JBL 2397 Curves

[Mr. Widget]

I recently bought an electro-acoustic measurement system called Clio. I still have a lot to learn about using it to do fancier measurements like THD, Polar Plots, etc., but I have been using it to do some basic frequency plots for the Project May effort and tonight I thought I'd give it a whirl on the popular JBL 2397 "Smith" horns.

Here is a plot of the JBL 2441 driver on the 2397 horn. The Blue plot is on axis and the Red plot is 30 degrees off axis. These plots have what is called 1/12th Octave smoothing. With smoothing it averages the response within the specified octave rate. The overall response is pretty flat (no speaker really measures flat at this resolution), and the 30 degree off axis response is surprisingly good. Realize that this horn is not really meant to be used below 800Hz.

Widget

[Mr. Widget]

Here is a comparison between the JBL 2397 and one of my Westlake clones. It is interesting how the the wider lips of the Westlake do seem to improve the lower response, but at a sacrifice at the top end. This explains why I always feel the need to EQ up a bit around 6-10KHz.

[Mr. Widget]

These plots are from the same measurements as above but with half octave smoothing. This is frequently the way we see response plots in catalogs as it looks better.

Widget

[Steve Gonzales]

Lovely piece of equipment there,Sir. Very interesting data too. With all due respect, I think you should be named Mr "Wizard". I've shown the drawings to some craftsmen I know and I'll be cookin' some test runs off those drawings you so kindly posted very soon. I love this new data because I really didn't know if there was truely a difference between the 2397's and the Westlake's . Can you plot spatially or is that a bad question? Also, when you say EQing, do you use an EQ in your main system (music). I have always got such a negative response when I tell friends that I use an EQ, but to my ears, when I use the EQ, the response is pleasing . I use both parametric and fixed band- subtlely . I am curious to know if you do too and to what extent, notch filter, full fixed band or parametric?

[Alex Lancaster]

That´s neat Widget!; Do You plan to compare the 2311/08 combo sometime?.

[paragon]

This is measured 12 years ago by "Audio-Technik" (Lowther Dist.) with a prof.
measure system.

[Mr. Widget]

That´s neat Widget!; Do You plan to compare the 2311/08 combo sometime?.

I don't currently have one or any 1" drivers. If someone brings one by, I'd be curious to check it out with this objective measurement gear. Subjectively, I prefer the 2397/2441. A while back I had both and did AB comparisons and to my ears there was no competition. I suppose THD measurements comparing the big 2" 2441 vs. the 1" driver should be made too as that is likely a contributing factor.

Widget

[Mr. Widget]

Can you plot spatially or is that a bad question? Also, when you say EQing, do you use an EQ in your main system (music).

I do plan to do polar plots and waterfall plots at some point. I will need to get a turntable and a bit more experience using the system.

As for EQ. I have found the White 4400 1/3 octaves to sound pretty much invisible. I have tried a variety of other EQs and felt they did more harm than good. I obviously haven't tried all of the EQs out there, only a handful really, but anecdotally there seems to be a consensus that the rotary pot Whites which have recently been discontinued are among the very best if not the very best.

Widget

[Dr.db]

Here is a comparison between the JBL 2397 and one of my Westlake clones. It is interesting how the the wider lips of the Westlake do seem to improve the lower response, but at a sacrifice at the top end. This explains why I always feel the need to EQ up a bit around 6-10KHz.

I know it´s been a long time since...

But I have one question; did the Westlake clones use the 2328 throat-adapter as well ?
Could this cause the difference at the top end ?
If the Westlake clones didn´t use this adapter, I guess their inner height was bigger? Probably 2" height for the westlake and 1,5" height for the 2397....!?

[ivica]

I know it´s been a long time since... But I have one question; did the Westlake clones use the 2328 throat-adapter as well ? Could this cause the difference at the top end ? If the Westlake clones didn´t use this adapter, I guess their inner height was bigger? Probably 2" height for the westlake and 1,5" height for the 2397....!?

Hi Dr.db,

I would expect driver to horn adapter something like on the figure
or 2" horn height as explained in the:
http://www.audioheritage.org/vbullet...ll=1#post49874

regards
ivica

[Mr. Widget]

I know it´s been a long time since...

But I have one question; did the Westlake clones use the 2328 throat-adapter as well ?
Could this cause the difference at the top end ?
If the Westlake clones didn´t use this adapter, I guess their inner height was bigger? Probably 2" height for the westlake and 1,5" height for the 2397....!?

Yes, the early Westlake horns that I copied did use the JBL 2328 adapter. I copied them exactly and also used the JBL adapter.


Widget

[Richard Long]

@ lee

thx for the curve, the red one looks quite good


@ ivica

i´m thinking about to change the horn but i have to do some tests ... and to buy some different horns - thx for the link!

[Richard Long]

Thx for the response.

i have the choice between 2441 and 2450.

I am interested in the difference of the curve with aluminium/truextent between 1.2khz to 10khz. at the moment i drive my 2441 with 2397 from 1.2 to 6.5 and after 6.5 i drive with a Fostex T925. next step is to change to truextent in the 2441, up to 10khz and over 10khz i will change to a Foste T500A MKII.

[ivica]

Thx for the response.

i have the choice between 2441 and 2450.

I am interested in the difference of the curve with aluminium/truextent between 1.2khz to 10khz. at the moment i drive my 2441 with 2397 from 1.2 to 6.5 and after 6.5 i drive with a Fostex T925. next step is to change to truextent in the 2441, up to 10khz and over 10khz i will change to a Foste T500A MKII.

Hi Richard Long,

Why to change 2441Aluminum diaphragm with anything, I would suggest You to change the 2397, with something like Yuichi A290 or A290S, like Tad TH4003.
I have seen a pair of A290S, seems the price OK

http://www.ebay.de/itm/DIY-YUICHI-A2...item1a04cef872

regards
ivica

[4313B]

I recently bought an electro-acoustic measurement system called Clio.

Very exciting!