[Jerry]

"Peter Wieck" wrote in message
...
Jerry wrote:

My den is quite small and my normal listening level is less than 1 watt,
but
occasionally I'll listen at levels higher.

Jerry:

There are a lot of misconception to do with "volume", and especially as
it relates to "watts".

At one watt average, with moderately dynamic source, you will need at
least a 100-watt amp to get clean peaks absolutely without clipping.
But you already know this. Put another way, a speaker with an 86dB @
1-watt SPL, a 30-watt amp simply will not cut it, even bi-amped at
anything above a very moderate volume. Agreed, mostly one listens at a
very moderate volume. But not always.

Peter, please remember that the 30 watt amp is driving strictly the mid and
tweeter. Further, this amp sees greatly reduced fundamentals, so the
voltage swings are NOTHING like what a single amp would experience. When
playing music at levels I can just barely stand (somewhere around 10 -20
watts), PEAK output voltages in this amp are LESS than 7 volts.

Now, one reason for that low output voltage is that I removed those blasted
pots from the AR xover circuit. This netted a huge gain in sensitivity on
just those drivers. So I must compensate by reducing volume or the
mid/tweeter will overpower the woofer. To give you a feel ... the average
voltage swings in the woofer amp are 5 times higher!

Based upon all of the above, there is just no way that peak output voltage
could ever get to the 40 volt rails in the mid/tweeter amp. Further, rail
drop will be minimal given the low current drain of the mid and tweeter.

Peter, please remember that I don't have the fundamentals going through that
30 watt amp and this significantly changes the game and the math.

Components of the vintage of your Heath more-or-less send straight DC
into the speaker when driven to clipping. And depending on the source
(where, as it usually happens most of the signal is at the mid-range),
that could be a lot of the time and pretty rapidly fatal to your
speakers.

Even if this is the case, (and I doubt that because I measured the filter
caps and they are just fine), the mid and tweeter will never see the impact
of the clipped waves and resulting harmonics in the woofer amp. Further,
neither will the woofer as it's internal xover will reject those harmonics.

Peter don't forget that the Heath amp sees reduced harmonics as well. Now
this reduction is NOT as great as the reduction of fundamentals in the 30
watt amp, but still there is a significantly less harmonics "riding on
fundamentals" than what a single amp would see.

Again, put another way, it is (Very typical of vintage SS amps)
amplifiers of low power that burn speakers, not high power. Almost any
well-made speaker can handle normal signal at very high power, well
beyond their nominal ratings, for brief periods. Even the very best
conventional PM speakers will fry in short order when fed DC. I think
this is what the OP was trying to convey.

Peter, if we drove this 30 watt amp to the 40 volts rails, clipping would be
the least of our problems. Both the mid and the tweeter would be smoking
long, long before. With the fundamentals removed, the impact of stacking 40
volt rails on top of 40 volt rails in the Heath is equivalent to a 750 watt
amp. Now this is from the vantage point of the mids/tweeters. (The woofer
still sees the same 100 watt amp with but even it "goes further" without the
harmonics.)

Those of us who dabble in tube equipment tend to ignore this simple
truth as output transformers will not pass DC, so clipping is much
softer and relatively harmless (to the speaker, that is). Also why
those of us who have high-powered amps (tube or SS) also tend to ignore
this as there is enough headroom in any case to minimize consequences
from clipping.

Peter, you can ignore it, but the truth is that I have far, far more
headroom than you with your "brute" ss amp. You must pass fundamentals
with harmonics on top through that amp. Further, you still have the pots
"sucking up power" in your AR-3a's and this also contributes to a reduction
in headroom.

Bi-Amping, even as you have applied it will create some advantages if
very carefully managed. But the real-world difference between a 30 watt
amp and two 30-watt amps split is limited in this *particular*
application given that at any given moment about 75% of your signal
will be at/within the midrange, and if you include the tweeter, that
goes to about 90%, at least as it applies to the need for headroom. I
would very strongly suggest that you make it your mission in Audio to
beg, borrow or steal a well-made high-powered amplifier (200W/RMS/CH @
4 ohms or better) and re-evaluate your position.

Peter, are you saying that 75% of the signal STRENGTH is going to the
mids/tweeters? This is totally incorrect and I have a dual channel scope
to prove it. Less than 25% of the voltage swings are going to the
mid/tweeter amp. Then if we integrated the signals to compute power, once
again the real power is in the woofer amp ... BY A LOT! It's not even
close.

I have the equivalent of a 750 watt amp (@ 4 ohms - 375 watts @ 8 ohms).
Why in heavens name would I want a mere 200 watt amp. That would be going
backwards.

Regards,
Jerry