Eddie Runner wrote:

Nousaine wrote:

Eddie Runner wrote:

Tom,
if you look at my graphs http://www.installer.com/tech/aiming2.html

you will see that in the Dodge NEON there is a
27db difference at 100Hz
26db difference ar 95Hz
10db difference at 90Hz
5db difference t 75Hz


So explain how they 'smoothly' transition to equal magnitude at lower
frequencies?

Why?
You are claiming I made the whole thing up!!
Any amount of explaining just seems to fall on deaf ears.

Just look at your traces. If aligned for level (areas where the
traces have the same shape) on a light box, which always happens when
nothing
more than a level shift is involved (which IS what happens when there is NO
more acoustic energy being produced) than it's apparent that there is not
significant deviation below about 80 Hz.

The fact is one trace is significanly lower SPL than the
other trace... I know you want them to be more SPIKED
so that my theory about standing waves would be realized.

If they were standing waves, tied to wavelength/distance then they would HAVE
to be frequency related and would NOT be evenly distributed.

And your trying to say the traces (although one is lower) are
not spiked....

I see your point there Tom...

But fact remains that one trace is still lower even though there
are no spikes... That lower difference can only be cancalation!!

No; they CANNOT be 'cancellations' or they would be unevenly distributed. The
only other acoustical sound pressure losses are distance (the closer enclosure
would be louder) and absorption (how would the vehicle absorb more low
frequency energy at any given frequency in the omnidirectional range with any
given orientation?)

Those exhaust the physical/acoustical possibilities.

What's left ....??? You tellme.

One thing for sure it isn't "cancellations". If you don't want to accept that
study Baranek some more.


Since the box output is the same and the only difference is the
speaker location... It can ONLY BE cancellation, the NODE
(standing wave) is more pronounced in the listening area!

But it CAN'T be, at these frequencies, where sound is being radiated equally in
all directions. If it WERE a standing wave it would have to be
wavelength/frequency related.


Have you checked the impedance/system resonance with both locations? I've
not
found a significant difference.

No but I can do it easily... I couldnt imagine it being much different by
location alone.

But it will tell you if there's a related effect regarding system tuning. Of
course, there's not but you haven't exhausted up-stream possible causes. We
already know it's not an acoustical effect.


1) the SPL is lower with the woofer aimed forward... Can you see that on
the
chart?

And why would it be" It's closer to the microphone so IF we're not in the
pressure zone in the car why wouldn't it be LOUDER?

because of cancelations that occur....

What 'cancellations'?

2) you dont believe the chart because you think there cannot be a
difference.

It has nothing to do with my (or your) beliefs. Physics tell us that you
cannot
increase average SPL with driver orientation in an enclosed space at omni
frequencies.

my sweeps show otherwise!

And you'll say that the other laws of physical acoustics still work their
normal way? But, in this case you've superceded them?


3) I say since the woofer has not changed its output at the cone, ANY
change
in
spl must be caused by replections that cancel or reinforce the
original
sound.
(WHAT ELSE COULD IT BE???????)

It's not standing wave activity. You tell me? I have a good idea but apparently
you don't.

Some operating error on your part. Are you now telling us that average SPL
in
an enclosed space at omnidirectional frequencies is affected by source
direction? How can this be?

Not source DIRECTION but instead SOURCE LOCATION!!

Same thing at these frequencies.

4) The reflections have changed because the woofer location has changed.

But is the woofer location constantly adjusting it's location for every
frequency equally? How does it manage to do this at 21.5, 34 and 43 Hz
simultanously? These ARE reflection/standing wave effects aren't they?

I dont see how it can constantly adjust its location(?)

Of course you don't because it can't and your results are contaminated by some
non-acoustical cause.

We'll I cajoled you into actually doing measurements. Now it seems that
either
you will accept measurements that don't exactly fit with the laws of
physics or
acoustics or you won't discuss fair questions about why your results have
things about them that fit.