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 it’s 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 I’m 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. I’m 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 025Ti’s 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 XO’s. I had hoped to feed the digital XO’s 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 XO’s or accept to feed a digital XO with analogue signal and accept the dual additional AD/DA conversions, I’m 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. I’m 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?
I’m not for a second imposing that a private individual like me with limited resources could copy the K2 concept with all its glory. I don’t 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 I’ve got.
I’m 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 XO’s 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.