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How to control long decay of B&W woofers ?

I have B&W Matrix 800 speakers (3-way system) with two 12" woofers per side. Currently the speakers are actively bi-amped between the woofers and the midrange modules using active crossover. A pair of KRELL FPB 350MC are directly connected to the woofers without the passive filters. The bass output is extremely good, deep and very tight. But some times I notice that on some drum beats the woofers don't stop as it should be, instead the woofers continue to make sound till the next drum beat. The long decay time of the woofers (some times) makes a kind of continuous background sound from the woofers and the sound becomes muddy. On many other recordings, the drum beats stop and start very accurately and the sound is very clean and crispy.

I am wondering what is the reason of this long woofer decay time (with some recordings) and how can I achieve a clean sound from the woofers ? I have tried the amps with damping factor upto 10,000, and the result is the same. Any suggestions from experienced inmates ?
Best regards,
Sunny
topmostaudio
topmostaudio OP
28 posts
 
Hi Newbee, that is an excellent point. I was also thinking on the same line what you have just pointed out. Otherwise there is no explanation. I was very much puzzled by this observation. I tried so many different ways to make the sound clean but failed. I changed amps, changed crossover charactersitics, added subsonic filters, but nothing made the sound any better.

I highly doubt that it is the room problem. Because I can feel and hear (by standing near to the woofers) that the woofers are still vibrating and producing sound long after the drum beat was hit. I believe that the symptom of the room problem is that you can hear the sound due to room reverberation (by standing waves) after the speakers have already stopped producing any sound. Am I wrong or correct ?

Probably I have to test those CDs on another system to know if it is the problem of the recording or not.
Thanks for your thoughts.
sunny
johnnyb53
3,510 posts
 
I agree with Newbee. It's gotta be the recordings. The fact that some recordings sound very controlled and tight means that it's not the speaker because it's proved that it's capable of stopping when "told" to.

Remember: When the B&W Matrixes came out, they immediately became the monitors of choice at Abbey Road Studios and also at Telarc; no doubt they found their way into several other studios as well. The thing is, the B&W Matrix was immediately received as a new standard in playback accuracy.

So I'd say if you're getting excessive bass overhang on some recordings and not on others ... it's the recording.
flrnlamb
508 posts
 
yeah...if the woofer is still moving,it's on the recording.
drrdiamond
671 posts
 
My set up is the same as yours, I think. I do use the Krell KBX that was set up by Krell especially for the 800's and includes the bass alignment filter. Unfortunately, they no longer make the unit and I don't think they will make the board (but you can ask them, if you find a used unit).

I have had no such problem.

Fell free to contact me directly if you have any further questions.

Richard
RxDentist@aol.com
drrdiamond
671 posts
 
2nd thought:

Did you change the polarity of the woofers when you removed the low pass filters? You should have.

Richard
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