VinylChef

A birdy told me that at some stage you have supplied replacement AR11 grilles. I've no idea whether this is just slander, or a bastion of hope. Can you confirm?

No worries. I think I misinterpreted your post. All good!

Thanks everyone for their input!

Hi Giorgio, I have a spare LST bass driver, if you are looking to acquire an original. David

I have been slowly restoring a pair of later model LST's, including recapping the crossover. Despite being advised that I would not experience any material benefit by replacing the old resistors (I haven't done this previously), I decided to anyway! As I did this, I thought it would be interesting to check all the old components as I replaced them. Most of the electro caps were quite good, apart from one that was about 25% out. But what surprised me was the oddly named King Wahoo 10ohm resistor, which read 19ohm. My questions are: Is this a rare occurrence? Would such a large variation in Rs manifest in any audible or practical way? If so, what? Is there any point replacing resistors? (I'm wooed by the idea of fancy 'audiophile' resistors but sense that this is not because they are any better, but because ignorant hobbyists like me are suckers for that kind of marketing.)

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. Regards, David

Hi, 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: 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: Can anyone identify the mystery woofer? Is it okay to use different vintage drivers for the two LST speakers? Would I hear a difference? Recommendations for which ones to use? Thanks a lot for your help! David

Hi Rjr, Thanks very much for the feedback. All great points and well considered! I'm having 8 LST tweeters refurbed by Chris1This1 in New Jersey at the moment and he also said that these LST-2 tweeters I've been given will inevitably need restoration by him or someone like him. So yeah, I can understand that buying a tweeter, shipping it to the US, just to then spend money on restoring it would sound unrealistically expensive. Shipping cost, not for your information, but for others who may be reading, was USD$110 for 8 tweeters from Aus to US. So yeah, maybe about USD$30-$35 for 2... I'll definitely chuck them on ebay to see how they go there. I've also got 7 original AR3a/LST midranges and 1 original LST bass driver to find homes for! Cheers, David

Can anyone tell me why there is no interest in these at all? Is it because few people need new/old tweeters because they have their own ones restored? I'd rather not throw these in the bin, but if there is no desire for them... Thanks!

I have for sale 8 x original 8 ohm tweeters that suit the above Acoustic Research models. Being still in their original packaging, these tweeters appear to have been never seen any action. The previous owner is not aware of these ever being used either and have been in storage for several decades. Visually, they appear to be in excellent condition, with no apparent wear or damage. When put across the DMM, most of the tweeters read between 5 and 7 ohms, with a couple between 3 and 5 ohms, with none showing infinite resistance. Please note, I have not tested these in a speaker, so I cannot guarantee that tweeters of such vintage may not have other internal problems, and for complete assurance I'd recommend getting chris1this1 or RoyC (both great guys on the AR pages) to rebuild or at least check them (this will be easier for US-based peeps). I'm finding it hard to find pricing, so perhaps let me know if you are interested and we can work out a price. Obviously if you wish to take a larger amount off me we can factor that in. I'm based in Sydney, Australia, so shipping may be horrible. Then again, I shipped 8 tweeters to New Jersey today and they cost a total of USD$90 only.

Thanks. I assume such a fluid, being an oil, will never 'dry up', so to speak. And it would not fall out as it is suspended by the magnetic field produced by the speaker magnet. Perhaps it changes, much like a cooking oil may become rancid and sticky etc.

Thanks, David, for the brochure snapshot. I took apart a tweeter just now and when I inserted a small piece of paper in the gap where the voice coil sits it definitely came out with fluid on it! How do I know whether it needs replacing?

Not on mine. Then again, when I took mine apart I wasn't even aware they had ferrofluid in them! The speakers must be, what, 40 years old now, so can I assume the removal of any old ferrofluid and the addition of fresh ferrofluid is either ideal for optimum performance, or crucial for the safe running of the tweeters?

Thanks Stimpy for taking the time to research those options. I have actually already bought a tweeter from someone in the US to replace my one with the crumpled dome. So I've a complete set now and my speakers are up and running (with new caps, surrounds and posts etc too). The reason I was suggesting the OP could provide a dome for my otherwise working tweeter was so that I would not have to waste the parts and could donate the complete tweeter out to the community.

Hi Sudhir, Thanks for your reply. I appreciate your recommendation of the Mylar Dome Tweeter replacements, but I'd rather try and stick to original parts. I am considering trying to salvage a good dome to put into my working tweeter. Do you need your dome anymore if you are moving to new tweeters? If not, maybe we can work something out? I did not even realise that these tweeters had ferrofluid! Can I assume that the fluid has to be put into the place where I have put a black arrow in the attached picture? Do you think that this product would be sufficient for two of these particular tweeters: https://www.parts-express.com/Ferrofluid-650uL-General-Purpose-for-2-Diameter-V.C.-340-544 Thanks for your help! David