My system is getting worse - now what?

Check with Tweeter, etc. They used to be a big ADS dealer. Maybe somebody still has some contacts. About a dozen years ago I blew out a pair of woofers in my 1987-era ADS 1090s (one generation after the 810), and my local repair shop (in Seattle) was able to replace them with OEM woofers. There are probably some companies around that specialize in rebuilding drivers for spares.

I believe Tweeters has gone out of business. I know the one in my town closed down about the same time Circuit City did.

05-08-09: Cleaneduphippy
I believe Tweeters has gone out of business. I know the one in my town closed down about the same time Circuit City did.

Oops. Missed out by just a few months.

Looks like the former ADS headquarters is occupied by American Florist Supply Inc.

I had a pair of L1090s that I bought new at the end of their run in 1987. Telarc used the flagship from this series, the 1590, as their monitors at the time. The 1090, 1290, and 1590 shared the same soft dome midrange and tweeter and dual woofers in a sealed cabinet. They varied by woofer diameter and cabinet volume. The 1590s had dual 10" woofers and reached pretty deep. The L1x90 series were preceded by the x10 series (e.g., 610, 710, 810) and followed by the M series such as the M10 and M12.

I also picked up a pair of near mint 810s for $100 and made them my rear channel speakers, as they had near identical mids and tweeters as my front L1090s. I experimented a bit with amplifiers and found that to get the most of the 1x90s or 810s, you needed a fairly powerful, fast, wide bandwidth high current amp that is comfortable into a fluctuating impedance. Telarc used Nelson Pass's Threshold Stasis amps at the time. I found nirvana with a used VSP Labs TransMOS SS amp making 200 wpc and lots of current--it weighed about 50 lbs. Today you can get good results with the more recent crop of wide bandwidth high current Mosfet power amps from Adcom such as the GFA-5400 and GFA-5500. These are fast and transparent, and have a nice liquid midrange and treble that mates well with the ADS dome midrange and tweeter.

Of course, it won't fix things if your voice coils are scraping. One thing to keep in mind, though, is that ADS built its drivers with very tight voice coil gap tolerances. They even built the machines to build the voice coils because nothing was available to maintain their tiny gap. My point is, you may hear a clink when tapping on an ADS bass driver even if there's nothing wrong with it. See if you an borrow an amp like I described and see if it gives you what you're looking for.

Johnny got a good point - your test procedure for woofer failure may not be valid? I'm going to try and describe how to test for a warped woofer voice coil. Let me make one point first : This is something you do to your speakers - YOURS - never ,ever do this to anyone else's . If you do this on someone's sales floor without first asking for permission - anticipate a violent physical assault on your person - which you richly deserve.In my 25 years in the industry I replaced dozens of drivers damaged by f#$%^&g idiots punching in domes or dustcaps on my demo speakers.Industrywide - you will find service people who have a real attitude about this kind of damage.
First off - this test procedure is only useful for woofers and a very few mid-bass/mid-range drivers that have a fair amount of excursion ( front and back motion).Most midranges and all tweeters that I am aware of will not tell you anything about their V/C condition with this test - you will however have a reasonable chance of permanently damaging them by sticking your fingers into them.
All we are trying to do here is feel and listen for a voice coil that is no longer round and/ or no longer intact ( voice coil wires have come loose).Most woofers have a obvious dust cap over the voice coil it's self - this will be at the exact center of the woofer - DO NOT TOUCH THE VOICE COIL CAP-COVER.Use both hands - spread your fingers evenly onto the woofers cone area a 1/2 inch or so outside the dust cap area and GENTLY press down - you want to get the cone to move as much as possible straight back - if you only press on one side of the cone it will probably scape - this doesn't mean anything- then release the pressure and let it spring forward - it should move forward freely and you should hear nothing. You do not need to push the voice coil to the bottom of the V/C cut in the magnet - if you can move it a little bit - you should be able to tell if it's moving freely and if there is no scraping or rubbing sound from the Voice Coil cap area.If it scrapes,catches momentarily or you hear a sorta whispy higher frequency brush sound when you do this - the voice coil is damaged.If it moves freely with no sound - at least the Voice coil is probably not damaged ( this doesn't always hold true - some prosound speakers have really wide gaps and the V/C can burn out and not scrape - not common on consumer stuff).Anyone who services speakers learns how to do this probably within their first week on the job - while not definitive - it does allow you to separate the obviously damaged from the maybe's - always useful in a service job.This will work work for something like 99% of Hi-Fi woofers ( pulp and plastic/poly cones) - a very few designs use Styrofoam like cones materials - very easy to try this and stick your fingers right thru the cone . If you're not sure - don't try this.
Be careful - but this might be of some help in analyzing your problem.

I've performed the above and I clearly have scraping on 3 of the 4 woofers. A slight tap on the 3 scraping woofers clearly creates a bad sound that I hear terribly when these are playing. Looks like I know what needs to be done. Now to find someone. Thanks all for your input.