Boomy bass in home theater room


I have a Martin Logan/Adcom home theater system in a 14' square room (concrete floor (no basement) with typical wood stud/drywall construction). I'm using a single, Infinity 12", 300 watt (RMS) subwoofer. The room is treated with 24, 2'x2' (3" thick) acoustic foam in various wall locations. The bass is boomy, especially in the mid-bass region. I can't change the room. When you get done laughing, care to offer some realistic suggesstions?
ivory1
Yep, no way around things (practicality wise, that is), other than radical "EQ'ing", speaker and seating placment changes (still have challenges thereafter), or, yep, massive bass traps/resonators, etc. Your most pracctical is to move speakers/seats, or (from what you're stating), using some Parametric EQ'ing for your system. At the price of your best option is to "EQ" the sub (fix the 40hz spot), and make sure it's not in the 80hz "hole at the 1/4 points of the room. Basically, you need to place the sub in the "middle" of the room to rid the 40hz peak from the sub/room interaction, which might not be practical. Otherwise, place it in the middle of the front wall behind your center speaker to help minimize the 40hz peak(by putting it in the null there!). Also, sitting in the middle of the room, side to side, will lessen that 40hz mode. Still, 80hz will be peaking there, but you can work that somewhat with crossover/rolloff of sub at 80hz, as well as coupling with Logans rolled off at 80hz a bit, if not perfect, but workable. (and you should be rolling the logans off at 80hz!!!!("small" on the pre/pro, yes!). Running em full range has set backs, espeically in that small room, not to mention dynamic range limitations.(Use THX guidelines).
Best bet is still to add some Parametric EQ to at least the sub ideally(but workable otherwise, as well as check level of sub balance vs. system), and get sub out of corner, and into middle of room more!.
You indeed should do bass traps in teh corners to help remove the sting there, and help room sound. Also, you might be doign a bit too much absorbtion. Try pannels on the sides, a few maybe upfront(although Logans don't like absorbtion behind their speakers so much, so beware!). Really, that small rooms needs some more "diffusion"! Particularly since the Logans severely limit off axis reflections greatly, by their phaae canceling dipolar design! I've sold Logans for years.
Basically, your problems can be tamed GREATLY, by moving the sub into the middle distance/dimmension (if not middle of the room more), adjusting levels/crossover, tweaking, speaker and seating placment (moving speakers near 1/4 points would help 80hz peak (how high is ceiling though?), and/or sitting closer to 1/4 point between/from the front/back wall), and fidgiting with set up. OTher than that, EQing should be considered.
For the record, the Rives Parc is the most transparent Parametric Analog device you'll find for doing speakers, but you'll pay a lot to do all of them with your system price range!...otherwise, concentrate on the sub/levels/eeating...you have no other options really
Dipole bass helps tremendously - perception seems to be driven by more than just steady state response. Unfortunately, most of the Martin Logans cross to monopole bass drivers by the time they reach 200-300Hz. You can do that down through the second octave using a speaker like the Linkwitz Orion or Audio Artistry Dvorak/Beethoven. You could also build dipole bass units for your martin-logans.

You'll need a box sub-woofer to reach home theater output levels in the last octave; parametric EQ (the Behringer Feedback Destroyer pro is cheap and fine in that frequency range) helps some there.

If you stick with the box bass, you'll need to use a steep cross-over slope to the sub or equalize everything - with an 80Hz 2nd order high-pass behavior my box main speaker bass hadn't rolled off enough for me to get more than 1dB of difference on big 40-80Hz bass peaks just equalizing the sub.
Pick up an old ashly analog parametric.They are very user frienly.This will remove the bass bumps.Digital parametrics are difficult for the beginners.Get yourself a test disc and a ratshack SPL meter.Put the sub where it sounds best and go from there.Good luck!