The old man in 'Moonstruck': "I'm so confused .........

[cgregory4]

Since I got this JBL 'bug', I've bought at least 8 pairs of speakers, as well as enough drivers (except 076, which are scarce as hen's teeth!) to cover the floors in 2 rooms and all my closets.

My confusion -- well, truthfully, just one aspect of such -- comes from wanting to play with compression drivers. The mid-range. The frequencies I still hear clearly. But, as Dylan says, "The Times, They Are a Changin'."

So, first, I bought a bunch of 1" throat drivers with various 1" inlet horns.

Then someone I respect comments, " Only an idiot would think a 1" could produce the range and detail of a well-designed 2" with the correct phase plug!" (What the hell is a phase plug?) So. I start collecting 2" throat drivers that weigh so much that they could be used as trotline weights during the spring runoff on the Colorado River! And, of course, the requisite horns.

Finally, the 'coup da grass': "The most modern and desirable designs are the 2435s and 2452s, with smaller 1 1/2" throats and superior phase plugs! Quit living in the 70s you fool!"

Honestly, what is the deal? Is the largest throat the most desirable, and will the next wave will be lightweight 2" throat drivers, with lightweight magnets? If the 1 1/2" is so well-designed and capable, why don't I see treatises on how to efficiently couple 1 1/2" throats to older 2" inlet horns -- without discontinuities in the horn/driver connection? Did I miss it when JBL started selling an H92-1.5? How do I get out ahead of this madness?

Help!

[Maron Horonzakz]

Actually the 2 inch units starts out at 1 1/2 near the phase plug...JBL 375,,TAD 4001 etc.

[fpitas]

I suspect the "magic" is in the larger diameter diaphragm, not the exit diameter; and as the drivers were pushed to higher frequencies of operation, the smaller exit diameter of 1.5" was desirable from a dispersion standpoint.

Francis

[cgregory4]

I suspect the "magic" is in the larger diameter diaphragm, not the exit diameter; and as the drivers were pushed to higher frequencies of operation, the smaller exit diameter of 1.5" was desirable from a dispersion standpoint.

Francis

Thank you, Francis. I suspected the same thing. 1" to 2" to 2/1.5" -- as the designs progress. However, it's the preserving (even enhancing) of the 'magic' through the lens and out into the audiosphere that puzzles me most. Is there a short horn (Like the 2311) that acoustically and mechanically transitions the 'magic' from the 1.5" exit out through the lens? Every horn I have lying around (long or short) would cause an extreme discontinuity at the driver/horn interface. Does that matter? Or, should I just get out the tool box and attach any ol' horn with a 1"/1.4"/2" inlet to the driver? Yes, that last sentence is a 'stupid' interrogative -- but it expresses how I feel: clueless.

Greg

[JeffW]

Those with more technical expertise will be the ones to give the accurate run down, butThe newer "snoutless" drivers have a different flare angle or expansion rate or whatever it's called. They are better off being mated to horns with inlet geometry that supports that angle. Not to say newer drivers/older horns can't be mixed/matched, just that it may not be optimal. That's just a broad view that's not terribly exact, correct, or accurate, just the big picture between the two different configurations. If nothing else, maybe somebody can correct me and help spell it out in more detail.

[cgregory4]

"They are better off being mated to horns with inlet geometry that supports that angle."

Exactamente!

Now ..... What/where are those critters?

Greg

[fpitas]

The only 1.5" JBL horn (waveguide, really) that I know of that is available to DIYers is the PT95HF. I haven't looked lately, but those may not be available anymore.

Francis

[Alien_Shore]

There are numerous articles available that provide some theoretical background on horn design. This one in particular strikes a good balance of science and application, in discussion of a reverse flair design:

Wide Angle Dispersion of High Frequency Sound - Abraham Cohen

[more10]

It is difficult to design a horn which spans more than three octaves. Starting at 20 kHz we reach 2500 Hz using this rule. This kind of horn should be driven by a compression driver with a small enough diaphragm. 1.75" VC (1" exit). Unfortunately you will have to look at Altec or TAD for the good vintage ones and Radian for modern versions. JBL never made good 1" drivers.

Three octaves down from 2.5 kHz is 300 Hz. Such a horn is really big and for most people unpractical. JBL has made a good driver for this span, the 248x. But all old 2" drivers (4" VC) have a snout with 182 Hz angle, so they where made for this purpose. The snout of the 2445, 2446 etc is there so they could use the new drivers with existing horns.

If you want only one horn, it is possible to create a horn for 800 Hz all the way up. It will be beamy though, only allowing one or two people in the sweet spot. For such a horn you should choose a 3" VC driver. Altec for vintage and Radian for modern drivers.

If you still insist on using a JBL 4" VC driver in a 800 Hz horn, you will have to spice the top end with a supertweeter.

This is a proper 200 Hz horn with a 2441: