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

Yes. Even at $499 some of the suggestions here should provide increased depth and bass when properly positioned and setup.

Clearly the addition of a subwoofer/s can dramatically alter a systems presentation which might be described by some enthusiastic new sub owners as added clarity.

Keep in mind an investment in a higher quality subwoofer may service you for a lifetime despite all your other audio related upgrades. 

Good luck with it. 

@millercarbon: You have referenced Floyd Toole previously. If you look on page 154 of his book, "Sound Reproductions", you will see a chart of frequency by sound attribute (direction & space + timbre & sound quality).

100Hz looks like the lowest frequency for boundary effects and envelope.

My understanding of spatial cues is that it has more to do with the time domain (reflected sound) than the frequency domain. The pro audio guys on Gearslutz are maniacal about getting their ETC curves and sound models correct. (Good resource for this stuff.)

I think we all agree that deep bass improves the SQ.

A 0-180 degree control is NOT adequate.

It is with a Phase invert

millercarbon,

      I just recalled something about the Audio Kinesis Swarm and Debra that Duke knows more about than I do; there's something called 'bass room gain' that needs to be compensated for when setting up a distributed bass array system.  I believe it's a 3 dB increase in the volume of deep bass frequencies in typical rooms using subs that is the result of acoustic interactions in the room itself.  

     I know Duke somehow compensates for this so that the in-room bass response is flatter and more accurate but I'm not certain of exactly how he does this.  Hopefully, Duke is still following this thread and will respond.  If not, I suggest you pm him and ask.  

    Sorry I didn't recall this earlier but I think it's important for your custom DBA build.

Tim

Yeah that’s fine Tim I got it covered. Its called room reinforcement. Every room has it to some extent. 3 dB per octave is rule of thumb. But it varies.

The free Parts Express cabs are all sealed. Frequency response of a sealed enclosure drops off very gradually, which actually turns out fine because the drop off is pretty much offset by room reinforcement. But you never can be sure your room reinforcement will kick in just right to match your speaker roll off. They may roll off early. So what Duke suggested, and I of course did, is build 2 sealed and 2 ported.

This way if it turns out I need the extra extension I’ve got it covered with the ported subs. But if it turns out that’s too much then I can simply plug one or two, in effect turning them into sealed cabs with the earlier/slower roll-off.

Some of this I have known since it feels like forever- from having built a transmission line speaker in 1980, and a ported sub about 10 years later. But a lot of the details used here, the use of room reinforcement, the sealed/ported options, and especially the distributed bass array concept itself, for all of that I owe a huge debt of gratitude to Duke. When it gets into "exactly how he does this" its proprietary info but everything else he has been graciously willing to share. As exemplified in his posts here. I only wish more were able to get their minds around this revolutionary development in subwoofer technology.