Low frequency acoustics

Tweakers' Asylum

Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ.

I'm absolutly not happy with my system's low freq performance. This is my setup:
B&W Dm604 speakers with the low pass filter for the woofers and the hipass filter for the midtoner removed.
dbx 223XL active x-over set @ 120Hz
Crest Vs1500 poweramp for low freqs
Crest Vs1100 poweramp for mid/high freqs
Behringer UltraCurve EQ
The problem is i have a 6 dB penalty in output under the 50Hz, that i can live with. But output in the 50-100 region is very troublesome. I only have output very near to the speakers, or in the left back of my room for the right speaker. And in the right back for the left speaker. There are some places where low freq output is better, but on those places stereo imaging is too much affected by reflections, and solving that would require too much places to be fitted with absorbers. My hot spot is in the exact middle of my room, but there's of course the least bass output.
Here you can see a meassurement with ETF, meassured with a Behringer mic (the one that goes with the UC):
http://aphrodite.tweakers.net/~crew/Jag/Zooi/EQlow.jpg
The blue line represents the raw response, the green line the EQ-corrected response. Apart from the terrible EQ-setting needed to correct these problems, it still doesn't sound well. Besides, this is the best speaker, left performs even less (which is caused by the room, not the speaker, i already switched them).
A part of the problem is caused by a EAW hornloaded sub lying behind the speakers (removing those gave a somewhat smoother response). But my guess is that most of it is caused by standing waves. I only have two parrallel walls, the side walls. Dimensions are (LxW) 7m x 4m (or 23 feet x 13 feet). Height varies from 0 to 3.5m (12 feet). The highest part of the ceiling lies in the middle of the room.
What are my options to solve this? I'm planning on buying a big couch, would that help much?
Here a picture of a 604 with the EAW sub on the background:
http://aphrodite.tweakers.net/~crew/Jag/Foto's/EAW604got.jpg
And the two 604's with subs behind them:
http://aphrodite.tweakers.net/~crew/Jag/Foto's/Kamergot.jpg
Amp rack shot from above:
http://aphrodite.tweakers.net/~crew/Jag/Foto's/Racktopgot.jpg
The two 19-inch racks:
http://aphrodite.tweakers.net/~crew/Jag/Foto's/Rackgot.jpg
I also have a nasty ringing to the sound in the low freqs, probably caused by resonances. Here's a waterfall plot which shows resonances around 30, 100 and 150Hz:
http://aphrodite.tweakers.net/~crew/Jag/Zooi/Resonanties.jpg
I'm planning on upgrading speakers to 803 or 805 with DIY subs. And a BSS fds 366 unit as EQ, x-over, phase corrector and DAC (in which case the UC would leave my rack :)). But before i go into that adventure, i would like to reduce these acoustical problems to reasonable levels :).
One final note: in contrary to what my system suggests (the high power amps, the hornloaded subs (which i only use for movies)), i'm not a bass freak :). I just like to combine best of both worlds (pro and HiFi).

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Topic - Low frequency acoustics - Jag 20:02:43 03/19/02 (13)

Different approach - Double Trouble 14:18:35 03/21/02 (1)

Re: Different approach - Jag 16:21:58 03/21/02 (0)

Re: Low frequency acoustics - dlarkin_dc 10:13:27 03/21/02 (6)

Re: Low frequency acoustics - Jag 16:17:16 03/21/02 (5)

Patchwork quilts are an American tradition! - dlarkin_dc 04:37:52 03/22/02 (4)

Re: Patchwork quilts are an American tradition! - Jag 04:35:43 03/23/02 (3)

Re: Patchwork quilts are an American tradition! - dlarkin_dc 05:38:47 03/25/02 (2)

Re: Patchwork quilts are an American tradition! - Jag 07:54:38 03/28/02 (1)

Re: Patchwork quilts are an American tradition! - dlarkin_dc 08:28:02 03/28/02 (0)

Position - Owen 02:36:24 03/20/02 (3)

Re: Position - Jag 11:29:04 03/20/02 (2)

Forgetting.. - Owen 02:08:48 03/22/02 (1)

Re: Forgetting.. - Jag 05:00:03 03/23/02 (0)

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