Radio Shack MINIMUS 7 crossover upgrade

A DIY company offered a upgrade kit many many years ago but basically this is what you can do:

1. Replace the stock gray capacitor with a 4.7 microfarad Solen rated at 250 volts. The old one may be hot-melt-glued to the crossover board so instead of trying to remove it, just snip the leads and solder in the new cap.

2. Remove the fiberglass insulation and affix / dampen the top, bottom and sides with a sticky dampening material (like Dynamat) since the one used is no longer available. Be carefull handling the FG. Reinsert the FG (you may want to replace the FG with some Poly).

3. Dope the woofer. It seems Damar varnish is the "dope" of choice. Damar varnish is not a brand name, but a type of varnish typicaly used by artists who paint with oils. It would be available from a local art supply store. Grumbacher's Damar Vanish (2 1/2 oz. was the smallest bottle I could find at Michael's or other artist supply store). Do not get the type used for airplanes Coat just the woofer with a small brush and be VERY CAREFUL not to get any on the rubber surround. Allow it to dry eight hours and then apply a second coat. Allow second coat to dry 24 hours before playing music. DO NOT ATTEMPT TO TREAT THE TWEETER!

[u]Special Note if you cannot find the Grumbacher Damar Varnish.[/u]
Run a test of a couple of whatever Damar varnishes you can find on 24# or higher copier paper or paper grocery bags cut into 4" square and let dry over night. The successful varnish will dry without warping the paper. Michael's was very accommodating in allowing me to return the ones I didn't use so long as I didn't gum up the containers.

You can google to see if there are other options. Good luck and have fun.

My first reply to your question doesn't seem to have made it past the moderators, perhaps because I gave the user ID of the guy who sells replacement crossover kits for the Minimus 7.

I don't have any connection to him other than having bought three of the kits and been very happy with them. He sells the kits on ebay and if you search for 'minimus 7' you'll find them.

The instructions that come with them are pretty primitive but it's definitely worth the effort to figure it out. Just take your time, stare at the innards of the speaker for a few minutes and you'll do fine.

The only thing that takes a little figuring out is where to mount the new crossover board so that you have enough clearance to put the woofer back in. I used a hot-glue gun to stick it against the side wall of the speaker enclosure.

I recently replaced the crossover in my Minimus 7s. I considered the kit that Sfar refers to (sold on ebay), I also searched Audio Asylum where there's lots of advice. In the end I simply built a 1st order crossover from parts I purchased at Parts Express. I also replaced the sprung wire connectors with good 5 way binding posts. I used acrylic from Home depot for the structural parts (ie to fasten the caps, inductors, and binding posts to). The only challenge was positioning the cap so it wouldn't interfere with the woofer.

This is an easy DIY project, even if you haven't done anything like it previously figuring it out yourself is a good learning experience.

Wow there are quite a lot of audiophile people still using or have knowledge of this Minimus 7 speakers! :)
After reading replies from these knowledgeable agons members and a little from google (not much there unless somebody can point to me the info), can I ask some follow up questions?
1. What is the recommended type of capacitor and value to replace the existing one inside?
2. What are the components to build the low pass filter for the woofer? How do you connect these components together with the woofer? How do you choose between cutoff at 2khz versus 3khz?
3. The fiberglass material should be replaced inside. What are the recommended material and how dense should it be stuffed inside the cabinet?
4. Should the woofer be doped like the suggestion above? Do you paint inside and outside? Would this make the speaker less efficient and perhaps change the lower frequency as the movement of the woofer is lower?
5. How easy is it to remove the metal grills off these speakers?

Thanks for your forthcoming replies on this! :)

The original kits were sold by a long-defunct outfit called Soundaids (separate kits for minimum 7 and the larger Minimus 77) Lngbruno has all the basics right. This is really worth doing -- especially for the 77, which produced an amazing amount of tuneful bass for a speaker this size. Good luck, Dave