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Thread: Large format HF drivers

  1. #61
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    Quote Originally Posted by toddalin View Post
    If I put an 8-ohm resistor in series with the woofer, it extends the woofers extension so that it better meats the horn. (But doing so will get you flamed around here.)
    You're free to post whatever you feel the need to post so long as it remains within Don's guidelines. You can put all kinds of things in series with your woofers and post about the experiences as you see fit.

  2. #62
    Senior Member vernb's Avatar
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    Quote Originally Posted by jerv View Post
    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
    Thanks Jerv. Just what I needed
    Vernb

  3. #63
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    After many hours of testing, looking at the Behringer, and listening, this is what I came up with. It works very well with a low efficiency woofer (W10GTI ~81 dB@1 watt), but I only run the L-pad at less than 1/4 turn of the way so would probably be fine with something on the order of 90+ dB. To bring the horn in a little lower (for your intended ~500 Hz duty), I would replace the two 8.2 mfd caps with a single 20 mfd.


  4. #64
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    Is there a good reference book on reading electrical schematics and building simple circuts?

    I've search the web and the stuff I'm finding is too advanced for my knowledge level (zero)?

    Where do you buy electronic components, resistors, capicitors, boards, ect.?

  5. #65
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    Quote Originally Posted by robertbartsch View Post
    Is there a good reference book on reading electrical schematics and building simple circuts?

    I've search the web and the stuff I'm finding is too advanced for my knowledge level (zero)?

    Where do you buy electronic components, resistors, capicitors, boards, ect.?
    If you really want to understand, take the course. A classic textbook is: Robert L. Boylestad, Introductory Circuit Analysis. Been around for thirty years at least, any edition will do. Old cheap used paperback copies can be found at Abebooks for $5 shipped. Current edition $108 at Amazon. You need to have a sense of an ohm, an amp and a volt going in. You might begin, though, with a textbook on technical math, and you should have a good calculator. I took half the course long ago (passive elements) and dug out my copy a while back and have been spending what time with it I could. It's difficult, but in the long run, I think this is the only way to go.

    Parts Express, Madisound, Michael Percy Audio.

  6. #66
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    Quote Originally Posted by 4313B View Post
    You're free to post whatever you feel the need to post so long as it remains within Don's guidelines. You can put all kinds of things in series with your woofers and post about the experiences as you see fit.
    I did that with an Altec 515 a long time ago to trial a diy system. I put an 8 ohm resister in series and it raised the Qt considerably and extended the apparant extension in a Bass reflex setup. I then changed out the 515's , sold them for a grand and bought a pair of 2245H's. The improvement was a no brainer!...LOL

  7. #67
    RIP 2011 Zilch's Avatar
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    Quote Originally Posted by toddalin View Post
    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.
    Nope, wasn't that:

    http://manuals.harman.com/JBL/HOM/Te...L200B%20ts.pdf

  8. #68
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    Quote Originally Posted by robertbartsch View Post
    Is there a good reference book on reading electrical schematics and building simple circuts?
    http://sound.westhost.com/beginners.htm

  9. #69
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    Quote Originally Posted by Zilch View Post
    OK, but I still say that, at least in my case, a 16 ohm woofer would have worked better with it.

  10. #70
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    Quote Originally Posted by robertbartsch View Post
    So is a passive crossover at 500hz too low for a set up consisting of 2225 and 2445 drivers?
    You need to measure both drivers in the system you intend to build and then determine the correct crossover frequency.

    Quote Originally Posted by vernb View Post
    Well. It is hard if you don't know what to search for. I have been looking for a long time for a two way system for the 2445 drivers - with out luck.
    You really need to build your networks based on your specific application. I know it's a real PITA but that's the way to do it right.

  11. #71
    Senior Member jerv's Avatar
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    Quote Originally Posted by vernb View Post
    Thanks Jerv. Just what I needed
    Vernb
    Hope you can use it.
    If you decide to build it - please let us know what you think

  12. #72
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    Quote Originally Posted by 4313B View Post
    You need to measure both drivers in the system you intend to build and then determine the correct crossover frequency.

    You really need to build your networks based on your specific application. I know it's a real PITA but that's the way to do it right.
    But my specific application and drivers is/are the same as Jervs and the same as JBL 4673, and since I have no measuring equipment, I will build Jervs x-over and work my way from there. The reason for not building JBL 3115 x-overs from the 4673 is that they have tapped inductor, L-pads, and no CD comp (HF boost). Jervs doesn't.
    That's what I did with my first project: Drivers and horns were close to JBL S3100, so I made a S3100 x-over and then fine tuned it to the 1400pro driver (the main difference to the S3100).
    Vernb

  13. #73
    Senior Member vernb's Avatar
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    impedance and x-overs

    Only thing that now puzzles me is that most of the "so called" JBL 16 ohm compression drivers I have, actually do not measure 16 ohm. My 2445 measure around 12 ohm and my newly arrived 2482 measure around 10 ohm. Even my 2426J measure around 12 ohm.
    I don't know much about building passive x-overs, but I thought that the impedance of the driver meant quite a lot to the x-over point. So that a 500hz x-over for 16 ohm drivers will actually not x-over at 500hz if the driver measures only 10 ohm. Am I right ?

    Vernb

  14. #74
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    Quote Originally Posted by vernb View Post
    But my specific application and drivers is/are the same as Jervs and the same as JBL 4673, and since I have no measuring equipment, I will build Jervs x-over and work my way from there. The reason for not building JBL 3115 x-overs from the 4673 is that they have tapped inductor, L-pads, and no CD comp (HF boost). Jervs doesn't.
    That's what I did with my first project: Drivers and horns were close to JBL S3100, so I made a S3100 x-over and then fine tuned it to the 1400pro driver (the main difference to the S3100).
    Vernb
    Ok.
    Quote Originally Posted by vernb View Post
    Only thing that now puzzles me is that most of the "so called" JBL 16 ohm compression drivers I have, actually do not measure 16 ohm. My 2445 measure around 12 ohm and my newly arrived 2482 measure around 10 ohm. Even my 2426J measure around 12 ohm.
    I don't know much about building passive x-overs, but I thought that the impedance of the driver meant quite a lot to the x-over point. So that a 500hz x-over for 16 ohm drivers will actually not x-over at 500hz if the driver measures only 10 ohm. Am I right ?

    Vernb
    Right. I addressed this long ago. JBL used 10 ohms for the 077/2405 and 12 ohms for many of the compression drivers for rudimentary modelling purposes.

    You shouldn't just pick 500 Hz out of the air. You may want to exploit the natural roll-off of the horn/compression driver combination. It should be 12 dB/octave which means you'll only need a 12 dB/octave electrical filter to get the 24 dB/octave acoustic roll-off.

    Honestly, if you're just tossing darts blindfolded then you might be better off picking up a cheap active filter like a dbx 223 and start dialing frequencies until it sounds good enough to you. Or pick up one of those dbx DriveRack PA's and play the whole day away. I think they're like $450. I don't think you can even pick up SoundEasy and a good eight channel sound card for much less than that.

  15. #75
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    Quote Originally Posted by vernb View Post
    But my specific application and drivers is/are the same as Jervs and the same as JBL 4673, and since I have no measuring equipment, I will build Jervs x-over and work my way from there.
    I'm probably getting lost in concurrent discussions of three different systems here, but Jerv's system uses a different XO frequency, HF driver, and horn than 4673. Ultimately, you've got to start someplace, and I've documented at least a half-dozen trips down this path in these forums.

    I'm kinda with the member formerly known as Giskard on this stuff. It was fun the first couple of times, but, in the end, it's obvious nobody gives a flying whit....



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