OK. I did the test. First I installed two Seas CA12 4.5" midbass-midrange speakers in extremely rigid double walled cabinets that I had built to help develop a midrange design for the as-yet unfinished HT4. I measured each (they were almost identical), and lugged them into my listening room to see if I could hear any difference between the two unmodified speakers. I have a comparison preamp machine with a remote control that allows instantaneous, volume compensated (though that wasn't necessary in this test) comparisons between up to 4 speakers. The two Seas units sounded the same to me, and not as good as the HT3 sitting next to them. But pretty darn good for raw drivers running full range. I then removed one of the Seas and wrapped mortite tightly around as much of the basket as I could without interferring with the spider or cone surround (that wasn't easy, and I can't swear that I succeeded 100%). I then listened to the same music slections as before (mostly a variety of stuff on the Iowa DIY2007 test disc and some Tchaikovsky at full cry). This was not a blind test. I obviously knew which was which. I didn't expect to hear anything, because the Seas frame is quite rigid to start with, and it's small. But there was an obvious difference this time around. It wasn't really that subtle, and I'll keep this experiment set up in case anyone else in the area wants to hear it. The modified unit had more presence. In comparison, the unmodified Seas sounded somewhat hollow. Maybe that was due to some kind of basket resonance. I'm not sure everyone would say the modified Seas sounded better, although I think it did. But there was a distinct difference, and there wasn't before. I thought it was probably just a change in frequency response due to some ill-placed mortite, so I measured that unit again in the same position as before. Really no difference, except at the very top, and in a direction that wouldn't explain the character or magnitude of the difference I heard, and was probably due to a slight difference in the mic position. Am I 100% sure the effect was due to mortite damping vibrations rather than just restricting cone movement? No--and I would have to repeat the experiment with a larger driver that was easier to work with. But I'm pretty sure. Unfortunately, I can't write to Jim telling him to wrap clay around all of the baskets, because it could very well come loose in the field or during shipping, and that would be a disaster. So I'm not sure this can be implemented as a post-mod. But it's certainly worth exploring (after I expermiment some more, which won't be anytime reall soon due to other demands.) If someone will remind me how to post images here, I would be happy to show you the relevant plots. Thanks for the suggestion, Frank.
