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In the Forum: Playback Listening
In the Thread: “Harmonic Speed”- friend of foe?
Post Subject: Speed, control and SET harmonicsPosted by Paul S on: 3/19/2008
I also find SET bass to be the overall best I have heard - at its best, and this has been, as you observe, when the amp is well within its comfort zone. And this seems to remain true even when Z out and speaker load "matching" are hardly taken into account.
Up to now, I have thought that the "best" SET used no NFB, and until I get a chance to compare under controlled conditions I still can't say if this is or is not the case; and maybe it isn't possible to say except in the case of the "optimized" situation. Of course, the ML2s use feedback, at least a comparitor in the PS circuit, yet these amps deliver the goods harmonically, including excellent low level harmonic and ambience cues.
Another thing that appears to be topsy-turvy is that the BR bins, setting aside their problems for a moment, deliver their best in terms of harmonic and ambience cues right about the point when the other "areas" of bass reproduction also sound optimised, and this is with the vent open, according to its LEAP design, meaning the woofer is mostly undamped and the Q is left to rip. This design seems to be most "alive" with the vent at the point where one can "almost" but not quite hear that obnoxious rush thing. So of course thisa is how I tune it, regardless of how what it means in terms of Q, Fs or Z/load.
These bins are tuned about 3/4 octave above Fs, and the impedance spike is about 1 1/2 octaves above Fs. I'm sure there are other electrical issues preventing me from hearing it, but so far I don't hear anything I can relate to the amp Z out and driver Fs except the "better" bass being from the 16 Ohm taps.
Of course I am not jumping to any conclusions about any of this, and I still wonder if the "harmonic speed" issue as it relates to bass is just as much a matter of very specific driver implementation as it is speaker topology. Yes, BR has all the often-discussed problems; but one reason I gave up on sealed was the fact that I just could not get decent harmonics out of it, and also there seemed to be a need for EQ/boost with any amps I tried.
The most common bass "solution" I have seen/heard has been to use SET for mid-bass on up and boosted SS below, perhaps even a plate amp. But I have never heard this done right, or rather I have never heard anything in the way of decent harmonics or decent ambience from this sort of set-up. So, here is a case where there is "plenty of power" and "plenty of damping", and even "plenty of bass' , but it sounds "empty" even as it is obviously "dense". No "content"?
Sure, there is more to bass than filling the room with LF, and maybe the transformer is the key, so NFB SET could do it. I have never gone whole hog on a specialized LF transformer, so I can't say. So far, my own idea from my own limited experience has always been that the answer was more power, other factors being equal.
Best regards,
Paul S
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