Of Rooms and Acoustics….. Studiofoam/DIY acoustic panels.
Bet you’ve heard of it. Room acoustics.. I dare say the most overlooked aspect of audio reproduction. I don’t remember just when it got marginalized to the point of obscurity but there was a time when it was given as much weight as the gear sold. Proper or even marginally proper setup of audio gear plays a big role in getting the best playback possible. Soundstage, stereo separation, imaging will be to many something never experienced not because of the lack of appropriate gear but the improper setup of it. I know its clichéd, but if I only had a dollar every time… well, you get what I mean. Its only in the recent past that manufacturers of receivers have been incorporating some sort of room correction circuitry to correct for room acoustic.
Unless a room was treated acoustically or custom built, there is no such thing as a perfect room. Many times even a treated room is not much more than compromise, ridding it of its worst traits. Realize that speaker manufacturers go to extreme lengths to create products with near flat frequency responses . And with recent advances, the art of the craft has been largely replaced with the science of it, using computers and anechoic chambers to design with expected results speakers that flaunt exemplary specifications to within what its individual components are capable of. Well heres the thing, the frequency response of your room isn’t flat. Wondered why, that system sounded so much better when auditioned at the store… ? Now you know.
Many a time, rooms get damped adequately with the furniture that populates it. In fact, that stuffy old study lined with bookshelves, oversized couch and heavy drapes to keep the sun out… it’s a pretty good bet that its acoustically pretty decent. All is not lost though, googling room acoustics will bring up a plethora of information by those in the know and how to tame it. Many better stores dealing with higher end audio video equipment also provide services to provide acoustic room treatments. While many a time this can tantamount to overkill, theres really some basic things that can be easily done to tame a room without turning into it a recording studio or alienating the wife and family dog. Err, I say this as aesthetically speaking room acoustics treatments tend to be rather challenged. It truly wants its own way, which by the time you’re done will look like either a recording studio or a tiny opera house, both of which will be the subject to snickers at the office water cooler till kingdom comes.
Heres a good article detailing room acoustics: http://www.silcom.com/~aludwig/Room_acoustics.html, and another detailing speaker setup: http://www.gcaudio.com/resources/howtos/speakerplacement.html. its pretty heavy to digest but worth the read, and don’t be surprised if you end up with speakers in a completely unacceptable position like I did. That’s when compromises come into play. There was no way i could have left my main speakers in the “ideal” position. I ended up compromising with the side wall distances.
Reverb on the other hand is easier to tame. An excessively echo-y room is not a good thing and sound bounces all around before reaching your ears muddying it up and ruining the listening experience. Its easy to test for it actually.. just use the hand clap test. Standing in the room, give a resounding clap with your hands and listen for the echo. If you hear it echoing badly, that’s bad. Its not hard to discern. Clap in several rooms, at work, in a neighbors home… you’ll get it. Bass is by far harder to tame. To go about that using room treatments often results in big bulky absorbers in the corner and what have you… its my home, not a theater
In an excessively echo-y room, acoustic panels prevent the sound waves from bouncing back and forth between the walls by absorbing or breaking them up and reflecting them in different directions. These treatments are no more than panels with absorptive or refractive properties that are hung on walls like paintings. While effective, they are only work in the mid to upper frequencies. The thicker the panel the more effective it becomes in the lower frequencies. Providing some separation between the panel and the wall increases the effectiveness of the panel. Spacing them about 3-4 inches from the wall may very well be a good thing, but consider that with the air gap and the thickness of the panel, that’s about half a foot of room lost on each treated wall. In an already small room, it may not be the best idea as I found out. I ended up leaving about 3/4th an inch.
There’s also too much of a good thing and deadening the room too much simply doesn’t sound good. There’s plenty of calculators out there that estimate just how much damping is required but in my opinion, start with 3/4th of what it states and work your way up.
My new study is squarely square shaped.. unfortunately,… this is how I went about fixing it up. Using the clap test nearly brought me to tears… its was terrible to say the least. There was already a couch in there and fully carpeted with heavy pile carpeting. After mulling it over, I decided to tackle the slap echo/reverb with a combination of Studiofoam and DIY owens corning 703 acoustic panels. I had heard good things about Auralex’s Studiofoam while looking for solutions. Not the prettiest thing looking more like it belongs in a recording studio, but well regarded to get the job done. I got it from Amazon which had it for less than other retailers. Reviews of the product suggest not using the supplied glue and that’s exactly what I did. This was trial and error after all, and not wanting to bond the foam to the wall, I used DAP Seal n Peal which worked a treat. It did though, smell something fierce. While I didn’t mind it so much, the Mrs wasn’t pleased. But it did fortunately wear off in a couple of days. It comes in 1 foot by 1 foot squares and it what manner its applied isn’t as important as the quantity applied. You can get creative and come up with eye pleasing patterns. The glue takes a while to hold it in position, I had a devil of a time getting it to stay put. The pieces kept wanting to slide down the wall and ruin the seamless effect I was going for. I solved the problem by using a small finishing nails to anchor the pieces to the wall while the glue dried. After completing the back wall and letting it dry overnight, I again used the clap test to see what improvement this had gained.. if any.
It was remarkable. The echo had reduced dramatically.. and this was only with the back wall treated! A pitchy “zing” was still present but far less obnoxious than before.
For the front wall I decided to use Owens Corning 703 rigid fiberglass panel that I was going to fabricate myself. These panels aren’t terribly expensive to buy commercially but I had the rough material in ready supply and couldn’t pass up the chance to go the DIY route. Its easy enough to put together with just basic tools. This is whats needed (about 40$ in parts to make 6 2×2 panels or 3 2×4 panels):
– 3 inch x 1 inch lengths of wood from your friendly neighborhood home improvement store. Get the cheap ones. Its not really supporting any weight and its not going to be visible in any way. They come in lengths so all you need to do is cut them into the proper lengths using a saw.. a table saw is ideal but a handheld jigsaw or traditional handheld saw will work just fine.
– Owens corning 703 rigid fiberglass. They come in 2’ x 4’ bats that are 2 inches thick (skip the 1 inch thick bats). So making 2×4 or 2×2 is as simple as cutting it into half. A sharp utility knife makes easy work of it.
– Get a mask of some kind and dress for the occasion. Fiberglass particles are itchy as hell and I wouldn’t want to be inhaling the stuff.
– 2 inch wood screws.
– A heavy duty stapler to fix the fabric to the frame. If you dont already own one, dont bother getting one just for this project, small finishing nails would work just as well.
– Some reasonably nice looking fabric to cover it all up. It should be coarse to not reflect any sound and instead let it pass through freely for the fiberglass to trap and damp. Burlap works just fine but is not the nicest looking. Guilford of maine available here is highly recommended. I used some drape material from Joanns fabric. Looks much nicer than burlap and is coarse enough to easily pass the breath test. Breath test you ask? Oh yeah… if the weave is coarse enough, such as Burlap, blowing through it provides no resistance which is basically what you’re looking for.
So, don’t dwell too much on the material, if you can easily blow through it, it will work just fine. Fire retarding it may be a concern to some, there’s spray applications that do the job, although I didn’t really concern myself with it.
Now to put it all together. Cut the wood into the appropriate lengths. 2 lenghts of 2 feet and another 2 lenghts of 2 feet plus the exact thickness of the wood multiplied by two. The wood will never exactly be one inch thick even if it says so on the label.. go figure. Mine, although clearly states 1 inch, is 3/4th of an inch. Measure thrice, cut once. No reason to learn this the hard way, its true. Glue the pieces together then use the wood screws to fasten it tight. One at each corner is more than sufficient. If pictures are worth a thousand words, then the following will give me a break from the old carpal tunnel flaring up… here you go, step by step.
Now, what did all this do… a heck of a lot is what it did. The clap test results in a nicely damped room. Not all dead but just about right.. I tweaked the front wall with Studiofoam until i was satisfied with the clap test .
With a window on one side and storage on the other, i didnt really have first reflections to deal with that i could tell of. And as expected, what a huge difference all this makes. Its quite literally night and day! The room now passes the clap test resoundingly, pun wholly intended! Sound stage is broad and gone is the excessive reverb that muddied it all up so much. Imaging is spot on now.. vocals seem suspended and theres the sense of space, everythings larger than what it was before. Too much bare wall also exaggerates the middle to high frequencies.. all peakiness gone! If theres a serious bone in your body about listening to hi-fi, then this simply must be a part of the budget of the entire system. The mistake made by most is not accounting for the room. While treatment specifics vary from room to room, the principle still applies and theres always a way for it to be had affordably. The entire project cost me less than a hundred bucks and a weekend.. it would be the best hundred any hi-fi enthusiast could ever spend.