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rnathans00

Need CD-7 crossover schematic

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I've worked on the crossover of one of my CD-6 cubes, but now I'm going to take a stab at one of my CD-7 minitowers. But though they have the same drivers, the crossover looks more complex, with more components bunched together behind the speaker terminals. Can anyone point me to the schematic? Thanks in advance.

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Here ya go. Looks like just 2 inductors and an 8uF cap.

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So I was right - it is more complex than that of the CD-6 with the addition of that second inductor across the tweeter. But it does appear to use the same value capacitor as the CD-6. (I replaced a problem capacitor on one CD-6 with a better but low-cost ERSE.) I need to do a little more testing, but it appears one of my CD-7's tends to be 'bass'ier' than the second, so maybe I'm just not getting the right amount out of the tweeter. (Both woofers are intact.)

The trick of course, should it prove necessary, will be getting that crossover/terminal plate disconnected from the drivers and clearing away some of that wax goop so I can work on it. I presume need only worry about the cap. Thanks.

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It appears there's at least one additional component on this crossover - a little (blue) component I suspect is a bridging capacitor. What's the best way to remove or dissolve that hard wax goop?

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Well, here's a major update. Suspecting there was more to my problematic CD-7 than just a capacitor, I contacted someone prominent in the amateur speaker building community (he's helped design some well regarded ID speakers) and he offered to look at them. Low and behold, the trouble speaker had a tweeter whose response was all over the place. (The other was remarkably well behaved by comparison.)

We decided to do a full overhaul. Since it would be tough to find another Allison tweeter that closely matched (unless I scrounged from my working CD-6 pair), we're replacing *both* tweeters with something more modern, and he's designed a more complex crossover with a lower crossover point. I'll be picking it up within the next few days and will report on the results.

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How did this work out?

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So I was right - it is more complex than that of the CD-6 with the addition of that second inductor across the tweeter. But it does appear to use the same value capacitor as the CD-6. (I replaced a problem capacitor on one CD-6 with a better but low-cost ERSE.) I need to do a little more testing, but it appears one of my CD-7's tends to be 'bass'ier' than the second, so maybe I'm just not getting the right amount out of the tweeter. (Both woofers are intact.)

The trick of course, should it prove necessary, will be getting that crossover/terminal plate disconnected from the drivers and clearing away some of that wax goop so I can work on it. I presume need only worry about the cap. Thanks.

Some CD-6 models retained the first-order tweeter filtering of the earlier Model 6 version. Many later CD-6 models had the same crossover network as the CD-7. The earlier version of the CD-7, namely the Model 7, had that same simpler network.

Howard Ferstler

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How did this work out?

Pretty well. The tweeters were replaced with SB Acoustics SB29RDC, which required some cutting to expand the tweeter opening. Attached is a shot of the new crossover, which I mounted on the inner panel behind the tweeter. There seems to be a bit more dynamics in the treble range, a tad less dispersion perhaps. But I can't confirm until I do proper testing until I've corrected some of the acoustics in my listening room.

Not really using it much, as I've moved to Revel M22 and Totem Sttaf as fronts in my two listening rooms. I hate to use them as just surrounds, so if someone in the Washington/Baltimore area is interested in some nice Allison hybrids, they're available for sale. (Still have one of the original Allison tweeters, which is in good shape and tests well - unlike many samples offered on eBay.)

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