Stimpy

There is an extra inductor in there...! AR-90

AR-9

I believe the AR-9 schematic, that listed a 6.0uF cap on the UMR, was in error. Both the 9 and 90, should use the 8.0uF capacitor.

My wife used to have TSW 410s. A great speaker, with good dynamics. A more lively sound, with a slightly hotter high end, than our AR 9 variants. Well, the 100uF Solen film cap would run over $55 dollars each. So, you'd spend quite a bit just to replace those 2 shunt caps. NPE's are fine there.

Good luck with the Classe preamp. I know a little Acurus L10 preamp really did wonders for my system, so I would think the SSP25 would be much better...!

I've never heard the 91s, but I do have 92s, and the 91s bookshelf twin, the 58S speakers. And I agree with David, that they're a great find, and I'm sure they're wonderful. Nice locating a recapped pair too. Plus, I wouldn't worry too much about the original 100uF electrolytic capacitor. It's a Unicon brand cap, and they tended to last much longer that some other brands that AR used back then. A Japanese manufactured capacitor, that sounds very good as well.

Parts Connexion just changed their website. It's now Audio-Connexion. The new site isn't as easy to navigate, and it's more geared to audio equipment, and not parts. Parts Connexion now requires clicking on a link, within Audio-Connexion...! The PC site has been "updated" too, and not for the better. But, at least the same parts brands are there, they just take a little more effort to find...! Edit: The new AC/PC site is very buggy. I can't even log into my existing account, to double-check the details of a previous parts order...!

Here's a repost of the North Creek file. Hope it works...! the art of bypassing.pdf

The 90s have a fairly low impedance dip in the bass. Around 3.2 Ohms down there. Just where you're hearing issues. So, look for high current amps, that can handle low impedances. That's not necessarily high wattage amps.

Those are final version of the AR-17's, from the High Resolution Series, and they do look correct. AR17 Specs

I've mentioned before, when I used my 90s in a HT surround system, my Yamaha AVR identified my 90s as being out of phase. Allowing the Yamaha to correct the issue, resulted in much better bass, with better balance to the rest of the speaker. At the time, my 90s were straight stock, purchased direct from the factory. So, I've always wondered if my woofers were mis-wired out of phase, when built?

My 90's (bought direct from the factory, around '81) have the adjustment resistors mounted on a separate board. But, a pair of back up 90 crossovers I have, that I sourced from eBay, have the resistors soldered directly to the switches.

A shame the Unicon capacitors aren't still available. Great sounding NPEs. Very dynamic.

Alcaps come in some good AR values; with 6, 8, 30, 40, and 80uF caps. If you eventually try some, I'd love to hear about your impressions.

I like bypass capacitors too. I use them on all values, series and shunt caps. Bypass caps seem to smooth out the sound, while still Improving detail retrieval. Oh, HiFi Collective and Falcon Acoustics, both in the UK, are good sources of capacitors. They could be useful for future projects. Good luck.

I've followed the techniques in this video, and didn't have to remove the center dust cap. Actually, with my M&K sub refoam, shimming the voice coil, still left a rub. Following the advise in the Simply Speakers video worked even better, since I could adjust the centering by feel. Simply Speakers Refoaming Technique

For what it's worth, M.D.L. looks to be it's own company; a Taiwanese manufacturer. M.D.L. Products

From what I've read, the owner passed away, and the family didn't want to carry on with the business. Now, it seems the Erse name is Chinese owned. I'm not sure if that means parts from the old Erse facility, or from China? Edit: After a quick search, it seems the former Esre employees have started US Coils. They look to provide many of the same components once supplied by Erse. Good news, I hope? US Coils

I agree 100%. The stock Unicon capacitors, in my AR58S speakers, still sounded great. But, out of caution, I replaced them. It took quite a bit of money, towards very decent poly caps, to improve upon the Unicon caps. I wish those caps were still made, as they would be my go to NPE.

Also, don't discount the use of bypass capacitors. A small value (0.10 or 0.01uF) poly film cap, in parallel with the NPE, can really open up and improve the sound of the electrolytic capacitors. They've been mentioned here, and aren't expensive. The Dayton film & foil bypass caps, that I use, are around a $1.00 each. Very affordable to try.

I am definitely a fan of Mundorf caps. Their E-Caps too. But, hang onto what you've ordered, and when you feel there's a true need for an upgrade, you'll have the parts at hand.

My AR58S speakers came stock with Unicon caps. The sound quality was still very acceptable. Actually, very dynamic in tone. I did a recap, for safety's sake, but truth be told, the Unicon's were equivelent to the poly caps I used. It would take boutique level capacitors to better the stock caps, IMO. Oh, the Callins capacitors in my AR90's, were horrible before a recap. Rolled off, muted, and distorted. The AR58S Unicon's exhibited none of those issues. Good luck.

Falcon has Alcap 7uF caps, to parallel for the 14s. A 20 as well, so nothing extra needed there. Plus, if the old capacitor leads are long enough, just clip the old caps off, and solder the new caps using the old leads. Alcap

Since you're in the UK, I'd use Falcon Acoustics. They're UK based too, and offer their well respected Alcap brand. The Alcaps are available in tight tolerances too, for a NPE.

Those four screws hold the faceplate and tweeter diaphragm together and in alignment. If you want to clean them up, only remove one screw at a time, so nothing shifts out of place. Capacitors can be daunting. Hard to decide how to replace, and with what? I used poly for the series values, (4, 6, 24, and 80), and NPE for the rest (8, 30, 40, and 350), to save a little money. You'll most likely have to bundle 2 caps in parallel, to add up to the needed values. That's unfortunately a common solution. Good capacitors can be found at Parts Express, Parts Connexion, Madisound, Meniscus Audio, and Sonic Craft. Prices vary, so be warned...!