Nope... just another bi-radial... and you know what I think about those.Originally Posted by Zilch
As for the Array Series... I haven't seen or heard them so the jury is still out. They may be good... tipping the H9800 on it's side may make it sound better too. I meant to give that a try when Giskard first showed us a pic of the Project Array Series... but it is fairly down on the list and hasn't happened yet.
Widget
I too have been doing a lot of listenin' here for the same reason. A lot of reading in the LHS Library, JBLPRO site, and others, to try to get a handle on what's going on and how to get it right.YYYep. That's why I hang around here listenin' ...
(mostly)
-grumpy
This is what I think I've learned so far:
As you go down in frequency, the horn's dispersion/pattern control in the horizontal or vertical plane is largely influenced, yea, dictated, by the dimensions of the mouth of the horn.
Smaller vertical mouth dimensions are a balance/tradeoff between 1) a large versus smaller cabinet, and 2) (most importantly in home listening) maintaining good vertical pattern control versus vertical lobing/cancellation effects due to wider spacing between between the horn driver and the adjacent driver -in the range of frequencies near the crossover frequency.
In other words, the closer the drivers are as you look at the front, the less comb-filter and resulting lobing effects you hear as you move up and down in front of the drivers (with a lower 6dB/octave crossover slope making it worse over wider range of frequencies than a 12,18, or 24dB/octave rate), -but- the big drawback is that you lose dispersion control if the frequencies are low enough that the small vertical dimension of the horn can no longer control the dispersion. Below such a frequency the lower the frequency, the more the sound wave just diffracts over the lip of the horn, "spilling out and over" instead of being directed by the walls of the horn.
Check out the vertical dispersion pattern graphs on a 2380 horn and a 2352 horn at the JBLPRO site for a working example. Notice that below about 2-3KHz the 40-degree vertical pattern control just goes to hell on the 2380, where the 2352's advertised 50-degree vertical dispersion pattern control holds up well down to about 1KHz. That's the difference between a vertical horn flare dimension maintained to only 9.25" on the 2380 and 16" on the 2352.
Note also that the 2380A brochure states, "...the horn's small vertical mouth dimension (just slightly larger than the compression driver...) allows very compact systems..., that it "provides vertical pattern control to 2KHZ... Should vertical pattern control be required below 2KHZ, 2 or more horns may be stacked to restore full bi-radial performance."
When you consider how narrow the Smiths are vertically, is it any wonder they would have reflection problems well into the treble frequency range -perhaps up to 5KHZ or higher? without "lips" to extend/maintain the horn's vertical mouth dimension. The lower end of a driver's output connected to such a narrow horn would probably wrap way back around the mouth, creating all kinds of reflection issues -maybe even from the speaker baffle it is protruding from?
As far as the case of Steve Gonzales, is the absorbent foam just "absorbing" the ill effects of diffraction at lower frequencies? The "lips" would remedy the shortcoming in the first place, right?
As I stated above, I think I got it right. Do I? Giskard? Widget? Zilch? Others?
Well here is the answer on the horn type if the add copy is correct
RobTo achieve their superlative performance, the 1400 Array, 1000 Array and 800 Array loudspeakers feature advanced-technology Bi-RadialŪ-horn compression drivers mounted vertically in a freestanding configuration.
Well it's basic physics concerning the extended baffle. Just like any radiating source ( woofer on a baffle for example ) the usable LF response / curve is a function of the *length* of the return path to the energizing source.
The length of the horn might be the dominate function for the cutoff frequency but it's not the only story. This is mentioned in the JBL acoustic lens tech manual where it says the 2390 can be used lower provided a baffle is used.
This why the old D130's actually had decent bass when installed in a 60's popular basment infinite baffle, the WALL
I agree that the extra length on the 2352 makes it a great horn for the 2435Be but the poor driver looks lost with all that horn and it's not that living room freindly.
As for steve's foam lips, I think the absorbtion was 20% and the added length was 80% what he experienced so duplicating / measuring / testing that would be one heckuva thread for the insomniacs amongst us.
sub
Rob,
My last and probably dumb idea is a large conical wave guide.
It would be large to run down to 650 - 800 ....probably about 20 inches or so in diameter. A bit like Earl Geddes thing you would get really good power handling and low distorton. I still plan to buy the 14 incher (1500hz version) from Parts Express and give it a wirl.
Thank you for the info. I've got to get that bloody RTA that Zilch has prompted me to acquire. As usual, I rely on what my ears tell me sounds correct (to personal taste). Now if I could just figure out a way to have the baffle/lips, and have it not look like shizznite.
How about the Vertec waveguide then (below)? Kinda like 2396. P-Audio makes one, too, for 1".
There's the round-to-rectangular transition throat some have been seeking. Just saw it off at the appropriate crossection.
[I'd have trouble calling that "rapid flare," I think....]
Ian just posted in another thread:
http://www.enjoythemusic.com/magazin...acurve2496.htm
$250 at Guitar Center. Ask 'em to throw in the mic and cables for that, too.
The 2396 is a modified throat from the big 2365 horn and I actually played with a pair for awhile. JBL had 'em in the original 1997 sale for 20 bucks..
Flushing that horn into a baffle creates a pure slit source and without some guidance it might be a little difficult to integrate BUT it sure could re-part someones hair line when sitting on axis...
But I think all this can be put to rest by installing a pair of 2360's in the living room and telling all listeners that it's gonna gound great.
Put seatbelts on the couch and sandbags by the door.
If you can't dazzle them with brilliance, baffle them with bullshit
Seat belts..with JBLs......what?.....We need Air-Bags
how about this?
RC
YEOW!! Those'll peel the wallpaper, if you're not careful.
Well, now we've gotten down to my response to Rudy's question:
I conceptualize the Smith horn as a segmented horizontal diffraction slot. The cylindrical baffle or "lips" control the vertical diffraction pattern.
But, what's the polar response in the horizontal, in detail? Do the individual segments beam with increasing frequency creating lobes of a different sort, i.e., not from interference, rather, from power response attenuation?
Indeed, at 8 kHz they're 3 dB and not shown above that frequency in the "Lateral Dispersion" plot:
http://www.jblpro.com/pub/obsolete/2397.pdf
"Because of the action of the power distributors, the 2397 is notably free of high-frequency beaming, and maintains its effective 140° coverage to the highest audible ranges, with only minor lobes appearing above 5 kHz."
If their magnitude above 8 kHz were known, would they still be considered "minor" in the context of the smooth power response control achieved with newer design horns and waveguides?
And finally, as bottom line, is 140° horizontal dispersion even desireable in a home system? Not according to JBL's current "state-of-the-art" design guidelines....
*****
With the 2396 mounted vertically, the uncontrolled horizontal dispersion is 160°, as I recall, a "feature" touted for their use in Concert Series stage monitors. Think 2405.
See Don's post regarding rotating the slot vertical here:
http://audioheritage.org/vbulletin/s...2&postcount=12
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....
I thought they would also but surprisingly not that bad at all. I bet they would be a little edgy with SS but with low powered tube they are sounding sweet as peaches. Until I also find the right horns, Im going to ride out the storm with those.YEOW!! Those'll peel the wallpaper, if you're not careful.
RC
As Zilch once said in the Q&D thread, that horn/driver combo "looks like a bug on a tricycle"
I wasn't referring to the length of the 2380, 2352, and the Smith horns, but the horizontal and especially the vertical size of the mouth of the horn and its substantial impact on pattern control.
As I understand it, baffle size would have little or nothing to do with pattern control, except for wavelengths that are so long that they diffract around the corner of an abruptly ending horn flare (a Smith horn has virtually no vertical flare to it, just a rounded edge to it). Energy at these long wavelengths would basically radiate into a 1/2-space (180 degree) pattern in the vertical dimension, gradually reducing the radiating pattern into the horn's design control pattern as the frequencies went up and the wavelength became short enough that the horns' small vertical dimension can maintain control of them. In the case of a Smith horn it seems that this would be happening into a fairly high frequency, causing lots of reflection problems in the lo-end if the horn is used down to lower frequencies, and not a problem once the frequencies are high enough that the small vertical mouth can maintain control.
Correct me as required-
I'm wrestling with the thought that soft absorbing foam could possibly serve as an extension of the horn, much less a baffle. In my mind I would've thought it was 80-100% absorpsion and 0-20% (at best) added mouth size in the vertical plane. If it is made of styrofoam or similar, I would think it would act as an extension of the horn mouth dimension or serve as a baffle for it that would stop vertical diffraction at the lower end of the horns' range. In that case, I would agree with subwoof.
What are the JBL "lips" made of? Hard or soft material? What about Steve G's?
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