Speaker Mods?

Modifying speakers is really iffy. You really might want to think about just buying new speakers, especially since no one will ever buy modified speakers. Totem makes bookshelf and small floorstanding speakers with a lot of bass, and those can be found rather inexpensively used here on Audiogon.

Would tend to agree with Milo. Leave the drivers alone. Look inside the cabinet for opportunities to upgrade. If electrolytics are used, replace with polypropylenes of equal value, improve wire internally and stuff corners with cord weather stripping to reduce cabinet resonance. Total cost should be no more than $50 and if you still don't like the speakers sell them.

Yo Alfred,
While I am not fond of aluminum dome tweeters, their sound can be improved on by several methods. Before you go buying new drivers, you might try upgrading your crossover capacitors. By replacing the caps with high quality MIT, Zen, Harmony, or Solen caps, the treble balanace will not be changed, but the sound will be smoother. Another trick it to bypass the existing caps with .01mfd ultra high quality caps. Simply solder them in parallel with the existing caps. For more info goto http://www.northcreekmusic.com/Bypassing.html. The best place to obtain these capacitors is Madisound, Michael Pearcy, North Creek Music Systems, Zalytron, and Welborne Labs.
My experience is that most of the time the speaker is not the culprit when someone complains of harsh treble. Your room might be the real problem. Room treatments might be all you need. A combination of absorbing and diffusion materials placed in the right locations can work wonders for those high frequencies. Take a look at this website: http://www.audiophilia.com/hardware/echo.htm for info on Echo Busters.
Hope this helps.
Best Regards,

Alfred,
One thing that hasn't been mentioned is that nobody will want to buy your modified speakers in the future. Selecting drivers/crossovers is a very interactive process, and is tricky to maximize without a lot of experimentation & knowledge. If you decide to modify them you'll have even more money wrapped up in them while the resale is simultaneously dropping through the floor. A potential buyer is likely to view the whole process as a huge red flag. If you change them you better want to keep them. It's probably not the best investment.

I suggest you sell them and combine your resale proceeds with whatever you would have spent on upgrades to finance the new purchase. I'd suggest a used or kit pair. There are many great kits from the sources listed previously. I've owned Madisound MDY-4's (they won't have the bottom end you're looking for), but they offer several other great options (I was always partial to the Dynaudio kits). I went with North Creek Music Systems (Scanspeak drivers and NCMS crossovers are amongst the best of the best) for my current setup. You owe it to yourself to check out the kit option. The other best bang for buck is to pick up a pair of whatever you've heard and liked used. A suggestion for small speakers with suprisingly good sounding LF (so long as you don't play them too loud) and great midrange/HF is the Totem Model 1's.

Best of luck.

I bought tweeter replacements from Madisound and had no problem... these were exact replacement tweeters. Changing tweeters to another model is NOT recommened.. will really screw alot of things up I'm told.