Would it be more beneficial to move my speaker to the left and right more, or move them closer to me in order to avoid reflections from the top shelf of my desk. Take a look at my pics I posted earlier and let me know what you think.You have the mic in the correct location, yes, and your speakers are aiming at the correct point, about 16" behind your head, yes, but the triangle does NOT need to be equilateral.... As long as the distance from left ear to left speaker is the same as the distance from right speaker to right ear, that's the only "triangle" you need. I can explain in more detail, if you want... But you have the mic and aim point correct, so that's good! - Stuart -When placing my monitors I made an equilateral triangle using a point that is 16” behind my ears/head. When I ran the REW test I placed the mic where my head/ears would be. Is this ok?
Need help with vocal booth/ room dimensions
Originally posted at johnlsayers.com, topic 21547.
Your speakers should be right up against the front wall of the room, on either side of the door. I wrote a long reply about speaker positioning for another forum member earlier today, where I covered most of the points that will be affecting you. Here's a link: viewtopic.php?f=2&t=19458&start=13 That should clarify several key issues about setting up your speakers and mix position. - Stuart -Would it be more beneficial to move my speaker to the left and right more, or move them closer to me in order to avoid reflections from the top shelf of my desk. Take a look at my pics I posted earlier and let me know what you think.
Interesting...I may have to sacrifice a bit as I do not want to have a trip hazard with the speaker wires being in the path between the door to the booth and my desk. I will think about this and may run a test with the speakers against the wall just to see what the difference in response is. In the meantime, when you have a chance, could you please give me some feedback on the last baseline REW test results I posted? I Want to make sure I did the test right and see what my next step forward should be. I want to fill the superchunks with insulation next and rerun the test, and then get some input from you guys as to how many panels I should use to tighten up the room from there. FYI, the LR--Baseline test did give a clipping error, not sure if that is normal or not, the single L and single R tests ran fine without clipping... Thanks!Your speakers should be right up against the front wall of the room, on either side of the door. I wrote a long reply about speaker positioning for another forum member earlier today, where I covered most of the points that will be affecting you. Here's a link: http://www.johnlsayers.com/phpBB2/viewt ... 8&start=13 That should clarify several key issues about setting up your speakers and mix position. - Stuart -Would it be more beneficial to move my speaker to the left and right more, or move them closer to me in order to avoid reflections from the top shelf of my desk. Take a look at my pics I posted earlier and let me know what you think.
Then run the wires in a different direction, and along the walls! You must be feeding power to your desk from somewhere, so run your speaker cables alongside that power cable over to the wall, then run them along the walls to the speakers.Interesting...I may have to sacrifice a bit as I do not want to have a trip hazard with the speaker wires being in the path between the door to the booth and my desk.
Yes, your data is valid, and you did the tests correctly. :thu:I Want to make sure I did the test right
The next step is to get your speakers and mix position set up in the correct locations. Here's an example of one of the issues: That's your low-end frequency response, below 500 Hz. You can see some very large dips in the response, at around 46 Hz and 65 Hz. I'm not sure how far your speakers are from the front wall, but I'm estimating that it is about 6 feet, so very likely the 46 Hz valley those is the first SBIR dip caused by that long distance. If the distance is a bit less, then it's the 65 Hz dip. It is impossible (or rather, extremely difficult) to fix those with room treatment. They are purely geometric issues, related to the incorrect location of the speakers. If you leave the speakers in their current location, there's nothing you can do about that. So, assuming you want good frequency response, the first thing you should do is to set up the geometry correctly, with the speakers and mix position in the proper locations. Then after that is correct, you should start with large bass traps in as many corners of the room as you can, absorption across the entire rear wall, and absorption in the first reflection points. Each time you make a change to the room, do another REW test to check that the device is working properly, and to see what needs to be done next.and see what my next step forward should be.
First, geometry. Then treatment. As you can see above, there are some issues that cannot be fixed with treatment, and must be addressed with geometry.I want to fill the superchunks with insulation next and rerun the test,
That's might be an issue with the mic pre-amp: if so, try turning down the gain a bit on the pre-amp. But first, check your gain structure: Are you certain that the level in the room was 86 dBC when you measured with your hand-held sound level meter (NOT with REW, but with your hand-held meter)? Did you have your meter set to "C" and "Slow"? - Stuart -FYI, the LR--Baseline test did give a clipping error, not sure if that is normal or not, the single L and single R tests ran fine without clipping...
Then run the wires in a different direction, and along the walls! You must be feeding power to your desk from somewhere, so run your speaker cables alongside that power cable over to the wall, then run them along the walls to the speakers. I will have to buy much longer speaker wires in order to do this, was trying to avoid having to do that, but after seeing the graph and response I think I'll run to the store and try it out! A couple questions first: 1) I believe the user manual for the Yamaha HS8 are reccomends the monitors be placed 4-5 ft away from the front wall. I believe they are rear ported and have a switch to compensate some if the monitors are being placed closer to the front wall. Should I ignore the manufacturer recommendation and move them close to the front wall anyways? If I do this, should I use the switch in the back to account for this? 2) Does it matter if one cable is say 50ft long and the other monitor cable is only 10ft long? Will this cause any delays, damage the stereo image, loss of quality or any other negative effects?Interesting...I may have to sacrifice a bit as I do not want to have a trip hazard with the speaker wires being in the path between the door to the booth and my desk.Yes, your data is valid, and you did the tests correctly. :thu: :yahoo:I Want to make sure I did the test rightThe next step is to get your speakers and mix position set up in the correct locations. Here's an example of one of the issues: That's your low-end frequency response, below 500 Hz. You can see some very large dips in the response, at around 46 Hz and 65 Hz. I'm not sure how far your speakers are from the front wall, but I'm estimating that it is about 6 feet, so very likely the 46 Hz valley those is the first SBIR dip caused by that long distance. If the distance is a bit less, then it's the 65 Hz dip. I will let you know the distance when I get back to the studio, however, I have the monitor height at 47" from center of tweeter to the floor. I couldnt find any information on where the acoustical axis is, and the manual suggested having the tweeter lined up with your ear. Is this ok or is there a known acoustical axis point for yamaha hs8 that I should use instad, or should I use the midpoint between the woofer and tweeter as the acoustical axis? It is impossible (or rather, extremely difficult) to fix those with room treatment. They are purely geometric issues, related to the incorrect location of the speakers. If you leave the speakers in their current location, there's nothing you can do about that. So, assuming you want good frequency response, the first thing you should do is to set up the geometry correctly, with the speakers and mix position in the proper locations. Then after that is correct, you should start with large bass traps in as many corners of the room as you can, absorption across the entire rear wall, and absorption in the first reflection points. Each time you make a change to the room, do another REW test to check that the device is working properly, and to see what needs to be done next. I will try moving the speakers and rerunning the test, but just a theoretical question, if I know where the dip is in the low frequency, could i use some room acoustic software to correct that? Is there a way to have the software add it back in? Not that I want to spend any more money on more software, but just curious! Also, could a workaround be to use headphones to check the low end also? I know the end goal is to have the room sound as good as possible, especially for playback purposes, but just thinking of workarounds.and see what my next step forward should be.First, geometry. Then treatment. As you can see above, there are some issues that cannot be fixed with treatment, and must be addressed with geometry. I plan filling all 4 corners with roxul safe n sound asap.I want to fill the superchunks with insulation next and rerun the test,That's might be an issue with the mic pre-amp: if so, try turning down the gain a bit on the pre-amp. But first, check your gain structure: Are you certain that the level in the room was 86 dBC when you measured with your hand-held sound level meter (NOT with REW, but with your hand-held meter)? Did you have your meter set to "C" and "Slow"? I had my meter set to "C", "Slow", but I had a level of 80db. Is "86" a typo, or should I run the next test at 86 db? Thanks for the help and quick response! Im anxious to get up and running and am hoping I can at least get the baseline and monitor position established asap so that I can get back to making music this weekend and then work on tweaking/improving the sound in the room from there - Stuart -FYI, the LR--Baseline test did give a clipping error, not sure if that is normal or not, the single L and single R tests ran fine without clipping...
The HS8 is an active speaker: built-in amplifiers. So there's no problems with having long cables to get to the speakers. There won't be any losses in quality due to the extra length. Assuming you are using balanced cables, of course! You could make them 300 feet long, and still not have any issues.I will have to buy much longer speaker wires in order to do this, was trying to avoid having to do that, but after seeing the graph and response I think I'll run to the store and try it out!
Keeping them away from the front wall is fine, .... IF you have a room that is large enough! But 4-5 feet is not enough. Here's a chart that shows the problematic distances in red, the not-so-good distances in blue, and the best distances in green: The chart is published by Neumann, but it applies to all speakers, made by all manufacturers. It's a physical problem that affects everything the same, not specific to any manufacturer. As you can see, the worst distance is about 4 to 5 feet! That's in the middle of the red range, as it produces SBIR dips in the range of 65 Hz to 45 Hz... :) To get to a sort-of OK position, it needs to be at least 7 feet form the front wall, which is not possible in a small room, and it only gets to be "good" beyond about 10 feet. On the other hand, if you put it right up against the front wall (less than 16 inches), then that's "good" too. So I'm not sure why the manual for your speaker says 4-5 feet: that doesn't make much sense, and you can see the exact problem in your own results. Set then up against the front wall, with just a 4" gap where you can insert a 4" panel of good absorption, such as OC-703 between the speaker and the wall.1) I believe the user manual for the Yamaha HS8 are reccomends the monitors be placed 4-5 ft away from the front wall. I believe they are rear ported and have a switch to compensate some if the monitors are being placed closer to the front wall. Should I ignore the manufacturer recommendation and move them close to the front wall anyways? If I do this, should I use the switch in the back to account for this?
Rear-porting is not a problem. You can place your speaker close to the wall if you need to. In fact, the manual says this as well: "In situations where it is not possible to position the speakers a sufficient distance from walls or corners, the ROOM CONTROL switch can be used compensate for excessive bass. As you move the speaker closer to walls or corners, a higher compensation setting may be required to achieve natural sounding response ...". So there's no problem with that: it won't damage your speaker if you put it close to the front wall, with the rear corner of the speaker just 4" away from the wall.they are rear ported and have a switch to compensate some if the monitors are being placed closer to the front wall.
No problem at all. The propagation of electric signals in copper wire is very nearly as fast as the speed of light, around 300 million meters per second, so unless one cable is a few million meters longer than the other, there won't be any difference at all in arrival of the signals. You would get a much, MUCH larger difference just by moving one speaker one millimeter closer than the other. So, no: there won't be any difference at all. The two channels will sound exactly the same, no loss of quality, no delays, no phase shift, no imaging issues, nothing. however, I have the monitor height at 47" from center of tweeter to the floor. I couldnt find any information on where the acoustical axis is, and the manual suggested having the tweeter lined up with your ear. Is this ok or is there a known acoustical axis point for yamaha hs8 that I should use instad, or should I use the midpoint between the woofer and tweeter as the acoustical axis? The acoustic axis is going to be on the imaginary line that joins the center of the woofer to the center of the tweeter, and much closer to the tweeter, which is a bit below where you estimated. So you could probably raise your speaker a bit. In fact, for most speakers and rooms, you can go a bit higher than 47", and that can be beneficial... as long as you don't go too high! Maybe an inch, or maximum 2 inches. The reason why that is good is because it reduces reflections from the surface of your desk or console. The reason why you can't go too high, is because you would put your head too far off-axis from the speaker.2) Does it matter if one cable is say 50ft long and the other monitor cable is only 10ft long? Will this cause any delays, damage the stereo image, loss of quality or any other negative effects?
Nope! Unfortunately not. The frequency is so low that any treatment would have to be huge. If you follow the theory that a porous absorber is effective at frequencies where the thickness of the absorber is 7% of the wavelength, and your frequency is 46 Hz, then your wavelength is over 24 feet! 295 inches, in fact. 7% of that is 21 inches. so you would need an absorber 21" thick on the front wall :shock: Even then, it would not be very effective, since porous absorbers just don't do very well at such low frequencies...if I know where the dip is in the low frequency, could i use some room acoustic software to correct that?
Nope! That doesn't work either, because this is a phase cancellation problem: the wave going towards the wall bounces back, and cancels itself out. So if you try to EQ that, and boost the frequency that is missing, all you do is get a BIGGER cancellation! You make the dip even deeper. But since you can't actually destroy energy, all the extra power that you are pumping in with your EQ boost has to go somewhere, and normally it just ends up causing instability around that frequency, so you end up with a very long ringing tone at an adjacent frequency (something like "feedback"). That's what I meant when I said it was "impossible or extremely hard" to treat such a problem. The frequency is just too low, and it is a phase cancellation problem, so it cannot be equalized. Sorry! :)Is there a way to have the software add it back in?
That's a good start, but there are 12 corners in a room, not just 4.... :) 8)I plan filling all 4 corners with roxul safe n sound asap.
You set the INDIVIDUAL speakers to 80 dBC for each one, but then when both are playing back the same sound together, the total will be 86 dB. Because twice the power is the same as an increase of 6 dB, and with both speakers on, the total is twice the power. That assumes that your speakers are playing in phase, of course, and that it is the exact same sound going out through both (in other words "coherent sound"). If the sound is not coherent, then the increase in level will be less: probably around 3 dB. So this is a good test to make sure your speakers and sound system is performing fine: test each speaker by itself at 80 dB with the other one turned off, then put them both on and you should see 86 dB. If you don't get 86 dB, then there's something wrong...I had my meter set to "C", "Slow", but I had a level of 80db. Is "86" a typo, or should I run the next test at 86 db?
Finding the best location for your speakers and mix position can take a long time! I'm just giving you the basics here: the starting point. Set them up against the front wall with 4" of absorption behind them, set up your chair at about 1/3 of the distance from the front wall to the back (anywhere in the range 30% to 40% is a good starting point), aim the speakers at a spot about 16" behind your head, then do multiple REW tests with the mic and speakers in slightly different positions to see if there's a better location. Move one thing at a time, in small increments, then keep the best location for that "thing". Then move another thing in small increments, to optimize that one. Then something else. Then go back to the first thing. For example, first try moving the mic forward and backward in steps of a couple of inches, to see if there's a good improvement overall. Then try moving the speakers further apart or closer together (also in small steps of a couple of inches). Then try moving the speakers up or down a little (in very small steps: half an inch or so). Then when you have all three of those done, go back to the mic position, because there might be an even better place now... etc. Optimizing this can take a long time... and then when you have your treatment in, you can do it all over again, since the best location will probably now be somewhere else! :) As the saying goes, Rome wasn't built in a day.... and your speaker / mix position layout can't be done in a day either! :) - Stuart - It's a slow process.Im anxious to get up and running and am hoping I can at least get the baseline and monitor position established asap
The HS8 is an active speaker: built-in amplifiers. So there's no problems with having long cables to get to the speakers. There won't be any losses in quality due to the extra length. Assuming you are using balanced cables, of course! You could make them 300 feet long, and still not have any issues. Thanks for the reassurance, I will buy some longer cables and try testing with the speakers closer to the wall as you suggest!I will have to buy much longer speaker wires in order to do this, was trying to avoid having to do that, but after seeing the graph and response I think I'll run to the store and try it out!Keeping them away from the front wall is fine, .... IF you have a room that is large enough! But 4-5 feet is not enough. Here's a chart that shows the problematic distances in red, the not-so-good distances in blue, and the best distances in green: The chart is published by Neumann, but it applies to all speakers, made by all manufacturers. It's a physical problem that affects everything the same, not specific to any manufacturer. As you can see, the worst distance is about 4 to 5 feet! That's in the middle of the red range, as it produces SBIR dips in the range of 65 Hz to 45 Hz... :) To get to a sort-of OK position, it needs to be at least 7 feet form the front wall, which is not possible in a small room, and it only gets to be "good" beyond about 10 feet. On the other hand, if you put it right up against the front wall (less than 16 inches), then that's "good" too. So I'm not sure why the manual for your speaker says 4-5 feet: that doesn't make much sense, and you can see the exact problem in your own results. Set then up against the front wall, with just a 4" gap where you can insert a 4" panel of good absorption, such as OC-703 between the speaker and the wall. Thanks for the explanation. I will try this out! Does it matter what angle I have the speakers pointing back towards me? OR should I test multiple positions between the superchunk and door? (making sure the distance from me to each speaker is equal of course)1) I believe the user manual for the Yamaha HS8 are reccomends the monitors be placed 4-5 ft away from the front wall. I believe they are rear ported and have a switch to compensate some if the monitors are being placed closer to the front wall. Should I ignore the manufacturer recommendation and move them close to the front wall anyways? If I do this, should I use the switch in the back to account for this?Rear-porting is not a problem. You can place your speaker close to the wall if you need to. In fact, the manual says this as well: "In situations where it is not possible to position the speakers a sufficient distance from walls or corners, the ROOM CONTROL switch can be used compensate for excessive bass. As you move the speaker closer to walls or corners, a higher compensation setting may be required to achieve natural sounding response ...". So there's no problem with that: it won't damage your speaker if you put it close to the front wall, with the rear corner of the speaker just 4" away from the wall.they are rear ported and have a switch to compensate some if the monitors are being placed closer to the front wall.No problem at all. The propagation of electric signals in copper wire is very nearly as fast as the speed of light, around 300 million meters per second, so unless one cable is a few million meters longer than the other, there won't be any difference at all in arrival of the signals. You would get a much, MUCH larger difference just by moving one speaker one millimeter closer than the other. So, no: there won't be any difference at all. The two channels will sound exactly the same, no loss of quality, no delays, no phase shift, no imaging issues, nothing. Awesome, thanks! however, I have the monitor height at 47" from center of tweeter to the floor. I couldnt find any information on where the acoustical axis is, and the manual suggested having the tweeter lined up with your ear. Is this ok or is there a known acoustical axis point for yamaha hs8 that I should use instad, or should I use the midpoint between the woofer and tweeter as the acoustical axis? The acoustic axis is going to be on the imaginary line that joins the center of the woofer to the center of the tweeter, and much closer to the tweeter, which is a bit below where you estimated. So you could probably raise your speaker a bit. In fact, for most speakers and rooms, you can go a bit higher than 47", and that can be beneficial... as long as you don't go too high! Maybe an inch, or maximum 2 inches. The reason why that is good is because it reduces reflections from the surface of your desk or console. The reason why you can't go too high, is because you would put your head too far off-axis from the speaker. THanks, ill try moving them up an inch amd then two inches and see what the results yield!2) Does it matter if one cable is say 50ft long and the other monitor cable is only 10ft long? Will this cause any delays, damage the stereo image, loss of quality or any other negative effects?Nope! Unfortunately not. The frequency is so low that any treatment would have to be huge. If you follow the theory that a porous absorber is effective at frequencies where the thickness of the absorber is 7% of the wavelength, and your frequency is 46 Hz, then your wavelength is over 24 feet! 295 inches, in fact. 7% of that is 21 inches. so you would need an absorber 21" thick on the front wall :shock: Even then, it would not be very effective, since porous absorbers just don't do very well at such low frequencies...if I know where the dip is in the low frequency, could i use some room acoustic software to correct that?Nope! That doesn't work either, because this is a phase cancellation problem: the wave going towards the wall bounces back, and cancels itself out. So if you try to EQ that, and boost the frequency that is missing, all you do is get a BIGGER cancellation! You make the dip even deeper. But since you can't actually destroy energy, all the extra power that you are pumping in with your EQ boost has to go somewhere, and normally it just ends up causing instability around that frequency, so you end up with a very long ringing tone at an adjacent frequency (something like "feedback"). That's what I meant when I said it was "impossible or extremely hard" to treat such a problem. The frequency is just too low, and it is a phase cancellation problem, so it cannot be equalized. Sorry! :) This is good to know! Thanks for the explanation.Is there a way to have the software add it back in?That's a good start, but there are 12 corners in a room, not just 4.... :) 8) True, but this will be my next step of action, how do I determine form the test results if I am sucking to much of the mids/highs out of the room. I obviously dont want to have a dead sounding space after adding more absorption to the roomI plan filling all 4 corners with roxul safe n sound asap.You set the INDIVIDUAL speakers to 80 dBC for each one, but then when both are playing back the same sound together, the total will be 86 dB. Because twice the power is the same as an increase of 6 dB, and with both speakers on, the total is twice the power. That assumes that your speakers are playing in phase, of course, and that it is the exact same sound going out through both (in other words "coherent sound"). If the sound is not coherent, then the increase in level will be less: probably around 3 dB. So this is a good test to make sure your speakers and sound system is performing fine: test each speaker by itself at 80 dB with the other one turned off, then put them both on and you should see 86 dB. If you don't get 86 dB, then there's something wrong... Thanks, I will confirm this next testI had my meter set to "C", "Slow", but I had a level of 80db. Is "86" a typo, or should I run the next test at 86 db?Finding the best location for your speakers and mix position can take a long time! I'm just giving you the basics here: the starting point. Set them up against the front wall with 4" of absorption behind them, set up your chair at about 1/3 of the distance from the front wall to the back (anywhere in the range 30% to 40% is a good starting point), aim the speakers at a spot about 16" behind your head, then do multiple REW tests with the mic and speakers in slightly different positions to see if there's a better location. Move one thing at a time, in small increments, then keep the best location for that "thing". Then move another thing in small increments, to optimize that one. Then something else. Then go back to the first thing. For example, first try moving the mic forward and backward in steps of a couple of inches, to see if there's a good improvement overall. Then try moving the speakers further apart or closer together (also in small steps of a couple of inches). Then try moving the speakers up or down a little (in very small steps: half an inch or so). Then when you have all three of those done, go back to the mic position, because there might be an even better place now... etc. Optimizing this can take a long time... and then when you have your treatment in, you can do it all over again, since the best location will probably now be somewhere else! :) As the saying goes, Rome wasn't built in a day.... and your speaker / mix position layout can't be done in a day either! :) But im soooo close! :cry: - Stuart - It's a slow process.Im anxious to get up and running and am hoping I can at least get the baseline and monitor position established asap
The speakers should always be angled to point at a spot about 16 to 24" behind your head. 18" is a good choice. Set up a mic stand or something else vertical at that location, and aim both speakers at that.Does it matter what angle I have the speakers pointing back towards me? OR should I test multiple positions between the superchunk and door? (making sure the distance from me to each speaker is equal of course)
Do REW tests, and also real listening tests, using the same music every time. Music that you already know very well.THanks, ill try moving them up an inch amd then two inches and see what the results yield!
You can see it in REW (as well as hearing it) on the RT60 graphs. There's an ideal decay time for every room, based on the volume of the room (dimensions): Calculate that for your room, then check in REW to see how your decay times are doing across the entire spectrum. The ideal situation (hard to achieve!) is that all frequencies decay at roughly the same rate, and that there is no more than 50ms difference between adjacent 1/3 octave bands.how do I determine form the test results if I am sucking to much of the mids/highs out of the room.
Right! That's why it is important to check in REW after you install each treatment device, to see how it affected the decay times. Then, if necessary, modify the device to improve the situation again. - Stuart -I obviously dont want to have a dead sounding space after adding more absorption to the room
Quick question,
I was thinking about using roxul safe n sound instead of OC 703 due to the cost and availability in my area.
However, you mentioned making 4" panels for behind the speaker, and the roxul sns only comes in 3" depths.
Is it ok to use a 3" panel of safe n sound with an air gap of 3 or 4" off the wall instead of using two layers of the 2" OC 703?
Also, I have a bunch of 2" studio foam from auralex leftover from a previous home studio, Is there any use trying to repurpose any of this material into the panels or is the density of the foam not worth the hassle?
Safe n Sound actually performs well. It is flimsy and hard to work with in my opinion though!I was thinking about using roxul safe n sound instead of OC 703 due to the cost and availability in my area.
If it were that easy and cheap, everyone would do it. The more insulation there is, the better it will perform. You're describing a cavity that is either 6 or 7" deep. (3" insulation + 3" gap, or 3" insulation + 4" gap). You could use a bit of both types of insulation to fill the cavity. For 6" you could use two batts of safe n sound. For 7" you could use 2 batts of safe n sound and 1" of OC 703. Or, worst case you could use 2 batts of safe n sound and leave a 1" air gap at the back.Is it ok to use a 3" panel of safe n sound with an air gap of 3 or 4" off the wall instead of using two layers of the 2" OC 703?
In my personal experience, removing Auralex foam from a room has yielded huge improvements. It has it's place, sure. But I'd stay away from it until your REW tests say you need to treat something that the Auralex would target. GregAlso, I have a bunch of 2" studio foam from auralex leftover from a previous home studio, Is there any use trying to repurpose any of this material into the panels or is the density of the foam not worth the hassle?
Safe n Sound actually performs well. It is flimsy and hard to work with in my opinion though!I was thinking about using roxul safe n sound instead of OC 703 due to the cost and availability in my area.If it were that easy and cheap, everyone would do it. The more insulation there is, the better it will perform. I was referring to this quote from Stuart up above "Set them up against the front wall, with just a 4" gap where you can insert a 4" panel of good absorption, such as OC-703 between the speaker and the wall." I was wondering if a 3" panel of roxul could be used instead of a 4" panel of oc703, and now that I re-read his statement, it sounds like the panel should be flush against the front wall? I was assuming a 4" panel with a 4" air gap behind the panel, and then my speakers directly in front of the panel. So would a 3" panel of safe n sound with a 1' air gap be ok?, or would I be better off locating the 703 and using the 4"panel flush against the wall. You're describing a cavity that is either 6 or 7" deep. (3" insulation + 3" gap, or 3" insulation + 4" gap). You could use a bit of both types of insulation to fill the cavity. For 6" you could use two batts of safe n sound. For 7" you could use 2 batts of safe n sound and 1" of OC 703. Or, worst case you could use 2 batts of safe n sound and leave a 1" air gap at the back.Is it ok to use a 3" panel of safe n sound with an air gap of 3 or 4" off the wall instead of using two layers of the 2" OC 703?In my personal experience, removing Auralex foam from a room has yielded huge improvements. It has it's place, sure. But I'd stay away from it until your REW tests say you need to treat something that the Auralex would target. GregAlso, I have a bunch of 2" studio foam from auralex leftover from a previous home studio, Is there any use trying to repurpose any of this material into the panels or is the density of the foam not worth the hassle?
Here is an explanation from Stuart about why you need 4" of insulation. Since SBIR is such a horrible thing, I wouldn't screw around with 3" of insulation. I'd personally opt to use 4" of 703 for this. "You can diminish the SBIR dip by using suitable absorption on the front wall, directly behind the speaker. The only problem is that the absorption has to be quite large with respect to the wavelength: at least 7% of the wavelength, and ideally more. So for low frequencies you need very, very thick insulation. The wavelength at 50Hz, for example, is about 22 feet, so the insulation would need to be nearly 2 feet thick to be effective. On the other hand, if you could arrange things so that the dip occurs at, say, 280 Hz, the wavelength is only 4 feet, and 7% of that is about three and a half inches, ... which just happens to fit a 4" thick panel of OC-703 insulation very well! And as luck would have it, the absorption coefficient of a 4" panel of OC-703 against the wall, at 280 Hz, is 1.24!" GregSo would a 3" panel of safe n sound with a 1' air gap be ok?, or would I be better off locating the 703 and using the 4"panel flush against the wall.
I guess what I wrote was a little ambiguous, talking about 4" gap and 4" panels... Greg is right: What I meant was that you need a 4" panel between the wall and the rear of the speaker. If you can move your speaker out another two inches and still have a decent frequency for the SBIR dip, then 6" of absorption would be even better. More depth is better. As long as you can keep the FRONT face of the speaker less than about 18" from the front wall, you are probably OK. 18" is the quarter wave of 190 Hz, and for waves much longer that you are into diminishing returns: even though you have more thickness of absorption, it is getting less and less effective. Personally, I'd try to keep it under 16", which is fine as long as your speaker is no deeper than twelve inches... If you can't find the right thickness insulation, then leaving an air gap between the wall and the insulation is OK, as long as you still have reasonable thickness. For example, let's say you can get your speaker face 16" away from the wall and still have a 5" gap, it would be OK to put in 4" thick insulation with a 1" gap, or 3" thick insulation with a 2" gap in the worst case, but not 2" or 1" insulation. If you only have 2" insulation, then put in two layers to get 4", plus an air gap. If you only have 1" insulation then put in five layers!. All of those options would give you roughly the same absorption in the region of 200 Hz, which is where the dip would be. Also, lower density is slightly better here: 701 would be better than 703, if you can get it. - Stuart -I was referring to this quote from Stuart up above "Set them up against the front wall, with just a 4" gap where you can insert a 4" panel of good absorption, such as OC-703 between the speaker and the wall." I was wondering if a 3" panel of roxul could be used instead of a 4" panel of oc703, and now that I re-read his statement, it sounds like the panel should be flush against the front wall? I was assuming a 4" panel with a 4" air gap behind the panel, and then my speakers directly in front of the panel. So would a 3" panel of safe n sound with a 1' air gap be ok?, or would I be better off locating the 703 and using the 4"panel flush against the wall.
Thanks for the explanation Stuart.
I would only be able to move it out another 1/2" or so, therefore, its looking like my options are 3" roxul safe n sound panel with a 1"-1.5" air gap, 4" panel of 701 or 703 with 0-1/2" air gap.
Here are some updated mdat files with the speakers moved closer to the wall, 4" gap between the rear corner of the speaker and the surface of the front wall.
I ran three different test in this position
1) 4" baseline test without the room compensation switch engaged
https://www.dropbox.com/sh/xt6aj746s3hx ... gUNya?dl=0
2) 4" baseline test with the room compensation switch at -2db
https://www.dropbox.com/sh/58kqnochk7b8 ... cs-wa?dl=0
3) 4" baseline test with the room compensation switch at -4db
https://www.dropbox.com/sh/gz3y8pc202jq ... UY-da?dl=0
Im curious to hear what you think of the results. It looks like the dip in the low end isn't as large as it was previously, however, there is a large dip around 120 now :cry:
Let me know how you think I should proceed when you get a chance to check out the mdat files.
I am going to proceed with filling the super chunk bass traps for now.
I attached a picture of how the speakers were positioned. Nevermind the position of the desk, its off center so that my short monitor cables can reach, I'll have to order longer cables if I plan on keeping them close to the front wall.
By the way, the microphone is at a distance of 76.6" away from the front wall which is about 35% of the total room length (~222")
The tip of the triangle (18" behind the microphone/ear position) is at a distance of 94.6 Inches from the front wall which is about 43% of the total room length.
The width of the room is 187"
The height of the room is 122.625" ( I believe, will have to double check), and the drop ceiling is at a height of about 94"
Thank You!
I've attached a screenshot of the REW results showing before and after moving the speakers 4" from the front wall. It looks like the drop at 46 Hz did move as you predicted (did it move to 200 Hz?), however, there is now a large drop at about 114 Hz.
The drop at 65 Hz still exists, not sure how to attack that...
Is the 114 Hz treatable?
Based on the new results, would you still conclude that its worthwhile moving the speakers up against the front wall (4" gap)?
I have finished the superchunks and will run another test today and post the results.
In the meantime, I'd love to get your feedback/input on these test results and any suggestions you may have for next steps forward.
Thanks Stuart!
I've attached updated REW files and a graph showing the room response after adding 4 floor to ceiling super chunks in the front and rear corners of the room.
Please review my last post as well to see the results of moving the speaker location to 4" From the front wall.
This latest test is with the speakers 4" from the front wall and the addition of super chunks.
https://www.dropbox.com/s/vms3zqjrjbq1m ... .mdat?dl=0
So you don’t have insulation behind the speakers?
Are you able to share some mdat files with us?
Greg
Correct, no insulation behind the speakers yet, that will be my next step. I shared a drop box link to the mdat file in my previous post. Thanks!So you don’t have insulation behind the speakers? Are you able to share some mdat files with us? Greg
Awesome. I'm excited to see the insulation behind the speaker difference. Make sure they are large panels of insulation.
Greg
I was planning on making a 4" thick panel of OC 703, 24" x 48".
Do you think that will be sufficient?
Yep.I was planning on making a 4" thick panel of OC 703, 24" x 48". Do you think that will be sufficient?
Here is the mdat file for the test run with 4" panels of 703 behind the monitors. I had to jack them up on 2x4's for now until I complete them with fabric and hanging wire.
https://www.dropbox.com/sh/zv577lct2po3 ... PnPla?dl=0
It appears to not have made a real impact on anything in the SPL graph, compared to the last test I ran after adding super chunks.
IM sure its helping tame reflections and echo in the room, but I still have some dips in the SPL id like to figure out how to attack.
Let me know what you think of the results, and what my next step forward should be.
Thanks
Not so sure about that! Here's a comparison of your original baseline results, to where you are now: That's quite a difference, I'd say! Your SBIR is gone, and your remaining issues are more typical of normal small rooms. However, the superchunks are not as effective as they should have been. How did you build those? What size? What materials? Photos of the construction? You also seem to have a flutter-echo issue, between your side walls (at least, the repeat period seems to correspond to the room width), so I'd be thinking about putting some panels on your side walls. You also have a couple of strong modal issues that might need more aggressive treatment, but first I'd like to see how you did those superchunks, and also get some side-wall panels in place, to deal with the flutter. - Stuart -It appears to not have made a real impact on anything in the SPL graph, compared to the last test I ran after adding super chunks.
Hey Stuart, Yes You are correct, in comparison from the first baseline test I ran I have come a long way! I was referring more to the difference between the last two tests I ran (one adding the superchunks, and the last one adding the 2 4” panels behind the monitors). Those two seem to be almost identical in the low end.
The super chunks are triangles of roxul safe n sound about 18” x 18” stacked up on each other from floor to the drop ceiling. There is one 3” panel of roxul standing vertically and then 15” x 15” triangles in front of that to make it 18 x 18
I attached a picture of the panels temporarily in place. I’ll be hanging them higher once wrapped and mounted
Do you think the side panels will help the dip around 114 Hz or is that a result of something else?
I’ll work on side panels next, should these be 4” also, same 703 material? Or should I use a 3” or 6” panel of roxul safe n sound instead?