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AR3 Midrange help!


Guest watson

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What a great forum, very glad I found it! I just picked up some sweet AR3s and am in the process of restoring the cabinets and have detected that a midrange is not working. The pots are okay and I verified that the crossover is okay by testing it with a another known working Pioneer midrange. I also removed the tape and checked the fine wiring from the post up to the speaker. Looks good. Can someone give me some tips or possibly point me in the direction of a new, used midrange that works? Many thanks for any help.

Vance

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Guest matty g

Vance

Congrats on the new speakers. Assuming that you checked the pots/xovers by connecting the test mid to the terminals in the front faceplate of the cabinet, check the fine wire where it enters the midrange screen - this is a common breaking point and it's easy to miss. Be VERY careful when removing the insulating tape and be shure to replace it to keep the leads from shorting to the frame and each other. If you can find a break in the wire, you may be able to solder it back together with a fine tip iron.

Otherwise, and I hate to say it, ebay. Just make shure that the seller "claims" it is in working order, for all the good that does.

Sorry to sound so sarcastic, but I know lots of people who have been burned buying drivers on ebay. I don't know of any good drop in replacements - other people on this site may - but if you go that route you'll have to buy two drivers.

Hope you can find an open wire on it!

Matt

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Vance,

How do you know the pots are OK?

If you cut the green wire going to the mid-pot wiper you can measure the resistance of the mid driver WITHOUT removing it from the cabinet.

If you get a reading, solder the green wire to the terminal with the other green wire. This "effectively" sets the pot to max increase.

Regards,

Jerry

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Thanks for the replies. I assume the pots and wiring up to the post on the front of the cabinet where the mid is is fine because I connected another speaker to the posts and it worked. Adjust the pot and it adjusted the mid I jumped off the posts. Therefor I assume the pot and wiring is good to the post. Am I right or missing something.

I guess the next step is to pull the tape off the leads again and get out the magnifying glass and closely check the fine wires up to the cage again.

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Vance,

A quick way to verify the condition of an AR-3 midrange or tweeter is to scrape the black paint from the 3-terminal tweeter terminal board on the front of the speaker; by holding a wire from one terminal of a 1.5-volt flashlight battery to the middle or common terminal, take the wire from the other terminal of the battery and lightly touch it to the other terminal going to the midrange driver. You should hear a distinct crackling sound from the driver if the driver voice coil is not open. Do not exceed 1.5 volts to make this test.

Unless you have or can locate a single-battery holder with output leads (Radio Shack), this operation will require that you solder a piece of stranded wire to one end of a flashlight battery and another piece of stranded wire to the other end. Strip the insulation back about 1/4-inch from the end of each wire, and you can use this for a quick test of the tweeters and midranges regardless of the condition of the level control.

No output from the driver most likely points to a "popped" midrange driver, meaning that the coil has jumped out of the gap due to excessive input energy and/or deteriorating foam suspension pieces, but I have found that there is no "mandatory" oxidation half-life of the foam pieces of the AR-3 domes as there is with foam surrounds on woofers. The early AR-3 domes -- those without the fiberglass pad on the outside of the dome under the screen -- were more prone to this phenomenon than the later ones. You can visually detect the occurance of this over-driven condition.

If you have determined unequivocably that the driver is burned out, there is no reasonable OEM replacement driver that can match the characteristics of this driver, so your best bet is to go out on eBay and locate an AR-3 midrange from someone who has parted-out an AR-3. If, on the other hand, you retrofit a cone midrange or something, the tonal characteristics will be greatly altered, most likely for the worse.

--Tom Tyson

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