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Thread: Large format HF drivers

  1. #46
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    Horn for 2" compression driver

    http://www.partsexpress.com/pe/showd...number=270-204

    A link to the horn I'm planning to use is above. My cabinet width is a tad narrow so the 15 inch horn width fits OK.

    I suppose I could squeeze in a 2405 slot but I had not planned on this.

  2. #47
    Obviously... not a golfer grumpy's Avatar
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    Vernb... I'd expect the 2350+2445+2225 to need a different crossover from the S3100.
    I believe the 3100's horn -is- more in the Constant Directivity family (albeit asymmetrically).
    I'd also expect your crossover could be made with much less complexity.

    Autotransformer? an inductor wound with taps... the taps act act as regular transformer,
    but with a common (not isolated) leg. They are custom designed and wound, and
    therefore not readily available in particular inductances and tap values.

    Robertbarch will need something at least similar to a 3115A or 3110A... or go active,
    or completely custom.

  3. #48
    RIP 2011 Zilch's Avatar
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  4. #49
    Administrator Robh3606's Avatar
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    The 2350 is an old school Radial. Very little compensation is needed as it uses the directivity to compensate on axis. With the extended response of a 2445 compared to a 2440 you may not have to do all that much beside the main crossover point.

    http://www.lansingheritage.org/image...orns/page3.jpg

    Rob
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  5. #50
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    Quote Originally Posted by grumpy View Post
    think that'd be a more natural cab match, w/ or w/o the bullet. Lots 'o dj cabs were built with
    essentially those parts (15" bottom, 2370+driver on top) and sounded pretty good in
    that environment.
    Here's a pair essentially ready to go: (no affiliation): http://cgi.ebay.com/JBL-SR4725-PAIR-...QQcmdZViewItem

    John

  6. #51
    Senior Member Ducatista47's Avatar
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    Quote Originally Posted by grumpy View Post
    Autotransformer? an inductor wound with taps... the taps act act as regular transformer,
    but with a common (not isolated) leg. They are custom designed and wound, and
    therefore not readily available in particular inductances and tap values.
    If a picture is worth a thousand words, here are two (I think) on a board in the 3145 (for the 4345) Thanks to Ian for the image, found here:http://audioheritage.org/vbulletin/s...46&postcount=4 The 3145 is a very large, complicated piece. It feels more like an amp than a crossover in your hands.

    These are c.1983 vintage parts, many from Mexico. Perhaps that explains the "TOLTEC" on them.
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  7. #52
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    55030 Tapped Autotransformer


    Tapped Autotransformer

    JBL used them as voltage drop devices in old crossover networks to match very high efficiency compression drivers to much lower efficiency dynamic drivers. Since they are reactive devices they present impedance problems unlike fixed resistors. The fixed resistor packs as used in the L250 and 250Ti are a superior solution. Note that the L250 also used a tapped autotransformer on the 044. I think that was the last time Greg used such a device in his crossover network designs.

  8. #53
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    I bought a pair of JBL SR4725 a few months go. I took the components out and mounted them in a furniture-grade cabinet.

    This is a kick-butt system that I enjoy very much.

  9. #54
    Senior Member vernb's Avatar
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    Quote Originally Posted by robertbartsch View Post
    I bought a pair of JBL SR4725 a few months go. I took the components out and mounted them in a furniture-grade cabinet.

    This is a kick-butt system that I enjoy very much.
    that's a great two way for the home. Did you do any mods to the x-over?
    Vernb

  10. #55
    Senior Member vernb's Avatar
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    So did anyone ever find a schematic for a two-way x-over at 500hz with CD comp (HF boost), without tapped inductor and without L-pads?

    I sure hope we do one fine day.....

    Vernb

  11. #56
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    Quote Originally Posted by vernb View Post
    So did anyone ever find a schematic for a two-way x-over at 500hz with CD comp (HF boost), without tapped inductor and without L-pads?
    Nope, I don't like 500 Hz crossover frequencies so I wouldn't waste time looking for one. Maybe someone else will.

  12. #57
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    Tweeter needed too?

    So, with the horn I'm planning to use with the 2425, the HF roll-off would be significant and would require a tweeter like a 075, 077 or 2402, etc?

    The cabinet I'm using is on the narrow and short side, so adding this would not be easy, I suppose.

  13. #58
    Senior Member vernb's Avatar
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    Quote Originally Posted by robertbartsch View Post
    So, with the horn I'm planning to use with the 2425, the HF roll-off would be significant and would require a tweeter like a 075, 077 or 2402, etc?

    The cabinet I'm using is on the narrow and short side, so adding this would not be easy, I suppose.
    well even though the HF roll-off is significant, you can easily use the 2425 without a tweeter. Both the 4430 and S3100 speakers do this and sound great. I copied the x-over from JBL S3100 to use in my 2-ways and it works absolutely great without the need for a tweeter.
    Both 4430 and S3100 have incorporated a HF boost in the x-over.
    Vernb
    Last edited by vernb; 10-16-2008 at 11:56 PM. Reason: forgot something

  14. #59
    Senior Member jerv's Avatar
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    FWIW, this is a filter (no L-pad, no transformer) I made for the 2226H and the 2425J on a 2370 horn.

    http://www.audioheritage.org/vbullet...4&postcount=18

  15. #60
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    I worked out a high frequency compensation circuit for the 2425J/2370 combination when I was doing my surrounds.

    I started with the basic L200B circuit to match my LCR, but instead of using a separate circuit for a 2402 as my LCR do, I kept it a 2-way.

    I felt that the HF compensation was definitely necessary and greatly improved the sound.

    I worked it out through trial and error using parts I had at hand and the Behringer. I kept my resistor values consistent with the Mills offerings and caps consistent with the Solen offerings at PE.

    I initially made up resistor values to simulate their offerings, then once I had decided on the values, ordered the Mills equivelents. I used caps I had around and once these values were decided, I ordered Solens with Theta by-pass caps.

    I actually worked out the compensation for both the JBL 2370 and P-Audio "9-inch butt-cheek" replica. Wow, I never would have thought they would be so different to get a similar hign end response! Actually, the 2370 did a little better than the P-Audio horn for extension and smoothness. I would have used them except for the WAF of the horns hanging under the four surround speakers in the living room. The external horns also helped the bass response by virtue of the increased cabinet volume. Alas, aesthetics trumped fidelity.

    These are being used with low efficiency, 12-ohm woofers (JBL W10GTI) and are really smooth. The crossover is ~800 Hz.

    When I use the same crossover on my 2235s, I don't get the woofers to go all the way up to the horn. I attribute this to the fact that the 2235 was reconed at 8 ohms and the original L200B was designed for a 16 ohm woofer. If I put an 8-ohm resistor in series with the woofer, it extends the woofers extension so that it better meets the horn. (But doing so will get you flamed around here.)

    I would think that using an 8-ohm woofer, you could use this as the 500 Hz woofer crossover. To extend the horn a little lower, I would up the size of the first horn cap from 16.5 mH to 20 mH. When I install the 2312 horns to replace the 2307s, I'll increase these caps to 18 mH as was done in some of the JBL offerings with the 2312.

    If this is of interest, I'll try to draw up and post the circuit.

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