Absorption Panels for my Setup

[SteveCallas]

Menards was having a buy one get one half off sale on some 8.5" thick Johns Manville fiberglass insulation rolls, so I decided it was time to add some absorption pannels to my room. I went with hardboard backing, no side support, and resin bonded polyester batting over the exterior. I have six 4' x 2' pannels done right now and may make four 2' x 2' pannels depending on whether or not these do anything noticable. I have one behind each main, one at each reflection point of the mains on each sidewall, one at the reflection point of he center speaker on one side wall, and one on an open space of wall behind me and to my left. The smaller ones would go on the ceiling and on the wall behind my ears if I decide to make them. I also put a 40" tall, 20" thick roll of the polyester batting in an open corner to act as a bass trap - I may unroll it, make it thinner, and make it floor to ceiling.

I'll try to get some music listening in tonight and see what I find, but I'm thinking it's going to be subtle at best.

[Sonnie]

Before and after REW measurements would be interesting.

[Blueeyedfrog]

So this material you brought is the fluffy stuff that goes in ceilings or walls? Do you have a photo or two? Also, I presume that the panels are primarily to absorb mid-to-high frequencies? What is "resin bonded polyester batting "? (Excuse my ignorance).

Cheers,
Blue

[SteveCallas]

I didn't take any photos during construction, but you can see two of the pannels in this photo - one behind each speaker.



But yeah, it's the fluffy fiberglass insulation that is used in walls, ceilings, etc. Based on other absoprtion pannels that I have read about people building, 8.5" thick seems to be quite thick, which is a good thing, so that's why I decided to jump on that sale. The thicker the insulation, the lower in frequency you should be able to absorb, so it becomes a more versatile absorption pannel.

The resin bonded polyester fabric is similar to regular poly batting you would find at a fabric sore or Walmart except that the individual fibers are held together to create a fabric by using resin instead of needling or low melt fibers. In other words, regular poly batting can be pulled apart very easily, isn't very dense, and is fluffy - this resin bonded poly fabric is much stronger, firmer, and not as compressable, though it is still very porous. I like it because I don't really need to go out and get any fabric to cover the pannels with - it's strong enough to use by itself, it won't shed, and it's already white to match my walls.......and best of all, I can get all I need for free

[bpape]

Just be careful Steve. In a corner or on the rear wall, I'd agree 100% with the nice thick deep absorbing panels. Behind a speaker which is dealing primarily with SBIR issues, you may not WANT the absorbers to go that low. Your SBIR issues may shelf off higher in frequency and you can actually cause anomolies by absorbing too low in this particular implementation.

Bryan

[titch--]

I have some superchunks not to far from my mains and I found that they sucked up alot of my mid range.

So what I did for now was I just put some cardboard in front if it and you could hear a big difference in the mids.

cheers

[SteveCallas]

bpape wrote:

Just be careful Steve. In a corner or on the rear wall, I'd agree 100% with the nice thick deep absorbing panels. Behind a speaker which is dealing primarily with SBIR issues, you may not WANT the absorbers to go that low. Your SBIR issues may shelf off higher in frequency and you can actually cause anomolies by absorbing too low in this particular implementation.

Bryan

Thanks for the comment Bryan, I am new to this absorption stuff. I just read your general acoustics terms thread on SBIR, and I take it that you are saying there is the potential for the response of my speakers to now seem a little rolled off in the lower mids/upper bass frequencies? Interesting. I still haven't gotten a chance to do any critical listening with music since the pannels were put in place, any free time has been spent on tv throughout the week. I'll do some music listening and then also try some measurements with the pannels and without them to make sure nothing detrimental is happening. Thanks for the heads up.

Again, I haven't done any listening or measurements yet, but what are your thoughts on the big roll of polyester fabric in the corner, ~20" thick and ~40" tall? Since it's not floor to ceiling, any potential for it to do much of anything?

[SteveCallas]

Did some listening for the past hour and half with no pannels, all pannels including the ones behind each main, and pannels except for the ones behind each main. I can't really percieve any difference in mids or bass with or without the pannels behind the mains - I guess I'll wait and see what the measurements show in that respect. I can percieve a focusing of sound with the absorption pannels as opposed to without them - without them, the sound is a bit more diffuse. It's not earth shattering, but it is noticable, and I find it beneficial. It is most noticable when parts of music are concentrated only on one speaker. I will go ahead and make the other 4 pannels for the wall behind me and maybe a couple on the ceiling.