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Thread: My new project: 4438

  1. #1
    Senior Member Guido's Avatar
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    Cool My new project: 4438

    Hi All!

    This is a first impression about my new project.
    I call it 4438

    Dimensions would be roughly 160 x 65 x 50 cm (HxWxD)


    Any comments, suggestions, hints, whatever?
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    Last edited by Guido; 02-25-2004 at 11:39 AM.
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    I'm pretty certain a copy of the 4435 crossover isn't going to work with another horn. Since the horn has a 1.5" throat I would go with the 2430 driver if you can afford it. JBL claims it is their lowest distortion compression driver ever.

  3. #3
    Senior Member Guido's Avatar
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    I did a lot of research for this new horn. It is very similar to the 2344.
    Nearly same dimensions, same DI, same depth.....
    Just overall improved design.

    For the 1,5" I try to use an adaptor.

    BTW: The 2430 is much cheaper than a 2426.
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    Guido, I'm confused. The top enclosure goes to 100Hz? and the
    driver is a 2234H?

    I've also thought of this kind of driver arrangement; ie having
    two bass drivers up to about 100Hz and then cutting one of them off, letting only a single one carry on the the horn x'ver. but then
    how to take care of level matching at - say - 100Hz when going
    from two to one 2235 - I think you meant. If you are going to
    1kHz with both bass drivers as the 4435 speaker does, I'd be worried about interference. The drivers are significantly far apart judging by a 1kHz wavelength to get serious lobing.... I don't know though.

    My idea was to somehow use two 2235's to about 100Hz, then continue with one of them to about 500Hz and then xover to midrange horn and then tweeter horn. Can't for the life of me figure out how to do it though without extensive equalization via a likely very complicated xover.

    - regards, Guenter

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    Administrator Robh3606's Avatar
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    Why stack it like an MTM?? Just put the sub at the base and stack above. You should be able to get the horn height right. Just use a series coil like the 4435.

    Rob

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    Senior Member Guido's Avatar
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    Guenter

    The xover frequencys are exactly copied from the 4435. No invention from my side
    One of the 2234 only goes up to 100 Hz, the other 2234 to 1000 Hz. That is given from the 4435 design.

    Rob
    Why MTM? I like the style and it should work. I do not have the space for a wide speaker like the 4435.

    I was testing the 2344 horn(s) from Ralf. No doubt they sound good but they are sold out.
    Then I was testing the PH316 from PAudio. Similar to the 2344 but 1,5" throught and a wider gap. Sounds different but not bad. Now I'm waiting for the AE Waveguide. I'm very curious. from the data it should be even better than the 2344 and it is available and it is cheap. 90 Bucks I think.
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  7. #7
    Senior Member Guido's Avatar
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    PH 316

    Same size than 2344
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    Super Moderator Hofmannhp's Avatar
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    4438

    Hi Guido,

    a nice project.......but I agree with rob.... if you want to use only one woofer from 100 Hz above, then you do not have to take the MTM stacking.
    Another idea...please think about to use a UHF driver (2405)...thats the only missing thing in the 4435 (sometimes). I like the crispening of them in my other cabinets.

    HP
    Please help us save more info about the vintage systems. Let us register your speakers and drivers.

  9. #9
    Senior Member Guido's Avatar
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    Re: 4438

    Originally posted by Hofmannhp
    Another idea...please think about to use a UHF driver (2405)...thats the only missing thing in the 4435 (sometimes). I like the crispening of them in my other cabinets.

    HP
    I know the 2405 from my 4343. NICE!

    I think the new Waveguide will improve the top end.
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    [QUOTE]Originally posted by Guido
    [B]Guenter

    The xover frequencys are exactly copied from the 4435. No invention from my side
    One of the 2234 only goes up to 100 Hz, the other 2234 to 1000 Hz. That is given from the 4435 design.

    Well, very strange then. I had wondered about this in the past, ie two 15" drivers going up to 1kHz, but the technical specifications of the 4435 speaker do _not_ mention a 100 Hz x'over. It does make sense, but where does JBL say that??
    Again, is 2234 = 2235?? I assume so.

    Why MTM? I like the style and it should work. I do not have the space for a wide speaker like the 4435.

    I assume by MTM you mean the d'Appolito type of configuration. If so, there is a good reason for this I believe. Having one woofer only you get the infamous 'floor bounce' ie cancellation (forgot who pioneered/investigated this problem first - believe it was Allison) By having the two woofers you tend to smooth out the 'suckout' in the amplitude response because of the 'floor bounce'.

    - Guenter

  11. #11
    Senior Member Guido's Avatar
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    2234 is 2235 without the massring. Do a search, there is a thread for this.

    The second woofer only to 100 Hz is stated in the tech data from this brochure:
    http://www.jblpro.com/pub/obsolete/443035.pdf

    Then you can see this in the xover schematic here:
    http://www.jblproservice.com/pdf/Net...%20Network.pdf
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    Guido, many thanks. I had not seen these more detailed spec sheets before. I am mainly perusing pro catalogs for information which, now, I realize are sometimes short on specifics.

    So, if I understand correctly, if the 4435 is biamped then one
    amplifier will drive just one of the 2234's while the 2nd amplifier will drive the second 2234 plus the compression horn. the 'midrange' refered to in the xover schematic presumably means the 2234 driver below the horn. right?

    seems I'm always learning more stuff here

    many thanks for the pointers. Now I'm starting to rethink my
    initial project for this coming summer

  13. #13
    Administrator Robh3606's Avatar
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    Hello Guenter

    When the 4435 is biamped both 2234 woofers are driven by the same amp. One is labled mid. Take another look at the switches. The Zobel gets droped on the "mid" and the only passive in circuit for the "woofer" is the 18mh choke and the resistors.

    Rob
    Last edited by Robh3606; 02-25-2004 at 09:42 PM.

  14. #14
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    Thanks Rob,

    I was expecting more of the circuit than it actually provides I believe. Specifically, considering - simple mindedly - around 100Hz I expected a level difference above and below this xover when one vs two of the 2234's are playing. therefore I thought that there must be some kind of amplitude contouring network. It doesn't appear to be there though. So, OK, the LF output is
    rolled off with the 18mH choke (at 100Hz presumably) and the mid
    output is only rolled off with a 2.6 mH choke that also forms part of an damped (with the 5R1 resistor) LC circuit that may have an ever so slight peaking/boost in the response. However, surely not enough to compensate for the LF woofer dropping out. am I missing something here??

    - thanks for any input

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