DIY Acoustic Panels

[fauzigarib]

Hi there,

I was wondering if anyone knew how effective this would be to dampen the sound in my HT.

I was going to make 2' x 4' x 3/4" MDF panels wrapped in Bleached Jute. The material itself looks nice enough to come in our living room (where the HT is based.. God, long story!).

I was wondering if anyone had any experience with this.

Regards,

Fauzi

[Kal Rubinson]

MDF is pretty useless as acoustic treatment.

Kal

[fauzigarib]

MDF is pretty useless as acoustic treatment.

Kal

Hmm... That's that then... Why though? With the right covering, wouldn't it work?

What are you thinking of for a market like Pakistan, where acoustic treatments are not readily available? Something more or less dense?

thanks for the help, Kal.

Fauzi

[ThomasW]

This should get you started....

http://home.comcast.net/~thomasw-2/SubwooferSetupandEQpage9.html

[Kal Rubinson]

Also: http://www.ethanwiner.com/acoustics.html and www.rivesaudio.com

Kal

[Chris D]

Yeah, I use MDF for home theater construction wher I need solid, rigid materials like columns where mass is also useful for bass absorption. But as an "acoustical panel" anything like MDF is just going to reflect other frequencies, so you don't want to use it for large flat things.

[KeithM]

May I reccomend foam by mail?
Not sure if they'll ship to your location though.

[fauzigarib]

Let me clarify...

Hi there,

Thanks for the info folks. The couple websites that were given are HIGHLY informative...

Actually, my HT is in our drawing room. The walls / ceiling are concrete, and the floor is marble, with a spatter of flush wood paneling here and there on the floor. Also the dimensions are really weird.. .12' x 32', with a 10' high ceiling.

The problem that I'm having is more with the highs right now (though, I haven't really paid attention to the sub, so that may end up being an issue also). There is (as expected) quite a bit of echo in the room. By the time a movie ends, it's actually a tiring experience.


Of course, that was an expected result. Now how to fix it?

I've plugged in my values into a Room Mode Calculator and got a visual graph for 4 axial standing waves along each of the dimensions. What should I be looking for?

I'm assuming that'll give me kind of an idea of the physical location where treatment needs to be applied, correct?

Any further help is GREATLY appreciated.

Fauzi

[Kal Rubinson]

1. Any rectangular room, especially with those hard surfaces, will have distinct modes and their primary influence is in the sub-200Hz range. Fixing these peaks/nulls requires some bulk and, therefore, a committment to fixing it without too much esthetic compromise.

2. The high frequency ringing is due more to the reflective surfaces than to the dimensions. This can be greatly ameliorated with flat panels. I suggest 1"-2" rigid fiberglass (Corning 703 or 705 or equivalent) covered in any of the many GOM fabrics that suit your decor. At CEDIA, Auralex showed kits for this but none suited my taste. YMMV.

I used Bryan Pape at www.sensiblesoundsolutions.com. He is knowledgeable, helpful and capable. I do not know what his shipping arrangements to you will be but you can ask.

Kal

[ThomasW]

The problem that I'm having is more with the highs right now.....

Of course, that was an expected result. Now how to fix it?

That's called 'slap echo' and it's the easiest to fix.

There's a techinque called the 'mirror trick'. This involves sitting in the listening position and having a friend move around the room holding a mirror against the walls, ceiling, and floor) Anywhere you can see a reflection of a speaker is a first reflection point and should be treated. Treatment can be oriental rugs or traps made from any appropriate sound absorbing material. I use oriental rugs on the floor and on the walls in my main listening room, since they're visually more interesting than standard traps.

I've plugged in my values into a Room Mode Calculator and got a visual graph for 4 axial standing waves along each of the dimensions.

Knowing where the modes are tells you where not to sit ....:wink:

Using bass traps starting with the corners, and dealing with other locations later will smooth the bass response.

If you have local access to fiberglass, rockwool, cotton or similar form of insulation, bass traps aren't particularily difficult or expensive to fabricate.

For your corner bass traps bigger/thicker is always better. For example, the corner traps behind my dipole ESL/magnetic planar arrays are 1/4th cylinder in shape, 94" tall and the radius is 24". They're filled with standard fiberglass batting held in place with a wire mesh that's covered with a dacron batting and soft cotton cloth. (Sorry I don't have any pictures of the building process since these were built some 15yrs ago.)

[Chris D]

Fauzi - actually, with those dimenions, we can make you a ROCKIN' theater. You'll find 12' to be a little narrow, but that's fantastic for depth and height.

[fauzigarib]

Bipolar speakers...

Fauzi - actually, with those dimenions, we can make you a ROCKIN' theater. You'll find 12' to be a little narrow, but that's fantastic for depth and height.

Chris!!!

Awesome! Err... how?

I temporarily put the speakers in place... no final fixing yet, just wanted to see how it sounded. It sounds.. well.. just so so...

Much worse than the exact same setup sounded in my 14 x 20 room. But that smaller room was kind of geared up for the purpose of HT (damping, tamed resonances, etc), whereas this room isn't... So part of what I was hearing was that.

But I have a feeling that the narrowness will be tough to control. However, what I am planning (and let me know what you think of this idea), is that since it is a narrow room, I'm going to put bipolars in the rears, very close to the top corners. Say about 1 ft away from the ceiling corners, so that the sound reflects off the side walls. This might give a feeling of a "wider" room.

And for the sides, I'm planning on putting small, bookshelf direct radiating speakers, just behind but pointing straight at the listening position.

[Chris D]

Well, mine's 14x22x8. You've got me beat on two dimensions. Unfortunately, I'd say that the one that I've got you on (width) is the most critical with our dimension types. But do-able.

Mostly, you'll be limiting your seating in each row, probably just two seats side-by-side. But with 10' height and ESPECIALLY 32' length, you'll be able to do at least 3 rows of seats if you build risers. (this is a dedicated room, right? An ex-parlor, not theater AND parlor?) Yes, use bipoles/diploes on side and rear walls. Your room depth makes you a great candidate for 7.1 surround sound, and you'll find 7.1 material like Dolby Pro Logic IIx to be very enveloping and useful. (those with shallower rooms don't recognize this as much)

Sounds like right now your primary concern is acoustics and echoes. Good for you for focusing on this--carpet, rugs, wall hangings, etc, will be your friend.

[fauzigarib]

Chris,

Hey, thanks so much for taking the time out to answer my questions! Much appreciated.

First the bad news: It's not a dedicated theater room... Not even close. It's our drawing / living room, where I have STRICT instructions from the wife that this is NOT to look like a theater at all!

However, the good news: It's not a dedicated theater room... Not even close... It's our..... well, you get the picture.

I actually took this project up just as an experience thing, cause I'm seriously working on starting a side business for HT design... so it's a step in that direction. But that's a whole different forum post.

However, last night I did finally put all the speakers in place (yes, I have configured it for 7.1, and put nothing but a few rugs in a couple strategic places. Man oh man oh man! Does that room ever sound so good!

I'll be sure to post some pics, if there's any interest. I think that I'm well on my way to creating a living space, where the theater comes out ONLY when we want it. Quite excited about this project!

Thanks once again, Chris.

Fauzi

[RobP]

You know Fauzi, acoustic panels do not have to look like acoustic panels, a few years back I used to deal with a company named Breefus, they specialized in acoustic panels for large venue Cinemas that looked like large murals, each panel was designed to fit in the mural like pieces of a large puzzle, some stuck out from the wall further than others but when they were all put together they made for a wonderful looking wall.

[ThomasW]

First the bad news: It's not a dedicated theater room... Not even close. It's our drawing / living room, where I have STRICT instructions from the wife that this is NOT to look like a theater at all!

However, the good news: It's not a dedicated theater room... Not even close... It's our..... well, you get the picture.

Oriental rugs, curtains or other types of wall hangings...

[fauzigarib]

You know Fauzi, acoustic panels do not have to look like acoustic panels, a few years back I used to deal with a company named Breefus, they specialized in acoustic panels for large venue Cinemas that looked like large murals, each panel was designed to fit in the mural like pieces of a large puzzle, some stuck out from the wall further than others but when they were all put together they made for a wonderful looking wall.

Robert,

You're absolutely right... However, the unfortunate thing is that in Pakistan I'm very restricted as far as non-mainstream things go. It's a blessing enough that I can buy recognized brand name audio equipment here. However, anything esoteric enough such as acoustic panels... well, you'd be better off not pushing it!

Going to make do with rugs, etc... will be sure to post finished pics.

Thanks,

Fauzi

[aud19]

Good to hear your having some success Fauzi :T

[Kingdaddy]

Did you say Pakistan?

How about some of those fabulous Persian rugs hung around to absorb the highs, they should do nicely and you should be able to get them a lot cheaper then we could here.



Oops, looks like that was already mentioned.

[Chris D]

Yeah, I'd like to see pictures!

[fauzigarib]

Pictures...

Yeah, I'd like to see pictures!

Hey there,

You guys are amazing!!! I almost feel guilty when I think about how much help I get from this forum! And it's all (almost!) free! I say almost, because after logging off of here, I get this sudden urge to just pick up the B&W N801's that have my name written all over it! So I guess there really is no such thing as a free lunch!

Anyways... My room is currently under the phase where I'm hiding the cables through the walls / ceiling, and getting the projector mounted and all... I must say, it's turned out a ton better than I expected. It is still a little bright, but well under control now, thanks to ThomasW's "mirror trick!"

So, I'm figuring if I continue at this rate, I should have pictures for you guys by Wed or so...

Will certainly post them the minute things are presentable.

Thanks once again guys.

Fauzi