Project M2 DIY Thread

[SMT]

Marketing Propaganda fwiw:

M2 ENCLOSURE
Small Footprint, Extended Bass Performance, Patented Low Frequency Port Design

Extended low frequency performance and high SPL can be the formula for unwanted resonance. The M2 enclosure is constructed of rigid 1" MDF and with the aid of JBL’s interferometer, extensively braced for rock-solid stability at the system’s full rated power. The enclosure incorporates a JBL patented Slipstream port design with internal flares that ensure low frequency efficiency while eliminating noise caused by port turbulence. Architecturally elegant, the M2 enclosure occupies a relatively small footprint, and can be transported to various working environments.

http://www.jblpro.com/www/jbl-story/...t#.Vmixz7-TVx4

[SMT]

Sadly, this is the most technical info. I was able to dig up. I was not able to find the pending patent docs...

https://www.youtube.com/watch?v=sIc2ORiDxrE

[Fitero]

Thanks for the responses.

Since this is a proprietary design for JBL, they won't sell the ports either. No matter, it is still a venturi, and can be easily copied by enterprising DIY people.

All we need is for someone to take a snap-gauge and caliper and measure the smallest part of the port, and the o.d. of the inner port bell and we can do the rest.
Valentin has already kindly measured the length, which more or less coincide to the data on the M2 tech sheet provided by 4313b.

[grumpy]

Or buy whatever flared ports you like and tune to length appropriately

[johnlcnm]

Since the JBL Master Reference Monitor thread is so massive I'm staring a thread that I and others can document our M2 DIY process if the. Here are some links that I was able to reference. Thank you for all of your contributions that made my and others project happen.

Schematic of the M2 - Note: C2 in the schematic shows a value of 33.3uf, this is a typo. the correct value is 3.3uf

DSP File

Inside the M2

Outside the M2

M2 Dimensions

Horn Mounting

Horn Mounting pt2

Scott,

I believe that the input coupling cap in front of the horn driver pad should be 33.3 uF plus the 4.7 uF. That along with the forward looking equivalent resistance of 7.1 Ohm, (into the pad/driver), would fall into the ball park with about a seven Ohm impedance. This would certainly become a part of the high pass network.

Regards,

John

[srm51555]

Scott,

I believe that the input coupling cap in front of the horn driver pad should be 33.3 uF plus the 4.7 uF. That along with the forward looking equivalent resistance of 7.1 Ohm, (into the pad/driver), would fall into the ball park with about a seven Ohm impedance. This would certainly become a part of the high pass network.

Regards,

John

Hi John,

I wish that was the case before I purchased the caps to charge couple the network. Barry confirmed the 3.3uf value here.

Thanks,
Scott

[hlaari]

Nice view

it will be nice to visit you in the summer, then you will be finish with the new M2 enclosure
I promise to take some interesting parts with me



Ari

[ggetzoff]

Any mounting adapters out there. I would really like a pair!

Cheers,

Greg

[ivica]

Since the JBL Master Reference Monitor thread is so massive I'm staring a thread that I and others can document our M2 DIY process if the. Here are some links that I was able to reference. Thank you for all of your contributions that made my and others project happen.

Schematic of the M2 - Note: C2 in the schematic shows a value of 33.3uf, this is a typo. the correct value is 3.3uf

DSP File

Inside the M2

Outside the M2

M2 Dimensions

Horn Mounting

Horn Mounting pt2

Hi srm51555,

Thank You for all information

Ivica

[baldrick]

According to rumours JBL have stopped selling M2 parts without valid M2 serial, so there's a chance they will not be avilable very much longer

[globulegl]

What is the difference between d2430h and d2430k. Lower frequency response for the 2430k?

[srm51555]

So I finally had time to try out the 2450SL-be's on my build and feel they are better suited for my needs. The D2430K's sounded very nice in a bigger room my house, but this room is doing kid duty for the next 18 years and I was never quite able to get the EQ'ing correct on them in my smaller listening room. Also I don't really need the spl capabilities of the D2430K's.Having a $1200 set of diaphragms sitting around doing nothing also played into it.


I'm now to the point of my audio journey where I feel like I have reached the peak of sound vs affordability and have no clue what to do with my audio need but here are some of my thoughts:

1) Sell all unused equipment, Wish I did this before my Mcintosh mc2155 went on the fritz this week. Sending it in for repairs this week hopefully. I'll keep this amp after complete rebuild and hopefully it will last another 10 years.
2) Purchase another set of woofers and be diaphragms for backups.

I also have some thoughts about using the extra set 2216nd's as under 100hz fillers. Although I don't think it needs it but it could be fun to play around with.

My lightly used D2430K's will be for sale if anyone is interested, shoot over a PM.

Thanks,
Scott

[hsosdrum]

I'm now to the point of my audio journey where I feel like I have reached the peak of sound vs affordability and have no clue what to do with my audio need ...

Just sit back and enjoy the music.

[pos]

Hello Scott,

How would you describe the difference between the D2 and 4" Be ?
How did you EQ them? Did you look for an identical response curve between the two?

I also have some thoughts about using the extra set 2216nd's as under 100hz fillers. Although I don't think it needs it but it could be fun to play around with.

This could help with room modes, at least.
Integrating a helper woofer in the M2 design is pretty straightforward if using an identical volume/tuning (~280L total!):

1. change the LF shelving to -2dB instead of -8dB
2. increase the Q/slope of that shelving a bit (IIRC in rephase I had to go from 0.6 to just under 1.0 when doing the simulation)
3. lower gain by 6dB
4. duplicate these LF settings for the helper woofer
5. add a 1st order low pass at 95.5Hz for that helper woofer ( 135Hz/sqrt(2) )

Steps 4 and 5 could probably be replaced by a line-level passive 1st order filter in front of the amplifier for the helper woofer, in order to save a DSP channel (unless you are using crown amps with integrated DSPs that is...)

[srm51555]

Just sit back and enjoy the music.

This is the toughest part, I really enjoy both the music and the equipment side of it.

Hello Scott,

How would you describe the difference between the D2 and 4" Be ?
How did you EQ them? Did you look for an identical response curve between the two?


This could help with room modes, at least.
Integrating a helper woofer in the M2 design is pretty straightforward if using an identical volume/tuning (~280L total!):

1. change the LF shelving to -2dB instead of -8dB
2. increase the Q/slope of that shelving a bit (IIRC in rephase I had to go from 0.6 to just under 1.0 when doing the simulation)
3. lower gain by 6dB
4. duplicate these LF settings for the helper woofer
5. add a 1st order low pass at 95.5Hz for that helper woofer ( 135Hz/sqrt(2) )

Steps 4 and 5 could probably be replaced by a line-level passive 1st order filter in front of the amplifier for the helper woofer, in order to save a DSP channel (unless you are using crown amps with integrated DSPs that is...)

Thanks for the integration notes, I like having the idea of having the extra woofers in a separate box for easier room placement. I'm sure when I get them we will talk further.

As for the difference between the two drivers, I felt the stock M2 is more of a studio tool than speaker. It sounded beautiful on Classical and Jazz music and I also felt it was comparable to the 435al in a friends 1400 array. It was two different rooms and different types of amplification, but they were more similar than different to me. I like the sound of the 4" JBL. It basically beat out everything else I have owned since Widget recommend the 2440 4 years back. Results between the original Sl's vs Be's were not huge, but noticeable. Right now I have a crude EQ and I think it is not too far off still from the original. I need to drag them outside and take some measurements, but that won't happen for a couple of months due to summer family life.

Thanks,
Scott