I'm designing a mid/kick horn for a diy venue that friends of mine run and I was wondering if anyone could give me some feedback. The design objectives are as follows:

• 100-900hz approximate usable bandwith with good emphasis in the kick register (Skram subs below and Altec 511E above) Depending on how the Skrams sound I might be able to cross over higher, like 110hz
  
• Single 15inch driver (I really like the sound of the Oberton 15L400 in another horn I built, so I'm designing around that. It has a very pleasant midrange voice and plays up to 1.5k in the 40cm exponential horn)
• Near 130dB output at 1m. The room is around 150qm and I'd like to use 1 per side
• Size is not really an issue, but two people should be able to lift it
• Approximately 90 degree horizontal coverage to match the Altec radial horn
  

How does this design look? Is the change in flare rate too abrupt? Can I expect the horizontal dispersion to be roughly the same as the angle of the exit flare?
Are there other drivers I should consider? Hornresp shows the PD153c002, for example falling off rapidly after 500hz, but AJhorn shows good HF extention like the Oberton. The Oberton has only 3.5mm Xmax, but I suspect that's part of the reason it's such a good midrange.

Thanks so much!

The mouth is 109cm x 50 cm

ha, thanks Meat Substitute, you're right. 

I'm just starting to understand the directivity feature of hornresp. It doesn't work for multiple segment horns, so I simulated an exponential horn with similar dimensions ( damn this thing is huge )

When simulated on axis, hornresp shows this massive peak around 400hz (reducing the compression ratio helps it mellow out a bit, but still there)

Ajhorn, which people say is very accurate for mid/high shows a much more reasonable on axis response...

Anyone have a hunch how this will behave in real life, with the two segments and wider horizontal dispersion? Is there any way to insure a flatter on axis response?