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Thread: Truextent Diaphragms in JBL four-inch compression drivers

  1. #46
    Unabashed Speakerholic cosmos's Avatar
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    Quote Originally Posted by eso View Post


    Aren't those just the cutest little radial horns ever?
    Very nice looking horns. What are the two notches on the top and bottom for?

  2. #47
    Super Moderator yggdrasil's Avatar
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    Those 476Be curves are looking insanely good!
    Johnny Haugen Sørgård

  3. #48
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    Quote Originally Posted by yggdrasil View Post
    Those 476Be curves are looking insanely good!
    They sound alot better than they look but you should see a waveguide/476Be curve.

    JBL has stated that the only way they might be able to make the 476Be any better would be to go to a five slot phase plug but the cost/performance probably wouldn't be justifiable. The JBL curves were done in the anechoic chamber with the usual 2.83 volts input. That kind of input is deafening outside a chamber.

  4. #49
    Senior Member eso's Avatar
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    Quote Originally Posted by cosmos View Post
    Very nice looking horns. What are the two notches on the top and bottom for?
    According the Steve Schell, who is a walking encyclopedia of things Lansing, JBL, Altec and RCA among others, the designer of these was never fully satisfied with anything and continually sought refinement. The slots were introduced in the "A" series, I believe, as a sort of mechanical notch filter to alleviate some artifact in their sound.

    As the slots remained in the horns through the final "C" series I suspect they have a positive effect. I went to pretty good lengths to make sure they were as identical in size, shape and location as possible so my wooden versions will have comparable performance to the originals.

    eso

  5. #50
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    Quote Originally Posted by Mr. Widget View Post
    I was curious about the mass break point of the Truextent diaphragms... I assume it was clearly visible in the unfiltered plots?
    I'm just not seeing it. I guess we'd need a PWT plot. Jerry calculated the breakpoint of one 476Be at 4733 Hz this morning. I would imagine it is between 3 kHz and 4.5 kHz depending on the core. :dont-know

  6. #51
    Senior Member doucanoe's Avatar
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    Wow, very interesting stuff guys! Thanks for taking the time to do the analysis, 4313B

    I guess this confirms what I find so involving about my own 350Hz Edgars. Also, that I really need to hear the Yuichi horn and the TruExtent diaphragm. Unfortunately, thats probably going to require a trip east for me.

    RC
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  7. #52
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by 4313B View Post
    I'm just not seeing it. I guess we'd need a PWT plot. Jerry calculated the breakpoint of one 476Be at 4733 Hz this morning. I would imagine it is between 3 kHz and 4.5 kHz depending on the core. :dont-know
    You know, I mis-posted... what I was looking for was a secondary resonance peak. But, I can't see that from your plots either.

    Yes, for the mass break point to be clearly defined we would need a plane wave tube... these horns all add too much coloration to really see what is going on. As good old Al Klappenberger posted back during Project May, without a PWT, you really don't know what you have.


    Widget

  8. #53
    Unabashed Speakerholic cosmos's Avatar
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    Quote Originally Posted by doucanoe View Post
    I guess this confirms what I find so involving about my own 350Hz Edgars. Also, that I really need to hear the Yuichi horn and the TruExtent diaphragm. Unfortunately, thats probably going to require a trip east for me.

    RC
    If anyone is interested, both will be playing at AKFest 2010 in Novi, MI on May 1st and May2nd. In addition, in the listening room I am Co-Hosting, I will have my new "Cosmos" horns, which are really good. AKFest is a really neat gathering of new and vintage gear and down to earth, relaxed atmosphere.. Frankly, it's a blast!

  9. #54
    Senior Member Ian Mackenzie's Avatar
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    Details of crossover network as requested.

    The actual resister values are quite flexible to tailor the response and this is only an example.

    The topology is what is important.

    Response image is the raw driver and horn.

    The actual values may need to be modified as there are differences in the throat and flare geometry of the Yuichi horn.

    This won't be up here indefinately.
    Attached Images Attached Images  

  10. #55
    Senior Member doucanoe's Avatar
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    Quote Originally Posted by cosmos View Post
    If anyone is interested, both will be playing at AKFest 2010 in Novi, MI on May 1st and May2nd. In addition, in the listening room I am Co-Hosting, I will have my new "Cosmos" horns, which are really good. AKFest is a really neat gathering of new and vintage gear and down to earth, relaxed atmosphere.. Frankly, it's a blast!

    Yes, I know. I listened to your jbl ewaves last year in your room. I think that you may have visited ours also. I was rooming with Retro Stereo (Greg). Your new horn creations are high on my "wish to hear" list also!

    I apparently don't make long lasting first impressions, Dan


    RC
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  11. #56
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    Thumbs up

    Quote Originally Posted by Ian Mackenzie View Post
    Details of crossover network as requested.
    Thank you!

  12. #57
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    Quote Originally Posted by Mr. Widget View Post
    You know, I mis-posted... what I was looking for was a secondary resonance peak. But, I can't see that from your plots either.
    You can see one in #7 which is right where JBL said I would find it, around 18 kHz. The 476Be occurs at around 21 kHz.
    Quote Originally Posted by Mr. Widget View Post
    Yes, for the mass break point to be clearly defined we would need a plane wave tube... these horns all add too much coloration to really see what is going on.
    Yep, it's easier to just figure it out mathematically if you know the Bl factor and the moving mass.
    Quote Originally Posted by Mr. Widget View Post
    As good old Al Klappenberger posted back during Project May, without a PWT, you really don't know what you have.
    Yeah but do we really care since we aren't designing drivers? We're playing with the cards delt us.

  13. #58
    Unabashed Speakerholic cosmos's Avatar
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    Quote Originally Posted by doucanoe View Post
    Yes, I know. I listened to your jbl ewaves last year in your room. I think that you may have visited ours also. I was rooming with Retro Stereo (Greg). Your new horn creations are high on my "wish to hear" list also!
    Ron,

    It sounded like you were not planning on coming to AKfest. I was attempting to entice you a little..

    For me, last year was more about just having fun at the Fest and less about higher end, as it was in the years that I brought KLH Nines, JBL 250Ti-LE and Yamaha NS1000. This year, however, I am teaming up with Kegger in a room. He's providing the chrome top stuff and I am providing the speakers. They'll be the new horns with 2445/TrueXtents and either E-145 or Lambda TD-15 woofers in a 2401 style cabinet. There may be a surprise or two.. Time will tell.. I always try to get more ready than I am able.

    I think it'll sound better than the 4648/E-Wave combo.

  14. #59
    Unabashed Speakerholic cosmos's Avatar
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    Quote Originally Posted by Ian Mackenzie View Post
    Details of crossover network as requested.

    The actual resister values are quite flexible to tailor the response and this is only an example.

    The topology is what is important.

    Response image is the raw driver and horn.

    The actual values may need to be modified as there are differences in the throat and flare geometry of the Yuichi horn.

    This won't be up here indefinately.
    Thank you very much, Ian!

    I almost missed it.. (Whew)

  15. #60
    Senior Member doucanoe's Avatar
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    Quote Originally Posted by cosmos View Post
    Ron,

    It sounded like you were not planning on coming to AKfest. I was attempting to entice you a little..

    For me, last year was more about just having fun at the Fest and less about higher end, as it was in the years that I brought KLH Nines, JBL 250Ti-LE and Yamaha NS1000. This year, however, I am teaming up with Kegger in a room. He's providing the chrome top stuff and I am providing the speakers. They'll be the new horns with 2445/TrueXtents and either E-145 or Lambda TD-15 woofers in a 2401 style cabinet. There may be a surprise or two.. Time will tell.. I always try to get more ready than I am able.

    I think it'll sound better than the 4648/E-Wave combo.

    I really would like to be able to make it again this year, Dan, but unfortunately it's not in the cards for me. Greg has been doing his best to "entice" me also

    Always something interesting going on in your room. With the teaming up with Kegger and his tubeware, I'm sure this year will be no exception.

    RC
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