Seeking crossover for Allison CD-6 (or at least schematics for same)

[rnathans00]

I recently acquired what at first seemed a nice set of Allison CD-6 speakers. Wood in very good conditions, the grills too. Even the woofers had already been re-foamed. But I quickly noticed that tweeter output from one of the speakers was sub-par - low in volume and seemingly restricted only to the highest frequencies.

At first I assumed "it must be the tweeter", and began that frustrating search for a near equivalent so many are familiar with. But further testing involving a signal directly to the tweeter's front contacts suggests the tweeter is fine, which means the problem must be the crossover. A set I found for sale on the web had already been sold, so I'm facing a perhaps even more frustrating search. I couldn't find details about the crossover itself anywhere. So if anyone can point me to a source for said crossover, or even the schematics to perhaps help me rebuild it, I would appreciate it.

[JKent]

Why not open that one up and see what's inside? Probably a capacitor, an inductor and maybe a resistor. None of those parts are likely to go bad but caps and resistors should have their values marked on them and should be easy and inexpensive to replace. You could post photos of the innerds.

Another suggestion: The Yahoo Allison forum may be more active than this one so maybe someone there has torn into a CD-6.

here is the CD-7

http://f1.grp.yahoof...matics/CD-7.jpg

and the allegedly similar Five and Six (not CD)

http://f1.grp.yahoof...atics/A5-A6.jpg

So the Six and the CD-7 both have a single 8uF cap in the tweeter path. I bet if you bought a couple 8uF film caps you could fix those puppies.

Good luck.

Kent

[rnathans00]

Given the "goop" covering the parts, it's hard to see what's there, what their values are, etc. But here's what's really curious. One site offered a pair of "tested and working" CD-6 crossovers (sadly already sold), but they don't look like mine! Here's the link:

http://www.wensy.com/detail.asp?id=7931803

Attached are pictures of mine, which seems not to have the parts in the once-offered CD-6 crossover.

Did Allison change the design or just strip it down to cut costs? Now I'm really confused! I'll have to open the second of my two speakers (the one that seems to be working properly) to see if it looks like the first.

[JKent]

Hi

Too bad you missed those because $20 was a bargain. But looking at the sold ones, I wonder if they may have been modified. Looks to me like they each have 2 inductors, an 8uF cap and a small "bypass cap." AFAIK Allison did not use bypass caps--that's more of a tweak.

First suggestion: Start a new thread under the Allison section here: http://www.classicsp...php?showforum=6 You will probably attract more Allison enthusiasts there than under this FS/Wanted section.

I see the links to the 5, 6 & 7 schematics did not work, so here is the 5/6 schematic below. That schematic has just an inductor, an 8uF cap and a switch. You may be right about a change in design. The xos for sale were 40066 & 40067. Are your numbers close to those?

It's also "possible" that the xo with 2 inductors was a case of Allison using what they had on hand and combined to inductors to reach the needed 0.27mH value.

Be sure to look inside your cabinets and on the back of the tweeter to be sure there isn't another inductor lurking in there.

The "goop" is probably hot melt glue and should not be too difficult to pry/scrape off. One easy way to trouble shoot would be to swap the xo's left & right and see if the problem stays with the original tweeter or follows the xo to the other tweeter. Or just remove the 8uF cap and replace it with a new film cap and see if that fixes the problem (before you're done be sure to replace the caps in both xo's so they match).

Finally, I strongly recommend you join the Yahoo Allison group. We welcome new members here, but the Yahoo group seems to attract more Allison fans and sometimes Roy Allison himself responds.

Kent

[rnathans00]

Funny, I thought I *was* posting in the "Allison" and not the FS/Wanted section. (Still familiarizing myself with this site.) I will repost, as well as try the Yahoo group you suggested.

I'm not new to audio, but *am* to the underlying circuitry. Yes, I too see two inductors and two capacitors on those two offered crossovers, which in some cases might suggest a 2nd order crossover while mine looks like a 1st order. There are no components attached to my woofer or tweeter. I haven't (yet) pulled the second crissiver because it means pulling apart a working speaker - taking off those fragile grills, removing both woofer and tweeter, as well as the crossover.

As to the schematic, I think that applies only to the Five and Six, not the CD-6 as the Six had the toggle; the CD-6 does not. My SNs aren't even close: F-28580 and F-28581. Thanks for the suggestions.

[rnathans00]

Just a follow-up: I replaced the small capacitor (marked 8uF 50v, not the 100v specified), which looks like an electrolytic. I replaced it with an Erse Pulse-X 8.2 uF polypropylene, 250v. (I couldn't find a 100v.) I bought two just in case the result was a speaker that didn't voice like the second. The surgery was successful, and the patient lives. But I'm of the "If it ain't broke ..." school of thought. So since the two speakers appear to "match", I'd rather not chance damaging the (perfect) grills on the second, or the drivers for that matter, until the need arises. I'll just hold on to that cap until it's needed. Thanks, Kent, for your suggestions.

[JKent]

Thanks for the follow-up. Yes, the original was a bi-polar electrolytic. Was there just 1 cap? Higher voltage is fine, and the better film caps will have voltages of up to 600. No problem at all.

You should not need to remove the delicate tweeters--just the woofers to get inside.

I'm pretty sure your woofer surrounds are past their lifespan. Even if they "look" OK, if you rub a finger on the foam it will probably tear or disintegrate.

Kent

[rnathans00]

Yes, there was just one capacitor in the crossover. Yes, removal of the tweeter might not be necessary if one can disconnect it from the inside. Some capacitors - especially higher voltage ones - can be rather large. The Erse Pulse was smaller than some (also 250v) I'd considered, and even that one required some lead bending for a proper fit.

The woofers have already been refurbished and they are fine. Even given the room's sub-optimal acoustics, they sound great.