Posted by Duke on August 22, 2003 at 09:52:55:
In Reply to: A-3 in Hong Kong posted by Kenny on August 21, 2003 at 21:56:17:
Hello Kenny,
It is quite possible that the Sound Labs are 10 dB less sensitive than your Apogees. I don't know which Apogee model you have and I'm not familiar with the specs of the different models, but I do recall that the Scintilla could be wired as either a 1-ohm or 4-ohm load.
With those big, beefy Accuphase amps, suppose you have the Scintillas wired for 1 ohm. Suppose the Sound Labs are nominally 8 ohms, and that both speakers have an efficiency of 82 dB for a 1 watt input at 1 meter (the "88 dB equivalent" spec given by Sound Lab is, in my opinion, overly optimistic). The sensitivity of the Apogees will be much higher even though the efficiencies are the same, because sensitivity is measured with respect to volts, not watts. Your amplifier actually puts out volts, and the wattage varies with the load. A voltage output of 2.83 volts into 8 ohms is 1 watt, but into 4 ohms the same voltage would be 2 watts. Into a 1-ohm load, 2.83 volts is 16 watts! So for a given volume control setting, the 1-ohm Scintillas would draw 16 times more power than an 8-ohm nominal speaker. This would more than account for a 10 dB sensitivity difference, assuming identical efficiencies.
But wait - it gets worse. The Sound Labs aren't really an 8-ohm load. They're up around 40 or 50 ohms in the bass, dipping to around 6 ohms (or possible below 3 ohms depending on which generation backplates you have) around 500 Hz, rising back up to 12-16 ohms and then decreasing to about 2 ohms in the high treble. So the average might be closer to 10 or 12 ohms.
I have included a link to an on-line calculator so you can easily play around with the relationship between volts, ohms, amps, and watts. It's rather revealing. I recall an amplifier that boasted of 80 amps instantaneous current delivery. Into an 8-ohm load, that would be over 50,000 watts! Obviously, the marketing department was getting a little carried away.
Also, as Brian said, let your Sound Labs charge up for a few days, but don't crank the bias control all the way up. A sudden drop in humidity could result in the bias being set too high, with possible damage if not quickly lowered. I find that it takes about five days of being plugged in for a pair of Sound Labs to really come to life. Also, with the warmish-voiced Accuphase amps, I'd suggest starting out with the bass control at -3 or maybe -6, and the midrange control at 0 or -3, and the brilliance control all the way up. If the bass is turned up too high, the overall presentation will not sound lively.
Best wishes,
Duke