Grasshopper desperately seeking guru

I come seeking wisdom... Hello, and thanks for looking at my post. Gratitude to those contributing so much to a forum like this where hacks like me can learn from some truly experienced acousticians. As a new member ( I introduced myself yesterday( http://www.johnlsayers.com/phpBB2/viewtopic.php?t=8300 ) I am trying to target a 159 hz peak that has really put the yang in my ying. My humble studio certainly doesn't have the "shock and awe" visual appeal like studio pics I see here and functionally I am having some issues with its acoustics. In this control room, I dont record much besides lead vocals and acoustic guitar; my tracking room (aka family room) handles the loud stuff and leakage has not been an issue for me. I've been mixing in here for years and realize now would be a good time to get off my ### and grapple with the acoustics. I have been trying my best to be scientific: listening to sweeped tones and measuring pink noise and such. As it stands, the rta agrees with my ears: a response peak (9db or more) at 159 hz is is what has been smearing my bass mixing. This is the gremlin I'm looking to eliminate. Here is where I stick my neck out; my floor plan below reveals a lot of mistakes I'm sure you can point out. I'm hoping for suggestions/ideas that don't involve a bulldozer. Following is a floor plan labeled with materials present: And the room dimensions on the mode calculator: It looks like I should have a problem at 72-74 hz but I think the 703 damped thin paneling of the rear wall is trapping that very well (contact mic seems to indicate 69 hz resonant peak of paneling). Also, it looks like my problem freq. should be 172-174 yet its definitely 159hz. additional modal problems around 212-260 are fairly tamed by the current absorbers. I"ve tried several changes of mix position using the info available here and ; no luck. I removed the paneling on the instrument closet, revealing the 703 layer inside and no change. My thought is to just add Helmholtz absorbers but I have no Idea how much area or best placement to be effective, or, if this is even the best course. Anyways if you could look it over you could be my guru . please, ask for info If I have omitted something critical: it's a lot of data, I know.....

Thought I should add some additional info in the form of closeups. This is the reason I refer to myself as a hack. I take some sound principles like oc703 absorption and low mass damped panels for trapping and kinda throw it all together as best as I can figure it out. Remember I did all of this back in 1997 when info wasn't so ubiquitous. I could rebuild the ceiling cloud with a limp panel or slats if that would yield good results.

possibly you already answered this: does this happen with all your audio monitors or just a particular pair? is it possible your monitors are the cause? I ran a room simulation in CARA based on your room and as much of the construction and treatments as I could add, and I don't see the 159hz as a problem even when I shift speakers and listening position around (which goes to show that simulations only get you so far as opposed to measurements...) this doesn't mean that something in the room isn't causing the 159hz to be elevated but usually you'd expect to see it in only a few places in the room - especially a mostly square room - due to modes - so either something is causing a resonance at that frequency (maybe some hollow cavity is reinforcing it? maybe the desk is creating a resonant chamber? the panel behind the drums?) or I'm thinking the speakers (or something in the amplification chain) is causing it.

Thanks for the Ideas ! I will address what I've done in these areas. I will also look for ways to test those suspects further. As far as the speakers go, they are Mackie HR824s which have a nice tight passive radiator ported bass end . I've tested the monitors with all three bass switch settings : open space, half space, and corner space. I've put them on alternate speaker stands and tried different heights. Doesn't seem to be the culprit. Still, I should take the speakers into another room and test them -- good thought ! I think searching for resonance is a good idea. the entire rear wall is thin paneling with 703 behind it. Im not sure how tight the contact is between the 703 and the paneling. Does it matter alot for damping ?? Some of the cavities are a bit open due to the pocket doors. The hollow core pocket doors have been gutted and filled with 703. Walking around and tapping on the paneling I only found one that made a substantial tone. I pulled off that one(the closet paneled wall) and it didn't affect the 159 hz . In order to test these paneled areas for resonance I attached a frap (flat response audio pickup) and measured pink noise. the peak always seem to come at 69 hz . I slid the pocket doors open and measured the pink noise in the room and saw no change in the 159 hz peak. I hope these tests were valid ?? I wonder if drilling some 5mm holes in my rear wall would randomize their tuning some. there is no panel behind the drums. Is the parquet floored section of the floor looking like a wall to you? there is a 2x2 cabinet that sits on top of an mdf set of drawers, so I will check out that cabinet for resonances. as far as the amplification chain, it is pretty simple: DAW to rme FF800 and addl. outboard converters. from there to one of two different mixers. I have swapped out both the converters and the mixers. from there it is straight to the powered mackies. The mixer sits on a table not much bigger than the mixer itself and the rest of the mix station is on tubular aluminum supports; not much of a cavitiy is presented for a resonance to develop. I'm drilling a pattern of holes in that closet paneled wall and turning that into a 3 1/2 " sealed Helmholz using the formula I got here. http://www.mhsoft.nl/helmholtzabsorber.asp I'll post how that affects things when I get it assembled. Matt

there appears to be an indent on the side you label with the drums. wasn't sure what that was. yea, trying the speakers in another room and seeing if you run into the same problem is a good idea.

Oh Yeah, that indent is my attempt at making my 3x6 window appear on the sketch. Same as on wall by monitors and smaller window opposite drums. Matt