Stupid question: How to attach 075 to C38?

[EddieJ]

Each 075 has a clamp ring but it appears that I need some sort of adapter plate to attached it to the cabinet. Did JBL make such a thing? Or do I need to build an adapter plate?

This is my first experience with JBL and I am really looking forward to listening to these speakers. I have an 030 system and was hunting for a pair of empty C37s when I found some C38s at a good price. Based on comments in a different posting, I realize that the C38s may not be the best choice, but they are better than nothing. And until I find larger boxes I would like to get these ol' JBLs up and running.

Any suggestions on how I can mount the 075s to the cabinets? I am not handy with wood. I don't even own a saw.

[toddalin]

The clamp ring has a few holes around it's perimeter that secure it to the cabinet.

Put the tweeter in the ring and through the baffle board hole. Make a mark on the wood where these "perimeter" holes line up along the back of the baffleboard. Then you can remove the tweeter and ring and pre-drill these holes (~1/2" deep) to use wood screws to secure the ring to the wood.

Take the tweeter out of the ring and mount the ring, and when it is in place, insert and tighten the tweeter clamp with a regular screwdriver.

VERY IMPORTANT!!! BE SURE THAT YOU ORIENT IT OR LEAVE ROOM TO GET A SCREWDRIVER ON THE TWEETER CLAMP SCREW!

[BMWCCA]

Any suggestions on how I can mount the 075s to the cabinets? I am not handy with wood. I don't even own a saw.

I'm guessing your C38 cabinets have a hole to mount the 15" D130 and some other opening possibly covered with a screwed-on wooden triangular blocking plate. If so, is there a hole under the blocking plate? Is it the correct size for the 075 (3-3/16") or is it larger (LE175DLH mounting hole is 5-9/32")? A picture might help but I'm guessing you'll either need to cut a hole in the blocking plate or your cabinet's baffle board.

Does yours look something like either of these?

[EddieJ]

Thanks for your quick response!

There is a blocking plate in each cabinet that I unscrewed. Each plate measures 5 5/8" square. Would I need to router a hole in the blocking plate and screw in the clamp ring?

If that is all I need to do I can find a neighbor with tools.
I'll trace the inside of the clamp ring.

I wasn't sure if JBL made a plate to mount the clamp ring.

[BMWCCA]

Thanks for your quick response!

There is a blocking plate in each cabinet that I unscrewed. Each plate measures 5 5/8" square. Would I need to router a hole in the blocking plate and screw in the clamp ring? If that is all I need to do I can find a neighbor with tools. I'll trace the inside of the clamp ring. I wasn't sure if JBL made a plate to mount the clamp ring.

They probably did, but you don't need it and probably won't find one.

Without seeing what you have, I'd suggest simply tracing the opening in the baffle board onto the blocking plate while it's attached to the baffle. Then remove it and have a neighbor cut a hole the size of the 075 which I believe is 3-3/16". Someone else here can correct that dimension, after they get done arguing about wasting time elsewhere on this site.

Todd's suggestion for putting the 075 with the clamp in the hole and then marking the clamp screw holes is good and, as he says, make sure you orient it so you can tighten it after you mount it. Or just tighten the tweeter clamp before you put the blocking plate back in if you forget!

Good luck.

[EddieJ]

Thank you toddalin and BMWCCA for your terrific suggestions!

This should be easy. Since I'm learning as I go, I want to be sure I don't screw this up. I'll take some photos tomorrow night and post them.

You guys are great!

BMWCCA, I thought you might pass me off as an ignorant newbie when I said that I picked up a C38 when in my previous posting you and other JBL experts recommended a larger box. I did hear you and I will take your advice and continue to search for a C37 or perhaps a C40. I'm looking forward to replacing my EPI 90s with this 030 system.

[BMWCCA]

You guys are great!

BMWCCA, I thought you might pass me off as an ignorant newbie when I said that I picked up a C38 when in my previous posting you and other JBL experts recommended a larger box.

:dont-know When I first arrived here I had a pair of 030s in C37 and C35 cabinets one of which I'd owned for fifty years and everyone was telling me they'd work much better in the smaller boxes. I even got a pair of C50SM cabinets (4320) from Heather so I could shrink the box. Then Harvey Gerst came in and restored my faith in the big boxes. I always figured there had to be something to it because of the way JBL referred to the smaller "barons" as being "adequate", and for when a smaller box was requested.

But you didn't come here looking to sell something, you came to learn and enjoy. Like I did. Since I got here I've been "helped" by members to purchasing nine more JBL pairs in addition to the two I had when I got here (L112 since new).

I'd never ridden a motorcycle or turned a wrench on one when I bought my first in 1971. But a great bunch of guys helped me learn to work on it myself, and gave me something that influenced my life more than (almost) anything else I've done. And I've been paying back that debt to others for 35 years. Even if my expertise isn't up to that of those who hate this kind of conversation, I'll still try to help whenever I can. And mostly I'll encourage, when I can. Like others here did for me.

Now someone can chime in with some sappy Academy Award Speech comment, or get out the hook. I don't really care.

Have fun with your JBLs. They'll sound fine in the C38. I'm putting mine in a pair of C35s I've had for ten years, empty. Just for a change. Bi-amping them, too, with active crossovers.

[EddieJ]

Without you and the other JBL fanatics here, I probably would have given up and just sold the 030 system and moved along. It's much more fun to learn new things -- especially since I always admired JBL speakers -- and perhaps make a few mistakes along the way.

For instance I just realized that there are no mounting holes in the C38 for the D130. Yikes!!! (However, the cutout and cork border fit the D130. I'll post photos tomorrow evening and you'll see what I mean.)

Now I really feel like a dolt. I can't even mount a simple 030 system into a small box.

[BMWCCA]

I just realized that there are no mounting holes in the C38 for the D130. Yikes!!! (However, the cutout and cork border fit the D130. I'll post photos tomorrow evening and you'll see what I mean.)

Now I really feel like a dolt. I can't even mount a simple 030 system into a small box.

Do you know what they had in them originally? Most I've seen were built to take a 15" and used adapter plates for 12" or 14" speakers. There's a cork border on the baffle board??

A drill and some T-nuts and bolts from Lowe's might be all you need, but there have to be some holes in that baffle from the previous install. I'm looking forward to seeing your pictures. Don't give up.

[toddalin]

Is it the correct size for the 075 (3-3/16")

Drill this hole 3-1/8" instead of the JBL-published 3-3/16". You will get an almost perfect fit without and extra 1/16" of slop in the hole.

That's how I've done all of mine and I've never had one not fit in the hole. Some others on this forum also use a 3-1/8" hole.

I think that this is even more important when using the mounting clamp (as opposed to those that mount directly with four screws) because there is a little gap when the clamp tensions that could possibly leave an air gap in the cabinet.

I think that JBL specs the hole large at 3-3/16" to allow for unit to unit variation. This is more important if you are going to produce a bunch of tweets and a bunch of cabinets and each tweet is not specific to each cabinet, so they account for this variation, especially for those tweets that mount directly as the central hole may or may not be centered with the four bolts.

(I've yet to have an HL-91/HL-93 center in its hole with the bolts in place in the factory drilled holes in my L200 cabinets.)

[Baron030]

Another way to cut a perfectly sized hole for a 075 is to use a plunge router equipped with a 1/2" pattern router bit.

Pattern router bits have a ball bearing guide wheel that allows the cutter to follow a pattern.

And the perfect pattern for the job is a 075 mounting plate.

A while back I posted this idea once before, here is a link to it:

http://audioheritage.org/vbulletin/s...ad.php?t=10047 (Post # 7)

Baron030

[EddieJ]

As you requested here are some photos that might help.

This sounds like a ridiculously simple task.

Router the blank plate 3 1/8", drill 5 holes for the clamp ring, insert T-nuts (or just nuts and bolts?), secure the 075 and screw plate into the baffle board. Then drill four 3/8" holes for the D130 and insert 5/16 T-nuts.

Are my measurements correct?

[toddalin]

As you requested here are some photos that might help.

This sounds like a ridiculously simple task.

Router the blank plate 3 1/16", drill 5 holes for the clamp ring, insert T-nuts (or just nuts and bolts?), secure the 075 and screw plate into the baffle board. Then drill four 3/8" holes for the D130 and insert 5/16 T-nuts.

Are my measurements correct?

"I am not handy with wood. I don't even own a saw."



Forget the plunge router! Just get a 3-1/8" hole saw (attaches to the drill) from a home supply place. It is a fairly common size and you will also need to buy the center bit that goes in the drill that allows you to mount the hole saw.





You don't need all five screws to hold the tweeter. Two or three will do fine and they can be small wood screws. You can see the obvious spacing for these two configurations. Just be sure to use screws that are shorter than your wood is thick so they don't come through the front. And if you pre-drill these holes, use a piece of masking tape on your drill bit as a depth gauge so you don't come through.

Your cabinet is already set up to use the external clamps to hold the woofer in place. You appear to just need the mounting kit. It is basically four "clamps" that screw into the cabinet face and secure over the lip of the woofer and are held into the cabinet with machine screws into T-nuts located inside the cabinet face. I have no idea of the availablity, cost, or part number for the kit. Someone else should be able to help you out there.

Also, your tweeter mount plate looks kind of flimsy to me (but could just be illusion or even stock). I would use 3/4"

[subwoof]

If you want to be real cute, holesaw with the 3.125 bit and then remove the horn from one tweet, place it in the hole and use a 11/32 bit on 2 holes ( 180 degrees apart ).

Get 2 8-32 bolts that are 1" longer than the originals and you can now mount the tweets with those 2 bolts.

Be sure to save the original bolts for later.

This was the way we stuffed bullets into pre-made cabinets when there was just NO room for mounting plates..

sub

[EddieJ]

toddalin, terrific, fantastic advice!

The mounting plate is only 3/8" thick, so 3/4" plywood makes much more sense. Do you agree?

RE: woofer mounting kit, clamp set ? ? ?
There had to be a way to attached 15" woofers without drilling. There are 4 holes on the outside of the 15" cutout with T-nuts and 5/16" bolts. So I'd bet my life savings that Madoff is carefully investing for me, that JBL had some type of "clamp" set. Good call, toddalin.

The big questions is: where can I find 8 of these "clamps".
Do you have a creative solution that might work?
I would rather not drill holes into the baffle board. I typically drink 3-5 double espressos before lunch. Then it's martini time.