When does speaker distortion become audible?

Kijanki, thanks for your response. Of course, the Paradigm Studios 60s and Signatures 8s are very different speakers at very different price points. Nevertheless, I think technical specs can only take one so far. There's the "X-Factor" that counts for a lot as to whether a speaker sounds fair, good or great.

Then of course there's the equipment, especially the amp. I noticed a major improvement in sound, particularly bass, when I sprung this year for the ARC Ref 150. I suspect the sonic presentation improved in large part because the Ref 150's DF is almost twice that of my previous amp, the ARC VS-115 (14 versus 7, respectively). In addition, the power supply in the Ref 150 is triple that of the VS-115 -- 1040 joules versus 335 joules, respectively. ARC's sales literature puffery that the Ref 150 "will dominate" one's speakers may not be total hyperbole.

Regards, Bruce

About 10-20% becomes noticeable to most listeners. But for some rock music it is 20%+. Listeners of small combo or solo jazz and classical can be upset by 5% "noise". I fall into latter group. Pristine quality is very appreciated. AC power conditioning is essential for fussy ears.

Bruce, the worst part of Studio/60 was aluminum dome tweeter. I did try to replace it with Morel Supreme 110 but at the end I failed - it is not as easy as it sounds. Tweeter in Hyperions HPS-938 is so well integrated that you cannot practically tell when sound goes thru it. Fantastic highs with zero sibilants.

Ptss, 10-20% might be noticeable to most but it is also related to frequency. Bass distortions are not as audible as midrange distortions. People often select an amp with 0.01% distortion not realizing that it is most likely due to deep negative feedback at the expense of the sound, while speaker distortions go in many percents.

Kijanki, I recall reading that folks who owned the Signature 8s (v1) also complained about the so-called "Go-Pal" tweeter being harsh, hot and fatiguing. The Go-Pal used some type of gold/aluminum dome. The later version of the S8s (v2 and v3) use a beryllium dome tweeter, which is a very different beast. Much of the HF ringing was eliminated because the beryllium dome's HF resonant point is much higher than its Go-Pal predesessor.

Btw, the Home Theater HiFi link I provided to you above is to the bench test report of the S8 (v2). The test results are notable because the S8's measured distortion is less than 1 percent over most of the measured frequency response spectrum -- while the speaker is pushed to 100db of SPL. I don't know how that converts into input wattage, but does it mnatter?? Sustained listening at 100 db will rupture the organs in small animals and damage one's hearing.

BIF

At 20 Hz it was over 5% but according to this article:
http://www.bksv.com/doc/BO0385.pdf
it is harder to hear distortions below 400Hz. Single tone shows only THD but there are other distortions that might be more audible. Intermodulation, caused by nonlinear motion and membrane bending, produces new frequencies when speaker is driven by two frequencies.

According to this article: http://publications.lib.chalmers.se/records/fulltext/126969.pdf
THD testing does not reveal all nonlinearities of the speaker. Harmonic distortion will alter instruments' overtones adding coloration while intermodulation distortion will be much more audible.