Driver in deep baffle"tunnel"

[marcus1]

Hi all

I've read that a driver mounted in a 2" or thicker baffle will be "acoustically loaded in an undesirable way if the woofer is placed in a deep “tunnel”."

Does this mean that I should try and remove the mdf/wood from around the rear of the cut driver hole; i.e. shaping it like a funnel leaving scallops(?) for the driver screws to screw into?

Or is this wrong and there is minimal effects of a driver mounted in a thick baffle? The driver I'm using is a SEAS W18.

[ianpengelly]

You should try and chamfer the hole behind the driver. There is a good article on this topic on Troel's website:

chamfering driver holes

["Q"]

It would depend a lot on the driver in question as well. A tweeter would be in a mishap of a waveguide in that situation while (I'll go out on a bit of a limb here) an 18" woofer could probably care less. Also it would depend on the crossover, if you're crossing fairly low it might be negligible.

[ianpengelly]

Forgive me if I am wrong Q, but surely the Tweeter with a sealed back mounted on a thick baffle is the one that it wouldn't make much difference too (none at al in fact), whereas an 18" woofer that needs lots of air to breathe would benefit quite a lot from a chamfered hole. The maximum benefit however would come with small mid/woofers where the circumference to depth ratio is small.

["Q"]

Ah, I see now that you are speaking of the interior "tunnel". I thought you were referring to a rear mount situation. Though I still think that smaller woofers will be affected the most if only for the fact that do reach the same SPL you will need more cone travel. But then someone would have to crunch the numbers on the increase (non linear if I recall)of the restricting surface area for an ever larger circle.

Also for a midwoofer I'd think that square edge would introduce diffraction just like it does anywhere else, even worse since it comes perpendicular to the cone (ouch!).

Whether or not this is audible on the other side, I'll leave that for the guys with measurement gear to answer.