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My Altec 604e build.

pete1729

pete1729

Super Member
I'm well enough down the road to actually post about it.

I got a pair of 604e’s last summer. They were in Great Falls, Montana, mounted in some cobbled Fisher cabinets. We settled on $460 for the pair.

I dithered for an eternity. 612 cabinets, 620's, Onken. I settled on Bilfort's corner cabs. Something about the 26" wide front baffle made sense to me in that both the 612 and 620 feature this as a dimension.

Crossovers? Mastering Labs, GPA, etc. Then someone reminded me that no less than Jeff Markwart had designed an XO specific to the 604e based on the N1500. It offered some midrange EQ and used the inductor I already had.

It seems so obvious now.

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Curious that you're using contractor grade plywood over cabinet grade or the industry standard Baltic Birch ply.
 
Gigantic said:
industry standard Baltic Birch ply.
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Industry standard in the pro world predominately for it's tensile strength, not for it's acoustic properties. Baltic Birch rings, much like a solid hardwood, and requires specific approach to damping and bracing. But, it's strength is absolutely superior if you're going to have roadies in and out load your cabinets several hundred times.

The contractor grade ply is the closest material to what would have been originally used for 604E cabinets in both R & D as well as production. This is not to imply that it's better or worse for the application, just that it's probably the closest period correct material available today.
 
The lower cabinet stiffener (the lower picture) is laid out like Bilforts plan. I realized that if they were evenly spaced, the upper stiffener would interfere with the driver. I laid it out differently so it would actually support the driver. Its vertical placement is still one third of the way down, and this necessitates moving the driver up higher on the baffle. Seemed like a good idea. 20251029_144723.jpg20251029_144710.jpg
 
How are going to tune the port? I my case with the speaker mounted in a 6 cu ft box to be used mounted on a wall at standing ear height or up against a 10 ft ceiling I would tune the box using a spectrum analyzer for flattest response. In either case they were flat down to the middle or lower 30's. The ports were a bit different for sure. That was about 50 years ago. A fiend of mine who had a MFA degree in Theater from Florida State built his own 8 cu ft boxes about 44 inches high. I tuned them for him. While I was doing that the first clarinetist came in and heard them from our local Symphony and we built an Identical pair for him. We sold 5 or 6 pairs off John Michael's design. He used very thick marine plywood similar to what EV used in building their 800 Patrician. We hung a curtain of cotton wool batting like Bozak used to dampen internal reflections. He used MC 60's, C-11 and a MR 65B and an AR TT with a Magnecord tape recorder. Of course most everything back then was SS even from Mcintosh, But he wanted a warmer smoother sound like his dad's system back home in Florida.
 
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twiiii said:
How are going to tune the port? I my case with the speaker mounted in a 6 cu ft box to be used mounted on a wall at standing ear height or up against a 10 ft ceiling I would tune the box using a spectrum analyzer for flattest response. In either case they were flat down to the middle or lower 30's. The ports were a bit different for sure. That was about 50 years ago. A fiend of mine who had a MFA degree in Theater from Florida State built his own 8 cu ft boxes about 44 inches high. I tuned them for him. While I was doing that the first clarinetist came in and heard them from our local Symphony and we built an Identical pair for him. We sold 5 or 6 pairs off John Michael's design. He used very thick marine plywood similar to what EV used in building their 800 Patrician. We hung a curtain of cotton wool batting like Bozak used to dampen internal reflections. He used MC 60's, C-11 and a MR 65B and an AR TT with a Magnecord tape recorder. Of course most everything back then was SS even from Mcintosh, But he wanted a warmer smoother sound like his dad's system back home in Florida.
Click to expand...

The ports on these boxes have the same area and depth as the Altec 620 cabinet.
 
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