Any enclosure ideas for the "new" JX92S?

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tubesguy

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#1
Hi folks -

I just got a pair of the Jordans from the Brian group buy (thanks, Brian) and was thinking of the Jim Griffin designs, with G2Si.

It appears, however, that the measured T-S specs of the drivers doesn't match the specs on the Jordan site. Brian came up with some numbers on his own, and Zaph has come up with some different numbers on his site:

http://www.zaphaudio.com/blog.html

I ran these in WinISD last night, and came up with, as Zaph suggested would be the case, some pretty large enclosures for a vented box. I'm guessing that the MLTL design is also going to be significantly different, and that even a sealed box is going to be quite different with these driver specs.

I am a total neophyte with regard to box modelling, so this is a bit of a reality check with you folks who can do this in your sleep. Any recommended box sizes/alignments/configurations, especially those that dovetail, so to speak, with the new Parts Express box choices? I do plan to use a subwoofer for the bottom end, and can comfortably cross over in the 80-100hz range.

Thanks in advance for any help - Pat
 
#2
I implemented the Jim Griffin mini-monitor design using a .25 cu. ft. PE box. My drivers are most likely the "new" version. I received them in December and they have the white boxes as shown in the group build thread.

I have not felt they are lacking in bass considering the size of the enclosure. I have no way to perform any measurements, but at a recent audio meet everyone made comments to the effect of, "its hard to believe how much bass those speakers have".
 
#4
Hmm, well it looks like the pair that Zaph tested are very high quality drivers, based on the tests he did, but they are definitely different in regard to the T-S specs, especially Qts, than the specs on the Jordan site.

If there is a concern that there are quality problems within this run of drivers, I'd certainly be willing to run my pair, presumably randomly selected from the batch, up to Zaph to test them. (He's about two hours away from me.)

I'm really just looking for suggestions on how to implement these drivers, insofar as they differ from previous Jordans, and as those earlier enclosure designs thus depart from optimum. - Pat
 
#6
Bob Reimer said:
I have it on good authority that there may be some QC issues with the JX92S.
Click to expand...

Hi Bob. When you say quality control, do you mean in terms of parameter variation? Because although I trust Zaph's numbers much more than the ones I came up with, the 20 that I measured were all pretty close to each other.

Here's a comparison of the numbers I came up with using new out of box drivers versus what Zaph measured after breaking them in well for 8 hours. Another member said he would measure his pair using WT2 as well. I will remeasure the drivers when I get them back from Zaph to see how much the numbers change.

Code: 
    BWRX        Zaph
DCR 5.2 ohms    5.2 ohms
Fs  58.6107 Hz  53.070 Hz
Qms 1.0726      2.1890
Qes 0.3645      0.7826
Qts 0.2720      0.5765
Vas 10.2355 L   11.01 L
 
#8
According to Ted (I asked last week when Brian's results were up, so the authority is pretty good here too), there is no 'new' JX92S - it hasn't changed and quality control has never been an issue.

The spec differences may be due to different measurement methods. Try the established specs first for enclosure design.

Ted tends to go for a belt and braces method on measurement, using traditional methods to verify what the computer measurements are telling him (ditto on enclosure and crossover design), so I'd be inclined to trust his results.
 
#10
Colin said:
According to Ted (I asked last week when Brian's results were up, so the authority is pretty good here too), there is no 'new' JX92S - it hasn't changed and quality control has never been an issue.

The spec differences may be due to different measurement methods. Try the established specs first for enclosure design.

Ted tends to go for a belt and braces method on measurement, using traditional methods to verify what the computer measurements are telling him (ditto on enclosure and crossover design), so I'd be inclined to trust his results.
Click to expand...

Could the measurements reported be due to the fact that the drivers haven't been 'run-in' ?

That is, will they loosen up with use, which would tend to lower fs and Qt, probably closer to the spec values ?
 
#11
If you look up at post #6, you can see Brian's measurements out of the box, and Zaph's (apparently either belt _or_ suspenders technique ;-)) after whatever break-in he applied. Fs did go down, but Qts is higher.

Since I have a pair of Variovents from a prior stillborn project, I may use those in a .38 cu ft PE box, first without the ribbon, and then with. Thanks for the input, guys. - Pat
 
#14
While many will argue the nuances of T/S measurements, one measurement that is fairly straight forward is resistance. It seems that everyone who has measured this batch from the group buy is getting 5.2 ohms. Note that the manufactures spec says that Re is 4.5. This to me seems to imply that the voice coils have changed.

This is a big change in T/S and I suspect that just dropping them into those enclosures will result in less bass depth and perhaps a hump in the bass response.
 
#15
tubesguy said:

I know little enough, however, to still be baffled as to how the difference translates into differences in designs such as GM's MLTL, or optimum box size for the Griffin mini.
Click to expand...


In both the 31" and 48" MLTLs, Zaph's specs show a bit more mid-bass 'bloom' with the attendant faster roll off to Fp typical of mildly under-damped alignments, so in theory need to be closer to a wall or corner to protect them down low and any BSC may need to be reduced.

Then again, since I used published specs and don't recall seeing any measured ones before now, for all I know nothing's changed.

GM
 
#16
Colin said:
According to Ted (I asked last week when Brian's results were up, so the authority is pretty good here too), there is no 'new' JX92S - it hasn't changed and quality control has never been an issue.

The spec differences may be due to different measurement methods. Try the established specs first for enclosure design.

Ted tends to go for a belt and braces method on measurement, using traditional methods to verify what the computer measurements are telling him (ditto on enclosure and crossover design), so I'd be inclined to trust his results.
Click to expand...

Hi,

Given Zaphs test results have verfied by others, they agree with good
manafacturers specifications and that he used two seperate methods
to come up with near identical results your attitude is hard to fathom.


Yes, those really are the Thiele/Small parameters. I use the delta compliance method, which is far more accurate than the delta mass method. They are way off from the factory specs. I've also included the results from the Woofer Tester 3. It's an all-inclusive hardware solution to get woofer parameters. By all-inclusive, I effectively mean hard to screw up with a wiring error. The results are similar - a high Qts. I've posted both to show two completely different software packages coming to close agreement on specifications that are far, far off from the manufacturer's. Maybe that will help minimize the number of people saying "Gee, Zaph's T/S numbers are very different from Jordan's, whose do I beleive?"
Click to expand...

You can lead a horse to water ......

🙂/sreten.
 
#19
gmilitano said:
While many will argue the nuances of T/S measurements, one measurement that is fairly straight forward is resistance. It seems that everyone who has measured this batch from the group buy is getting 5.2 ohms. Note that the manufactures spec says that Re is 4.5. This to me seems to imply that the voice coils have changed.
Click to expand...
be aware that most common resitance meters will not acurately measure anymore in this range (allthough a difference this large may be significant), I know mine doesn't
 
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