What type of capacitors should I put in my AR-90s?

[blastinbill1]

Thanks for the advice Rich. I was going to leave the coils and wires anyway. The resistors on the switches are already out. The replacement caps will be a mixture of NP electrolytics for the midranges and metallized polys and mylars from PE and Madisound.

Billy

[blastinbill1]

I finished the recapping the AR90's last night, except for the two 350uf capacitors in the woofer section, which I left in for now. For the 80 uf capacitors in the lower midranges, I ordered a pair of 80uf NPE's from both Madisound and PE. The pair from PE measured about 87-8 uf, and the pair from Madisound measured about 85-86uf, so they were not used. Surprisingly, I was able to meausure 78uf out of parallelling a 47uf and a 22uf, both from PE, which actually measured 54uf and 24uf, respectively! Out of all the various NPE's ordered from PE, all measured from about 3 to 15% high, and the ones from Madisound also measured high, but stayed below 10%.

In summary, I used Dayton (PE) metallized polys for the 4 uf in the tweeter, Carli (Madisound) mylars for the other 6 uf in the tweeter and the 8 uf in the upper midrange, and a combination of Dayton (PE) and Bennic (Madisound) NPE's everywhere else (except for woofer section capacitors, which were not changed). All installed replacement caps or combination of caps were within 6% of AR90 schematic stated values. All equalization switches left in but electrically bypassed. The 8 inch sealed chambers were checked for leaks (none found) and resealed with RTV, as were the lower inside edges and corners of each speaker tower. One 7"x7" piece of "egg-crate" acoustic foam from PE was glued to the inside front surface of each speaker tower above the lower crossover board. All solder connections were checked for continuity, and drivers installed.

First impressions of both speakers (no before and after A/B comparisons) with FM music and a known CD is that they sound no worse than before and seem to have a little more output in the higher ranges, but this is only an initial subjective observation on my part. Although 6 out of 16 of the original capacitors measured more than 10% off from the schematic values, the speakers didn't sound bad before the recap, and they certainly didn't get worse, but I can't objectively say they are "better". I think I now have more "piece of mind" that this is close to the way they sounded when new, which was always a seemless, uncolored, non-fatiguing sound. To paraphrase Julian Hirsch in his review of big brother AR9 in May 1978 Stereo Review, there may be other exotic speakers that perform better in one single area, but none that do all the things as well as the AR9 (and the similar AR90, I would assume).

[JKent]

blastinbill1,

You may be fretting needlessly about the tolerances of electrolytics. When I recapped my MAC4100 receiver it had two big 12,000uF electrolytics. The originals are marked "12000UF -10 +75%". I've heard from other sources that within 75% is close enough. So yes--your recap probably sounds "no worse" than before but you've given the speakers an extension on their life span, and hopefully had some fun.

Kent