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How long can a speaker last?

Other than rotting foam surrounds, watch for:

- Deteriorated glue joints in the drivers, but also the cabinets. Glues can harden and crack over the years. Can often be repaired.
- Dried out cone/dome damping. Some cones are coated and this can crack and peel. Soft dome tweeter 'gunk' can dry out.
- Dried/evaporated ferro fluid in tweeters.
- Sagging cones. Gently depress the bass/mid cones and feel for any rubbing. Can sometimes be eliminated by turning the driver.
- Off spec electrolytic caps, though that's rarer than you might think.
- Check behind any interior foam lining for cabinet wall damping pads and make sure they are still sticky and attached to the cabinet. They can fall off and just sit there doing nothing.

Most of these can be fixed by a specialist repairer, and some DIY.
 
Just to add my 2c. I've got a pair of Mission 752 Freedoms that are 15 years old and look, feel (and hopefully still sound) as good as new.

I've also just recently bought a pair of 754's which would be about the same age and had no qualms about them being that old and buying them second or third hand. Condition was lovely and the sound was great so happy days :)
 
SimonB said:
What are the signs to look for with dried ferro fluid in the tweeters?


Simon
Click to expand...

Unduly strong top end, though ideally you need measure the HF response and compare to a known reference. The fluid performs two functions - cooling of the voice coil and mechanical damping. If the latter is missing the response generally develops a peak in output.
 
Rob,
Thanks for that. I rather expected the opposite. Less output as more energy went to heat..

Simon
 
SimonB said:
Rob,
Thanks for that. I rather expected the opposite. Less output as more energy went to heat..

Simon
Click to expand...

Possibly at very high SPLs, but at low-normal levels the lack of damping pushes the output up and there is less damping of peaks.

Some manufacturers make identical tweeters with and without the fluid.
You usually find that the undamped versions are 1-2dB more sensitive and less even.
 
Depending on the type used some interior acoustic damping materials can degrade after time. More prone in ported speakers as they allow house dust mites to get in to the speaker.
 
Robert said:
Possibly at very high SPLs, but at low-normal levels the lack of damping pushes the output up and there is less damping of peaks.

Some manufacturers make identical tweeters with and without the fluid.
You usually find that the undamped versions are 1-2dB more sensitive and less even.
Click to expand...

I measured my dried out metal domes and found the following:
Up-tilted response with a strong HF resonance and no LF output.
Very high distortion levels
Coil movement very limited (completely locked in places)

Removing the fluid residue restored coil free travel, flattened the response and drastically reduced distortion.

I have suspicions that some speaker "burn in" is (temporary) loosening up tweeters that are in the early stages of sticking by redistributing the remaining fluid. The measured effects are not subtle
 
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