hipmomk

Good luck with the AR-90's. Like all vintage AR's of the 70's, they like a lot of good clean power by an amp comfortable handling complex and low impedances (like your 1.0 mk2). More power is much better than not enough power. I happen to have a set of AR9's & AR90's, and are very happy with both. The 9's will go slightly deeper, but he 90's are no slouch. From lower mid up, they are about the same, the 90's are easier to fit in a room. They will play very clean & loud, but do remember they are over 30 years old. They will probably take everything the 1.0 can dish out - but I am not suggesting constantly running the amp with the lights high up the scale, dynamic range is a funny thing, and even though the amp hasn't lit the headroom exhausted bit, it is probably already clipping a bit on consistently high volume playback. Mid & high range drivers don't like that, especially older ones. Couple of suggestions. You probably want to pull one of the side woofers out and see if the caps look original. These things are over 30 years old, and the drivers are getting rare. If the caps look to be original Spragues or worse Callins, or are the black and red things they really need to be replaced. The crossover network is very complex (side firing woofers intentionally are out of phase with the other drivers for one thing). Cap replacement is not fun but can be done with half ass skills, but it is tight in the cabinet. The tweeter midrange board is on the back of the cabinet, the woofer on the bottom. You really need to be concerned with the tweeter midrange caps, because original drivers are hard to get (replacements are available but don't quite sound the same), and old caps drift in values enough to overload drivers, or can short open and blow them. Being sealed in design, make sure the drivers have the gaskets on them and so on, it makes a difference. Have a good time, Joe

The woofer surround kits I mentioned above on eBay are really not that bad to install. I have done about 6 to 8 AR 12 inch woofers over the last 10 or 15 years, and am what I consider "medium handy" at these types of things. "M_Sound" includes voice coil shims and very good instructions. So if you are willing to put in "sweat equity" and do it yourself, you can do all of them including the midranges for around $125. You need an exacto knife and patience. Note that with acoustic suspension drivers, if you play at any kind of volume with junky surrounds you run the risk of (permanently) damaging the drivers, as the woofer spider is very compliant (or loose/sloppy) as compared to a bass/reflex type of design which will have a comparetively "stiff" spider. These drivers are essentially the same 12 inch drivers of the AR3, just updated slightly for higher power handling in the later 70's. Good thing about the AR9 vs AR3 is the AR9 driver connections are regular push on types versus the soldering required for the old AR speakers - so driver removal is a snap (just remember which color wire goes where). Joe

In their day (circa 78 -79) they were some of the best available, and widely considered AR's overall best speaker made - which is really quite a statement. AR invented acoustic suspension ("sealed") speakers - they are power hungry, would not use less than a MKII 1.0, 1.5, or 4.x series. They can be passively bi-amped with very good results, best to keep same type amp on woofers & the mid tweeter array for simplicity. The AR 12" woofer is pretty famous for being very flat at low frequencies, it is widely accepted the NHT1259 subwoofer driver prevalent in use in high end systems in the 80's & 90's was patterned off of it. The AR9 has two of them, with the lower bass response being very robust. One of the reasons it was considered AR's best was the woofers hand off to an 8 inch midbass driver, and then on the the usual AR dome midrange and tweeters of the era. – this solved lower midrange coloration of a big woofer handing off to cone midrange drivers. The negatives include the speakers are a pain in the ass to place in a room. They need to be against a wall about 5 or 6 feet apart with about another 5 feet or so to the corner wall - that's because of the side firing woofers. And of course, they are power hungry. They are a low impedance speaker, nominally rated at 4 ohms, but at various frequencies it can dip to 3 or 2, especially in the bass region, which can stress very good amps, even the Carvers. And they are over 30 years old. In the lower 48, they are very collectible, ranging from about $600 to $1500 depending on condition and luck - you got a good deal. M-Sound on eBay (Moonlistener) sells the correct foam surrounds - this is pretty important for the older AR stuff because the acoustic suspension principal requires very compliant surrounds in order to maintain their low frequency response - if I remember correctly the AR9 woofers are around 19hz FS. AR used very good quality caps in the crossover, only the tweeter array ones (somewhere around 6uf) should probably be replaced. The crossover is very complicated; don't bother thinking about a way to truly biamp by bypassing the internal crossover unless you are a rocket scientist. Drivers are becoming rarer and pricy so while playing loud is fine, be careful of playing demo records (1812 overture comes to mind) after several beers. In the day, AR made some of the better driver around, but again the speakers are over 30 years old now. Good find (I am a little jealous, have been looking to score a set in NJ for cheap for about 2 years now), have fun. Joe

I guess we are all as OCCD about speakers as Carver gear. AR-LST 2 sets of AR3A (one pair needs to have mids/hi's repaired and a recap) AR3 Empire Grenadier 9000 2 sets of Allison 3 (corner speakers) AR90's on the way Dayton subs HT390HF Allison 6's? in the attic Does a 1940's/50's vintaqe Jensen count (hasn't been out of the attic in 30 years Joe

On the cap replacement front, replacing caps is often an insurance policy, if one of the caps shorts, pop goes the tweeter, midrange, or worse. It is also possible that after the new caps “wear in” that it will improve sound quality and/or return the overall frequency response back to where it was designed to be, as you have mentioned cap values can change in 30 years. Highly unlikely inductors should be replaced, ones part of a well designed system (Polk) probably will not be improved upon dramatically. As a comment, a few years ago I replaced the caps in one of my AR-LST’s ( built ~1973) as a preventive measure, was a very tough job (well, for me) based on the way the x-over board was located… got busy, did not do the other. AR used high quality components, I was just afraid that one of the electrolytics would die while I was redlining my M1.5 during a party. If memory was correct, I used Solen’s for the mid, and a more esoteric cap for the tweets. Long story short, I think I would say that today, the speaker I changed the caps in is a little “brighter” than the one I didn’t, not that either can be criticized as being “dull”. I would not say there is a huge difference, but there is at least some difference. There was a big sprague that I missed on the schematic (~2500mfd) that was not replaced (no parts) as I had not done the proper research at the time. On the active crossover front, another good active crossover is the TDM Design series, TDM CX-2, CX-3, CX-4 (stereo 2 way, 3 way, 4 way). They have been sold both as pro & consumer, Madisound sold them at one time as their “Sledgehammer” active crossovers. They have the usual 24db Linkwitz alignment. Pretty easy to find on ePay for a reasonable amount, I picked up my CX-4 for less than $80. In my case, am only using for stereo subwoofers, normally a CX-2 would fill the bill. Note that the vast majority of the units are pro-sound oriented, meaning the connections will be XLR etc, which you can use with home audio with simple cable converters, I happened to get one of the comparatively less common RCA jack versions. If you decide to go the active route, you may want to keep in mind the existing crossover driver slopes of your speakers when shifting to an electronic crossover – many speakers used either 6db or 12db slopes because of the difficulty in designing a 24db slope in a passive (cap & coil) crossover. So it may sound a little different just because of the slope differences. You will also need to find a way to balance the relative volume of the tweeter section with midrange with woofer, etc – an equalizer with a RTA & mic (like above, I have a C-101) or some other PC RTA software. Just replacing the caps with good quality replacements is probably the best place to start – JMO of course. Joe