Walnut Smith Selsted

[John W]

Big thanks to Widget for taking the time chase down the drivers and make these measurements. You’re a gentleman and a big asset to the forum. I really appreciate the consistent help, encouragement and good advice you provide.

I am a little surprised at the jagged response compared to 2404, but then again it’s the great engineering that makes JBL great, not just pretty good.

I wonder if there are things that could be improved upon in the design to smooth it out some? A couple of things I will probably try would be rounding over the lips, and smoothing out the throat a little.

Also, I made a couple measurement errors in the original drawing at the top of the post, the height is really 5” rather than 6”, and the radius is 4 7/8, not 5 7/8.
Here is an updated sketch, showing the no-vane version.

[4313B]

Very cool!

Nice thread guys!

Since I needed a 2404 driver to test John's horns, I asked Zilch if I could borrow one... he graciously offered to lend me one.

So that's where the little trade came in...

To carry out these tests I used my recently upgraded CLIO rig... unfortunately I discovered after the conclusion of my tests and having put everything away that one of the new features, saving the plots directly as jpegs isn't terribly great.

I would always save each curve as a .mls file for future reference.

To sum up... while these graphs look a bit rough, that is the nature of diffraction slots. For the most part the diffraction effect seems to be causing narrowband suck outs... these tend to be difficult to hear. While I did not set these tweeters up in a system and evaluate them subjectively, I have heard quite a number of tweeters under test over the years and these did sound a bit more natural than the baby butt cheek.

Yep, so it's probably best to post at least 1/12 octave smoothing. You can open up the .mls files and apply the smoothing as desired/required.

[northwood]

really really very gorgeous

[Mr. Widget]

I would always save each curve as a .mls file for future reference.

Ideally sure... but I did something like 15-20 separate measurement and saving and naming each one was more of a commitment than I was prepared for. With the plot images 4 or more test plots can be saved at a time along with notes explaining what they are.

Yep, so it's probably best to post at least 1/12 octave smoothing. You can open up the .mls files and apply the smoothing as desired/required.

I agree that saving the .mls files would have allowed that, and in this case it would have been nice to have the option. I guess my laziness bit me in the butt this time. I usually do run my tests with 12th octave smoothing, but in this case there was little change between 12th octave smoothing and no smoothing so I thought I'd post the full resolution plots.

For additional info on the tests:

They were all done at 1m. The tweeter was 4' off the ground and the test structure supporting the tweeters was wrapped in sonex.
There was also sonex on the floor between the mic and device under test and the time windowing was wide enough to far exceed the frequency response of the device under test.


Widget

[4313B]

Ideally sure... but I did something like 15-20 separate measurement and saving and naming each one was more of a commitment than I was prepared for.

I hear ya! I have to keep reminding myself that it is soooo much better than the old days though.