Originally Posted by RMK!
^^^ "self-noise" ... I love the little pearls that are dispensed here at the science forum.
What exactly do you find objectionable about the term "self-noise"? Some amps are inherently noisy. Only someone utterly without experience would deny that! If an amp makes a "fuzz" kind of sound with speakers connected but no source, that's its self-noise.
It's useful for someone with an analytic mind to distinguish between noise from the amp (self-noise) and noise passed down the chain because of problems such as poorly optimized gain structure. For someone who just like to look at big gear, it doesn't matter.
Originally Posted by coolgeek
"I can't imagine why anyone would need anything more than the cheapest AVR offers, power-wise, for such efficient speakers in a domestic living room. (For that point fleshed out more generally, see here and to some degree here.)"
Not to say I disagree... but read this from another member. It does make a lot of sense (perhaps SPL is not the only variable here):
One word: transients!
Two words: maximum level.
Modern audio systems set an absolute ceiling
on the signal level. That level is 0dBFS from the digital source. Literally nothing can be encoded louder than 0dBFS. So one can know with certainty exactly what the maximum peaks of any given recording will be by finding the peak level (-xdBFS) of that recording. When people listen at "cinema reference," the absolute maximum possible level of any transient signal
is 105dB in the main channels and 115dB in the LFE channel. Likewise, if one is listening through calibrated gear, then -10dB on the volume knob means 95dB max mains peaks and 105dB max LFE peaks. If one's speakers are 95dB/W/m sensitive, then in a huge and fairly absorbent room one might need 16dBW to hit those peaks at the listening position. (The numbers that people often quote, from calculator's like Crown's
are only valid outdoors or in anechoic chambers. But most people, sadly, don't think enough to realize that.)
What is 16dBW? A massive 40W.
And that's peak power, so we're actually talking about a 20-30W power requirement.
FWIW, I once did a level-matched listening test between my old Meridian 551 integrated amp (~60W/ch/8Ω) and my old Adcom GFA-5800 (>300W/ch/8Ω), powered from the 551's preouts, driving two Tannoy System 12DMTII's (96dB/W/m). With levels matched (using a voltmeter and a 0dBFS 1kHz sine wave on the outputs), there was no absolutely no difference in perceived dynamics (or anything else) on material like Shostakovich 7 at front-center hall levels. Everyone should do a test like that (with proper level matching, otherwise it's just a waste of time; most people are too sloppy or lazy to actually think through the test and realize that without level matching it is a test completely without merit). It's one thing to intellectually understand reality. It's quite another to experience it oneself and have those nagging doubts fully excised from one's mind.
Where power is actually needed is in the subwoofers, because small cabinets asked to go low are very inefficient. (An I-B type install doesn't need much power to get loud. Most people think they "need" lots of power for I-B's simply because they've set their gain structure poorly. And, to be sure, with a lot of power one needn't spend much time optimizing gain structure on subs in very large "cabinets." Power is cheap, and with lots of power comes big fudge factor in that regard.)