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In Reply to: RE: Max. listening level ... have I hit a ceiling... (long) posted by bjh on May 28, 2007 at 18:43:32
HiIt is very hard to tell “over the phone” what it is exactly but there are only a few possibilities.
Short term clipping appears to be inaudible unless you can compare to “with and without” where the unclipped sounds slightly more dynamic.
Longer term clipping (normally Voltage swing limiting within the amplifier) shows up as flat tops on the largest waveshapes. Being longer in time, these can sound like a click or a pop associated with transients. Gross clipping makes a raspy buzz etc.
Amplifiers can also current limit from an excess of current and / or load phase angle which is in the “Verboten” zone. This limiting is unpredictable; some popular early SS amplifiers actually went into HF oscillation when V/I limiting engaged (circuits based on the old RCA SS book, I’m looking at you).Your best bet determining where you are is to get an old oscilloscope, figure out how it works (easy) and then look at the voltage coming out of your power amp.
Lastly, if your speakers really are 84dB 1W 1M, then you may well be running them out of gas. ALL voice coil drivers begin to depart form “linear” at about 1/10 of their rated power. In the 1980’s Doug Button (JBL) presented a paper at AES showing that as power capacity’s continue to climb, that the effects of power compression would eventually reach the point where an increase in input power actually resulted in a reduction of output sound level.
This kind of dynamic compression is driver dependent, the woofer, mid and tweeter all have different time constants so this is usually a case where by it self it is not very noticeable but is audible when you can compare with and without.
For the woofer though, VC heating can be related as the driver T&S parameters change wildly. Alternately, plain old over excursion can result in the VC former bottoming out.
This is usually a loud crack sound that gets your attention.
If you smack the coil too many times, it will be damaged.Also, keep in mind the Radio shack meter on “fast” is not displaying peaks but rather is integrating over some (unspecified) time period.
Lets say your listening distance is only –6 dB down by distance from 1 meter and reach peaks of 96dB so at 1 meter its 102 dB peak (RS). Lets say the real peaks were only 6 dB greater than the RS meter so one needs 108 dB at 1 meter. With no power compression and 84dB sensitivity, it takes 250 Watts (+24dB over 1 Watt).
Your probably out of Gas.
Best,Tom Danley
Edits: 05/29/07Follow Ups:
This could explain why many believe low-power/high-efficiency is the way to go.....
Actually it explains why those who want their reproduction system to get a little closer to sounding like the real thing, would want high power and medium to high efficiency. But not at the expense of large amplitude variation, as is so often the case.
Here's a stereo based on that premise rather than the audiophile belief system Todd. Quite different from anything you will ever have.
cheers,
AJ
The threshold for disproving something is higher than the threshold for saying it, which is a recipe for the accumulation of bullshit - Softky
Heard an all TAD driven horn speaker in Munich driven by KR audio Kronzilla DX monoblocks (100 watt parallel SETs). Great sound but with the wrong amps those microscopes, er I mean speakers, could get brutal.
MC - Great sound but with the wrong amps those microscopes, er I mean speakers, could get brutal.
And for this you would blame the loudspeakers, rather than the recording and/or ancillary equipment?
Don't GE's like to brag about "resolution" and how when blind tests fail its because of not enough system "resolution" and such? Hmmmm.
cheers,
AJ
The threshold for disproving something is higher than the threshold for saying it, which is a recipe for the accumulation of bullshit - Softky
"And for this you would blame the loudspeakers, rather than the recording and/or ancillary equipment?"
Moron, I am talking about the recording and/or ancillary equipment. When the speaker is good enough it is a window to what the rest of the system is doing. Clear enough for you. Try reading correctly next time.
And what speakers are used for blind test of amps and such?? How do we know they are sufficiently resolving?
The top-quality transducers, materials, system matching, exacting specifications, and painstaking measurements and optimization.....
With asynchronous sample-rate conversion and digital amplification......
BUT.....
As long as he enjoys it, that's the bottom line.
TK - With asynchronous sample-rate conversion
Audible threshold data where? Please do point me to it.
A 0.5% concern in the 5%? Maybe. Like wires. Possible audio difference. Sure. Maybe. Magnitude? Hmmmm.
Now what about the 95%? You think a blind test would be needed to differentiate between (any of) your speakers and those? How do you think your entire system would fare against that one? What about when live instruments were thrown in? Like a 4pc acoustic jazz band. How do you think your/his vs live would pan out for a panel of listeners? Care to guess :-)?
TK - and digital amplification
You know whats weird is that if you read the "Digital amp" forums, one finds a large # of tube converts. Probably much more than folks who prefer plain ol' SS. I put little weight into such anecdotal evidence, but a pattern does seem to emerge. I think we have a bit of a convert here in Al.
Of course, I have not heard Bouskas system or yours (though I've heard your VonS model [in a different room] and others.....y-a-w-n..zzzzzz), so I might be speculating purely on measurements, which of course are absolutely useless.
cheers,
AJ
The threshold for disproving something is higher than the threshold for saying it, which is a recipe for the accumulation of bullshit - Softky
TS - Lastly, if your speakers really are 84dB 1W 1M
Actually the article states 84db w/ a 2.83V input. It's clearly not an 8ohm speaker.
I agree with you on the power compression, worse on most home type drivers. I suspect a full 6db of diffraction loss compensation in the filter, hence what should be about 90db sensitivity tweeters and mids being lowered to match the baffle step of the woofer.
Any decent pro amp would drive these into smoking confetti, you know, like a QSC. But of course, the price is too low and chassis not pretty, leading to glare, grain and other such mind effects. Not to mention poor street cred with the audiophile buddies...
cheers,
AJ
The threshold for disproving something is higher than the threshold for saying it, which is a recipe for the accumulation of bullshit - Softky
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