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Replacing a 3a mid driver - Looking for guidance


Vern48
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I recently discovered the midrange driver in one of my AR3a speakers, serial 86650, is faulty, emitting a crackling, buzzing sound around 800HZ. I determined this by playing frequency bands on a test CD.

[Has anyone come up with a repair for the mids as is being done for the tweeters?]

I have a single older, poorly stained,  pine AR3 cabinet that has a ‘service replacement’ mid driver in it. I believe it is the Tonegen. Got this speaker quite a few years ago with a bad mid and had it replaced by AR in Norwood, long before I started doing repairs myself. This pine cabinet looks to be early and is in pretty rough condition although someone with more skill than I could most likely refurbish.

I believe the Tonegen would be a correct, suitable replacement in the AR3a. Not sure if a crossover change is required.

I’m trying to decide whether to “steal” that driver out of the old AR3 to replace the bad AR3a driver, or try to locate a used driver that matches the one in the 3a cabinet, which I believe is a ’70-73 era, 200010-1, based on the images in the restoration document.

I guess I would just part out the rest of the old cabinet, But, I hate to trash a working AR speaker, even if it looks bad. As far as I can tell, there are no issues with the woofer and tweeter.

Another factor, I’m now retired, and thinking of downsizing my equipment stash. My hearing isn’t quite what it used to be, either. Thinking the pair of 3a’s would be more desirable, if I decide to sell them, if they both have “period correct” mid drivers.

Looking for wisdom and thoughts approaching this in case there are factors I have over-looked.  Or, am I overthinking this?

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Hi Vern, I don’t know of anyone(yet) who can repair a 3a mid. The 3 midrange can be repaired(check with RoyC). midwestspeaker.com does show an AR-9 replacement mid and says it can be used in the 3a. If I replaced mine I would use 2, nothing was mentioned about any crossover changes.

RickB

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The 10pi and 11 mids are identical to the 3a and some later mids (9, 90, 92, 38s) are nearly identical, just missing the screen iirc. Those have a plastic wave guide that I think can be removed and the screen from the 3a can be glued on “I think “. Maybe see what more experienced members say about that.

Edited by JKent
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3 hours ago, Vern48 said:

buzzing sound around 800HZ. I determined this by playing frequency bands on a test CD.

All of your mid drivers appear to be 3a style mids.  Swap the 3a mid in question with the 3 mid.  The crossover in the 3 is 1000hz.  You should have a working 3a pair and the mid in the 3 that buzzes at  800hz may no longer have an audible buzz. 

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5 hours ago, Aadams said:

All of your mid drivers appear to be 3a style mids.  Swap the 3a mid in question with the 3 mid.  The crossover in the 3 is 1000hz.  You should have a working 3a pair and the mid in the 3 that buzzes at  800hz may no longer have an audible buzz. 

Interesting thought.  It didn't occur to me that if that driver was put in the 3, it may never be called on to reproduce frequencies in the problem area because of the higher crossover.  I'll give it a try and see what happens.  Probably won't get to it until next week.

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Before I start, genuinely not now trying to win an argument, or potentially rattle anyones cage, just trying to help and perhaps I am more likely to in the end gain some knowledge for my own benefit.

But, asking as somewhat of an amateur, could not an out of specification capacitor/component cause a driver to be subject to frequencies/distortion outside of the range for which it was designed ? Or is it the case that whatever the full range of frequences that any given driver is subjected to it will only reproduce the frequences for which it was designed accurately and without distortion ? Even if a faulty component is connected in series/parallel with it ? The op mentions the distortion becoming apparent at a frequency/frequencies around 800 Hz ?

Again, I am not trying to be clever, but I am most happy to be, kindly, enlightened. Thanks in anticipation.

 

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26 minutes ago, lance G said:

The op mentions the distortion becoming apparent at a frequency/frequencies around 800 Hz ?

If the problem remains in the same cabinet after the swap it could be the crossover or perhaps even something loose inside.  The chances are low that two out of three drivers would have the same buzzing sound at 800hz.

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