Dozens of people get abducted by Aliens everyday too. Many people have
seen
BigFoot. Many people believe that hot water freezes faster than cold
water. So
what?

So, we've seen evidence of at least one of these things, what does that have
to do with this topic? lol

In my explanation I define low bass as 10-62 Hz. The subwoofer region.
Some
will consider anything up to 200 Hz as bass. That's fine with me as long
as you
specify the frequencies of interest.

I think the majority of people define bass from 120hz and below (some would
probably consider 200hz and down though, as you mentioned).

Also your SPL readings mentioned are pretty much frequency independent. A
wide-open Sound Level Meter reading could simply be encompassing any
frequencies; they are not frequency specific unless the excitation
stimulus is.
For example when I test maximum SPL of a woofer system in the car I use a
6.5-cycle ramped sine burst at 1/3 octave preferred frequencies and
measure
both distortion and SPL at those specific frequencies.

When I test SPL I typically test using a single tone, and repeat the same
tone at the same volume (MAX) for each test, so as not to have anything else
taint the results. I build and compete in SPL competitions, and we have
definitely seen increases by moving the enclosures around, but have no
reason to sit and document every aspect of it (until now, but of course
things have died in Arizona, so I have not been working on anything in quite
some time). One of these days I might break out one of my vehicles and do a
couple of controlled tests just to satisfy you though, but by the time I get
around to it this thread will probably be long forgotten. It doesn't really
matter though since 99% of those responding have stated that they DID, and
DO notice a difference when flipping the box around, and that is ALL that
matters really, to them, and to myself. If there is a perceived increase,
and the sound is more enjoyable to them, that's all that matters. Whether
you think it is true or not, it is a FACT that it happens.

If you want to use examples, I can also use the example of my 86.5 nissan
with solid side shell, walk-through, with 2 18's in it. With subs halfway
back in the bed firing forward it ROCKED, but I noticed an increase simply
by moving the subs further back in the bed. If I had them turned around
facing the rear, but centered in the bed, it would TWANG a bit more on the
outside (tailgate would vibrate) but still had a lot of output. If I slid
the enclosure back, it got louder (or at least it appeared to, but of course
we never metered it, this was back in the late 80's early 90's and I never
cared about metering anything). If we had the enclosure up near the front of
the bed, with the subs firing forward, it sounded ok, and hit pretty good,
but not as much as with the subs firing back, but enclosure in the same
position (front of bed). It was just one of those strange things that
happens.

We also had an 89 Prelude with a bandpass enclosure, firing forward into the
seat, and it didn't sound nearly as loud, or as good as when the port fired
to the rear, or towards any corner.

We took a customers 91 cutlass supreme that had an enclosure with 2 12's
firing into the back seat, and flipped the enclosure around and he noticed
an increase in the bass output as well. We did NOT tell the customer we were
changing anything, but he ASKED what we did because it sounded louder to
him. I told him I was just screwing around with his system and flipped the
box around to see how it'd sound. His trunk flexed a lot more, so we ended
up having to dynamat the hell out of it, but he was much more happy with the
enclosure that way, and refused to switch it back (I wanted to because it
sounded like ass outside the vehicle with it that way).

My dads olds cutlass supreme with 2 Boston Pro 10's running off an RF 200ix
sounded pretty good with subs firing forward into the rear seat area, and ok
with them firing up, but when we rotated the box so it fired towards the
back it increased the output greatly, and he noticed it, because he asked me
to change whatever it was I did because it was then TOO MUCH for his tastes.
Didn't change anything else except rotate the enclosure.

Trust me, it happens, but you are so caught up in only performing tests and
looking at meters, and #'s, that you can't, or WON'T see what goes on in the
REAL WORLD of installation. Your tests show that there is a difference, in
your car, albeit a small amount, but that is not representative of ALL
vehicles, or all listening choices. Everyone is different, and a mic cannot
pick up differences that the human BODY can (trust me, it's not all in the
SOUND here, it's in the FEEL as well with most people). Have you not ever
had a system that tickled your ears with it setup one way, but you change
the position of the box and it now hurt your chest or you felt it in your
stomach more than in your ears? I know I have, and I bet 100's of others in
this newsgroup have too.