Dear Multitask,
That's the horn from the JRX125/225, a modern version of the 2370 you could say. At 12"x6.375"x5.75", that horn is usually crossed as high as 2kHz. There are a lot of people who have modified JRX cabs with the Selenium D220Ti, but I don't think they changed the crossover frequency. But I guess, you chose 1.3kHz for matching directivity with the 12" woofer beneath.
However, the horns in consideration here are cinema horns that are as wide as the LF baffle itself (see post#8) and 12-14" deep, which is at more than twice as deep as the JRX. With such dimensions, these could properly load a compression driver to much lower frequencies (~700Hz or so).
Regards.
I'm sure at least a few on the forum use/have used these cinema horns and could confirm these points for the OP.
That's the horn from the JRX125/225, a modern version of the 2370 you could say. At 12"x6.375"x5.75", that horn is usually crossed as high as 2kHz. There are a lot of people who have modified JRX cabs with the Selenium D220Ti, but I don't think they changed the crossover frequency. But I guess, you chose 1.3kHz for matching directivity with the 12" woofer beneath.
However, the horns in consideration here are cinema horns that are as wide as the LF baffle itself (see post#8) and 12-14" deep, which is at more than twice as deep as the JRX. With such dimensions, these could properly load a compression driver to much lower frequencies (~700Hz or so).
Regards.
I'm sure at least a few on the forum use/have used these cinema horns and could confirm these points for the OP.
My point was that a long, deep horn (vs. short one) essentially implies a slower flare rate, making the horn more suitable for LF reproduction.
And the longer (deeper) it gets, the earlier (in frequency) its acoustic resistance (real part) rises to useful values, once again, implying an improved LF reproduction.
And the longer (deeper) it gets, the earlier (in frequency) its acoustic resistance (real part) rises to useful values, once again, implying an improved LF reproduction.
Oh, so "horn vs waveguide" ? Technically speaking, anything that resembles a "pipe" will be able to load the driver!
In my opinion, both the JBL Screenarray (vertically asymmetric) and Progressive Transition (PT) waveguides are simply bleedovers between diffraction type horns and standard ones. There are other threads here where people show how to obtain such profiles (and results), from standard ones, and the term "waveguide" simply appears to be a horn that places large amount of importance on dispersion.
I agree with that there's no point in trying to define a cutoff frequency for a waveguide, like with an exponential horn etc. However, a physical dimension like length/depth is a "very" fundamental aspect that no waveguide/horn/anything else can violate. Besides, if you ask me, I would only say that waveguides and horns may have differing dispersion, but both match acoustic impedance to the airload in front of their mouth area and larger dimensions (mouth area) do that to lower frequencies.
In my opinion, both the JBL Screenarray (vertically asymmetric) and Progressive Transition (PT) waveguides are simply bleedovers between diffraction type horns and standard ones. There are other threads here where people show how to obtain such profiles (and results), from standard ones, and the term "waveguide" simply appears to be a horn that places large amount of importance on dispersion.
I agree with that there's no point in trying to define a cutoff frequency for a waveguide, like with an exponential horn etc. However, a physical dimension like length/depth is a "very" fundamental aspect that no waveguide/horn/anything else can violate. Besides, if you ask me, I would only say that waveguides and horns may have differing dispersion, but both match acoustic impedance to the airload in front of their mouth area and larger dimensions (mouth area) do that to lower frequencies.
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Well, you're talking scaling, and scaling does cause the frequency axis to scale inversely as well .. (I had asked that question to which Mr. McBean answered yes, pointing to the resize option within Hornresp).
I'm surprised you're asking that! With no real part in its impedance to load, how could you expect the horn/waveguide to put out any real acoustic power into the air? Well, attached is the manufacturer's take on terminology for the Screenarrays.
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I just happened to notice that the Hornresp pictures you show in post #30 uses a rather large throat, about 3 inches or so, whereas the Selenium D220Ti in question has a 1-inch wide throat.
From the pictures in #30, I feel that the throat diameter appears strongly influences the LF capabilities (and loading) of the OS "waveguide", because a larger starting diameter/throat you would be able to get a slower flare rate and good LF loading.
Also, it's worth noting that the JBL Screenarray horns have an initial pipe-like section after which the actual flare begins. I guess, that would certainly make a difference in terms of flare-rate when compared to the JRX 338800-001 horn that begins right at the throat.
I'm just trying to recall where we were at with this, but IIRC there was a point that was explained by the throat resistance being down by half at 3k, down to 10% at 1k5, and yet the response is not down 3dB until 750Hz. (Edit: yes, that loading is not that important. There was another point as well about the mouth.)
The units I've used are cm... those are 1"CDs being simmed.
And thirdly, I get the feeling you are not convinced by what I've shown. Why not do some sims of your own to demonstrate the point.
The units I've used are cm... those are 1"CDs being simmed.
And thirdly, I get the feeling you are not convinced by what I've shown. Why not do some sims of your own to demonstrate the point.
AllenB said:
OK got it now, I had the impression that the red line on the throat of the horn was what was supposed to be 10cm or 4 inches.
AllenB said:
I already understand (from literature) that the loading offered by an OS depends on the wall angle and the throat size, and had already accepted in post #27 that it may not be very useful to specify a cutoff for such profiles. Nevertheless, we're still talking about same angles and throat diameters, i.e. similar flare profiles, which may not be the case with the horns in question.
I'm not very conversant with Hornresp (though I have it), which was why I was looking at what you were showing, else I could have gone simulating myself, just as you say. Besides, I do not know if Hornresp can add a pipe to an existing flare.