JBL M2 Build for a complete novice

[kelossus]

Close to kicking off a M2 build but am overwhelmed by the pages/threads of information. Hoping to kick this thread off by asking a few questions regarding the crossover and cabinet design. I will not be building the cabinets myself but out sourcing the job to a very skilled speaker builder in Oz.

I have forwarded himself a few pictures which show the dimensions of the cabinet and woofer/horn cut outs. Now that we are a few years removed from the initial build threads on LHF can anyone advise on "best in world" tips. Questions like port size, cabinet bracing and build material all come to mind.

Also the biggest challenge I can foresee is regards to the network. I would rather passive but I don't know if the 4367 network is a drop in replacement or does the M2 Cabinet need a bit of EQ from a DSP to function properly. I have a very limited knowledge when it comes to active crossovers/dsp and would like some guidance regarding this. I have an integrated tube amp which I could use as a power amp but how to integrate a amp to drive the woofer and EQ everything properly is beyond me? I don't have the ability to troubleshoot these kinds of things so I would need straightforward direction that is essentially plug and play. Or even better a charge coupled passive network if feasible or in existence?

Proof reading this post is only reinforcing the fact that a project like this may be beyond myself and require more experience to tune the speaker once built.

Any feedback will be greatly appreciated.

[johanwholst]

My tips is to go active! Its a steep learning curve but the advantages outweights the hassle. Regarding amps, a tube amp on d2430k and a powerful solid state makes sense. You can drop or modify the original network that is basically attenuation network to reduce hiss from the I-tech amp in addition to protection and a 1 order LP
I dont know your budget, but there is an OZ dsp/preamp on the marked now that looks like a dream product
A budget solution would be a minidsp.
All the eq settings are readily available

Build as close to the original as possible. Mdf is fine and the bracing is actually superb
Also try to make the curved baffle plate.

[kelossus]

My tips is to go active! Its a steep learning curve but the advantages outweights the hassle. Regarding amps, a tube amp on d2430k and a powerful solid state makes sense. You can drop or modify the original network that is basically attenuation network to reduce hiss from the I-tech amp in addition to protection and a 1 order LP
I dont know your budget, but there is an OZ dsp/preamp on the marked now that looks like a dream product
A budget solution would be a minidsp.
All the eq settings are readily available

Build as close to the original as possible. Mdf is fine and the bracing is actually superb
Also try to make the curved baffle plate.

Do you have the plans for the curved baffle? This kind of information is extremely important and I thank you for making me aware.

[kelossus]

Are you talking about the baffle plate that the ports sit in? Or is the front baffle itself curved?

[johanwholst]

Are you talking about the baffle plate that the ports sit in? Or is the front baffle itself curved?

Im talking about the baffle plate with the ports. I did not make it myself, and regret a little even I doubt it have a significant sonical impact. Maybe reduce diffraction?
I do not have the curvature, but if you shape it with the highest point equal to the height of the waveguide, you should be close to the original. Calculate the radius of the circle that gives you approx the height and baffle width (the chord). Good opportunity to brush your geometry skills!
https://planetcalc.com/1421/

[Ian Mackenzie]

An interesting article on port design and a calculator

BTW those DEQX dsp processors start at around US$2995
http://www.deqx.com/products/

[dprice]

Post # 405 in the Project M2 DIY Thread features a build constructed via CNC machining and 3D printing of the ports. If you could get a copy of the files it would be nearly trivial for a CNC shop to cut the cabinet parts for you including the curved lower baffle. Does your cabinet guy have CNC capabilities or work with someone that does? Same thing for having someone print the ports.

The "simple" crossover solution is to buy one of the BSS London processors that have the M2 presets pre-loaded (or can be downloaded from JBL). As mentioned above, miniDSP and others have have gear that will do essentially the same thing but require a little more effort on your part to program the EQ settings. I use a pair of the miniDSP openDRC-AN units as described here: https://www.minidsp.com/forum/opendrc-projects/10584-jbl-m2-crossover-with-the-opendrc?limitstart=0 I'm no expert but was able to follow the excellent directions provided by member POS. You might get acceptable results with a lower cost unit (miniDSP 2x4HD?) but I don't know if anyone has tested it.

Good luck with the project.

[hsosdrum]

The "simple" crossover solution is to buy one of the BSS London processors that have the M2 presets pre-loaded (or can be downloaded from JBL).

True that. If you build the speaker with a passive crossover, even if you get every other detail 100% correct you won't have an M2. If you want M2 performance (or even close to it) you must go active and use a BSS processor that has M2 presets or the recommended Crown amps that have built-in M2 presets. Those presets are part of the speaker; it's not an M2 without them.

If you go with a passive network you've elevated yourself into the position of speaker designer. And no matter how good at it you might be, you aren't as good at it as the guys who designed the M2. And you don't have access to their test and evaluation gear, which (besides tons of electronic gear and proprietary computer algorithms) includes 3 different anechoic chambers and at least 5 different listening rooms.