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#1
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Bass resonances in large room
Recorded in a new school gym that sounded pretty good except for the bass
drum, which created about a 30 Hz rumble that carried for a couple of seconds. Roughly 40 x 60 x 24. Concrete block wall, wood floor, nondescript ceiling. Looks like a band of 703 roughly 6' high running around the room about 6' below the ceiling. Other than that rumble of thunder, this was a fairly pleasant room--at least with a floor full of performers and parents. Don't know how it would sound empty. Astonishing note: My local middle school (6th - 8th grades) has nearly 80% participation in the performing arts. Over 400 students play string instruments, another 400 in the six (!) bands, and like numbers in the choruses. Phenomenal! Is there a portable way to contain that noise if I ever wanted to record anything important in there? |
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#2
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Carey Carlan wrote:
Is there a portable way to contain that noise if I ever wanted to record anything important in there? No, but there is probably a place in the room where you can go (or where you can put the drum) where it will be less of a problem. It's a standing wave issue, in all likelyhood. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
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#3
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Carey Carlan wrote:
Is there a portable way to contain that noise if I ever wanted to record anything important in there? No, but there is probably a place in the room where you can go (or where you can put the drum) where it will be less of a problem. It's a standing wave issue, in all likelyhood. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
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#4
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Carey,
Recorded in a new school gym that sounded pretty good except for the bass drum, which created about a 30 Hz rumble that carried for a couple of seconds. In large rooms the low frequency problems are mainly excessive reverb, which is the case here. With smaller rooms the walls are close together so you get peaks and deep nulls caused by standing waves, but not reverb. In a large room you're far enough away from the walls to avoid that. But just like with small rooms, absorption is the solution - the thicker the better, and lots of it. --Ethan |
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#5
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Carey,
Recorded in a new school gym that sounded pretty good except for the bass drum, which created about a 30 Hz rumble that carried for a couple of seconds. In large rooms the low frequency problems are mainly excessive reverb, which is the case here. With smaller rooms the walls are close together so you get peaks and deep nulls caused by standing waves, but not reverb. In a large room you're far enough away from the walls to avoid that. But just like with small rooms, absorption is the solution - the thicker the better, and lots of it. --Ethan |
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#6
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"Ethan Winer" ethanw at ethanwiner dot com wrote in
: In large rooms the low frequency problems are mainly excessive reverb, which is the case here. With smaller rooms the walls are close together so you get peaks and deep nulls caused by standing waves, but not reverb. In a large room you're far enough away from the walls to avoid that. But just like with small rooms, absorption is the solution - the thicker the better, and lots of it. "Lots of it' seems to be the keyword. Assuming about 40 x 60 x 24, what percentage of the walls would need covering to damp the resonances? |
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#7
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"Ethan Winer" ethanw at ethanwiner dot com wrote in
: In large rooms the low frequency problems are mainly excessive reverb, which is the case here. With smaller rooms the walls are close together so you get peaks and deep nulls caused by standing waves, but not reverb. In a large room you're far enough away from the walls to avoid that. But just like with small rooms, absorption is the solution - the thicker the better, and lots of it. "Lots of it' seems to be the keyword. Assuming about 40 x 60 x 24, what percentage of the walls would need covering to damp the resonances? |
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#8
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"Ethan Winer" ethanw at ethanwiner dot com wrote in
: In large rooms the low frequency problems are mainly excessive reverb, which is the case here. With smaller rooms the walls are close together so you get peaks and deep nulls caused by standing waves, but not reverb. In a large room you're far enough away from the walls to avoid that. But just like with small rooms, absorption is the solution - the thicker the better, and lots of it. Call the principal. Tell him the school is in for a giat liability suit if some kid runs into one of the walls, and that they should get real thick padding all around. That will cover 1/4 of the walls. Then you might be able to afford enought for the top of the walls. On Wed, 17 Nov 2004 16:47:40 GMT, Carey Carlan wrote: "Lots of it' seems to be the keyword. Assuming about 40 x 60 x 24, what percentage of the walls would need covering to damp the resonances? Willie K. Yee, M.D. http://users.bestweb.net/~wkyee Developer of Problem Knowledge Couplers for Psychiatry http://www.pkc.com Webmaster and Guitarist for the Big Blue Big Band http://www.bigbluebigband.org |
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#9
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"Ethan Winer" ethanw at ethanwiner dot com wrote in
: In large rooms the low frequency problems are mainly excessive reverb, which is the case here. With smaller rooms the walls are close together so you get peaks and deep nulls caused by standing waves, but not reverb. In a large room you're far enough away from the walls to avoid that. But just like with small rooms, absorption is the solution - the thicker the better, and lots of it. Call the principal. Tell him the school is in for a giat liability suit if some kid runs into one of the walls, and that they should get real thick padding all around. That will cover 1/4 of the walls. Then you might be able to afford enought for the top of the walls. On Wed, 17 Nov 2004 16:47:40 GMT, Carey Carlan wrote: "Lots of it' seems to be the keyword. Assuming about 40 x 60 x 24, what percentage of the walls would need covering to damp the resonances? Willie K. Yee, M.D. http://users.bestweb.net/~wkyee Developer of Problem Knowledge Couplers for Psychiatry http://www.pkc.com Webmaster and Guitarist for the Big Blue Big Band http://www.bigbluebigband.org |
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#10
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In large rooms the low frequency problems are mainly excessive reverb,
which is the case here In large rooms the high frequency problems are mainly erverb..as you go lower it's a whole different game. John A. Chiara SOS Recording Studio Live Sound Inc. Albany, NY www.sosrecording.net 518-449-1637 |
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#11
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In large rooms the low frequency problems are mainly excessive reverb,
which is the case here In large rooms the high frequency problems are mainly erverb..as you go lower it's a whole different game. John A. Chiara SOS Recording Studio Live Sound Inc. Albany, NY www.sosrecording.net 518-449-1637 |
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#12
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Carey,
Assuming about 40 x 60 x 24, what percentage of the walls would need covering to damp the resonances? How much absorption you need to obtain a particular RT60 (reverb decay time) depends on what's in the room now - what's on all the surfaces, how many windows, cinder block or sheetrock walls, etc. I'll guess that 20% of the total area of all six surfaces is a good start. Since boominess is the main problem and you want the space to sound good for music, not just speech, a permanent treatment solution would use rigid fiberglass that's four inches thick. Thicker materials don't absorb "more" than thin ones, but they do absorb to a lower frequency. If the fiberglass panels are suspended away from the walls/ceiling by a few inches they'll absorb to an even lower frequency. I noticed you asked about a portable solution, and that's what my company RealTraps makes. But understand that for a space that size you're looking at a fair number of panels. --Ethan |
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#13
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Carey,
Assuming about 40 x 60 x 24, what percentage of the walls would need covering to damp the resonances? How much absorption you need to obtain a particular RT60 (reverb decay time) depends on what's in the room now - what's on all the surfaces, how many windows, cinder block or sheetrock walls, etc. I'll guess that 20% of the total area of all six surfaces is a good start. Since boominess is the main problem and you want the space to sound good for music, not just speech, a permanent treatment solution would use rigid fiberglass that's four inches thick. Thicker materials don't absorb "more" than thin ones, but they do absorb to a lower frequency. If the fiberglass panels are suspended away from the walls/ceiling by a few inches they'll absorb to an even lower frequency. I noticed you asked about a portable solution, and that's what my company RealTraps makes. But understand that for a space that size you're looking at a fair number of panels. --Ethan |
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#14
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"Ethan Winer" ethanw at ethanwiner dot com wrote in
: I noticed you asked about a portable solution, and that's what my company RealTraps makes. But understand that for a space that size you're looking at a fair number of panels. Thanks, Ethan. That's what I needed to know. IOW, it isn't an option. |
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#15
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"Ethan Winer" ethanw at ethanwiner dot com wrote in
: I noticed you asked about a portable solution, and that's what my company RealTraps makes. But understand that for a space that size you're looking at a fair number of panels. Thanks, Ethan. That's what I needed to know. IOW, it isn't an option. |
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#16
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Carey Carlan wrote in message .191...
"Ethan Winer" ethanw at ethanwiner dot com wrote in : I noticed you asked about a portable solution, and that's what my company RealTraps makes. But understand that for a space that size you're looking at a fair number of panels. Thanks, Ethan. That's what I needed to know. IOW, it isn't an option. Well if you don't care what the live show sounds like but you want to make the RECORDING sound better, and your problem is really at 30 Hz, a graphic EQ will be a big help. Just notch out the 30 Hz. Mark |
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#17
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Carey Carlan wrote in message .191...
"Ethan Winer" ethanw at ethanwiner dot com wrote in : I noticed you asked about a portable solution, and that's what my company RealTraps makes. But understand that for a space that size you're looking at a fair number of panels. Thanks, Ethan. That's what I needed to know. IOW, it isn't an option. Well if you don't care what the live show sounds like but you want to make the RECORDING sound better, and your problem is really at 30 Hz, a graphic EQ will be a big help. Just notch out the 30 Hz. Mark |
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#18
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#19
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#20
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Carey Carlan wrote:
(Mark) wrote in . com: Well if you don't care what the live show sounds like but you want to make the RECORDING sound better, and your problem is really at 30 Hz, a graphic EQ will be a big help. Just notch out the 30 Hz. At best a second-rate solution. I still need the fundamental of that big bass drum and some of the resonance. It just needs to fade about three times as fast. Does anyone make an anti-reverb? g No, but they do make an anticompressor. A multiband compressor that will also do expansion can be a big help for fixing this sort of thing. Make a band centered around the problem area and expand it while leaving the rest of the bandwidth unchanged. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
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#21
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Carey Carlan wrote:
(Mark) wrote in . com: Well if you don't care what the live show sounds like but you want to make the RECORDING sound better, and your problem is really at 30 Hz, a graphic EQ will be a big help. Just notch out the 30 Hz. At best a second-rate solution. I still need the fundamental of that big bass drum and some of the resonance. It just needs to fade about three times as fast. Does anyone make an anti-reverb? g No, but they do make an anticompressor. A multiband compressor that will also do expansion can be a big help for fixing this sort of thing. Make a band centered around the problem area and expand it while leaving the rest of the bandwidth unchanged. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
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#22
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#23
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#24
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Does anyone make an anti-reverb? g
Transient Designer type units can do this on recordings. John A. Chiara SOS Recording Studio Live Sound Inc. Albany, NY www.sosrecording.net 518-449-1637 |
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#25
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Does anyone make an anti-reverb? g
Transient Designer type units can do this on recordings. John A. Chiara SOS Recording Studio Live Sound Inc. Albany, NY www.sosrecording.net 518-449-1637 |
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#26
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Well that does rasise an interesting question. If a room resonates at
30 Hz and creates a freq response peak and ringing at 30 Hz, if you create an EQ curve that matches the inverse of the room so it just flattens the peak, it should also take out the ringing. No? PLUS...what system do you have that is actually producing substantial energy at 30HZ? It is probably producing harmonics of that. John A. Chiara SOS Recording Studio Live Sound Inc. Albany, NY www.sosrecording.net 518-449-1637 |
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#27
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Well that does rasise an interesting question. If a room resonates at
30 Hz and creates a freq response peak and ringing at 30 Hz, if you create an EQ curve that matches the inverse of the room so it just flattens the peak, it should also take out the ringing. No? PLUS...what system do you have that is actually producing substantial energy at 30HZ? It is probably producing harmonics of that. John A. Chiara SOS Recording Studio Live Sound Inc. Albany, NY www.sosrecording.net 518-449-1637 |
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#28
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Mark wrote:
Well that does rasise an interesting question. If a room resonates at 30 Hz and creates a freq response peak and ringing at 30 Hz, if you create an EQ curve that matches the inverse of the room so it just flattens the peak, it should also take out the ringing. No? Cascaded linear systems? It does. But Carey wants to take the ringing out without removing the peak, probably because the peak is not evident in the direct sound. This is not a very common problem, and it's really a sign of just catastrophically bad acoustics. But considering that I have a gig in a high school multipurpose room myself in five hours... --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
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#29
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Mark wrote:
Well that does rasise an interesting question. If a room resonates at 30 Hz and creates a freq response peak and ringing at 30 Hz, if you create an EQ curve that matches the inverse of the room so it just flattens the peak, it should also take out the ringing. No? Cascaded linear systems? It does. But Carey wants to take the ringing out without removing the peak, probably because the peak is not evident in the direct sound. This is not a very common problem, and it's really a sign of just catastrophically bad acoustics. But considering that I have a gig in a high school multipurpose room myself in five hours... --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
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#30
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Blind Joni wrote:
Well that does rasise an interesting question. If a room resonates at 30 Hz and creates a freq response peak and ringing at 30 Hz, if you create an EQ curve that matches the inverse of the room so it just flattens the peak, it should also take out the ringing. No? PLUS...what system do you have that is actually producing substantial energy at 30HZ? It is probably producing harmonics of that. Live tympani. In a gymnasium. This is the kind of gig that it is best to turn down altogether. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
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#31
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Blind Joni wrote:
Well that does rasise an interesting question. If a room resonates at 30 Hz and creates a freq response peak and ringing at 30 Hz, if you create an EQ curve that matches the inverse of the room so it just flattens the peak, it should also take out the ringing. No? PLUS...what system do you have that is actually producing substantial energy at 30HZ? It is probably producing harmonics of that. Live tympani. In a gymnasium. This is the kind of gig that it is best to turn down altogether. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
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#32
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Mark wrote: Well that does rasise an interesting question. If a room resonates at 30 Hz and creates a freq response peak and ringing at 30 Hz, if you create an EQ curve that matches the inverse of the room so it just flattens the peak, it should also take out the ringing. No? Cascaded linear systems? If the equalization is not out of phase with the resonance as measured at the speaker (which is very hard to do) it can add to it. Inversion means both magnitude and phase correction. Bob -- "Things should be described as simply as possible, but no simpler." A. Einstein |
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#33
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Mark wrote: Well that does rasise an interesting question. If a room resonates at 30 Hz and creates a freq response peak and ringing at 30 Hz, if you create an EQ curve that matches the inverse of the room so it just flattens the peak, it should also take out the ringing. No? Cascaded linear systems? If the equalization is not out of phase with the resonance as measured at the speaker (which is very hard to do) it can add to it. Inversion means both magnitude and phase correction. Bob -- "Things should be described as simply as possible, but no simpler." A. Einstein |
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#34
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Live tympani. In a gymnasium.
This is the kind of gig that it is best to turn down altogether. --scott Absolutely..I played Tympani in high school..we always rehearsed in the auditorium..but the competitions were in large gyms..very distracting. Once at All State I had 128 measures of rest and miscounted..ended with my big tympani flurry with great conviction and style..too bad I was one measure ahead of the rest of the group. John A. Chiara SOS Recording Studio Live Sound Inc. Albany, NY www.sosrecording.net 518-449-1637 |
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#35
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Live tympani. In a gymnasium.
This is the kind of gig that it is best to turn down altogether. --scott Absolutely..I played Tympani in high school..we always rehearsed in the auditorium..but the competitions were in large gyms..very distracting. Once at All State I had 128 measures of rest and miscounted..ended with my big tympani flurry with great conviction and style..too bad I was one measure ahead of the rest of the group. John A. Chiara SOS Recording Studio Live Sound Inc. Albany, NY www.sosrecording.net 518-449-1637 |
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#36
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#37
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#38
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You're assuming that the sound comes from a speaker, an electrical
signal. Mine comes from a 6' concert bass drum. (The fundamental of which I really want in the recording). Make that a FIVE foot concert bass drum. Measuring the drum against the drummer, I forgot the percussionist was only a 7th-grader. |
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#39
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You're assuming that the sound comes from a speaker, an electrical
signal. Mine comes from a 6' concert bass drum. (The fundamental of which I really want in the recording). Make that a FIVE foot concert bass drum. Measuring the drum against the drummer, I forgot the percussionist was only a 7th-grader. |
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#40
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Scott Dorsey wrote:
It does. But Carey wants to take the ringing out without removing the peak, probably because the peak is not evident in the direct sound. This is not a very common problem, and it's really a sign of just catastrophically bad acoustics. But considering that I have a gig in a high school multipurpose room myself in five hours... Which makes for a great opportunity for some of us to get educated. So, are you going to print your multiband expansion to tape (or DAT or DISK) live? Or is this something you can do later? |
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