Hi I have a horn that is rated to be crossed at 800hz and a driver rated for 300hz. I'm planning to experiment with different crossover frequencies below 800hz using DSP and equalization as it's a bi amplified active crossed system. In addition, I am curious if I can further achieve the desired frequency by incorporating a plain wave tube type of equal diameter to the horn thoat and driver throat -- effectively extending the horns throat section anywhere from maybe 3-12". Any thoughts?
Getting output at lower frequencies without considering how wide they will play, is one thing.
You're considering the horn loading aspect. Horn loading challenges you in going low. How is it that your horn has an 800Hz cutoff... is it about loading? Waveguides don't really have a cutoff...
You're considering the horn loading aspect. Horn loading challenges you in going low. How is it that your horn has an 800Hz cutoff... is it about loading? Waveguides don't really have a cutoff...
I have wondered this also. I think the horn will not provide proper air mass loading below its cutoff frequency. This will almost certainly affect power handling. It may or may not work fine at lower volumes, don't know.
Adding a tube to the throat may help the lower end by adding moving mass, but will likely have standing waves due to the parallel walls at higher frequencies.
There is really no substitute for trying and listening however...
Adding a tube to the throat may help the lower end by adding moving mass, but will likely have standing waves due to the parallel walls at higher frequencies.
There is really no substitute for trying and listening however...
The recommended crossover for the Ciare PR614 is 800hz it seems. I'm using them with a pair of CP755NDs in a two way configuration to great effect crossed over at 900hz. I would like to add a mid compression driver crossed over at 300hz and in the interest of consistency use the same horn. Look at mid horns in various systems -- they are typically quite large. Examples being GOTO Horns, the JBL 2490 with matching 2451 horns, the big multicell Altec 300hz horns, WE 15A etc. I have a large biradial Iwata horn which I will default to for the mid section and should work fine, though would like to experiment with different options. I prefer the Ciare horns to the biradial in the two way setup I have currently.
If it solves a problem of enabling lower crossover options I would like to experiment with adding a plane wave tube to a pair of the Ciare horns. This raises two more questions while I have your attention -- would adding two compression drivers instead of one with a Y adapter also enable yet an even lower crossover point? And in that configuration is there an advantage to two 8ohm (4ohms) vs two 16ohm (8ohms) midrange compression drivers? The setup is actively crossed and amplified and the levels of each band are specified independently so I'm not sure if the advantage of reduced driver impedance as a pair benefits me in any way aside from playing louder.
If it solves a problem of enabling lower crossover options I would like to experiment with adding a plane wave tube to a pair of the Ciare horns. This raises two more questions while I have your attention -- would adding two compression drivers instead of one with a Y adapter also enable yet an even lower crossover point? And in that configuration is there an advantage to two 8ohm (4ohms) vs two 16ohm (8ohms) midrange compression drivers? The setup is actively crossed and amplified and the levels of each band are specified independently so I'm not sure if the advantage of reduced driver impedance as a pair benefits me in any way aside from playing louder.
Wouldn't it be the opposite scenario in that there is less air volume and thus less mass at the interface where the diaphragm meets the air in the version with a plane wave tube adapter?
This is not really the issue. The loading is more about the horn and its radiation. As far as the diaphragm loading is concerned, the driver compression ratio is the main factor. Consider for example, that a waveguide doesn't offer much loading and they are often used to a much lower frequency.
I'm not sure about that. A horn that has a cutoff will go wide at a higher frequency than a waveguide of the same dimensions which doesn't have a cutoff.. so you'll need more output to cover that. You'll also have to deal with the group delay that going through a cutoff will give, not to mention the resonance of the tube.
If you want to experiment with tubes, consider simulating it in hornresp.
I think the tube will act like a transmission line where the air mass is moving in phase with the driver and quite possibly lowering its resonant frequency. As the wave moves into the horn, the pressure begins dropping to match the room and it becomes decoupled from the driver. In a TL, it is common to add stuffing to the pipe to damp higher frequency waves. This might actually help in your case.
You'll trade a lot of efficiency doing it electronically since excursion increases 4x/octave plus decreasing horn loading support.
It's been done, but long since don't remember the brand/models nor how well they performed, but here's the basics, i.e. we want Fc = ~300/1.5 = 200 Hz = ~13543/200 = ~67.7" horn axial length (includes any driver internal horn) and a suitably large enough baffle to support ~200 Hz/F6 x 'y' angle, then assuming the horn is square and the wall angle is a flat baffle (180 deg) extension = 10^6/(180*200) = ~27.8" square.
With a relatively low eigenmode pipe modulating it I don't have high hopes for it though.
What is an eigenmode pipe modulating it? And where do you get the number 13542? And why 200hz and not 300hz?
The pipe you want to add, it's a 1/4 WL resonator. Speed of Sound in air we use for calculations = 13543"_sec. So it will load to 300 Hz, ergo if you want it rolled off use 300 Hz.
Best bet would be to bolt it on to the horn, measure and eq to your desired response, and run distortion measurements at various spl's to see when distortion spike to unacceptable levels.
If the distortion levels are acceptable at your typical listening levels, no further work is necessary.
If not, you'll have to use a larger horn. Alternatively you can try some very high efficiency midrange cones. No compression driver will outperform them below 1khz.
If the distortion levels are acceptable at your typical listening levels, no further work is necessary.
If not, you'll have to use a larger horn. Alternatively you can try some very high efficiency midrange cones. No compression driver will outperform them below 1khz.
Which midrange cones do you recommend and feel would be equivalent or superior to a compression driver? The drivers I have are B&C DCM414 compression drivers. And the midrange cones of interest are low mass high efficiency low xmax Beyma 10MI100s and Fostex FE208EN full range drivers to cover ~100hz-900hz. Any other recommendations are appreciated.
The Beyma is an excellent choice.
Another great driver is the 10NMBA520. The 10NDA610 is the midrange version.
If you move up the crossover a bit, PHL has some nice 10" midrange drivers as well.
Another great driver is the 10NMBA520. The 10NDA610 is the midrange version.
If you move up the crossover a bit, PHL has some nice 10" midrange drivers as well.
The addition of the pipe would add some more (pure, real) acoustic resistance to the net impedance exhibited by the horn and thereby reduce its cutoff frequency. In my opinion, the idea could work and if I'm not wrong, it has already been tried in the JBL M2 monitor that mainly consists of a 4" pipe followed by the shallow horn profile. This should be clear from its side view (below). Now, it becomes difficult to imagine how things would've been without this pipe.
https://www.audiosciencereview.com/...9f77-ae7e-4766-ac0f-0bbdd9e64b4e-jpeg.150469/
https://www.grc.com/acoustics/an-introduction-to-horn-theory.pdf
https://www.audiosciencereview.com/...9f77-ae7e-4766-ac0f-0bbdd9e64b4e-jpeg.150469/
https://www.grc.com/acoustics/an-introduction-to-horn-theory.pdf
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It's clear from the photo that the entire M2 horn depth is about 3.5 times that of the D2 driver's 1.4" throat entrance.
The sonic consequence of adding a 4" pipe is immediately apparent by simply speaking through a 4" tube- it is not a high fidelity experience 😉
Art
For 300Hz - 900Hz, it'd be better and cheaper to mount small a cone driver on the horn, rather than a compression driver.
Im' sorry, that was supposed to be 4 cm, not inches, maybe a better picture (below) that shows the 40mm knuckles. My point, however, was that the flare portion of the horn is too thin and would be therefore be almost inconsequential (loading-wise) without the pipe.
https://www.audioheritage.org/vbull...ompact-monitor&p=375628&viewfull=1#post375628
https://www.audioheritage.org/vbull...ompact-monitor&p=375953&viewfull=1#post375953
Agreed.
Calling the 40mm throat restriction "knuckles" a "pipe" threw me off. The knuckles aid in HF dispersion as well as LF loading, though still require a dual diaphragm driver for the acoustic crossover point of 800Hz.
I agree with ErnieM and Hollowboy that adding midrange cones to the same horn sounds better than adding a second horn and compression driver or a dual driver Y adapter to cover the 300-800Hz range.
The B&C 4NDF34-8 or 4NDF34-16 sound really good sharing a HF horn.