you have heard this tired song before from me I guess...
Hey WW, tasted SET and want to try the real hard drugs now huh?
Well, I guess you already know what my opinion is here as we discussed this at length when I visited and it looks like I’m pretty much in agreement with Mikebake. Good, big woofers done right (no small feat!) will get you part the way there but I really think when you hear the dynamics and presentation of a good high efficiency, probably at least partially horn loaded system with SET’s you’ll want to go all the way, but I hear yah, 1 step at a time.
On your MTM’s – hey, you love them so why dick with em? I’m not familiar with the details of this design but I suspect a lot of development went into getting that crossover just right and it probably goes way beyond simply picking a cross point and slope which is about all you can easily do with in an active crossover. Add to that that unless you spend big money on a tube unit, you are putting solid scrape op amps between your SET and those speakers you love – personally, no thanks. There may be some real advantages to rolling off low bass to the MTM’s though (I remember how those little cones danced!) so a crossover down low to big woofers might be a good thing. Actually, I’d want to try a crossover scheme like the Dahlquist design ProAc suggested – active SS high order (18db) lowpass rolloff on the big woofers and shallower (6db) passive line-level highpass crossovers to your MTM’s – just a cap in the signal path. I’m not a subwoofer fan 95% of the time but the best bi-amp integration I ever heard (aside from Edgar’s Titan system) was Dahlquist DQ-10’s with this type of crossover and Dahlquist woofers (not “subwoofers”). This would also give you the ability to keep your system’s strength’s in tact (tube pre, SET amp to your MTM’s) while using SS where it really shines – low bass.
On woofers and cabinets - I’d rule out real horns (I mean real ones) for deep bass unless you are willing to put something the size of a large refrigerator in your room. I know people will say there are small ones that work but there is no cheating physics – to get horn loaded bass down into the 30’s you need a huge mouth (even in a corner) and a long horn path length – read BIG. Maybe I’ll find I’m wrong about this someday but I sure haven’t heard any horns smaller than a large appliance that pulls this off yet. 2 bass horns that I have heard and liked which you could build are the Edgar seismic and the Labhorn but I think when you comprehend the size of these things you will run away very fast.
My preference for woofers (if I can’t have a real horn) are large format (15”) “pro” market parts with powerful motors, light paper pulp cones, cloth surrounds, highish Fs, low Qt, high efficiency – yes, Altec, JBL, TAD type stuff. These won’t go real deep and usually have to go in large vented cabinets but you end up with a high efficiency woofer (not subwoofer) that has fast, dynamic bass that can sound like the real thing. Nice starting point too if you decide to try horns for the rest of the range. The spec sheets say you can have lower bass with smaller cones flopping around in little boxes but I gave up on listening to spec sheets - the large pro type stuff just sounds more like music to me.
All just my opinion of coarse (hey, you asked
).