JBL M2 Reference Master Monitor Review

[JoshK]

I think you should bring the swarm back, @Duke. This crowd is a better crowd to learn some "science".

 

[Duke]

Ha! Thank you, @JoshK!

Actually the Swarm never went away. But the price did go up.

The Swarm Subwoofer System

www.audiokinesis.com

 

[Jaxjax]

What the above guys said, I am only going to add my $.02. Speaker and room interaction is a big deal and a larger speaker with pattern control objectives in mind has some advantages than more traditional bookshelf T+W speakers have in that regard. And then there is all the dynamics available with larger speakers, higher efficiency, lower compression that you get as well.

I like a bookshelf speaker, but the larger is another level if you can get away with it (WAF).

When I had a large dedicated room years ago with large pro jbl horns I I worried for myself a few times in there ....not so much with the little guys I run now

 

[thewas]

The impression I got from somewhere was that the damped-slot technique's path length for the backwave is not very precise so the cancellation is not optimal. For one thing the point where cancellation should be maximal for a true cardioid would be in the middle of the back panel of the enclosure, not on the sides where the slots usually end up.

I found this article quite helpful when I was starting to explore cardioids. The author is now the B&C distributor for the US:

https://bennettprescott.com/downloads/AdvancedSubwooferArraying.pdf

Interesting, on the other hand for example Geithain models seem to have the slots on their rear panel (although not in its middle but symmetrically around it

and show at their measurements a rear attenuation of approximately 8-10 dB which would be contradicting that theory?

Source of above: https://www.me-geithain.de/en/rl-901k2.html

Hope one day some Geithain, @sigbergaudio or other passive cardioid would be sent to a NFS for a full spin down to 20 Hz to validate such.

 

[Duke]

Interesting, on the other hand for example Geithain models seem to have the slots on their rear panel (although not in its middle but symmetrically around it

View attachment 431062
and show at their measurements a rear attenuation of approximately 8-10 dB which would be contradicting that theory?
View attachment 431061

Source of above: https://www.me-geithain.de/en/rl-901k2.html

Hope one day some Geithain, @sigbergaudio or other passive cardioid would be sent to a NFS for a full spin down to 20 Hz to validate such.

So it appears. I don't remember what my source was.

 

[sigbergaudio]

Interesting, on the other hand for example Geithain models seem to have the slots on their rear panel (although not in its middle but symmetrically around it

View attachment 431062
and show at their measurements a rear attenuation of approximately 8-10 dB which would be contradicting that theory?
View attachment 431061

Source of above: https://www.me-geithain.de/en/rl-901k2.html

Hope one day some Geithain, @sigbergaudio or other passive cardioid would be sent to a NFS for a full spin down to 20 Hz to validate such.

Not sure I grasped exactly what the question was / what we are uncertain about, but here is 0 and 180 on the Manta at least, if it helps enlighten something. These are measurements from 2023 so they're not necessarily a perfect representation of the on-axis response of today's production speakers, but give an impression of the cardioid effect, which I believe was the topic. Both graphs have 1/24 smoothing. This is anehoic, 2m distance.

 

[thewas]

Thank you for the plot which seems quite similar to the Geithain ones, the question was how large the total DI is below 100 Hz as Duke stated that "a true cardioid has a directivity index of 4.8 dB but a subcardioid has a directivity index of only 3.2 dB" and to answer that with safety I guess a full NFS spin could be helpful.

 

[Duke]

Thank you for the plot which seems quite similar to the Geithain ones, the question was how large the total DI is below 100 Hz as Duke stated that "a true cardioid has a directivity index of 4.8 dB but a subcardioid has a directivity index of only 3.2 dB" and to answer that with safety I guess a full NFS spin could be helpful.

I'm under the impression that a true cardioid would have a deep null at 180 degrees, but I could be mistaken. Maybe that deep null doesn't happen in the real world?

Please don't misunderstand me; -10 dB at 180 degrees is great in my opinion!

 

[sigbergaudio]

I'm under the impression that a true cardioid would have a deep null at 180 degrees, but I could be mistaken. Maybe that deep null doesn't happen in the real world?

I don't think you will realistically see a pattern similar to a cardioid microphone with no output (or input in the case of the microphone) at 180 degrees.

Manta is specced as follows based on some averages across the 120-180 degrees area from several measurements, it varies a bit from unit to unit and measurement to measurement, since I don't have a full Klippel NFS it's hard to make these types of measurements exact.

Cardioid dispersion characteristics (120-180°):
~100-500hz: 10-12dB attentuation
~500hz-1khz: 16-20dB attentuation
~1-5khz: 25dB attentuation


So it's quite a lot of attentuation further up (somewhat helped by a wide baffle as well) in frequency, that I find to have a positive effect too. It's not just about bass in my opinion.

 

[Duke]

I don't think you will realistically see a pattern similar to a cardioid microphone with no output (or input in the case of the microphone) at 180 degrees.

Manta is specced as follows based on some averages across the 120-180 degrees area from several measurements, it varies a bit from unit to unit and measurement to measurement, since I don't have a full Klippel NFS it's hard to make these types of measurements exact.

Cardioid dispersion characteristics (120-180°):
~100-500hz: 10-12dB attentuation
~500hz-1khz: 16-20dB attentuation
~1-5khz: 25dB attentuation


So it's quite a lot of attentuation further up (somewhat helped by a wide baffle as well) in frequency, that I find to have a positive effect too. It's not just about bass in my opinion.

North of 500 Hz that attenuation to the rear looks to me like it's pretty consistent with a 12" cone in a 14" wide box. But from 100 to 500 Hz, and especially towards the bottom end of that range, the attenuation to the rear you're getting is imo fantastic.

 

[sebackman]

Don't know if it helps but attached is some info on ports. I believe that some of these findings are used for the M2 ports.

 

[Martijn Mensink]

Yes, imo it's a brilliant design, and I was surprised to see that the old-school approach of big-baffle-plus-big-woofer actually measured better.

My understanding is that a passive cardioid - that is, one which uses slots in the enclosure rather than a dedicated cancellation woofer - ends up being a "subcardioid" in practice rather than a true cardioid. A true cardioid has a directivity index of 4.8 dB but a subcardioid has a directivity index of only 3.2 dB, if I recall correctly.

Hi Duke,

This is the directivity of the JBL 4367 you were talking about.



This is the 8c:




Based on Erin's measurements, the 8c has higher directivity in the 100–300 Hz range.

While designing a passive cardioid is more challenging than its active counterpart, a well-engineered passive cardioid can achieve the same directivity.

The 8c's are optimized to perform exceptionally well in a wide variety of rooms, delivering full-range output, constant directivity, and a very smooth response. They excel at normal and moderately elevated levels. However, if you need extreme dynamics and very high SPL, the 8c's fall short compared to the 4367 or the M2. Ultimately, it’s a case of using the right tool for the job, horses for courses.

 

[Duke]

Hi Duke,

This is the directivity of the JBL 4367 you were talking about.

View attachment 434129

This is the 8c:
View attachment 434136



Based on Erin's measurements, the 8c has higher directivity in the 100–300 Hz range.

While designing a passive cardioid is more challenging than its active counterpart, a well-engineered passive cardioid can achieve the same directivity.

The 8c's are optimized to perform exceptionally well in a wide variety of rooms, delivering full-range output, constant directivity, and a very smooth response. They excel at normal and moderately elevated levels. However, if you need extreme dynamics and very high SPL, the 8c's fall short compared to the 4367 or the M2. Ultimately, it’s a case of using the right tool for the job, horses for courses.

Hi Martijn,

Thank you for posting that, and I see what you mean! Not only the pattern control 100-300 Hz, but the sheer uniformity of the radiation pattern of the 8c across the spectrum is outstanding. I've edited my post, directing people to your post.

 

[Tom C]

Has anyone seen a contour plot for the M2?

 

[jtwrace]

Has anyone seen a contour plot for the M2?

Yes

 

[Tom C]

Yes

Please share.

 

[NTK]

Please share.

Aren't they in Erin's review www.erinsaudiocorner.com/loudspeakers/jbl_m2?

 

[Tom C]

Sorry. I looked, but didn’t see. Thank you.