4310 midrange problem

[Strat O'Saurus]

I have a pair of later 4310 monitors, the midrange of one is not working. I've removed and resistance-tested both midrange speakers. The DC resistance in both are identical, which leads me to believe the problem is in one of the crossover networks. The midrange drivers are 2105s.

DC resistance of the x-over was tested by use of the midrange speaker leads. One speaker x-over reads ~4 ohms, the other reads 34 megohms, and that value increases slowly, as if one of the capacitors in the network is charging.

My question is simple. How does one remove the x-over network from a 4310 cabinet? If there are any suggestions, I would appreciate ANY input.

Thanks,
Strat O'Saurus :confused:

[Robh3606]

Hello

For starters take out the woofer and find the location of the network. If it is like a 4311 there should be a box where the speaker leads go with a harness to the pot's. I think 4 screws on the back of the speaker around the terminal cut out. If I remember right the screws for the pots were under the foil. With any luck you won't have to remove the foil label.

Those woofers can be hard to get out so be careful. They can stick real well to the baffle.

Take a look at the M12 Expander Kit installation in the L88 Owners Manual should help



Good Luck!

Rob :)

[Strat O'Saurus]

Hello

For starters take out the woofer and find the location of the network. If it is like a 4311 there should be a box where the speaker leads go with a harness to the pot's. I think 4 screws on the back of the speaker around the terminal cut out. If I remember right the screws for the pots were under the foil. With any luck you won't have to remove the foil label.

Those woofers can be hard to get out so be careful. They can stick real well to the baffle.

Take a look at the M12 Expander Kit installation in the L88 Owners Manual should help



Good Luck!

Rob :)

Thanks for the quick response.

I have the 4310 monitors. There are two controls on a narrow panel at the bottom of each cabinet. I have removed the midrange driver from each cabinet for DC resistance test. The interior of the cabinet is stuffed with what appears to be yellow fiberglass insulation. While not adverse to doing so, I would prefer to leave the insulation as is.

I believe that I'll have to remove the foilcal panel and the two knobs for access to the x-over. I suppose my question is how to remove the foilcal dress plate without destroying it.

Strat

[Robh3606]

Thanks for the quick response.

I have the 4310 monitors. There are two controls on a narrow panel at the bottom of each cabinet. I have removed the midrange driver from each cabinet for DC resistance test. The interior of the cabinet is stuffed with what appears to be yellow fiberglass insulation. While not adverse to doing so, I would prefer to leave the insulation as is.

I believe that I'll have to remove the foilcal panel and the two knobs for access to the x-over. I suppose my question is how to remove the foilcal dress plate without destroying it.

Strat

How do you plan on getting the crossover out without removing the woofer?? The mid is in a sealed sub-enclosure. The whole enclosure is not stuffed. Did you look at what I posted?? L88P L100 4310 and 4311 are almost the same speaker. To remove the foil label heat with a hair dryer and gently peel off.

Rob

[Odd]

https://www.audioheritage.org/vbulletin/showthread.php?37054-restoration-project-on-JBL-4310


https://www.audioheritage.org/vbulletin/attachment.php?attachmentid=65671&d=1433664507

[Don C]

It is actually possible for the mid-range to be bad even though the continuity through the coil is good. In your particular driver, it's the most common failure that I've seen. The glue that fastens the voice coil to the former fails due to heat. Then the voice coil and its former and the cone no longer move together. So it's worth taking the time to substitute a known good mid-range to be sure.