Hi All,
I am new to the forum. I joined as I look to construct some DIY M2's.
Firstly, a big thankyou to all members who have contributed to such an amazing resource of information.
I have been reading as much as I have time for, and I greatly appreciate the efforts of all who have documented and compile/tweaked settings etc.
I sent POS a private message with some questions regarding M2 crossover design.
I tried to post publicly, but I think my message and content exceeded maximum limits.
Anyway, I was hoping someone might have a link to a recreated cut sheet and design plan for the M2 cabinets.
I.e. CAD cut sheet etc. Does this exist?
It would be amazing to get these plans, linked on the crossover google link, including the 3D file for the port design etc.
Thanks for your assistance.
Many thanks
Hello,
I know that is years later.
As the discussion goes around the purpose of the resistors and capacitors.
I see it some thing like this:
1 the capacitors provide DC and low frequency protection well below the crossover frequency.
2 Padding to operate up in the amplifier power range where there is less noise.
3 with R2 in parallel with the driver and R1 in series with the driver the impedance curve is much flatter and tamer with much less resonance to disturb the frequency response.
Thought comments, agreements disagreement?
Thanks DT
If you Google M2 passive crossover there is a diagram with corrections of the capacitor mis print,
An explanation is given of the network.
Yes it provides attenuation of approximately 9 dB and a slow 1st order high pass passive filter at approximately 1000 hertz. This significantly improves the signal to noise ratio of a horn when used Bi amplified application.
There is no rocket science here and l doubt Jbl spent too much time thinking about it. Greg typically uses a -6 dB fixed pad when Bi amping a horn. Those Crown amps have massive output so the M2 pad is scaled accordingly. There’s nothing to it.
A horn without a pad will exhibit noise problems heard as residual hiss and other artifacts that erode the noise floor and resolution of the system. We don’t want that so we insert a fixed pad.
The network is there to back the warranty and mis use of the system in the event in of an amplifier malfunction. Scroll down this link to the diagram.
https://www.avsforum.com/threads/diy...2852530/page-4
Thanks for the replies with links.
I have an order in at Mouser for the 3.3uf + 4.7uf capacitors and resistors.
POS I did note in one of your links that you speak of the passive network linearizing the impedance of the D2+ waveguide.
I believe that will be true.
I will test that with wit the analyzer on my bench. (APx555 plus calibrated microphones.)
Thanks DT
M2 tested on a klippel test bench at Erin's audio corner:
https://www.erinsaudiocorner.com/loudspeakers/jbl_m2/
Excellent waveguide, 1-2 dB too hot tweeter and cabinet could and perhaps should be a little bit better resonance-wise. It's possible that some of those resonances could come from something being loose.
This measurement also confirms the peaking from 7-11 kHz even with the M2 version of D2 that can benefit from adjustments in the dsp.
The compression tests shows why a big ole speaker has its merits. Excellent stuff.
Very interesting, thanks for posting.
He confirmed the 270hz issue that we found awhile back ago.
Thanks,
Scott
🟢Hello Friend! I'm quite confused about which speaker to use in my project.
You commented on the 2216ndi, the original I believe is the 2265HPL, others say they can be replaced. Please help me.
If you recommend a speaker, please put a link to purchase. I'm not in the US, I'm in Brazil where we didn't find anything about it.
Thank you!
Edgewound...JBL Pro Authorized...since 1988
Upland Loudspeaker Service, Upland, CA
I would try to find a pair to listen too. I have a pair if Be CC 1400's and a CC M2 based passive system. IMHO are not the same as far as imaging and depth. The 1400 is a bit more forward than the M2 passive. They are not in the same room and I know that the M2 is using 1dB of attenuation on the waveguide SO??? I wouldn't dump a pair of 1400's and go grab a pair of M2's without a good listen and preferably doing it side by side. The 1400 is a damn fine speaker on it's own account.
Rob
"I could be arguing in my spare time"
The M2 being (intended to be) paired with the Crown amps using active crossovers, would be an apples-to-oranges comparison to the passive-crossover 1400.
I feel that the better comparison would be the consumer / Synthesis version of the M2: the 4367. Comparing the 4367 to the 1400 I feel that the 4367 is a more accurate speaker.
- Jeff
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