L-150 best refoam, shim or not ?

[Dave Cawley]

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I bought a new pair of L150's in 1980 and later sold them to some friends. Now they are back here where they belong ! But all four bass units have lost their foam.

Which is the best kit, I have seen some with shims, others without. Cost is no object.

Are there any driver/crossover upgrades ?

Thanks

Dave

[Odd]

Resurround Step-by-step (http://www.audioheritage.org/vbulletin/showthread.php?469-Resurround-Step-by-step)In the link above you also get recommendation about the possibly best kit.

[Dave Cawley]

Yes, I had read that, but the supplier doesn't seem to do the ABR and the thread doesn't actually answer any of my questions.

Thanks

Dave

[grumpy]

Both shim and LF tone methods work. I'd be more inclined to use the tone method if the sole issue was deteriorating foam (less intrusive and sufficient). A full-on recone definitely requires a physical centering device.

L150A would be one upgrade, but I don't think the 044 physically fits the 033 hole without a lot of work.

could do a partial network update and bypass (small value in parallel) the existing capacitors ala the 150A network. I don't recall if they used Mylar or polystyrene...

I'd be surprised if the passive radiator surrounds were different than the 128H (iirc, several cone diameters were used, so your source should be asking you to measure the diameter).

[Chris Brown]

Which is the best kit, I have seen some with shims, others without. Cost is no object.

Both methods have their pros and cons. Using shims is the older / more traditional method. The benefit of this method is that you will be able to know, with 100% certainty, that the voice coil is perfectly aligned. That is what the shims are for. The downside is that it requires you to remove the dust cap first. That can be difficult, and it's almost impossible to get the glue to look as good as it did previously when you re-attach the dust cap. The other method involves using a 30Hz test tone during parts of the refoaming process to self-center the voice coil within the gap. This method is a bit less precise but is what most people use these days, and results are almost always more than adequate. The benefits are that it involves less work, particularly not having to remove the dust cap, which means the factory glue job can go undisturbed.

I'm not sure if this counts as an "upgrade" but one easy thing you can try is adjusting the mass rings (http://gotnorice.com/PR300weights.jpg) on the passive radiators. This would have the same effect as lengthening or shortening the port on a ported system, but thankfully adding or removing mass rings is much less permanent, making it easy to adjust to your taste.

[Dave Cawley]

Thanks for the help and encouragement. I have ordered the refoam kits.

I am amazed at the internal wiring and the input terminals on the back. JBL recommend 300W for transients, however the wires are so very thin. I'm going to replace them and solder directly to the crossover, speaker units and to the new replacement terminals.

Thanks

Dave

[Dave Cawley]

All sorted, re-foamed and rewired including all push on connectors now soldered. 3V RMS at 22Hz but I think not essential though. Works great !

Regards

Dave