MA-15 Clamps

[speakerdave]

I have a question about the MA-15 clamps. I have six sets. The clamps in two sets are heavy, nicely finished, natural metal color underneath and painted black on top, typical JBL product. The clamps in the other four are much lighter, a little smaller and have a sand-cast look under the silver (underneath) and black paint. It's definitely not the same metal. The screws and T-nuts all seem to be the same. Does anyone know if JBL actually made both types or if these second type are a knock-off? The second type I have in boxes with authentic-looking literature from the 70's and the Casitas Ave. address. The heavy, nicely finished ones I got with a pair of 2202 drivers a few months ago.

I have two concerns: One is whether I've bought knock-offs thinking I was getting JBL. The second would be a question about reliability.

Any help on this would be appreciated.

David

[boputnam]

Hey, Dave...

Can you post some pics...? I've noticed Widget has slightly different clamps than I do - as does the damned Aussie...

[speakerdave]

Not immediately. I don't have a digital camera. Let me see what my scanner will do.

David

[speakerdave]

Here you can see most of the differences.

[John]

Well i could tell you that the ones i recieved from JBL with the help of my broker "L-100" boputnam for my 4350 project are the same as the ones on the right hand side of your picture:D

[speakerdave]

Yes. The person I got those from probably bought them in the last ten years or so. If JBL made them both, those would be the more recent.

Thanks for the information.

David

[4313B]

The right hand side is the genuine MA15 clamp that we've all known and loved for the past 30+ years.

[speakerdave]

That answers it.

Thanks,

David

[boputnam]

Originally posted by Giskard
The right hand side is the genuine MA15 clamp :yes:

As on the 4345's...4345 Monitor Plans (http://audioheritage.csdco.com/vbulletin/showthread.php?s=&threadid=314) Thread.

[speakerdave]

Thanks, Bo.

That's a lovely big old badass woofer.

My flying BIN finger has got me in trouble here, fortunately not too bad--$12.50 a set. I've got an email out to the seller. We'll see what happens.

I'm trying to see how they got into the JBL boxes. I really don't suspect deliberate fraud. Somebody bought them, decided they suck, bought some real ones and dumped these in the boxes. They get sold at the estate sale and then show up on eBay.

Meanwhile I'm trying to think of some suitable use for these clamps. They look OK by candlelight.

David

[4313B]

Originally posted by speakerdave
Thanks, Bo.

That's a lovely big old badass woofer.

David It's a facade! That woofer is really only 16 ounces and is actually held in with double-stick tape. The clamps are used to make people think it is a "big old badass woofer". Oh wait... wrong thread... no... wrong forum... :slink:

[boputnam]

Dammit Giskard!!

:rotfl:

[andresohc]

Is there any benefit to using the kit as opposed to just using the mounting holes, tnuts and the screws. I have a my 2245Hs mounted with screws in each hole on the frame. Thats the way the (4645?) JBL sub cabinet came equipped.

[speakerdave]

Well, here's my final word on this. Both Alex and the seller (the latter rather adamantly) state that during a certain period JBL sent out both sandcast and diecast versions. I have no reason to doubt either of them, so that's it. Although not visually pleasing, the clamps may be seen as reliable, as far as I am concerned, and I plan to use them.

Thank you for all your assistance in clearing this up.

andresohc: reasons for using them. Well, first they're stylin' impressive. Two, they're faster because you can demount the woofer without taking the screws all the way out. Great for use on a test bed. Three, according to the JBL literature, they permit "a certain amount of flexibility in the diameter of the mounting cutout. . . ." That is, if you are trying to cut the holes with a sabre saw, you need these. Of course, I know Forumites all use the Jasper jig, so this last reason is unimportant. I doubt that any factory-built speaker ever showed up with these on. It would be much more expensive than just the screws and T-nuts.

David

[John]

My B460 came with them and bo,s 4345 came with them and the 4350-55.s came with them.

[andresohc]

I cant figure out a way to use the Jasper Jig for holes smaller then the diameter of the router. I ordered a Porter cable "magic edge router guide", It looks like it can make smaller holes.

[speakerdave]

Originally posted by andresohc
I cant figure out a way to use the Jasper Jig for holes smaller then the diameter of the router. I ordered a Porter cable "magic edge router guide", It looks like it can make smaller holes.

I think Jasper has another jig for smaller holes.

David

[speakerdave]

Originally posted by John
My B460 came with them and bo,s 4345 came with them and the 4350-55.s came with them.

Geez, I never noticed that in the literature, but I just checked and it's there. Thanks for that correction

David

[boputnam]

Originally posted by andresohc
I cant figure out a way to use the Jasper Jig for holes smaller then the diameter of the router. Hey, Andre...

That Model 200 cuts to 2-1/4 in diameter, and my plunge router has a 6-1/2 in diameter frame. Never had a problem. What has been your trouble...?

[andresohc]

I think I figured it out, I had a team of monkeys working on it all morning and we came up with the idea that the pin to anchor the center of the hole doesnt need to stick up through the top of the jig, it can stick down through the bottom of the peice. Thats what I get for trying to figure it out 1 am. Whats that saying about opening your mouth and removing all doubt?:D

[boputnam]

:rotfl:

Yea, and don't forget the really helpful trick: Use a backing board beneath the baffle being cut, and drill a guide hole through both. Router only half-way through, then filp-over the baffle, realinging the two boards with the guide hole. Finish the cut. This keeps both edges of baffle cut, front and back, clean without chips... :thmbsup:

[speakerdave]

Briefly, back to the clamps. I was just rereading the 4350/55 thread and ran across Giskard's posting of an image of the original foilcal for the 4350. If I'm not mistaken, the woofer clamps incidentally visible in the photo look a lot more like the sandcast version than the diecast. The wider throat is apparent in both and the roughness of the sandcasting is clearly visible in the one on the left.

David

http://audioheritage.csdco.com/vbulletin/showthread.php?s=&threadid=425&perpage=15&highlight=3107&pagenumber=3

[Alex Lancaster]

Dave:

If the alloy in the sandcast ones is correct, they are stronger than the diecast ones, just not so smooth.

Alex.

[speakerdave]

Originally posted by Alex Lancaster

If the alloy in the sandcast ones is correct, they are stronger than the diecast ones, just not so smooth.


Cool! That's good, because they're going to be hanging on to some 2242's.

David

[Mr. Widget]

Style A is from either EV or Meyer, I can't remember. It is a very light aluminum.

Style B is from a no name brand that I bought back in the 70's. It was sold in a kit with screws and cork gaskets just like the MA-15 but was half the price. It is a harder alloy than the JBLs.

Style C came from a 4320 circa 1962. You got me, they were actually called C50SM back then.

Style D is the current JBL product. They no longer sell the MA-15 kit but they do sell the clamps, screws and gaskets. They do not sell the clamps painted black. You have to do that yourself.

Widget

[speakerdave]

Apparently there was also a style E pictured above with the "current JBL product" and also pictured in the above cited thread ON a contemporary JBL product.

David

[speakerdave]

Originally posted by Mr. Widget

Style C came from a 4320 circa 1962. You got me, they were actually called C50SM back then.


That concurs with one of my sources who said that the current JBL diecast version was a third JBL casting.

David

[John Y.]

Originally posted by andresohc
Is there any benefit to using the kit as opposed to just using the mounting holes, tnuts and the screws. I have a my 2245Hs mounted with screws in each hole on the frame. Thats the way the (4645?) JBL sub cabinet came equipped.

andresohc,
The kits enable easier exchange of speakers. You don't have to remove the screws entirely to take them out - just slip out the brackets. One decided advantage in using the brackets is that the T-nuts are spaced further from the edge of the woofer cutout. With the use of MDF, etc. this can be quite an advantage since this material is subject to splitting around the holes if they are too close to the edge. Extreme care should be exercised in the assembly of the woofers using the normal bolt holes in MDF.

If something like Birch ply is used, I believe the holes spaced per the woofer mounting holes is entirely adequate. I further believe it probably results in a better seal if all eight holes are used. Just my opinion.
John Y.

[andresohc]

John Y,
Sounds good. I actually looked at my cabs today. I use clamps on the 2245Hs. With the other speakers I have been using the mounting holes. So far only on plywood not mdf. Your read on the MDF is spot on. I will have to convince OCS to order the brackets. They were befuddled by the pricing on the clamp and sold me their own clamps on my last try. Their clamps were too shallow to hold the 2245 and I had to build spacer blocks.

[andresohc]

John Y,
Sounds good. I actually looked at my cabs today, I use clamps on the 2245Hs, With the other speakers I have been using the mounting holes, but so far only on plywood not mdf. Your read on the MDF is spot on. I will have to convince OCS to order the brackets. They were befuddled by the pricing on the clamp and sold me their own clamps on my last try. Their clamps were too shallow to hold the 2245 and I had to build spacer blocks.

[Mr. Widget]

They may have been befuddled by the fact that the price today is 5-6 times higher than it was a year or two ago.

Widget

[HornForever]

John Y.

I agree with everything you said.

Regarding 2245H, I also wonder why JBL grouped 2 clamps together and hold speakers on 4 points, 90 degree apart, instead of evenly spaced the clamps around on 8 points, 45 degree apart, which should give more uniform pressure on speaker frame and provide better seal.

May be JBL did that for aesthetic purpose.