73 Fender Twin w JBL's Blown speaker?

[ctcpete]

Hi Guys,

I blackfaced and refurbed my 73 Twin with the great assistance I found here about a year ago. It went well, I even had a pro amp tech check it over and he said it looked good..thanks again.

I'm having a problem with a buzz occurring on bass notes starting at medium volume I'm suspecting a speaker, they are original orange frame JBL D120Fs, never re coned. Can I disconnect one speaker at a time to troubleshoot them? I have no other speakers around that I would want to try at this output wattage.

Thanks very much in advance.

Pete

[JoeM]

You'll have a mismatch in impedance, but that wont be a problem for testing the speakers. Does it sound like it's coming from a particular speaker, or is it a cabinet buzz? I'd first be sure the speaker mounting nuts are tight, chassis mount straps,etc.

[Gibsonman63]

It is not enough of a mismatch to hurt anything and a good way to isolate the problem. Make sure the nuts holding them in are tight. Drop in recone kits are about $80 if you decide to tackle it yourself.

[Jazz P Bass]

Peek in at the spider (the round ribbed thingy where the voice coil attaches to the cone) & see if the glue did not lift.

[ctcpete]

It is not enough of a mismatch to hurt anything and a good way to isolate the problem. Make sure the nuts holding them in are tight. Drop in recone kits are about $80 if you decide to tackle it yourself.

How difficult are the recone kits to do? If I need 2 kits at $80 each I may decide on replacement speakers although I've heard that the old JBL's are valued by some.

Thanks for the info.

[Gibsonman63]

Reconing them is not terribly difficult with the drop in kit, just a little tedious. If you decide to do it, cut around the center cone first, pull the voice coil and then tape off the slot. If you get anything in the slot, it will be hell to get out. The JBLs are a bit pricey, so even if you decide to go with another speaker, they are worth something to someone who really wants one. In a Twin, they are super clean. Good for rockabilly or country twang, not so much for blues and rock to my ears.

If you figure out which speaker is giving you grief, remove it from the amp and press in onthe cone with even pressure (carefully) and see if you can feel where the voice coil rubs the slot. If it is a slight rub, there are some tricks to try before reconing but I have never done it. Just search the forum, I believe it has been covered. Also, mark the spot on the backside with a sharpie where the rub is so you can check it later to make sure that the slot is clean and smooth in that area.

[JoeM]

Where do get a JBL recone kit? Are they JBLs or aftermarket?

[ctcpete]

Where do get a JBL recone kit? Are they JBLs or aftermarket?

These are original orange frame JBL's. I don't think I am up for the recone job but thanks for the advise, I'm afraid I'll botch it. I would like something that breaks up easier then the JBL's anyway, I may replace the speakers (need to do some research for what to get) and keep the JBL's if I sell the amp. I'll have a chance to test it tomorrow with one speaker disconnected at a time.

[Gibsonman63]

The kits were aftermarket. I got them from Reconkits.com. It took quite a bit of googling to find them the first time.

That was a project amp that I picked up. The Twin that I kept has the goldback Jensen speakers. For the stuff I play, they work better and the amp is 30 pounds lighter.

[ctcpete]

How would I remove these speakers anyway? I assume you need front access? Thanks again for all the replies.

[Gibsonman63]

There should be 4 or 8 nuts holding them in that can be removed from the back. Check first to make sure they are tight. The gaskets on the front of the speakers can dry out and the speaker can loosen, which will cause a rattle especially at lower frequencies.

[ctcpete]

I'll do that. I also learned from another site that the grill cloth frame prys right out, it's held on with velcro (didn't think they had it in 73). The fronts look ok,no rips, the glue on the two small wires near the cones look ok. Some of the nuts are slightly loose, will tighten them. Thanks again for the assistance Gibsonman63.

[überfuzz]

Wow. So your going to do major tinkering without even testing the speakers? If I were stranded with no extra speaker I'd go to the nearest rehearsal studio or amp dealer asking please with sugar on tops. (Plug the machine in, your amp with their speakers, your speakers with their amp.) If you hit a band, you'll hear the noise from across the street, in the studio they might charge you a bear or two, if anything. An amp dealer would probably like to see you buying a set of tubes in the near future.

[überfuzz]

Oh, by the way. Velcro came with the aliens in the Roswell crash - 1947.