I second the reco on the Yamaha pro amps, big power, low fan noise in stock config ...
But, if I were dabbling into the pro amp market these days, with an eye on dsp, I'd look seriously into what Crest is offering. Their new pro-lite series (whatever it's called) looks like the goods. Yeah, it's not US built like their good stuff, but their cred is solid, and if it says Crest, I'd bet it would pass the test. The real question would be their -3dB point.
btw, IMO, differences are often merely attributable to some non-linearity,maybe clipping onset. The peak demands are extraordinary when one examines the math.
10dB peak requires 10x power increase
20dB peak requires 100x
30dB peak requires 1000x
Quite the daunting task... hence the inherent level of capability oft associated with high sens/high power approaches. Dynamic material easily gobbles up amplifier headroom.
Here's Tom Danley on the subject;
I have to run in a little bit but saw the words “ go deaf” and such and thought it would be important to clarify a couple things on that subject.
I think I mentioned this stuff to Brandon and Josh a while back so I hope they aren’t bored hearing the explanation again haha.
In audio, there is an expression “headroom is your friend” and I guess that is part of the message. What loudspeakers do wrong or non-linearly changes with level and the amount of misbehavior increases more rapidly than the level of the desired signal as you increase the operating level.
Well before a speaker burns out, it is severely compromised in it’s performance.
With the heating of the voice coil, one finds the SPL decreases relative to the expected level with increasing power, also the systems tuning / frequency response changes at the same time, for the same reason.
For “modern” drivers, this “power compression” begins about 1/8 of the drivers rated power, if rated using the AES procedure.
Honestly there is so much BS regarding specs and such in commercial sound that to add a sense of “realism” or something to that mess, we have a 3rd party laboratory specify usable rated power. Hifi, don't get me started.
When driven with a slowly increasing drive level, when the speakers response departs by 3dB from the expected response based on the input power and 1W response, that is the maximum usable power.
If you examine the CLF file with the CLF viewer, that is the number shown there, as well as other parts of the speakers performance.
Anyway, what we associate with “loud” music is often at least in part or even largely due to the departure from linear the speaker is exhibiting when driven hard. We have learned what “loud” speakers sound like, only in part through the actual SPL.
For this reason, a very clean linear speaker producing music at the same measured SPL, may sound much less loud than another speaker that is straining.
We hear “loudness” in part through the spectrum we are exposed to, distortion itself is the production of “extra” harmonics not part of the music, “free energy” so to speak which occupies a larger spectrum than the original signal.
On the other hand we have sound pressure that you measure and here to the situation is less than ideally clear also.
In the old days of analogue tape it was critical to have a way to set the recording level.
This was done by a VU meter (Volume Unit), usually a meter movement with markings and a red “don’t go much past here” marks.
When done properly, this represented a realistic limit.
The funny thing is, what you measure depends on how long a time you examine.
If you use a fast reading sound level meter, you are integrating the SPL for some period of time and arrive at short time average SPL.
Set the meter to “slow” and obviously the meter moves a lot less and the peaks and dips are much smaller, integrated for a longer time. So, what we hear as loudness is also in part related to how long the sound is.
Most people think about loudness this way, what the sound level meter says.
Actually while useful measurements, these do not tell you what is really happening either if that is your interest.
If you take the microphone Voltage signal and it’s root sensitivity and you examine that signal on a storage oscilloscope, you can work backwards to the peak SPL, the actual loudness at that instant in time, NOT at all what it might sound like.
If you have a peak hold reading sound level meter (not common but I have one) you would find that in your home, you can produce very intense short sounds and very intense very low frequency sounds. I found that dropping a spoon on the floor could produce peak levels in the 130’s and sitting in car and closing the door produced a peak in the 140’s.
You never see anything like that with a normal Sound Level meter because these sounds are too short or low to sound “loud” or be indicated as significant.
Modern reproduction systems are not usually geared around the short term peak requirements but a slower lower average.
About 10 years ago, I was part of a ABX blind listening test comparing a number of Pro-sound amplifiers. I was using some early time coherent speakers I had designed for the company and as a sanity check, brought in two hifi amplifiers, one being a Threshold Stasis.
The amplifiers did not all sound the same, after searching recordings I found a couple parts where one could reliably hear differences, not in anything obvious BUT oddly in the decay parts of the sounds.
Anyway at a modest level (peaks about –15 –20dB on the Thresholds “fast” meter, it began to be “different” in a different way, it sounded slightly less dynamic.
I was very puzzled (it was my listening amp at home) and grabbed an oscilloscope and examined the outputs. Sure enough around the point it began to sound less dynamic, it had reached instantaneous clipping.
TO BE CLEAR this is nothing like “clipping” which everyone knows, this was ONLY detectable if one had a “without” version to compare to (in this case from a much larger amplifer).
By it self, it sounded fine, no problems and that “not hearing” the problem is exactly why most sound level meters and other volume level indicators do not show the peak requirements.
Anyway, my point (looking at the clock) it that to preserve or realistically reproduce sounds, you often need a far larger peak level than you would ever guess based on the ubiquitous Sound level meter. Of course all of this is irrelevant if your producing near steady tones, I am talking about dynamics.
You simply can’t produce short large peaks unless the system can produce them at all in the first place. Headroom is your friend.
This interest in making things sound real is also why I fiddle with recording too, recording with no compression. I have a pair of TH-50’s and SH-50s in my system with enough power to be somewhat embarrassed to mention and at a level that is still ‘not that loud”, I can reach instantaneous clipping with the fireworks recording.
I have not had a problem with any movie sound track however.
I am trying to decide if I am going to re-arrange everything so I can get these guys worked in and retire the TH-50’s.
I suspect I will have to listen to another round of my kids saying “DAAAAD are you playing that fireworks thing again!!!” But they love watching movies on it when the TH-50's were put in haha.
Got to run,