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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
rilbr
97 posts
 
Be careful with the material of the cabinet and size of screw. In general, oil strengthens wood and paper material, water swells and weakens wood and paper. Use a wood or mineral oil rather than automotive types which have solvents and detergents.

Brass inserts are the best way to go, but require time and skill. This is why only a few speaker manufacturers use metal inserts in the cabinet.

If torquing, use a high quality torque screwdriver. Avoid a torque wrench. Otherwise just go by feel.
swampwalker's avatar
swampwalker
5,138 posts
 
Otherwise just go by feel.
And remember that the tightness scale is as follows:
A little loose
Snug
Tight
Very Tight
Totally Loose!!
strat1117's avatar
strat1117
38 posts
 
Thought I’d resurrect this worthwhile old thread. I have found this to be true on virtually every speaker I have owned. I disagree about doing it every two weeks as someone mentioned above, but once every 2 years is about right. I also don’t agree that it is strictly or even primarily about the expansion/contraction of mdf - over 40 years in the hobby and I have found that tweeters rarely get loose, and I have found that woofers get loose even on Wilson speakers which are made from materials designed not to expand or contract. It’s about the movement of the woofers, and it cannot be avoided. Be gentle and be VERY careful of the powerful magnets which can rip the tool from your hands. I would NOT recommend Loktite or any other foreign substance or modification (such as bolts instead of screws) unless you are confident that you can reverse it without consequence. Such modifications WILL alter the sound of your speakers in unpredictable ways, while merely snugging up the drivers every couple of years should be considered ordinary maintenance that will keep your speakers sounding like new.

Enjoy!!
jafant
18,932 posts
 
This is a pretty good thread.  Happy Listening!
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