New Studio build! Calgary AB.

Regarding your three-leaf question, I don't think it is going to be a big deal, since most of that leaf is just one huge hole! In any event, if you are concerned about it, you can compensate somewhat for three-leaf issues by increasing the air gaps and increasing the mass of the two leaves that you will be adding. - Stuart -

Death By Darwin wrote:

it looks to me that the only rays that will reflect back to the mix position would be from the very front edges of the windows only. I could rotate the control room, but that would leave only 10' or so to the back wall (I read on here somewhere that 13' was optimum and that 10' was particularly bad.) which problem is the greater evil?

Draw your listening area. Extend the splayed wall lines past the listening area. Draw a mirror image of the listening area using the extended splayed wall line as the mirror Draw lines from the monitors to the listening area Where ever the lines cross the extended slaped wall line, has to be absorption. The drawing you posted does not have the listening area, or the extended walls on it. Stuart answered the 3 leaf question beautifully. Andre

Ok, I drew the listening area and mirrored it as per Andre's suggestion. I didn't post the result as it was too small to really see the lines with the 700pixel limit, but the results showed that if I limit the listening area to the area in front of my console I get some early reflections off the first couple inches of the window as well as the wall between the window and soffit. I can certainly treat the wall, and I can make either a thick heavy curtain or some kind of sliding absorber that I can slide across the window when mixing. I think this is my best bet as turning the control room to have the window at the front would also mean I would have a large window at the back of the control room where absorption is also needed. Tell me if I am wrong however, if it is more important to have no early reflections than short backwall reflections... I can't change the windows at this point because I have already obtained a permit for the construction as is (Note I did ask if this was going to be a problem in an earlier post prior to applying for the permit and got no responses to the contrary). On a more exciting note, I have been making progress on the construction end of things and now have the Concrete done, framed most of the exterior walls of the addition and installed the roof trusses (with much difficulty and inclement weather) Hopefully I can get the entrance way framed and whole thing sheeted by next week! Here are some pics of my progress. Regards, -jER

Death By Darwin wrote:

I can certainly treat the wall, and I can make either a thick heavy curtain or some kind of sliding absorber that I can slide across the window when mixing.

Good idea.

I can't change the windows at this point because I have already obtained a permit for the construction as is (Note I did ask if this was going to be a problem in an earlier post prior to applying for the permit and got no responses to the contrary).

The only reference to design and construction permit I see is a post where you wrote that it was primarily exterior, what you had shown, and that the interior was not a concern to inspectors. Andre

It was in my first post, "The mixing desk would be at the end of the room with the window into the live room to the left of the desk. I was thinking of having a identical window to the outside on the other side of the room for symmetry and to allow light through to the live room. I will have some heavy curtains on both windows that I can pull across when mixing. Are there any significant reasons I shouldn't do this?" The drawing I posted was only the exterior, and that is the only part that concerns the permit, however having windows in the outer leaf that don't match up with windows in the inner leaf is kinda pointless. I guess I should have probably finished the sketch-up model to include the interior design at that point and maybe that would have been a little clearer. Anyway, I think it should work out alright. At the time I thought about making the window on the exterior side smaller or maybe remove them all together, however I figured having such a large pane of glass on one side only would ruin the symmetry as far as sound is concerned. This way at least the panes will effect both left and right equally. Would have saved me some money though, the quote I got for a 1/2" pane of laminated glass was $850 ea.

A good trick for checking your wall angles (in Sketchup, though I'm sure you could do this technique in other programs) Use the protractor tool. Draw an angle that has the vertex (elbow, if you will) at the forward-most edge of your splayed wall. Extend one ray to the speaker and the other to behind your listening position. This shows you the angle from speaker to wall to listening position. If you half that angle, it will give you a line that will be perpendicular to the splay angle needed to reflect behind the listening position. So just take that half and find 90 degrees from it and that is the minimum splay needed to reflect behind your listening position. I hope I did not write this too confusing. Here is a quick example of what I mean. With a soffit mount I would start an angle from my speaker's tweeter (arm A) to the forward-most edge of a splayed wall (vertex) to behind the listening position (arm B). Let's say that angle between Arm A & B is 30 degrees. If I were to take 15 degrees and add 90 to it, I'd get the minimum angle that the splay wall would need to be. So, from the front of the wall facing the tweeter, I'd need to extend the wall 105 degrees. Any less than 105 and I'd be moving the reflection toward the listening position. More than that and I'd be moving the reflection further back in the room. That example is for if you want your walls to reflect incoming sound behind your listening position. The other option is having them reflect to your listening position and place absorbing treatments at the reflection point. Just remember to do a trace for each speaker and each listening position that you want to be treated.

A good trick for checking your wall angles (in Sketchup, though I'm sure you could do this technique in other programs)

Unfortunately, it isn't that easy: it depends on the speaker dispersion angles too, as well as the tilt angle of the soffit panel, and the rest of the room, which is all 3D, not 2D. The only reliable way to do it is with ray tracing in 3D. - Stuart -

Of course it can be more complicated. Walls that are tilted immediately become more complex. I don't see how a soffit angle will affect the reflection point off of a side wall, though. Can you explain this part more clearly? My understanding was that if you are soffiting your speakers, then the speakers become the single point sources for sound. You wouldn't say "Put a mirror on your side wall and if you can see any part of your soffit, you need to treat that spot." You would just look for the speaker, and specifically the tweeter. Or I could be misunderstanding what you meant. As far as speaker dispersion, this is assuming dispersion in 360 degrees from the speaker. It just limits that down to the pie slice of that which is falling on the side wall. Assuming we were talking about light, if you lit up your side wall "mirror" with a huge 360 degree light from the speaker and then angled that mirror so that the entire reflection shone behind the mix position, then that is the goal right? One edge of that pie slice would be the first to cross over the mix position as you tilt your wall inward. So if you get that worst offender behind the mix position, the rest of the wall is safe. I'm not proposing how to find the reflection point within the wall itself. You would need to ray trace to find that spot on the wall that your reflection is going to fall at. I'm proposing a way to angle the wall so that no part of it is reflecting into the mix spot. It's not quite addressing the issue the same way, so ray tracing may very well be what is needed in a situation. Maybe I'm just complicating a simple issue, but I guess this little trick works for me.. or I could be wrong and only think it works for me. :( I'll double check in a bit. I don't really see how measuring an angle of bounce off of a wall is a bad way to go about solving reflection problems for the entire wall. Perhaps I was confusing about the technique described. If so I apologize.

Attached is a little Sketchup with a simple wall reflection from a soffited speaker to demonstrate the concept I'm talking about. I don't wish to derail the thread, so if this is getting too much, would an admin please remove the post or let me know and I will post it as its own thread. I wanted to find an angle for the bright green side wall that would provide a RFZ to the listening position. I extended the speaker and listening position down to the floor into a 2D space. I measured the angle from speaker to wall front edge to the outside of the listening position, all in 2D space. Half of that angle plus 90 gave me a minimum angle for me to turn my wall away from my speaker to reflect everything on that wall behind the listening position. To double check, I extended rays in 3D space from the speaker to the four corners of the wall and traced the bounce on those. If you look downward in Parallel Projection, without perspective, you can see these 3D bounces line right up with the 2D trace. So, with level floors or ceilings this method will work. For multiple bounces off of angled walls, such as a sloped ceiling to a sloped wall, I'm pretty sure that you're going to need to get into ray tracing at that point. But this should work fine for working out a wall angle to eliminate a first reflection point.

As far as speaker dispersion, this is assuming dispersion in 360 degrees from the speaker.

For a soffit mount???? :shock: The entire purpose of soffit mounting is to force the speaker to radiate into half-space, not full-space. Dispersion angle cannot possibly be 360° for a soffit mounted speaker. In any event, dispersion depends on both frequency and speaker design, and is practically always different in the vertical and horizontal planes.

I don't see how a soffit angle will affect the reflection point off of a side wall, though.

Simple: If a soffit happens to be angled too far towards the opposite-side wall, the reflection will be towards the mix position, which is what you are trying to avoid. And if it is angled too far towards the near-side wall, you get the same problem. (Depending on the speaker and frequency, of course.)

You wouldn't say "Put a mirror on your side wall and if you can see any part of your soffit, you need to treat that spot."

Why not? A soffit is an infinite baffle, so treating any point where you can see the soffit reflected is not unreasonable. It might be overkill to treat locations where you see the reflection of the extreme edges of the soffit, but treating the central area is great idea.

Attached is a little Sketchup with a simple wall reflection from a soffited speaker to demonstrate the concept I'm talking about.

Maybe I'm totally misunderstanding your model, but the speaker isn't eve soffited in there! It appears to be pointing straight down the room. I don't understand the room geometry, either: Assuming that the mix position is represented by the white circle, and the speaker is the circle on the non-angled front wall, then the room geometry makes no sense at all. The mix position is not centered in the room, the speaker is not placed at any usable location, and is not facing any useful direction. Sorry, but I just don't get it. - Stuart -

Soundman2020 wrote:

For a soffit mount???? :shock: The entire purpose of soffit mounting is to force the speaker to radiate into half-space, not full-space. Dispersion angle cannot possibly be 360° for a soffit mounted speaker.

Sorry -- misspoke, 180 degrees

Why not? A soffit is an infinite baffle, so treating any point where you can see the soffit reflected is not unreasonable. It might be overkill to treat locations where you see the reflection of the extreme edges of the soffit, but treating the central area is great idea.

This is just the first time I've heard that. Usually when advising treatment of first reflections, using the mirror technique to find the tweeter is what is mentioned by those giving advice.

Maybe I'm totally misunderstanding your model, but the speaker isn't eve soffited in there! It appears to be pointing straight down the room. I don't understand the room geometry, either: Assuming that the mix position is represented by the white circle, and the speaker is the circle on the non-angled front wall, then the room geometry makes no sense at all. The mix position is not centered in the room, the speaker is not placed at any usable location, and is not facing any useful direction. Sorry, but I just don't get it.

Sorry for the lack of clarity. The point source in the front wall you see all of the rays coming from is the "speaker". If you would like to solve for an entire area of a soffit, you can take multiple measures around whatever your soffit is, just as you could with the mirror technique or what have you. The circle in the middle of the room would be the area that you want to make reflection free. The sketchup is just demonstrating that you can take a source (speaker) a single wall, and a listening area, and find an angle that reflects 100% of what hits that wall from that point away from the listening position. If you want to find a good wall angle for multiple points, just use multiple speaker positions at the edges of your soffit and find the wall angle that works for them all. Symmetrical rooms, centered mix positions, producers couches, etc. aren't needed to show the way sound bounces from a point off of a wall. Sorry if this has confused more than it should. I can't think of an easier way to demonstrate the concept.

Symmetrical rooms, centered mix positions, producers couches, etc. aren't needed to show the way sound bounces from a point off of a wall.

I beg to differ! If you want to demonstrate how sound radiates from an angled soffit, then it might be an idea to actually show the angled soffit! And if you want to show how angling the soffit affects the RFZ around the mix position, then room symmetry, geometry, and the other wall are all kind of important too, yet not shown on your diagram... - Stuart -

Do you need a blueprint to measure an angle of a reflection? Being a studio designer doesn't change the way your physics work or the ways you can measure them. It's not important, if ray tracing works for you it certainly works for bouncing waves off of a wall. Go with that. :horse:

RScott - a speaker doesn't radiate 180 degrees - the high end drivers will have a directivity angle where the power rolls off as you move off axis. It's usually around 30 degrees. Check the curves on page 3. http://www.genelec.com/documents/datasheets/DS1034B.pdf

Do you need a blueprint to measure an angle of a reflection?

Ummm... actually, yes you do, if you are designing a studio. And as John mentioned, you also need to understand the characteristics of the speaker you are dealing with. - Stuart -

Does a carpenter need to know about his bookcase to measure 3 inches with a ruler? Mind you -- just to take a ruler and measure off 3 inches -- of anything. No. The ruler will measure those 3 inches no matter what the application (In this case, protractors measuring angles of bounce.) I see there are two arguments happening. Your argument is valid -- that a designer needs to know what those inches (or in this case angle measurements) are being used for and how they relate to his design. Obviously it is super critical that he measure the proper 3 inches on the proper board at the proper angle to build his bookcase. No argument there from me. You are 100% right that many, many aspects of design interconnect and that a designer needs to know how they impact each other. What angle the speakers disperse in, angles of walls and even bounces off of multiple walls, soffit and speaker mechanics, etc. etc. etc. 100% right. My argument is valid -- that you can use a protractor to quickly find the minimum angle needed to bounce something to someplace you want to bounce it. No argument there from you as far as I understand. The designer's job will be to decide what factors to consider at what value and use his tools to reach whatever goals he has. Suppose he decides through research that his tweeters don't radiate anything significant enough to consider past 45 degrees off their horizontal axis. He can measure the waves he considers important out to a wall that they will collide with. He may then quickly use a protractor to solve what angle that wall must be to get those important waves where he wants them (EG: not in the listening zone.) Or he could make sure that he bounces them into some rear broadband absorbers. Or to another wall that can bounce them far enough that they will not interfere with the sound image. Suppose he decides that his woofers and also a portion of his soffit are sending out waves at a given dispersion angle. He can find the walls they will come into contact with and use a protractor to quickly solve the minimum angle he needs to get all of those where he wants them to go. Suppose he wants to print my super cool protractor trick out, ball it up and make a 3 point shot off the wall and into the trash can.......... that's probably the best approach due to the simplicity. Unless your trashketball is as bad as mine and requires you to shoot, curse, and then walk all the way across the room to make Par 4. Death by Darwin .. I apologize for my confusion and mess in your thread. I will cease.

Question for you guys... Would it be better to build the interior leaf of the control room rectangular and then build a cloth covered frame to make the 6deg splay and fill it with rockwool like a wedge shaped superchunk for extra bass trapping? or maybe put slats across them and make hembolts style walls so that the directional high frequencies are still reflected behind the mix position while still adding extra bass trapping? just an idea... -jER

Would it be better to build the interior leaf of the control room rectangular and then build a cloth covered frame to make the 6deg splay and fill it with rockwool

Nope. That won't work, since cloth is acoustically transparent and has practically no mass. The ONLY purpose of cloth in a studio is to hide the ugly treatment behind it: it is purely aesthetic, and has no effect either on isolation or treatment. If you did that, it would be a bass trap, but it would do nothing at all to shape the RFZ that you need, and most certainly would be useless as a speaker soffit. Soffit panels have to be hard, massive, solid, rigid, and large. EG. very thick plywood, MDF, HDF, even concrete, etc. Rockwool and cloth is exactly the opposite of what you need for a soffit panel.

or maybe put slats across them and make hembolts style walls so that the directional high frequencies are still reflected behind the mix position while still adding extra bass trapping

That is commonly called a "slot wall" here, and it is a good idea.... but for the SIDE walls, not for the speaker soffit. The entire concept of a soffit is that it must act like an infinite baffle, which is basically just an extension of the front panel of your speaker itself, which is also called a "baffle", technically. It just makes your speaker drivers "think" that they are part of a really huge speaker box, and forces them to radiate sound into half space only. the infinite baffle prevents low frequency sound from "wrapping around" behind the speaker, where it gets reflected off the front wall, interferes with itself, and muddies up the sound. So the soffit panel has to be at least as hard, dense, solid, etc. as the front panel of your speaker, but it has to by MUCH bigger in all directions, and since it is much bigger, it also needs to be more rigid, held in place tightly, etc. - Stuart -

I am talking about the side walls of the control room (splayed 6deg as per forums recommendation) not the soffits themselves, the soffits will be angled more around 30deg and made of MDF. I was just thinking that since the 6deg splay on the side walls will not affect the low frequencies anyway I might as well make the inner leaf rectangular and make slot walls inside at 6 deg to make a RFZ in the higher frequencies. I am limited in space for bass trapping at the rear of the CR (I will have superchunks in the rear corners but no room for hangers etc.) and was thinking this could give me some extra bass trapping along the side walls. -jER

Update for those who are interested... I have been spending every spare minute outside of work building the addition for my control room and it is coming along; slower than I would have liked but steady at least. I am doing all the work myself and have been kind of learning as I go. I finished all the framing and sheeted the whole addition including the roof with 3/4" tounge and groove OSB (with acoustic caulk in the grooves during assembly). The structure is solid enough to withstand a tornado. Once 3/4"s of stucco is applied to the outside my outer leaf should have plenty of mass and a really good seal. After pulling up the shingles on the front half of the existing garage in order to install the blind valley trusses for the addition, and realizing the roofers didn't even bother to put felt under the shingles never mind drip edge, ice & water shield, vents etc, I have decided to re-roof the entire structure. This past weekend was spent shingling the front half of the garage and addition. I used a nice heavy laminated shingle and it looks pretty good. This was my first experience with roofing and I can honestly say I don't envy roofers. It might been easier had I not had the misfortune of stepping heavily on a 3" deck screw protruding from a 2x4 while cleaning up the yard in preparation; sunk it through my shoe and a good 1" into the ball of my foot (got a tetanus shot this time). Hopping 30 bundles of shingles up a ladder onto the roof on one foot was not fun, but I managed not to fall off at least. Planning to complete the back side of the garage this friday. Still need to finish the soffits and fascia, install the window and doors and some 2x6 cedar trim, then learn how to stucco, and I will be ready to start framing the interior leaves. Will post some picks as soon as I can borrow a camera... Regards, -jER

I'm interested! got any pictures? :D -janne

Sorry for the delay, I had borrowed a camera from a friend and took these pics, but he needed it and took it back before i could get the pics off it. Anyway here are a few somewhat outdated pics of my progress, after these were taken I have installed the exterior door, window frame, cedar trim, building paper, lath, etc. Spent the the past three days putting up the 2 base coats of stucco on the addition. Stucco is another one of those things on this project I have never done before, its proving to be a lot of hard labor, however not too difficult. Most of what I learned of concrete finishing earlier in the project was similarly applicable to stucco, particularly the sore back... needless to say it would not be my first choice of professions, although it still beats roofing. I had to tarp all the walls from the eves and crank the furnace in the garage to keep the stucco from freezing overnight. Once I am able to take down the tarps I will try to take some more pics. Regards, -jER

So, some new pics of my progress... Got the exterior addition almost complete, including some nice cedar trim and fascia and stucco is finally finished. The final coat of stucco didn't work quite as nicely as I would have liked, the colour doesn't quite match and I was unable to match the texture of the origional finish. I ended up doing the finish coat all by my self since my help bailed on me, it was 24 degrees that day and the stucco was drying faster than I could put it up. Didn't leave me much time to experiment, so I went with an easy flat finish. Doesn't look too terrible for my first attempt at stucco... Unfortunately last night I went and put a huge dent in my studio budget... (see first pic) stupid, stupid, stupid...