JBL M2 Reference Master Monitor Review

[napilopez]

We agree.

Assuming it's speaker sample consistency, then it becomes pretty pointless to choose between models based on one measuring closer-to-ideal than the other, beyond a certain point. And, based on the M2 differences we are observing, that 'certain point' is pretty rough, really.

You're right, but I don't really think it's manufacturer consistency exactly, perhaps I should have rephrased. After all, we saw earlier in this thread both the left and right units measured identically in the bass.

Instead I think the most likely explanation is that for whatever reason the official spinorama made during the development phase is not 100 percent reflective of the products people are getting. I wouldn't be totally surprised if the spinorama was made during near-final development of the speaker, but some slight thing was tweaked near or after shipping. We also saw a similar thing happen with Buchardt when they slightly changed the crossover of the S400 and and the official measurements were not reflective of the changes (they've since updated those measurements).

So the mystery remains but I see no reason to believe anything is amiss with Erin's measurements. It is ultimately an EQ problem as you say, but why the EQ is wrong is the real question.

Without getting at least one or two more decent measurements of the M2, it'll be hard to tell. A single quasi anechoic measurement would be enough to tell. Heck, not even that -- I just need a nearfield woofer and port measurement to see if the same issues are present as with my earlier nearfield sum of the speaker being tested.

 

[Pearljam5000]

Would be interesting to know how the 1238A compares to M2 since it also has a 15 inch woofer but it's a 3-way(and costs less)

 

[Absolute]

Perhaps the difference between the JBL M2 data and Erin's data can be explained by differences in the dsp versions used.
After comparing near-field measurements of the Crown cdi M2 settings and manually entering the same values into the Hypex Dlcp dsp, there's a difference in how the dsp's interprets the shelf filter in the bass.

We don't know what dsp JBL used during that demonstration graph or if Erin had the same dsp version.

 

[Absolute]

Would be interesting to know how the 1238A compares to M2 since it also has a 15 inch woofer but it's a 3-way(and costs less)

Will sound completely different as it's not a constant directivity design.
Based on measurements from Genelec this thing looks to be less refined than other speakers they have. At least it's ugly!

It's nearly half a meter shorter than the M2, so let's call it a standmount speaker. Some might even call it a toy

 

[Norway]

I wonder which compression driver needs a boost at 5k to10k? Thats where they usually enjoy to play?

Well it’s not a real CD in the way a TAD 3001, Altec 288 or JBL 475 at all! It’s more like a ring-radiator and not at all happy below 1500 hz but for the output very effective over 10 k Hz. Trying to match up with a 15” is the weak point of the M2 and 4367 that really needs to have a 500 hz crossover point. The M2 is more a measuring exercise than audiophile speaker imo and I have had both M2 and 4367 in my living room.

 

[tomtoo]

Well it’s not a real CD in the way a TAD 3001, Altec 288 or JBL 475 at all! It’s more like a ring-radiator and not at all happy below 1500 hz but for the output very effective over 10 k Hz. Trying to match up with a 15” is the weak point of the M2 and 4367 that really needs to have a 500 hz crossover point. The M2 is more a measuring exercise than audiophile speaker imo and I have had both M2 and 4367 in my living room.

Ah, thx for the info!

 

[807Recordings]

Well it’s not a real CD in the way a TAD 3001, Altec 288 or JBL 475 at all! It’s more like a ring-radiator and not at all happy below 1500 hz but for the output very effective over 10 k Hz. Trying to match up with a 15” is the weak point of the M2 and 4367 that really needs to have a 500 hz crossover point. The M2 is more a measuring exercise than audiophile speaker imo and I have had both M2 and 4367 in my living room.

You are not correct in saying this is not a compression driver. It is and the driving mechanism being ring driven does not change this from being any less true. If the driver is placed into something like a horn/waveguide to create compression then it should be a compression driver.

The D2 driver is a dual coil compression driver with a lot more excursion unlike the others you have mentioned. From my understanding this creates larger power handling, higher SPL, and lower X over point.

Do correct me if this is incorrect with specifics.

 

[Bugal1998]

Well it’s not a real CD in the way a TAD 3001, Altec 288 or JBL 475 at all! It’s more like a ring-radiator and not at all happy below 1500 hz but for the output very effective over 10 k Hz. Trying to match up with a 15” is the weak point of the M2 and 4367 that really needs to have a 500 hz crossover point.

There seems to be some silliness here.

Of course the D2 is a 'real' compression driver; putting the driver in a space that allows compression and better impedance matching with the atmosphere is what makes it a compression driver (which the D2 clearly does)... being a ring, dome, or heck parrallelogram radiator has absolutely nothing to do with it.

At 96db the D2 in the M2 has less distortion from 1-2k than it does above 5k, with decreasing distortion from ~1600hz down to the ~800hz crissover point. Just look at Erin's 96 db distortion plots. While I agree the directivity could have benefited slightly from a larger waveguide and lower crossover, the facts simply don't backup your statement about weakness due to distortion. Might other drivers have lower distortion in this range? Sure. But calling this a weakness of the D2 implemenation in the M2 is, again, silly.

"The M2 is more a measuring exercise than an audiophile speaker"

I have no idea what that statement even means.

 

[Tom C]

“The M2 is more a measuring exercise than an audiophile speaker"

Maybe it means it measures better than it sounds, or measures well but doesn’t sound that great. If so, that’d be the first I’ve heard of it.

 

[Bartl007]

Just out of curiosity, anyone have insight on the D2 compression driver and 2nd harmonic distortion that appears to limit peak spl capabilities above 1kHz.

Is this audible at higher Spl in a home theater setting? (Typically listening from ~4m)

(Full disclosure: I own these speakers and think they sound fantastic, until I can afford Meyer sound blue horns, this "measurement exercise" will have to do)

 

[fluid]

If the driver is placed into something like a horn/waveguide to create compression then it should be a compression driver.

It is a compression driver because the diaphragm is larger than the exit. This is where the "compression" comes from.

 

[Bugal1998]

Just out of curiosity, anyone have insight on the D2 compression driver and 2nd harmonic distortion that appears to limit peak spl capabilities above 1kHz.

Is this audible at higher Spl in a home theater setting? (Typically listening from ~4m)

I've read different thoughts about 2nd order harmonic distortion audibility, some... or all... of which may not be true. But if I don't hear it, then it's not audible (to me).

Crossover points, EQ or other frequency shaping, and a host of implementation decisions could all come into play, but the VTX V25-ii lists the combined maximum output of the three D2 drives in the enclosure at 149.5 db. That's something like 450x the amount of acoustic output (did I calculate that right?!) compared to the 123db rating of the M2 (or about 150x the acoustic output per D2 driver in the VTX 25). I would imagine the VTX has a higher crossover point to the D2 than in the M2... And perhaps it's audibly distorting at that 149db output... but I remain, nonetheless, completely unconcerned about the D2 limiting the output in any way.

Yeah, the Meyer Sound Blue Horn looks like an intriguing speaker.

 

[Absolute]

Just out of curiosity, anyone have insight on the D2 compression driver and 2nd harmonic distortion that appears to limit peak spl capabilities above 1kHz.

Is this audible at higher Spl in a home theater setting? (Typically listening from ~4m)

(Full disclosure: I own these speakers and think they sound fantastic, until I can afford Meyer sound blue horns, this "measurement exercise" will have to do)

Compression drivers "always" have a fair bit of 2 harmonic distortion. Usually you also have elevated 2 harmonic distortion in horn-waveguides, so combined you'll often see higher 2nd harmonic than you might intuitively expect.

Don't mistake that for a lack of capacity, though. Those D2 drivers will happily destroy your hearing if you're not careful. Second harmonics usually won't bother us, so it still sounds clean at insane levels.

From experience I can tell you that it's the lower part of the operating range where the D2 shows a bit of strain at high volumes compared to larger format compression drivers. I compared distortion of D2 with 18sound 4015 Beryllium driver and there's about 15-18 dB less distortion in the 4015Be between 1500-1800 hz even with 4015Be crossed at 600 hz.

 

[briskly]

Just out of curiosity, anyone have insight on the D2 compression driver and 2nd harmonic distortion that appears to limit peak spl capabilities above 1kHz.

Is this audible at higher Spl in a home theater setting? (Typically listening from ~4m)

This is only the maximum output referenced to a nonlinear distortion threshold. The maximum output of the M2 horn goes far beyond that.

JBL D2430*, like most compression drivers in horns, has elevated 2nd order at HF from nonlinear acoustic propagation: consider the high pressure in the phase plug and the horn throat. It would be broadly inconsequential as far as hearing goes.
The LF behavior of the dual annulus is a bit weaker than other 1.4-inch exit drivers. Their combined membrane area is less than a typical 3-inch compression dome.

 

[Speaker-Inquisitor]

AFAIK the D2 driver was initially developed for Line Arrays with an x-over an octave higher. There its Output is at least equal to the large 4“ Dome drivers, while beeing smaller and i suspect cheaper to manufacture. Compared to my 2450SL Compression drivers, the D2 is a tiny thing.

 

[Absolute]

Here's the D2430k vs 18sound 4015BE for visual reference on the M2 horn.

While certainly bigger and heavier, when I changed them the most striking thing was actually the huge difference in magnetic pull. Any screws in the vicinity would suddenly find themselves glued to the 4015 and was a real pain to get off.
It would happen to D2 also, but was easy to pull off in comparison.

 

[Speaker-Inquisitor]

For comparison, 2450sl on the d2 mounting plate.

btw nice 18S driver. Maybe i‘m gonna get some be diaphragms in the future, but first i have to build the rest of the speaker for which the m2 waveguide was intended for.

 

[73hadd]

View attachment 150565View attachment 150566

Wow this is really helpful. I have some 2446 that I have not implemented yet because I am stuck searching for a DSP solution.

What is the 2nd graph?

As for the 2446, does anyone have some graphs comparing oem, Be (radian), Be(Materion), and a 2446 with 2450SL dia installed?

Edit: I didn't find the exact graphs I was looking for, but here is 2450H with 2450 vs. 2450SL:

2450 Dia - Page 4

Does a 2450 Titan Diaphragm also fit in a 2441 ?? Eckhard

www.audioheritage.org

Also, what would happen if someone used a 2446 (2"exit) on an M2 (1.5" exit) waveguide? Asking for a friend

 

[jmpsmash]

View attachment 186064
View attachment 186065

Here's the D2430k vs 18sound 4015BE for visual reference on the M2 horn.

While certainly bigger and heavier, when I changed them the most striking thing was actually the huge difference in magnetic pull. Any screws in the vicinity would suddenly find themselves glued to the 4015 and was a real pain to get off.
It would happen to D2 also, but was easy to pull off in comparison.

How does the 18Sound compare to the D2430K, for measurements and for sound?

 

[arn]

jbl m2 vs 705p

https://www.youtube.com/channel/UCuz54JZgDAWjJkwZZ2TeKKw/videos