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AR 302


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  • 2 weeks later...
Guest richd

I have one in my hand as I type this. It looks to be the same as the schematic for the AR 303a crossover that is posted on in the AR library under the AR 303 series link. Also from that section one can find the AR 303 series brochure which calls out the same crossover orders and crossover frequencies for the 302 and 303. The crossover orders called out in the brochure are consistent with the AR 303a crossover schematic.

In the AR 302 crossover electrolytic caps replace the mylar caps and no mylar bypass is used. This appears consistent with the $4.00 cost decrease of the AR 302 crossover sited in the AR production cost document found in the AR 303 series library I have not measured the inductor values of the AR 302 crossover but the woofer inductor appears to be smaller than the stock AR 303a crossover pictured in the library. Given that the 10 inch woofer of the 302 would have a mechanical high pass roll off higher than the 12 inch 303 woofer one would expect component value differences to occur during the computer optimization of the crossover once the woofer driver models were included.

One notes that modern driver model of a dome midrange would have to be modified to take into account losses from the material in front of that driver before computer simulation. Given the first order low pass section on the midrange and the 3rd order high pass section on the tweeter we can assume that the mechanical driver roll off of the midrange is utilized as part of the low pass transfer function of the midrange crossover in the 302 and 303.

It is interesting to compare the crossover of the AR 3a and the crossover of the Magic II to the AR 303a. The Magic II crossover is a modern 3rd order Butterworth design. The AR 3a is its own thing. The AR 303a looks like a missing link. In essence the entire AR 302 appears to have been designed to be a missing link when one compares the 302 drivers and the cabinets to the AR 5 and modern designs

From a sonic point of view (matched levels) I find the AR 302 to sound like a missing link in comparison to the AR 5 and a well designed modern speaker. I will also put my two cents in here and point out that the smaller woofer of the AR 5 and 302 does a lot to clean up the lower midrange relative to the AR 3a and 303. This observation was also noted by Consumer Reports at the time they did the review of the AR 3 and AR 2a 30 years ago.

Also of interest is that the 302 goes lower than the AR 5 since the 302 is 1 dB less sensitive as result of changes in the design of the woofer. The 302 almost approaches the AR 3 frequency response although the distortion performance is not as good. We thus get better midrange performance relative to the AR 303 and almost the full bass response of the AR 3a. One is left to wonder why the AR 302 gets no respect. The AR 303 has the same sensitivity reduction and goes lower than the AR 3 (see the section in the library called comparison between the AR 3a and AR303). The sensitivity for the AR 3a is a typo I think. It is specified as lower in other AR spec sheets.

If you after the AR 302 schematic information to modify the crossover then you are in luck since you can follow the path to the AR 303a. I would not suggest playing with the inductors unless the one you wind yourself has the same inband electrical Q (you can add a small resistor to compensate). The complete inductor model would have been incorporated into the computer optimization of crossover at the time the AR 302 was designed. You can redesign the whole crossover to a modern design like the Magic II using modern CAD tools but I think this defeats the intent of the designer to create a speaker that is a missing link. I also note that once I pulled the crossover out of the cabinet I got a buzz at low frequencies when I put it back and had to do something to dampen it.

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