Eddie Runner wrote:

Nousaine 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

Are you blind? Or just stupid? In the Neon the sound pressure distribution
is
equally 'different" at all frequencies below 100 Hz. So exactly ''how" does
that woofer system have 'reflections' that cancel equally at every
frequency?

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

And IF the woofer IS NOT producing more SPL and IF there are not any wavelength
dependent 'cancellations' (which should be be obvious like the 100+ Hz 'notch')
then there cannot be a general improvement in SPL. Reflection/cancellation
artifacts which are independent of wavelength just don't occur acoustically in
air equally at ALL frequencies in a given bandwidth at omnidirectional
frequencies.

Anechoically of course there will be a 6-dB loss with every doubling of
distance. But this situation is in a bounded but leaky space. So IF there were
a distance effect the woofer closer to the listener would have a slight
advantage. NOT the one farther away.

Now there may be some system tuning advantage to close-boundary driver-face
placement, especially in larger spaces but I've not seen that to make any
significant difference in cars because, for the most part the cabin-transfer
function already provides the advantage.

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

For everyone else. If you measure a woofer low passed at 60 Hz in a anechoic
space you'll find that the SPL will measure equally at any given distance in
any direction; (front/back/left/right/up/down.)

Now introduce a boundary (floor, for example) and you'll get an apparent
reinforcement because the sound pressure that was formerly just disspating off
as a propagtaing wave will be retained. Add another boundary and you get some
more SPL back. Add 6 boundaries, such as an enclosed space like your living
room or your car or a phone booth, for that matter, and you'll retain most of
the SPL (some will be absorbed by the walls or surface of the enclosure and
some will escape through leaks) but you'll also cause uneven sound pressure
because standing waves will develop between every 2 sets of opposing surfaces
(there will also be other less strong effects between multiple wall surface
reflections) at wavelengths related to the boundary distances.

Below the 1/2 wavelength distance of the longest ecnlosure dimension the
displacement of the driver/port output just pressurizes the entire space.

Standing waves occur at every frequency between opposing walls; play a 1 kHz
tone in your car or your listening room and you can hear the sound change when
you move your head. But, because the wavelength is about 1 foot you get exactly
the same effect every where you sit in the room.

At 100 Hz you'll get a change in sound pressure that changes over a much larger
area. But if the room is much smaller (like closed back headphones) there is no
change in SPL with head position no matter what frequency you play.

Your listening room and your car fall in-between. In your listening room the
standing wave region generally falls between 30 and 300 Hz. In your car it's
shifted an octave upward (60-600 Hz.)

This means 2 things. First you get the pressure effect (12 dB reinforcement as
frequency falls from about 30Hz in a typical listening room; and 60Hz in a
smaller car); below this frequency there ARE no standing wave cancellation
effects because the wavelengths are quite long compared the ineterior
dimensions.

Second; because the wavelengths involved are large compared to the radiating
area of the source (woofer displacement) the sound is radiating equally in all
directions and orientation is irrelevant (at the frequencies of interest.)


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?



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.

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???????)


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?



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?



5) Since you dont believe any of this that explains why you kept on and on
about
the woofer knowing when to turn itself up..?? Pretty funny....

6) Im just sharing some graphs, you dont believe they are real, you even
question

my integrity as to creating the graphs fraudulently... I even posted
names of

witnesses to the tests...

7) I cant prove it to you unless you come on down here or you do your own
tests.
you have been in audio for a long time, you cant teach an old dog new
tricks
unless they wanna learn... If you would rather believe I made the
graphs in
photoshop I dont see any amount of argueing with you that can change
your
mind if you wont listen....

Oh I'm listening.



8) I have invited anyone that wants to show up to stop by and witness the
tests.

9) everytime I post something relevant, you hold your hands on your ears and
sing very loudly " LA LA LA LA LA LA LA LA LA LA LA LA"

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.