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Thread: Large format HF drivers

  1. #1
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    Large format HF drivers

    OK, so I plan to build a pair of two-way systems that use 2225 and 2445 drivers (2-inch compression drivers).

    Are there any special considerations I need to ponder?

    I will run them in a 7sq ft box, and plan to passively cross these at 500hz.

  2. #2
    Obviously... not a golfer grumpy's Avatar
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    Are there any special considerations I need to ponder?
    how large a horn you can tolerate...

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    Administrator Robh3606's Avatar
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    Depending on the horn you may have a issue above 10K. Depends on what you are looking for. Why are you running 2225's in 7 cubic ft??

    Rob
    "I could be arguing in my spare time"

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    Quote Originally Posted by Robh3606 View Post
    Depending on the horn you may have a issue above 10K. Depends on what you are looking for. Why are you running 2225's in 7 cubic ft??

    Rob
    Good point, Rob.
    The VAS of the 2225 is 6 ft3.

    Ron

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  6. #6
    Senior Member vernb's Avatar
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    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.

    I thank you for these valuable informations. My search is now over and I will start building my second DIY project.

    Thanks again
    Vernb

  7. #7
    Senior Member vernb's Avatar
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    But I am still in doubt, because some people here on LH say that you need to compensate the falling HF response of the compression drivers in the x-overs. They do that in S3100 I know, but on the JBL 4673 the x-over doesn't have any kind of compensation. It is just a straight 12db/oktav filter, as I see it.

    Is that because the 2445 2" drivers do not roll of in HF like the smaller 2426 1" drivers ??? Are they more linear in their response?

    Vernb

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    constant directivity horns exhibit roll off


  9. #9
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    Quote Originally Posted by vernb View Post
    But I am still in doubt, because some people here on LH say that you need to compensate the falling HF response of the compression drivers in the x-overs. They do that in S3100 I know, but on the JBL 4673 the x-over doesn't have any kind of compensation. It is just a straight 12db/oktav filter, as I see it.

    Is that because the 2445 2" drivers do not roll of in HF like the smaller 2426 1" drivers ??? Are they more linear in their response?

    Vernb
    If you take a look at the 3160 crossover - attached - used in the 4670 series theater systems, you'll find a compensation switch, S1, that does this to compensate for the rolloff. It works quite well in my setup although the physical size of the crossover is a bit overkill for a residential system.

    To play around with the whole thing, though, I'm seriously considering just going with an electronic crossover as others have suggested. This gives me the freedom to dink around with crossover points and levels that hardwiring a dedicated crossover will not.

    If you think about the cost of replicating something like a 3160 you'll find you will have as much or more in a dedicated crossover than an electronic one, assuming you have the extra amps around already.

    Cheers,

    David
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  10. #10
    Senior Member vernb's Avatar
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    Quote Originally Posted by doodlebug View Post
    If you take a look at the 3160 crossover - attached - used in the 4670 series theater systems, you'll find a compensation switch, S1, that does this to compensate for the rolloff. It works quite well in my setup although the physical size of the crossover is a bit overkill for a residential system.

    To play around with the whole thing, though, I'm seriously considering just going with an electronic crossover as others have suggested.

    Cheers,

    David
    Hi David
    Thanks for pointing out the idea with the S1. I thought it as basically just a volume pot for the 2445 driver (the complete HF range).
    I hope that is the same thing with the 3115 x-over? The reason I'm asking is that I have exactly the 2225 and 2445 drivers (JBL 4673 components), so I would have an impedance problem with the 3160 x-over, I think....

    If you went active, you wouldn't have the S1 as a HF compensator. Wouldn't that be a problem?
    Vernb

  11. #11
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    Quote Originally Posted by vernb View Post
    Hi David
    Thanks for pointing out the idea with the S1. I thought it as basically just a volume pot for the 2445 driver (the complete HF range).
    I hope that is the same thing with the 3115 x-over? The reason I'm asking is that I have exactly the 2225 and 2445 drivers (JBL 4673 components), so I would have an impedance problem with the 3160 x-over, I think....

    If you went active, you wouldn't have the S1 as a HF compensator. Wouldn't that be a problem?
    Vernb
    I don't think the 3115 xover has a similar boost circuit built in. I believe it has a level control which, in the 316- is done as a series of jumpers.

    If - actually when - I go to an electronic xover there will be no need for the passive xover at all. I'll put it on the shelf for later.

    Note that the 3160 xover has a couple of other issues such as the 4 ohm woofer requirement and the 16 ohm horn requirement. If your drivers work then great but not all have that setup. They come up sometimes on auction sites.

    BTW, S1 is a reference to the switch in the 3160 schematic where you can switch in and out the boost circuit into the horn tweeter's path.

    Cheers,

    David

  12. #12
    RIP 2011 Zilch's Avatar
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    What crossover is used in 4673 I linked above?

    3115A has a three-position HF Boost switch and compensation circuitry:

    http://www.jblproservice.com/pdf/Net...%20Network.pdf

    Yah, the schematic in the system tech sheet is the older 3115 without that good stuff:

    http://www.jblproservice.com/pdf/Net...%20Network.pdf

    Many active crossovers have a CD Comp button to do similar.

    If you want to build 3115As yourself (with no tapped inductor), there may be an equivalent circuit posted in the forum somewhere.

    Link it here for the benefit of others if you find it, please.

    Otherwise, I presume y'all know who to ask to kindly post one....

  13. #13
    RIP 2011 Zilch's Avatar
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    Quote Originally Posted by Zilch View Post
    If you want to build 3115As yourself (with no tapped inductor), there may be an equivalent circuit posted in the forum somewhere.
    O.K., I put some effort into searching, and the only thing I found re: 31xx crossovers was this equivalent for 3110:

    http://audioheritage.org/vbulletin/s...84&postcount=3

    There are some clues there as to where to start, but he's subsequently also observed that a simple inductor swap (even if we know the DCR) plus L-pad does not produce a true autotransformer equivalent.

    Once a true equivalent IS generated, however, the same boost circuit might be usable with it, or an improved version developed.

    This "generic" approach is not generally favored, but a true LX5 (and LX5 plus HF boost) equivalent that anyone can build might be seen as having merit and deserving the requisite effort.

    If not, the options are clear: go active or find 3115As and recondition them....

    Footnote: I've never done much with large-format 2" drivers, but on the one occasion I ran 2450s on 2380A with 3110A (800 Hz) using HF boost, it sounded surprisingly good. Sorry, I did not measure the response, alas.

  14. #14
    Senior Member SMKSoundPro's Avatar
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    Boy howdy!

    I am sitting here watching the snow fall, and the small juvenile moose in our back yard paw at the ground for some chikweed...

    thinking about exactly this!

    I still think about building some 4507 boxes for the small dance floor using a 2225 or 2226 and a 2425/2370 combo. I know that this little two-way kit gets a lot of press here, and am really ready to start cutting plywood.

    I am lacking the 15's at the moment, though. I was thinking of 6 or 8 boxes to start. Fill them with components as I can. Use a two way active crossover with subs underneath.

    I just need to learn more.

    Scotty.
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  15. #15
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    Quote Originally Posted by SMKSoundPro View Post
    I am sitting here watching the snow fall, and the small juvenile moose in our back yard paw at the ground for some chikweed...
    It's a damn good thing Palin is out of the area at present or you'd be grinding up moose burgers about now... nice photos!

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