AR 58S Rebuild

[frankmarsi]

15 hours ago, briodo said:

Thanks for that tip Frank. This is the first time I've had two AR's that are as close to identical as AR58S with AR91 xover and the AR91's.  Honestly I admire someone like yourself who took years putting their system together and finally finding Nirvana.  It's clear you have built a truly unique system that we all secretly yearn for!!  

Will try out the stacking using a Crown XLS2002 running the 2 pair in series which should produce 375 w/c at 8 ohms.  Not quite the same as the famed Phase Linear, but will be fun to try out.  

 

Thanks for that compliment "briodo" and coming from a member that's been here since 2006, that says many things to me. Regarding my comment on how some others that have chosen the route of besmirching my posts instead of praising my systems they must be fuming. The irony here is it's always individuals with lesser set-ups, and some with ,lesser experience in setting up a 'real' quality system.

On another note, regarding driving those two similar though different speakers, I have to agree can be fun to a degree. A number of years ago, I connected four AR-3a's to two Phase Linear PL-400 amplifiers so, all components were identical.  I found the pairing to be somewhat bass heavy and 'thick' sounding, so I chose not to go forward with it. A note-worthy member on this forum also admitted to this tendency occurring but, perhaps with these two models you speak of you might have better results. Just keep in mind when speakers are 4 ohms, it could stress even the most hardy of amplifiers and fusing is recommended. It would prove to be a learning experience in any event, just don't play too loudly no matter how good it might sound. I believe that amp you refer to has a inboard cooling fan. Ultimately, it would always be better to use two identical amps.

So, good luck with all that and I'm sure all here would like to hear of your results.

[harry398]

On 8/14/2020 at 5:24 PM, briodo said:

And I finished the frame.  I do not know the source of the cloth, as I bought it years ago and have enough left to do many speakers.  Not sure that was a good idea, but it is what it is.  Also the colors in person do not match the photo.  The AR91 is original and the two look identical in pattern and color, not sure why my cell came to a different conclusion.  All in all I'm happy with outcome.

The AR91 and AR58S sound alike, which should not be a surprise. My wife helped me do AB test using speaker out switch on the receiver and we could not tell the difference.  

Next on the bucket list is make like Frank Marsi and stack them.  That should be fun.

  

Brian......

 

Revisit the sound......are you sure they sound the same?

I never had the ar91, but my brother has.....he says...the 91 is not as good as the 58s...bass is better on 58s.

 

Just asking.

 

[DavidR]

AR-91:1979-1982,12" Woofer,1.5" dome Mid, .75" dome Tweeter, Range: 35-25K ± 3db, 87 db, xover 700/7500hz, power req 15-200 w, Ohms: 3.2-4 ohms, 31.5x14x11.5, 53.0 lbs

AR-58: 1981-1983, 12" Woofer, 1.5" dome Mid, .75" dome Tweeter, Range: 37-25k ± 3db, 87 db, xover 700/7500hz, power req 15-200 w, Ohms: 4 ohms, 27x14x11, 52.0 lbs

The above info is from http://www.aphenos.net

It would seem the 91 has a slight edge in bass otherwise all is much the same.

[briodo]

On AR91 vs AR 58s, it is a valid question and needs more listening to provide an answer.  

In the case of the AR58s in question, it may no longer be a valid comparison.  The crossovers are from an AR91 with -3/-6db attenuation on tweeters/mids, along with a brace I added since AR91's come with more bracing.  My observation is they may be more AR91 than Ar58s at this point.

I adjusted the mid and tweeter to -3db which can't be done on a AR58s.  The default AR91/AR58s attenuation setting is overbearing to me from a sound experience.  I do have a Soundcraftsmen equalizer, but will admit the switches on the back of a speaker make it fairly easy to get close to what sounds right.  

More listening must be done and I hope to provide feedback on an A/B experience in the future. 

The question becomes, are the switches taken out of the equation?

[ar_pro]

Same drivers, essentially the same internal volume once the AR-91's plinth and oddly-shaped top are factored into the measurements, and the same crossover, minus the AR-91 level controls, associated resistors, and spaghetti.

The AR-91 had a mini "acoustic blanket", and (sometimes) foam inserts, which made a slightly audible difference with close-in listening,  but not so much in larger spaces. And of course, the 91 had the mid & tweeter level switches for 0 dB and -3 and -6 dB settings. 

Differences in sound could be related to variation in the type & amount of stuffing used in any restoration,  the volume of any additional internal bracing installed, as well as in the vagaries of woofer surround repair & replacement; otherwise, I'd say that there's no audible difference in low-frequency performance between the two systems, and essentially no difference in mid or high frequency presentation when listening at a distance of 15 feet or more.

The AR-91 used AR's very best switches, but to me, the 0 dB settings sound fine, and I prefer the crossover without any level control circuitry.

[briodo]

On 9/12/2020 at 12:56 AM, ar_pro said:

Same drivers, essentially the same internal volume once the AR-91's plinth and oddly-shaped top are factored into the measurements, and the same crossover, minus the AR-91 level controls, associated resistors, and spaghetti.

I'd say that there's no audible difference in low-frequency performance between the two systems, and essentially no difference in mid or high frequency presentation when listening at a distance of 15 feet or more.

 

I'm in agreement after several weeks of listening.  I simply can't tell the difference between the two.  

[Giorgio AR]

Another AR58s conversion using the AR92 crossover: you got it right, unfortunately I managed to buy a pair of AR92 crossovers!
Thanks to all the schematics of our beloved AR speakers published on CSP I am modifying these crossovers to make them identical to the AR91 ones. The 1.37 mH coil (different in the AR92 crossover) comes from the original AR58s crossover, always the same source for the 2ohm and 22w resistor, to also add the missing 40uF capacitor in this board and then wire everything correctly.
As a replacement for the capacitors I will use bipolar electrolytics in the sizes of 40uf and 100uf, PIO to replace the remaining capacitors.
I am attaching the photo of the provisional test arrangement of a crossover in the AR58s cabinet and a second photo showing one speaker with original mids and tws, the other with mids and tws from AR10 / 11 MK2, to the right of this cabinet is also the AR10 / 11 woofer, in front of this woofer the box containing the NOS CCCP PIO capacitors (the box contains 42 capacitors that I will need to renew the AR78LS and AR2a torque crossovers too) .I have long wanted this modification on the AR58s for being able to attenuate the medium / high range and thus bring it to be more similar to the sound of the AR3a, the cabinet with the AR10 / 11 speakers, when the crossovers are finished and working, will help me to grasp the differences between the two series of woofers, mid. and tw.
Like all my projects, the realization will not be in a short time, but I will update the report of the continuation of the work over time!

P.S. The coils present in the AR58s and AR92 crossovers have the thick 18ga cable if I'm not mistaken, but the two small .2mH coils, despite having the same values in both crossovers, in that of AR58s, the wire is much thinner! As soon as I can I will publish the photos to see the differences with the diameter measurements in mm. of the wires.

 

[dna]

Several posts here give me questions, AR 91, AR 92 ? Was there a 92 or is this a typo? "ARs "best switches"? I know quality components should always be used but the "quality" of the switch? What "quality" is being refereed to? Does one switch turn off and on better than another of equal quality?

Did AR spec out a certain way to stuff the "cotton" in the enclosure; a fold VS. a wrap up?

I found the gasket in the 12 driver broken into several pieces all about 3" to 5" I used some speaker gasket foam I purchased for the 17s; the speaker mounting screws went conveniently right through the foam; but where could I find some original gaskets or should I used that putty AR once used?

I was thinking about adding the switches that are on the 91 model; comments?

By the way they really sound great!

[Giorgio AR]

54 minutes ago, dna said:

AR 91, AR 92 ? Was there a 92 or is this a typo?

The masonite crossover board bears the wording AR91 AR92, but even if common to the two models, the specific one for AR91 has different woofer coils, a capacitor and an additional resistor, all the other components are common to the two models.
On my AR58s I mount an AR92 board modified to make it right for AR91 (I used the original AR58s coil on the AR92 board, I have to add the 40uF capacitor and 2 ohm 22watt resistor to replicate the correct AR91 crossover with the AR92 board!

[lARrybody]

On 2/27/2022 at 11:50 AM, dna said:

By the way they really sound great!

Yes, yes they do sound great.

AR91 boards with upgraded switches, binding post, capacitors and resisters.

[DavidR]

Beautiful work Larry. Neat and tidy.

[ar_pro]

This man knows his way around a crossover. 

[DavidR]

I'm wondering if he's happy having (what looks like) used NPE (except for the 4uF). I beginning to think this might be best for the old ARs to sound like they were intended to. I used NPE in my 90s and 10Pi rebuilds with a small poly cap in parallel on the series caps and am very happy with those results.