Need some info on peaking and bass louder when windows down

[CJ18]

I dont think a meter is a fair example for this question though. Every vehicle is different, my truck and most truck with small cabin space are just the same as yours. Mine sound like absolute ass with the windows up, but meters well sealed up. Good thing I dont listen to test tones. All of the no wall suv and vans I have built have been different, did great windows up and down.

[Smoove]

It's sounds louder with windows down because there is less air pressure on the front side of the subs so there is more excursion. Think of your vehicle like a huge 4th order enclouse with the car being the sealed part of the box. or maybe i am wrong/.

Thats basically the way I have always understood it. It's a box in a box and both need room breathe.

[Twostrokeking]

I'll throw this in also haha. How do I know if the box is tuned to high or to low?

[Jessica]

Here is one for you. Metering on the windshield, does windshield flex affect spl readings and possibly give inaccurate results? Like when the sensor is moving at the same freq. as the tone being played.

[bobobass]

I assume the reason it's louder with the windows down is because you are taking away pressure which allows the sub to move more. In my car, I have notices that my sub moves a whole lot more with a door open than closed.

[AMI CUSTOMS]

Here is one for you. Metering on the windshield, does windshield flex affect spl readings and possibly give inaccurate results? Like when the sensor is moving at the same freq. as the tone being played.

I have tested this, just hold the meter close to glass and answer is no is doesn't affect a TL.

[AMI CUSTOMS]

I'll throw this in also haha. How do I know if the box is tuned to high or to low?

Called hours of testing and rebuilding lol

[AMI CUSTOMS]

So I see people using WinSD or something like that and they are seeing a graph of some sort?

It is a frequency response graph to show you at what frequencies the box will add "gain" to the output. Also show your f3 down point where you lose twice the output or 3db.

peak or something like that?

Something like that

what does that all mean?

See above

and why is my bass louder with the windows down?

Could be a few things going on, but generally means you are causing the sub to have more xmax this increasing output and making it louder.

with the windows up it sounds dry and not as loud. How can I fix it? why does it do that?

A few things that come to mind, wrong tuning, wrong air space, wrong port area, clipping vs non clipping, and change box perimeters and cabin gain when windows down so you can change rise in the box this making more power.

In the quote I hit on all of them

[V8SRSLO]

If you meter it and it is considerably louder center shield with the window down it is a good sign your under powered and dont have the power to move the cone with the window up. That has been my experience anyway

[SQMonte]

Sounds like you're experiencing cancellation. When a sub fires, it sends out a front and rear sound wave, if those two arent in sync with one another due to acoustics of the vehicle and placement of the subs then one wave can cancel out the other and it'll sound like yours does with the windows up. Roll the windows down though and it will decrease the deflection of the sound wave that's cancelling out the other, making it sound alot cleaner and louder. Trunk cars experience this pretty commonly. Especially when subs are firing to the rear and the box is as close to the back seats as possible.....simply moving the box so its just a few inches from the back bumper usually works wonders.