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PattonLowenstein

Repaired 2ax and 4x; questions about the next ones.

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Hi all,

I want to start by saying-- Thank you all!

(And my god, what an absurdly long post this has turned out to be…I’m going to give a spark notes, then post the full story afterwords so it’s easy to skip if you feel like it.)

Short story:

-        I replaced the pots etc. of an AR 2-ax and a 4x (both my dad’s from the late 60’s)—both sound amazing now—thank you all so much for replying to past threads. In no particular order, and sadly I’m sure I’m forgetting people to single out--JKent, RoyC, ra.ra, and stupidhead all showed up many times with excellent advice and encouragement. Michael T's diagram and photos were also invaluable. 

-        Bad news: The other 2ax and 4x tweeters are shot—the 4x can’t get any resistance reading, the 2ax reads around 3 ohms, but won’t put out any sound

-        Since I would rather hear them working again (and don’t have another $250 hanging around for two original tweeters), I’m leaning toward buying replacement tweeters and adding the crossover mods –here’s where my real questions start:

I don’t have a high opinion of my own hearing, so I’m leaning towards replacing only the tweeters that don’t work, then balancing out the sound with new matching tweeters when my dad’s old ones eventually go gently into that good night. (Is this a horrible idea?)

-        It seems like the HiVi Q1R with a 0.05 mH inductor in parallel and a 3uf cap is a good option for the 2-ax tweeter. Correct?

-        For the 4x, it seems like opinions are split between dropping in either HiVi Q1Rs or AR-T-135s, both with no mods. Does anyone have a couple of cents to add on this one?

-        Again, thank you! It means so much to have my dad’s old speakers playing again.

 

Here’s the full story:

As far as my dad can remember, he bought the 4x’s with his summer job money building tennis courts in North Jersey in the late 60s. I can [mostly] read the date on one of the woofer magnets, and I think it says “Mar 15 1966”, but it could as easily be 1968 or 1969. The date on the other has faded too much to tell. Both have cloth surrounds on the woofers, and they’re in fantastic shape—no problems that I can identify.

He bought the 2ax’s when he was manager of his college radio station, probably in 1969 or ‘70. The only legible date I can find is “Mar 11 1969” on one of the woofers. Both woofers have cloth surrounds, and it seems like the cones, surrounds, and Masonite rings are well seated and in good condition. When I got the first one back together, its ceremonial first song was “The Weight” by The Band on the album “Music From Big Pink”. One of my dad's finest accomplishments: his radio station had the privilege to play that album’s world radio premiere when he was manager. Immediately after, it was followed by Schubert’s “Death and the Maiden” string quartet, which I think is an underappreciated and epic piece of music (see video).

As for their performance: I’ll start with the good news: I’m proud (as a complete newbie) to say I have one of each up and running. Luckily, the [now] working ones only had the ol’ deteriorated pot problem, so I bought new L-pads, caps, a bunch of wire, and redid everything. I went with the 25 ohm resistor on the midrange in the 2ax, along with new 4 uf and 6 uf caps in the 2ax and a 20 uf cap in the 4x.

Sadly, I’m fairly sure one of the 4x tweeters is beyond repair. I can’t get any resistance reading on it, so I think the wire somewhere in there has broken or something has shorted. Plus, there’s powdery rust coming out from under the cloth surround (cone?), which has completely separated from the faceplate. The other tweeter (which does work) also has the rust coming out around the edges, and the surround seems….not totally secure. While it sounds good, I don’t think it’s very long for this world.

I haven’t been able to find any accounts of people repairing them, but if you have ideas or suggestions, I’m definitely down to take it apart and try fixing it--I'm mechanically inclined and I have nothing to lose. In lieu of that, I think my best option is to buy two replacements, replace one, and wait for the other to fail. That way, eventually I’ll have balanced sound, but in the meantime I can enjoy the final days or years of the original part my dad enjoyed half a century ago.

As for the 2ax’s, one is in amazing shape. It was the first one I put back together, and when I first turned it on---wow! A whole string quartet from one cabinet. I was blown away.

The other one unfortunately has the tweeter problem where the yellow glue dots have failed. It still has 3 ohms of resistance between the terminals so I put the speaker back together after work yesterday, but the tweeter…sadly….didn’t tweet. I know it should’ve been 4-8 ohms for a working tweeter, but I couldn’t help but hope.  I think I’m going to go with the HiVi Q1R 1 1/8” tweeter with a 0.05 mHz inductor in parallel glued underneath, as well as dropping the capacitor in the HF circuit down from 4 to 3 uf. (I think I understood this correctly from other threads, but I may have mistaken a conversation about replacing a 3a tweeter.)  

From a similar thread, I think my best option with the 4x’s may be to drop in the same Q1R, as opposed to going with a phenolic ring tweeter, so I think my best play is to get four Q1R’s, two 3uf caps, and two 0.05mH inductors. Anyone have any opinions?

Again, thank you so much for all the opinions and advice you’ve all shared over the years. I don’t know how many threads I’ve read about these two AR models over the last couple of months. My dad bought these speakers over a half century ago, and to have even just two of them working again means a great deal to both of us. Hopefully, given a little more time, I’ll have the full set making music again soon. You can see the current setup with a Denon AVR-1508 receiver and Boston Acoustics subwoofer, both of which were free at the dump. I’m pretty sure the only reasons they were thrown out were a broken source select knob on the receiver and a stain on the sub’s grille. As they say, one person’s trash….yada yada yada.

Both sets had the mineral wool, which I replaced with the pink stuff, and totally shot pots. While I like the idea of repairing the pots, I’ve spent enough time dealing with dissimilar metal corrosion to have any illusions or dreams of actually doing it. They’re in a plastic container in my garage if anyone wants them. PM me.

Obviously the cabinets need some TLC, but I'm waiting until I have the sound all figured out.

Ok. Wow. Almost 1300 words later (wouldn’t my boss like to see that output!), I think I have a problem….If you’re still with me, I really appreciate your help. Please let me know what you think!

Regards,

Patton

 

 

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On 5/20/2020 at 6:32 PM, PattonLowenstein said:

don’t have a high opinion of my own hearing,

Based on the above statement my two cents is

1. Disconnect the working tweeter and you will have a pair of AR2x

or

2. Install matching HiVi Q1Rs.  

I don't have a recommendation for the 4x but the Q1R has never been adapted for 4x application in this group.

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The Q1R bottoms out around 2500Hz. The 4x crosses over at 1200Hz.

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3 hours ago, Aadams said:

Based on the above statement my two cents is

1. Disconnect the working tweeter and you will have a pair of AR2x

or

2. Install matching HiVi Q1Rs.  

I don't have a recommendation for the 4x but the Q1R has never been adapted for 4x application in this group.

Thanks! I'll go with the Q1Rs for the 2ax. I do like hearing those cymbals. 

2 hours ago, genek said:

The Q1R bottoms out around 2500Hz. The 4x crosses over at 1200Hz.

Could this be solved with a capacitor modification, like a 15uf instead of the 20uf, to raise the crossover up to the lower end of the replacement's range? (I may be misunderstanding the function of a capacitor, and the math that determines frequency crossover.) Simplyspeakers's AR-T-135, which calls itself a replacement for the 4ax tweeter, apparently has a bottom end of 2kHz. 

Or does the 4x's woofer top out below that? 

 

Thank you both again for responding. I'm very new to this. 

 

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I don't think any classic era 8" AR speaker ever crossed higher than 2000Hz. No idea what the upper limit of the woofer is.

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