IIRC it's recommended to face the subs backwards for a few reasons. Prompted me to do some digging
found DriverGuru's reply (last in thread) to be pretty good info
https://arstechnica.com/civis/viewtopic.php?f=6&t=676198
I'm pretty sure that with a single speaker you don't need to worry about phase changes though as nothing else is putting out anything out of phase on the same frequency. Going off guru's post, the only thing it'd come into play with is reflection, and for that it apparently doesn't matter which way it's facing really vs position inside the car
Tbf, with my setup I did try switching the direction and couldn't hear any difference beyond what I'd put down to placebo so *shrug* can't hear it over the sound of my car being rattled apart by the sub anyway
Bit of misinformation here actually.
First to phase, in my particular situation I had to search for over 3 hours to find the actual proper wiring diagram for my car radio as the original connectors were cut and taped. I have a Mach 360 audio system, and 98, 99, 2000, and 2001 ALL have different wiring setups. The system has 2 stock amps, and a tweeter low pass filter setup for the fronts to not blow them as the front speakers are setup like a component system. There are 4 possibilities of reversed polarity which will cause most bass to cancel out which is the situation in my car. There's no way of me fixing this until I get a 4 channel camp and wiring all 4 speakers independently to make absolutely certain all speakers are in phase including the sub. Reversing phase on the amp will put the sub in phase with the out of phase speakers but not damage the sub since it's not "pumping" backwards. Here's a good article from MTX on it.
https://www.mtx.com/library-phase-discussion
The compression and rarefication waves for the low bass tones radiate roughly equally in all directions from the sub. The direction the sub faces doesn't matter, as far as its intended output is concerned.
This is partially untrue. Lower frequencies tend to not matter which is why in a home theater setup a sub can be facing any direction in any part of the room. Lower mids on the other hand with the "kick" or "pump" are actually pretty directional in relation to the way the speaker itself is facing. In a low wattage/small speaker scenario that definitely is not tuned to the car it can make all the difference. Remember me saying my sub is meant for inside the cabin and under a seat? It's meant to face upwards under a truck bench seat so you get all the bass personally. I figured I could compensate this by just cranking it. Which almost works, except the out of phase situation. When I'll be (ugh) pushing 500W RMS it won't matter at all.
Many subs also emit significant levels of distortion products -- multiples of the freqs they're supposed to be reproducing -- and these ARE directional. Facing the sub away from you causes them to be less apparent.
He kinda correct himself here. This is why I mentioned before "low distortion".
> I've also heard that the majority of speakers are designed to give
> a higher level of bass output from the rear of the speaker instead
> of the front....
This really isn't possible.
In fact, subs designed for reverse polarity in a situation like pictured in the MTX enclosure are. It's very possible. Pro audio Cerwin Vegas are a prime example of this and why a lot of people think they "suck". They're just not using them properly.
> ... because they are usually mounted in boxes, and you want the
> box to resonate the bass hit for a more powerful effect. So I
> guess turning them around would help.
"Resonating the bass hit" is not what you are after unless you want a lot of bass at just about one frequency, but anyway... are you talking about the practice of mounting the drivers "upside down" on the box, so that the spider and cone are extending out from the box instead of being recessed into it? That does make room for a few more cubic inches of box volume. If this allows the box to reach the CORRECT volume (which is not necessarly larger) that's fine, but the same effect can be achieved by making the box overall a bit larger.
Of course, like almost everything else in car audio, this technically valid point has been taken over by the industrial design folks. The vast majority of bass drivers that you see mounted "upside down" these days are done that way just because someone decided it looked cool. Odds are no one ever looked up the T-S parameters of the drivers, let alone designed the box volume to complement them.
I'm going to assume that this was overall correct when the post was posted in 2003. I didn't start getting into car audio until around 2009 and intentionally designed reverse mount setups were a thing then.
Then again, I have a feeling the guy didn't word his post correctly so the answer was also directed incorrectly. I have a feeling the guy was talking about volume. That's a different subject altogether.
The bottom line from what I can take from the post in general is something that needed to be said overall. Subwoofers are all about pushing AIR and manipulating frequencies. Subwoofer design, power, and a properly designed enclosure to tune for what you want are way more important than a lot of things and most people don't realize this. You buy an el cheapo box that somebody slapped together in a shop with no proper engineering to it you can starve the sub of air and it won't push air. I had a ****ty box made to fit in a small trunk but for an 18" speaker. The speaker could do 1800W RMS from 10hz to 500hz allllll day long. The box starved it and it sucked. Properly ported and tuned box for a pair of 15" 600W speakers and that **** hit harder than most setups I ever encountered with a particularly **** 1000W Sony Xplod amp. It rattled off a mirror, 2 bolts for the AC compressor, slowly pushed out the rear lamps, and eventually I had to start loctite all the bolts coming off. Mind you these were pro audio speakers designed for arena subwoofer purpose. They didn't have the low rumble like a fat foam rolled car sub but the punch was INCREDIBLE. Turned up it would almost hurt your chest in the car.
So in my situation of that tiny sub, starved for air, low RMS power, out of phase. Yea it's gonna be ****. It's intentionally made for small locations and a more localized experience. Not 6ftish away facing the opposite direction, and definitely not enough to overcome an out of phase situation. It does decently now but still not what I want.