AR38S restoration on a dime.

[graham]

Hi All,    I recently saw a pair of AR38S at auction in very rough shape.  Left behind a written bid of $12.  Was called later to be told I had got them for $10. I should have attended, I bet mine was the only bid, and If I had been there I would have probably got them for $2 !.  I intend these to be a basement workshop pair, so I was not going to spend out on audiophile quality repair components. I decided to restore them on a dime.  The woofers both needed a re-foam.  I also decided to replace the 6uf 50v BP caps.  I got a pair of generic 10" woofer foams from aliexpress, $3 the pair.  Also from aliexpress,  I got 6uf 50v Bipolar capacitors which came in a packet of 30 for $6.33.   They are radial instead of the original axial, but I don't see it would matter. Following are the photos before and after.

Yes I should have snipped out a small "V" from the foam where the screw holes go, but I forgot. When tightening the screws I was very careful not to rip into the foam by over-tightening.  The original foam went underneath the woofer cone edge ( which is why it looks so clean from the top ).  I glued the new woofers on top of the woofer cone edge. ( Is that acceptable? they work great).  I also glued the foam directly to the speaker metal casing - is that acceptable?  will it cause problems down the road? Anyhow they sound great -  $10 + $3 + $6 = $19 for a pair of restored AR38S'. Comments? Kudos? Brickbats? questions?

As purchased - both woofer foams completely disintergrated

[ra.ra]

As you've already mentioned, axial lead caps are far more common in speaker crossovers, but I suspect your choice should work fine. My choices for components would have most likely been different, but that's partly because I tend not to use Alibaba, and partly because I wouldn't know what to do with twenty-eight extra 6uF electrolytic caps!   Getting $1 in change back from your Andrew Jackson, you got one heckuva bargain in assembling those speakers.      

The smaller AR-18 and AR-18s are very fine loudspeakers, and at one time they developed a mini-cult status among professional studios for near field monitors. I would suspect the 38s model is essentially a beefed-up extension of the 18s, and in this 1981 NYT review it was hailed as among the best "bang-for-buck" loudspeakers on the market.

https://www.nytimes.com/1981/04/26/arts/sound-the-best-loudspeaker-for-the-money.html

What's got me curious now is thinking about the evolution of AR's 10-inch two way speaker models, which more or less followed a progression of: AR-2x ⟶ AR-8 ⟶ AR-14 ⟶ AR-38s. Of this bunch, the AR-14 might be considered "the pick of the litter" due to that wonderful tweeter, more complex crossover and beautiful cabinet; but I guess I'm mostly curious about the similarities and differences (in performance and perception) between the AR-8 and the AR-38s. Slightly different woofers, yes, but similar cabinet volume, cheap vinyl wrapper, simple crossover, and 1-1/4 cone tweeter. List price: $139 for AR-8 circa 1973; $150 for AR-38s circa 1981. 

The AR-8 was not a bad loudspeaker at all, but it has come to represent the bloody nadir from the "Classic" years of AR and was basically a dud in the marketplace. With so many similarities between the AR-8 and AR-38s, how did this generic speaker formula (10" two-way bookshelf) go from failure (AR-8) to moderate success (AR-38s) over a period of 8 years or so? 

[graham]

I have now listened to about 30 CD's , played through the AR38S,  and the sound is seems to get better and better, particularly after the first 10.  These are good quality speakers, nice bass and lots of definition on the higher notes. Not top of the line audiophile quality, but certainly in the very good category,  and can look down from a great height upon the majority of squawk boxes in mainstream use today.   Some of my listening list are:-  The gentler side of John Coltrane,  The very best of Albert King ,  Compact Jazz by Harry James,  and  Chet Baker Jazz Masters 32.  From the brushing of the drums , shining ambience of the cymbals,  deep low pitch of the  double base,   the trumpets and the saxophones,  all come out clear and warm on the A38S;s.   My next project is to rebuild 2 sets of AR4X, After that I will feel confident to move on to a pair of AR9I   which I picked up at auction about 8 years back for just $79 + premium and tax. The foam is in good shape, so I will likely just rebuild the crossovers.  For the AR91  I will go for audiophile quality caps. 

[Pete B]

Those tiny NPE's probably have very high ESR (some are 2-3 ohms and not intended for crossovers)

it might tone down an otherwise hot high end - don't know never heard these speakers.

[graham]

2 hours ago, Pete B said:

Those tiny NPE's probably have very high ESR (some are 2-3 ohms and not intended for crossovers)

it might tone down an otherwise hot high end - don't know never heard these speakers.

Thanks for the comment Pete.    Yes NP caps do look small in comparison with the originals.

I did not find an   ESR ( equivalent series resistance) ohms value quoted for my capacitors or for  a couple of well known brands I looked at.

The originals were Unicorn 6uf 50v made in Japan  Bi-polar   size  0.5" x 1.12"

Mine are Japan Chemical BP Series 6uF/50V 10% (on behalf of 5.6uF/6.8uF) (K) 85 C.  $6.33 for packet of 30.  size 0.25" x  0.5"

I looked at what I could have got in axial with a well known brand name.

packet of 4  SPRAGUE for $12.84.     5.6uF 50V DC solid-electrolyte Tantalex capacitor. Hermetically sealed, axial solid tinned nickel terminals. Case Code: R   The size of these is 0.28"  x  0.68"     or a packet of 2 SIEMENS for $13.98,   still sized at 0.28"  x  0.68"

So mine are practically the size as the recognized brand name ones, if size has anything to do with the ESR ohms resistance. 

 I guess measuring the ESR would be the next step? I have an elenco M2795 multimeter but not sure if it can measure a capacitors ESR?

 

[Pete B]

No a multimeter won't do it.

If they sound good I wouldn't worry about it, just something to note.

Nice to see it done so economically.