What is the factor that makes tweeter's level unequal between left and right ?

presscot

Member
2010-07-27 12:24 pm
I have a pair of the old school ADS 320i speakers. It hasn't been used for many years. I now bring it back in use again and found one of the tweeters has no sound. So I inspected it and saw the tweeter's dome, a fabric dome, was attaching to the grill. I removed the grill to correct it but as the grill was pulled upward, the dome+voice coil came out with the grill. :eek: Although the dome + voice coil separated from the magnet, but the copper wires that connect the voice coil to terminals are still remaining. So I recognize that the glue on the surrounding was defunct and the fabric dome also deteriorated so that it became gummy and finally attaching to the grill. After that, I use the needle to press the dome out of the grill. When it came out the whole dome I glued the surrounding and installed it back to the magnet. Sit back with a glass of wine and listen to them. There's a good news that this ADS can sing again! But the bad news is the repaired tweeter was sound gradual to the other side.

What is the factor that makes tweeter's level unequal between left and right ? What needs to be fixed ?

PS. There's one thing suspected. Once the dome+voice coil were standing out of magnet, I saw the voice coil was wet, something like fluid soaked on it with brown color - a rust like :xeye:. But I suspect this was the ferrofluid, could it be ? If so, Could it be the cause of the tweeter unequal loud ? i.e. the fluid dried. Will I have to fill it ?
 
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eriksquires

Member
2013-05-10 4:11 pm
That's a very disturbing set of events. It's like you described your speaker being dismembered in a horror movie, with ferrofluid for blood.

If you added any mass at all, or fail to replace the coil in exactly the right position this would all be causes for this issue.

Best,

Erik
 
I suppose you have not replaced the voice coil in the right position, try to move laterally (carefully !) in every direction until you get a louder sound... If you have an audio generator, 1 to 2 kHz (try !) sinus can be very helpful. Beware of any excess of power. Audaces fortuna juvat !

Pierre.
 
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TMM

Member
2007-09-01 8:37 am
Australia
If some ferrofluid was removed in the process, it is very likely that the voicecoil is no longer centered in the voicecoil gap and is now rubbing. This will increase distortion and lower the sensitivity/level.

It's also not unusual for a tweeter to have a very small xmax - that is the region of concentrated magnetic field in which the voicecoil experiences linear and maximum force. <0.1mm xmax isn't uncommon. So if the voicecoil is now sitting 0.1mm further into the gap or 0.1mm further out, it will perform differently.