604-8H & 604-8C

[Jeff M]

I have a chance to pick up a set of new 604-8H drivers still in the boxes and a set of the 604-8G crossovers (only a few scrapes on the back, but in good shape). What would be considered a very good buy for these at a minimum? I need to act pretty fast on these and not sure what to offer?

[UreiCollector]

A brand new pair on ebay would easily fetch over $1000. I wouldn't hesitate to pay $1000 for a brand new pair.

[Don McRitchie]

The 604-8G cross-over is not the best fit for a 604-8H driver. One of the primary benefits of the H version was the introduction of a more advanced cross-over that for the first time included equalization to flatten out some of the more obvious response discontinuities that exist to some degree in all 604's. The G cross-over is pretty much just a simple frequency splitter. While it would work, it would not match the performance of a complete H system.

[CONVERGENCE]

GPA has Cross Over's for their 604 8H II. I would give him a call to see if they would match your 604 8H. Ask for Bill.

http://www.greatplainsaudio.com/


...................

[TnTn]

IIRC, the 604-8H is the last of the alnico 604's. If NOS and a friendly deal, $1K is fair. If not from a friend, I would offer up to $1500 for the set and then flip the 8G xovers and build my own 604-8H xovers. If you decide to back out, please PM me.

[UreiCollector]

Another major differance is the 604-8G had a multicellular horn, and the 604-8H had a mantaray horn (constant directivity horn).

[Zilch]

http://www.altecpro.com/pdfs/vintage/SpeakerAndMics/duplex/604%20Forever%20All%20Models%20Summary.pdf

[CONVERGENCE]

I found this article by Jeff Markwart.


Enter the H model
In early 2004 I acquired a pair of 604-8Hs, the last ALNICO magnet duplex model Altec produced before they switched to ferrite magnets. It was also the first Altec duplex model equipped with the Tangerine phase plug, Mantaray constant directivity high frequency horn, and a crossover that utilized dual equalization of the compression driver output. I swapped out my 604Bs for these Hs using the same cabinets, and was immediately impressed by the differences in output - well controlled upper mids, significantly more high frequency extension, improved imaging detail and more apparent bass & mid bass. What was in that Dual EQ crossover? Could it be adapted to older 604s as well?



At the basic level the 604-8H filter is a parallel 3rd order HP and 2nd order LP filter, with L pad shelving of all horn frequencies when the EQ button on the front panel is in the released position. Pretty much like a stock 604-8G filter. However, when the EQ button is clicked inward to the depressed position, the similarity ends. The older style shelving circuit is disabled, an adjustable, frequency dependent, contour circuit is pulled in for the upper mids, a high frequency trim circuit becomes active, and a driver-side series resistor further shapes the rising HF slope. At the recommended dial settings the upper mids are appropriately depressed relative to the high frequencies, and results similar to the famous Mastering Labs and UREI 604 filter implementations are achieved. Unfortunately, this Altec filter is not time domain corrected like the others - so I naturally wondered just how would it sound if applied to my phase corrected 604B filters




http://home.earthlink.net/~jmarkwart/sitebuildercontent/sitebuilderfiles/604_8Hpcwmfeq.pdf


......

[Jeff M]

TnTn....sent you a PM. Thanks for the repies everyone;).

[John]

I found this article by Jeff Markwart.


Enter the H model
It was also the first Altec duplex model equipped with the Tangerine phase plug





http://home.earthlink.net/~jmarkwart/sitebuildercontent/sitebuilderfiles/604_8Hpcwmfeq.pdf



......


Well not quite correct, I have seen 604-8G units with the Tangerine phase plug.:blah: