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AR90 replacement woofers


Guest blastinbill

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Guest blastinbill

Does anybody know the proper impedance of the original AR90 woofers? About 10 years ago I had foam rot on all 4 woofers and the 2 lower midranges in my pair of AR90s and replaced all of these drivers with replacements from AB Tech. I have since discovered that three of the woofers have part number "1210033-2a" and are 4 ohm nominal impedance, while one of the woofers has part number "1210040-2a" and is 8 ohm nominal impedance. I brought this to the attention of AB Tech and they said the 4 ohm woofers used to be the replacement but are now unavailable and only the 8 ohm woofers are being sent out as replacements. Obviously I want to keep the original AR sound, and I should have refoamed my originals (since long gone), but the AR90 crossover schematic does not indicate the proper woofer impedance. Substituting woofers of improper impedance will surely change at least the low pass -3dB frequency. I can't beleive AB Tech would send me a set of woofers with different impedances.

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Guest dogmeninreno

> Does anybody know the proper impedance of the original

>AR90 woofers? About 10 years ago I had foam rot on all 4

>woofers and the 2 lower midranges in my pair of AR90s and

>replaced all of these drivers with replacements from AB Tech.

>I have since discovered that three of the woofers have part

>number "1210033-2a" and are 4 ohm nominal impedance,

>while one of the woofers has part number

>"1210040-2a" and is 8 ohm nominal impedance. I

>brought this to the attention of AB Tech and they said the 4

>ohm woofers used to be the replacement but are now unavailable

>and only the 8 ohm woofers are being sent out as replacements.

> Obviously I want to keep the original AR sound, and I should

>have refoamed my originals (since long gone), but the AR90

>crossover schematic does not indicate the proper woofer

>impedance. Substituting woofers of improper impedance will

>surely change at least the low pass -3dB frequency. I can't

>beleive AB Tech would send me a set of woofers with different

>impedances.

I believe the AR90's used a 10" 8 ohm driver..The AR9 used a 12" 4 ohm woofer..I have several of the 8 ohm 10" woofers for the AR90 if you need any. Dale

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Guest blastinbill

Thanks for the replies. I, too, have the AR90 owner's manuals and they only refer to 4 ohms as the nominal impedance of the speaker system (all 5 drivers with crossover), and not the impedance of any of the individual drivers. AB Tech is sending me 3 more 8 ohm woofers (not original...if anybody has the original AR90 woofers with square shaped magnets, let mr know) to go with the one that I already have so I hope 8 ohms is the correct value. Blastinbill

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Guest dogmeninreno

>Thanks for the replies. I, too, have the AR90 owner's

>manuals and they only refer to 4 ohms as the nominal impedance

>of the speaker system (all 5 drivers with crossover), and not

>the impedance of any of the individual drivers. AB Tech is

>sending me 3 more 8 ohm woofers (not original...if anybody has

>the original AR90 woofers with square shaped magnets, let mr

>know) to go with the one that I already have so I hope 8 ohms

>is the correct value. Blastinbill

I have the original square magnet 8 ohm AR90 woofers.. duffydog1234@sbcglobal.net

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>I have a set of AR-90's and the owners manual say they are 4 ohms. I am not sure where this 8 ohm stuff is coming from.<

Two 8 ohm resistors in parallel yields 4 ohms.

Two 8 ohm woofers in parallel is 4 ohms.

Since the speaker has two 8 ohm woofers, in the woofers' frequency range the speaker SYSTEM is 4 ohms over those frequencies. The midrange is not 8 ohms since there is only one. (I think it is really 6.x ohms) The upper midrange and its associated crossover parts is also about 4 ohms as there is only one. The tweeter the same. Therefore, over the entire range of frequencies that the speaker will play, it's "nominal" impedance is rated at 4 ohms.

The speaker has a separate impedance for each frequency it plays regardless of which driver is playing or what combination of drivers are playing. There is no hard-and-fast rule about what a manufacturer claims as "nominal impedance." The "4 ohm" description is descriptive, but not necessarily 100% accurate. It is "about" what the speaker's impedance is, on average, sort-of, over the entire audio band, kind-of. A speaker is not a simple resistor and is not exactly the same impedance over all frequencies.

I was initially confused about this with an AR-9. The AR-9 uses two, 4 ohm woofers but has a complicated circuit adding and subtracting impedance at various frequencies so that the average is still 4 ohms. Well, honestly it isn't even an average of 4 ohms. It's more like a median once you remove the big spike up at resonance. (if you have any interest in how this works, you should read "engineering the AR-9" in the Library - it's pretty interesting - and ingenious, and enlightening about what goes on in any speaker insofar as impedance is concerned)

No such complex circuit exists in the AR-90. In a 90, two 4 ohm woofers would add together and produce 2 ohms (sometimes more, sometimes less) and that would likely smoke more than a few amplifiers.

I've talked a lot, but did I make enough sense so you can see how two eights make a four?

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Hi Bret;

You are absolutely correct, the 2 - 8 eight ohm speakers in parallel gives an approximate 4 - ohms for the woofers.

When I saw this topic earlier, I was going to ask if there was 1 or 2 woofers in that model speaker, I didn't know.

If, for example, 2 - AR-3A's rated at 4 ohms, were connected in parallel, we would have a real amplifier problem.

With their individual impedances actually going down to 2.75 +/- ohms, I can assume that, the amps would be seeing, as the worst case scenario, about 1 3/8 ohms, maybe.

What I have noticed is the abundance of 6 ohm replacement drivers, and a shortage of 4 ohm drivers, on the better quality driver market.

Also now reading, that, AB Tech, is supplying different impedance drivers, as the correct impedance drivers, are not available.

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  • 1 year later...

Maybe I have overlooked it, but as I read this thread, I did not see any answer to the question of whether this is THE proper original part for the AR90. The thread seemed to result in the conclusion that it was the PROPER impedience. But never mentioned the part number "1210040-2a" again, or addressed it's appropriateness. Would someone please be kind enough to address the Part # issue.

Thanks

Jeff

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Thanks for responding so quickly. But I THINK you may have in haste, made an error. I believe the FAMOUS 200031-1 woofer driver is the later version AR 12" from AR3a, AR9 & MANY other models. The AR90 has 10" woofer drivers Part # (?). Feel free to set me straight if I've missed this.

If I am right take proper solice in the fact that, the only people who never make a misstake, are people who NEVER do anything.

Thanks

Jeff

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Hi, Jeff -

I'd been using the reference numbers from the AR-90 schematic, which shows driver numbers identical to their AR-9 counterparts, with the exception of the woofers, which are listed as "200031".

The AR-9 blueprint lists the 12" drivers as part number 200003-1 or -2.

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The point must be made that THIS paragraph is NOW refering to AR 12" woofers. Those guys at AR were trying to make us crazy. (Perhaps I may be a little pedisposed to the condition.) I have attached a JPG of a pair of 12" straight sided, factory stamped 12" woofers Pt# 1210003-08&2A currently on eBay. There are 2 pairs of these same speakers, removed from my pair of AR9's, in my family room RIGHT NOW. They BOTH carry a STICKERED Pt# 2000031-1. 1 pair has ROUND magnets, the other pair are SQUARE. The numbers referenced in this paragraph refer to 12" woofer.

This is now just puzzleing the heck out of me. I owe you an apology for MY falure to COUNT zeros.

Regarding the AR90 10" woofer, I originaly asked about. You DO make reference to a Schematic. It's just that I have seen so many refererences to schematic errors, on THIS site that I am PRETTY reluctant to consider them as relable Part # references.

I DO appreciate your input and information. But to be honest, at this point I would really appreciate any clarification regarding part #s of BOTH the 12" and the AR90 10" I originaly asked about. Perhaps yourself or another member can shed some light referencing an additional or more reliable source.

Thanks Again

Jeff

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Hi Jeff

The part #s for the different drivers used in AR speakers can also be found in the late seventies/early eighties official pricelists from AR Teledyne, they are available from the CSP library. Also here the (1)200031-0 is listed as the correct part# for the AR-90 10" woofer (1986 pricelist). This supports the part # AR-pro found in the schematics. The 200040 is for a different range of speakers, no other AR speaker has, accoring to the list, used this driver.

BRgds Klaus

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Thank you Klaus and PRO for your responses.

I did FINALLY find the 1986 Part List thanks to Klaus's prod. Previous attempts came up empty or 1979.

I also found the schematic, dated 1978. It is obviously official and properly assumed to be accurate. My concern with a document like this, is that in my experience, production changes (in any manufacturing situation) don't always get pushed back, or added to such documents.

Thank You for the Assistance

Jeff :)

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I have a pair of AR90 speakers; all four (original) woofers are part# 200031 (manufactured in early 1979); they have square magnets, and two dust caps per driver (the inner cap is paper and the outer [cosmetic?] cap is cloth).

To the best of my knowledge, the AR 10" woofer part# 200040 is correct for the AR38s & AR48s. (My guess is that the 1210040-2 driver may be later Tonegen unit, perhaps acceptable as a replacement for the 200040 driver, but questionable when used as a substitute for the 200031).

AR90 Driver Part Numbers:

Tweeter = 200029

Upper Mid = 200028

Lower Mid = 200027

Woofer = 200031

Robert_S

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Thanks for this accurate and brief summation.

This is the conclusion I arrived at, but never made CLEAR.

The original post concluded that the 040 woofer was the correct impedance, WITHOUT mentioning that it was NOT the correct driver.

It that respect hopefully this time has been well spent. Even if clumsily managed by myself.

Thanks

Jeff

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