Acoustic Research AR-2ax referb

[Powerglide]

I've been looking out for a set of tired vintage speakers to have a crack at refurbishing. I didn't want anything too flash but on the other hand pointless bringing something back that was never any good in the first place. Came close a couple of times with some British contenders but then a month ago these AR's were posted in need of attention. Knowing nothing about them, a quick google search revealed a somewhat cult following on the East Coast of the States and hard to find a bad review, so I forked over my hard earned

 

 

 

 

 

 

The speakers presented OK for 45 years old, Drivers needed assessing with bass surrounds being the only visual issue. Someone before the previous owner had cut holes in the rear panels to access the crossover potentiometers and rewired them externally. A bit of research revealed this could be catastrophic as the design for the bass relies on the box being sealed, if the speakers have been driven hard the voice coil formers could have slammed into the magnets cracking the voice coils. 

 

 

I gingerly fired them up and went through the motions of testing all the drivers at low levels, to my relief the bass drivers were fine, the mids were said to be bulletproof, and I was surprised that the tweeters were sounding sweet also. One potentiometer was broken but the other 3 did as they were asked without crackle or dropouts. 

I selected a vocal track and increased the volume and it was apparent what all the fuss was about, I had a poor source and an average amp but new these speakers were worth saving and setting up properly.

 

Bit of research and theses speakers were build cira 73 in Holland, having the removable grilles. Removed the drivers and crossovers, revealed that the tweeters had been replaced in 82

 

 

 

Sanded back the old lacquer and made a few repairs 

 

 

 

One speaker had lighter timber beads to the front that needed staining to match the American Black Walnut veneer 

 

 

 

sprayed a couple of coats of 25% gloss acid catalyst lacquer, final coats this morning, happy with the results 

 

 

 

 

began making new crossover boards today, I will be replacing the capacitors and adding L pad attenuators, swapping the terminal to gold bananas, hopefully the new bass surrounds arrive before Christmas. 

 

Al

 

 

 

 

 

Edited April 21, 2020 by Powerglide
Date correction

[MGO]

Great work on the cabinets Al.  They look like new.

[GregWormald]

Great work; and they should sound excellent when fully refurbished!

 

I bought a new pair of these sometime around 1970 and they were indeed superb for the time, and probably still very good when in good (or refurbished) condition. They were my introduction to quality sound. I took them to NZ with me and when I left I was able to sell them for the same price I paid--free listening for seven years!

 

 

Yes, the cabinets need to be sealed--these were one of the early acoustic suspension speakers (this construction was invented by the founders of AR) and the speakers depend on the sealing to provide the required suspension spring/damping. Without the cabinet the speaker suspension is very floppy. The lack of ports also makes them quite flexible in their placement. (I still prefer acoustic suspension speakers and find the SGR CX4F-2 delightful.)

 

BTW the ones I had did not have any beading around the front--so I would say the grill cloth was replaced earlier too.

 

Please keep us up to date on how it all goes. 

 

 

[Powerglide]

30 minutes ago, GregWormald said:

BTW the ones I had did not have any beading around the front--so I would say the grill cloth was replaced earlier too.

Hi Greg, I joined an AR forum in New England, there's a real East/West -Love/Hate thing going on, ie. don't mention JBL, anyway they have all the answers on AR vintage and restoration. 

Your old ones with the thick front edge had fixed grilles and probably ply backs, were pre cira 73 and were built in Massachusetts. The later beaded model had removable grilles and were built/assembled in Europe, England and Holland, I still have the original grilles 

 

 

I'm slowly getting all the crossover components together, just waiting on the L Pads from the US and some resistors for the mid range L Pads that apparently will make them perform more like they did off the factory floor. 

 

 

if anyone is interested the original Potentiometers were 16ohm - 25w the new Attenuators are 8ohm - 15w, mids will run through a 25ohm - 10w resistor  

New woofer surrounds arrived on Friday so I'm going to give them a crack tomorrow

 

 

[Powerglide]

Had my first crack at replacing a set of surrounds. Nothing too daunting, a few you tube tutorials to get some pointers. Pretty basic, but still I learnt a little more about the music chain, nothing like pulling something apart to cement how it works.

 

46 year old crusty surrounds 

 

removed 

 

 

old glue removed 

 

 

new surrounds fitted

 

 

can recomend Queensland Speaker Repairs for these surrounds and the bostik glue they supplied was great and easy to use, but the applicator was a hassle, needed an extra hand to keep the glue flowing.

 

 

I didn't use the shim method, coils aligned perfectly once the cones were glued. I probably didn't need to but I ran a tone generator through the speaker at 50Hz to double check. Can share the App if interested PM me.

 

 

 

 

Edited January 1, 2020 by Powerglide

[Powerglide]

Progess on my refurb 

 

freshened up the faces with a matt black enamel chalkboard paint

 

 

because my pots had been savagely cut out from the rear I made complete new crossover boards from black acrylic. I have access to a digital printer so I took a photo off the net of the rear panel text and had it converted to a vector file for printing. I had no accurate measurements of the L Pad location but it looks pretty good

 

 

I put a matt laminate film over the vinyl sticker after I applied it to the acrylic

 

 

With the new L Pads installed apparently the mids perform more to the original with these resistors fitted 

 

 

Finished off the cross overs

 

 

 

This design of AR's relies on a sealed box, I ran a thick bead of Sikaflex around the terminal opening to create a gasket 

 

 

rear view 

 

 

 

got to do a little trouble shooting on one of the bass drivers, everything else is working which hopefully means my first solider job is OK even if it's not that pretty 

 

 

 

[robmid]

Brilliant work! You must have great patience.

They certainly look like they will sound incredible.

Cheers, Rob

[Powerglide]

Thanks Rob,

 

had a little teaser today, I'm taking some flack files and a DAC in to work tomorrow, hopefully I can sort this woofer out and crank them both up 

[Powerglide]

Sorted my Bass driver issue and restuffed the cabinets 

 

 

 

finally got to open them up and for what they are they sound great, the first thing you notice is the amount of bass they possess for a small bookshelf. 

 

 

Looking forward to putting them against something else in a proper room with better gear.

 

 

super happy with the results, thanks to @evil c for his advice and original comments about these speakers that sparked my interest,@MGO for the cap selection's and candid comments about my lack of soldering skills, hey sometimes ugly can work too! 

 

[evil c]

@Powerglide been watching your AR rebuild project with interest - haven't needed to comment as you have surpassed my level when I rebuilt my pair of AR2ax .

Credit to your dedication and professional manner, one of the best results I've seen!

[Timepop]

Hi Al, I haven't really been on over Christmas/New Year and somehow completely missed the message you sent me earlier about these. Absolutely fantastic to see your restoration - the end result looks brilliant.

 

Really puts a smile on my face seeing them get the care they deserve.

[Powerglide]

Thanks @Timepop surprisingly the most work, or should I say time, was in the research around getting the correct attenuators and understanding wiring the caps. It looks like pretty simple stuff but for a first timer there's still a few wires that could have gone wrong.

One thing that was a bit confusing is the bass woofer is wired reversed polarity to the other drivers, so the most basic rule is broken, negative is connected to positive inside the box. 

 

Ive had them home now for a few weeks and it took a few different line ups to get the best out of them. Maybe the mids and tweeters have deteriorated somewhat but I found it hard to get some life out of them with my mainstay vinyl set up, they are heaps brighter through digital. I have 3 Amps, two TT's and two Phono stages so plenty of combo's later and the best for vinyl was 

 

Ortofon Rohmann with ruby cantilever - Sansui SR525 - Exposure XXVI - Cambridge Audio Azur 351r 

 

They are definitely a great listen, and when you dedicate an entire evening to them they have moments of brilliance, they perform well with blues and vocal tracks, they especially like layered seventies soft/folk rock, Steely Dan, Little Feat, Allman Brothers, Fleetwood Mac, CSNY ect. 

I find them a little too polite for heavier rock and the separation is not quite there for Floyd and detailed modern recordings, which is why I think the mids and highs could be a little fatigued (not that I've ever heard another pair) All that said I could easily live with them but for a set of 4313b's prowling in the background, not that there was a contest but even my listerning companion agreed the JBL's are from a different league. 

 

 

 

 

 

[5L15]

@Powerglide I’m speechless, that is “beautiful work” you did there and your photography is to be commended too.

This thread put a smile on my face for sure, Thank you 

[Powerglide]

Thought I'd post the last finishing touches made to the 2ax's 

 

The original glass wool was a mismatch of two different products and one was showing signs of breaking down so I replaced both with a more Eco friendly earth wool, the given specs was by weight which I converted to volume as the wool is lighter. Apparently there was a barrier cloth between the glass wool and the bass woofer which was prone to deterioration, mine was nonexistent so I cut a piece from some agriculture cloth I had.

 

 

 

I also decided to replace the tweeters, there are no NOS and only recently has someone perfected rebuilding original ones, they are not doing them on a commercial basis and I bet the price would be OTT. Anyway settled on these Hi-Vi Research which kind of bolt straight in. 

 

 

The Accoustic Research brains trust approve of the Hi-Vi's but recommend a mod to make them sound more like the originals by adding an external coil to the rear. Another parallel resistor (like the mids) makes the L-pads perform more like the original potentiometer did. The cardboard shim eliminates any bare wire contact. Had to ream out the factory mounting holes to take the original M8's and modify the cabinets slightly for the front connections, latter models were wired internally, which I could have done. 

 

 

I found some smaller knobs for the L-Pads and fitted them off 

 

 

Happy with the new tweeters, I made some earlier comments on what they could and couldn't do, I was wrong!

They like a lot of power for their best and I subjectivity prefer they heavier bass from my Benz Wood.

They handle most music but in my opinion excel with reggae, anything with a big smooth bass and do strings exceptionally well, I stand by my "they are not rock speakers" comment. They are very mellow and the more I listen the more I understand peoples loyalty to the brand. Well worth the effort and enjoyed the process so much that I've purchased something new to restore