I guess I've always accepted the oft-mentioned statement "You need a more powerful amp to get these speakers to
really open up", when looking at some of the high-end loudspeakers from Aerial, Salk, and Thiel. The companies themselves usually recommend pretty high Power Requirements in their specs: 100 to 600 watts, 50 to 350 watts, etc.
But when a salesman claims that "...buying these speakers is a waste of money unless you also get the matching Krell amp", I gotta wonder why (since this is the same guy that says I also need the "matching" $1200 cables)?
Crown has an interesting little calculator on their site (
www.crownaudio.com/apps_htm/designtools/elect-pwr-req.htm)
for determining Amplifier Power Requirements when plugging in the following variables:
Listener Distance from source
Desired SPL Level at Listener Distance
Loudspeaker Sensitivity Rating
Amplifier Headroom
So... If I plug in my figures - about 15' (4.5M) distance, 85dB, sensitivity rating of 92dB (Pinnacle's), and 6dB headroom (out-of-a-hat figure), I get -
Required Amplifier Power = 16 Watts
If I change the sensitivity figure to 86dB for the Aerial 7B, I get -
Required Amplifier Power = 64 Watts
OK, this supports the "more power needed" theory (especially if the Distance and SPL numbers are increased - if I went to 18' I'd need 96 watts with the Aerials), but the Salk Veracity and Thiel CS3.7's have higher sensitivity figures, but still recommend more power (Thiel - 90dB - recommends 100 to 600 watts).
Dumb questions time (sorry it took so long
) :
1. Are there other variables involved that the Crown formula doesn't address? It looks like Sensitivity is the only speaker variable driving the formula. Am I over-simplifying the power-to-SPL requirements of the Aerials? (For example, might power requirement differentials exist between the drivers...that is, do bass/larger drivers require exponentially more power/headroom than the tweeters to match spls?)
2. If I turn my 130 wpc receiver up enough to get 85dB out of the Aerials @ 15', is that the same as turning the 250 wpc Krell down to get 85dB? Obviously the Krell has a lot more headroom, but do I need it in my 15' room?
3. If 85dB in a 15' room (or 64 watts) is not enough to get the Aerials to perform properly ("open up"), do I need a bigger room / turn them up? How ‘bout the more sensitive Thiels? - I’ve heard the same comments regarding them requiring more power to perform well, but if 25 watts will get me 85dB, won’t my 130 wpc receiver still have plenty of headroom?
I've seen parts of this answered elsewhere, but sometimes I didn't completely understand the concepts - for example: I didn't really get what is meant when a speaker sounds "strained" due to lack of headroom. The fault wasn't in the reply, but in my own lack of experience. So, thanks in advance for any help in clearing my cobwebs
.