Can you show me a round horn doesn't have to have an on axis dip? I get the small sweet spot, but that's why I figure you'd want to listen on axis, not slightly off axis. Though maybe a deep horn would not show these on axis dips that seem to be linked to symmetric waveguides.
I'd want to avoid any slotted kind of throat section in a horn for reference/studio use. I don't see the OS throat as a slot opening, so I'd disagree with you there
. The OS throat makes sense from a wave shape viewpoint, a slot doesn't.
Then all waveguides and horns would have slots.
My largest waveguide had a very small hole, almost nothing. It was the Abbey waveguide that exhibited the largest hole, because it mouth radi was too small. As shown by MAbat in another thread the hole is all about the mouth termination, nothing else, and can be eliminated with a good design. Elliptical does NOT eliminate it, just spreads it out more.
As to the off axis pointing direction, I would do this with any speaker as it enhances the size of the sweet spot. It does not make it any better or worse in that location, just wider.
Mouth shape will have almost nothing to do with bandwidth on axis. It's up to the driver size and throat size and it's mostly a constant. Raise the driver size and throat size and the HF limit will lower, make them smaller and this limit will grow. The LF limit is entirely dependent on mouth size to hold the directivity. So the widest bandwidth is obtained with a small driver in a very big horn - no surprises there! This is exactly what the NS-15 uses from about 700 Hz up. Try to lower the 700 Hz and you WILL cut off the high end, making it beam, etc. - it will not be CD at the upper end. To me this is critical. This will require another driver and unfortunately another crossover.
All I am saying is a 200 Hz flair horn and compression driver will not give you 200 Hz performance. It will be usable from around 500 Hz up. Maybe a little lower. A smaller horn will probably have better treble performance too. I have a pair of round 180 hz tractrix horns and even with a cone driver they are only usable to 300 hz in free space. With a compression driver 500 hz and they beam A LOT.
Here is a 200 hz expo horn with a compression driver. Look at the frequency response measurements.
Exponential Midrange 2
If you want true 200 hz performance in free space best to use a suitable cone driver. If you are going to do that than I recommend taking it down to 100 hz and lower and crossing over to a mid high horn above 500 hz.
Here is a 200 hz expo horn with a compression driver. Look at the frequency response measurements.
Exponential Midrange 2
If you want true 200 hz performance in free space best to use a suitable cone driver. If you are going to do that than I recommend taking it down to 100 hz and lower and crossing over to a mid high horn above 500 hz.
The widely considered best waveguides (other than OS) do indeed have slotted throats, e.g. the 18Sound XT1086.
On-axis dips are typical for smaller sized OS (round) waveguides, but don't apply to classic (Salmon family and similar) deeper horns, whether elliptical or not.
It's a product of the OS throat relative to the mouth size as well as the inclusion of a roundover (or not).
> 50cm mouth diameter, the on-axis dip of OS waveguides disappears.
Last edited:
That is not exactly true. The throat size has no bearing on the problem, the waveguide length does. The reason that OS exhibit such a significant hole is because the path lengths of the edge diffraction for virtually all frequencies and are the same everywhere. This means that the wave diffracted from the edge is completely coherent with the direct sound and hence its effect can be very narrow and deep - but it can also be made to go away (larger mouth radius). No other horn shape really has these same characteristics - which are required for a narrow deep hole. Squares, different profiles all change either the path lengths (cross sectional shape) or the frequencies leave the boundary at different locations (also changes the pathlength,) hence the diffracted wave is not entirely coherent with the direct wave.
That's how the axial hole comes about.
Last edited:
As I said above, an axial hole is almost unique to an OS waveguide. So axial holes in anything other than OS are not really an issue. Short round horns of any size with sharp edges may show this effect to a certain degree, but even a long OS would have it if the edges are sharp. (Found this on the very first OS that I ever made back in the early 1990s.) Any sufficiently long non-OS will likely not show an axial hole.
Gradual mouth terminations are always an improvement however - no diffraction is still better than incoherent diffraction.
PS - for those into physics, the axial hole is the identical effect as the bright spot on the dark side of a disk. If the disk is not a circle it smears out rapidly.
Last edited:
Thank you for the comprehensive explanation.
I guess I had to be more specific regarding the throat size > OS waveguides generally have smaller throats (1").
If one desires a large mouth radius, it would seem logical to increase the waveguide's length at the same time.
The larger mouth radius also increases the sheer size of the horn. I remember posting the paper on this very thread that sports measurements on several different types of horns (16 in total) and the late energy they show in those measurements, arriving after the first pulse: http://unepassionaudiophile.fr/wp-content/uploads/2018/01/Horns_measurements_ETF2010d-1.pdf
These measurements show some interesting results from these different types of horns that would seem quite valid to this discussion. If anything, you'd want to have a horn that shows one of the cleanest pulse results, or viewed in that paper as wavelets. At least I would want that if I were after a reference quality horn for studio work.
In my book that would point to a smooth driver - throat transition and a generous round-over at the mouth to get it. But there's always compromises to make, and I just wonder how far camplo is willing to go size wise to check all these boxes... At least i would think a generous roundover would make his round horn bigger than he'd like it to be?
A square, ellipse or rectangle horn would still have that energy after the pulse, but more smeared out (due to those different path lengths). So it could be one has to choose (as always) your set of compromises to get close to what you'd want.
Personally I'd pick a (slightly) higher crossover and get that generous roundover (for instance the already picked out JMLC horn), when looking for that reference quality but I can understand the quest camplo is on.
We are not after the best horn in just any room here, we moved past CD type as requirement because the room/speaker setup would be adjusted for best performance, looking for a more nearfield use than regular entertainment setups would use.
But can we create that 200-20K (or as close as possible) horn within the size constraints camplo is willing to make, keeping in mind the best possible (non CD) performance. My bet is the horn when done without compromise (for this specific task) could turn out to be larger than camplo would want it to be.
Last edited:
288B FR response 500-12,000hz with a 2.8" voice coil..... ( http://greatplainsaudio.com/wp-content/uploads/2016/06/288B_hfdriver_spec_sheet.pdf )....This driver also had the characteristic of a strong PWT spec, and with a 37" long horn, he settles on a 300hz xover....
We are working on a AXi2050 with a 5" voice-coil, that is rated to 300hz, also with an strong PWT reading. So far, we (I) are speculating that a 36" long horn on said driver might make it to 200hz.
One guy is already taking the Axi to 300hz on a 250hz horn that is shorter than the 1/2WL of 250hz, probably like 40% of the wave length (21"), measured at 3m in a room.
I don't think anyone is disagreeing with you except that I am optimistic in reaching, if not 200hz, 300hz, with better performance than what has been achieved. The free space measurement spec is the one to be respected is what it sounds like you are saying.
Last edited:
I also have an engineering background, so that makes sense to me
Some more inspiration:
Did you see the the personal web page from Bjørn Kolbrek? On it is his own system (at least up till january 2018) and the journey he made to create his own 200 Hz midrange horns (DIY).
Among other things he used a casting process for the horn throat which is described here: Exponential Midrange 2
On another note, if you do end up wanting to make round horns you might want to look into the Delta type 3D printers. They do round shapes rather good and are quite scalable.
Ooook I think POOH thought that you were suggesting a 200hz horn when this post is really about horn building ideas. OK POOH now I understand you lol!
I have seen those pages but I think I will study them again. Have you seen this?
Bjorn's Content - Page 2 - The Klipsch Audio Community
What the heck Wesayso?! Did he cast the horns throat in Tin? He melted tin and casted it on the silicon plug!?
"Delta type 3D printers" - I actually have just discovered this type and skimmed over a few....they cost more, and for hte money have way smaller tables. I'm looking at the Crealty CS-10 S4....with a 400x400x400 print, I can print from the horns entrance till the horn is 15" in diameter in one piece. I think that is a good thing. Whether I'm printing a cast or go with the shell idea to be filled with something (sand/mortar/some mystery magical pour substance I have not discovered yet)
Last edited:
Yes, I linked to that page for the casting procedure
.If you liked that Klipsch data with the Axi driver, this post might be of interest too: https://www.diyaudio.com/forums/multi-way/244508-monster-massive-29.html#post5707811
It gives you something to compare to the wavelets in the paper i posted a few posts ago
.Delta printers can be more expensive, there are a couple of huge ones that could print your horn in one go!
At work we have created a hanging printer that uses the Delta principle for the most part. Given enough room it can print huge prints hanging from the ceiling with ankers spread out in the room... fun project (done within Fusion 360)! But not a real fast printer!
If you have facebook you can view it here making it's first moves (the gears are now upgraded and it can print quite a bit faster than shown here):
Scauting - Yessss "het lab" heeft de 3D hangprinter aan...
Print size wise there are no specific limits except the room you have to spare and the length of the cables one uses
.
Last edited:
I have horns that are a meter plus long with compression drivers with large diaphragms - 6" Ec600, JBl 8" CMCD81, Community 8" M4 and 10" Adamson. The Celestion you bought may be the exception.
Good luck with your build!
