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Restore early (ish) AR-5 pair


JCinLA
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Hi folks

I acquired an original pair of AR-5s from an estate recently. Removed badges then determined that the grilles were not going to go quietly. (they were never coming off intact, tried all the tricks, oh well).  So I hooked them up to my Pioneer SX-980 and queued up Miles on my Yamaha PX3 table with Denon DL-103 MC cart and Denon AU-300LC step-up transformer. A nice simple setup, nothing fancy here.

First impressions: slowly increased the volume realizing they appear to be quite inefficient compared to my 1970s JBL Century L100s.  Also less efficient compared to my 1960 pair of fairly rare EMI DLS-529x, which are 4 ohm loudspeakers. Once I reached my normal listening volume level (probably on the high side because my listening ‘room’ is a large commercial loft space), I was actually blown away! At first, I thought they might be good to go as is. No, then at low volume I started to hear some woofer distortion sounds. Turning the rear knobs revealed scratchy noise and dead spots.  So that ended the testing session.

Observations:

1) Having to turn the volume up to near 3/4s was a surprise. Both other pairs mentioned above are never above 1/2.  Is this due to the aging electronics in these AR-5s? My presumption is that may change somewhat after a restore.

2) Got to get these fixed up and amazing potential!

After studying much of the AR-5 related content here, I decided to try a restoration myself even though I have no real expertise. I have only rudimentary knowledge and just enough hand tools to be dangerous.

I have (successfully) restored some cars, motorcycles a lot of mid-century-modern furniture and did a few basic clean up duties on the above vintage HIFI units.

I plan on contributing this process to the forum here, mostly with photos and documenting what may be useful to others.  It also appears that good documentation of original AR-5s may be helpful for the knowledge base here in general (hopefully I’ll contribute something worthwhile).  Any observations are encouraged and I’ll be asking for a bit of help along the way.

James

Sorry for the long-winded opening post.

photos to follow 

 

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First look photos and after opening the first one:

Some observations/comments:

Dated woofer:  Feb 19, 1970

Stuffing shown as I found it.

Red marker X on basket showing Pos. (not tested yet)

Other Red marker ‘marks’ on magnet:    ‘2’ ??

8 mounting holes on basket/ only 4 used

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That's a nice find; the AR-5 is a very well-regarded, but somewhat rare bird.

With rotted surrounds, typically bad level controls, and aged foam-suspension tweeters, there's no way in the world that the speakers can be properly tested or evaluated. Hopefully, the woofers are still OK after being driven without surrounds.

If you haven't already, carefully read Restoring The AR-3a; everything in this document is applicable to your AR-5 speakers:

https://www.classicspeakerpages.net/library/acoustic_research/original_models_1954-1974/original_models_schematicss/restoring_the_ar-3a/restoring_the_ar-3a_full_pd.pdf

 

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The serial numbers and dates on the woofers show these to be early specimens constructed in the first year of manufacture. Approximately 50,000 were manufactured.

Roy

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Great find, very impressive speakers when restored.  A key point from AR_Pro is the speakers should not be used until they are restored to avoid further damage.

The foam surrounds on the woofer hold the speaker coil in careful alignment to the magnet surrounding it.  Without foam the coil will scrape against the metal causing damage which is difficult to repair.  Think of a piston which is cushioned by air within a cylinder where the surfaces should be close, but never touch.  No foam means the surfaces can touch.  A little use, maybe no issue.  A lot of use without foams leads to scraping of the voice coil, leading to more extensive repairs...

Take your time, ask lots of questions, and you too can become one the forum members with great pictures and stories shared about your restoration. 

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7 hours ago, ar_pro said:

That's a nice find; the AR-5 is a very well-regarded, but somewhat rare bird.

With rotted surrounds, typically bad level controls, and aged foam-suspension tweeters, there's no way in the world that the speakers can be properly tested or evaluated. Hopefully, the woofers are still OK after being driven without surrounds.

If you haven't already, carefully read Restoring The AR-3a; everything in this document is applicable to your AR-5 speakers:

https://www.classicspeakerpages.net/library/acoustic_research/original_models_1954-1974/original_models_schematicss/restoring_the_ar-3a/restoring_the_ar-3a_full_pd.pdf

 

 

2 hours ago, briodo said:

Great find, very impressive speakers when restored.  A key point from AR_Pro is the speakers should not be used until they are restored to avoid further damage.

The foam surrounds on the woofer hold the speaker coil in careful alignment to the magnet surrounding it.  Without foam the coil will scrape against the metal causing damage which is difficult to repair.  Think of a piston which is cushioned by air within a cylinder where the surfaces should be close, but never touch.  No foam means the surfaces can touch.  A little use, maybe no issue.  A lot of use without foams leads to scraping of the voice coil, leading to more extensive repairs...

Take your time, ask lots of questions, and you too can become one the forum members with great pictures and stories shared about your restoration. 

Oops my bad! I should not have test driven them as you both have correctly pointed out.  Thank you for that!

Also thanks for the encouragement!

 

4 hours ago, RoyC said:

The serial numbers and dates on the woofers show these to be early specimens constructed in the first year of manufacture. Approximately 50,000 were manufactured.

Roy

Wow that’s something!

Thank you for that info, Roy!

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Moving along…

Photos of the second AR-5 speaker (serial No. 12410)and a few additional detail photos of both speakers (now identified by serial No.)

Observations:

Woofer also dated February 1970.

This one has 4 mounting holes. (whereas the previous speaker serial No. 12843 has 8 mounting holes).

What does this mean?

Probably not too much; In February 1970 they were simultaneously using both the 8-hole and the 4-hole basket for AR-5s. Also slight differences in the terminal connectors.

Both woofers appear to be usable and are now cleaned up ready for refoaming.

 

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