Altec 604B (1948)
Little is documented about the 604B beyond its place in the Duplex lineage, but the essentials are clear. The 604 Duplex was produced from 1945 to 1948. The 604B arrived in 1948 as an improved version of that original 604. Altec priced it at $125.00. The Duplex built its reputation on a midrange that, unlike many competing coaxial designs, did not exaggerate the middle frequencies. The flip side, as Vacuum-Tube-Valley noted, was that with some amplifiers the design could produce a "hole in the middle" character. Recording engineers of the era compensated with frequency compensation - sometimes checking their work on home hi-fi speakers.
That's most of what the record holds. The 604B is listed in the Altec catalog as an improved version of the original 604. It turns up in collector circles largely on the strength of the Duplex name, not on any well-documented changes specific to the "B" revision. Expect the usual Duplex caveats - these are old - and treat any seller claims about B-specific revisions with caution, because the documentation isn't there to confirm them.
- Introduced: 1948, as an improved version of the original 604
- Original price: $125.00
- Predecessor: 604 Duplex (1945–1948)
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