Side fire Passive Radiator

[zak]

Is there any reason to not "side fire" a passive radiator. I'm drawing up a compact 3-way with an 8" woofer and I'd like to use a PR but a 10" PR will not fit on the front baffle I want to use, so I was planning to side fire the PR. The PR will not have a lot of "breathing room" to the back-wave, but I'm wondering if that will really matter all that much. Also, I don't know about the PR being set at 90 degrees off the plane of the bass driver. I don't think that will matter either, but I'm just puttin' it "out there" in case someone knows a reason why I shouldn't do this.

[Wolf]

...and you'll effectively minimize the enclosure "rocking" that could have occured on the front or back position. Do not bottom-fire PR's. I believe you are go for launch.....
3-2-1,
Wolf

[djjustice]

There are many commercial designs that use a side firing system, so yes, you can do it. I would suggest that the PR be as far away from the main driver as possible; such as if you have a 2'X12''X1'
HXWXD sub chamber, and you have the active driver at the bottom, which for example goes 1' up, leaving 1' left in the upper area- instead of putting the PR right next to the active driver, you put it on the opposite side in the upper 1 foot space. The idea is that you give the back wave some time to "feel out" the space that you tuned it with so that it generally works better. If the PR is right next to it, it will get the back wave, but only at the point where it has achieved a 1 foot height fall out; the rest will fill the chamber, but, it will hit the PR after the original wave, giving you a lag in the lower HZ spectrum.
If any body has any contradictions and KNOW that I am wrong, fine, this idea just seems very feasible .

[djjustice]

Why not bottom fire? My MTX bottom fires. I guess it will not as affectively minimize cabinet rock, but it will give nice ground affects for movies. Though, the windows in my A/V room do shake erratically when I use the MTX sub, so maybe it isn't a good idea unless you have a well braced room. Heh, could I minimize the floor rattle by placing a piece of, say, marble underneath to disperse it more into the air?

[nick29498141]

Bottom fire can affect the driver's mechanical params over time. There is cone sag and deformation to worry about, and the surround can encounter all sorts of weird problems when spaced to close to the floor. Bottom fire subs can also suffer from poor sound propagation. on the one side, you have a driver spaced a few inches from a primary reflector, which changes the sound's diffusal patterens. The air is also a slightly different temrature, when the driver is so close to the ground, with the coil's venilation system (pole piece) being physically inverted. So you may want to conside that the speed of sound is 343m/s in 20* C air. if that air is 30* C, then your sub is seeing a different propagation speed, and a very different diffusal pattern. I used a Velodyne Sub with an 8" forward firing driver and a 10" down fire-PR, and was not happy with hoiw it intergrated with my mains, which have side-fire subs in them. (Def Tech Towers). There are some great down-fire designs out there, but many of them use purpose-built drivers, and are optimized to work in the adverse down-fire condtions.

This may all just be a bunch of hoopla to some, but to me, everything matters.

NK