Second Generation Jordan JX92S MLTL Designs

[Jim Griffin]

Over on the Audiocircle.com full range driver forum a thread has been generated the last few days that references a second generation version of the original Greg Monfort (GM) 48" and 31" Jordan JX92S MLTLs. Mark Dikovics of Jordan-usa.com has spent some time with Martin King's spread sheets and has generated new MLTL iterations which are 40", 35", and 31" long. The new models extend the low end 3 dB cutoff down to 30 Hz or below while reducing the harmonic related peaks and dips. Mark's work also takes into account the placement of the speaker in-room so that the driver position and port placement are iterated to achieve a flattened response. Again thanks to Martin King for the powerful spread sheet capability he has given us. Take a look at the discussion at:

New MLTL Designs for JX92S

I'm particularly impressed by the new 35" version which tunes below 30 Hz and out performs the older versions of these speakers. The new designs are detailed on the Jordan's US Distributor for JX92S and other Full Range Drivers site which has the enclosure drawings and such.

Mark also suggests that the new 35 " and 40" enclosures can be augmented with the Aurum Cantus G2si ribbon tweeters as I did in my 'Jordan with a Ribbon MLTL'. That thread is on the diyaudio site.

Thanks to Mark for his work and contributions. Good stuff worthy of duplication.

Jim

[northernsky]

Hi,

I built, as you call it, a first generation MLTL box; to go from 40 to 30Hz just with a new cabinet seems very attractive. Is there someone who already listened to the new boxes?

Renato

[peterpan]

I am a little confused. It says all dimensions are internal, so the 35" design will be more than 35" tall when complete, am I right?

[northernsky]

Yes, you are.

Renato

[R-Carpenter]

Dimensions are posted this way because builders will use anything from 3/4 to 1.5 inch MDF or plywood for the cabinet. There's a small increase to a baffle size but the diffraction changes are minuscule.

[jfs]

If using the Aurum Cantus G2si Ribbons with the 35" second generation design - due to the increase in baffle width over Jim Griffins MLTL with Ribbon design, would the crossover have to be modified to compensate for an increased baffle width of 1 1/2".?

Phew !!!! That was a long sentence, or was it two, just badly composed.?

[Jim Griffin]

jfs,
what I recommend on the baffle width for the second generation models is to use a 7.5" external cabinet width (the same as my Jordan with a Ribbon mini-monitor and MLTL). Adjust the cabinet depth to attain the same cross sectional area as given for the second generation models.

An example for the second generation 35" the internal dimensions are 7 x 9inches. If you are using 0.75" thick material for the construction, then the external dimensions would be 8.5 x 10.5". Now the crossover for the ribbon version will take care of baffle compensation (optimized for an external baffle width of 7.5") so we need to alter the external dimensions for the ribbon version. Thus reduce the width from 8.5 to 7.5" but increase the external depth to 11.5". That would attain the desired baffle width for the ribbon version while maintaining nearly the same internal cross sectional area.

Jim

[jfs]

Jim, you are indeed a star. Throughout my posts I seem to be thanking you constantly for your assistance, once again thank you.

Have a very Merry Christmas and a Happy New Year - you have made mine one to look forward to audiowise.

:

[Colin]

Hi Jim - What influenced the crossover point of your ribbon design, given that the JX92 goes to 20kHz. Is there a 'sweet point' at which it is advantageous to crossover? Would it have worked if you had allowed the JX92 to continue full range?

[Jim Griffin]

Colin,

From my early work with the JX92S run full range in a mini-monitor enclosure I observed that the off axis response (say 20-30 degrees off-axis and greater) of the Jordan driver really starts to beam beyond 3 kHz. Also the small Aurum Cantus G2si tweeter can be crossed over with a reasonable crossover slope in the upper 2 kHzs so a 3 kHz crossover was a natural target. The ribbon has wider off axis dispersion so the in-room power response is very pleasing when married to the JX92S. Essentially, the tweeter helps the speaker to maintain wide dispersion higher in frequency than just the JX92S only. You can hear the difference. I have my MLTL Jordan with a Ribbon MLTL tricked out so I can swap between the Jordan run full range with a baffle step circuit and the crossover with the ribbon tweeter. Bottom line: it is the off axis response that pleases me the most with this combo.

Jim