Question on how to mount compression driver in JBL Box

[gwho]

I recently picked up a pair of JBL boxes. The tag on the back says they are JBL 4502. I want to make a three way speaker with parts that I have. I would like to use a 2441 compression driver for the midrange. The 2441 has a 2311 horn on it. The 2311 fits in the stock opening. I also purchased a JBL/Selenium exponential horn that is supposed to sound better than the 2311. I would have to cut the opening bigger to fit the JBL/Selenium horn.

Did JBL support the back of the compression driver in the cabinet or is it suspended by the horn? I can't believe it could hold up that weight. How did they do it if the CD does need to be supported. A picture would be great if anyone has one.

I greatly appreciate any help you can provide.

Regards,
gwho

[Earl K]

Yes, you should support the driver .

Even a 2x4 ( run side to side / or front to back ) that the bottom of the driver rests on top of, will suffice .
- The 2x4 also acts as extra box bracing ( which is usually needed ).

One can get fancier by adding padding , adding plumbers strapping over the top to secure the driver in place ( if the box is stood end on end ) &/or a circular cut into the supporting wood ( lined with padding ) that is shaped to the driver .

:)

[gwho]

Earl K,

Thank you for the help and the instructions on how to do it. The only opening I have to work with is the woofer opening. I wish the back could be removeable so I could have easy access to the interior. Maybe I should cut an opening and make a removeable plate in the back for access. I will see what I can do through the woofer hole.

Regards,
Gary

[robertg]

I had a pair of those and they didn't have any bracing, however they came with the 2420 driver and the 2307 horn. The 2441 is a lot heavier, so bracing is a good idea.

[gcarlberg]

This is a interior shot of a saddle I built to support a 2446 on a 2311 inside a DIY 4345

Double thickness of 3/4 ply glued and screwed.



75958

[gwho]

Thank you for the picture. My boxes also don't have any bracing. I will add a brace as suggested. Thanks everyone.

Regards
Gwho

[gwho]

Thank you for the picture. My boxes also don't have any bracing. I will add a brace as suggested. Thanks everyone.

Regards
Gwho

[ivica]

I recently picked up a pair of JBL boxes. The tag on the back says they are JBL 4502. I want to make a three way speaker with parts that I have. I would like to use a 2441 compression driver for the midrange. The 2441 has a 2311 horn on it. The 2311 fits in the stock opening. I also purchased a JBL/Selenium exponential horn that is supposed to sound better than the 2311. I would have to cut the opening bigger to fit the JBL/Selenium horn.

Did JBL support the back of the compression driver in the cabinet or is it suspended by the horn? I can't believe it could hold up that weight. How did they do it if the CD does need to be supported. A picture would be great if anyone has one.

I greatly appreciate any help you can provide.

Regards,
gwho

Hi gwho,

I think that 2311 has to be used with 2308 lenses if You want to get JBL expected characteristics.
Without 2308 lenses 2311 or Selenium 2inch short horn You would get very narrow off axis response,and I will not suggest to use in such driver&horn combo. All of the mentioned is only my personal experience.
With 2308 the risponse off axis is very, very good.
Regards
Ivica

[gwho]

Hi Ivica,

Thanks for the advice. The boxes I bought have the velcro on them for the lens. I also saw pictures of the box with the lenses so I assumed that I might need them. I went on ebay and there is someone selling replica lenses so something is available. Would you know if there be any significant sonic difference between the 2311 and the HL-50N horns (with lens). The 2311 mounts flush. I would have to increase the hole size to mount the HL-50N because it mounts externally. All things being equal I would likely use the 2311 since it does not require any cutting but would consider the HL-50N if it would sound better.

Best Regards,
Gary

[ivica]

Hi Ivica,

Thanks for the advice. The boxes I bought have the velcro on them for the lens. I also saw pictures of the box with the lenses so I assumed that I might need them. I went on ebay and there is someone selling replica lenses so something is available. Would you know if there be any significant sonic difference between the 2311 and the HL-50N horns (with lens). The 2311 mounts flush. I would have to increase the hole size to mount the HL-50N because it mounts externally. All things being equal I would likely use the 2311 since it does not require any cutting but would consider the HL-50N if it would sound better.

Best Regards,
Gary

Hi Gary,

I have experience with 2311 and 2308 lenses only,
so may be quite good offer for 2308 like lenses, most of the forum members were satisfied:
http://www.ebay.com/itm/JBL-2308-L91-Style-KENRICK-SOUND-brand-new-Lenses-/251338534170
(http://www.ebay.com/itm/JBL-2308-L91-Style-KENRICK-SOUND-brand-new-Lenses-/251338534170)

I have HL14-50 horns too, but I am sure that mounting a kind of lenses has to be recalculated shape of
hyperbolic "V" shape relative to its directivity.

As You have 2311 horn, I would suggest You to use 2308 lenses with horn-driver combo.
regards
ivica

[1audiohack]

Hi Gwho!

I just bought a pair of 4502's to go in a gray scale rooom.

Mine have front baffles that have been hacked for other horns so I have to replace them. I have one grille so more work still.

The horn driver supports in the 4350's are sheet metal that bolt to two of the throat fasteners and clamp around a wooden cross brace.

That's probably the most difficult to create but I can find some pictures possibly if you are interested.

I am still trying to decide what to do with mine.

Barry.

[gwho]

gcarlberg,

Thanks for the picture! How did you cut the saddle. Was that just a jigsaw cut, router, or some other way to make that semicircle.

Regards,
Gary

[gwho]

Ivica,

I agree with you. I will use the 2311 and pick up a pair of the lenses. My goal is to make this as easy as possible.

Regards,
Gary

[gwho]

Hi 1audiohack,

Thanks for letting me know about the 4350. I think I figured out how to support the CD if I make a saddle as disclosed by gcarlberg. There is some minor bracing along the walls that I can use in conjunction with the saddle that I can use to support it. I would also get a band that will go around the CD to hold it to the saddle to prevent any movement. If you look at my pictures the previous owner hacked up the woofer opening but it will still work with clamps.

Regards,
gwho

[gwho]

One final question. I would like to add a tweeter. I would like them in-line with the woofer and midrange. Would anyone know the center to center distance between the midrange and the tweeter in the 3-way version of this speaker. I have a pair of Selenium ST200 tweeters (looks like a JBL bullet tweeter but is smaller) but would like to know how significant using a 2405 of 2402 would be with this design. I also have a pair of 2402 bullet tweeters but both need new diaphragms (and I found the price for JBL diaphragms quite high).

Regards,
gwho

[grumpy]

Would anyone know the center to center distance between the midrange and the tweeter in the 3-way version of this speaker.

Can measure this evening if no one else has the answer.

[gcarlberg]

gcarlberg,

Thanks for the picture! How did you cut the saddle. Was that just a jigsaw cut, router, or some other way to make that semicircle.

Regards,
Gary

Hey Gary,

I got the outside dimension from the cut sheet in the JBL Library.

Made a rough cut with a jig saw, glued and screw the two pieces together and smoothed it out with a drum sander mounted in a drill press.

George

[grumpy]

Looks like 5 1/8" center to center. To get closer I'd have get out the calipers.
I viewed the mounting hole center values on one scale to get the above value probably within ~1/16"

[gwho]

George thanks for the tip on making the saddle.

Grumpy thanks for the center to center spacing.

Best Regards,
gwho

[ivica]

One final question. I would like to add a tweeter. I would like them in-line with the woofer and midrange. Would anyone know the center to center distance between the midrange and the tweeter in the 3-way version of this speaker. I have a pair of Selenium ST200 tweeters (looks like a JBL bullet tweeter but is smaller) but would like to know how significant using a 2405 of 2402 would be with this design. I also have a pair of 2402 bullet tweeters but both need new diaphragms (and I found the price for JBL diaphragms quite high).

Regards,
gwho

Hi gwho,

As it is known 2405 has much wider horizontal dispersion then 2402.

regards
ivica

[gwho]

Ivica,

I looked up the sheet and there is a significant difference. 140 degrees vs 40. I assume that the lens on the midrange is supposed to increase the dispersion greater to better match the 2405. I will try to find a pair of 2405 to use in my boxes.

Thanks
gwho

[1audiohack]

Late but here they are.

762867628776288

[gwho]

Thanks for the pictures 1audiohack. I guess my pegs are different. You can see the white colored pegs for the speaker cover on the picture of the open hole. I want to thank everyone for the help. I am posting a couple pictures to show what they look like (although I am not finished). I am using parts that I have on hand for the project (the woofer is a AE TD15H). I cut holes and picked up a pair of 2405H for the tweeters. I was able to put in a brace to support the 2441 driver. 763377633876339

[gwho]

One odd thing about the boxes that I picked up is that the previous owner took a jig saw to the woofer opening and opened the diameter almost to the screw holes. This is why I had to go with the external mounts. Luckily the TD15h has a slightly larger diameter than a JBL 2235.

Regards
gwho