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Dick Pierce on Altec, or MM?
(Sam Byrams) wrote in message . com...
1. A system built before and, subsequently, in effective ignorance
of the comprehensive Thiele-Small model. Thus, as a result, a
misdesigned, mistuned conglomeration of poorly integrated parts
and, well, "concepts" to be generous, that misses the theoretical
capabilities of a cabinet that large and a woofer that big by a
VERY wide margin.
Many enclosures were available for the 604, which is the driver
proper, and the old ones are crude by modern standards. The Japanese
have built several commercially, they tend to be really big and heavy.
Big and heavy is good until you have to ship it from Japan.
Maybe you missed the point of my remarks. The 604 design comes from
an era when no one new how to design a box suited to a driver, and
no one new how to design a driver to fit in a box. People couldn't
do reasonable driver/enclosure and thus system designs because no one
knew, back in the middle 1940's what any of this stuff meant.
A number of variations of the 604 exist, but typical T/S figures
on them run something like:
Fs 27 Hz
Vas 450 L
Qms 2.32
Qes 0.22
Qts 0.20
Xmax 3 mm
Yes, it's got phenomenal efficiency at about 98 dB 1W @ 1m, but
at a pretty significant cost: look at the Qts figure of 0.2.
Aiming for a maximally flat response requires the speaker to be mounted
in a TINY box, on the order of 80 liters, tuned to about 50 Hz. The result
is impressively flat, less than 1 dB response variation (ignoring driver
response anomolies), but is hardly impressive bass-wise for a 15" driver,
struggling, as it does, to reach down to 53 Hz.
In the more typical cabinet used for these drivers, which is an excessively
large cabinet tuned with large ports at a very high frequency, the response
of the system is, well, abyssmal. How about an 11 dB peak at 80 Hz, with
a response that plummets like a rock below that.
And the horn is such that crossover frequencies like 900 Hz are a
bare minimum. That's asking an awful lot of an untreated paper cone.
2. A "real" large driver with very poor linearity that has no better
linear volume displacement than your alledged "cheap" smaller
drivers, with a stiff and VERY non-linear suspension.
With an excursion of all of about 3 mm, despite its enormous magnet
and underhung voice coil, this 15" driver has no more output capability
than one of those "cheap" 10" drivers you go about.
3. A "real" expensive crossover that was designed without any
consideration of conjugate load matching
Doug Sax of Mastering Labs designed a much better x/o but although
it's still available to order I think even he would admit biamping is
better.
But the basic item is SO handicapped by its fundamental limitations. It
was an amazing driver in its time. But it's time was 1945. That's almost
SIXTY years ago, my friend. Event ignoring your rather biased and poorly
constructed remark about "cheap" drivers, pretty much EVERYTHING that's
understood about the interaction of cabinets and drivers, system
integration, crossover design, driver design, EVERYTHING occured
significantly AFTER the 604.
You take ALL of that knowledge, lump it into a single pile, call it
"the stuff they sell at Madisound" and "Speaker Builder mentality
projects" as if that represented the Parnassus of loudspeaker knowledge
and proceed to tilt against it like some evil windmill. Well, there's a
much larger world of knowledge about loudspeakers than that, I would
hesitate to suggest. And the Altec 604 is NOT part of it, because it
was born 25 years too early.
If you like the Altecs, fine. But holding them up as a paragon of
design acumen, as shining examples of how to design a well-performing
speaker in any reasonable objective sense is, well, amusing.
I have a pair of late (Mantaray) 604s with Mastering Labs x/o in some
cement cabs. I like them but they are not perfect. Improved cab design
and biamping will lead to substantial improvement, I think.
No, you have already run up against the unresolvabel fundamental
design limitations of the the beast. Theya re intrinsically what
they are, and NO amount of fiddling will get them beyond that point.
Appreciate them for what they a probably one of the best examples
of the black art of speaker from 6 decades ago, a period where more
witchcraft and alchemy and kitchen-sink fiddling then science and
understanding and real engineering ruled.
604's, like T. Rex, is a magnificent specimen of a time long past.
We can admire them, study them, marvel at their anachronistic
magnificence.
But, like T. Rex, they're STILL extinct. Their time has come, and
their time has gone. R. I. P.
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