crossover schematic for Altec 604-8K?

[dr.joe]

Any leads appreciated: I'm looking for a crossover schematic for the Altec 604-8K. I have the stock crossovers, but my sense is that a crossover without the EQ and other controls and with higher quality parts would improve the sound of the speakers.

I'm also wondering what, if any, difference there is between the Altec 620A and 620B cabinets.

Many thanks,

Joel Tatelman (Ottawa, Canada)

[RonSSS]

I generated a schematic of the crossover on my 904-8A which I'm betting is identical to the crossover for the 604-8k. The 904 was simply a higher powered version of the 604. I'll try to cut and paste it here, but if it doesn't work I can email you a copy.
Personally, I feel the EQ is very beneficial. When set to the position that allows shelving of the MF, it reduces the amplitude in the 1500-4000 hz rnge, allowing the resultant response of the HF horn to be flat. Measurements tell me that as well as my ears.
I tore mine apart and removed the selector switch section, and left it wired for the dual shelving option.
I also messed with caps, but ended up liking the stock ones just fine. I'm sure there are better sounding caps to be had, I just didn't want to invest hundreds and hundreds of dollars figuring out which ones I liked. I spent over a hundred as it was.......

Well, I can't paste an image here and I don't have a web site so send me an email and I'll send you what I have.

Ron

[Jim D]

Our research into the 604H-K crossover and other older ALTEC units shows the schematics do not tell the whole story. The inductors in these items do not just directly interchange with "better" quality units. While the unit you build will work, our tests show peaks in reponse not there in original production.ALTEC had their own trnsformer plant and like the transformers in their amplifiers, optimized the inductors for where they were used, you just can't go build a unit and think it will work better. WE are continuing testing but for now I must caution, JIm