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Bass Traps and acoustic panels


GC456

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How important are they, I was thinking about getting 4 2'x2' foam panels and bass traps for the corners of the room.

I am having a hard time finding any useful info on the net, what are the best and most effective types?

If you have them please let me know if they are worth the money. What did you install, how effective were they.

Thanks

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You are asking a tough question, but you are on the right track.

You need to determine what the problems are first and then plan your attack.

Room treatment is certainly a good idea. There is quite a bit of info over at Audio Asylum (along with quite a bit of voodoo). This should get you started.

You are trying to achieve two inter-related goals. The first is to tame room modes (resonances) so the frequency response (of the speaker/room considered as a system) is somewhat uniform. At low frequencies, this is not trivial. The second is to tame excessive reverberation time. Again, at low frequencies this is not trivial.

Individual treatments have (one of) three goals: absorb the sound; reflect the sound; or diffuse the sound.

With that in mind, I would suggest doing some research (and there is much info on the Web) ahead of time. Hopefully, you could do some measurements of the room also. This may be a bit more than you bargained for; however, the treatments can be expensive. So a focused approach will be ultimately economical. But the good news is that this approach will have a significant impact on the sound, much more than many of the other things that people do to their setups.

There are also issues of "deadening" the sound to make your listening environment quiet, but that is another topic

Good Luck,

-Tom

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Thank you for the info.

After doing a few hours of research I think I might start with the following:

Bass Traps : http://truesoundcontrol.com/products/MTRLEN8.html

Foam Panels : http://www.truesoundcontrol.com/products/SFLAT8.html

I might even go with some smaller 1'x1' foam panels for the smaller areas.

After all this reading and even some R&D in my HT, I never realized

how much eco my room produces. I really think these things will help me

out quite a bit.

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Well here's some great starter info and you'll come across a lot of new terminology that you can google and find more info:

http://www.ethanwiner.com/acoustics.html

It's a long read, but that probably sounds like a good thing.

As far as an actual product to go with I would highly recommend looking into foambymail:

http://www.foambymail.com/Products.html

It's factory direct of the same foam products you'll find

elsewhere...definetly the best bang for the buck I've come across so

far. (It's identical to the stuff auralex is using).

Btw, pictures and diagrams work wonders on our ability to help you

more. Also, keep in mind that too much acoustical "treatment" can be a

bad thing too (often times worse than the starting point).

Hope this helps.

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Yea, I've read that link before on another forum.

Unfortunately......My idea of doing home improvements, is running the

sweeper. I dont mind hanging things on the walls providing it

doesnt require much work, or cost much money:/

The DIY projects arent something I'd do, and I'm too cheap to pay someone $1,000s to do it for me....LOL

Im screwed...

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Dr who,

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after reading Ethan Winers column and looking at the real data for his real acoustic panels, I am surprised that anyone would consider foam for the narrow frequencies that it attenuates[H]

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Well I don't exactly consider 250Hz to 4kHz+ very narrow band (that's over 4 octaves). [;)] And I don't consider acoustical foam the only treatment necessary to fully treat a room (which is what I think you're getting at). But when it's so cheap and easy to work with, I see no reason not to do as much treatment as possible with foam. At the higher frequencies these panels are probably not absorbing anymore, but then you can take advantage of the shape of the panel that will act as diffusion (effectively accomplishing the same thing).

We can talk theory all day long...but I'll just revert to all the well treated acoustically spaces I've been in...which typically use foam on the side walls - skyline RPG diffusors on the cieling - bass traps in the corners - or sometimes helmholtz resonators positioned strategically throughout the room. Anyways, the point being that there is no one single solution that will address all the acoustical issues in a room.

Also, the true goal of acoustical treatment isn't so much a flat frequency response, but rather a flat time response. You want the RT60 (time for a sound source to decay to 60dB) to be the same throughout every frequency. In fact, if you acccomplish this goal then you'll find the modal effect of the room on the frequency response isn't a huge issue anymore. I forget the ideal RT60 to shoot for though...I wanna say around 350ms? It is slightly music dependant...and you might even consider a different RT60 for different frequencies too. But that all comes down to the subjective aspects (artistic side) of acoustics.

So what the heck does that mean? Well it means you shouldn't use too much absorbtion because you will quickly make your room dead sounding. Reflections are good, too many are bad and too few is awful (think anechoic chamber...if you've never been in one, then I highly recommend taking the next opportunity that comes by). If you want to get rid of a reflection without affecting the decay as much as absorbtion, then think diffusion - redirect the sound instead of getting rid of it.

Since most people want to do things by ear, I would start with bass traps in the corner because they will have an effect on all frequencies...not just the low end. And then I would add foam to the walls - addressing early side reflection points first. I would then add foam elsewhere in the room that is aesthetically pleasing until the room starts to sound too dead. At which point I would remove about 10% of it and then throw RPG diffusors on the cieling. If it's still too dead, then I would try replacing some of the foam with curved masonite panels (try not to touch the early reflection point treatments). Add one treatment at a time (maintaining symmetry) and listen for a long time before adding the next treatment. Get an idea for the change the treatment made so that later on you have an idea of what treatments to remove/change after the fact.

If you want to actually measure everything, then for about $300 ($50 mic, $50 mixer, $200 ETF software) and a computer you would have everything necessary to measure accurately the changes your treatments are making. And with a little intuition you can get a pretty good idea of what you need to do before you start adding treatment (which can be very helpful in the purchasing process).

I am a fan of both methods, but with measuring you at least know when you have arrived at the ideal - when you should shift your attention to other areas of the system.

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Many good points here on the subject. If you are into reading about these issues, I would recommend two books. First, "The Master Handbook of Acoustics" by F. Alton Everest. This is to me, the most complete book on understanding what you are trying to do, and includes ideas on how to make your own if you so choose. The other is "The Complete Guide to High-End Audio" by Robert Harley...this is more of a layman's guide, but does touch on the basics.

I just finished installing some mid to hi frequency absorbers I made in my HT room. I will post pictures below. These are installed in the "reflection" points along the side walls. I could easily tell that I had resonance problems by just clapping my hands and listening to the continuing echo of the sound. I also have some DIY bass tube traps in the back of the room for low requencies. I still have a little work to do, but am thus far very pleased with the results. I made the panel absorbers with the Armstrong "420" ceiling panels you can get at any Home Depot. I used two panels for each absorber and covered them with speaker cloth. They look good and work very well. I obtained the acoustic tests on these panels from Armstrong and would be glad to send you the results if you are interested.

post-10337-13819284134594_thumb.jpg

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Another view:

My plans also include adding some heavy courtains around and below the screen. This will deaden the room somewhat. Other than that, I would like to add a few more panels to the ceiling reflection points and feel that should get the room right where I want it.

There are a few programs and .xl spreadsheets that will give you an idea of your problem areas based solely on room dimensions. However, you then have to consider room construction materials, carpeting or bare floors, windows, furnishings etc.

post-10337-13819284144794_thumb.jpg

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Radio Shack SPL meter, inaccurate by 2dB

At what frequency? That meter is +-6dB throughout the entire audible range. I have written a spreadsheet that you just enter the raw SPL readings from your RS meter and it automatically applies the correction and creates a graph of the frequency response. I think it's more fun to play with than beneficial, but I am willing to email it to anyone interested (just PM your email address). This topic has come up a few times lately too (outside of the forum) and I remember reading about a $10 mod to the meter that results in a flat frequency response...so I'll have to see if I can't dig up that website again.

The problem is that no RTA or SPL meter will give you information in the time domain....Acoustical problems exist in the time domain so you're wasting your time playing with the frequency domain. In fact, the speaker manufacturer already took care of the frequency response for you. [;)]

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I recommend that you go to www.avsforum.com and hang around the Setup and Theory subforum for a while. They also have a Design and Construction subforum that has a wealth of data too.

www.audioholics.com has some good information too, especially for the DIYer .

There's a free analysis program in the Setup and Theory subforum. I have not used it yet. I am going to hire an acoustic engineer to evaluate my room acoustics.

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I just wanted to thank everyone for the info and links. I

recieved my foam on Friday from foam by mail, and I finished putting it

up yesterday.

I used 8 bass trap, and 2" foam. My room is just under 800 square

feet (excluding the carpeted floor) and I now have 100 square feet of

foam for a total of 12.5% coverage.

What a huge diffrence this has made, much more than I thought was

possible. The ecos have been reduced approx 80%, and I placed

about 1/3 of the pieces in the reflection spots. My sub woofer

is now very clean sounding, and has more punch. I am going to order a

little bit more for the room and the long hallway leading to my

HT.

It is amazing that $250 of foam made my many thousands of dollars

system sound so much better! If you haven't done this yet I

highly recomend it! [:D]

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Great news on the improvement. It is interesting how much $250 & a bit of knowledge can get you in terms of better sound. It is unfortunate that so many people would spend that same money on "audio voodoo" and simply be out of $250 and have no real change in the sound.

Good luck,

-Tom

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