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AR LST/3a driver identification and advice


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I have been bestowed with two AR LST speakers, which I am determined to bring back up to scratch, and a whole heap of extra drivers. I'm trying to sort them out and work out what to keep and what to sell. I referred to the excellent Restoring the AR3a article to try and understand what I have before posting here.

I have 17 midranges in total:

  • 8 that I removed from the cabinets with 200010-1 and Made in USA labelled on the rear side, what looks like batch numbers (eg 561 7609) and a round stamp. The spongy material under the mesh is tan in colour and the mesh is black and I think they were manufactured from 1974-1976
  • 8 seemingly 'new' ones still in their original boxes. These also say 200010-1 on the rear but have silver mesh and darker material under the mesh. They also all have 'Service Replacement Unit' on a label on the rear side and I think they were manufactured from 1977-1980. According to the Restoring the AR-3a article, these were assembled with ferro-fluid immersed in the voice-coil area around the outside portion of the coil. (Does this make this a superior version of driver?)
  • 2 more ones identical to the replacement units, but without the 'Service Replacement Unit' sticker on the back

I'd like to keep 8 midranges for the LST's themselves, keep two additional ones in case I ever find some AR3a's to do up (or to keep in case I lose one or two in the LST's). And I'd like to sell the rest.

My question:

  1. Is there any difference either sonically or in regards to durability between the two models? Which ones should I keep?

I have 3 bass drivers in total:

  • 1 x with a 20003 label, pale metal basket on front and back and masonite shim flush with the edge of the surround
  • 1 x with a 20003-1 label with a square magnet, that I believe was manufactured between 1979 and 1983
  • 1 x unidentified. It has what looks to be 561 7633 stamped on the rear. It has a round magnet, black basket on front and pale metal on rear, masonite shim protruding about 8mm out from the edge of the surround, and a kind of wire mesh enveloping the basket.

My questions:

  1. Can anyone identify the mystery woofer?
  2. Is it okay to use different vintage drivers for the two LST speakers? Would I hear a difference?
  3. Recommendations for which ones to use?

Thanks a lot for your help!


Unknown AR woofer front.jpg

Unknown AR woofer rear.jpg

Unknown AR woofer corner rear.jpg

200003 woofer.jpg

2000031-1 woofer.jpg

LST replacement mid front.jpg

LST replacement mid rear.jpg

AR LST Orig. midrange corner.jpg

AR LST Orig. midrange front.jpg

LST original mid 1.jpg

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9 hours ago, VinylChef said:

My questions:

  1. Can anyone identify the mystery woofer?
  2. Is it okay to use different vintage drivers for the two LST speakers? Would I hear a difference?
  3. Recommendations for which ones to use?

Assuming they are in good shape, all three of the woofers have near identical performance.  There is no practical difference . The square magnet woofer is the latest version of the three.

Same for the mids: Assuming they are working correctly you won't hear a practical difference, they are essentially the same.

My recommendation would be to make sure every driver in your reassembled LSTs operates to your satisfaction before selling any spare parts.

You should replace the fuses with new ones even if the old ones appear to work.

If your LSTs have Sprague Compulytic caps throughout I would leave them.  If they have a mix that includes ICC wax box caps I would replace the ICCs.




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Hi Adams,

Thanks very much for your advice, especially cautioning me against selling spare parts too early; it would be ironic (and pretty stupid) to sell them all then find the ones I've kept aren't working!

I'll take a look at the crossover shortly to find out whether they feature the ICC caps.



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