Heath Hi-Fi Question

[Jack Crenshaw]

There are a lot of aspects to your question, which I'll try to answer as
best I can. A good start is to note that the typical table-top radio of the
50's-70's made about 1/2 watt. That was with the volume turned wide open.
With a decent speaker, 1 watt will be painfully loud in most listening
rooms.  All those other watts, then, only provide for headroom for loud
transients.

ca. 1965, I had two amplifiers, one rated at 25 watts and one at 30.  They
sounded pretty good, but I decided that they needed "tuning up."  I put them
on test equipment and discovered, to my amazement, that the 25-watt amp was
only putting out 600 mW without clipping (a resistor had shifted value).
The other one was putting out 6 watts. After tuning, of course, they both
sounded better, but the fascinating thing was that, during normal listening,
power levels on the order of a watt still sounded pretty good.

Another issue is speakers.  Old bass reflex enclosures were quite efficient;
as high as 20%.  That means, of that 20-watt
W-4M, 4 watts would end up as sound power.   Trust me, that's enough to
drive you out into the front yard, if not the street.
When AR introduced the acoustic suspension speaker, efficiency went down to
1%, or even 1/2%.  It doesn't take a rocket scientist to figure out that
implies a ratio of as much as 40:1 on power input.  To get the same
performance as the 20-watt W-4M, you'd have to drive an AR-1 with 400 watts.

Many modern speaker systems use ducted-port or other bass reflex designs,
and power efficiency is back up again, but not as far as it was.  On the
other hand, small non-vented enclosures like the ADS or Tandy Minimax still
use huge amounts of power for the sound they produce.  So the short answer
is, older speakers needed far fewer watts than newer ones, to get the same
sound level.

Another issue is headroom.  If 1/2 watt produces a comfortably loud sound,
what is the other 19 1/2 watts for?  Answer: Headroom, for dynamic
transients. When a tube amplifier is driven to its limits, its distortion
behavior seems, to some, to be less objectionable than an equivalent SS
unit. So SS amps need more power, to ensure that they are never driven near
the limits.

Finally, mfrs sometimes play games with specs. That 150-watt, 4-channel
system you mention may or may not really put out 150 undistorted watts, with
all channels driven.  Even at that, it's less than 40 watts per channel,
which is not that much more than the Heathkit.

Jack

----- Original Message -----
From: Ed Goss <meg at APLCOMM.JHUAPL.EDU>
To: <HEATH at LISTSERV.TEMPE.GOV>
Sent: Monday, November 05, 2001 12:09 PM
Subject: Heath Hi-Fi Question


> Hello,
>      Although I recently sold some old Heath hi-fi equipment, I
> haven't been much involved in that aspect of Heathkits; most of my
> time is spent on ham gear.  But I did become curious as to the
> great demand for old Heath amps, like the W4-AM Williamson
> amp, for example.  It's only rated at 20 watts.  Many speaker
> systems today appear to need much more power to drive them
> properly.  And there seem to be many high-powered amps available
> today for reasonable prices.
>      So my question is this: What makes the old Heath amps so
> desireable?  I assume people use the amps and don't just buy
> them to sit on a shelf.  Is there something unique to the sound that
> a modern 150 watt/4-way speaker system can't equal?
>      Thanks for the comments.
> --Ed--
>
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