M2 passive network for CD

[Jakob]

Hi,
I'm searching for the layout of the passive network for the compression driver in the M2. I saw a picture on the forum somewhere but due to the resolution i couldn't read any values on the components. Thanks in advance!

[Odd]

Hi,
I'm searching for the layout of the passive network for the compression driver in the M2. I saw a picture on the forum somewhere but due to the resolution i couldn't read any values on the components. Thanks in advance!


M2 manual

[Jakob]

Great, thanks for the help!

[audiomagnate]

I'm sure you already know this, but it's not really a passive crossover network, it's just a (compound) blocking cap to protect the D2430K from accidental destruction, and a pair of resistors to pad it down so residual amp noise can't be heard from the listening position under no-signal conditions.

[Jakob]

Yes, i've been playing around for fun with my bss unit and speakers imitating the m2 and just out of curiousity wanted to know how big cap they put in. It seems JBL chose almost the same as me :). By the way, I get really enjoyable results with the 6dB high pass at 750 or so Hertz. Digital cross overs and eq is great fun!

[audiomagnate]

Yes, i've been playing around for fun with my bss unit and speakers imitating the m2 and just out of curiousity wanted to know how big cap they put in. It seems JBL chose almost the same as me :). By the way, I get really enjoyable results with the 6dB high pass at 750 or so Hertz. Digital cross overs and eq is great fun!

With that crossover frequency and gentle slope you're dumping MUCH more mid frequency energy into your driver than goes into a D2.

[Jakob]

Ok, please explain why. If I remember correctly the d2's highpass is a 6dB butterworth set at 782 Hz. What have i missed?

[Ruediger]

Ok, please explain why. If I remember correctly the d2's highpass is a 6dB butterworth set at 782 Hz. What have i missed?

This irritates me, for several reasons. Where is that statement from?

Ruediger

[pos]

This comes from the DSP preset:
https://docs.google.com/document/d/1bzJyui75ZG_-wjV95dqKSbFs1Xh87bk2qlc-qS7Kk_Y/edit?usp=sharing&rm=demo

The protection networks adds another 6dB/oct high pass filter around 200Hz, and of course the closed volume inside the compression driver also adds is own 12dB/oct high pass.

[Jakob]

Ok, i'm sorry if I'm offending anyone, that has never been my intention
To clarify; i'm not trying to replicate or clone the m2 but reading about it made me want to experiment with my bss. I'm just having fun, thats all. There is much more to the m2 splendor than a 6 dB filter.

[Ruediger]

No worries, the technical aspects irritated me. I expected a real filter such as Linkwitz, and voila: you can have it. The 6 dB Butterworth is just a partial filter.

Rüdiger

[4313B]

I expected a real filter such as Linkwitz, and voila: you can have it. The 6 dB Butterworth is just a partial filter.The system does have a real filter, acoustic filter coupled with electrical filter. No need to add a bunch of extra poles in the mix and thoroughly jack up the superb system response. In short, the designers have an outstanding handle on world class filter design.


This comes from the DSP preset:

https://docs.google.com/document/d/1bzJyui75ZG_-wjV95dqKSbFs1Xh87bk2qlc-qS7Kk_Y/edit?usp=sharing&rm=demoOutstanding! :)

[pos]

I stumble upon this nos four years old thread, and I think it is important to correct some errors for reference reasons :)
It is now known that the schematic of the passive network from the M2 tech manual is false: c1 should read 3.3uF instead of 33.3uF, resulting in a combine c1+c2 value of 8uF, and a first order filter at 1kHz (instead of 209Hz with the original wrong values, quite a difference...)
And of course you can simply replace c1 and c2 with a single 8uF cap.

http://www.audioheritage.org/vbulletin/showthread.php?33972-JBL-Master-Reference-Monitor&p=383264&viewfull=1#post383264
http://www.audioheritage.org/vbulletin/showthread.php?33972-JBL-Master-Reference-Monitor&p=383277&viewfull=1#post383277