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JBL Speaker Repairs

Note: Many JBL models exhibit "reverse" or negative polarity - that is, when a positive voltage is applied to the red input terminal, the cone or diaphragm moves inwards, towards the magnet structure, not outward, as is the industry standard. There is a factory document that details this and lists the polarity of all JBL models.

JBL loudspeaker products can be divided into two distinct, but of course blurred, categories: PA products and consumer products. The distinction is blurred not just by people who use PA speakers for enjoyment of music at home, but products that were designed and built for studio use that were also offered in consumer versions.

Professional and Public Address

I see a steady stream of PA drivers from local bands and venues. These are high power, high efficiency units that are often run at full tilt for hours on end. Sometimes this is just a bit too much, and they get rotated through my shop so they can go back to work.

Here are a pair of 2241H 18" and M115-8A 15" (I think) drivers in for repairs - the first photo shows just how far gone they were!

JBL 18 and 15 PA repair - damage

The exposed magnetic gap is taped off while the old cone edge and spider are scraped clean.

JBL 18 and 15 PA repair - cleaned

The new spider and voice coil are carefully shimmed, centered, aligned for height with the magnetic gap, and glued in place.

JBL 18 and 15 PA repair - voice coil install

The new cones are carefully glued in place while the voice coils are still shimmed.

JBL 18 and 15 PA repair - cone install

The leads have been dressed to new tinsel, new dustcaps attached, the cloth surrounds treated with a flexible sealing compound, and the front trim gasket is in place. Tested and ready for action!

JBL 18 and 15 PA repair - finished

Consumer and High Fidelity

This is a pair of 12" woofers (part number 2214H) from JBL L100T speakers I refoamed:

The surround wasn't the only foam rotted away on these - the vents in the magnet structures were covered with disks of porous foam (to keep foreign material out) which had also fallen apart. I scraped them off and replaced them with circle of grill cloth and the screen I use to protect my tweeter dome:

Here is a pair of James B. Lansing "Minuet" speakers I repaired. Unlike polyether foam surrounds, which slowly soften, degrade, and fall apart, the "Lans-a-loy" surrounds used in this speaker get so stiff with age that they no longer allow the cones to move.

This is a full-range design, with one active and one passive driver.

Here they are as delivered by the customer.

JBL Minuet repair - before work

The grills are removed and the problem diagnosed (inflexible surrounds).

JBL Minuet repair - grills off

Here is a gratuitous rear view of these vintage parts.

JBL Minuet repair - rear view of parts

The surrounds were so hardened they came off in one piece.

JBL Minuet repair - surrounds removed

Here is a woofer with the dust cap removed, the voice coil properly shimmed, and a new surround glued on.

JBL Minuet repair - shimmed and new foam

The new dust caps did not come with new closed cell damping foam, so I saved the two pieces to reinstall.

JBL Minuet repair - new dust cap, old damping foam

While I had them apart, we had decided I would replace the old spring terminals with my binding posts and 1/4" MDF board. The old input boards were saved for posterity.

JBL Minuet repair - old terminals

Here is the board and new wires installed from the inside.

JBL Minuet repair - new board inside

And this shows the new binding posts from the rear.

JBL Minuet repair - new terminals

And, finally, reassembled, tested, and ready to go home.

JBL Minuet repair - fnished

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