This quote is left in place to clarify the first response to the thread. Studio build starts a few messages down:
(Removed by OP pending clarification of measurements and ideas, and more suitable placement in the forums.)
Sorry about the confusion.
-Mark
Mix Room in Scottsdale, AZ - Construction Starting
Moderators: Aaronw, kendale, John Sayers
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Mark Jeangerard
- Posts: 19
- Joined: Fri Jun 21, 2013 1:19 pm
- Location: Scottsdale, AZ
Mix Room in Scottsdale, AZ - Construction Starting
Last edited by Mark Jeangerard on Wed Aug 14, 2013 4:30 am, edited 4 times in total.
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Mark Jeangerard
- Posts: 19
- Joined: Fri Jun 21, 2013 1:19 pm
- Location: Scottsdale, AZ
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Soundman2020
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Re: Mix Room in Scottsdale, AZ - (Removed)
OK, but if it is a studio design, then right here on the design forum is the best place to put it.Removed by OP pending clarification of measurements and ideas, and more suitable placement in the forums.
Looking forward to seeing more details!
- Stuart -
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Mark Jeangerard
- Posts: 19
- Joined: Fri Jun 21, 2013 1:19 pm
- Location: Scottsdale, AZ
Re: Mix Room in Scottsdale, AZ - (Removed)
OK...
Two and a half months ago I was going to start building corners slats, slat walls, pressure traps, and hanging 703 fixtures almost at random. Based on a few ideas I had about controlling a room and some stuff I had built before, stuff that had an effect on a recording room. I came here to check that I was going to build the things correctly and make sure my math was on and got hit in the head with a dose of reality. Cool. Except that I haven't cut a single piece of wood. I got Everest' and Gervais' books, and a favorites folder with 100 links in it that I pour through daily. I got REW and an Earthworks M30 and a head full of incomprehensible gobbledy-gook. At some point I have to start, no matter how effective my strategy might be, and today is that day.
Oddly enough, I'm right back where I started. Corners slats, slat walls, pressure traps, and hanging 703 fixtures. Hopefully, not so random this time. And probably no pressure traps.
So, no solid plans yet, but at the very least there are two things I can build. A corner trap and a wall section. These illustrations should help you understand why I think I can build two fixtures without a plan. I'm starting with the wall section.
This is the room in question. North wall is on the right, south door leads outside, east opening leads to the kitchen. (Very handy for coffee and peanut butter on spoon runs.) I tried really hard to justify building the room on the short orientation. The build would be much easier because of the slant in the roof and the fireplace would not interfere with the soffit. If it were my house and I could build airtight floor to ceiling that is what I would be doing. (Except that I would have bought a different house.) Alas, I am renting. So, for the most part, my build has to be freestanding. This build won't work because it is too hard for me to predict what all that open space would do to the sound.
North is up. None of the measurements are accurate, this is just a mock up so that, along with the previous sketch, I could visualize what it would take to build the room. I am working on a more accurate sketch up as I post this. The problems here are the fireplace, the slant roof, and the "back" of the room. The back of the room is also a pathway both into the mix position and outside for the family, so I can't build back too far or all the way across the space. But overall the space will be much more predictable for someone of my practical skill set in acoustics. (That last line makes me laugh... skill set... lol.) So, what can I start building today? The wall section (in green) that adds just a little more separation from the kitchen. It will be 3/4" MDF with 2" of depth avail....
OK. I just thought about that. Maybe I won't start building that as it is a fairly large space to work with. 3' x 7' x 15 1/2". I could use that for low end absorption.
The other thing I was considering building, which seems to be a no-brainer is this: Seeing that I have only 2 corners to work with, and that I have a lot of wackyness going on in my transition range, 2 of these makes sense to me. However, as you will see, the second one might not make a lot of sense. Or will it? That is one of my first questions which I will get to in the next post.
-Mark
Two and a half months ago I was going to start building corners slats, slat walls, pressure traps, and hanging 703 fixtures almost at random. Based on a few ideas I had about controlling a room and some stuff I had built before, stuff that had an effect on a recording room. I came here to check that I was going to build the things correctly and make sure my math was on and got hit in the head with a dose of reality. Cool. Except that I haven't cut a single piece of wood. I got Everest' and Gervais' books, and a favorites folder with 100 links in it that I pour through daily. I got REW and an Earthworks M30 and a head full of incomprehensible gobbledy-gook. At some point I have to start, no matter how effective my strategy might be, and today is that day.
Oddly enough, I'm right back where I started. Corners slats, slat walls, pressure traps, and hanging 703 fixtures. Hopefully, not so random this time. And probably no pressure traps.
So, no solid plans yet, but at the very least there are two things I can build. A corner trap and a wall section. These illustrations should help you understand why I think I can build two fixtures without a plan. I'm starting with the wall section.
This is the room in question. North wall is on the right, south door leads outside, east opening leads to the kitchen. (Very handy for coffee and peanut butter on spoon runs.) I tried really hard to justify building the room on the short orientation. The build would be much easier because of the slant in the roof and the fireplace would not interfere with the soffit. If it were my house and I could build airtight floor to ceiling that is what I would be doing. (Except that I would have bought a different house.) Alas, I am renting. So, for the most part, my build has to be freestanding. This build won't work because it is too hard for me to predict what all that open space would do to the sound.
North is up. None of the measurements are accurate, this is just a mock up so that, along with the previous sketch, I could visualize what it would take to build the room. I am working on a more accurate sketch up as I post this. The problems here are the fireplace, the slant roof, and the "back" of the room. The back of the room is also a pathway both into the mix position and outside for the family, so I can't build back too far or all the way across the space. But overall the space will be much more predictable for someone of my practical skill set in acoustics. (That last line makes me laugh... skill set... lol.) So, what can I start building today? The wall section (in green) that adds just a little more separation from the kitchen. It will be 3/4" MDF with 2" of depth avail....
OK. I just thought about that. Maybe I won't start building that as it is a fairly large space to work with. 3' x 7' x 15 1/2". I could use that for low end absorption.
The other thing I was considering building, which seems to be a no-brainer is this: Seeing that I have only 2 corners to work with, and that I have a lot of wackyness going on in my transition range, 2 of these makes sense to me. However, as you will see, the second one might not make a lot of sense. Or will it? That is one of my first questions which I will get to in the next post.
-Mark
-
Mark Jeangerard
- Posts: 19
- Joined: Fri Jun 21, 2013 1:19 pm
- Location: Scottsdale, AZ
Re: Mix Room in Scottsdale, AZ - Construction Starting
My primary concern here is stereo reproduction. I am going to build a center soffit and have surrounds on stands. Except for the center soffit, I will consider the 5.1 system last. A hobby, if you will. I think I will probably build some hanger mounts into the tops of the soffit walls in the event I want to hang some absorbers for 5.1. But that is all I am thinking about 5.1 for now.
The design will be RFZ with a Slayers style soffit, slot walls, absorptive ceiling and rear wall. Rear wall area in pink is 2'x8'. Slot walls in this sketch are 8' long but I will probably be making two 4' segments per side. (Unless someone has a good reason to stick with the 8' section.) I have some initial questions which I will ask at the end of this post. I will refer to this sketch for some of them. Room is 20' x 13' 4" x 7' 2" average height. Floor is linoleum on concrete. Walls and ceiling are 1/2" gypsum on 2x4 stud. (For the most part.)
I have done a lot of measurements and moving of things. The room, as it stands - empty but for a couch and coffee table - has a certain amount of "glue" when playing musical program with the speakers on an 80° axis, 50" from listening position, focused 7" behind the listening position. I know that soffits and slats will change the room considerably, but my assumption is to go with what is naturally working before treatment.
This REW set shows the room empty but for the couch and coffee table in both the short and long configuration. The first three measurements, "Doors Off" are the sweeps from the "wide" configuration of the room. They are there only for comparison as I am almost certainly committed to loading the room on the long axis. (The only reason I was considering wide was because I thought it might give a more symmetrical stereo image because of the fireplace and ceiling. I no longer believe that is the case.)
01WideVsLong.mdat https://docs.google.com/file/d/0BxqCOj6 ... sp=sharing
Measurements 4-6 are from 38% in the room with the sub in a somewhat logical placement. (I have many sub tests and these demonstrations are fine for comparison.)
Measurements 7-9 are 5" towards the front from 38% in the room with the sub in a somewhat logical placement.
Measurements 10-12 are 11" towards the front from 38% in the room with the sub in a somewhat logical placement. (With the speakers on a 60° axis this position was actually pretty good. But the soffit is then too narrow. I measured on the 80° axis just to be thorough.)
I am fairly confident that 38% is going to be the way to go and this is where I am starting. The mathematical predictions of modal and spectral behavior and decay of the room seem to jive pretty well with the measurements. Doing the math on the room with the windows, walls, floor, and ceiling is fairly straight forward. But my main concerns are this:
1. Will the room be sufficiently different with soffits and slat walls that I should calculate from there instead?
2. I have no idea how to calculate how the slat walls behave absorbtively above the midrange.
The other questions at the top of my list:
3. Given that the drawing above is simply a very quick sketch to illustrate what I am thinking. The OSB areas are going to be independent fixtures. Standing objects. (Except the right speaker soffit. I couldn't figure out how to make it one solid piece quickly. Please ignore the horizontal line splitting it.) If I build sections like that, should I still build a second corner slat for the NW corner? Will it still work the same way between approx. 110hz - 500hz? Or would some other construct better serve the space available?
4. The pink area is roughly 8'w x 2'd x 7'h. Would 1"MDF with 4" 703 mounted at differing depths be better? Or a frame with acoustic hangers?
5. The green area. Really, any low end control in that position could only be achieved with a pressure device. Is there going to be sufficient benefit to attempting to build one in that exact position?
Anyway, I'm working on drawings right now. Soffit is primary. After which, I need to start calculating treatment for decay times.
6. Am I correct in thinking that most of that will come from ceiling and back wall? (I'm right back to now knowing how the slat walls act.)
Thanks for any input. (Please.)
-Mark
[Edit] I forgot to specify exactly how measurements 7-9 and 10-12 were different from 4-6
The design will be RFZ with a Slayers style soffit, slot walls, absorptive ceiling and rear wall. Rear wall area in pink is 2'x8'. Slot walls in this sketch are 8' long but I will probably be making two 4' segments per side. (Unless someone has a good reason to stick with the 8' section.) I have some initial questions which I will ask at the end of this post. I will refer to this sketch for some of them. Room is 20' x 13' 4" x 7' 2" average height. Floor is linoleum on concrete. Walls and ceiling are 1/2" gypsum on 2x4 stud. (For the most part.)
I have done a lot of measurements and moving of things. The room, as it stands - empty but for a couch and coffee table - has a certain amount of "glue" when playing musical program with the speakers on an 80° axis, 50" from listening position, focused 7" behind the listening position. I know that soffits and slats will change the room considerably, but my assumption is to go with what is naturally working before treatment.
This REW set shows the room empty but for the couch and coffee table in both the short and long configuration. The first three measurements, "Doors Off" are the sweeps from the "wide" configuration of the room. They are there only for comparison as I am almost certainly committed to loading the room on the long axis. (The only reason I was considering wide was because I thought it might give a more symmetrical stereo image because of the fireplace and ceiling. I no longer believe that is the case.)
01WideVsLong.mdat https://docs.google.com/file/d/0BxqCOj6 ... sp=sharing
Measurements 4-6 are from 38% in the room with the sub in a somewhat logical placement. (I have many sub tests and these demonstrations are fine for comparison.)
Measurements 7-9 are 5" towards the front from 38% in the room with the sub in a somewhat logical placement.
Measurements 10-12 are 11" towards the front from 38% in the room with the sub in a somewhat logical placement. (With the speakers on a 60° axis this position was actually pretty good. But the soffit is then too narrow. I measured on the 80° axis just to be thorough.)
I am fairly confident that 38% is going to be the way to go and this is where I am starting. The mathematical predictions of modal and spectral behavior and decay of the room seem to jive pretty well with the measurements. Doing the math on the room with the windows, walls, floor, and ceiling is fairly straight forward. But my main concerns are this:
1. Will the room be sufficiently different with soffits and slat walls that I should calculate from there instead?
2. I have no idea how to calculate how the slat walls behave absorbtively above the midrange.
The other questions at the top of my list:
3. Given that the drawing above is simply a very quick sketch to illustrate what I am thinking. The OSB areas are going to be independent fixtures. Standing objects. (Except the right speaker soffit. I couldn't figure out how to make it one solid piece quickly. Please ignore the horizontal line splitting it.) If I build sections like that, should I still build a second corner slat for the NW corner? Will it still work the same way between approx. 110hz - 500hz? Or would some other construct better serve the space available?
4. The pink area is roughly 8'w x 2'd x 7'h. Would 1"MDF with 4" 703 mounted at differing depths be better? Or a frame with acoustic hangers?
5. The green area. Really, any low end control in that position could only be achieved with a pressure device. Is there going to be sufficient benefit to attempting to build one in that exact position?
Anyway, I'm working on drawings right now. Soffit is primary. After which, I need to start calculating treatment for decay times.
6. Am I correct in thinking that most of that will come from ceiling and back wall? (I'm right back to now knowing how the slat walls act.)
Thanks for any input. (Please.)
-Mark
[Edit] I forgot to specify exactly how measurements 7-9 and 10-12 were different from 4-6
-
Mark Jeangerard
- Posts: 19
- Joined: Fri Jun 21, 2013 1:19 pm
- Location: Scottsdale, AZ
Re: Mix Room in Scottsdale, AZ - Construction Starting
OK... corner slat will be my second project. 
It has become obvious to me, after speaking with the Sylomer guy, that I should build my speaker boxes first. I need to weigh them so we can come up with the correct Sylomer product and puck size to most effectively decouple the speakers from the stands they will be on. Then I can measure the system under load and finish designing the soffit.
A Sylomer dealer in America who answers his phone and even offered to help me with the calculations can be found here:
http://www.pyroteknc.com/contact-us.asp
Sylomer specs, so you can do your own math can be found here:
http://www.proctorgroup.com/products/ac ... ns/sylomer
I am going to use Sorbothane and Sylomer in my soffit. The reason for both is that I got so wound up in trying to find Sylomer in America that I am going to use it even though I have recently found Sorbothane and have it and the math necessary at my immediate disposal. It's just an OCD kind of hang up thing. I really want to have some Sylomer in my hands to play with and look at and all those other human fetish things that keep me from going with a Sorbothane solution that can be implemented now rather than the time it will take to consult, order, receive, and measure the Sylomer. But... I'm kinda silly like that.
I am assuming, that the point to the box is to further increase transmission loss in the speaker cabinet. My design thus far is based on that principal. The box is 1/8" per side bigger than the speaker. I am using Sorbothane to mount the speakers in the box to keep them from slipping, keep them from rattling, and to seal the air channel between the box and speaker. (I imagine some kind of port action in that 1/8" of space. I have no idea if that is a concern.) The Sorbothane is not being used for isolation because, while I know how to calculate the weight of the speaker on top of Sorbothane material, and *maybe* how to calculate suspending the speaker in the material on 4 sides, I have no way of measuring the deflection accurately enough to make sure I have the correct amount of pressure on the material. And I'm not sure I can get that accurate with wood to load all the points correctly. So I am simply stuffing the Sorb and speakers into tight fitting boxes and then mounting that assembly on Sylomer (or Sorbothane) pucks.
In America Sorbothane can be purchased here. I don't know if that is a good price. But it is the best I found in my search:
http://www.mcmaster.com/#sorbothane/=o5g1t9 They are in California and get the goods to me in 24 hours, regular shipping.
You can find the specs on Sorbothane and even a handy calculator at their web site:
http://www.sorbothane.com/
My plan so far is to build the boxes. Weigh them. Then call the Sylomer guy and order that. Then I can measure the Sylomer under load and finish drawing the soffits.
I love, love, love SketchUp. Never knew about it until I read about it here. I made about 50 mistakes on the boxes from logical errors to bad fraction summing. SketchUp saved me on almost every account because I could see that there was a 1/4" of gap here, or 1/16" overlap there. Very handy tool, that. It also makes it really easy to measure and cut compound angles and size cuts from stock material. It does a lot of math for you.
I remember the last time I had a soffit the entire front of the room was shaped like a horn (sorta). The acoustician spoke with the contractor for a couple of hours over lunch. When the contractor started - a good friend of mine and well respected builder in the community - he was very confident. I actually saw him throw a tape measure, curse incessantly for about a week, and even just give up and take an afternoon off over the compound angles. He was doing all the calculations on the saw and sketches on the backs of 2x4s. Something like SketchUp would have made him a very happy man at that time.
Nice tool, that SketchUp. Now, if only there are no flaws in my thinking....
It has become obvious to me, after speaking with the Sylomer guy, that I should build my speaker boxes first. I need to weigh them so we can come up with the correct Sylomer product and puck size to most effectively decouple the speakers from the stands they will be on. Then I can measure the system under load and finish designing the soffit.
A Sylomer dealer in America who answers his phone and even offered to help me with the calculations can be found here:
http://www.pyroteknc.com/contact-us.asp
Sylomer specs, so you can do your own math can be found here:
http://www.proctorgroup.com/products/ac ... ns/sylomer
I am going to use Sorbothane and Sylomer in my soffit. The reason for both is that I got so wound up in trying to find Sylomer in America that I am going to use it even though I have recently found Sorbothane and have it and the math necessary at my immediate disposal. It's just an OCD kind of hang up thing. I really want to have some Sylomer in my hands to play with and look at and all those other human fetish things that keep me from going with a Sorbothane solution that can be implemented now rather than the time it will take to consult, order, receive, and measure the Sylomer. But... I'm kinda silly like that.
I am assuming, that the point to the box is to further increase transmission loss in the speaker cabinet. My design thus far is based on that principal. The box is 1/8" per side bigger than the speaker. I am using Sorbothane to mount the speakers in the box to keep them from slipping, keep them from rattling, and to seal the air channel between the box and speaker. (I imagine some kind of port action in that 1/8" of space. I have no idea if that is a concern.) The Sorbothane is not being used for isolation because, while I know how to calculate the weight of the speaker on top of Sorbothane material, and *maybe* how to calculate suspending the speaker in the material on 4 sides, I have no way of measuring the deflection accurately enough to make sure I have the correct amount of pressure on the material. And I'm not sure I can get that accurate with wood to load all the points correctly. So I am simply stuffing the Sorb and speakers into tight fitting boxes and then mounting that assembly on Sylomer (or Sorbothane) pucks.
In America Sorbothane can be purchased here. I don't know if that is a good price. But it is the best I found in my search:
http://www.mcmaster.com/#sorbothane/=o5g1t9 They are in California and get the goods to me in 24 hours, regular shipping.
You can find the specs on Sorbothane and even a handy calculator at their web site:
http://www.sorbothane.com/
My plan so far is to build the boxes. Weigh them. Then call the Sylomer guy and order that. Then I can measure the Sylomer under load and finish drawing the soffits.
I love, love, love SketchUp. Never knew about it until I read about it here. I made about 50 mistakes on the boxes from logical errors to bad fraction summing. SketchUp saved me on almost every account because I could see that there was a 1/4" of gap here, or 1/16" overlap there. Very handy tool, that. It also makes it really easy to measure and cut compound angles and size cuts from stock material. It does a lot of math for you.
I remember the last time I had a soffit the entire front of the room was shaped like a horn (sorta). The acoustician spoke with the contractor for a couple of hours over lunch. When the contractor started - a good friend of mine and well respected builder in the community - he was very confident. I actually saw him throw a tape measure, curse incessantly for about a week, and even just give up and take an afternoon off over the compound angles. He was doing all the calculations on the saw and sketches on the backs of 2x4s. Something like SketchUp would have made him a very happy man at that time.
Nice tool, that SketchUp. Now, if only there are no flaws in my thinking....
-
Mark Jeangerard
- Posts: 19
- Joined: Fri Jun 21, 2013 1:19 pm
- Location: Scottsdale, AZ
Re: Mix Room in Scottsdale, AZ - Construction Starting
Lessons for today:
1. Never let your exuberance over a laser guided chop saw cloud your better judgement. Seeing that I would eventually be lowering the ceiling, I decided to make a bob stand. Oh, it works. It works perfectly. It will allow me to get meaningful measurements right through the end of construction. But looking at it in action I realized that I have some 30 mic stands in a closet and that material would have been better used to build a nice stand for my laser guided chop saw. Derp.
2. Cutting wood without a laser is not so easy as marking a piece of wood with a pencil then running the saw down the pencil line.
I started breaking down my plywood stock yesterday. I need to be within 1/32 in pretty much everything I do on this project. Well.... My first speaker box is going to be over an 1/8 here, under 3/32 there. So many things to learn. So many ways to mess up a cut: where you put the measuring tape, where you mark with the pencil, how you mark with the pencil, how you line up the jig to the pencil marks, how you ride the jig with the saw, how you ride the saw with your hand, where you keep your eyes compared to the cut... At least the boxes are going inside the soffit and they will be square where it is important so I don't feel the need to break down another sheet of plywood. The third speaker box is dead on. But it was a process to get there.
3. Always expect windo... no... Never count on windows to not completely lose track of your audio drivers right when you need them most.
4. If you have a project slated for completion on July 15th of a certain year, don't book a family vacation for August 26th the same year. It is almost certain that you will have just STARTED the project when it is time to leave for vacation.
I'll be back in a couple weeks. I will have the boxes assembled and some pretty pictures of them and a nice corner slat wall. Plus, at least two soffit designs to ponder.
-Mark
1. Never let your exuberance over a laser guided chop saw cloud your better judgement. Seeing that I would eventually be lowering the ceiling, I decided to make a bob stand. Oh, it works. It works perfectly. It will allow me to get meaningful measurements right through the end of construction. But looking at it in action I realized that I have some 30 mic stands in a closet and that material would have been better used to build a nice stand for my laser guided chop saw. Derp.
2. Cutting wood without a laser is not so easy as marking a piece of wood with a pencil then running the saw down the pencil line.
I started breaking down my plywood stock yesterday. I need to be within 1/32 in pretty much everything I do on this project. Well.... My first speaker box is going to be over an 1/8 here, under 3/32 there. So many things to learn. So many ways to mess up a cut: where you put the measuring tape, where you mark with the pencil, how you mark with the pencil, how you line up the jig to the pencil marks, how you ride the jig with the saw, how you ride the saw with your hand, where you keep your eyes compared to the cut... At least the boxes are going inside the soffit and they will be square where it is important so I don't feel the need to break down another sheet of plywood. The third speaker box is dead on. But it was a process to get there.
3. Always expect windo... no... Never count on windows to not completely lose track of your audio drivers right when you need them most.
4. If you have a project slated for completion on July 15th of a certain year, don't book a family vacation for August 26th the same year. It is almost certain that you will have just STARTED the project when it is time to leave for vacation.
I'll be back in a couple weeks. I will have the boxes assembled and some pretty pictures of them and a nice corner slat wall. Plus, at least two soffit designs to ponder.
-Mark
-
Soundman2020
- Site Admin
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- Joined: Thu Aug 21, 2008 10:17 am
- Location: Santiago, Chile
- Contact:
Re: Mix Room in Scottsdale, AZ - Construction Starting
Valuable lessons indeed! All of them.Lessons for today:
I would just change one of those a bit, to say that if you schedule to start building your studio on July 15, do not plan a family vacation for the next several YEARS!!!
- Stuart -
-
Mark Jeangerard
- Posts: 19
- Joined: Fri Jun 21, 2013 1:19 pm
- Location: Scottsdale, AZ
Re: Mix Room in Scottsdale, AZ - Construction Starting
Several Years Indeed... 
It's a whirlwind out there. After coming home from our trip I had a choice 2 days to not unpack and recharge before going back out for a couple of weeks on the road with work. I brought my laptop with REW and Sketchup files on it but ended up getting nothing done. I've been home for a few weeks now but keep getting work in town nearly every day.
On the one free day between camping and mini-tour I got my speaker boxes built. (I just realized that I did not take a picture of my stack of speaker box cuts. Anyway... it looked like the Sketchup only much more realistic.) Here I am cutting my Sorbothane strips and double checking my 1.5" clearance from the front of the baffle.
So far, so good. Note the change of venue. Went outside for gluing and screwing.
Sorbothane is really interesting to work with. It is a liquid solid and will spend the remainder of it's life attempting to flow back into it's original shape. It is necessary to place it without stretching it. If there is any misaligning torque on it, it will immediately start working it's way back to where it started. Putting these together with just one person is not very easy. One must be quick and precise and willing to start over at any time. Note the "oldschool" countersinking technique. See you tomorrow. I left myself 3" for cooling and knob twizzling. I have some idea of how I am going to run the duct but it may change by the time I have the soffits done based on what I may stumble upon at the hardware store. I am taking all these pictures with my phone. Even if I were using my girlfriends camera I wouldn't know how to make them look the same.
It's a whirlwind out there. After coming home from our trip I had a choice 2 days to not unpack and recharge before going back out for a couple of weeks on the road with work. I brought my laptop with REW and Sketchup files on it but ended up getting nothing done. I've been home for a few weeks now but keep getting work in town nearly every day.
On the one free day between camping and mini-tour I got my speaker boxes built. (I just realized that I did not take a picture of my stack of speaker box cuts. Anyway... it looked like the Sketchup only much more realistic.) Here I am cutting my Sorbothane strips and double checking my 1.5" clearance from the front of the baffle.
So far, so good. Note the change of venue. Went outside for gluing and screwing.
Sorbothane is really interesting to work with. It is a liquid solid and will spend the remainder of it's life attempting to flow back into it's original shape. It is necessary to place it without stretching it. If there is any misaligning torque on it, it will immediately start working it's way back to where it started. Putting these together with just one person is not very easy. One must be quick and precise and willing to start over at any time. Note the "oldschool" countersinking technique. See you tomorrow. I left myself 3" for cooling and knob twizzling. I have some idea of how I am going to run the duct but it may change by the time I have the soffits done based on what I may stumble upon at the hardware store. I am taking all these pictures with my phone. Even if I were using my girlfriends camera I wouldn't know how to make them look the same.
-
Mark Jeangerard
- Posts: 19
- Joined: Fri Jun 21, 2013 1:19 pm
- Location: Scottsdale, AZ
Re: Mix Room in Scottsdale, AZ - Construction Starting
Just like room measurements, I took these measurements several times each. The scale was perfectly level and calibrated. The left speaker assembly is 0.3 pounds heavier than the right. I have written the weight of each assembly on top of each box with a sharpy.
These are as close to in place as I can get them prior to building the soffits. The woofers will actually be scooted in about 3" towards the center along the baffle plane. I have measure response in both positions and they are close enough for comparison during the build.
The woofer on the left is sitting on 4 pieces of accurately calculated and cut 1/2" Sorbothane. It's really cool stuff and immediately there was less vibration from things like the lamp, or a level laying on the floor.
This was an exercise in commitment. Those speakers are very much in those boxes. If a speaker fails it will have to be cut out of the assembly to be repaired. While in New Mexico I spoke with a woodworker that I and some friends use for cases, racks, and cabinets. He said he could have built boxes that would have fit exactly without the need for any type of gasket. I also spent some time thinking about the weight discrepancy. The speakers themselves are off by 0.1lbs. But perhaps particle board or OSB would have been better. If I have done it wrong, I will be bummed, but have no qualms about starting over.
That being said, it is really interesting what the boxes alone do to the sound. Much less sound is coming out of the sides and top, and what is coming out of the front seems to be of greater intensity. Or, I'm completely misinterpreting what I am seeing in the room measurements. Which is; that there seem to be deeper nulls along the length axial corresponding to shallower ones in the height and width. Also, the impulse seems to be smoother along the decay. That makes me think that the sound is taking longer routes?
Multi Measurement REW File https://docs.google.com/file/d/0BxqCOj6 ... sp=sharing
Measurements 001 are from the empty room. 002 are after the speaker boxes are built. I will keep adding to this file as I go.
This was an exercise in commitment. Those speakers are very much in those boxes. If a speaker fails it will have to be cut out of the assembly to be repaired. While in New Mexico I spoke with a woodworker that I and some friends use for cases, racks, and cabinets. He said he could have built boxes that would have fit exactly without the need for any type of gasket. I also spent some time thinking about the weight discrepancy. The speakers themselves are off by 0.1lbs. But perhaps particle board or OSB would have been better. If I have done it wrong, I will be bummed, but have no qualms about starting over.
That being said, it is really interesting what the boxes alone do to the sound. Much less sound is coming out of the sides and top, and what is coming out of the front seems to be of greater intensity. Or, I'm completely misinterpreting what I am seeing in the room measurements. Which is; that there seem to be deeper nulls along the length axial corresponding to shallower ones in the height and width. Also, the impulse seems to be smoother along the decay. That makes me think that the sound is taking longer routes?
Multi Measurement REW File https://docs.google.com/file/d/0BxqCOj6 ... sp=sharing
Measurements 001 are from the empty room. 002 are after the speaker boxes are built. I will keep adding to this file as I go.
Last edited by Mark Jeangerard on Tue Oct 22, 2013 9:32 am, edited 1 time in total.
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Mark Jeangerard
- Posts: 19
- Joined: Fri Jun 21, 2013 1:19 pm
- Location: Scottsdale, AZ
Re: Mix Room in Scottsdale, AZ - Construction Starting
So... the room is a bit cockeyed. The ceiling slants from left to right. I have decided to load it on the long axis. In an attempt to use as much space as possible for trapping I have built one corner trap for one of the two possible corners. The second one may or may not be built the same way. (I will address that question in the next post.) In the meantime I have one device in place and ready for measurement. I have some errands to run today, and work tomorrow, but hope to measure tonight. We'll see.
Sketchup of Corner Trap https://docs.google.com/file/d/0BxqCOj6 ... sp=sharing
There is the plan. I haven't finished it. Trim needs to be measured and the angles need to be figured, but for now, it won't have trim any time soon. I just want to see how it works.
Here is my sacrifice table for breaking down large stock. It works pretty good. It's 2' high and levelish. 1' 8" would have been better. I may lower it. I learned about the 1/4" Masonite straight cut jig and sacrifice table on youtube. What a blessing that website is. 3/4" particle board is being cut for the corner trap cabinet. I am working on this every time I get 2 spare hours. I need two because the new puppy dog dictates that every piece of scrap, every screw, and every tool be stowed at the end of each working session. This thing is the size of a freakin' bulldozer blade and as far as I can tell, weighs nearly as much. Furring strips.... And caulk I brought this inside with a hand truck. I actually got pinned under it for a couple of minutes. It is not light. lol. I made it an inch short on purpose because I was worried about being able to tilt it into the upright position. I'm glad I did. Even at the highest point in the room it barely cleared. I have installed 4 nylon pads on the bottom so that it slides easily. I hope they don't rattle. It will get heavier. I did my calculations based on the wood size as it is from the store. 3.5", 5.5", and 7.25". Here are a bunch of slats cut to length, marked, and pilot holed. I also cut myself some sweet spacers for the assembly of the wall. 1/4", 1/2", and 1/8". I am using screws and wire to hold the 703 in. Yes, I did get the angle wrong on the pieces that fit closest to the corner. I was not wearing my mask when I opened the box. Just opening the box launched particles into the air and some got in my lungs. It was uncomfortable for a few days. Now I know, and so do you.
Just enough staples to keep the burlap stretched. I figure the slat screws will do the majority of that work.
At last! A step in the process that is actually easy.
And there you have it. (Less trim.)
Yes, I did use the cheap wood. It is about the same mass as the wood I am going to use for the rest of the room, and 1/3 the price. I figured I'd mess up a lot so I bought the cheap stuff. In the end I was amazed to find out that every cut I made corresponded to the Sketchup plans. I measured the actual build for every cut every step of the way. When I measured for the last slat on top it was exactly the same in actuality as it was in the Sketchup drawings and the spacers fit perfectly. The 1/32nd or so of the burlap that I did not factor in is clearly not factored in! So there's a lesson for me - rulers work. Don't be afraid of the ruler.
I will measure the room with REW later and put the results right here. Curious to see the effect one corner slot wall might have on the room.
[later] Grrrr.... I backed into the right speaker while moving stuff. I now have no faith in the measurements for direct comparison. I have two options, sally forth and use the measurements to judge general trends to help make decisions during construction, or reset the room from scratch (I already pulled up all my tape floor markings) then remove the corner trap and start the process over from that point.
[later still] I reset the room.
The wood I intend to use (and I can't remember which one it is now because I have a bunch of woods in my head and know it by sight but will buy a plank later to get an estimate of it's mass and then tell you what it is...) is quite good looking. No knots and a rich color. As a matter of fact I saw some of the exact wood I intend to buy at a trendy downtown clothing store Saturday night as I was doing sound for a street party type thing. The store is two stories tall and completely done in this scrap wood theme. There is at least 5 times the wood I need for my room in the front window display alone. At least they are conscientious enough to sell "Vegan Leather Jackets". (I kid you not.)
First day off this week I am going to go down there and ask if the display is coming out any time soon.
Sketchup of Corner Trap https://docs.google.com/file/d/0BxqCOj6 ... sp=sharing
There is the plan. I haven't finished it. Trim needs to be measured and the angles need to be figured, but for now, it won't have trim any time soon. I just want to see how it works.
Here is my sacrifice table for breaking down large stock. It works pretty good. It's 2' high and levelish. 1' 8" would have been better. I may lower it. I learned about the 1/4" Masonite straight cut jig and sacrifice table on youtube. What a blessing that website is. 3/4" particle board is being cut for the corner trap cabinet. I am working on this every time I get 2 spare hours. I need two because the new puppy dog dictates that every piece of scrap, every screw, and every tool be stowed at the end of each working session. This thing is the size of a freakin' bulldozer blade and as far as I can tell, weighs nearly as much. Furring strips.... And caulk I brought this inside with a hand truck. I actually got pinned under it for a couple of minutes. It is not light. lol. I made it an inch short on purpose because I was worried about being able to tilt it into the upright position. I'm glad I did. Even at the highest point in the room it barely cleared. I have installed 4 nylon pads on the bottom so that it slides easily. I hope they don't rattle. It will get heavier. I did my calculations based on the wood size as it is from the store. 3.5", 5.5", and 7.25". Here are a bunch of slats cut to length, marked, and pilot holed. I also cut myself some sweet spacers for the assembly of the wall. 1/4", 1/2", and 1/8". I am using screws and wire to hold the 703 in. Yes, I did get the angle wrong on the pieces that fit closest to the corner. I was not wearing my mask when I opened the box. Just opening the box launched particles into the air and some got in my lungs. It was uncomfortable for a few days. Now I know, and so do you.
Just enough staples to keep the burlap stretched. I figure the slat screws will do the majority of that work.
At last! A step in the process that is actually easy.
And there you have it. (Less trim.)
Yes, I did use the cheap wood. It is about the same mass as the wood I am going to use for the rest of the room, and 1/3 the price. I figured I'd mess up a lot so I bought the cheap stuff. In the end I was amazed to find out that every cut I made corresponded to the Sketchup plans. I measured the actual build for every cut every step of the way. When I measured for the last slat on top it was exactly the same in actuality as it was in the Sketchup drawings and the spacers fit perfectly. The 1/32nd or so of the burlap that I did not factor in is clearly not factored in! So there's a lesson for me - rulers work. Don't be afraid of the ruler. I will measure the room with REW later and put the results right here. Curious to see the effect one corner slot wall might have on the room.
[later] Grrrr.... I backed into the right speaker while moving stuff. I now have no faith in the measurements for direct comparison. I have two options, sally forth and use the measurements to judge general trends to help make decisions during construction, or reset the room from scratch (I already pulled up all my tape floor markings) then remove the corner trap and start the process over from that point.
[later still] I reset the room.
The wood I intend to use (and I can't remember which one it is now because I have a bunch of woods in my head and know it by sight but will buy a plank later to get an estimate of it's mass and then tell you what it is...) is quite good looking. No knots and a rich color. As a matter of fact I saw some of the exact wood I intend to buy at a trendy downtown clothing store Saturday night as I was doing sound for a street party type thing. The store is two stories tall and completely done in this scrap wood theme. There is at least 5 times the wood I need for my room in the front window display alone. At least they are conscientious enough to sell "Vegan Leather Jackets". (I kid you not.)
First day off this week I am going to go down there and ask if the display is coming out any time soon.
Last edited by Mark Jeangerard on Wed Oct 30, 2013 1:18 pm, edited 1 time in total.
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Mark Jeangerard
- Posts: 19
- Joined: Fri Jun 21, 2013 1:19 pm
- Location: Scottsdale, AZ
Re: Mix Room in Scottsdale, AZ - Construction Starting
Whilst resetting the room I found two problems with my earlier set that I adjusted for.
1. For whatever reason, I documented the acoustical center of the speaker 1/4" higher than it actually is. The height of the speaker cabinet has not changed but I have lowered the bob and the measurement mic by that amount.
2. In my previous set I had the speaker cabinets centered on the focal axis. I have now set with the acoustical center on the focal axis. This brings the speakers in 1 1/4" each.
I reset the room. It is very close to final positions now. Removed the corner trap, measured, replaced the corner trap, measured.
Every step of the way I run into one thing or another that confounds me completely. Today it is the timing of the measurements. When looking at the impulse response, ETC, and Step I am seeing a lot go on before the 0 time mark. I have read and reread the REW online manual and the help inside the preferences window and I am just. Not. Getting. It.
From the REW online manual, "When an impulse response is measured by means of a logarithmically swept sine wave, the room's linear response is conveniently separated from its non-linear response. The portion of the response before the initial peak at time=0 is actually due to the system's distortion - looking closely, there are scaled down, horizontally compressed copies of the main impulse response there - each of those copies is due to a distortion harmonic, first the 2nd harmonic, then the third, then the fourth etc. as time gets more negative. The initial peak and its subsequent decay after time=0 is the system's response without the distortion."
Why is the system distortion before the 0 time point? Is it important for me to understand why, or can I go on and worry only about what the rest of the display tells me?
This graphic is from a measurement set I took of the slat corner trap. I set the mic a couple of feet from the corner when the trap was not there. Once the trap was in place, the mic was now 1 foot from the trap. I expected some timing differences. (The reason I put the mic there was because when walking around, I thought I heard some significant difference that I wanted to measure.) What I am not understanding is why the impulse appears to be before the initial peak time. I am trying to look at the impulse response as if it were a sound recording of a wave. Because that's what it looks like to me and I stare at those things all day long, every day. My brain is wired to interpret that shape into that thing. Am I looking at this completely, or partially, incorrectly? The gold plots are from the bare corner. The blue plots are with the corner slat wall. Top plot is L&R speakers. Middle is Left only. Bottom is right only. The subwoofer that is used in all three measurements is placed under the left speaker. The system distortion mentioned above is in those plots at a very low level. That is not what I am concerning myself with right now, but rather the larger, more obvious, impulses. Hmm... is it that I have unhooked the foldback channel to facilitate stereo operation?
(OK. This is really weird. I am looking at the measurements from the mix position and there is no timing discrepancy in the impulses, whatsoever. I did the measurements in one session in this order, trapless corner LR L R, trapless mix LR L R, trapped mix LR L R, and finally trapped corner LR L R. Perhaps I have applied some offset by accident? Or are they doing what they should and I just don't understand how to read the graphs?)
Anyway, here is the file with some interesting results. The speakers are firing off the North wall, which is the front of the room. The south west corner is the only corner on the south end of the room. It is bare in the first three measurements, and has the above referenced slat wall in place in the second three. The mic is 27 5/8" from the south wall, 26" from the west wall, facing south. I think I put the mic too close to the trap. But I'm not moving that thing again any time soon.
Corner Trap.mdat https://drive.google.com/file/d/0BxqCOj ... sp=sharing
My design estimate said it would be effective from about 70hz to 700hz. This is the stereo plot showing effect down to 53hz. Gold is no trap. Blue is with. The tangentials seem to get some strong influence from the device. At least in the (0,0,x). Unfortunately, the vertical modes and reflections are going to be a problem in this room for ever. That big dip at 155hz would appear to be the second vertical harmonic. It would make sense where the mic is, I think, although I can't see how the trap would affect the vertical. That whole 155-180hz region is supported by a lot of oblique modes. Is that it? less support? The waterfall would appears to show no small amount of influence on the decay. That is part of what I thought I was hearing standing close to the trap. 20hz to 20khz 20hz to 16khz
Another thing I thought I was hearing (feeling?) was a significant boost in the 20-30hz range. Especially in the north/west corner behind the left speaker and woofer. These plots clearly show a boost in that range after the trap was placed. ? It's easier to see looking at the REW files.
Tests from the mix position. 003aRoomStart.mdat https://drive.google.com/file/d/0BxqCOj ... sp=sharing (Measurements designated "001" are from the incorrect placement. Although, without the soffit, I'm not sure it matters so much.)
Back to the mix position and we see some dramatic changes. These next plots are from 50hz to 700hz. Mic is at mix position in a bare room with the exception of a couch and coffee table in their final positions and the corner trap out and in. L&R speakers. It's hard to see in this graphic, but those nulls at 283hz and 297hz are 10db deeper with the trap in place. The null at 602hz is a full 25db deeper. It ends up that the slat corner almost perfectly opposes the fireplace which also cuts across a corner. It has, in effect, changed the dimension of the room.Left speaker only. The comb filtering is pretty rowdy. It fires into the east wall, then reflects into the SW corner where the trap is. Right speaker only. It fires into the west wall then exits the room through the kitchen opening. Once again, I need some time to think about how this is all happening.
The waterfall still looks marginally better in the predicted range. So... hum.... the device and how closely it matches prediction are impressive. The overall effect of the new surface in the room is also impressive. While I'm so impressionable I'm tempted to think that over thinking each piece as it goes in will lead to me chasing my tail. At this point however, I am just starting to think about how acoustics work, and how these devices work. It is easy to get sidetracked with these lines of thought. Even so, I think I have more ammo for my final design by getting sidetracked in this manner.
OK. So. Soffit design and trapping questions...
1. For whatever reason, I documented the acoustical center of the speaker 1/4" higher than it actually is. The height of the speaker cabinet has not changed but I have lowered the bob and the measurement mic by that amount.
2. In my previous set I had the speaker cabinets centered on the focal axis. I have now set with the acoustical center on the focal axis. This brings the speakers in 1 1/4" each.
I reset the room. It is very close to final positions now. Removed the corner trap, measured, replaced the corner trap, measured.
Every step of the way I run into one thing or another that confounds me completely. Today it is the timing of the measurements. When looking at the impulse response, ETC, and Step I am seeing a lot go on before the 0 time mark. I have read and reread the REW online manual and the help inside the preferences window and I am just. Not. Getting. It.
From the REW online manual, "When an impulse response is measured by means of a logarithmically swept sine wave, the room's linear response is conveniently separated from its non-linear response. The portion of the response before the initial peak at time=0 is actually due to the system's distortion - looking closely, there are scaled down, horizontally compressed copies of the main impulse response there - each of those copies is due to a distortion harmonic, first the 2nd harmonic, then the third, then the fourth etc. as time gets more negative. The initial peak and its subsequent decay after time=0 is the system's response without the distortion."
Why is the system distortion before the 0 time point? Is it important for me to understand why, or can I go on and worry only about what the rest of the display tells me?
This graphic is from a measurement set I took of the slat corner trap. I set the mic a couple of feet from the corner when the trap was not there. Once the trap was in place, the mic was now 1 foot from the trap. I expected some timing differences. (The reason I put the mic there was because when walking around, I thought I heard some significant difference that I wanted to measure.) What I am not understanding is why the impulse appears to be before the initial peak time. I am trying to look at the impulse response as if it were a sound recording of a wave. Because that's what it looks like to me and I stare at those things all day long, every day. My brain is wired to interpret that shape into that thing. Am I looking at this completely, or partially, incorrectly? The gold plots are from the bare corner. The blue plots are with the corner slat wall. Top plot is L&R speakers. Middle is Left only. Bottom is right only. The subwoofer that is used in all three measurements is placed under the left speaker. The system distortion mentioned above is in those plots at a very low level. That is not what I am concerning myself with right now, but rather the larger, more obvious, impulses. Hmm... is it that I have unhooked the foldback channel to facilitate stereo operation?
(OK. This is really weird. I am looking at the measurements from the mix position and there is no timing discrepancy in the impulses, whatsoever. I did the measurements in one session in this order, trapless corner LR L R, trapless mix LR L R, trapped mix LR L R, and finally trapped corner LR L R. Perhaps I have applied some offset by accident? Or are they doing what they should and I just don't understand how to read the graphs?)
Anyway, here is the file with some interesting results. The speakers are firing off the North wall, which is the front of the room. The south west corner is the only corner on the south end of the room. It is bare in the first three measurements, and has the above referenced slat wall in place in the second three. The mic is 27 5/8" from the south wall, 26" from the west wall, facing south. I think I put the mic too close to the trap. But I'm not moving that thing again any time soon.
Corner Trap.mdat https://drive.google.com/file/d/0BxqCOj ... sp=sharing
My design estimate said it would be effective from about 70hz to 700hz. This is the stereo plot showing effect down to 53hz. Gold is no trap. Blue is with. The tangentials seem to get some strong influence from the device. At least in the (0,0,x). Unfortunately, the vertical modes and reflections are going to be a problem in this room for ever. That big dip at 155hz would appear to be the second vertical harmonic. It would make sense where the mic is, I think, although I can't see how the trap would affect the vertical. That whole 155-180hz region is supported by a lot of oblique modes. Is that it? less support? The waterfall would appears to show no small amount of influence on the decay. That is part of what I thought I was hearing standing close to the trap. 20hz to 20khz 20hz to 16khz
Another thing I thought I was hearing (feeling?) was a significant boost in the 20-30hz range. Especially in the north/west corner behind the left speaker and woofer. These plots clearly show a boost in that range after the trap was placed. ? It's easier to see looking at the REW files.
Tests from the mix position. 003aRoomStart.mdat https://drive.google.com/file/d/0BxqCOj ... sp=sharing (Measurements designated "001" are from the incorrect placement. Although, without the soffit, I'm not sure it matters so much.)
Back to the mix position and we see some dramatic changes. These next plots are from 50hz to 700hz. Mic is at mix position in a bare room with the exception of a couch and coffee table in their final positions and the corner trap out and in. L&R speakers. It's hard to see in this graphic, but those nulls at 283hz and 297hz are 10db deeper with the trap in place. The null at 602hz is a full 25db deeper. It ends up that the slat corner almost perfectly opposes the fireplace which also cuts across a corner. It has, in effect, changed the dimension of the room.Left speaker only. The comb filtering is pretty rowdy. It fires into the east wall, then reflects into the SW corner where the trap is. Right speaker only. It fires into the west wall then exits the room through the kitchen opening. Once again, I need some time to think about how this is all happening.
The waterfall still looks marginally better in the predicted range. So... hum.... the device and how closely it matches prediction are impressive. The overall effect of the new surface in the room is also impressive. While I'm so impressionable I'm tempted to think that over thinking each piece as it goes in will lead to me chasing my tail. At this point however, I am just starting to think about how acoustics work, and how these devices work. It is easy to get sidetracked with these lines of thought. Even so, I think I have more ammo for my final design by getting sidetracked in this manner.
OK. So. Soffit design and trapping questions...
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Soundman2020
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Re: Mix Room in Scottsdale, AZ - Construction Starting
... Then you need to fix that! Two possible solutions: 1) Make it flat (wastes valuable volume), 2) Make it gabled (might need extra treatment at the peak). I would go for gabled.So... the room is a bit cockeyed. The ceiling slants from left to right.
You don't really need to build a half-box for a corner trap: you can just stack triangles of 703 in the corner, and put a fabric-covered frame in front to hide them.Sketchup of Corner Trap
Ummmm..... you put slats across your bass trap?At last! A step in the process that is actually easy.
That makes it into a slot wall, not a bass trap. I'm not sure I understand the reason behind that.Me too! What frequencies did you tune it to?Curious to see the effect one corner slot wall might have on the room.
Every step of the way I run into one thing or another that confounds me completely.
Welcome to the wonderful world of acoustics! "Intuitive" and "logical" are words that you don't hear too often in relation to acoustics.... Hmmmm.... strange. What REW shows before time 0 is the harmonics response, but that sure doesn't look like harmonics response in your graphs! What you should see on the left side is sort of squished up copies of the fundamental response (starts at time 0). However, you seem to be showing the actual linear impulse response curves themselves as %FS, when what you really need to see is the logarithmic version, dB FS. IF you hover the mouse over the window, you should get a pop-up box at the top left side, where you can select the correct display. It should look something like this:When looking at the impulse response, ETC, and Step I am seeing a lot go on before the 0 time mark.
If you then zoom out form that view, you'll see the harmonic copies over on the left, something like this: If yours don't look like that, then you there's something wrong with the way you are measuring.
It isn't actually "before" time 0 in reality! That's just the place it appears, due the way the math works out...Why is the system distortion before the 0 time point?
That's also not correct: You should only ever make measurements of the room with the mic in the listening position! If you move the mic, then you CANNOT compare that reading against any others you took in a different place in the room. With the mic in a different place, you are not measuring what you need to measure: what it sounds like at the mix position! So unless you plan to mix at the location where you had the mic, then you can safely discard that data, and re-measure your "before" and "after" responses for that angled slot thingy.I set the mic a couple of feet from the corner when the trap was not there.
Another no-no! You should always measure at least 3 feet from walls and things, to ensure that you are measuring the overall response. (Unless you want to measure the response of one specific part of a device, in order to see if it is working, or compare it to another part of the device.).Once the trap was in place, the mic was now 1 foot from the trap.
Because you change the distance! Originally, before you put your corner thingy in place, the mic was several feet from the wall, so all responses took several milliseconds longer to arrive than after you put it in place! So the "after" responses appear to be several ms earlier than the "before" responses, simply because, in effect, you moved the reflecting surface closer to the mic.What I am not understanding is why the impulse appears to be before the initial peak time. I am trying to look at the impulse response as if it were a sound recording of a wave.
Right!My brain is wired to interpret that shape into that thing. Am I looking at this completely, or partially, incorrectly?
Ahhhh! Now maybe that's why the recommendation is to always to all your measurements form the mix position!!!!I am looking at the measurements from the mix position and there is no timing discrepancy in the impulses, whatsoever.
Yup! You moved the mic... or the device... Both create time offsets in the response, which is what is confusing you, and also invalidating all of your readings.Perhaps I have applied some offset by accident?
Or are they doing what they should and I just don't understand how to read the graphs?)
The mic must ALWAYS be exactly where the middle of your head will be while you are mixing, pointing forwards (towards the speakers), and angled upwards at around 45°, give or take. That's the ONLY place it should ever be for taking room measurements. The only exception is if you are trying to measure the response of a device, but you'd need a proper acoustic measurement lab to do that, not a home studio .....I think I put the mic too close to the trap. But I'm not moving that thing again any time soon.
What speakers are you using? There aren't many that give any reasonable resemblance of flat response down that low. And REW cannot give you accurate readings down that low either.Another thing I thought I was hearing (feeling?) was a significant boost in the 20-30hz range.
I'm not seeing that! In fact, if anything there seems to be a slight drop at around 68 Hz, and a hole bunch of stuff going on between 100 and 200 Hz. But I don't even know what I'm looking at, and since you didn't measure at the mix position, none of it is useful anyway!These plots clearly show a boost in that range after the trap was placed. ?
What I do see is that the room needs major treatment!
(But you knew that already....)Those are probably more correct, so that's what I'll look at now.Tests from the mix position....
There is no bass trapping at all in the room yet, so I wouldn0t be too concerned about what is happening in the low end. I would rather be looking at the frequencies that you tuned your slot wall too, to see if it is having any effect. What frequencies did you tune it to?It's hard to see in this graphic, but those nulls at 283hz and 297hz are 10db deeper with the trap in place.
What was the prediction????? I didn't see where you predicted the response of your slot wall thingy! Plus, in a room that has no bass trapping yet, it won't be easy to see any mid-range results....So... hum.... the device and how closely it matches prediction are impressive.
I think you are just attacking thins on the wrong order!I'm tempted to think that over thinking each piece as it goes in will lead to me chasing my tail. At this point however, I am just starting to think about how acoustics work, and how these devices work. It is easy to get sidetracked with these lines of thought. Even so, I think I have more ammo for my final design by getting sidetracked in this manner.
First, get an accurate base-line measurement of the room with nothing in it. I think that might be your "002" measurements, but I'm not certain.
Next, install your soffits and get your speakers properly tweaked, and take another reading. That's your second baseline. Call it your "soffit baseline".
Now install basic bass trapping: superhchunks or hangers in the corners, deep absorption on the rear wall. Now measure again, to see how that worked out, and take another reading. Hopefully you should have the modal response under control now, so you can get better, more useful readings of the mid range, to see what you need to do there.
Now install your first reflection point treatment on the side walls, and take another reading.
Then your cloud, and take another reading.
Then, and ONLY then can you determine if you need slot walls, diffusers, resonators, or something else to deal with the remaining problems.
By starting out with slot walls, you have no way of knowing if you have tuned them right, and now way of measuring their response. You can ONLY do that in a room that is already properly treated for the typical basic problems.
So I'd suggest revising your Gantt Chart, and re-scheduling things in the right order!
- Stuart -
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dufo
- Posts: 81
- Joined: Thu Sep 16, 2004 4:42 pm
- Location: Australia
Re: Mix Room in Scottsdale, AZ - Construction Starting
Stuart,
Just curious why you say ALWAYS have the mic pointing up at 45 between the two speakers. This is contrary to what many other sources state. IN my case with a mic from cross spectrum labs calibrated, I use the 90 degree file pointing up in the middle of the mix position. Id be interested if you see problems doing it that way. I of course COULD do it your way and use the 45 degree cal file, but most dseem to think, IF you have the cal. file, that pointing straight up at the ceiling is best for room measurements. Thoughts?
I don't want to de rail the thread, but Im sure this is info the OP will find relevant when he gets to it.
Just curious why you say ALWAYS have the mic pointing up at 45 between the two speakers. This is contrary to what many other sources state. IN my case with a mic from cross spectrum labs calibrated, I use the 90 degree file pointing up in the middle of the mix position. Id be interested if you see problems doing it that way. I of course COULD do it your way and use the 45 degree cal file, but most dseem to think, IF you have the cal. file, that pointing straight up at the ceiling is best for room measurements. Thoughts?
I don't want to de rail the thread, but Im sure this is info the OP will find relevant when he gets to it.
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Soundman2020
- Site Admin
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Re: Mix Room in Scottsdale, AZ - Construction Starting
It's more of a general compromise that works for most situations. Some people tell you to point the mic directly at each speaker as you test it, but that makes no sense since you'd have to move the mic tip by several inches when switching from L to R, thus making it impossible to compare measurements, and leaving you with a big question mark as to where you point it when measuring both at once, and what to do if you also have a sub! So the logical thing is to just point it straight forwards, directly between the speakers for all tests. However, that has the drawback of perhaps having the results skewed for high frequencies, due to the directional characteristics (polar patterns) of the majority of studio monitors. Other people tell you to point the mic straight up at the ceiling, to avoid these HF artifacts, but that has the drawback of possibly being affected by first order mid-frequency reflections from the ceiling. If your ceiling is very dead (plenty of absorption, no reflections), then I'd have to agree that pointing straight up is the best option. But not all studios have such perfectly dead ceilings, and almost certainly don't when you do the first "baseline" test in the room, against which you will later compare all others. Others say to point it straight down at the floor, but the floor is practically always hard and reflective, and generally is in the shadow of the console/desk/chair, so that just doesn't make sense to me. It only makes sense if the room is empty and you have a thick pile carpet on the floor... So a 45° upwards angle is about the best compromise in avoiding all of these issues as much as possible, or at least minimizing them. To be honest, there isn't a huge difference in which way you point an omni mic anyway, so it's not a huge deal, in my book. To me, the most important and absolutely vital factor is to have the mic always in the exact same position for every single reading, regardless of which way it is pointing. The entire idea of taking readings after installing each round of treatment is to be able to compare the "before" with the "after", to see what the treatment accomplished, and to do that the mic MUST be in the identical location each time. If not, then you cannot validly compare readings. So if you had it pointing up the first time, then that's the way you should always have it. If pointing down, or straight ahead, or 45° up, or whatever for the very first reading, then all subsequent readings MUST be done the exact same way. As long as the mic position is consistent, you will get valid comparable results that really show you what each piece of treatment is doing. Of course, you might well want to take other readings around the room to look at other aspects, but for the actual treatment testing, the most critical factor is to duplicate the mic position perfectly every single time.
- Stuart -
- Stuart -