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steveokla
03-17-2006, 05:56 AM
I recently picked up a nice K130 for my Vibroverb, but, turns out, the mounting screws in the amp are nearly 1/4 inch too short (the original CTS speaker is a thin, stamped frame, versus the heavy cast frame of the JBL). I certainly don't want to drill any new holes or drive in additional screws as this is a vintage amp. Anyone have any suggestions? Thanks, Steveokla

edgewound
03-17-2006, 07:40 AM
I recently picked up a nice K130 for my Vibroverb, but, turns out, the mounting screws in the amp are nearly 1/4 inch too short (the original CTS speaker is a thin, stamped frame, versus the heavy cast frame of the JBL). I certainly don't want to drill any new holes or drive in additional screws as this is a vintage amp. Anyone have any suggestions? Thanks, Steveokla

Steve,

Make an adaptive mounting ring/plate to attach to the stock baffle screw studs, attach the K130 to the ring.

Hamilton
03-17-2006, 08:54 AM
Is it possible (with the speaker removed) to reach your hand between the baffle board and the grill cloth, then tap the orig screws forward from inside the cab?

edgewound
03-17-2006, 09:22 AM
Is it possible (with the speaker removed) to reach your hand between the baffle board and the grill cloth, then tap the orig screws forward from inside the cab?

That was gonna be my other suggestion. Try to put in longer screws through the original holes

Zilch
03-17-2006, 09:55 AM
There's a way to do this. I saw a kit on eBay about 9 months ago sepecifically for the purpose. Anybody remember how it worked?

Alternatively, I'd be trying to remove and replace the original studs....

Tom Loizeaux
03-17-2006, 10:29 AM
You're going to have a hard time pulling the screws out the front of the baffle. The screws have large flat heads that pull up flush with the front of the baffle and are long enough to give you problems with pulling them out the front due to the tight grille cloth.
You may want to look for T nuts, sized to thread on to the existing Fender baffle-mounted screws, that can push through the holes in the JBL frame and catch the screws. Look for long necked T nuts and preferably the ones with the two flat sides without the bent-over prongs. You could, of course, bend the prongs back on standard ones. The question is if these T nuts will fit in the JBL holes and reach the ends of the screws.
I agree that you should try to avoid "modifying" the amp if possible.

Hope this helps.

Tom

steveokla
03-17-2006, 12:33 PM
Thanks, all. I've spent a good part of the day in hardware stores, then specialy supply places looking for T-nuts and similar hardware, as well as connectors to 'lengthen' the machine screws. Struck out.

Zilch--do you recall if the kit was a JBL product of somd kind?

Edge--could you elaborate a little on the additional ring--what material, etc.?? Thanks agains, Steveokla

Zilch
03-17-2006, 12:54 PM
Zilch--do you recall if the kit was a JBL product of some kind?Not JBL, it was offered by one of the guitar amp restoration/customization type folks.

I kinda recall it was a custom nut with a threaded female shaft, like sex bolts. Go here and put "sex bolts" in the search window:

http://www.mcmaster.com/

Depending upon the stud size, you may have to enlarge the woofer frame holes for the standard ones to fit.

See also "weld nuts," the type like T-nuts without the prongs....

edgewound
03-17-2006, 01:58 PM
Edge--could you elaborate a little on the additional ring--what material, etc.?? Thanks agains, Steveokla

Steve,

Here's a really, really crude sketch to show you my idea. If there's room enough in the Vibrolux enclosure, you could mount the ring to the original studs and secure it with the original nuts countersunk. You would mount new machine screws or studs to the ring exactly like the on the amp baffle board....only you'd place the new studs between the counter sink holes, and only use four studs to mount the K130.

steveokla
03-17-2006, 02:18 PM
Thanks much, Edge!

Hamilton
03-17-2006, 02:26 PM
Is it possible (with the speaker removed) to reach your hand between the baffle board and the grill cloth, then tap the orig screws forward from inside the cab?
Oh man, I just re-read this and it sounds like I'm suggesting to pound the screws deeper into the baffle board. Well, that's about the last thing I would have in mind, my intent was to gently remove the orig screws and, if possible, replace them with longer ones.

But...I just grabbed one of my Super Reverbs, pushed on the grill, and it only had about " flex before hitting the baffle, so Tom looks to be right about anything coming out the front.... :(

steveokla
03-18-2006, 02:59 PM
Bad news. Given crowding in the amp, it will not accomodate the 3/4 inch stock for a false baffle board.

I've done a lot of searching under 'barrell nut', T-nuts. 'connectors', etc. I've found some, but none small enough--the studs/machine screws in the amp are 8-32.

I did check for play between the baffle board and grill as suggested but, alas, as someone pointed out, it's only about a half inch. Might be stretched another 1/4 inch safely, but I figure these machine screws have to be 1 1/2 or two inches--that's likely pushing it too far for safety.

Please let me hear any other suggestions or other specialty hardware. Thanks, Steve

Zilch
03-18-2006, 04:26 PM
Surprisingly, the holes in the driver are spec'd at 9/32" (0.281"). I didn't believe it myself, until I just checked. A 1/4" bolt goes through. You may want to confirm that on yours. I assumed they were sized for the #10-32 screws typically used to mount them, but, no, apparently.

Like you, I don't find headed binding barrels as small as #8-32.

However, standard 1/4" OD Female Threaded Round Standoffs are available in #8-32 in lengths from 1/4" to 2". Spin a stainless steel one of the appropriate length on each stud, then secure the driver with #8-32 screws.

They're fully threaded through in lengths up to 1". I'd use button-head hex cap screws, probably, plus washers, if required, to mount the K130.

Also available at the link I provided above in brass and aluminum....

Will that work?

steveokla
03-18-2006, 05:05 PM
Surprisingly, the holes in the woofers are spec'd at 9/32" (0.281"). I didn't believe it myself, until I just checked. A 1/4" bolt goes through. You may want to confirm that. I assumed they were sized for the #10-32 screws typically used to mount them, but, no, apparently.

Like you, I don't find headed binding barrels as small as #8-32.

However, standard 1/4" OD Female Threaded Round Standoffs are available in #8-32 in lengths from 1/4" to 2". Spin a stainless steel one of the appropriate length on each stud, then secure the driver with #8-32 screws.

They're fully threaded through in lengths up to 1". I'd use button-head hex cap screws, probably, plus washers, if required.

Also available at the link I provided above in brass and aluminum....

Will that work?

Zilch--I think that will work--can you tell me where I might find the 'standoffs'? Thanks so much, Steve

steveokla
03-18-2006, 05:08 PM
Zilch--I think that will work--can you tell me where I might find the 'standoffs'? Thanks so much, Steve

My fault--in my excitement, I didn't see your reference to the site--I've found them there and will order up a couple different lengths and give it a try. Much appreciated! I'll let you know how it goes. Regards, Steve

Zilch
03-18-2006, 05:16 PM
COOL! :thmbsup:

You can sell a "Kit" on eBay if it works.

"JBL Mounting Kit for Vintage Fender Amps"

[Forum gets 5%.... :p ]

Earl K
03-18-2006, 06:21 PM
NICE WORK ZILCH !

- GOOD SLEUTHING ! :)

Hamilton
03-18-2006, 08:32 PM
Yikes! Zilch, the bloodhound!

edgewound
03-19-2006, 01:18 PM
Surprisingly, the holes in the driver are spec'd at 9/32" (0.281"). I didn't believe it myself, until I just checked. A 1/4" bolt goes through. You may want to confirm that on yours. I assumed they were sized for the #10-32 screws typically used to mount them, but, no, apparently.

Like you, I don't find headed binding barrels as small as #8-32.

However, standard 1/4" OD Female Threaded Round Standoffs are available in #8-32 in lengths from 1/4" to 2". Spin a stainless steel one of the appropriate length on each stud, then secure the driver with #8-32 screws.

They're fully threaded through in lengths up to 1". I'd use button-head hex cap screws, probably, plus washers, if required, to mount the K130.

Also available at the link I provided above in brass and aluminum....

Will that work?

I did a search on female threaded standoffs but couldn't find any with threads bigger than 6-32.

Nice find, Zilchster...good work!!:) :applaud:.Shoulda done my search right inside McMaster rather than Google...duhhh!!!

Zilch
03-19-2006, 03:39 PM
I did a search on female threaded standoffs but couldn't find any with threads bigger than 6-32.I have some in my anechoic wall of "stuff" here, so I KNEW they were available. :p

Discovering the actual size of the mounting holes in the driver frames was the breakthrough in finding a solution.

I hope Steve confirms that before ordering the spacers.... :yes:

Tom Loizeaux
03-19-2006, 04:46 PM
[QUOTE=steveokla]
I recently picked up a nice K130 for my Vibroverb, but, turns out, the mounting screws in the amp are nearly 1/4 inch too short (the original CTS speaker is a thin, stamped frame, versus the heavy cast frame of the JBL).

I find this a little surprising.
I measured the screw length protruding out from the rear of the baffle board on a '62 Fender amp and a '66 blackface amp. The '62 measured 7/8", while the '66 measured 3/4". I also measured the thickness of a, E140 frame with gasket and found it to be 11/16" (1/16 less then 3/4")
Though these aren't the exact same componants you're dealing with, I think you might be able to get a nut to catch on your existing Vibroverb screws.

Always be very careful when placing a speaker over mounted screw ends. Be sure the holes line up with all the screw tips before pushing the speaker in place!

Keep us posted.

Tom

57BELAIRE
03-24-2006, 06:25 AM
Here's something to consider....before you start modifying a vintage amp especially when it's collectability is an issue, make sure the new speaker (130) will suit your needs.

Years ago I yanked all four 10 in. stock (CTS/Oxford?) speakers from my '65 Super Reverb and replaced them with Altec 10's.

Know what? I HATED IT!!!

The amp went from a fat bluesy tone machine to a sonic weapon capable of inflicting aural damage at close range.Gone was that warm fuzzy overdrive and in it's place was a hard, shrill attack...much more suited to steel guitar or chunky rhythms.

I thought the upgrade would make what was good even better....it didn't. I ended up using two Altecs instead and it worked great...SO...mayby it would be prudent to try the 130 in a similar open-back cab and see if that's the sound you're looking for. If it is, then you can go ahead with the upgrade utilizing any of the wonderful suggestions provided by our esteemed Forum members.

edgewound
03-24-2006, 08:48 AM
Years ago I yanked all four 10 in. stock (CTS/Oxford?) speakers from my '65 Super Reverb and replaced them with Altec 10's.

Know what? I HATED IT!!!

The amp went from a fat bluesy tone machine to a sonic weapon capable of inflicting aural damage at close range.Gone was that warm fuzzy overdrive and in it's place was a hard, shrill attack...much more suited to steel guitar or chunky rhythms.

I thought the upgrade would make what was good even better....it didn't. I ended up using two Altecs instead and it worked great....

That just go to show that too much of a Lansing thing can be bad....

But it only took 2 Altecs....to flat blow away 4 Oxfords:applaud: ...with 2 Altecs left over!!!

ddeand
03-26-2006, 07:50 PM
Given that the baffle board comes out of the amp, it should be easy to handle the job. One possibility (I've done this before on a blackface Princeton Reverb) is to very carefully and slowly separate and spread the threads of the grillcloth at each bolt point so you can get a narrow screwdriver into the bolt head. I used a shish-kebob stick, and it worked pretty well. And, if my memory serves me correctly, the original bolts were reverse threaded to guard against stripping the wood. When I used standard bolts, I made sure I didn't over-tighten the nuts. The new bolts should be painted black before you insert them. When you're finished, carefully move the threads of the grillcloth back into place.

Another possibility would be to simply remove the grillcloth on three sides and make the change - then restaple the cloth. Of course, you lose the vintage staples.

And another possiblity - depending on if you can even find such an animal - would be to find a type of nut that has a long barrel into which the bolt can be screwed - the extension is on the nut rather than on the bolt. Here's a picture of one that was used to anchor some bolts on an old recliner (don't even ask me why I took it apart):
http://pic12.picturetrail.com/VOL417/1034344/1934051/135648734.jpg

Of course, the prongs would need to be removed on this one, but I think you can find these with a screw head or a knurled head.

Good luck with the swap - those JBLs are awesome!

Dean