Flushed?

[stevem]

I have a question for the DIY enclosure builders on the forum. When you make a box, do you flush mount the drivers? If so, do you do it strictly for cosmetic reasons, or are there any audible differences with how a driver is mounted? Also, how do you rout the shape of the driver when it is not completely round, but also has four flat sides? Do you build a jig? Thanks!

[edgewound]

The only time I would flush mount the drivers would be for cosmetics, and the baffle is thick enough to sturdily mount the component....like 1" or thicker MDF...the stronger the baffle the better. I don't see the point in flush mounting the driver if a snap-on grill frame is going to be mounted anyway. If reflections are a concern, then the baffle should be covered with an absorptive material such as foam or felt, etc.

It's best to make a template for your router to hog out an irregular shape driver.

Hope this helps.... maybe others have additional insight...good luck with your project!

Edgewound

[GordonW]

It's totally a matter of the wavelength of the sound that the driver is going to be playing. Until you're getting to wavelengths where the "step" of a surface-mounted driver frame is at least 1/4 of a wavelength, it's probably not going to make any significant difference.

For most drivers, the approximate 1/4" flange thickness would correspond to a 1/4 wavelength at somewhere above 10KHz. Hence, only sounds in that range and above, would "see" the step as a signicant diffraction generator, in any significant sense of changing the polar response of the driver.

So, by this rationale (backed up by measurements I've taken), I commonly only bother to flush mount (or blend-in to the baffle otherwise, ie, with felt, foam, etc) tweeters, or any driver that's going to play above 5Khz or so (an octave below the 1/4-wavelength "critical point", for safety). It really just doesn't seem to make any significant difference, in the frequency range below that. Some may choose to be "safe rather than sorry" and flush mount midrange drivers, which is understandable, especially given shallow-slope crossovers (ie, the mid may be producing some HF energy)... but there's really no impetus to flush-mount a woofer, that won't ever play above 500 Hz.

One other consideration, as to flush-mounting drivers- in the case of tweeters and/or mids, flush mounting ONLY the higher-frequency driver CAN help to somewhat "equalize" the path length. I've seen cases where flush-mounting a tweeter, managed to smooth out the response at crossover, where the tweeter and midrange were both producing sound. Less offset equals less time delay/phase shift between the drivers at crossover...

Regards,
Gordon.

[stevem]

Thanks, guys, I do appreciate the responses. I think I 'll leave everything surface mounted. My "tweeter" horn handles from 1.2Khz on up, and really doesn't have much of an enclosure anyway.;)

[GordonW]

Yeah, flush mounting matters a whole lot less with a horn. Given their directionality (ie, less than 180 degrees), there's less of an issue with sound going out 90 degrees up/down/sideways and encountering baffle discontinuities... so, things should be just fine.

Regards,
Gordon.