Sorry for the delay, for those interested I now have some results regarding bass
output with the windows open. First a baseline was recorded with the windows up
then several other configurations were tested for comparison. I only made a few
sweeps from 10Hz to 200Hz in each configuration. My physics teachers would be
disappointed to hear I made no calculations of standard deviation so there are
probably (small) errors in my results. Whoop dee doo. Any content below ~15Hz is
only crap getting into the mic, possibly remnants of Katrina.

Interesting points:

1. Output below 22Hz was improved by 4dB when the front windows were opened 2".
Above 22Hz output was hardly effected. I'm not entirely convinced of this and
plan to repeat tests in future.

2. Opening the front and rear windows all the way dropped the output by 10dB at
20Hz, diminishing to no effect above 39Hz.

3. Opening the trunk improved sub-sonic bass by 6dB and flattened the response,
however greater overall losses were achieved above 20Hz.

4. Opening up the car in any way lowered the tuned frequency of the subwoofer
enclosure. This is apparent in the small response peak in each curve around 20
Hz. The sealed cabin must excessively load the box.

5. Turning the enclosure to face the rear dropped the overall output slightly,
except when the front windows were cracked open 2". In this case output was
slightly improved but admittedly, it may have been the asshole with the
lawnmower.

6. Moving the enclosure to the backseat lowered the output across the board and
deepened a response hole at 64Hz to -24dB. This indicates the car's transfer
function is probably responsible for the hole.

Conclusion: Both opening the windows and moving the enclosure have definite
effects on the output response. If you're into car audio for fun you can
experiment with placement of your subs. Maybe even drive around with the trunk
open for a flatter response. If you're a competitor and have exhausted ways to
improve the tuning of your system, you may want to attempt to tune your car's
transfer function. I recommend using a 4" holesaw.

If anyone has questions or would like me to try something else feel free to send
me an email.
The measurement plots are available for viewing he
http://i8.photobucket.com/albums/a39...acingfront.gif

Kevin Murray

What kind of car was this, by the way? And do you have the graphs available
for turning the box around?


"Kevin Murray" wrote in message
...
Sorry for the delay, for those interested I now have some results
regarding bass
output with the windows open. First a baseline was recorded with the
windows up
then several other configurations were tested for comparison. I only made
a few
sweeps from 10Hz to 200Hz in each configuration. My physics teachers would
be
disappointed to hear I made no calculations of standard deviation so there
are
probably (small) errors in my results. Whoop dee doo. Any content below
~15Hz is
only crap getting into the mic, possibly remnants of Katrina.

Interesting points:

1. Output below 22Hz was improved by 4dB when the front windows were
opened 2".
Above 22Hz output was hardly effected. I'm not entirely convinced of this
and
plan to repeat tests in future.

2. Opening the front and rear windows all the way dropped the output by
10dB at
20Hz, diminishing to no effect above 39Hz.

3. Opening the trunk improved sub-sonic bass by 6dB and flattened the
response,
however greater overall losses were achieved above 20Hz.

4. Opening up the car in any way lowered the tuned frequency of the
subwoofer
enclosure. This is apparent in the small response peak in each curve
around 20
Hz. The sealed cabin must excessively load the box.

5. Turning the enclosure to face the rear dropped the overall output
slightly,
except when the front windows were cracked open 2". In this case output
was
slightly improved but admittedly, it may have been the asshole with the
lawnmower.

6. Moving the enclosure to the backseat lowered the output across the
board and
deepened a response hole at 64Hz to -24dB. This indicates the car's
transfer
function is probably responsible for the hole.

Conclusion: Both opening the windows and moving the enclosure have
definite
effects on the output response. If you're into car audio for fun you can
experiment with placement of your subs. Maybe even drive around with the
trunk
open for a flatter response. If you're a competitor and have exhausted
ways to
improve the tuning of your system, you may want to attempt to tune your
car's
transfer function. I recommend using a 4" holesaw.

If anyone has questions or would like me to try something else feel free
to send
me an email.
The measurement plots are available for viewing he
http://i8.photobucket.com/albums/a39...acingfront.gif

Kevin Murray

Asshole with the lawnmower... Thanks man, I just spent sooo much time
cleaning my keyboard and now you ruined it by making me blow beer out
my nose onto it. It's my ONLY beer tonight, my nose is killing me and
now I'm typing on a cheapo keyboard....


Soooo. Anyone use an illiminix keyboard... I'm in the market

Asshole with the lawnmower... Thanks man, I just spent sooo much time
cleaning my keyboard and now you ruined it by making me blow beer out
my nose onto it. It's my ONLY beer tonight, my nose is killing me and
now I'm typing on a cheapo keyboard....


Soooo. Anyone use an illiminix keyboard... I'm in the market

Toyota Camry four door sedan (my other car is a Ferrari). I have the graphs
for rear facing and back seat position on another computer and will post
them when I get a chance.

Kevin Murray

"MZ" wrote in message
...
What kind of car was this, by the way? And do you have the graphs
available
for turning the box around?


"Kevin Murray" wrote in message
...
Sorry for the delay, for those interested I now have some results
regarding bass
output with the windows open. First a baseline was recorded with the
windows up
then several other configurations were tested for comparison. I only made
a few
sweeps from 10Hz to 200Hz in each configuration. My physics teachers
would
be
disappointed to hear I made no calculations of standard deviation so
there
are
probably (small) errors in my results. Whoop dee doo. Any content below
~15Hz is
only crap getting into the mic, possibly remnants of Katrina.

Interesting points:

1. Output below 22Hz was improved by 4dB when the front windows were
opened 2".
Above 22Hz output was hardly effected. I'm not entirely convinced of this
and
plan to repeat tests in future.

2. Opening the front and rear windows all the way dropped the output by
10dB at
20Hz, diminishing to no effect above 39Hz.

3. Opening the trunk improved sub-sonic bass by 6dB and flattened the
response,
however greater overall losses were achieved above 20Hz.

4. Opening up the car in any way lowered the tuned frequency of the
subwoofer
enclosure. This is apparent in the small response peak in each curve
around 20
Hz. The sealed cabin must excessively load the box.

5. Turning the enclosure to face the rear dropped the overall output
slightly,
except when the front windows were cracked open 2". In this case output
was
slightly improved but admittedly, it may have been the asshole with the
lawnmower.

6. Moving the enclosure to the backseat lowered the output across the
board and
deepened a response hole at 64Hz to -24dB. This indicates the car's
transfer
function is probably responsible for the hole.

Conclusion: Both opening the windows and moving the enclosure have
definite
effects on the output response. If you're into car audio for fun you can
experiment with placement of your subs. Maybe even drive around with the
trunk
open for a flatter response. If you're a competitor and have exhausted
ways to
improve the tuning of your system, you may want to attempt to tune your
car's
transfer function. I recommend using a 4" holesaw.

If anyone has questions or would like me to try something else feel free
to send
me an email.
The measurement plots are available for viewing he
http://i8.photobucket.com/albums/a39...acingfront.gif

Kevin Murray

Sorry Chad, I owe you a beer. For what it's worth I ruined my keyboard with
coffee when I read your post.

Kevin Murray

"Chad Wahls" wrote in message
oups.com...
Asshole with the lawnmower... Thanks man, I just spent sooo much time
cleaning my keyboard and now you ruined it by making me blow beer out
my nose onto it. It's my ONLY beer tonight, my nose is killing me and
now I'm typing on a cheapo keyboard....


Soooo. Anyone use an illiminix keyboard... I'm in the market

Here are the plots I promised. The yellow trace in the previous plot relates
to the cyan trace in the second plot. I should have kept the colors the same
but I goofed. As for the lower output with the sub facing the rear, I can
only assume that the mass of the air trapped between the box and the trunk
back was added to the pistonic mass of the cone. This would tend to lower
the efficiency as the frequency increased. One thing to note, the vent was
not shrouded as it's located in the end of the box.

I made only one plot when the box was in the backseat. It was done with the
windows up and the trunk closed. Note how the response took a bigger dive at
~65Hz. I measured the length of the car's cabin front to rear and it came to
~10.8'. With a wavelength of ~17.25' (at my mach number which was adjusted
for altitude, humidity and my blood alcohol level ) this works out to about
one and a half wavelengths. No surprise really.

http://i8.photobucket.com/albums/a39...facingrear.gif
http://i8.photobucket.com/albums/a39...acingfront.gif

Kevin Murray

"MZ" wrote in message
...
What kind of car was this, by the way? And do you have the graphs
available
for turning the box around?