1204B Mods?

[des2105]

I recently acquired a set of 1204B's and had two questions. The Altec literature calls for an 811 horn but my set appears to have a 511B (based on the physical dimensions.) It is driven with an 808-8a. Is this a factory substitution or did a prior owner get creative? Also, what is the easiest way to change the crossover so it will cross at 500 and not 800. Is a different choke used? Or is it easier just to use an EQ to tailor the sound. I would like to get rid of the midrange heaviness it exhibits right now. Thank you.

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Altec did have the 511 in the 1204B. Not the 811. Sorry I can't help you W/ your other questions...
Mark

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Heres a link: http://www.lansingheritage.org/image...-mi/page08.jpg

[StuWelwood]

The link that n3135x gave you is a scan of the 1974 Altec Musical Sound Equipment catalog. I have that very catalog and the same one from 1975. It appears that the link is in error as to the date of the catalog, but it does indeed show the 1204B.

I bought a pair of the 1205B systems in May of '74 and still have them. The 1205B is identical to the 1204B with the only exception being that the 1205B is equipped with 771B biamps instead of the N809-8A crossover.

In 1974 the 1204B went for $580 at Sam Ashe, and the 1205B went for $884. The difference being the additional cost of the biamps, of course.

BTW, you're not missing anything by not having the biamps. I had to repair them more times than I could count. They were blowing out power transistors frequently and were generally a noisy pain in the *** . So, I replaced them a few years ago with a Rane AC22B active crossover and a pair of Altec anniversary amps. The difference in sound was stunning!

As to your other questions, I can't tell you how to change the crossover frequency, but I wonder why you would wish to. I have listened to mine at several crossover frequencies and have settled on 800 Hz as having the most natural sound. Since the original biamps allowed the selection of 500, 800, or 1200 Hz, I had played with them a bit and also came to the same conclusion.

My advice is ultimately to remove the passive crossover and biamp them, but that is less effective at what I think you are trying to accomplish, getting "rid of the midrange heaviness" as you said. My solution was to get a Sabine PowerQ 31 band equalizer and a calibration microphone. I run the EQ through the effects loop on my McIntosh C42 preamp. It's sounds great, but is a bit pricey. I did it anyway, because I wanted to use the 1205Bs as studio monitors.

For many years I used them as a home stereo system with a 10 band graphic EQ that I manually calibrated with a Radio Shack SPL meter with quite nice results. You might try the same.

[des2105]

Thank you all for your input. I did realize later that I had made a mistake regarding the horn used in the system. It is in fact a 511 which is exactly what's called for by Altec.

I may try biamping the system or using an EQ. I own a store (Classic Audio) in CT that deals exclusively with used equipment and therefore can pretty much take my pick of amps and/or EQ including a Behringer 31 band unit. Perhaps some combination of the above will sound better than what I currently have. When I spoke of mid-bass heaviness, I was comparing the 1204B to a set of Valencias that I own and I didn't think the Vlas had the mid-bass coloration the 1204Bs have. Of course it's a larger cabinet and sometimes that alone can cause a sense of heaviness.

Thank you all again.

Dave

[StuWelwood]

I used to have a Behringer EQ, but it never seemed to come up with the same, or even similar, results when running the calibration. It was also quite noisy compared to anything else in my system and didn't sound very good. In fact, it was so bad that I simply threw it into the trash! The problem is that there doesn't seem to be anything between the Behringer (a couple of hundred dollars) and the Sabine ($1600) that could do the same job.

You might just try fiddling around with a 10 band EQ. Try cutting a few dB at 240 Hz, as that's where that muddy sound seems to come from. Boost the high end to get some "air" and boost the low end for some thump, and you'll probably be surprised at how responsive these speaker are.