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View Full Version : 2447J on 2381...diaphragm options?



emilime75
01-02-2017, 08:20 AM
What are my options, and what would the best choice be based on the following criteria? Beryllium is not an option due to cost, so I'm looking at SL diaphragms.

1. Fit the 2447 motor/core and phase plug.
2. Work better than the 2447J on the 2381 horn.
3. 5 will be used, but only 3 of those(LCR) in a 3 way and the remaining 2(surrounds) will be 2 way.
4. All will be above an 8/10" mid bass/mid range, so extension below 1-1.2K Hz is not necessary. I believe this is about the lower limit of the 2381, anyway.

Reasons for wanting replacements?

1. The 2447J drivers I own came from a church install and were put into service in 2002, making them about 14-15 years old. I'm assuming fresh diaphragms couldn't hurt.
2. These will now be used in a home theater system, but music playback quality is equally, if not more, important.
3. Improve on SQ above 1K Hz, and extend higher than 2447J without using a UHF driver/horn.

Nominal impedance isn't important, these will all be active. Cost/diaphragm should be <$200, max. Is there a better horn/wave guide, that is readily available and costs <$200 that would be a better choice than the 2381? If so, would replacing said horn be worthwhile, or are the improvements minimal?

Thanks.

sebackman
01-02-2017, 08:40 AM
Hi emilime,

If you have a 10" or 12" below I would skip the 2381 and use the much smaller and more modern VTX F12/F15 waveguide / horn. You can buy them new for $65 from Speaker Exchange (search for STX).

Use search and you can find measurements I have done here on LH. They sound rather similar to the M2's, however that is possible but they do. I have both in several installations.

As for diaphrams I think the horns will make bigger difference. But talk to Cathy at SE she had some new SL's for about $110, D16R2451SL. The 4" SL's are all the same and measure the same.

Having been installed in a church I don't think the Ti diaphragms have aged much. They typically age when driven hard, too low XO, heat and moisture. These probably have seen neither. Pure age has probably little effect on the Ti's.

However the SL's does sound better for home use to my ears. Try first. Get the wave guides and try with Ti dia's.

Kind regards
//Rob

emilime75
01-02-2017, 12:52 PM
Rob, I tried searching for your measurements, but couldn't find them. Do you have a link to them?
EDIT: Is this it? http://www.audioheritage.org/vbulletin/showthread.php?36686-New-JBL-waveguides-5006812-90x50-vs-PT-F95HF

Over the last few weeks I've read all I could find on JBL horns/waveguides and the PT type did come up as a viable option. Could you elaborate on how it is better than the 2381, and why do you suggest it?

Are the F12 and F15 guides the same? I couldn't find dimensions of either.

Your comment on all 4" SL diaphragms being the same also has me curious. In what way are they the same? Do you mean interchangeable, or they will all sound the same? 2451SL are definitely the cheapest to source, but if the 52SL or 53SL are not much more, is there any benefit to them?

Thanks for your reply, I appreciate it.

1audiohack
01-02-2017, 05:12 PM
Hi emilime,
Having been installed in a church I don't think the Ti diaphragms have aged much. They typically age when driven hard, too low XO, heat and moisture. These probably have seen neither. Pure age has probably little effect on them...Kind regards
//Rob


Over here we have quite a few rock and roll churches with amateur volunteer sound people who wreck stuff pretty regularly. From a church here in the states guarantees nothing. :(

Barry.

sebackman
01-03-2017, 02:56 AM
Hi

Yes, you should find some useful information there. And I think there is also somemore info if you search in the "Compact Monitor" thread.

The VTX may look like a PT waveguide but it is not. The VTX is much more modern and measures better regarding both frequency response and phase. It's a different animal. I do not recommend using a PT guide given the low price and availability of the VTX waveguide. In fact I just bought a 6thpair J .

https://reconingspeakers.com/product/jbl-horn-lens-5006815-stx825/ (https://reconingspeakers.com/product/jbl-horn-lens-5006815-stx825/)

Yes, it is the same waveguide in VTX F12 and F15. Both of them use the D2(2430k) driver but I use 2450SL, 2451H, 2451SL, 2451Be and 2447's on them. -Allworking excellent. Mounting size is the same as the small sibling used with the 1” drivers albeit that is a much simpler horn and would not stand the weight of a 1,5” driver. If you plan to use a 2447’s you may have to make a support bracket to the driver due to the weight. PT-F95HF is also the same size.

Worth noting is that the UHF is better in the VTX so with an SL diaphragm you can do without any UHF unit. If you use a Be diaphragm they tend to fall off earlier so there a UHF may be valuable. I use a 045-1 with mine. Please see measurements in thread mentioned above.

To my ears the newer waveguide designs sound more like large dome's than horns but with the dynamics and resolution of a compression drivers retained. But what really matters is what your ears are telling you. The VTX is cheap at $65 so you can always try and compare.

Regarding the diaphragms the 2452 and 2453 use different diaphragms and they are not interchangeable with 2447, 2450SL and 2451. The connectors are mounted on the diaphragm, and exist from the driver facing back. 2452 is a newer more compact driver compared to the older cores and 2453 is a different core all together.

The first JBL with SL diaphragms, as far as I know, was the 2450SL when JBL designed the DMS-1 studio monitor back in the day. The SL’s have since been used in many PRO and K2 speakers. From what I can understand 2450SL core is identical to 2451 except for the bolt pattern, it is small on the 2450SL and large on the 2451.

2450SL bolts right up to the VTX waveguide but for 2447 and 2451 you need and adapter. A drawing is included in the mentioned thread. Just have them made locally in Alu and you are good to go.

All SL diaphragms fit all 4" cores and there are both 8ohm and 16ohm versions. I do have most variations and they look and measure the same using the same core. Worth notingis that all 476Nd diaphragms are 16ohms (8ohm DC) regardless of designation (D8R476Ndor D16R476Nd). A few diaphragms seem to have been coated also over the “Diamond edge”. I have seen pictures of such diaphragms but never seen them in reality. So fromwhat I can understand and from my experience you can get “any” SL diaphragm(except 2452 or 2453) and get the same result using the same cores.

And of course Barry is right, there is no guarantee that “Church duty” saves the diaphragms from being out of spec… I appears that church duty over here is somewhat less destructive… J .

Hope this helps

Kind regards
//Rob

emilime75
01-03-2017, 08:10 PM
I appreciate all of the info, Rob. I think I will try those VTX horns and 2451SL diaphragms in my 2447 cores. I'll figure out the mounting once I have the horns in front of me. In the mean time, could you provide the exact outer dimensions, W x H, of the horn?

ivica
01-05-2017, 06:16 AM
Hi

Yes, you should find some useful information there. And I think there is also somemore info if you search in the "Compact Monitor" thread.

The VTX may look like a PT waveguide but it is not. The VTX is much more modern and measures better regarding both frequency response and phase. It's a different animal. I do not recommend using a PT guide given the low price and availability of the VTX waveguide. In fact I just bought a 6thpair J .

https://reconingspeakers.com/product/jbl-horn-lens-5006815-stx825/
(https://reconingspeakers.com/product/jbl-horn-lens-5006815-stx825/)http://www.audioheritage.org/vbulletin/showthread.php?36686-New-JBL-waveguides-5006812-90x50-vs-PT-F95HF&p=375519&viewfull=1#post375519


Yes, it is the same waveguide in VTX F12 and F15. Both of them use the D2(2430k) driver but I use 2450SL, 2451H, 2451SL, 2451Be and 2447's on them. -Allworking excellent. Mounting size is the same as the small sibling used with the 1” drivers albeit that is a much simpler horn and would not stand the weight of a 1,5” driver. If you plan to use a 2447’s you may have to make a support bracket to the driver due to the weight. PT-F95HF is also the same size.

Worth noting is that the UHF is better in the VTX so with an SL diaphragm you can do without any UHF unit. If you use a Be diaphragm they tend to fall off earlier so there a UHF may be valuable. I use a 045-1 with mine. Please see measurements in thread mentioned above.

To my ears the newer waveguide designs sound more like large dome's than horns but with the dynamics and resolution of a compression drivers retained. But what really matters is what your ears are telling you. The VTX is cheap at $65 so you can always try and compare.

Regarding the diaphragms the 2452 and 2453 use different diaphragms and they are not interchangeable with 2447, 2450SL and 2451. The connectors are mounted on the diaphragm, and exist from the driver facing back. 2452 is a newer more compact driver compared to the older cores and 2453 is a different core all together.

The first JBL with SL diaphragms, as far as I know, was the 2450SL when JBL designed the DMS-1 studio monitor back in the day. The SL’s have since been used in many PRO and K2 speakers. From what I can understand 2450SL core is identical to 2451 except for the bolt pattern, it is small on the 2450SL and large on the 2451.

2450SL bolts right up to the VTX waveguide but for 2447 and 2451 you need and adapter. A drawing is included in the mentioned thread. Just have them made locally in Alu and you are good to go.

All SL diaphragms fit all 4" cores and there are both 8ohm and 16ohm versions. I do have most variations and they look and measure the same using the same core. Worth notingis that all 476Nd diaphragms are 16ohms (8ohm DC) regardless of designation (D8R476Ndor D16R476Nd). A few diaphragms seem to have been coated also over the “Diamond edge”. I have seen pictures of such diaphragms but never seen them in reality. So fromwhat I can understand and from my experience you can get “any” SL diaphragm(except 2452 or 2453) and get the same result using the same cores.

And of course Barry is right, there is no guarantee that “Church duty” saves the diaphragms from being out of spec… I appears that church duty over here is somewhat less destructive… J .

Hope this helps

Kind regards
//Rob

Yes, here VTX825 & 2450/51SL.... and more ...thank You

http://www.audioheritage.org/vbulletin/showthread.php?36686-New-JBL-waveguides-5006812-90x50-vs-PT-F95HF&p=375519&viewfull=1#post375519
http://www.audioheritage.org/vbulletin/showthread.php?36789-Compact-monitor