Adding a center channel sub-woofer?

[Firedome]

My Scott 222D had provisions for 2 speaker sets, A & B. My Klipsch KSB 3.1s are great all -round speakers, but with only 8" woofers iirc,the deep bass could be better, though they do amazingly well for what they are, thanks to modern speaker technology, quite amazing.

A friend has 2 15" Magnavox woofers with big-ass magnets that would make a killer subwoofer in the right size ported cabinet... could one add such a sub-woofer by just running the 2 "B" speaker outputs with L & R wires to each separate 15" woofer? Would I need to have some kind of crossover to cut out frequencies over, say, 500 Hz or just let'er rip as is?

[TC Chris]

Your plan should work even without a low-pass crossover because the speaker will physically eliminate the highs via its natural rolloff. My question would be one of balance--relative speaker efficiency. Klipsch speakers are usually high efficiency, so the bass from the additions could be relatively weak. Or if the new speakers are MORE efficient, you'd have to tame them. Seems to me I've read that series resistance added tends to reduce damping factor and give you a flabby bass.

But what the heck, you won't know if you don't try it, and if you've got the parts, why not try?

Chris Campbell

[Firedome]

Ya I figured you could just hook it up w/o crossover, but wanted to ask.
The Klipsch KSBs I got new in 2000 are pretty efficient at 96dB/W/m, the woofer is paired with a Tractix horn/driver in a small-ish ported cab as you'd expect with Klipsch. They work fabulously with the pp 6BQ5 Scott.

The sub thing is sort of a mental exercise as I doubt something big enough to hold 2 x 15" woofers would ever actually be allowed in the LR, not to mention they wouldn't fit there well anyhow. What could work is some kind of small acoustic suspension sub perhaps. It'd be fun to pair something like that with a mono tube amp, I don't care for those self-powered subs that most seem to be out there. Not sure if a small AS non-powered sub even exists though.

[Firedome]

Guess my main concern is that if no low-pass filter is used with a 15" woofer, the output, whatever it is, without a cut-off above a certain Hz could be more distorted or undesirable than those frequencies from the other (Klipsch) speakers and interfere with the overall sound? How do I know at what Hz would a specific 15" woofer typically begins an audible drop-off and where would one draw the line? I may be wrong but it seems to me above some critical Hz the woofer output would be undesirable and should be filtered out, but I have no frequency curves or specs for it. Maybe instead for a center channel I should just get a single classic acoustic suspension job known for excellent bass response like an AR-3 as it would also have (relatively) undistorted output up to 15kHz+ and could complement the small Klipsch KSBs. Those are really sweet sounding with 6BQ5 amps and super clean from, say, 60 Hz to 20K, but lacking in true deep/tight bass below that.

[TC Chris]

But the AR-3 is much less sensitive and will be driven to lower levels than the efficient Klipsches. I'd hook up the 15"and just see how it sounds. The ears are the best test.

Chris Campbell

[Firedome]

I probably will experiment, but the idea of a cabinet with 2 x 15" woofers is out, it just won't fit. I gave the woofers to a guy I know in town some years ago and I know he's never used them, but even with just one it'd be too big, I have about 18" to play with between cabinets. An AR-3 will fit, Dad had them, but would need more power, even Dad's Fisher receiver was hard pressed. I know a guy in VT with AR2ax-s and they are also excellent bass performers bass, but I don't know if they're any more efficient, and I don't want to buy 2 of them, or another amp. At the moment all this is just a thought experiment anyway, gives me something to think and ask questions about. In any event any solution will have to require minimal expenditure according to SWMBO... I just got some "feedback" for buying a used 5AR4 tube! lol

[Firedome]

Well looks like I've solved the center channel speaker problem, thanks to Dave MM! He has an ADS L780 which will fit perfectly in the "gap" I have between cabinets, then I can use my 2 smaller ADS L10 (single dome tweeter and 6" woofer) as the side speakers. Those were originally designed to be satellite speakers but work great as the stereo spkrs right now in my office. I bought them in '80 as sattelites for my pr of L-710s. The L-10s had their dome tweeters re-built last year by John Yee in CA, a retired ADS guy. So all the sound would be quite coherent as the L780 has more bass, bigger woofer, and is 3-way, with the same smaller tweeters plus a dome midrange. ADS built all their own drivers and the liquid ferro-magnetic fluid in them give their dome tweeters + mids give them incredibly smooth and clean highs. I had the L-710s back in the day and should never have parted with them. Thanks to Dave this has the potential to be a really well balanced and excellent sounding system for our smallish living room!