Why do subs sound bloated or slow?


The use of subs in 2 channel audio is controversial around A’gon. Detractors argue that subs usually make a system sound bloated or slow.

IME, the two biggest challenges for integrating a sub into a 2 channel system are optimizing frequency response and optimizing transient response. When frequency response isn’t flat, the bass sounds bloated. When transient response isn’t time aligned, the bass sounds slow.

Here is my pet theory about why systems that use subs often sound bloated or slow: Under many circumstances, optimizing frequency response and optimizing transient response is a zero sum game. In other words, getting one right usually means you get the other wrong.

Thoughts?

Bryon
bryoncunningham

Showing 2 responses by bifwynne

I agree with Plato. I also run two channel fronts and I have a Paradigm Signature Servo subwoofer. This Paradigm sub has its own Class D amp to power the woofer and three controls knobs to control phase, cut-off and loudness.

Because I only have one sub, I also bought a Paradigm X-30 crossover unit. The X-30 has the same controls and also allows me to combine left and right channels without shorting my pre-amp Mains. I feed my main fronts off the preamp's Main 1 output to the power amp. I run my fronts straight out. I feed the X-30 off of the pre amp's Main 2. output As stated, I use the X-30 to combine the two channels into one channel for the subwoofer.

My front speakers are Paradigm Signature 8 v2. The fronts roll off at roughy 35-40HZ. Of course room placement also affects base contour. However, as a general matter, I cross the sub over at 40-50HZ. Based on my ear, that sounds about right. Too high a cross-over and the bass sounds boomy. Too low, and bass is thin.

I also adjust phase by ear. I listen for the best sounding bass response. Loudness often varies by source material, but as I got used to working with the sub controls, I don't move the adjustment controls around too much.

I understand that Paradigm's current subwoofer line-up offers a bass adjustment kit which uses a small mike to sample bass contour, phase and loudness information directly into the woofer's self contained power amp. The sub's amp does all the work and makes the necessary adjsutments. That's about as good as it gets.

Anyway, I hope this helps. For those of you whose subwoofer doesn't allow cross over, phase and loudness adjustments, I suggest buying a cross over control box like the Paradigm X-30. It really works. BIF
Marty and CBW: Interesting posts. On Jan 23rd, I mentioned above:

"I . . . run two channel fronts and I have a Paradigm Signature Servo subwoofer. This Paradigm sub has its own Class D amp to power the woofer and three controls knobs to control phase, cut-off and loudness.

Because I only have one sub, I also bought a Paradigm X-30 crossover unit. The X-30 has the same controls and also allows me to combine left and right channels without shorting my pre-amp Mains. I feed my main fronts off the preamp's Main 1 output to the power amp. I run my fronts straight out. I feed the X-30 off of the pre amp's Main 2. output As stated, I use the X-30 to combine the two channels into one channel for the subwoofer.

My front speakers are Paradigm Signature 8 v2. The fronts roll off at roughy 35-40HZ. Of course room placement also affects base contour. However, as a general matter, I cross the sub over at 40-50HZ. Based on my ear, that sounds about right. Too high a cross-over and the bass sounds boomy. Too low, and bass is thin.

I also adjust phase by ear. I listen for the best sounding bass response. Loudness often varies by source material, but as I got used to working with the sub controls, I don't move the adjustment controls around too much."

Does this sound like a reasonable approach to adjusting the subwoofer? Also, as mentioned, I can adjust phase from 0 to 180 degrees. My sub is placed about 6 inches behind the fronts. For some reason, it seems like a 40 60 degree phase adjsutment sounds best to my ear.

Would you guys explain the relationship of (a) phase degree adjustments (i.e., 0 to 180 degree) to (b) coplanar placement and (c) time coherence??? My sense is that in a perfect world, if the sub and mains are placed equidistant on a fron plane with the mains from the listener, there is no need for a phase adjustment. However, if the sub is moved forward or behind the mains, or placed along a different wall, then a phase adjustment is needed.

One other complication: As stated, I can adjust phase, cut-off and loudness from BOTH the sub and the X-30 control box. Because it is more convenient to use the X-30 control box, I set the sub controls at zero degrees for phase; 3/4 gain for loudness; and 180 HZ (max) for crossover cut-off. However, as stated, I use the X-30 box to control the foregoing adjustments. Phase: 30-40 degrees; Crossver 35-40 HZ; Loudness -- whatever sounds about right, less is generally more. Does this approach make sense to you??

Thanks for your advice. BIF