JBL M2 Reference Master Monitor Review

[Absolute]

Here's some measurements of 18Sound 4015 Beryllium compression driver on the M2 waveguide;

Raw response without EQ, measured relatively near-field from several angles and averaged. Ungated in a reflective room, so wiggles are reflections;

After EQ, taken from 70 cm distance (laser-measured) to center driver at angles from roughly 0-45 degrees - gated but don't recall resolution;

More interesting for most is the distortion measurements. Taken at 1m distance at 96 dB with Umik-1. Awfully loud in a living room.
4015 BE only - L/R 36 dB @ 600 hz;

Same measurement, but distortion normalized;

The distortion is where the differences become really apparent. I'll look and see if I can find similar measurements of the D2 2430k. If my memory serves me correctly I think there's close to -20 dB less distortion between 1-2 kHz with the large format driver. It was really noticeable how much more effortless and snappy the large format driver sounded when I swapped, but I could have imagined some of it due to buyers decease.

 

[sebackman]

Hi all,

I have had the fortune to test a large number of drivers and horns over the years. There are of course many very good combinations with new being added all the time, but its just about time and money "find" to the perfect combination. Some experience and knowledge also comes into play...

Disregarding the fact that you need access to the actual units it is very time consuming to measure FR response on and off axis, distortion and horn load on large number of driver/horn combinations.

Regarding JBL large format drivers on the newer JBL wave guides (VTX, M2 & 4367) , all designed for the JBL D2, I think it is just cheer luck that they are such a perfect match. There are so many parameter that comes into play but the phasing plug seem to be the perfect design and distance to the wave guide throat turns out to be more or less optimal. Some other drivers do need a spacer to work reasonable.

If we disregard potential sonic views the large format JBL drivers on these new wave guides, they objectively measure better than most other driver/horn combos that I have had the chance to sample. Later drivers (incl 243X), even large format as 2453, does not show equally good coupling between driver and these horns. 2447, 2450SL, 2351, 476XX are just great on these waveguides.

Using coated SL diaphragms also contributes to the very pleasant combination. The coating (Aquaplas) reduces the ringing common in metallic diaphragms over 2-3k. Ti and sometimes Alu can be perceived a little harsh and give some "listening fatigue" even if EQ'd correct.

I also have JBL large format Be drivers here (now on M2 wave guides) and albeit one can potentially hear a very slight difference on a good day the fact that they "fall off" quicker requires more intervention in the filter to push them up 20k. JBL solved this in the K2S's by adding a small tweeter driver/horn, 045, and so did I. I do prefer that combo compared to push the Be's, even if its a fully active DSP setup. Just sounds more at ease.

With that comes the drawback that a 3-way system is much more difficult to get right. Given that this sport is all about compromises, I almost always prefer 2-way systems over higher order . The plain SL diaphragms in combo with a good DSP gets the large format drivers to 20k without any problems. Nice.

Having shelved out the money for BE drivers myself, I would say that IMHO it is not worth the potential improvement over SL's. And a 2-way is significantly easier to bring to success.

When you get to this level of sonic performance these speakers are not just drivers in a cabinet with some electrical stuff attached, they are integrated system where every piece contributes. Having built many full DIY systems over the years I have, as many others, come to the conclusion that it is to complicated to build from scratch. Now we typically find very successful speaker systems and tweak them with proven alterations that could have come from the factory but mat have been omitted for cost or marketing reasons. Hence building clones on 4367 but adding the large format drivers drivers from the K2S series, which would have brought factory 4367 out of their intended price bracket. Adding active setup inspired from the M2's also adds proven technology that could not fit in the price/customer bracket targeted for 4367. If these indeed are improvement or just alterations is in the eye (ear) of the beholder.

Regarding the wave guides in M2 vs 4367, the the M2 is more difficult to integrate in a residential settings due to its (almost) 90x100 dispersion. That gives lots of floor and ceiling bounces in a normal home. This is less critical in a controlled studio environment. I had a difficult time to get my M2's to work in my room. The 4367 fair much better in my room. My 4367's are the same setup as member Beatelund, with large format driver and full active DSP setup ala M2.

The 4367 wave guide is wider and hence load the driver deeper. I would say that the 4367 provides an additional usable low end of about 100-150Hz, compared to the M2. That extra range may be easier to exploit with the large diaphragm 4" drivers that can be used down to about 500Hz (in 1,5" exit drivers) on a sufficiently large horn.

I think the reason that we like the active DSP 4367/large format horn/driver combo is probably due to that we could lower the XO +100Hz (as member Beatelund pointed out) in the very sensitive mid range where there is a lot of voice and instrument energy is. Moving that that range from the woofer to the driver changes the sonic composition quite dramatic. At least we like it.

Much about little

If someone would be interested in measuring data, for private use only, just give me a shout

Rock-on

//Rob (aka "sebackman")

 

[JoshK]

Thanks for the information Rob!

Some member here might not know but I have a long history of DIY and being in various forums. I used to tinker with building tube amp, more for fun than dogma, and horn speakers. I just like large format speakers. 6 1/2" two way speakers are ok, but never did it for me. I am not good enough with prose to describe.

The best 6.5" speakers I owned with the Modula MTMs designed on a DIY forum by an EE type. I've owned my fair share of all of the above, but the JBL M2s got me out of the merry-go-round for a decade.

Are the M2s perfect? God no. No speaker is, but they are better than everything else I've had the pleasure to hear including some multi-million dollar systems (I was a cofounder of a hifi club in NYC with some well to do friends). Given the incurred damage, and the DIY spirit I still have, it caused me to want to consider seeing what tradeoffs were made for reasons we are no privvy to. I had read all of Greg Timber's words before, including more than was quoted here.

 

[srm51555]

As promised from LHF and Greg Timbers

"Congratulations to those who have received their 4367's. There are a ton of misconceptions regarding the speakers. i can comment through the DV run after which I was no longer involved. The speaker is essentially similar to a 4365 in overall sound performance. There are some voicing differences partially due to my desires and partially as a result of the hardware used. The 2216Nd has the low TCR wire and is very kicky and dynamic as a result. The 2430 needs to be used an octave below where it is happy (as in the M2) and has an increased amount of 2nd harmonic distortion between 750 Hz and 1500 Hz as a result. It is not horrible, but it is about 10 dB higher than the 476Mg in that range and up to 20 dB higher than the 476Be over the same octave. The increased second comes from the 2430 being a ring radiator with no suspension. It is just difficult for it to move below 1500 Hz. The Mg diaphragm is twice as thick as the Be diaphragm so it resists motion in that range to a degree. The Be has the most freedom to move in the octave at and above crossover so it is the best of the three in that regard. With that said, the 2430 has a very detailed and musical sound and is a fine driver. It is capable of much higher output levels than any of the 476 family and is therefore well suited to Sound Reinforcement and Studio use. There is no silver bullet. With good things come bad things and one has to look at the total set of compromises. The 2430 is also about 1/3 the cost of the 476 precious metal drivers."

JBL 4367 first listen - Page 6

Just got them in today. The large packing containers insinuate the speakers are much bigger than they really are. They are easy to un-box and one person can do it although two is better. The multi-lingual owners manual is about 3/8's of an inch thick although only about 4-6 pages of it are...

www.audioheritage.org

and a few posts down

JBL 4367 first listen - Page 6

Just got them in today. The large packing containers insinuate the speakers are much bigger than they really are. They are easy to un-box and one person can do it although two is better. The multi-lingual owners manual is about 3/8's of an inch thick although only about 4-6 pages of it are...

www.audioheritage.org

Thanks,
Scott

 

[Pearljam5000]

It has a huge 15 inch woofer
Would a speaker with a smaller woofer + subs give similar or better sound?

 

[thewas]

It has a huge 15 inch woofer
Would a speaker with a smaller woofer + subs give similar or better sound?

Like I have written several times everything is a compromise so there is no total or absolute better or worse but everything depends on the application and personal priorities. For example such a large woofer and baffle controls the directivity quite down lower than a smaller one, unless you start making cardioid designs with multiple woofers or radiators.

 

[Duke]

It has a huge 15 inch woofer
Would a speaker with a smaller woofer + subs give similar or better sound?

It depends on the specifics. Imo that woofer's size is a "feature" and not a "bug", and it was designed to go up high enough well enough for that two-way application. It's a somewhat exceptional 15" woofer in that respect, but hardly unique, as there are other 15" woofers which work well in a two-way. (The M2's woofer combines this with unusually good bottom-end extension for a prosound-style 15" woofer, and that particular combination of attributes may well be unique.)

For example such a large woofer and baffle controls the directivity quite down lower than a smaller one, unless you start making cardioid designs with multiple woofers or radiators.

Imo a wide baffle and a good big woofer definitely have merit.

Erin's measurements indicate that the slightly-wider-baffle JBL 4367 has better low-end pattern control than the cardioid (actually sub-cardioid if I understand correctly) Dutch & Dutch 8C. I would expect the M2 to also surpass the 8C in this respect, though by a smaller margin. Video cued up to where he makes the comparison:

 

[thewas]

Erin's measurements indicate that the slightly-wider-baffle JBL 4367 has better low-end pattern control than the cardioid (actually sub-cardioid if I understand correctly) Dutch & Dutch 8C. I would expect the M2 to also surpass the 8C in the respect, though by a slighly smaller margin.

Yes, it should be added though that the 8C is only per design for various reasons cardioid only in the upper bass while there exist also cardioids who keep that pattern also lower.

 

[Duke]

Yes, it should be added though that the 8C is only per design for various reasons cardioid only in the upper bass while there exist also cardioids who keep that pattern also lower.

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. [EDIT: Apparently I was mistaken about the 4367 measuring better - see this post by @Martijn Mensink.]

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. [EDIT: Again I was mistaken; evidently a passive cardioid can have directivity as good as an active cardioid; see this post by @Martijn Mensink.]

 

[JoshK]

It has a huge 15 inch woofer
Would a speaker with a smaller woofer + subs give similar or better sound?

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).

 

[jtwrace]

I would expect the M2 to also surpass the 8C in this respect, though by a smaller margin. Video cued up to where he makes the comparison:

I've heard the 8c and obviously own the M2; there is no comparison between the two. Very few people have heard the M2's properly setup.

 

[JoshK]

Before I bought my M2s, I went to a Blu-Ray mastering studio here in Toronto that mixed supposedly 60+ % of all the Blu-Rays for North America in the last decade. It was all M2s up front (not sure the rest because I was listening stereo). They gave me an hour to play what I wanted in their home theater like room. I am pretty sure those were setup properly. I am not sure if I ever achieved that myself, but I am always working on it.

I was also honored to be invited to Dr. Geddes' home and heard both his "HT" like room and his living room setups with the 15" versions of his speakers, I forget the name. I genuinely enjoyed the experience. Got to talk math, audio and eventually wrote back and forth about a math problem.

 

[Pearljam5000]

Like I have written several times everything is a compromise so there is no total or absolute better or worse but everything depends on the application and personal priorities. For example such a large woofer and baffle controls the directivity quite down lower than a smaller one, unless you start making cardioid designs with multiple woofers or radiators.

I asked because in this video Alon Wolf said every speaker benefits from having subs(Including the $375,000 Magico M7) because it mitigates room modes.

 

[GXAlan]

Alon Wolf said every speaker benefits from having subs(Including the $375,000 Magico M7) because it mitigates room modes.

Not if you have a big enough room

(Which I would think the Magico M7 owner would be able to do).

 

[kma100]

I've heard the 8c and obviously own the M2; there is no comparison between the two. Very few people have heard the M2's properly setup.

In what way? M2 better? If so, then what is driving that? Low distortion or something else?

 

[thewas]

I asked because in this video Alon Wolf said every speaker benefits from having subs(Including the $375,000 Magico M7) because it mitigates room modes.

Yes, that is in contract one advantage of several subwoofers, but the other one I mentioned is conflicted in that case.

 

[thewas]

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.

Do you remember the reasons why a passive one can only be a subcardioid?

 

[Duke]

Do you remember the reasons why a passive one can only be a subcardioid?

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

 

[srrxr71]

I've heard the 8c and obviously own the M2; there is no comparison between the two. Very few people have heard the M2's properly setup.

Does the Harman experience center in LA have a pair set up?

 

[JoshK]

Duke provided one of the best solutions at a reasonable price back in the day. Dr. Geddes created a solution to follow for below the Schroeder frequency and it was all about multiple subs in strategic locations. It is all about using the other subs to fill in room modes for your first and main one.