I really need help with a DIY sound room. - diyAudio
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Old 27th January 2002, 04:43 PM   #1
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Default I really need help with a DIY sound room.

I could really need your guys help on this.

I want to confert a storage room into a sound room.There is one door that opens into the room.There is no windows (it was designed as a "safe"room) by safe I mean that it is not accessible from the outside.
I will use aircons for fresh air and to keep the temperature constant. If possible it must be fairly soundproof because it's close to my bedroom.

The room size is as follow: L=6.3m w=3.75m h=2.8m a Total of 66.15 cubic meters. The only things in the room will be the sound equipment,chairs and TV. I will used the room for stereo listening as well as home cinema. Advice on DIY speakers is more than welcome.I want to build decent speakers even if I have to build two sets (stereo and cinema).

I don't know wat the sound would do in the almost empty room.If anyone could give me advise on what to do with the walls,floor and celing I would really appreciate it.

Consider money to be no opject.

Thanks.
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Old 27th January 2002, 05:56 PM   #2
Super is offline Super  United States
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Considering the fairly small size of your room, I would suggest using smaller speakers. Large floorstanders would likely overload your listening room and cause problems.

In my opinion, its more what to avoid than not to avoid. Bare hard floors cause nasty reflections, so go with carpet, or at the least, an area rug. Drop ceilings should also be avoided.

Also, some sound absorption panels and diffusers would be nice to experiment with. The good thing about this is that they can control reflections, and there are many inexpensive ways to construct various types of them.

Good luck
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Old 27th January 2002, 06:18 PM   #3
ucla88 is offline ucla88  Tahiti
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here's an interesting link

even if it is somewhat peripheral.
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Old 27th January 2002, 06:36 PM   #4
PassFan is offline PassFan  United States
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There is some good info on the site ucla88 recommended. If I get a chance today I will post a table of different materials and their sound coefficients. This may be helpful to adjust the rooms frequency balance if you run a real time analyzer to check it. Some of these are inexpensive and only require a test cd with white noise and a microphone. Also, I know its hard sometimes but parrallel surfaces are to be avoided if possible. The only way to get rid of them though is to build a room within a room, which is done alot in the recording industry. Carpet is a good deadener which is advisable, but I would check the room before hanging bass traps without knowing what your target frequencies are. Also plan out your power req. and placement of speakers. You might want to install all cabling in the walls and especially want to have adequate power were you need it. It doesn't have to be ugly if you have the money and your wife will love you for it.
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Old 27th January 2002, 08:54 PM   #5
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I put galvinized steel conduits in the walls I built. They have slow 90 degree turns. That way I can pull the wires out and replace them, or run more wires. It works really good for shielding too. There is very little noise in my rear speakers.

I also ran a separate 30 amp power outlet just for my audio equipment in the front of the room.

I angled the walls by 3 degrees, and built an alcove in the back of the room. The only problem I have with bass is the room tends to eat bass. But, I solved that with a killowatt of sub.

All of the walls and ceiling are built with cross-braced studs insulated with the best I could get to fit. Then 1/4" plywood and 5/8" drywall. The walls are textured with what is known as "smash-texture" the ceiling is standard popcorn texture. I have the best carpet I could afford. With the pad it's about an inch thick. I get about a 30dB cut in sound C-weighted just on the other side of the door, which, of course, is solid core pine.

It's a beautiful room that my wife and I spend many hours in.

I hope some of these ideas can be integrated into your room.

pixie
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Old 27th January 2002, 09:25 PM   #6
PassFan is offline PassFan  United States
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Pixie:
It sounds like a lot of hard work but I'm sure it was worth it. Angling the wall helps to eliminate standing waves. A sub is one way to overcome a loss of the lower freq. though it might have been cheaper to analyze it and compensate through the use of different material, maybe not. It seems I recall wood absorbing lower freq. really well. That may be the reason, although without it you may not have realized such a drastic noise loss outside the room. Did you happen to measure the loss with an A weighting?
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Old 27th January 2002, 11:43 PM   #7
PassFan is offline PassFan  United States
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Default Absorption Coefficients

Okay hear they are.

125hz 250hz 500hz 1khz 2khz 4khz

Brick .03 .03 .03 .04 .05 .07

Brick, painted .01 .01 .02 .02 .02 .03

Carpet, heavy .02 .06 .14 .37 .60 .65
(on concrete)

Same on 40 oz. .08 .24 .57 .69 .71 .73
hairfelt or rubber

Same with latex .08 .27 .39 .34 .48 .63
backing on 40 oz.
hairfelt or rubber

Concrete block .36 .44 .31 .29 .39 .25

Concrete block .10 .05 .06 .07 .09 .08
painted

Fabrics
Light velour 10 oz .03 .04 .11 .17 .24 .35
per sq. yd. hung str.
in contact w/wall

Medium velour 14 oz.07 .31 .49 .75 .70 .60
per sq. yd. draped
to half area

Heavy velour 18 oz. .14 .35 .55 .72 .70 .65
per sq. yd. draped
to half area

Floors
concrete, Terrazzo .01 .01 .015 .02 .02 .02

linoleum on concrete.02 .03 .03 .03 .03 .02

Wood .15 .11 .10 .07 .06 .07

Glass window .35 .25 .18 .12 .07 .04

1/2" gypsum on .29 .10 .05 .04 .07 .09
2x4 16" oc.

Marble or glazed .01 .01 .01 .01 .02 .02
tile

Plaster, smooth on .013 .015 .02 .03 .04 .05
tile, brick

Plaster, rough on .14 .10 .06 .05 .04 .03
lathe, same with
smooth finish

Plywood paneling3/8 .28 .22 .17 .09 .10 .11

Whew!!!

Keep in mind these are how much absorption a specific material has, not reflection

Edit: Sorry, the columns didn't line up like I typed them, but the numbers correspond to the freq. at the top.
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Old 29th January 2002, 02:19 AM   #8
BAM is offline BAM
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For your speakers, use some with a Scan-Speak 7" carbon fibre/paper mid-woofer. The cone looks weird, but that actually helps the sound. They go down nice and low, and you can build a subwoofer with two of the 8" Scan-Speak paper cone woofers. You'll end up with something that looks like the Altec Lansing 2100 subwoofer, only in a sealed box, bigger with 8's instead of 4's and with frequency response down to 20 Hz using a Linkwitz Transform circuit. If tight, accurate bass (not window-shaking) is your thing, do the thing with the sealed 8's, but if loud bass is your thing, then do a sealed Dayton Titannic MkII 12"

Run the mains down to 50 and then from there use the subwoofer to go down to 20 Hz. Build the subwoofer into a sealed box and use the Linkwitz Transform circuit. There are sources on the internet that are actually a better source for information on designing a Linkwitz Transform than Linkwitz's own site, from my experience. A spreadsheet is widely available that will allow you to input the Ftc and Qtc of the sealed enclosure and get the values for the capacitors and resistors and stuff.
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Old 30th January 2002, 10:53 PM   #9
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I guess this would be the time to ask about acoustic panels.

I'm just looking for something for the first reflection points on the side walls for now. The graph shows about a 10dB-20dB rise at and above 1600Hz.

I read somewhere that the material should be 1/2 the wavelength of the frequency you want to dampen. So, what's that? 4.25in? wavelength(m) = 1130ft/s / f(Hz) correct?

The panels on Jon Risch's page are a bit excessive for me. How about fabric over styrofoam panels? I can get them as thick as 2" at a hobby store.

I figured out the mirror points for my mains and center. I need about 3' x 3' panels. The problem is I need to be able to walk past one of them. So, it can't be very thick. Two inches would be about the limit. How about 1 inch styrofoam + polyester batting?

So, what do I have wrong? What would be a better choice of materials?

pixie
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Old 30th January 2002, 11:15 PM   #10
PassFan is offline PassFan  United States
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If you refer to my chart on absorption coefficients it shows three weights of velour fabric and that they would be an excellent choice to attenuate in your frequency range. You will have to experiment with them though. The styrofoam may wind up affecting some other frequency. You may try hanging them on the walls and replotting the spectrum. Once you get it where you want it then figure out a permanent installation. Note the coefficient difference for mounting on the wall versus hanging, as well as the weight. You may be able to mount directly to the wall with the lighter velour and do the whole room. As for your size equation, I don't know, sorry.
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