I haven't seen much about the ALS40 II's around here, so I figured I would share some experiences recapping a pair.
I bought the replacement capacitor kit from Falcon Acoustics, which arrived in a timely fashion but, unfortunately, it was missing two of the necessary 4µF capacitors. I alerted Falcon but have yet to hear back from them.
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For reference, a full recap of two ALS40 II speakers requires twelve (12) capacitors:
4x 60µF
2x 12µF
2x 6µF
4x 4µF
The crossover network inside each speaker is divided into two boards, a large one located behind the upper bass driver (see below) and a smaller one located on the back of the terminal binding posts. Each of the large boards has four capacitors (2x 60µF and 2x 4µF) while the small boards have two (1x 6µF and 1x 12µF).
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Here is the board behind the bass driver:
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This board is attached directly to the white foam, via some sort of brown, crusty glue. The foam peels away from the board relatively easily, especially if you use a plastic putty knife. Since I didn't have enough capacitors to do the entire job right now I didn't peel the boards off completely. Does anybody here have suggestions for an appropriate adhesive to re-attach the boards to the foam? I have some good contact cement and I was thinking of trying that. What do you guys use?
Although I left the big boards alone for now, I did re-cap the small boards and clean the high frequency attenuator switch with contact cleaner. The through holes for the 6 and 12 µF capacitors are marked below.
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The ALCAP replacements are slightly bigger than the original ELCAP's but they fit just fine.
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I am not finished with these speakers, but I already notice a BIG difference in the sound. Before cleaning the switches and replacing the capacitors, both tweeters were essentially dead and the overall sound of the speakers was quite dark. Now the sound is much brighter and the authoritative bass that these speakers can pump out is balanced by a clear top end register.
I finally replaced the rest of the crossover capacitors in one of my IMF ALS40 II's. I often work on one at a time and then compare the two, just to make sure I am not wasting my time with all of this refurbishing. Sometimes I can barely detect a difference, but with the IMF's both rounds of capacitor replacement made a significant difference in the high and midrange sound, in fact more than I expected.
For those who might be tempted to try it themselves, here is a simple, step-by-step guide:
1. You will need: replacement capacitors (natch), phillips screwdriver, plastic putty knife, rubbing alcohol and Q-tips, contact cement (I used Weldwood by DAP), needle-nosed pliers, and soldering gear (iron, solder-sucker, solder, and a good solder flux).
2. If you order the replacement capacitors as a kit from Falcon Acoustics, be sure to tell them how many capacitors your speakers actually have. IMF made different models of the ALS 40 II (some for export, etc.) and the crossovers do not all have the same number of components.
3. The large crossover (which has either 3 or 4 capacitors) sits behind the upper low frequency driver. This driver is not centered and the easiest way to remove it and get it out of the way is to turn the speaker on its side, so that the driver is farther from the floor. This sounds counter-intuitive, but the way the wires run, this position gives the most play and allows the driver to reach the ground without cutting the wires.
One of the best decisions IMF made in building these speakers was to use bolts and threaded inserts to hold the drivers, rather than just driving wood screws into the MDF. The driver might need to be coaxed loose and it will probably take a few small chunks of MDF with it (see second photo below).
4. The crossover board is glued to the acoustic foam inside the speaker so you will have to pry it off. I used a combination of a plastic putty knife and my fingers to minimize damage to the foam. Some of the foam will inevitably come along with the board.
5. Use the rubbing alcohol and Q-tips to remove the foam and glue residue from the solder joints that connect the capacitors to the traces. You don't need to remove all the crud, just the crud on the contacts that you need to de-solder.
6. Desolder the contacts (I prefer a spring-loaded solder sucker) and use the needle-nosed pliers to pull the old capacitors. Be careful not to pull any of the traces loose. If you do, use super-glue to re-attach them to the board.
7. Thread the new capacitor leads through the holes and double check the values. Pull the leads tight with the needle-nosed pliers and then solder them in place. Use flux to get a good, hot joint. Note that the Alcan capacitors from Falcon Acoustics are larger than the original Elcans, so they might protrude over the edge of the board or rest against the adjacent inductors. I use hot glue to stabilize them.
8. Apply contact cement to the bottom of the board and to the foam. The foam soaks it up a bit so you will have to apply more to the foam than the board. I shifted the position of the board slightly compared to its original position so that I was not applying all the cement over the old, dried up glue. Depending on the contact cement, wait a few minutes for it to dry and then apply the board to the foam. The bonding is more or less instant, but I held it on for a minute or so, just to make sure.
9. Replace the driver and screw it in tight (this is where the bolts and inserts make a huge difference). Be sure to inspect the gasket to make sure that it is in good shape and will make a nice seal.
And then: voila!