I've not heard an assemble pair of Summas, just your OS 15 profile waveguide baffle with the venerable DE250 CD and variable HP filters via electronic crossover. This was tried with several 12-15" drivers of which I became extremely fond of the JBL 2206.........15's lack suitable midrange clarity for me subjectively speaking.
FYI.....the waveguide was turned from a layered cake of MDF on a Bethlehem lathe salvaged from the scrapyard back in the early eighties. I've since parted ways with it as CNC is readily available at a friend's fabrication shop for pizza and beer.
......and no need to damp that guide, it was hard enough to lift!
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Mayhem - for good reason I get a little disturbed when people claim to have heard a Summa, when I know that is highly unlikely. One guy in the EU claimed to have heard them, but there are none in the EU. I do not accept that it is a Summa unless I made it and tested it to perform as a Summa. It is simply unfair to claim otherwise.
I agree with Bill that the M2 horn is likely so chaotic that the HOMs are simply inaudible. That may be fine, time will tell. I also noted that virtually nothing theoretical has ever been published about this device, the patent says very little. I also have never seen a highly accurate display of its performance in order to judge if the chaotic nature is a problem or not. The minimal published performance looks good, but nothing that a nice boring waveguide doesn't do. I suspect that patentability and uniqueness was more the goal than performance.
I agree with Bill that the M2 horn is likely so chaotic that the HOMs are simply inaudible. That may be fine, time will tell. I also noted that virtually nothing theoretical has ever been published about this device, the patent says very little. I also have never seen a highly accurate display of its performance in order to judge if the chaotic nature is a problem or not. The minimal published performance looks good, but nothing that a nice boring waveguide doesn't do. I suspect that patentability and uniqueness was more the goal than performance.
Isn't the target of a 120deg pattern one of the driving forces behind the design of the M2 wg? I've never built or modeled a wg with that wide of a pattern, but I would think an OSwg with that wide of a spread might lose significant output in the top octaves. I noticed a difference going from 60 to 90deg, but they were different designs really. With diffraction they can spread the beam at hf without losing as much output. I also agree that it gives them something unique for their flagship monitor.....unique being better or not idk, never heard them.
Obviously you must feel that 90deg is optimal, Earl, but is there any detriment to the performance of the wg going narrower....say 60deg? Also, while I'm at it, how wide can an OSwg be done effectively? I have no desire to go any wider than 90, but theoretically what would be the limit?
Obviously you must feel that 90deg is optimal, Earl, but is there any detriment to the performance of the wg going narrower....say 60deg? Also, while I'm at it, how wide can an OSwg be done effectively? I have no desire to go any wider than 90, but theoretically what would be the limit?
Yes, I do believe that 90 is optimal, and yes 120 degrees would be pushing an OS to its limits.
There is little to no disadvantage of going to 60 degrees except that it gets pretty long in order to get a decent mouth area for good control down to a lower frequency. Then matching this with a woofer becomes almost impossible.
There is little to no disadvantage of going to 60 degrees except that it gets pretty long in order to get a decent mouth area for good control down to a lower frequency. Then matching this with a woofer becomes almost impossible.
Unfortunately, a patent with partial (or no) disclosure undermines the patent.
Trade secrecy and patents are exactly opposite: the first requires signing Non-Disclosure Agreements (NDA's) all around, and the second requires sufficient disclosure that a "person skilled in the art" can make a working copy. You don't get to split the difference and claim trade secrecy and patent protection at the same time.
Lynn,
It just seems if the patent attorney is good enough at patent speak they can make something of nothing these days and get a patent issued. It seems fairly straightforward that they are using a form of pressure wave thinking in that JBL horn. I wouldn't say it would sound good or bad, haven't heard one, but a compete polar plot would be interesting.
It just seems if the patent attorney is good enough at patent speak they can make something of nothing these days and get a patent issued. It seems fairly straightforward that they are using a form of pressure wave thinking in that JBL horn. I wouldn't say it would sound good or bad, haven't heard one, but a compete polar plot would be interesting.
Yes ...
.. according to Sprinkle, needed for matching the radiation pattern of the woofer in the c/o overlap region centered at 800 Hz. See Mix article for the actual quotation and more. WHG
The Making of a Monitor: An Inside Look at How JBL Developed the M2 and Re-ignited Its Studio Line | Mixonline
.. according to Sprinkle, needed for matching the radiation pattern of the woofer in the c/o overlap region centered at 800 Hz. See Mix article for the actual quotation and more. WHG
The Making of a Monitor: An Inside Look at How JBL Developed the M2 and Re-ignited Its Studio Line | Mixonline
Never the less that is exactly what has been accomplished. If the geometry is blindly followed you will get to a horn, but where in the patent does it tell you the details of how and why it works. BTW non-disclosure agreements are signed long before patents are issued. At least in my case that was the facts of the matter. WHG
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At the time I heard the M2 which is prior to the NAMM demo, there was little to no info available,.,.......just an invitation to 'check em out' one on one for before the show. My experience with them was purely subjective I was blown away primarily by the cohesive nature of the device which overall the speaker behaved like a very dynamic point source......or in other words a really special bookshelf two way with balls too big to carry!
'The second thing we did was use a blending geometry—there are no straight lines, you’ll notice—that has a generally decreasing radius,” he continues, “forming an infinite number of reflections, and the net effect is that it smears the reflections coming back down the horn and negates them. “The third thing we did is bring these ‘knuckles,’ which is a name that sort of stuck, in from the side so that rather than having this 1.5-inch aperture that we had in the Bi-Radial design, we were able to get the upper pattern control frequency up near 10k, much like it would be with a 25mm dome. You combine that with a high-frequency device that has the internal damping characteristics this driver has, and it sounds like a silk-dome!'
Straight from the team at JBL that designed it. Seems like you are right, Earl. They think the HOMs would be quite inaudible at the listening position, because they are creating so many low-level reflections. Do you think that such a concession is a compromise? It seemed as if they were willing to sacrifice some things to get their desired pattern.
Yes, interesting to see Harman's arrival at 120 degrees as their aim. Unusual and I've not seen their sophisticated listening tests actually compare what angle (and by extension, what proportion of direct and reflected sound) is subjectively preferable. I recall either Toole or Olive's work saying that the reflected sound is equally important in their opinion to subjective preference, so that probably informed their decision to go 120.
Quip,
My question is if homs are truly the issue they are made out to be or are they totally overblown in reality and aren't the major problem with most basic horn shapes. How much can you weight them against the actual horn materials acoustic properties and the sonic signature of the drivers attached. I still don't buy the conversation that all compression drivers are interchangeable, each has its own sonic signature.
My question is if homs are truly the issue they are made out to be or are they totally overblown in reality and aren't the major problem with most basic horn shapes. How much can you weight them against the actual horn materials acoustic properties and the sonic signature of the drivers attached. I still don't buy the conversation that all compression drivers are interchangeable, each has its own sonic signature.
I think they are an issue. For one thing, every horn controls the dispersion pattern and that is singularly the most important (but not the only) factor affecting our perception of sound.
The way I see it is that Earl is quite correct in that distortion of compression drivers is imperceptibly low in typical domestic listening conditions. The polar FR would be dominated by the boosts imparted by loading in the horn and its shape, rather than the intrinsic FR of the compression driver (which is of course a measurement that is quite moot). I can see why they would sound the same under blind conditions unless the FR deviations are truly egregious.
Back to my original question: are there further consequences with the JBL approach of introducing many, many potentially inaudible HOMs? Anything that can be construed as sonically deletrious, even if the HOMs themselves can't be discerned?
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For the masses, 120 offers a wider area of coverage for multiple listeners in the room. But for myself, I prefer the single listener dominant position for hearing what a producer might have heard with his/her near-field monitoring/mixing. Even with classical music recording, I would rather hear the recording halls sound and not my room sound. So, it is a more narrow dispersion for accuracy to the original recording.
It seems that the issue of flat power response becomes more and more important as the dispersion of the system becomes broader. On the recording side... near-field flat on axis response monitoring/mixing will sound dull if the playback listening is in far field and is not flat in its power response with wide dispersion speakers.
So if the norm is to make (mix) recordings with flat on axis and near field, then we should do same in playback or if listening further away to those recordings, then greater directionality and CD speakers for flat power response are required. [EQ the on axis flat if needed).
90 degrees seems best over-all for critical listening and accuracy.
Thx-RNMarsh
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ICW (M2) FR (Audio Heritage)
Post #731, #733 & #735 from the referenced thread show some frequency response details. There a probably more. I am still reading the thread. WHG
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Thread (at Posts)
JBL Master Reference Monitor - Page 49
Post #731, #733 & #735 from the referenced thread show some frequency response details. There a probably more. I am still reading the thread. WHG
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JBL Master Reference Monitor - Page 49
Directivity measurements of the JBL M2 can be found here. When scaled to +/-90° it looks like this:
This doesn't look that good. The directivity between woofer and tweeter is not well fit and beyond 10 kHz there is strong beaming. Neumann and Genelec does it better.
On the other side maximum SPL is very high below 1 kHz.
This doesn't look that good. The directivity between woofer and tweeter is not well fit and beyond 10 kHz there is strong beaming. Neumann and Genelec does it better.
On the other side maximum SPL is very high below 1 kHz.
Attachments
Directivity measurements of the JBL M2 can be found here. When scaled to +/-90° it looks like this:
This doesn't look that good. The directivity between woofer and tweeter is not well fit and beyond 10 kHz there is strong beaming. Neumann and Genelec does it better.
On the other side maximum SPL is very high below 1 kHz.
Your linked image fails to show the frequency scale......where they measured relatively even directivity all the way down to below 400hz which is quite an accomplishment of these measurements are accurate.
..........but more important seems to be the critical assumptions as to what makes a speaker sound good or bad based solely on objective data. We all know the room plays a critical roll in the overall performance and in the case of directivity in relation to the reverberant field, listening position and placement all bets are off if there's no consistency. I used the term ' relatively' to describe the M2's directivity measurements for just that reason........with all things being equal......which they NEVER are, this is pretty solid performance. Besides this, all the objective data and measurements in the world of the M2 can't convince me that what I heard was anything less than spectacular so at some point, we have to let our ears play their subjective role in the design and evaluation phase. A chef tastes his creations before serving and rightfully so if his palate is trained.
Plasticine softens considerably with hand warming.
It can be quite squishy, or very hard, or anywhere in between. Very temperature dependent.
I'm pretty sure the damping characteristics will be very different.
Will the volatiles in the plasticine change over time?
Is there a more consistent material, that is not so temperature dependent?
Is mortite better?
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Directivity measurements of the JBL M2 can be found here. When scaled to +/-90° it looks like this:
This doesn't look that good. The directivity between woofer and tweeter is not well fit and beyond 10 kHz there is strong beaming. Neumann and Genelec does it better.
On the other side maximum SPL is very high below 1 kHz.
How was the plot captured? Has it been DSP'd to flat on-axis and then normalized to the on-axis response? If so, that is terrible performance. Nothing a SEOS can't do better.