Amazing "tightening" of bass on cone speakers


I own a pair of old Mission 773 speakers. My impression has been that these still sound "okay" but have seen better days. Today I was reading the owner's manual to check the stated specs. In the maintenance section, Mission suggested that the screws holding the bass drivers to the cabinets should periodically be tightened(they also warned never to touch the screws for the tweeter). I said to myself "What the heck" and grabbed an Allen wrench. To my surprise, all the screws seemed tight but were able to be tightened another turn or so without undue pressure.
I was surprised by the difference in the sound. Not only was the bass much better defined and could go much deeper without distortion, the total sound was transformed, leaving far more interesting timbres to be heard and even the imaging was sharpened.
Having been into audio since forever, this really shouldn't have surprised me. It makes sense that slightly loosened bass drivers would create bad sound. And over many years of constantly vibrating, some loosening could easily happen. However, checking this out had never even occurred to me and I'm wondering how many others have tried this "cure" and (other than over tightening) if you've experienced a downside?
terrysimmons
Well, a timely thread for me. I built a pair of speakers in January and have been making progress on them since (been out of town and otherwise occupied so not continuous). I've been working to get the bass right and have been struggling. I read your thread and VIOLA...OK still not perfect but more progress fixing the bass in 2 minutes than I've had in 2 months. Of course this wasn't fixing something that worked loose, but fixing my sloppy work.
Thanks Terrysimmons!
Read pages 4 & 5 of this article, for an explanation: ( http://www.stereophile.com/content/pace-rhythm-dynamics-page-5 )
...depends on the manufacturer. Vandersteen says never to tighten the screws, because mastic is applied before the speakers are screwed in. ..so they are glued in at the factory, and futzing with the screws could break the seal.
Thanks Terry,
That is one that I had completely forgot about and it used to be a regular thing 'back in the day'. I just checked mine and all the hex heads needed almost a quarter turn, main driver as well as the mounting for the supertweeter.

Embarrassed, to say the least :-)

All the best,
Nonoise