Figure this out - Car On = Lower SPL
500 Watt CAFz'r
Joined: Jan 2008
Posts: 537
it's because the alternator in a crx doesn't put out power unless there is a load on it. This is why yulis is less loud with the car on and why my crx lost 0.5db between the pits and the lanes at finals. You need to turn the lights on in order to get a load so it charges
I'm leaning towards turboeyore's theory with the vents. I did a little test a few years ago where I did spectrum sweeps of my car with the windows up vs down. The region below ~60Hz was 10dB higher with the windows cracked a few inches. This was with a ported box in the trunk. It's also why some people experience "better" bass with their trunk open. The sub is basically a box playing inside a box. The car cabin loads the woofer and detunes the enclosure.
Yuli try this out and maybe we'll have more clues:
- key to acc., engine off, windows up
- key to acc., engine off, windows cracked a bit
- key to ON, fan on medium, engine off, windows up
- key to ON, fan on medium, engine off, windows cracked a bit
ok this may be far fetched but yuli try this, when you're "burping" with the car off open the door. check the amp draw. the loss of pressure letting the sub's move more freely and uncontrolled would make the amp draw more maybe? so what i'm thinking is with the car off all the outside vents are closed, when you start the car the vacuum motor is opening the vent door in the heater box letting out pressure when the car is running. i hope it's that easy.
True but it doesn't explain why Yulis car is louder with the engine off. It just explains why it isn't louder when it's on.
I'm leaning towards turboeyore's theory with the vents. I did a little test a few years ago where I did spectrum sweeps of my car with the windows up vs down. The region below ~60Hz was 10dB higher with the windows cracked a few inches. This was with a ported box in the trunk. It's also why some people experience "better" bass with their trunk open. The sub is basically a box playing inside a box. The car cabin loads the woofer and detunes the enclosure.
Yuli try this out and maybe we'll have more clues:
I'm leaning towards turboeyore's theory with the vents. I did a little test a few years ago where I did spectrum sweeps of my car with the windows up vs down. The region below ~60Hz was 10dB higher with the windows cracked a few inches. This was with a ported box in the trunk. It's also why some people experience "better" bass with their trunk open. The sub is basically a box playing inside a box. The car cabin loads the woofer and detunes the enclosure.
Yuli try this out and maybe we'll have more clues:
- key to acc., engine off, windows up
- key to acc., engine off, windows cracked a bit
- key to ON, fan on medium, engine off, windows up
- key to ON, fan on medium, engine off, windows cracked a bit
my car, and pretty much every single car i tested with, is louder with the vents open.
in the crx, you can open the vent manually, regardless of the car being on or off. mine is always open, it is always louder with it open. every car i've touched for street was louder with the vent and blower open.
in the crx, you can open the vent manually, regardless of the car being on or off. mine is always open, it is always louder with it open. every car i've touched for street was louder with the vent and blower open.
50 Watt CAFz'r
Joined: Feb 2008
Posts: 163
I think I know the answer.
It has been many years since I have done the "DB Drag racing" program but the one thing I always noticed is that right before anyone "burped" their car, the meter would read "zero".
Now wouldn't a running car read 40-50 db? So I would assume the SPL meter is "zeroed out" right before the burp, but while the car is running. That would mean the over all increase from a non-running vehicle vs a runnig vehicle would be greater.
It has been many years since I have done the "DB Drag racing" program but the one thing I always noticed is that right before anyone "burped" their car, the meter would read "zero".
Now wouldn't a running car read 40-50 db? So I would assume the SPL meter is "zeroed out" right before the burp, but while the car is running. That would mean the over all increase from a non-running vehicle vs a runnig vehicle would be greater.
500 Watt CAFz'r
Joined: Jan 2008
Posts: 537
Damn, missed this post. Shouldn't skip to the end.
You have the vents angle covered too so my post was useless. At least I got a "sir".
Some questions: How long do you let the battery recover from starting? What is the max output rating of the alt (ie: is it a high output unit)? What rpm is the engine doing while burping?
You have the vents angle covered too so my post was useless. At least I got a "sir".Some questions: How long do you let the battery recover from starting? What is the max output rating of the alt (ie: is it a high output unit)? What rpm is the engine doing while burping?
I think I know the answer.
It has been many years since I have done the "DB Drag racing" program but the one thing I always noticed is that right before anyone "burped" their car, the meter would read "zero".
Now wouldn't a running car read 40-50 db? So I would assume the SPL meter is "zeroed out" right before the burp, but while the car is running. That would mean the over all increase from a non-running vehicle vs a runnig vehicle would be greater.
It has been many years since I have done the "DB Drag racing" program but the one thing I always noticed is that right before anyone "burped" their car, the meter would read "zero".
Now wouldn't a running car read 40-50 db? So I would assume the SPL meter is "zeroed out" right before the burp, but while the car is running. That would mean the over all increase from a non-running vehicle vs a runnig vehicle would be greater.
I believe the meter doesn't usually register until 120dB (or lower/higher depending on whatever the minimum reading is set as).
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