[drphoto]

Hi all.

 I run a pair of the OB of the servo subs per side in big flat baffles. I did this, well, because they're easy to construct, and I have limited woodworking tools and skills. I'm really pleased, as I have posted, but I'm wondering would an H or W box work even better. Does the push/pull arrangement offer sonic benefits over all 4 drivers firing forward? Or is simply a way to reduce the footprint of the setup. I don't have WAF issues.

If there is no advantage, my final baffles (test mules for now) will each be a sand filled 2.5" x 2'x3' (ala Bob in St. Louis) w/ drivers mounted near the bottom center of the baffle. I'll finish 'em in black bed liner to approximate the finish on the Merlin mains.

cheers,

joe

[Danny Richie]

My thoughts on that is that when you just have a baffle only then the cancellation from one side to the other is immediate. It also offers no real loading on the drivers.

So I think you'll find that you will have more output if you use a H or W frame that is about 13" deep.

The H or W frame also makes it more rigid. This can increase output as well.

Depending on how high they play a wider baffle with more forward surface reflections will also hurt the imaging making it sounds as if it is playing from the baffle forward. I'd keep those dimensions to as small as possible.

[sfdoddsy]

The H and W baffles increase the path length from front to back, lowering the frequency where the dipole roll-off commences. Hence you will get better extension from a given width and need less EQ.

The downside is that you will get resonances with both, more so with the W baffle, that mean you will need to high pass lower than with a flat baffle.

The push/pull arrangement lowers even order distortion, and cancels out driver vibration, which is generally a good thing.

[drphoto]

Thanks for the feedback. I guess I could give the H frame a shot, even w/ my limited skills, it can't be that hard.

Ok, I assume for the push pull arrangement, the driver coils are connected in parallel, but out of phase. (plus to plus from amp to 1st driver, them jumper from 1st driver to 2nd wired plus to minus) Is this the same for the servo coils?

It'll an interesting experiment if nothing else. I'll post results, of course.

BTW Danny, when I first tried this I used a baffle barely larger than the driver. I mistakenly thought that because the drivers were designed for OB use, this would work. Needless to say, it was less than impressive. However, once I went to a 2'x3' baffle at Bob's suggestion the slam and extension are quite impressive. However, like everyone else, I always want to improve things.