could someone come up with the 15" version of it?

Wow man, thanks for the link to the box calculator! This may play into a twist I wanted to add the gig: Each of the four speakers will be driven by four separate special guitar pickups with very specific frequency bandwidths. If each of the four speaker enclosures were designed to have a high acoustical gain (or resonance?) at these four specific bandwidths, that would be the bawm!... That's like, acoustical crossover networks!... Heady stuff!

I would just design my own for reflex. WinIsd is a great resource to help design one or there is this online box calculator http://www.mh-audio.nl/ReflexBoxCalculator.asp

If you really want to go with a premade plan, you could try making a full range cab like a DM2 http://www.speakerplans.com/index.php?id=dm2. It would go higher than needed but I bet it would sound awesome for a bass cab.

Thanks, any plans here that you might suggest?

That seems like a pretty restrained range for a bass guitar. I would think a bass guitar would go lower than that. I would think you would want to get down at least to 60hz unless you are using a separate sub-bass cab too. On the top end I would try to hit at least 5K.

Personally I would go with a nice two or three way reflex box.

Does MKH-230 = MKB-230?
They look like the same plans.
Any other suggestions for a large bandwidth horn?
Any other suggestions for bass guitar speaker cabinet?
Bandwidth of bass guitar is 329.63 to 1108.73 Hz

@tamuksthe side with 77.0cm is the bottom.

its a big cabinet .which side is bottom