Simple H-frame / OB combo - Question

Imagine a tombstone OB sunk into an H frame such that the FR and Sub drivers share the same physical baffle. Let's say the baffle board extends upward by > 20" above the top of the H frame box.

In this case are the top two pieces - top of the front and rear parts of the H frame - needed?

Would not the baffle board extending up another 20" take care of blocking the bass wrap cancellation as well?

Is the shallow, front side of the H frame doing something that would be disrupted if the top board were removed? Perhaps get away with it on just the rear part of the structure?

Thanks for any insight you may have on this.
 

OllBoll

Member
2010-11-22 11:24 pm
Imagine a tombstone OB sunk into an H frame such that the FR and Sub drivers share the same physical baffle. Let's say the baffle board extends upward by > 20" above the top of the H frame box.

In this case are the top two pieces - top of the front and rear parts of the H frame - needed?

Would not the baffle board extending up another 20" take care of blocking the bass wrap cancellation as well?

Is the shallow, front side of the H frame doing something that would be disrupted if the top board were removed? Perhaps get away with it on just the rear part of the structure?

Thanks for any insight you may have on this.

I'm not sure I got the question correct but if I understood correctly:

1. You ask if you can instead of a H baffle have a normal flat (but bigger) baffle?

The answer is yes. A H-frame is just a normal flat baffle but folded, so we can get a "bigger" baffle given the same volume of speaker. They do have resonances though so a flat baffle measures better but takes up more space.

2. Can you skip the foldings on the top and just keep them on the bottom? Yes, it is a pretty good idea. Instead of thinking the whole baffle as a single thing just think of every driver separately and measure the distances from the middle of the driver to the edge of the baffle. Longer distance -> less cancellation but a lower dipole peak.

One thing to keep in mind though that open baffle bass moves a lot of air, so the panel will vibrate a lot. So if you want to build a H-frame I'd recommend you decouple the subwoofer baffle and the upper baffle like the LX521 does. If you instead use force cancelling setup like a W-frame or similar then you do not need to decouple as the drivers will cancel forces anyway. A folded W-frame has worse resonances than a H-frame though so needs to be crossed lower.