JBL Master Reference Monitor

[Cappelen]

The baffle size and baffle diffraction affects the off-axis response in lower frequencies. The speaker is much taller than it is wide, so I guess it is natural that it is somewhat different.

If you talk about the average measurement I showed, this is simply a functionality built into the program Room EQ Wizard. I assume the formula is like you say. The sum divided by the number of measurements.

[natehansen66]

Hi natehansen66 and Cappelen,

I wonder why horizontal and vertical dispersion differ in the mentioned frequency region

Diffraction I would say like Cappelen says......though like I said I don't see how what they show is possible. Also, if they are rotating about a common axis (in this case I'll assume the horn throat but idk) then as you measure + vertical you're moving farther away from the woofer, and - vertical you're getting closer to it.

I haven't spent a lot of time measuring vertical response......+/-20deg is about as far as I go and then I'm moving the mic vertically and not keeping the distance constant to the speaker......like the arc it would make if the mic was tied to a string which was tied to the speaker. I'm not really sure the correct way to go about it but my first thought would be to rotate about the design axis like we do with horiz measurements.



I think these D2 drivers are interesting......does anyone know what the exit angle is? Also, are there any measurements of these on a wg other than the M2? I'm looking for some new cds and I just might make the jump to JBL

[Flaesh]

..does anyone know what the exit angle is?

Throat angle is negative.
But there is cone in throat.
That's how Faital (they added exit angle in driver's specs) describes the angle of similar exits:

Exit Angle* Combined Exit
*The driver's exit coincides with the end of the phase plug, there is no adaptation throat.

[Cappelen]

For some reason my REW measurement file from before was lacking some of the measurements I used in the listening window I showed earlier
Therefor I made a new set of measurements.

I was more careful about geting the angles right, so up and down looks more symmetrical and correct in the UHF.
On the negative side I had to leave the speaker where I listen to it, I couldn't move it to the middle of the room as I normally do (GF home). This made especially the -10 deg vertical a bit noisy do to reflections from a nearby sofa.

I split the measurements, because it's really hard to read all at once when they are as tight as this.

First, the horizontal measurements 0 - 10 - 20 - 30.



Nex vertical responses.


Finally, the average of the 6 measurements compared to the on-axis one. On axis is the green one.



Again, this are gated indoor measurements, don't try to read too much detail out of them. There is no smoothing applied.

Regards, Fredrik

[pos]

Thanks

Looking at your measurements, it looks like most of the "waves" you get down low are from reflections and not from the horn itself, as these vary from one position to another.

[Cappelen]

You could be rigth... I really need to get them outside.

But it can also be a diffraction effect. There is a dip on-axis in JBL's on axis mesurement aswell @ 2kHz.

But most likely room reflections leaking through like you say.

[natehansen66]

Throat angle is negative.
But there is cone in throat.
That's how Faital (they added exit angle in driver's specs) describes the angle of similar exits:

So would it be considered a throatless design? Do you know the negative angle?

[ivica]

So would it be considered a throatless design? Do you know the negative angle?

Hi natehansen66,

If can be trusted from the patent drawing, then it is about -10 to -11 deg.
regards
ivica

[SMT]

sub'd

[srm51555]

Has anyone figured out the best way to mount the wave guides to the enclosure?

There are 10 holes on the back that can be threaded, but then you need access form the back.

How is it done in the M2?

Good question because when I was performing a mock up of the horn on a piece of scape wood I realized the 10 baffle mounting holes are not flush with the rest of the horn. I'm on the fence with either drilling a hole all the way through or making a countersunk hole 10mm down and finishing the rest off with an M6. Either way the horn needs to have a gasket on the inside and the outside of the mounting holes. Is everyone still going with an M6 or 1/4" and how far down.

Thanks,
Scott

[SMT]

Long time looker, first time poster... Please forgive my elementary question, what is the useful range of the D2/M2 waveguide combo, looks to be 7-800hz?(AND ABOVE) Perhaps the question to ask is where does the waveguide loose directivity?

Thanks,
Shane

[ivica]

Good question because when I was performing a mock up of the horn on a piece of scape wood I realized the 10 baffle mounting holes are not flush with the rest of the horn. I'm on the fence with either drilling a hole all the way through or making a countersunk hole 10mm down and finishing the rest off with an M6. Either way the horn needs to have a gasket on the inside and the outside of the mounting holes. Is everyone still going with an M6 or 1/4" and how far down.

Thanks,
Scott

Hi srm51555,

Look at the:

http://www.audioheritage.org/vbullet...1&d=1442093038
http://www.audioheritage.org/vbullet...2&d=1442093060

I think that would be the best answer, knowing that about 700Hz i crossover (sharp , I think 48db/oct)

regards
ivica

[ds23man]

From very reliable sources I have been informed that the D2430 driver is produced by BMS.......

[ivica]

From very reliable sources I have been informed that the D2430 driver is produced by BMS.......

Hi ds23man,
Interesting info, especially if BMS4599 driver is in the consideration (yes it is mid-frequency, but may be some phase-plug and diaphragm change....)

regard
ivica

[JeffW]

Strange that the JBL driver has "Made in Mexico" stamped on the foilcal. BMS has plants in Mexico?