Will a subwoofer add depth and clarity to my system, or just bass?

Vtvmtodvm wrote:

"The "distributed array" concept is worthy with one notable exception: It generally (?) recommends leaving the main speakers Unfiltered."

Whether or not filtering the main speakers is desirable depends on the specifics of the situation. The same is true with ANY subwoofer system.

The amplifier included with the Swarm and DEBRA systems has a fixed 80 Hz 2nd order line-level highpass filter built in, so the option is always there.

If there’s a worthwhile benefit to the main speakers from using it, then by all means use it! If not, then why not leave it out of the signal path?

Duke

designer of the Swarm

"To OPTIMALLY separate the (low bass) subwoofer passband from the (mid-bass) main woofer passband, it’s necessary to use a full 4th order (24dB/octave) active Linkwitz-Riley crossover."

How do you know? Are you taking into account the rolloff inherent in the main speakers, and its accompanying phase shift? If so, what frequency and what slope is it? How much phase shift does it contribute? Well the answer is... IT DEPENDS!

The real world is far more complicated than your "one size fits all" claim implies. 

I certainly do not agree with your claim that a 4th order LR crossover is "necessary".

And out in the real world, my second order highpass + the speaker’s inherent rolloff will usually (but not always) come closer to a 4th order acoustic slope than what you are suggesting (4th order highpass + the speaker’s inherent rolloff).

"A simple (generally passive) 2nd order (12dB/octave) crossover is simply not sufficient; the overlap is excessive."

If there does happen to be some overlap, you have more than enough adjustability in the amp’s lowpass filter section to deal with it: Phase, frequency, gain, and if necessary a parametric EQ. Low-frequency speaker systems in rooms are minimum-phase systems, which means that once you get the amplitude response right, the time-domain response is also right. And the amp has the tools needed to do that in the crossover region.

"Is a 12dB/octave crossover better than nothing? Well, probably; but why compromise unless there’s a cost-related cause."

Yes in the Swarm I’m trying to keep bang-for-the-buck fairly high. There is always some improvement that can be made for more money, so these sorts of things are judgment calls. I don’t think it would be a wise investment for me to have custom subwoofer amps made, but if I did, I’d look into parts quality in the highpass section before I opted for a steeper slope (or ideally, a variable slope).

Nobody is obligated to buy the subwoofer amp that I offer. Anyone can buy just the subs and provide their own amplifier and filtering.

Duke

Jnorris2005 wrote:  "One thing to be aware of is that the sub will not add clarity to the main speakers unless the sub or the preamp provides a high pass filter to them, blocking out the bass that is now to be handled by the sub. Otherwise you're just adding murk to the low end."

That is certainly a very reasonable statement, but I don't think it's an absolute truth, logical as it may be.  In my experience it is possible to clean up the bottom end with subs even without a highpass filter in series with the main speakers, and depending on the specifics of the situation, that may even be preferable.  I can cite examples if you would like. 

"Also, if your room is small, chances are you don't need a subwoofer at all. The addition of one will muddy up the sound and probably activate room nodes that will devastate the imaging and sound balance of your speakers."

Agreed!  The smaller the room, the worse it is from a bass mode standpoint.  Chances are a single subwoofer in a small room will sound boomy, tubby, and bloomy, unless you turn its level down very far below the level of your main speakers. 

That being said, imo there is hope for good quality deep bass even in a small room.  This is somewhat counter-intuitive, but smaller the room, the more it benefits from the modal smoothing effect of using a whole bunch of intelligently-distributed bass sources.   

Duke