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#1
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Bass test results [was:"No bass when windows are up"]
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 |
#2
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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 |
#3
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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 |
#4
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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 |
#5
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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 |
#6
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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 |
#7
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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? |
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