Mega midbass straight horn 139dB

kipman725

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2007-06-10 12:41 pm
Warrington
I think I nailed this but perhaps I made some mistakes and more can be wrung out of this driver or another drive can get similar results at lower cost.

The aim is a midbass horn covering 100 - 400 Hz that can keep up with a community M200 on a clone of a K-402, or is that's a bit challenging a classic dual conical CD horn. The midbass will be the same width as the K-402 (1m) and will also be a rectangular horn. The aim is to make a 3 way full horn stack that can keep up with the M200 and has low distortion. The driver used is the Beyma 15p80fe/n as it has very low Qes and high power handling and 7.5mm xmax. I selected an exponential flare as it should provide the highest fidelity.

I used the papers of Keele to design the horn:
The throat is sized for maximum acoustic efficiency, the mouth size was selected to be optimum and the rear chamber is sized for reactance annulling at 100 Hz.
 

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freddi

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2005-08-16 4:21 pm
your horn also looks good with 10 liters back chamber + my JBL M151 bass guitar speaker (large published xmax but short overhang - so lots of compression at higher inputs)

- wonder how much it might suffer folded to reduce depth ? - the front could be ~1M x 0.61M external
 

freddi

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2005-08-16 4:21 pm
oh - my Peavey FH1 isn't far off from that spec,
just reduce its back chamber with foam blocks

CIiWiGQ.jpg
 
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kipman725

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2007-06-10 12:41 pm
Warrington
Ah interesting results on the FH1, looks like a folded horn would work to 400 Hz. I think we are going to go with a straight horn though for ultimate fidelity. I have heard void tri motion which uses a smaller 15" midbass horn with a single 90 degree bend:
Tri Motion : Air : Three-way bi-amped sculpted loudspeaker array
and was impressed with the results. The size is managable as we intend to only run it in large spaces and outdoors.

The JBL M151 does not seem very readily available in the UK unfortunatly. I'm pretty excited by the output potential of this horn so hopefully in the next few weeks I will be able to translate the Hornresp simulation into a CAD design (need to learn the software).
 

kipman725

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2007-06-10 12:41 pm
Warrington
I have calculated the profiles for the x and y contours of the horn. In the y plane the horn is a simple conical and in the x plane the horn makes up the remaining area such that the overall area is exponentially expanding to the final mouth size. The throat is a square and the final mouth is a rectangle with a width matching the k402 clone. As only one set of sides has to be curved this should make construction a lot easier.

What opinions do people have for the midrange horn on just building a standard dual slope conical horn? significant performance difference from k402 in the 400 - 3 kHz range?
 

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kipman725

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2007-06-10 12:41 pm
Warrington
Thanks to Hornresps directivity tools I have found a problem? (more on this in a bit) with the horn, the vertical pattern at the crossover frequency of 400Hz is too wide and the horizontal too narrow. We are trying to get a nominal 90x60 but have 75x134... however the k402 reportedly has a pattern of ~75x105 at the same frequency to which this is a good match. As the mouth dimensions are quite similar this makes sense (as both horns are loosing directivity) and so will probably be also the case if I go for a similarly dimensioned dual slope conic horn for the midrange.

To simulate the pattern I made new Hornresp records with identical parameters apart from changing the flare type and the mouth area such the the diameter of the mouth would be correct for the plane under study. (as Hornresp simulates a round mouth).

From these results I'm tempted to increase the vertical dimension of the mouth to obtain a better directivity match. The current midbass horn has a side wall angle of ~20 degree which is anomalous with having a 60 degree overall pattern (they should be 30 degree). However the size and weight would increase and throat impedance will have larger ripples with the only gains been small improvements in the directivity plot around 400Hz, where its already pattern flipped and becoming non directive.
 

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pelanj

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2008-07-17 8:47 am
Hořovice
Very interesting. My front midbass horns, that I needed to put aside due to the size have curved walls and flat top and bottom. They can do high SPL and relatively flat in the pass band, I used them below a JBL2380 horn up to 650 Hz and they could go higher with EQ. I am now trying to find something like half the height and at least 90% of performance:) So I am heading in the opposite direction and I actually plan to try a 12" super planar "kick-top." Thanks for sharing and I am curious how this turns up.

Edit: I actually forgot to write a point - I have also FH-1 like bass bins and they could do easily 650 Hz too. I liked the front horns better, but I think it was actually because of the looks, they measured equaly well on axis. I actually got sound improved at the listening spot when I placed the WBins on the short side. Again, no hard evidence for that, just a feeling.
 
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freddi

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2005-08-16 4:21 pm
hey pelanj - re: 1x12 super planar - that will be interesting to me. On the Karlson side of things I'm thinking of a "K12" with internal K-tube - but don't know whether to try a curved reflector and if so, what profile. FWIW, I prefer a K12 with pym1298 (~same as Kappa 12a) to my FH1. The little K sans midhorn of course has a different presentation, but is more dynamic and with better coupling to the room than my Klipschorns. Maybe no mod is needed to K12 but the port would have to be split to accommodate the K-tube. A midhorn and tweeter on top would be another option, but I've several pairs of 12CX.

Maybe Karlson's little X15 would be smoother graph-wise by making it a bit taller. A smoothing stub could be added internally. Acoustic Control's 115BK based on X15 size graphs very nice but will not mount an internal K-tube. An appropriate subwoofer added to a pair of 115BK with K-tube on top would make a nice compact system. (I'm hoping the dual slot tube can work as well or better than the asymmetric pattern K-tube)

How much range do you think your Super-Planar 1x12 might cover ? - I'm always looking for excellent sound in the midbass for percussion, and cello/bass viola. So far the Karlson stuff has been very good for their size.
 
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pelanj

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2008-07-17 8:47 am
Hořovice
This is what MMJ said about it (see attachment). Maybe there are some newer measurements, but Facebook is a hell to search for info. I think there was a Hornresp record in the Super Planar thread here.

The second attachment is the plan I will build with Beyma Liberty 8 (internal height 330 mm, 15 mm plywood). I wanted to try the super planar as an alternative to the horns as it should offer similar "dynamic" performance.

I am sorry for hijacking the thread - the Super Planar sounds as a viable alternative to large front horns, so I want to try myself.
 

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freddi

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2005-08-16 4:21 pm
I made a poor try with 2-3012LF - does the basic input look ok to you ? Its tuned too low. When I was young a 4 inch edge wound voice coil speaker was typically rated 30 watts. I've completely fried a 3 inch diameter coil in less than a minute with sine input and clipped 80 watt rated amp. A 30 watt soldering iron would be one example of 30 watts sine input.

For hi-fi use I'd look at lower q lower mass 12s - but really 0.32 qts and mmd ~66g is pretty
good for such large displacement capability (9.1mm)

jmg2F5v.png


Here's a Klipsch La Scala vs that Super Planar

oops - think that's a Kappa 15C (5 ohm) I used in the La Scala sim-
not radically different than K33E

gf8FmNG.png
 
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pelanj

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2008-07-17 8:47 am
Hořovice

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kipman725

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2007-06-10 12:41 pm
Warrington
its cool, that super planar stuff is hard to navigate on FB I wish they would use a forum. Looks like the exponential horn has is tiddly beat with 139dB max SPL over the band of interest. I have got fusion360 installed now so hopefully I can generate some some CAD files. I think it would be pretty easy to build even with a basic circular saw though; when you have a conical expansion as one of the axis. Lots of projects on the go at the moment, need to get two more subs built for the end of the month.

The one design that could be louder would be a front and back loaded horn design (with the back horn having a 180 degree bend) but that would seem very difficult to build; for one how would you even get the driver in!
 

freddi

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2005-08-16 4:21 pm
a lot of times I think for a given bulk, there can be similar predicted outcome. In the example below, getting a good size vent that doesn't compress too much for PWK's "Belle" back chamber might be a problem. Cubo Kick looks good for hit.

Maybe resonator chamber speakers do sound "different"

JACxLZZ.jpg
 

pelanj

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2008-07-17 8:47 am
Hořovice
I got some interesting results with compound horns - when they had a certain length ratio (1/3 or 1/4? or maybe 1/2...) The outputs mixed really well together. I tried only conical, evem that would be difficult to build and very large. So I went for the SP which is super easy to build. Maybe one day I will investigate these compound horns more. I was after maximum output from a single 12" above 100 Hz.