freed@foxvax1.UUCP (D. Freedman ) (01/21/84)
(Reprinted without permission from the Boston Phoenix, Feb. 15,1983.)
The American way wins out
Bob Carver's theory
of objectivity in practice
by E. Brad Meyer
Every once in a while something happens that distills perfectly
the real fascination that audio holds for its devotees. You see, hi-fi
is not concerned just with mere technicalities, however much it may
appear that way. It isn't even entirely about music. No, friends,
hi-fi is about Life, the Universe, and Everything. Why, at the Consu-
mer Electronics Show in January, Bob Carver - but wait. Perhaps we'd
better give you some background first.
For years the audio world has been divided into two major camps.
There are no names to describe them fairly, but the most neutral terms
for the two groups are subjectivists and objectivists. The subjec-
tivists maintain that only by listening can we make any valid judge-
ments about equipment, and that measurements give little or no informa-
tion about what the equipment sounds like. Some hi-fi gear, they main-
tain, sounds clearly superior for reasons that are either very compli-
cated or completely unknown - and maybe even unknowable.
The objectivists have a less mysterious view of things. They hold
that the specification and measurement of audible performance, at least
of electronic components like power amplifiers, though difficult, are
entirely possible. The distinctions that the subjectivists find so
important are, they say, the result of changes in simple parameters
like frequency response, and not of complicated distortion mechanisms
or other, similarly arcane, remedial devices.
To the objectivists, the subjectivists are dreamy nonthinkers, too
easily impressed by pseudo-technical mumbo jumbo, and too easily gulled
into paying high prices for equipment that sounds different, but not
really better. The subjectivists think the objectivists are a bunch of
tin-eared spoilsports, insensitive to sonic subtleties and anxious to
declare nonexistant anything they cannot quantify.
Regional differences between the groups exist, by the way. New
England in general, and the Boston Audio Society in particular, are
centers of "objectivist" thinking. It probably has something to do
with the cold winters and the legacy of puritanical frugality. The
subjectivists (in popular stereotyping anyway) live west of here,
mostly in California.
There are manufacturers in both camps; not surprisingly, the mak-
ers of the most expensive equipment believe most strongly in the value
of subtle improvements. Bob Carver, president and chief designer of
Carver Corporation, must be counted as a member of the objectivist camp
because his equipment does alot and doesn't cost very much. For
instance, Carver's most expensive power amp, the M-1.5, has a rated
continuous output of 350 watts per channel into eight ohms, with a peak
power of 1.5 kilowatts (hence the model number), yet it lists for only
$799, little more than a dollar per watt.
Carver has for some time had a running argument with one Peter
Aczel, golden-eared guru and publisher of a magazine called The Audio
Critic. Carver averred that the differences Aczel claims to hear
between power amplifiers are simple in nature and easy to duplicate.
Carver issued Aczel a challenge: Aczel was to pick any power amplifier
he liked, and Carver would, by means of simple modifications, make one
of his own power amps audibly indistinguishable from it. He would, as
he explained it at the Carver Corporation press conference, make the
transfer function - the complex expression by which the input signal is
multiplied to get the output signal - of the two units exactly the
same. Taking Carver up on his challenge, Aczel chose the Mark Levinson
ML-2, a gigantic monaural megalith with countless output transistors
and huge heat sinks, which puts out 35 watts/channel into eight ohms
and costs $3150 ($6300 for a stereo pair).
Carver brought a couple of M-1.5s and some test equipment to
Aczel's facility and spent about four days fiddling with his unit,
evaluating his work with an ingenious null test. In this test the
carver and the Levinson were fed the same signal, and the loudspeakers
connected to their outputs were placed outside the listening room in
acoustic isolation. Then a third speaker was connected across the two
output terminals of the power amps. The third speaker, which was in
the listening room, emitted sound produced by the difference between
the transfer functions of the two amplifiers. If there was no audible
signal coming from the speaker, there would be no audible difference
between the amps. The test is very sensitive, because the difference
signal is heard by itself, with no annoying music to distract the crit-
ical ear. After Carver's adjustments, the sound out of the third
speaker as 74 db below the level of the music, inaudible even in the
absence of the music itself.
Aczel then assembled a listening panel (of which he was a member)
and performed a regular listening comparison. At the end of the exer-
cise he officially pronounced (and will publish in the next issue of
his long-dormant magazine) that the two amplifiers were audibly
equivalent, unless of course the music gets loud enough to overdrive
the Levinson, at which point the Carver sounds much better.
The modifications, Carver announced, have been included in all M-
1.5s shipped after November, 1982. "You can tell you've got one of the
new ones because the front panel says 'M-1.5t'," he said; "the 't'
stands for 'transfer function' or 'tweak'." The price of the M-1.5t is
unchanged, at $799.
For those interested in the technical details, the modified unit
has polypropylene film capacitors, installed at the suggestion of Aczel
before testing even began; its ultrasonic output filter has been made
less aggressive; it has a slightly higher input impedance at high fre-
quencies, and a higher damping factor (the latter achieved by wiring it
internally with Monster Cable); and its open-loop gain and feedback
have been adjusted. No transistors were changed, nor was the basic
topology of the circuit. The null between the two amps reportedly held
up well with several loudspeakers.
Carver has in the past occasionally annoyed some of us in the
audio community by his aggressive promotion of units whose designs were
still unfinished, and by his free appropriation of misleading technical
terms for marketing purposes. His "Sonic Hologram," for example, has
little to do with holography, and his "Magnetic Field Amplifier" is
ingenious but not really magnetic. This time, though, he has struck a
major blow for the American Way.
What makes Carver's achievement so typically American is his pri-
mary concern with results, not with methods. The Levinson amplifier is
noble in concept, extravagant in execution, imposing in appearances; it
has mysticism and majesty, and it costs a bloody mint. The M-1.5t is
small and unassuming in appearance, but has enormous reserves of per-
formance. In automotive parlance it's a "sleeper" - a '49 Hudson body
hiding a blown 396 Chevy V8 with tricked-up suspension and brakes.
Compared to the Levinson there is something almost uncouth about it.
Or rather, there was; in its new version it bears the imprimatur of one
of the high priests of audio, and it's still cheap, too.
We got preprints of The Audio Critic's write-up at the press
conference, and to read Aczel's version of the story you would think
that the all-knowing guru told the well-meaning and talented (but
unfortunately ignorant) designer all about how to fix his amplifier so
it really sounded right. Bobby did as the sage instructed him, and lo!
a miracle!
The conventional engineering wisdom (which is well supported by
careful experiments) is that the initial audible differences between
the amplifiers were most likely a matter of the extent to which they
maintain a flat frequency response into the complex load presented by
the loudspeaker. Aczel speaks approvingly of Carver's "reformation"
and assures us that if he ever entertained such heresy he "abandoned
that pious mid-fi tenet" in the course of his work.
It was clear from what Carver said at the press conference that he
has done no such thing, but he was diplomatic about it. He is content
to let Aczel's version stand publicly, saying that though he does not
necessarily consider the differences between the old and new versions
of the M-1.5 terribly important, to some people they obviously mean a
great deal. If he can satisfy those people with a minor redesign, then
he is willing to do so.
Aczel maintains that there are still reasons for buying a pair of
Levinsons, even though it means spending almost eight times the money
for one 10th of the power. But physical beauty and predicted reliabil-
ity are the only ones he can think of. He acknowledges that "the
Carver M-1.5t symbolizes with great poignancy the end of the high-end
boom of the 1970s"; to his credit, he is genuinely pleased that
audiophile-quality sound has become available in such a practical pack-
age.
And so here we are. Every M-1.5t is being checked against an ML-2
at the Carver factory; without debating the technical issues at all, it
is easy to appreciate the value represented by high power in a small
and inexpensive package, especially when accompanied by such a guaran-
tee of consistent high performance. We're going to try an M-1.5t at
home soon.