Broadband Absorber plans?

Hey all, I have scoured the forum for an answer to my first 2 questions, but couldnt find the exact answer i was looking for (i suspect due to the search feature not about to search for an exact string - unless im using it wrong) I have 12 pieces of 2" plain OC703 (2' x 4') and want to make some broadband absorbers to hang on the walls of the studio. My questions are: 1. Can one construct broadband absorbers to be High Frequency absorbing and others to be low frequency absorbing, or is the broadband absorber a "one fits all" situation, covering high to low frequencies? 2. Can someone point me in the right direction for plans for simple portable absorbers (ones i would build and hang on the wall as opposed to actually afixing to the wall (something different from panel traps?) 3. How would i treat the two rooms below considering my 12 pieces of OC703 and desire to trap all nasty freqencies from highs to lows? (the ceiling is very low - about 6' 3") Forget about the minitraps that are drawn in there already - i was going to buy some realtraps, but now am under the impression that i can build something about as good with wood, material and OC703. thanks!! :-)

1. Can one construct broadband absorbers to be High Frequency absorbing and others to be low frequency absorbing, or is the broadband absorber a "one fits all" situation, covering high to low frequencies? All thicknesses of 703 will absorb highs, it's more a matter of how LOW they go. The lowest frequency absorbed is a function of how far from the wall the FACE of the absorbent is, and the DEGREE of absorption is a function of the THICKNESS of the absorbent. So, if you use 2" 703 against the wall it will absorb less low frequency than if you place that SAME piece of 703 2" or 4" AWAY from the wall - Optimum absorption, considering ONLY direct 90 degree incidence, occurs at 1/4 wavelength of a particular frequency away from the wall; realistically though, few sounds hit the wall at 90 degrees so there is more effective thickness of absorbent at work here. The general rule of thumb that seems to work in most cases is, place your absorbent at least as far from the wall as the thickness of the absorbent. Since you're looking for EVEN absorption, there is usually little purpose in going for just "high frequency" absorption; you get enough of that in most cases just with furniture, people, carpet, cloth covers, etc. 2. Can someone point me in the right direction for plans for simple portable absorbers (ones i would build and hang on the wall as opposed to actually afixing to the wall (something different from panel traps?) http://www.johnlsayers.com/phpBB2/viewtopic.php?t=659 Also, check the Studios Under Construction pages, accessed thru the John Sayers Productions logo at the top of the page. 3. How would i treat the two rooms below considering my 12 pieces of OC703 and desire to trap all nasty freqencies from highs to lows? (the ceiling is very low - about 6' 3") Your slot resonators in the drawing would take most of that; 12 pieces = 96 sq ft, and you need 703 behind all the slat area. In addition, everywhere you show commercial traps should have at LEAST 2", preferably 4" 703 (you can double the stuff if 2" is all that's available) - in addition, the splayed walls will control flutter echo but will NOT give you reflection-free monitoring - you would need to use the "mirror trick" to find first reflection points from each speaker to your head, and treat those with more 2" 703. First reflections also come off the ceiling, so more 2" 703 up there, centered halfway between speakers and your head; Hopefully you can get more of the 703, the 12 pieces you have will be a good start though... Steve

Thanks Steve - great info. The page you sent me to for the plans didnt really have what i was looking for - it did link me to johns small room absorber page and i guess i could build a portable version of the rear wall absorber (just not as thick). It does also seem to me now that i could just take a piece or 2 (thick) of the OC703 and and attach it to a light timber frame, cover it with some material that breathes and then hang it (+ others) at different distances away from the wall. - Bass traps up behind the speakers, more low/mid on the sides and and more mid traps up the back? does that sound about right? both front and back of the absorber would be open right - meaning dont attach it to a board. Ill draw some pics of what im thinking and well see if i am on the right track Will look into the mirror trick thanks -Pete

Yeah, Pete, you've got the right idea; I did a "concept" drawing a while back that might work for you - http://www.johnlsayers.com/phpBB2/viewtopic.php?p=15642 It's about 2/3 of the way down on this thread... Steve