Time Alignment Dilemna

[the apprentice]

Hi All,

I'm currently playing around with some horn hybrids using a 15" JBL in a 4 cuft. vented enclosure and compression mid on the end of a TH-4001 clone.

Listening tests have shown the enormous benefits of time aligning the compression driver and bass voice coil - particularly with regards to image depth and layering. The problem is the old one of the horn sticking 15" forward of the bass cabinet with all the attendent reflections. The situation is the same for the 2405 tweeter.

Now I know many will recommend DSP based crossover systems but they are out of the equation as this is a strictly analogue based set up. I was just sat here wondering if anyone on the forum had come up with an aestetically acceptable solution for this age old problem? Any ideas?

[Robh3606]

Is the horn really that deep?? Doesn't it mount to the baffle with the lips protruding?? Do you have them running now?? How do they sound??

Rob

[the apprentice]

Hi Rob,

yes they are 18" front to rear. You look at the pictures of the likes of the TAD 2404 and 2402 and indeed they do just attach them to the cabinet front. It kind of works but the imaging and coherence is so much better when properly aligning the units, particularly when using a tweeter above the horn, which the designs I mention above do not.

Cessaro here have a neat solution when there tractrix pivots and is held by a chain at the rear of the drive unit - I'm loathe to copy their solution though, and it might look a little OTT with a large wide dispersion device sticking out.

[inertial]

Hi,
maybe you can choice a transient-perfect crossover type that require a "delayed" tweeter, but I'm not sure if compression drivers can manage
such "soft" high-pass.

regards,
Inertial

[Robh3606]

Have you looked into horn loading the 15?? The Edgar Horns use a short straight horn that loads down to about 70hz?? or so. That might get you a good deal of the depth you want but will certainly complicate things as fars as a sub and the suitability of your current 15 in that application. If I remember he offers kits/plans for those so inclined. Luckilly the 2405 is very directional in the vertical axis so you could drop it back and not have to worry about reflection in that axis.

Rob