Horn Recomendations for 1.5" Drivers

[Rudy Kleimann]

More info on that here, including height vs. frequency chart:

http://www.jblpro.com/pub/technote/tn_v1n07.pdf

Clearly, stacking's no panacea, either, as it becomes multiple sources lobing throughout the entire frequency range....

'zactly, Zilch.

Regarding lobing in my first post, I was talking about interference-induced lobing effects from multiple drivers reproducing the same frequency, specifically a midrange and horn through the crossover region. This would cause strange irregularies in frequency response in the range of frequencies near the crossover point as your ears move off-axis. The same lobing problem would be true for multiple horns or multiple drivers of any type, but who wants or needs that in home hi-fi anyway?

Back to diffaction: To me, that is exactly what the "lips" for the Smith horns are for: to maintain pattern control in the vertical plane to a much lower frequency than the wood horn can do alone. In the case of a smith horn, it sticks way out beyond the baffle, so diffraction pattern at low frequencies would be even more than 180*, right? Talk about reflection problems?

What I was getting at is that a smaller horn allows you to get the drivers closer together (midrange and tweeter, for example) and that reduces the off-axis irregularity problems in the frequency range near the crossover frequency, but if one is driving a horn, you must realize that the horn will turn into a diffraction slot with near 180-degree dispersion if used down to a frequency lower than the small mouth dimension can control. If you want 180-degree dispersion, fine. But if you are trying to control the dispersion pattern, you must use the horn above the frequency where pattern control becomes effective.

[Zilch]

The trick seems to be to match the directivity of the horn and the crossover frequency to that of the lower frequency driver at that frequency, at least in the horizontal, so that the two sources blend coherently. From there on up, the objective is constant directivity and power response, such that the reflections may then be uniformly handled by the room.

In 4430, for example, the 2344(A) 100° beamwidth in both axes is matched to the 2235H diaphragm dispersion of 100° at 1 kHz.

For a 12" woofer, the target frequency would be ~1.2 kHz. An 8" woofer and an 85° horn wants more like 2.4 kHz for a seamless blend....

[Steve Gonzales]

[quote=Rudy Kleimann]

The same lobing problem would be true for multiple horns or multiple drivers of any type, but who wants or needs that in home hi-fi anyway?


Well Rudy, I'm guilty of that. I do my own thing in regards to my setup. I've been very careful to not recommend it as what to do (multiple pairs), and have always stated that it is just what I like. I will say this though., and this is where it gets tricky, well I do appreciate the science, it sounds pretty damn good. I've seen some unorthodox configurations in my time, from some kid with every speaker he could get his hands on, piled up and stacked, to massive full horn W.E./Altec/JBL systems in ridiculously small rooms. I fall somewhere in between. Unorthodox, but I also know how a great system sounds too. I wouldn't continue to keep running my side by side pairs if it didn't sound very good. I believe that I know what good imaging is, what a great soundstage is, etc-etc. So, therein lies the paradox. On paper, it would seem that there isn't a snowball's chance in hell that it should sound as pleasing as it does. Are there compromises? Yes. Do they outweigh the reality of how it actually sounds? Not to me or to quite a few friends that range from the very informed to not-so-informed (in the technical aspects). The addition of the foam lips makes the 2397's more focused. They didn't ever sound harsh or anything. Thank you for the explanation. I appreciate it and value it.

[Rudy Kleimann]

I agree 100% Steve! If it sounds good, that's all that matters. If it's fun, play on!

I certainly don't want you to feel I'm faulting you for your setup. You are obviously enjoying your JBL system now, whereas my dream system exists only "on paper". Finishing my house takes priority in time and dollars. In the interim I make do with a pair of JBL L166's.

This thread (and many other threads I've read on this forum) have served as an exercise in Engineering design Philosophy for me to learn by. I've got quite a bit of JBL Drivers, horns, and cabinets sitting in storage, but I haven't decided what of them I'll be using yet.

Since I don't have the budget or test equipment to try all kinds of prototypes, I do all I can to read and learn by what others have done. This site and the JBLPRO site have taught me a lot already; hopefully I can avoid costly mistakes in my design by trying to apply all I can from the work of others.

[subwoof]

I have repaired a few UREI coax horns that use this foam technique - inside the horn there are 2 different types of foam that resemble undercoating on a car and the lips have a 1/2" thick sculpted piece of closed-cell foam on all 4 sides and the edges are rounded.

The added foam probably doesn't add to it's effective length but it's there for *some* reason...

And remember the room itself is the DOMINATE parameter tand it can only be controlled to a small degree ( S.A.F.)



sub

[Zilch]

Lipped Smiths:

[Steve Gonzales]

You know Zilch, those smith's of John W's were the first thing that came to mind with me too. I guess that they have more engineering to them than I first suspected.

[Guido]

Lipped Smiths:

Where do the black ones came from?

[Mr. Widget]

Where do the black ones came from?

I believe that photo came from an eBay auction... there is no real mystery though. The JBL Spec sheet for the 2397 states, "Vertical dispersion is largely dependent on the baffling; with the recommended cylindrical baffle extending at least 3 inches above and below the mouth, a nominal 60° vertical beam-width is achieved".


Widget

[Steve Gonzales]

That is correct Widget. Member John W. sold those on ebay. They were removed from an installation in Seattle. He said that they were built by a well known local company there in the 80's.

[cvengr]

This just begs for a custom horn to be made in the shape of 2 large red lips.

[Rudy Kleimann]

Yeah, Mick Jagger Horns