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Thread: Crossovers for K2S9800 and/or S1M, tweeter over 1,5"driver

  1. #1
    Member sebackman's Avatar
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    Crossovers for K2S9800 and/or S1M, tweeter over 1,5"driver

    Dear all,

    I would need some help with input on filter design and if possible a copy of the layout of the filters in the new K2S9800 and/or the S1M.

    -Or if any of you experienced members would have any other example or ideas that you would be kind to share. All ideas are kindly appreciated

    I'm building a Hifi/HT system based on the ideas in the JBL Synthesis One system. The system is going to be a three-way in the front (left/centre/right) and a two-way for the rear speakers. All in all its going to be five cabinets + 2 subs.

    Two subwoofers will support the system below 50Hz, mostly for cinema use. One limitation is that the system (except the subs) will have to be wall mounted, which kind of dictates the shape of the cabinets.

    In each cabinet Im going to use two 8 woofers in parallel in a vented 40-litre box. The drivers are 8 ohms and the have a very flat curve to about 1,5k. The sensitivity is 87db and with two drivers, the system should have about 93-94db overall. The drivers are latest generation Alu cone drivers from Norwegian SEAS. The distortion below 1kHz is very low and the sound is very detailed. Im aware of the break-ups in the Alu cone above 3kHz so the LP filters will have to be at least 24db slope. I originally planned to use the 8 JBL driver in the LRS-28, but never found out a way to cope with the 1ohm load.

    Above that I will use a 2451J 1,5 driver with a 2332 (from DMS-1) horn and in the 3 front speakers I will also use the 025Ti tweeter to fill in from about 12kHz (from TI10K).

    The 025Tis are from the Audax factory in France and has a sensitivity of about 94db and stretches out to over 20kHz. Should work fine since they sound good in the TIK.

    This is a test box for measuring and listening. Ugly, but works.



    -Pretty much a stolen idea from K2S9800, to put a tweeter above the 1,5 driver. It will be a challenge since few if any other JBL has this feature. Even the DMS-1 was just a two-way construction.

    My initial idea was to run the whole system active and use digital XOs. I had hoped to feed the digital XOs with 24/96 digital SPDIF signal directly from a normal HT pre-amp. To my surprise it turned out that there are virtually no home theatre pre-amps with 5.1/7.1 digital outs in the market. The exception is Meridian and they have a proprietary signal out that can only be interpreted by their own components. They are also very expensive. If anybody has a good alternative, please post.

    So, unless I would use analogue XOs or accept to feed a digital XO with analogue signal and accept the dual additional AD/DA conversions, Im back to conventional stuff with passive crossovers. Hence this kind request for help.

    I did buy a Behringer DCX2496 digital XO to play around with, and have spent some time trying to set it up for a four way active play like this:

    *Subwoofer < 50Hz

    *Woofers < 1kHz, 24db/ slope, Butterworth curve

    *2451/2332 > 1kHz, 24db slope, Butterworth curve with CD horn compensation 6db slope from 3kHz < 12kHz 12db slope, Butterworth

    *Ti025 >12kHz, 12db slope, Butterworth.

    It all works quite good but I do need to play around with it some more to get the last bit right. Im using a MLS based system for measuring and even under my rather simple setup it seems to work reasonable.

    Now, since I know how much effort JBL put into the new K2S9800 series, which sound fabulous to my ears, and also know much time they have spent to add a tweeter above the driver/horn, I would really like to know how they did that. Can anybody please help me finding out how these filters look like?

    Im not for a second imposing that a private individual like me with limited resources could copy the K2 concept with all its glory. I dont even have access to the same drivers, but since the new K2 is near my ideal sound I would like to get as close as possible with what Ive got.

    Im also reasonable aware of the complexity of building speakers with several drivers. My last construction was a large four-way system with 2234H, 2118J, 2426J/2344 and a 2404H on top. It had passive XOs and sounded pretty good to me. As they were large I decided to sell them about a year ago, to go for something smaller. They are now in a recording studio as main monitors, so at least something was right about them.



    I understand that my drivers are different then the K2/S1M and those they have different electrical needs. But if I could find out how the S9800 filter were done, I could use the topology and plug it into my simulator and, together with the MLS curves for my actual drivers, see if I could tweak it to suit my setup.

    Without even the topology to start with it will be very complicated, as the filter also must incorporate the CD horn equalisation. Other input to this topic I also very appreciated.

    Also of great interest would be how the crossovers in the Synthesis S1M looks like. Those speaker uses dual 2118 to a 2416, and a 046Ti on top. Even though the compression driver is only a 1, the concept is similar with a tweeter above the drive.

    Does anyone here have other experience with putting a tweeter above a 1,5 driver with a CD horn it would be much appreciated.

    Kind regards

    //Robert

    Email:
    backman@ebox.tninet.se

  2. #2
    Member sebackman's Avatar
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    Question

    Nobody with experience of putting a tweeter (075&077&Dolly or Ti) over a 1,5" or 2" driver in a three-way system?

    Best regards

    //Robert
    Last edited by sebackman; 02-11-2004 at 11:34 AM.

  3. #3
    Administrator Robh3606's Avatar
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    Hello Robert

    Nice speakers! I have never really tried what you are doing but I have some thoughts. Figure any of the 434X monitors had the ring radiators above a horn so what's the difference?? Path lengths in both are comporable, phase will be an issue.

    When you did the 2344/2404 combo how did you do it?? Did you detune the compensation for the 2344 to give you a rolled off high end?? You could possible do that with the 2332 but I am not familiar and don't know how much compensation there is up top.

    If I remember right the tweeters are used in music mode and are switched in and out so they don't work when the horns are up in cinema mode. I could be wrong here.

    Rob

  4. #4
    Member sebackman's Avatar
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    Dear Rob

    Thank you for the input.

    You are right about the S1M, they do turn off the tweeter (045Ti) with Cinema sound. The topology could be of interest anyway, since I do believe they are 18db slopes.

    My old system only had 12db slopes because all the drivers had so wide operating ranges and no real disturbing anomalies. I also seem to remember that there is a difference (correct me if Im wrong here) in the compensation needed for the 2426/2344 (which is a Bi-Radial horn) and the 2451/2332 (which is a Constant Directivity CD horn). Furthermore the old system had a cross over to the horn at 1.8k, which kind of simplified the equalisation, as it according to my measurements (MLSSA) could go all the way.

    With the new combo I want a cross over at about 1k and the driver/horn only needs the CD compensation from 3.2k so the equalizer curve will have to have a knee at 3.2k. Level before and then 6db/octave gain upwards.

    I guess that I what they do that in the K2 filter which made that filter topology very interesting. I also need to go at least 18db to reduce cone break up noise from the woofers (Alu cones), which also is a challenge. I do believe that the K2 filters are 24db slopes, which is even better.

    As for cross over in the old system I only used a 12db HP at 1.8k and a 12db LP at 12k followed by a resonance circuit with a resonance frequency of 15k that was constructed as a fixed attenuator with a L+R+C circuit in parallel with the series resistor. Simple, but worked both on the MLSSA and to my ears. This one will be more complicated.

    Phase was an issue and I never got it quite right, but since the drivers all ran in their sweet spots it was not perceived as a big problem when listening. Normally you can get I little listening tired after a while if the phases are completely wrong. Not in this case.

    Phase will be an issue with the new system but I am a OTM (one-task-man) so I will try to get the SPL curve straight before fiddling with the phase and pulse response.

    More input, experiences and ideas are always appreciated.

    Best regards and thanks

    //Robert

  5. #5
    Member sebackman's Avatar
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    Hello all,

    I did get some info regarding the S1M&S3M. Thank you.

    This community is a brilliant source for JBL information.

    Is there realy nobody else with experience of putting a tweeter on top of a JBL CD hor/driver combo?

    All input appreciated.

    Thanks

    //Robert

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    It seems that in the S1M the horn is turned OFF when playing music. So basicly the horn is used for cinema and the dome is used for music. Hence they have apparently havent dealt with the integration issues of the two drivers.

    Interesting thread though!.

    cheers
    andreas

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    Senior Member herve M's Avatar
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    I have S1M schematic.
    Herv

  8. #8
    Member sebackman's Avatar
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    Hi Andreaspaulsen and herve M,

    Thank you for the info.

    It's feels like a little waste not to use the driver along with the tweeter in the S1M. I had hopped they did, and that was also my interest in the model.

    I will try to use a tweeter on top of my 2451/2332. Ideas welcome.

    Herve, thanks for the offer I have received a copy from a forum member a few days ago.

    I will probably try to get some ideas from the new K2 series.

    I feel a little uncertain what tweeter to use right now. My original thought was to use the Ti10K tweeter 025Ti. But when I put into my MLS rig the SPL is very uneven with two clear dips at 8k and 15k.

    Maybe a 2404 would be the cure...

    Best regards and thanks

    //Robert

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