S'pose there was a $125 200-Hz JBL Horn

[Zilch]

A PT waveguide, actually:

[subwoof]

I snagged 2 of those off ebay and I also have the drivers and 8's BUT I don't have the nice aluminum condoms for the 8's...

Any unique engineering inside them that precludes DIY??

sub

[Zilch]

All the parts are relatively inexpensive, including the phase plugs, a surprise. It's the drivers that are expensive.

DIYers will have to check whether the cones of alternative drivers line up with the phase plug. The compliance on 2250s is VERY stiff, and it's a tiny half-roll cloth surround. 2118s come to mind. I can check those.

The other issue is getting an adequate seal to the driver at the rear of the back can. JBL doesn't list a gasket for that for 2250, even, so, assuming it's supposed to be tightly sealed, I used foam gasket tape. The front of the can seals to the driver with the traditional "Noodle."

Another option is not to use them in compression mode, rather, merely as waveguides. The throat is 4" diameter, and 104H(-x) is a perfect fit, for example. I don't know how low various LE5 derivatives will play on waveguides. Edgar use them on Tractrix. This might work, too.... :dont-know

The HF can be 243x, 1.5" 245x, or, as I have shown, with JBL throat adapter, thread-on 1".

If I was one of those bass horn enthusiasts, I'd sure be lookin' real hard at these.

These are two-ways with LF augmentation, right Sub?

[They'll play 132 dB continuous.... ]

[subwoof]

Back in 1980 I started making 4530 clones for the band market and made hundreds of them. A few times I made custom 2-3 ways with extended tops for theaters, clubs and other semi-permanent venues that wanted high output plug-n-play.

Of course designing the wood flares and making comp chambers was fun along with the complete lack of flat front horns. We had to get pretty creative.

Here is a quickie cabinet profile sketch of that waveguide if it sat on top of a jbl scoop clone. Using a foam woofer wouldn't help the LF so sticking with the higher output, tight suspension cones will actually work better. I *think* the Nd 15 is too deep? I know the auto ones would be but unsure about the SRX model(s)

With a sharp rolloff at 30hz, this would re-arrange caulking and dryclean your drapes. Size would be 24 X 24 X appox 60

sub

[Robh3606]

Another option is not to use them in compression mode, rather, merely as waveguides. The throat is 4" diameter, and 104H(-x) is a perfect fit, for example. I don't know how low various LE5 derivatives will play on waveguides. Edgar use them on Tractrix. This might work, too.... :dont-know

Hello Zilch

He used Le5-2's. The rising response is what you want when you horn load them. If I remember right he had them play into a throat with a rectangular cut out and a backchamber. It was a rectangular tractrix horn. Unfortunately you can't just drop them on the waveguide. You would have to come up with a throat assembly to load the waveguide and a backchamber. There are a couple of his DIY articles about. There is one for that horn somewhere. I think it was in Speaker Builder?? I have it at home.

2118?? I would think more towards am M 209-8. That's hornloaded in the 4315??? The one's Mike Baker had at the MAF. Similar set-up this seems to be the next generation.

Rob

[jackgiff]

A PT waveguide, actually:

I would want some, yessir!!!

And some LE14H-3's to put under them.

[Zilch]

If they're made like the 18s, 15" Nds could poke through, looks like. The pressures aren't huge, so a resiliant seal of slits would probably do well enough. Pipe the vent out the back, if necessary:

[Zilch]

Edgar Tractrix. They sold for $261, more than a pair of these PTs. Compression, but no phase plug. Bolting a 2118 with a sealed back chamber on the PT appears analogous. That I can try. I haven't measured anything for a baseline yet....

[toddalin]

Edgar Tractrix. They sold for $261, more than a pair of these PTs. Compression, but no phase plug. Bolting a 2118 with a sealed back chamber on the PT appears analogous. That I can try. I haven't measured anything for a baseline yet....

So you got hold of them! Cool!

[Zilch]

So you got hold of them! Cool!

Nope, somebody else bought 'em.

Rob says there's an article in Speaker Builder, which maybe details how to make them.... :dont-know

[Zilch]

2118 seems to be a "Go" with the phase plug, mechanically. Add the larger diameter (~3.5") 2250 dome, remove the tire and make a 1/4" plywood adapter ring to seal the rear to the stock back can with foam gasket tape.

[Gonna get yelled at, I jus' KNOW it.... ]

What these have is best characterized as "SMACK!"

[toddalin]

If they're made like the 18s, 15" Nds could poke through, looks like. The pressures aren't huge, so a resiliant seal of slits would probably do well enough. Pipe the vent out the back, if necessary:

Not to hijack the thread, but this just looks so wrong..., like someone forgot to put a magnet on it..., sure it's not a passive radiator?

Also, looking at the pic it occured to me that maybe some of the difference between the Alnico "sound" and the ferrite "sound" is that the Alnico magnets are on the inside of the V/C (away from the windings) whereas the ferrite magnets are on the outside (toward the windings), and that's just account for something. I'm assuming that the Nd magnets are also inside the coil like the Alnico magnets?

[Zilch]

It's quite amazing, Todd.

I can literally pick that 18" driver up with one finger.

For those who haven't read it, here's the Tech Note on the CMCD (Cone Midrange Compression Driver) technology I've shown above:

http://www.jblpro.com/ae/pdf/CMCD%20TechNote.pdf

[pos]

Is it the PT-K95MH ?
It sure looks appealing! Do you think it could be suitable for a studio monitor?

[Zilch]

Yes.

And from what I'm hearing, yes.

I don't have measurements yet.

[18" square.... ]