IIRC it's based off the 7e or probably the same unit just rebadged.

 

I think the 28 has the same ability of the XM-5e, it just looks purty and has the option of balanced connections.

 

 

The XM-3/3e/4, as shown, has a lowpass and two high pass.

The XM-5/5e/6 has a lowpass, a bandpass, and a highpass - as does the 28 in that photo. All the extra RCA connections on the 28 are for balanced inputs/outputs that nobody uses.

 

That was puzzling too

 

Well... back when that crossover was new, Coustic sold DR amps with balanced inputs and they sold an outboard D/A converter that had balanced outputs. This all came out about 2 years before differential inputs on amps became popular and made balanced connections more or less unnecessary.