Quick & Dirty 4430-Inspired Two-Ways Part I

[Zilch]

O.K., so help me interpret and understand this, please.

Looks like they're all three the same game, essentially, but 4430 has 5 dB more boost (not insubstantial).

N200B could/would have more than 3110 if it were operated at, say 25% rather than 50%. (Gonna resolder stuff and try that.)

N200B level control adjusts the highpass Q, apparently, within limits. While not intended for CD compensation, it might be successfully used for that purpose.

Special thanks to Giskard for the requisite curves....

[Zilch]

"Real deal" 2344A horns provided for this project by forum member Mike Caldwell have engineered constrictions in the diffraction slot to transition from 1" round to race-track oval narrow (~5/8") opening in horn shown below. I haven't found the JBL reference again yet which describes the essential purpose, alas. I CAN, however attest that there's an immediately apparent difference between the performance of PH-316 (which doesn't have it) and 2344A (improved dispersion and transparency).

The OASR tech note touts the lowered distortion advantage of NOT having such constriction, however. PT Waveguides apparently continue that diffractionless design philosophy.

http://www.jblpro.com/pub/technote/tn_v1n21.pdf

http://www.jblpro.com/PD5000/PDF/PT_WaveGuide.pdf

[Robh3606]

This explains it pretty well

Rob

[Robh3606]

Now the other view. Your cards are in transit.

Rob

[Zilch]

O.K., 0.7598" then.

Your cards are in transit.

Oh, BOY, we'll have ALL the pieces soon!

[Ian Mackenzie]

That White paper is a good read.

I spent 12 months trying to make the passive crossover eq from the simplified schematic in the paper before emailing JBL and asking for the schematic (before it was public domain) which they actually send me.

I have it that the Tad 2001 works very nicely on this horn with some tweaks to the eq.

Ian

[Zilch]

Depth is 7" from rear of driver to mount surface, approaching alignment with woofers, so polarity is re-reversed when connected to L200B crossovers. In this setup, 2344A is operating at its lowest recommended crossover frequency, 800 Hz:

http://www.jblpro.com/pub/obsolete/2344A.pdf

[Zilch]

Real deal (albeit funkified) 2344A horns, here with LE85 and L200B crossovers. N200B L-Pads set to 20% (9:00) position for presumed maximum HF boost, LE85's are still attenuated an additional 3 dB with an external 16-Ohm L-Pad. Quite listenable, getting close.....

[Zilch]

Inexpensive ($38) floriform JBL OASR horns (85° x 85°) are thread-on mount, 1-3/8"-16. Removing adapter on 2426J (not easily accomplished on one of them; had to use lathe chuck and oil-filter wrench) exposes threaded "snoot." LE85 is easily adapted using P-Audio PC-35 throat adapter, shown.

Surprisingly, the relatively small (8-3/4/" square) OASR horn assemblies are deeper than 2344A behind the panel by about 1". I have no clue what these are (CD or not?), or the requisite equalization, until Mr. Widget measures them. They sound "tweety," which may be good.

Clearly, LE85 does not conform to the "Optimized Aperture" design guidelines:

http://www.jblpro.com/pub/technote/tn_v1n21.pdf

It's not clear that 2426 does either, for that matter. What, then? 2406 or 2407? This "Optimized Aperture Symmetrical Radiator" is used in Marquis 112 with 2418H crossed at 1.6 kHz, Marquis MS28 with 2412H at 2.8 kHz (MTM center anyone?), Sound Power SP 212-A with 2426H crossed at 1.6 kHz (nice response curves!), smaller SRX Series monitors with 2417H (1.2 kHz) and 2226H (1.3 kHz), CSP18 with 2418H, unstated crossover frequency, here called a "Conical Waveguide," and unknown others, perhaps.

[Note: Order gaskets for these as well to use as mounting template. NOT a round hole.]

[Zilch]

OASR under test at Widget Works. Comprehensive tests and measurements with different drivers take less than an hour using CLIO system:

[Mr. Widget]

So how do the relatively inexpensive OASR horns sound? I couldn't tell you. They do measure pretty well on axis though don't quite have the off axis response of the 2344. Here is a plot comparing the on axis response response of the 2425 on a 2344 and a 2427 on the OASR horn.

Red 2344
Blue OASR

[Mr. Widget]

Both of these sets of plots are using the CD (constant directivity) equalizing network from a 4430. The Upper plot shows the on and off axis response of the OASR with 2427. The lower is a 2425 with 2344 horn.

For both sets of plots.
Red is on axis
Blue is 15° off axis
Green is 30° off axis
Purple is 45° off axis

[Mr. Widget]

Here is a plot with no compensation comparing both the LE85 and the 2427 on OASR horns.

Red is LE85
Blue is 2427

[Mr. Widget]

Here is a plot of an LE85 both on and off axis. Again, there is no compensation so we see the actual roll off of the horn.


Red is on axis
Blue is 15° off axis
Green is 30° off axis
Purple is 45° off axis

[Mr. Widget]

Based on these measurements, I'd like to see a bit more top end, but as a mid horn between 1KHz and 10KHz, this may be just the ticket for a low cost solution. We will have to wait for a subjective evaluation.

Widget