Radio Shack's LX-5 speakers had a bit of popularity at one time, as they featured unusual dipole tweeters made by Linaeum, known for making higher quality speakers. However, the LX-5 had mixed reviews. It was not a high-end speaker by any means. Through the years, some people intended to find out if there was a way to improve the speaker, to bring it closer to the quality level that is deserving of such a unique tweeter.
Some simply tried replacing the woofer. One weakness of the speaker is that the enclosure is fairly small, perhaps too small for the included woofer to operate as well as possible. Others suggested various modifications to the crossover. Yet others worked on modifying the enclosure, which has thin metal walls.
I decided that the parts seemed to be pretty good (particularly the crossover parts), and modifying the crossover seemed like the best place to make modifications, if the changes could be kept minor.
One suggested modification was to add a capacitor to make the woofer's crossover into a 2nd order crossover (having a steeper cutoff). I tried this with one speaker, and it didn't seem much of an improvement.
The modification I preferred was the Murphy mod (the "scaled-down version"), and only for the woofer. http://murphyblaster.com/content.php?f=rslx.html The instructions are for a slightly different model than mine, so the values for the tweeter crossover are different. Only modifying the woofer's crossover risks having problems with the phase, but wanting to keep the change simple, I gave it a try. I may go back and mod the tweeter portion for completeness.
The speakers gained a lot of midrange clarity; some might think it's too much midrange. I think this mod was able to roll off the woofer's frequencies more abruptly, allowing the tweeter to be heard, at the expense of allowing more midrange. Bass is dampened a bit but that may be due more to the polyfill than the circuit change. I'm not sure why this circuit sounds better to me than the simpler 2nd order crossover mod. Perhaps this circuit has a lower cut-off point? I wouldn't have thought so. At any rate, going with a steeper roll-off should make a difference, from what I've read, to get the woofer out of the range in which the tweeter should be playing, particularly since it peaks at some of the higher frequencies.
Another complaint about these speakers is that the bass is a bit boomy. Part of the problem may be that the enclosure is just too small for the woofer. A bit of polyfill will dampen it a bit (just don't add too much) and perhaps give the speaker the illusion of a bit more room. I started to experiment with changing the port, but there's just not enough room to do much with it. While the boomy mid-bass is reduced, you do lose low bass. If you could pair these speakers with a sub, it would fill in the low bass and not be an issue.
After these subtle changes (polyfill and woofer crossover mod), I'm much happier with the speakers. They seem "smoother" and, for now, have eased my desire to run out and get better bookshelf speakers. Ideally, I should modify the tweeter portion of the crossover to match.
LX-5 Crossover with the modification just to the woofer portion.
As these speakers age, it seems to be a known problem that the soft foam surrounds on the woofer deteriorate. Mine were going, so before they went, I proactively ordered a set of replacement speakers, rather than attempt to re-foam the old ones. The stock speakers just have too many problems to try to save them, and you can get decent, superior replacements for $20-50.
AudioKarma has an old thread with instructions on how to open the face of the LX-5.
I decided to go with the HiVi L5-8R as replacements. They seem to be a bit peaky in the upper-midrange, but the are more clear-sounding overall, and in particular, detailed in the bass. The tweeters still sound a bit recessed, but at least the replacements do not overpower them any more than the old speakers.
The crossover probably needs modification, but that is a lower priority.
web.archive.org/web/20070305102054/http://mysite.verizon.net/tammie_eric/audio/lx5mod/lx5.txt -- Another LX-5 crossover mod
Do not attempt this project unless you are familiar with working with audio circuits. This is not a how-to guide, just information on what options are available.