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Author Topic: Sound absorption on the cheap  (Read 11981 times)

Randy Pence

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Re: Sound absorption on the cheap
« Reply #10 on: December 07, 2008, 09:22:00 pm »

Yes, treating the stage will make mixing easier.  I had originally read doing the floor, but I would do both if possible.

With rockwool, one does have to build a lot of panels, but they are very effective.  Spacing them from the wall will increase lf performance.  I like modular ideas in a club, because you never know what someone will do to a big piece of material.  Washing fire retardant fabric can remove the protective coating!
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Jason Dermer

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Re: Sound absorption on the cheap
« Reply #11 on: December 07, 2008, 10:24:32 pm »

Find a bonded/ insured acoustic design company.

Pay them to do the work safely and properly.

Enjoy your SAFE, better sounding room.

Unless you are willing to take the chance at making the sound worse and have the insurance to cover the possibility of EVERYONE at your gig DYING, There are no other options.


As I have mentioned multiple times in the past, the last Great White show before the Station disaster was at one of my house gigs, so I do not take the sound deadening issue lightly. Do it right, or stay away.
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Jason Dermer
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"Rock & Roll and cars are just slightly different versions of the same mental disorder."- Peter Egan

Micah McFadden

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Re: Sound absorption on the cheap
« Reply #12 on: December 08, 2008, 01:01:53 am »

You need to find some acoustically transparent fabric to get the most out of the absorbers you will be putting up.   I suggest

using some Guildford of Maine FR701 fabric.  This fabric is a bit expensive, but it seems to be the #1 choice for acoustic

professionals when building broadband absorbers.  If you want some fabric that will perform the same for less money, I would

suggest this fabric:        http://www.acoustimac.com/index.php?page=shop.product_detail        s&flypage=shop.flypage&product_id=22&category_id        =5&manufacturer_id=0&option=com_virtuemart&Itemi d=21

I did not see whether or not this fabric is fire treated or not.  I know the Guildford of Maine fabric is treated and they

even provide data sheets for you to show to the fire marshal who might happen to ask about that fabric you have hanging on the

wall.   For other acoustic materials you might want to check here:         http://www.acoustimac.com/index.php?page=shop.browse&cat egory_id=11&option=com_virtuemart&Itemid=21

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Micah McFadden

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Re: Sound absorption on the cheap
« Reply #13 on: December 08, 2008, 01:18:21 am »

Also another tip would be to try and use at least 2 inch thick panels.  The thicker the panel the lower in frequency it will

absorb.  A thin panel will only reduce the upper frequency range, while still allowing the mids to reflect off the wall.  Using at

least 2 inches thick will help get the absorption down into the mids.  I would also suggest using Owens Corning 703.  You should

be able to find a local insulation place that would have it in stock, or you can easily buy it off of many websites and have it

shipped to you.
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Tim Padrick

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Re: Sound absorption on the cheap
« Reply #14 on: December 08, 2008, 02:33:56 am »

Corning also makes SelectSound, which is basically 703 in black, so the cloth has a better chance of hiding the color.

Dick Rees

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Re: Sound absorption on the cheap
« Reply #15 on: December 08, 2008, 09:49:35 am »

Jason Dermer wrote on Sun, 07 December 2008 21:24

Find a bonded/ insured acoustic design company.

Pay them to do the work safely and properly.

Enjoy your SAFE, better sounding room.

Unless you are willing to take the chance at making the sound worse and have the insurance to cover the possibility of EVERYONE at your gig DYING, There are no other options.


As I have mentioned multiple times in the past, the last Great White show before the Station disaster was at one of my house gigs, so I do not take the sound deadening issue lightly. Do it right, or stay away.


+1.  The longer I'm at it, the less I care to alter any building construction.  You CAN be held liable even if someone else screws up what you did right.  When the S*** hits.......they'll sue everyone who walked in the front door with a hammer.  Don't let that be you.

On a side line:  Low frequency control does not rely entirely on absorptive material.  A certain amount of dead space contained by the proper materials (bass trap) will really do the job.  The problem is that you have to have the space to waste.
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Art Welter

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Re: Sound absorption on the cheap
« Reply #16 on: December 09, 2008, 02:12:27 pm »

Brad,

All the prior posts about having it done right, and making sure anything installed is fireproof is good advice.

However, all the ideas so far mostly only deaden the high frequency, which often make lower frequency problems even more apparent by comparison.

Another approach not mentioned so far that works quite well in small and larger scale rooms is a type of diffuser panel I encountered in an orchestral rehearsal room.

The room was a typical ballroom type room, about 70’ x70’ and 10’ ceilings. I expected it to sound like the usual boom boom room, but was surprised to find I could run my system at upwards of 115 dB (where it was running out of headroom) without any of the flutter echoes, boom or the other crud associated with that type of room shape.

I later built the same type of panels for a friend who wanted to turn his cinderblock single car garage (probably roughly the size of the stage you are trying to fix) into a rehearsal/recording studio.

Each panel uses a piece of 4’x8’ 1/4” ply bent on arcs which are cut from 2”x12” material. Picture the cross section of a parabolic satellite dish vertically attached to a frame, like an airplane wing, or a giant roll and pleat.

The back side of the frame has fiberglass insulation installed. The sections I made, and the ones I copied, used 4’x8’ 1/4” ply. If your ceiling is higher, the “wing” could be made higher.

The arcs were cut to a 4” depth if I recall correctly, with a 1.5” frame thickness, for a total depth of just under 6” in the center. The arc is a section of a circle with approximately 57.5” radius. Four arcs per 4’x8”, and 1.5” angled “studs” on either side. The left to right dimension is slightly under 48” because of the arc, so you need to lay one up to figure exactly how many sheets you need for the finished length.


The reverse parabola scatters, rather than absorbs the sound waves, the spectral content stays roughly the same, while the standing waves and HF chatter are largely eliminated. The 1/4” material flexes enough that it (with the fiberglass behind) eliminates much of the mid-bass build up common to a small room.

I can not normally stand to be on a small live stage without hearing protection with even a moderately loud drummer. With this type of treatment not only do drums sound good, but everything is easy to hear distinctly throughout the room. Stage volume escalation should  tend to be less than on a “dead” stage, where musicians crank up because their apparent volume seems less, or a too live stage where they crank up to hear themselves over the wash.

Cutting the arcs with a band saw took a while, but the rest of the construction is about the equivalent of doing a sheet rock wall of the same size.

Art Welter

P.S. Really large sonotubes could be cut up for a similar effect as what I described above, and would be a snap to install.

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SteveKirby

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Re: Sound absorption on the cheap
« Reply #17 on: December 09, 2008, 02:37:42 pm »

One small suggestion, while it may seem like a good idea, try not to totally deaden the area behind the drummer.  Drapes or other HF absorbtion kills the sound of the kit and tends to make the drummers bang harder.  A bit of diffuse reflection behind them will let them balance themselves better with the rest of the band.

First order of treatment should be along the sides and rear corners of the stage and then the short dimensions of the room.
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Brad Weber

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Re: Sound absorption on the cheap
« Reply #18 on: December 09, 2008, 04:16:57 pm »

Art Welter wrote on Tue, 09 December 2008 14:12

The reverse parabola scatters, rather than absorbs the sound waves, the spectral content stays roughly the same, while the standing waves and HF chatter are largely eliminated.

I agree that convex diffusers can be very effective and any diffusion would probably help however convex or 'barrel' diffusers are one dimensional diffusers and are spectral, the overall size and depth of the diffusers will affect the frequency range over which they are effective.  Providing elements of varying size and radii can help provide effectiveness over a wider range and having varying orientations can also help with ceiling applications.

Other similar options might include pyramidal diffusers, which are two dimensional diffusers and for which some of manufactured units are asymmetrical and can then be randomly rotated to provide more random diffusion.  Another option, although not necessarily for those on a tight budget, might be RPG BAD or Kinetics TAD panels which are absorbers at lower frequencies and transition to binary diffusers at higher frequencies, similar to what was apparently intended with the custom built panels noted but with two dimensional diffusion.  If budget is even more forgiving, then RPG Omniffusor, Abffusor or QRD panels might even be an option.
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Brad Weber
muse Audio Video

John Halliburton

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Re: Sound absorption on the cheap
« Reply #19 on: December 09, 2008, 05:11:27 pm »

Brad Weber wrote on Tue, 09 December 2008 15:16

Art Welter wrote on Tue, 09 December 2008 14:12

The reverse parabola scatters, rather than absorbs the sound waves, the spectral content stays roughly the same, while the standing waves and HF chatter are largely eliminated.

I agree that convex diffusers can be very effective and any diffusion would probably help however convex or 'barrel' diffusers are one dimensional diffusers and are spectral, the overall size and depth of the diffusers will affect the frequency range over which they are effective.  Providing elements of varying size and radii can help provide effectiveness over a wider range and having varying orientations can also help with ceiling applications.

Other similar options might include pyramidal diffusers, which are two dimensional diffusers and for which some of manufactured units are asymmetrical and can then be randomly rotated to provide more random diffusion.  Another option, although not necessarily for those on a tight budget, might be RPG BAD or Kinetics TAD panels which are absorbers at lower frequencies and transition to binary diffusers at higher frequencies, similar to what was apparently intended with the custom built panels noted but with two dimensional diffusion.  If budget is even more forgiving, then RPG Omniffusor, Abffusor or QRD panels might even be an option.



Varying the curvature of the curved diffusers shouldn't be much of a problem.  Also, a more accurate method of cutting arcs out of 2x12's(I'd use sections of Baltic Birch plywood, but that's me) would be to make a pattern for a router to follow using a bearing bit or template bushing installed in the router base-common accessories for the router.  1/4" plywood should still flex fairly easy to even a 24" radius, probably smaller, depending on the plywood type.
As Art also mentioned, this could be done using Sonotube, and you could just buy a selection of diameters to slice up lengthwise, make a frame to hold a set of these slices, and fill the backside with insulation. Sonotube is available 22 diameters from 6"-60", and lengths from 3-20'.  Fun!

Best regards,

John
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