Need help on windows & Bass
You problem has to do with cancellation. When a subwoofer is in a car it puts out a direct wave and a reflected wave. If these two waves are out of phase they create cancellation. The best way to prevent cancellation is by firing the sub backwards.
Read the following article for more details:
http://www.installer.com/tech/aiming.html
Read the following article for more details:
http://www.installer.com/tech/aiming.html
1000 Watt CAFz'r
Joined: Oct 2003
Posts: 1,783
Okie dokie.
Pressure is the answer.
Think of this as a 6th order bandpass box...with a large front chamber. While at low volumes, the front chamber (your car interior) does not restrict the movement of the cone, at high volumes it does. Artificially increase the size of the front chamber, and at higher volumes there is less restriction on the cone.
Open your windows too much, and the pressure loading that the car introduces is lost. Your cracked windows are kind of like ports.
Make sense?
Adam
Pressure is the answer.
Think of this as a 6th order bandpass box...with a large front chamber. While at low volumes, the front chamber (your car interior) does not restrict the movement of the cone, at high volumes it does. Artificially increase the size of the front chamber, and at higher volumes there is less restriction on the cone.
Open your windows too much, and the pressure loading that the car introduces is lost. Your cracked windows are kind of like ports.
Make sense?
Adam
Originally posted by PEI330Ci:
Pressure is the answer.
Pressure is the answer.
[ September 26, 2005, 10:51 PM: Message edited by: Luckyman ]
Guest
Posts: n/a
^ Your suggestion is that his single 13W7 is actually pressurizing the car to the point that its movement is being restricted?
That would be impressive.
I would suggest a woofer relocation, redirection, or re-tuning. All of which are gonna suck in the tiny hatch of a 300zx.
That would be impressive.
I would suggest a woofer relocation, redirection, or re-tuning. All of which are gonna suck in the tiny hatch of a 300zx.
seems there are some heavy hitters chipping in...
keep it coming.
i can't see the pressure being that high inside the cabin although its pretty well sealed. there's got to be more to it...
keep it coming.
i can't see the pressure being that high inside the cabin although its pretty well sealed. there's got to be more to it...
If you can hear the subwoofer then you know for sure that it's pressurizing the cabin. The existence of sound equals the existence of pressure. The cancellation that I'm talking about doesn't necessarily require high levels of pressure. It can also happen at low volumes.
The reason your bass is louder when you open the windows is because your creating resonance. If you were to measure the frequency curve of this bass you would find that it has a peak. This peak is the natural resonant frequency of your car. Everything has a natural resonant frequency. When you close the window your car no longer acts like a tuned instrument. Instead it becomes like a muted trumpet.
Another example is when you blow across the top of a bottle and it creates a nice musical sound. This happens because you found the resonant frequency. If you blow too fast you lose the resonance. If you put some cotton in the bottle you also lose the resonance. The resonance doesn't actually disappear but rather it shifts to a different frequency so that you have to blow on the bottle differently in order to hear a sound. This is what happens in your car when you close the windows.
I still think the best solution is too change the direction of your box.
The reason your bass is louder when you open the windows is because your creating resonance. If you were to measure the frequency curve of this bass you would find that it has a peak. This peak is the natural resonant frequency of your car. Everything has a natural resonant frequency. When you close the window your car no longer acts like a tuned instrument. Instead it becomes like a muted trumpet.
Another example is when you blow across the top of a bottle and it creates a nice musical sound. This happens because you found the resonant frequency. If you blow too fast you lose the resonance. If you put some cotton in the bottle you also lose the resonance. The resonance doesn't actually disappear but rather it shifts to a different frequency so that you have to blow on the bottle differently in order to hear a sound. This is what happens in your car when you close the windows.
I still think the best solution is too change the direction of your box.
luckyman,
the majority of my car is dampened heavily from factory (not wimpy dampening either... some heavy duty stuff). on top i have a couple layers of brown bread doing some extra duties. the result has been a much lower resonant frequency than normally expected. given that the effect is there regardless if its a 60hz note playing or a 30 hz note playing (both an octave apart and i would expect them to have greatly different effects on the car's surfaces at their resonant frequency) i find it hard to accept the result being the same as you describe. besides, changing the location of the box would not affect the resonant frequency of the car thus not eliminate the effect if its indeed due to resonance...
Dukk, i may be able to angle the speaker differently with some fiberglass work...that would be a project for a boring day though..
any more input guys?
thanks alot for every one's contribution
the majority of my car is dampened heavily from factory (not wimpy dampening either... some heavy duty stuff). on top i have a couple layers of brown bread doing some extra duties. the result has been a much lower resonant frequency than normally expected. given that the effect is there regardless if its a 60hz note playing or a 30 hz note playing (both an octave apart and i would expect them to have greatly different effects on the car's surfaces at their resonant frequency) i find it hard to accept the result being the same as you describe. besides, changing the location of the box would not affect the resonant frequency of the car thus not eliminate the effect if its indeed due to resonance...
Dukk, i may be able to angle the speaker differently with some fiberglass work...that would be a project for a boring day though..
any more input guys?
thanks alot for every one's contribution
