Acoustic reearch AR-2 Crossover Info?

rshadley · Nov 11, 2009

Can anybody lead me in the right direction for getting info on the AR-2 crossover as I would like to Recap mine. Thanks

rmeade · Nov 11, 2009

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=4467&st=0&p=74232&#entry74232

about half way down the page is a detailed diagram of the 2ax crossover

rshadley · Nov 11, 2009

Great info, but I have the original AR-2 with the two identical 5-1/2 mid tweeters and what appear to be four large metal capacitors(cant find the Uf rating) wired in series for both med-tweeters.

Zilch · Nov 11, 2009

Surely the info is available on Classic Speaker Pages somewhere.

If not, find the assembly manual for the Heathkit clones I built 50 years ago, AS-2 or something like that.

Tore into a pair in ZilchLab but didn't document the crossovers:

http://www.audiokarma.org/forums/showthread.php?t=153835

I can almost gurarantee that the paper-in-oil caps that were in them do not need replacing. Yeah, I still have them, but not the crossovers intact.... :dunno:

rshadley · Nov 11, 2009

I still have the full crossovers intact, had to open one cabinet to check one tweeter that was not working. Thought I might just replace them while I cleaned everything up.
Maybe I will just leave them as they highs are ok.

Zilch · Nov 11, 2009

If you post a pic of the crossover, I may be able to figure it out....

rshadley · Nov 11, 2009

The capacitors are gray and measure about 4" x 1" x 1-3/4" and are marked U4053-B on the top and just below that 1MFD + 1MFD.

spkrdtr · Nov 11, 2009

I worked on one of those quite some time ago. However, I can't remember the details. The caps were wired in some arrangement I believe, to add up to a target capacitance.
The two's have just the mids w/no tweeter and I suspect the final target was 6 uF.

I wouldn't want to try to get that cap/coil package by airport security though - yikes!

rshadley · Nov 14, 2009

Here is a diagram of the heath kit AS-2. What is the point of the 2Uf capacitor wired between the tweeter pot control? Some earlier info on the classic speaker page recommended the Dayton 6.2 Uf's for the recapping.

rmeade · Nov 16, 2009

Sorry about the mis-direction; here is a discussion about the 2a, including a schematic of the crossover arrangement.

http://www.mbzponton.org/n2awa/ar2a.html

I am suspect, though. You seem to indicate that you have fewer capacitors than outlined in the schematic - and the schematic treats the wiring on the separate potentiometers inconsistently.

And yet another discussion and hand drawn wiring diagram. http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=4513

Maybe I am wrong on the pot wiring - as both diagrams seem to agree.

Zilch · Nov 16, 2009

rmeade said:
Sorry about the mis-direction; here is a discussion about the 2a, including a schematic of the crossover arrangement.

Nope, still wrong; these are AR2, not AR2a, either, but it's instructive that both Vintage AR and AB Tech fail the restoration correctness test in those citations.

The AS-2 schematic is correct. The variable 0 - 15-Ohm resistance across 2 uF is both attenuation and response shaping at once, and quite clever, actually. Put it in Spice to see how it works.

Here's my two double-stacked 2 x 2 uF caps out of AR2s:

The bottom terminals are the commons, the two caps on the left of each stack plus the lower one on the right comprising 3 x 2 uF in parallel = 6 uf, and the upper right one the additional 2 uF across which the potentiometer wired as rheostat is connected.

Measurements and variance from spec:

A = 5.79 uF (-3.5%), 1.92 uF (-4.0%)
B = 5.83 uF (-2.8%), 2.09 uF (+4.5%)

Still want to recap? Use a 4uf and two 2 uF in each, the 4 uF and one 2 uF in parallel = 6 uF, and the second 2 uF in series with that pair having the 15-Ohm variable resistance across it as shown in the AS-2 schematic.... :thmbsp:

rshadley · Nov 21, 2009

Great stuff, just got my parts express order and i thought i had ordered 4 3Uf capacitors for the job. Received 8 and used all those in my B & W dm10's. Will get the 4Uf's and 2Uf's and recap.

Thanks Again

Dannyobee · Jun 20, 2020

rshadley said:
Great stuff, just got my parts express order and i thought i had ordered 4 3Uf capacitors for the job. Received 8 and used all those in my B & W dm10's. Will get the 4Uf's and 2Uf's and recap.

Thanks Again

Hello. I’ve been reading this thread because I have 2 AR-2’s I’m considering recapping. How did yours turn out? Any discernible differences in sound? Also, can you provide a sketch of what you did? Thanks!

RxDx · Jun 20, 2020

The oil caps typically don't go bad. I replaced the ones in mine, and there was no
discernible difference in sound.

What did make a big difference was replacing those dual "tweeters" with the single
midrange unit from the AR-2ax. That, of course, requires a mounting plate, but if you
listen to these any at all, it's worth the effort. It really transforms the sound. No change
to the crossover needed.

Dannyobee · Jun 20, 2020

RxDx said:
The oil caps typically don't go bad. I replaced the ones in mine, and there was no
discernible difference in sound.

What did make a big difference was replacing those dual "tweeters" with the single
midrange unit from the AR-2ax. That, of course, requires a mounting plate, but if you
listen to these any at all, it's worth the effort. It really transforms the sound. No change
to the crossover needed.

View attachment 1903308

Thanks a lot for the feedback!

Acoustic reearch AR-2 Crossover Info?

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