Bass management questions: DIY subs, pro amps, HT, music

[HeatMiser]

Thanks to the wealth of information on this forum, I have been introduced to the benefits of using pro sound reinforcement amps (as opposed to plate amps) to drive DIY subwoofers. This solution would seem to demand a certain level of flexibility in the receiver/processor's bass management system that unfortunately isn't always there - especially if one wishes to use the sub for both HT and stereo music with a minimum of fiddling.

The main issue as I see it is that many HT front ends seem to do one of the following, depending on how they are set up:

- route only the LFE signal to the sub (fine for HT, useless for stereo music since there is no dedicated LFE channel in stereo)
- route the LFE + the full-range L/R to the sub (works for HT and music, but presumes the presence of a low-pass filter on the sub since it will be seeing a full range signal - therefore it won't work with a sub driven by a full range pro amplifier)

Now I have to think that the people using subs with pro amplifiers must be in one of the following situations:

- own front end electronics with more comprehensive bass management options, with the option to route not only LFE and LFE+L/R, but also LFE + a low-passed L/R signal with adjustable crossover frequency etc.
- use an outboard crossover
- don't feel a sub is necessary for their music listening, or don't listen to music on their systems

So all this leads to my question: what are you folks (you know who you are ) doing? What front end electronics offer the flexibility I have in mind? Are there certain brands of processors that do this better than others, or are there any resources available to help me make an informed decision when it comes to buying a new front end?

Any input would be appreciated.

Moderators, I apologize if this seems better suited to the HT/front-end subforum, but I feel my question is really only relevant to people who have built their own subs with pro amps to power them.

[Dennis H]

99% of the receivers these days have a 12 db/octave filter on the sats and and a 24dB filter on the sub for any channels set to small. It works best with sealed sat enclosures that give a 12dB rolloff. The natural 12dB rolloff of the box plus the 12dB electrical filter give a 24dB combined rolloff to match the sub.

[HeatMiser]

Thanks Dennis. Is my resistance to using the "small" setting with large full-range main speakers misguided? In my perfect fantasy world, I would wish (when listening to music) for my subwoofer to supplement the bass produced by my mains, in order to compensate for the ever-present issues of room placement and such, rather than choosing to not have my mains produce any low bass at all.

[Dennis H]

Is my resistance to using the "small" setting with large full-range main speakers misguided?

Probably. Taking the low bass load off the speakers makes them play much cleaner. In this forum, full-range means your mains will produce enough low bass so no sub is needed. Very few speakers qualify. Say, if each speaker can put out as much bass as a pair of SVS subs, then you could set it to large. Otherwise it's small. Chris and Brian's 3-way, each speaker with two 10" woofers, is optimum for small setting and XO frequency of 50 Hz.

[HeatMiser]

Probably. Taking the low bass load off the speakers makes them play much cleaner. In this forum, full-range means your mains will produce enough low bass so no sub is needed. Very few speakers qualify. Say, if each speaker can put out as much bass as a pair of SVS subs, then you could set it to large. Otherwise it's small. Chris and Brian's 3-way, each speaker with two 10" woofers, is optimum for small setting and XO frequency of 50 Hz.

Well that actually makes sense; it seems I have been laboring under a misconception (based I suppose on experience with older/cheaper receivers) that the majority of HT receivers have a non-adjustable crossover point set at 80 Hz that comes into play along with the "small" setting, and a more desirable (lower) cutoff would only become available with "large" settings, and only in receivers that feature a greater number of options in that area.

Embarassingly, this thread turns out to have little to do with DIY after all. Thanks for taking the time.