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Mega midbass straight horn 139dB
Mega midbass straight horn 139dB
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Old 3rd February 2020, 10:07 PM   #1
kipman725 is online now kipman725  United Kingdom
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Default Mega midbass straight horn 139dB

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.
Attached Files
File Type: pdf MidBasBeyema.pdf (345.8 KB, 123 views)
File Type: txt BeymaMidBass.txt (75.6 KB, 30 views)
File Type: pdf M200.PDF (80.7 KB, 69 views)
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Old 3rd February 2020, 10:47 PM   #2
freddi is offline freddi  United States
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Mega midbass straight horn 139dB
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
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Old 3rd February 2020, 11:26 PM   #3
freddi is offline freddi  United States
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Mega midbass straight horn 139dB
oh - my Peavey FH1 isn't far off from that spec,
just reduce its back chamber with foam blocks

Click the image to open in full size.

Last edited by freddi; 3rd February 2020 at 11:28 PM.
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Old 4th February 2020, 12:57 PM   #4
kipman725 is online now kipman725  United Kingdom
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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).
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Old 5th February 2020, 09:06 AM   #5
kipman725 is online now kipman725  United Kingdom
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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?
Attached Images
File Type: png 100HzBassHornProfiles.png (31.3 KB, 423 views)
Attached Files
File Type: zip SquareToRectHorn.ods.zip (35.7 KB, 1 views)
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Old 6th February 2020, 02:01 PM   #6
kipman725 is online now kipman725  United Kingdom
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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.
Attached Images
File Type: png H_beamwidth_k402.png (880.5 KB, 402 views)
File Type: png V_beamwidth_k402.png (877.2 KB, 390 views)
File Type: png H_beamwidth_0.png (13.7 KB, 388 views)
File Type: png V_beamwidth_0.png (11.9 KB, 18 views)
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Old 6th February 2020, 02:31 PM   #7
pelanj is offline pelanj  Czech Republic
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Mega midbass straight horn 139dB
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.

Last edited by pelanj; 6th February 2020 at 02:34 PM.
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Old 6th February 2020, 02:49 PM   #8
kipman725 is online now kipman725  United Kingdom
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for sure looks are very important in PA (people listen with their eyes). This whole system should look very serious with skeletal horns and no boxes. If it was for home use I would defiantly fold or bend the horn to save space.
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Old 6th February 2020, 06:25 PM   #9
freddi is offline freddi  United States
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Mega midbass straight horn 139dB
hi pelanj - are you going for a single 12 planar ? - or a double 12?

https://i.imgur.com/Z2rFvjP.png

hi kipman725 - yeah, a straight horn would be better looking
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Old 6th February 2020, 06:50 PM   #10
pelanj is offline pelanj  Czech Republic
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Mega midbass straight horn 139dB
Freddi, it will be a flatter higher tuned 1x12. When I have it finished, I will post a separate thread.
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