Hi Kasra: This is the CHEAPEST way I know of. But it is not the best way, and there may be some strong comments in response to what I am going to say. The following solution is cheap and nasty, but it WORKS well enough to give a significant improvement to old X-over boards with drying out aluminum electrolytic caps. And, ANY local electronics supply source will have the parts you need for a very low cost.
I don't know what is in the Advents, but I am assuming that they are bipolar electrolytics ... uhm ... 8uf — 10uF — 22uF — 47uF ? ... I dunno. Ideally you would replace them with good film caps, and there are lots of choices. Often there is a problem getting their large physical size to fit where they are needed, but it is virtually a universal opinion that film caps of some kind are better than aluminum electrolytics. Some people select paper and oil. Well, that's great, except if you are not in the money, or in your case balking over the supply issue. This alternative solution does not require you to order parts on the net.
Get to your local parts store and buy some bipolar electros of the same values as the originals, and that are no less than the original voltage rating. Also buy some Mylar or metal film caps between 1uF and 4 uF — again no less than the voltage marked on the old caps. You will need as many of these as there are electros.
The electrolytics you find will most likely be radial types, and their physical size will be MUCH smaller than the bipolars specifically designed for X-over circuits. It is pretty likely that they will be rated at 50 volts or so. If your parts shop carries proper X-over caps, by all means buy them. They will cost a bit more, but they are applicatiion suited by design. The glich may be that most local shops that I am familiar with don't have such an animal.
Hot glue, strap, or otherwise fix these whatever bipolar electros to your X-over board as close to the appropriate pads as you can. Proper X-over caps will be a cinch, but modern examples could still be smaller than the originals. Lead orientation is a non-issue with BP caps. You may need to solder a tad more copper onto the leads to feed the pads — not ideal either, but then ....
Next, you use the film caps to by-pass the electros. Even in these values their size is likely to be large relative to the electros, so be sure to fix them onto the board as opposed to just hanging them on the body of the electros. If you have not by-passed caps before, just solder the leads of the film cap to opposite leads on the electro. Use a heat-sink clip or haemostats next to the cap bodies to soak up heat on the leads when you do this.
This solution will no doubt horrify the purists, but IT WORKS. If you have tired/drying out caps that you can't afford to replace and upgrade in the best manner, you will still hear a VERY significant difference. For one thing, these new bipolar caps will more than likely be pretty good in themselves compared to the 40 year old do-dahs that are in there now. And the bypass caps will help a lot too. You will be told by some people to use much smaller values for the bypass, but I followed some other advice, and I liked what I heard a lot.
There could be a drawback to keep in mind: these smaller electros may not dissipate heat fast enough. They may dry out faster than the normal application would call for. I say MAY, because YMMV. But, in any case, you can be enjoying tunes for some time while you take your time collecting parts for the most masterfull X-over rebuild that you may want to accomplish some time in the future. Besides, it can be a treat to hear an improved sound that costs only a few bucks.
Here are some pics of a cheap-and-nasty I did on a pair of Sansui SP-G88 3-ways. My pencil said that if I were to do the job in the best and most polite way, it was going to cost me more money than I had. And I decided that if I couldn't have the whole monty, then I would have the cheapest solution. So I made do with common parts from the local industrial supply house. Big improvement ... and it cost very little. I remounted part of the network on a plywood board. The next time I get to Tokyo, I will buy some better (larger) BP/NP electros, or go the whole hog on some big film caps.
The blue, boxy thingy-puffer is a Mylar bypass cap. For extra copper I used "magnet wire" and single 24 guage strands of CAT-5 LAN wire. The big resistor is an original part that I mounted on a pair of ceramic insulated standoffs I had in my parts bins. I used hot glue to stick stuff on the ply, and tied I the circuit together on a phenolic mounted strip. The board was suspended on the speaker body by copper that I cut, bent driilled and screwed. Any moron can do it, and it is likey that you can do a better piece of work than I. The point is, just go and do it with what is at hand. The last pic shows the comparitive size of the old electros.
One thing about doing things in steps like this is that you learn something about what is going on in your component. On a newer set of speakers I merely by-passed a 47uF BP electro on the woofer and — WOW — what a difference! I used a non-exotic 4uF film cap.
Cheers and good luck. And BTW, any searches will dredge up TONS of stuff about speaker recapping both here and over at Audio Asylum.
