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[Jeff Hague]

I have a pair of McCauley B1860 18" drivers lying around that havent been used for quite a while. They were loaded in a set of homemade cabinets and were supposed to be used in place of double 18 cabinets for smaller stuff but, if the band was fairly loud, I would get a real nasty "pop" out of them every now and then - sounded like the coil was jumping the gap. I assumed that the cabinets were not designed properly. Anyway, they got shelved for several years and I pulled them out about a year ago to try to figure out what to do with them. I found that one of them had about a 2" section where the cone had become separated from the surround and I suspect that is the "pop" that I remember hearing. Anyway, I posted here for advice on how to fix it (since baskets are no longer available) and last night I finally got around to doing it. Whilst fixing it I noticed that the spider looks a bit deformed - its not really flat - and I also noticed that there is a big difference between the 2 drivers. The 1 that needed the repair is nowhere near as stiff as the other driver when pushing against the cone and the cone sits higher as well - the 2nd roll of the suspension sits out past the rim whereas on the 1 that didnt need to be fixed, the 2nd roll of the suspension does not sit out past the rim... Both drivers do work when popped with a battery and they both feel good - no rubbing or scraping of the coil.
Is it possible for a spider to be damaged but still hold the coil in the gap?

[Art Welter]

Jeff,

Spider damage should be visible, though age deformation can be subtle.

The “pop” noise you mention could have been the voice coil former hitting the back plate, although that sounds more like “clack” to me than “pop”.

Cones separating from the surround usually “flap” rather than “pop”.

Both the surround suspension and the spider should be parallel to the front frame.

It is possible the cone that needed repair may have been reconed with improper alignment or parts or both. The difference in suspension stiffness  makes me suspect the parts are different. A looser suspension would allow the speaker to “bottom out” easier.

Careful inspection would probably reveal if the parts were different.

It is possible that the cone has simply drifted over time, which way was it sitting while stored?

Were both cones stored in the same direction?

Any sign of water damage?

Art Welter

[Jeff Hague]

It may have been a clack, a flap or a pop - but it definately was not musical. Once I noticed the separation, I envisioned the cone traveling farther than the suspension on the way out and the sound was when the 2 met again on the return trip... It actually did it very quietly whn popping with a battery too.
They werent reconed - we bought them new from McCauley (probably 10 years ago - its been a while) and they are field replacable baskets anyway - pull the entire basket off of the magnet and bolt a new one on. To my knowledge, that was never done but they were in the care of my brother for many years so its always possible. The cones, spiders, baskets, suspensions, et al do look like the same parts.
They were "stored" in their cabinets upright so drifting is definately a possibility. Most of the time they were in a barn so free from outright water damage but exposed to humidity and temperature changes.
I do know that the paint on the rim near where the separation occured is in bad shape - almost like corrosion - and I believe that was the part that was toward the bottom of the cabinet. I suspect a drink was launched at the cabinet at some point...
Ill try to post some pics tonight.