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Thread: Altec 1234 restore help needed

  1. #1
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    Altec 1234 restore help needed

    I am rebuilding a pair of 1234's. I cant find a crossover schematic for these. There is a number on the aluminum crossover plate 391922. I have installed a cheapo diaphragm from EBay in one horn. I see there is also a set available from people who claim to be using Altec equipment to build them now but 10 times the price. I went ahead and installed one diaphragm tonight and it ohms at 6.3 and sounds good with the sweep generator. The woofer sounds good but I get basically nothing out of the HF side. Before I just switch things around I want to know what goes where first. The one crossover has red,wht,grn and blk wires and from what I read rd to pos horn wht to neg horn grn to pos woofer and blk to neg woofer. The other crossover has a white wire where the grn one is on the other crossover and all the wiring looks really undersized. Original caps in here and I only checked the end one of I believe 6uf and it was OK. I stopped there and did not test the others.

    Before I start testing all the caps I thought I would ask here and see if perhaps the diaphragm might be the problem. A schematic would be nice to if anyone has one. I lean towards a cap myself since they are well over 20 years old. I think the caaps should be 28, 10 and 6uf but I am not sure.

  2. #2
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    Bump

    If anyone knows the answer or who does know or where to go online for an answer please respond. I have Altec parts in my shop waiting on information.

  3. #3
    Senior Member spkrman57's Avatar
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    Is that a electronic bi-amp or passive crossover?

    I have a pair of Altec N501-8A passive crossovers if you need passive.

    Send pics if you can so we can see it.

    Regards, Ron
    JBL Pro for home use!

  4. #4
    Senior Member gdmoore28's Avatar
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    427, Earl, or some of the other Altec experts will know exactly which crossover you have and how it needs to be wired. You need to post your enquiry on the AudioKarma site, as they and others seem to respond a little faster there. Otherwise, hold tite for a bit and one of them will see your post.

    Good luck.

    GeeDeeEmm

  5. #5
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    1234 update

    here are pics of the crossover.Name:  DSC_0001.jpg
Views: 129
Size:  88.0 KBName:  DSC_0003.jpg
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Size:  87.5 KB

    I have replaced the diaphragm both of which were toast and used a Chinese knockoff part commonly found online. There are also some at ten times the price made on old Altec equipment. I have no idea of the difference between these two for sound and would REALLY like to hear from users who have tried both to know.

    Recapped the crossover and it is a different sound than I am used to with my La Scalas. It seems as though the sound is improving over the course of a couple of hours after I got it all back together and fired it up and they are pretty darned good especially with classical organ and Stevie Ray Vaughn.

    So any suggestions as to what would improve the sound quality further?

  6. #6
    Senior Member gdmoore28's Avatar
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    1. I can't find the references now, but I've read two reports on the Chinese diaphragms where they were tested and diagnosed. The results were that they are not suitable for the sometimes low crossover frequencies Altec used (500-800Hz), but from 1200Hz and up they were acceptable. Long term reliability, though, is an unknown at this point.

    The GPA diaphragms you referenced are top notch and exceed the performance of the originals. And, yes, they are made by former Altec folks on Altec machinery. There is also the Radian brand. Also made in the USA, get great reviews, and about the same price as the GPA diaphragms.

    2. Sound improvement: your next logical step is to install the Altec 30923 equalizer network between your crossover and the horn. The network is cheap and easy to build and will make one of the most significant contributions to a hifi-like response that you can perform. (It consists of only three resistors and one capacitor. Do a search and you will find the schematic.)

    GeeDeeEmm

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