Thanks for posting the pics of the M2 throat. For some reason I reckoned they were moulded in 4 parts with the joins along the diagonals. Seems not.
It would be fun to carve those from wood.
BTW you are not messing around here , some good engineering going on , nice.
Hi RoB,Originally Posted by sebackman
Interestingly that the response is almost flat, not as expected CD horn behavior.
regards
ivica
JBL 2451J Be on JBL M2. Pretty nice.
Kind regards
//RoB
The solution to the problem changes the problem.
-And always remember that all of your equipment was made by the lowest bidder
Some additional data
Test JBL M2 / 2451H Be 2015 04 03
Indoor workshop lower floor, upward on work bench.
LSPCad 60 (latest update), M-Audio Fast Track Pro, Samson Servo 200, Earthworks M30 (calibrated), 33mf in series,
2-Channel measurement, 48kHz, 512 buff, 65536 MLS, 1/24 smooth offset 64 cm, range 40db, window 4ms (OBS short window only high frequency usable), approx 86db SP level. No EQ or PEQ.
Kind regards
//RoB
The solution to the problem changes the problem.
-And always remember that all of your equipment was made by the lowest bidder
An impressions how the m2 waveguide sound compared to other horns?? Are the M2 waveguid really that good or is it more the DSP and D2 driver makes the difference in M2?
Kind of surprised to see the measurment with 2451 dropping so much downto the 800hz crossing point, I would expect the D2 driver to drop even more than 2451!?
Baldrick,
As you can read the the time window is very short, ie no usable data that low. I will post data from outdoor measurements later.
Kind regards
//RoB
The solution to the problem changes the problem.
-And always remember that all of your equipment was made by the lowest bidder
Sorry, didn't see that until now
It is a combination of all three working together. I do know that all the previous waveguides JBL had didn't do what they needed the M2 waveguide to do in this specific instance, so there's that.
Hi sebackman,
Using 4ms windows, I would expect that the frequencies under 500Hz, can be much influenced, but not 1.5kHz.
As I have said, before, I believe that the lower frequency "loading" of the M2 horn, as seems to me as "fast flaring wall type horn", is not so good as can be expected due to its large mouth format. Almost the same as OSWG type of horns.
For D2430K driver, may be that is not a problem, due to its membranes, but for the old JBL 4-inch dome type diaphragms with metal-made suspension, large diaphragm displacement (at lower frequency) can be fatal. (especially 2441AL, and 476Be). Here using Truextent Be, or Radian 4-inch diaphragm,
with a polymer suspension would be less sensitive.
Am I right, we would see one day when our honorable member 4313B, would make THD measurements of his 476Be with M2 horn.
regards
ivica
Are you taking into consideration just how loud these things are? Especially in a home environment? Are you guys using the recommended 6 to 10 dB resistor pad between the c.d. and the amp? Protection caps?
I agree that the polymer suspensions are less prone to fatigue but I don't think it is an issue here. Doug Button, Greg Timbers and I have talked about these suspensions and c.d. excursion.
I will confess my real concern - that foam in the back can... it turns to tar over time and, quite frankly, I'll be replacing that junk with felt as soon as I get around to it. The 476's are chock full of that stuff and it has to go.
The thought has never even occurred to me. I suppose if I was hearing a bunch of junk I might be inclined to investigate the cause but given that they are so insanely clean sounding I probably won't bother.
Hi 4313B,Are you taking into consideration just how loud these things are? Especially in a home environment? Are you guys using the recommended 6 to 10 dB resistor pad between the c.d. and the amp? Protection caps?
I agree that the polymer suspensions are less prone to fatigue but I don't think it is an issue here. Doug Button, Greg Timbers and I have talked about these suspensions and c.d. excursion.
................
The thought has never even occurred to me. I suppose if I was hearing a bunch of junk I might be inclined to investigate the cause but given that they are so insanely clean sounding I probably won't bother.
Have You tried 476Be with M2?
I am sure (if not yet) that one day You will inform us about that [476Be & M2], and after that some of us can decide whether or not to make DIY M2 ("inspired") horn, and what would be lower frequency that such 244x/5x combo with M2 that can be applied to them. I believe that something around 800Hz, using sharp (say 18~24dB/oct) filtering would be good protection for the driver suspension.
Neglecting the possible problems about LF loading of the driver, on-axis response shown here (almost FLAT up to 15kHz), push me to believe that such combo (244x/5x & M2) is not so wide dispersive as it has been said in some M2 presentations. I would expect a kind of CD-horn behavior (-6dB/oct roll-off, over say 3kHz), but here I can to see.
regards
ivica
No, not yet. Just on the older 100x100 and 90x40 waveguides.
Hi 4313B,
Can You show on 90x40 WG (may be PT-H95HF)
regards
ivica
Not anymore. The 476Be's are bolted to H4338 horns. I'll be bolting the 476Mg's to the M2 waveguides.
Hi,
Thank you for feedback on the 2206 vs other 12”. Not needing the lowest octave when running subs (SUB1500’s) it sounds like 2206 may be a good choice, even if 1200FE takes it one step further.
I normally mount an attenuator to reduce sensitivity 5-10db as suggested, at least on the drivers with more exotic diaphragms and I always mount a protection capacitor. I have no idea if it has any sonic effect but I have always used a large and a small capacitor in parallel, as in the M2.
When testing here I use a 33mf Audyn cap to protect the driver. Normally I also set the MLS sweep to start at maybe 4- 500Hz to reduce any strain on the dia. I agree that at normal listening levels at home it feels less likely that the suspension would harden and give up.
4313b, what kind of felt do you use to replace the foam. In one of my spare drivers the rot has started… Suggestions much appreciated.
I will do some measures outdoors next weekend and also some on and off axis and publish. I also have a pair of almost new 2450SL’s to test. -Later I will throw in the DSP settings in one of the BSS units to see what happens.
I also agree that other JBL driver/horns can probably be “DSP tuned” to deliver equally solid sonic results, or at least almost. But having toyed with DSP filters for quite a few years I know that getting good results with them goes beyond setting PEQ’s to flatten the curve.
My guess is that if the raw data curve from D2 on M2 waveguide would be given to a bunch of different people to equalize, their respective DSP settings would be different but the final measure may very well be rather similar. There is just way to many parameters to tweak and let alone combinations of them. In the newer DSP units there is virtually “no limit” to EQ/PEQ settings. The BSS units can do both IRR and FIR filters and even combinations of them.
The settings for M2 kindly posted by 4313b leads me to think that JBL has a computer algorithm to calculate several different combinations of EQ/PEQ/phase/delay with an acceptable final curve. Then they listen to each different combination to verify that a given combination of DSP settings indeed sounds good. That is why I think the M2 is getting so fantastic reviews. They have spent the time needed, they have the HW needed, they have a large anechoic chamber and they have the skills to find the right HW / DSP combination.
I think it will be difficult to privately find “the combination” to make other horn combination to sound equally good. If JBL at some point in time would to publish full DSP settings for K2 / 43XX horns that may well prove to be equally good or even better for home use.
This is also why I have chosen to limit myself to use the 2332 horn for a number of years. With my drivers (2451Be) they produce a nice curve that is easier to “straighten” than some of the other horns I have tested. Albeit that the other horns may very well sound significantly better with passive filters or other active settings I have not been able to get them to the same level as the 2332 with my DSP settings (to my ears). I do have pretty decent measuring equipment but it may very well be the lack of knowledge and/or experience preventing other horn/driver combinations to deliver their native superiority at my place.
The interesting thing from my point of view is that we do have the M2 DSP setup from which we can do tweaks to adjust for other woofers, other cabinets and potentially other drivers. That base is very important because we do know that the DSP settings with the original HW sound really good. We cannot expect to get to the level of M2 system quality, but I do think we can get acceptable close with that as a starting point. Without access to the DSP settings I would probably not have dared to take on this project, just too many unknowns. :-)
I know that Mr Timbers have posted some DSP suggestions for other JBL speakers and that may very well be equally good or better. For some people the original JBL speakers will always be the preferred sound, for some people adding DSP processing and/or other tweaks may make their clock tick. And then there are lunatics like me who attempts to create our own combinations and accepting that they are not JBL speakers but DYI bastards. Albeit good sounding bastards.
The real M2 real game changer to me is that JBL created a system where components and SW is integrated into one function, producing accurate sound.
More data will come soon.
Kind regards
//RoB
The solution to the problem changes the problem.
-And always remember that all of your equipment was made by the lowest bidder
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