High Sensitvity = good transient response ?

Sean, they don't give the details on the website, other than it is a line with "valves" to control air flow. That sounds like what you are talking about with the stuffing. I've never experimented with something like that before. It seems like an interesting concept, but I don't know how well it would work.

"valves" to control air flow? Sounds like the the old Proacs(?) with straws stuffed in the ports (semi ports or multi ports or semi passive radiators?).

Learn something new everyday. And I thought that the covering on Brentworth's opening was the driver. I have only heard 2 SET as dealers don't carry this stuff. Sam Tellig talked with Mike Sanders re Quicksilver Mini Monos / March 2001. Page 36 I quote:
"The distortion is so high with Single-ended that when you put negative feedback around it, you get distortion of distortion. . . The distortion is multiplied so the amplifier sounds worse"
"The annoying thing is the higher distortion, because you don't get the distortion cancellation that you do with push pull. . . So you can't get rid of the distortion of single-ended with feedback: after a while, that distortion just eats away at you".
This is about all I know about SET.
I've only been in this hobby 1 year. Sometimes I think I should've gotten another boom box :)
Went to 2 live shows last month and the musicians and singer were playing through mics / amplifiers / speakers and even though their systems really did have a lot of distortion compared to audiophile stuff somehow it was better. Seemed like that "immediacy" thing people talk about with SET. So I'm interested in SET stuff.

Aperiodic designs seek to combine the damping of sealed speakers with the efficiency and extension of ported speakers. You pick up bass extension and efficiency due to making use of the backwave from the driver ( like a vent ) but the impedance remains low ( typically even lower ) at resonance like a sealed design. The high impedance peak of a vented design is part of what contributes to the "bloated" or "uncontrolled" low end response that lacks definition.

While it sounds like a phenomenal trade-off ( best of both worlds type of situation ), aperiodics ( also called "vario-vents" by Dynaudio and some DIYer's ) don't sound like either design. How such a design would work in combination with a TL is anybody's guess. Obviously, one would have to listed and see if it was their cup of tea. Sean
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I am assuming that was Sam Tellig that you quoted. First, he is making a totally "out-of-hand" statement, based on the measurements of a single ended tube amp design. This is obvious, as he refers to "adding negative feedback" as some kind of fix for distortion. It was known more than 25 years ago that negative feedback is NOT a fix for distortion in a real world environment, but only on the steady-tone measurement bench. No really good single ended tube designs that I am aware of, use any negative feedback in the circuit. Their "measured" distortion shows up as higher than SS on the bench, but not in the listening room. It is really sad that a person that writes for an audiophile publication is so ignorant and misinformed. Perhaps now you see why some of us have such little respect for the reviewers in the audio rags. Not all single ended tube designs are great, or even good. But the good ones are capable of doing the job as well or better than any amp out there. No audiophile in his right mind would spend $10k on a single ended tube amp that had so much distortion, that he couldn't listen to it, and no company would expect to sell such an amp. In fact, there are a good number of "hardcore" audiophiles that wouldn't use anything but a single ended tube amp, because they feel that only SET is capable of meeting their stringent sonic requirements. To sum up, a SET does not have higher "real world" distortion, and may actually have less than other amps, measurements notwithstanding.