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Crossover issues AR-2AX


Mark D C

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Hello. About 8 months ago I picked up a pair of early '70's AR-2AX speakers. They still had the original midrange drivers, woofers, capacitors and pots installed and a pair of replacement HiVi Q1R 1 tweeters. I replaced the capacitors and pots in December with Dayton Audio PMPC-4.0uF 250 V caps for the midrange and DMPC-5.6uF 250V and PMPC-0.47uF 250V soldered together for the high range drivers.

 Last month I decided to upgrade from the HiVi Q1R 1 a to pair of Peerless tweeters (https://www.parts-express.com/pedocs/specs/264-1676--peerless-da25tx00-08-spec-sheet.pdf). After 40+ hours I began to notice what I will describe as a buzzing sound in the middle frequencies. Yesterday I called and spoke to a tech person who, although unfamiliar with the AR's, made an educated guess that there was an issue with capacitors.

Does anyone have a clue as to why this is happening? Thank you.

 

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1 hour ago, Mark D C said:

Does anyone have a clue as to why this is happening?

The 2ax is not really a 3way.  Your tweeter is running full range in the 2ax unless you modified it.  The original AR tweeter has a natural roll off around 5k.  If the Hivi  was correct it had coil on he back that made it roll off around 5k as well.   Perhaps you are hearing beating from interference with the mid range driver.  Your tweeter and mid are both covering the same frequencies down to the woofer crossover.  Just a guess. 

In a sense it is a crossover problem because the 2ax is really a two way crossover. 

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Hi Mark, and welcome to the forum. While I'm not exactly sure what Aadams is driving at, I do know that you have incorrectly installed the capacitors - - - the tweeter  circuit uses the smaller (4uF) value while the midrange employs the larger (6uF) value in all versions of the 2ax speaker. Maybe you can please describe why you think the Peerless is an "upgrade" over the Hi-Vi and what you are trying to achieve with this replacement- - - adding pics to your post is always helpful.

 

 

AR-2ax schematic v.4.jpg

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3 hours ago, Aadams said:

The mid runs full range...

I remain a bit confused by the point you are trying to state. The mid driver has a 6uF cap filter that limits lower frequencies reaching this driver to 1400Hz (according to AR literature).  

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Hello original poster, this is easy enough to isolate with use of the mid and HI controls on the back of the speakers. If you are buzzing with the HI turned all the way down, now it’s either the mid or the woofer, then it can simply by isolated further by removing the jumper wire on the back terminals and connect directly to terminals. 1 and T. Still buzzing? Do this connection to both speakers and compare with the balance control, both speakers mids should sound similar, if the buzzing speaker seems like it’s hitting more lower frequencies than non buzzing speaker, its probably a crossover wiring mistake. If both sound similar, but one buzzes, it’s probably the mid driver at fault.  No buzzes? Probably woofer issues.

I’ve never experienced buzzing from new capacitors. Shorted old caps, could probably cause buzzing on drivers, so I’d rule out caps almost immediately if connected correctly. 

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1 hour ago, ra.ra said:

The mid driver has a 6uF cap filter that limits lower frequencies reaching this driver to 1400Hz (according to AR literature).  

Understand your confusion. I mean they run full range after they crossover at 1400.   The tweeter the OP has chosen responds well below 2kz I was pointing out he had the tweeter overlapping the mid but I have no idea if that is related to what he is calling "buzzing".  It would have been better had I not posted on this one.

 

 

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46 minutes ago, Chris1this1 said:

If both sound similar, but one buzzes, it’s probably the mid driver at fault.  No buzzes? Probably woofer issues.

Shot-in-the-dark: This is not simple to diagnose, but if these are early 2ax's  with cloth surround woofers, the buzz problem could be from the masonite ring coming loose from the cast metal basket. If so, need to re-glue. Could also be similar situation at masonite ring under the spider. 

7 hours ago, Mark D C said:

....a pair of early '70's AR-2AX....

...but of course these could be the later foam surround woofers.... OP needs to clarify particular components.

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If the OP did wire the capacitors backwards, then they would be experiencing exactly what I heard with mine a couple weeks ago, when I messed up by relying on an incorrect schematic that I found online. I described it as the mid-bass being "muddy". I have probably destroyed my credibility here but did not hurt the speakers. I switched the caps and fixed that problem. Still need to replace the tweeters since they are original and have very little output. Here is that thread.

 

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11 minutes ago, bluelick said:

I have probably destroyed my credibility here...

Not at all.....in fact, I was thinking about your thread earlier when I read about Mark's problem. It is very easy to make these sort of wiring mistakes. I always need to check, re-check, and triple check my wiring connections in most every project. Still, there is a "buzzing" problem here....

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1 hour ago, ra.ra said:

Not at all.....in fact, I was thinking about your thread earlier when I read about Mark's problem. It is very easy to make these sort of wiring mistakes. I always need to check, re-check, and triple check my wiring connections in most every project. Still, there is a "buzzing" problem here.... 

Yes, I'm curious about the "buzzing" because what I was hearing when I had the capacitors swapped was a sort of distortion that I wouldn't have to stretch too far to think of as "buzzing" perhaps depending on what was being played. If the OP does have the caps reversed, and if he swaps them, it will be interesting to learn whether that fixes it. If the caps are reversed, then the tweeter is getting signal down to around 1400 Hertz, and maybe it doesn't much like that--hence the buzzing? Not contesting anything here, just glad to be along on the learning journey.

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12 hours ago, Mark D C said:

Hello. About 8 months ago I picked up a pair of early '70's AR-2AX speakers. They still had the original midrange drivers, woofers, capacitors and pots installed and a pair of replacement HiVi Q1R 1 tweeters. I replaced the capacitors and pots in December with Dayton Audio PMPC-4.0uF 250 V caps for the midrange and DMPC-5.6uF 250V and PMPC-0.47uF 250V soldered together for the high range drivers.

 Last month I decided to upgrade from the HiVi Q1R 1 a to pair of Peerless tweeters (https://www.parts-express.com/pedocs/specs/264-1676--peerless-da25tx00-08-spec-sheet.pdf). After 40+ hours I began to notice what I will describe as a buzzing sound in the middle frequencies. Yesterday I called and spoke to a tech person who, although unfamiliar with the AR's, made an educated guess that there was an issue with capacitors.

Does anyone have a clue as to why this is happening? Thank you.

 

As ra.ra pointed out, you apparently incorrectly installed the larger cap (6uf) in the tweeter circuit and the smaller cap (4uf) in the mid circuit. There is nothing likely to be wrong with your new film capacitors. There could be issues, however, with what you did with them.

If you did not use a parallel coil of some type with the Peerless tweeter (as you should have with the HiVi tweeter), there is much more current going through it. If so, your intended "upgrade" was most certainly a downgrade. There is also no reason to believe the Peerless tweeter would have represented any kind of improvement over a properly implemented HiVi tweeter.

Buzzing is most often caused by a malfunctioning or over-driven driver.

Roy

 

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Thanks, every After just now opening the first speaker, to my dismay, I discovered that in fact, the caps were properly installed.
So, as to the recommended and critical modification to the tweeter, could someone please point me to the instructions.
Thanks again! 

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5 hours ago, ra.ra said:

Shot-in-the-dark: This is not simple to diagnose, but if these are early 2ax's  with cloth surround woofers, the buzz problem could be from the masonite ring coming loose from the cast metal basket. If so, need to re-glue. Could also be similar situation at masonite ring under the spider. 

...but of course these could be the later foam surround woofers.... OP needs to clarify particular components.

These are the 11" foam surround woofers. 

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6 hours ago, Chris1this1 said:

Hello original poster, this is easy enough to isolate with use of the mid and HI controls on the back of the speakers. If you are buzzing with the HI turned all the way down, now it’s either the mid or the woofer, then it can simply by isolated further by removing the jumper wire on the back terminals and connect directly to terminals. 1 and T. Still buzzing? Do this connection to both speakers and compare with the balance control, both speakers mids should sound similar, if the buzzing speaker seems like it’s hitting more lower frequencies than non buzzing speaker, its probably a crossover wiring mistake. If both sound similar, but one buzzes, it’s probably the mid driver at fault.  No buzzes? Probably woofer issues.

I’ve never experienced buzzing from new capacitors. Shorted old caps, could probably cause buzzing on drivers, so I’d rule out caps almost immediately if connected correctly. 

Hello, Chris1'. Yes, I did isolate each driver by using the controls. This made a small difference.  I haven't tried the second method, connecting the wire directly to the terminals, but will do tomorrow. 

Now to the modification ...
Thanks. 

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9 hours ago, RoyC said:

As ra.ra pointed out, you apparently incorrectly installed the larger cap (6uf) in the tweeter circuit and the smaller cap (4uf) in the mid circuit. There is nothing likely to be wrong with your new film capacitors. There could be issues, however, with what you did with them.

If you did not use a parallel coil of some type with the Peerless tweeter (as you should have with the HiVi tweeter), there is much more current going through it. If so, your intended "upgrade" was most certainly a downgrade. There is also no reason to believe the Peerless tweeter would have represented any kind of improvement over a properly implemented HiVi tweeter.

Buzzing is most often caused by a malfunctioning or over-driven driver.

Roy

 


 

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8 hours ago, Mark D C said:

as to the recommended and critical modification to the tweeter, could someone please point me to the instructions.

A belated welcome, Mark

The Hi Vi mod is Roy's thing and there has been some evolution over the years and from model to model (AR). I think the current recommendation is to install a 0.05mH inductor in parallel with the tweeter if you are using L-pads, 0.07 if you are using pots. It can be mounted to the back. A spacer is recommended. I think Roy originally also added a 1.5 Ohm resistor to the tweeter circuit but I believe he found that unnecessary. 

There has been discussion as to whether or not to reverse the leads. The inductor changes the phase relationship. You might want to copy this search text

hivi tweeter inductor site: classicspeakerpages.net

and paste it into google. You'll get all the CSP threads that discuss the topic. This one may be the best place to start:

-Kent

 

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