To find your cars res. freq... You make a sealed box and find where it peaks at right?

But wouldn't the peak be different from box to box?

Say I have a 2³ sealed box with 1 12" sittin' in the trunk and it peaked at 47Hz.

Wouldn't the res. freq. be totally different if I built a wall (12³) with an 18" and covered up the port?

When trying to find your res. freq., are there other factors involved which could change the peak such as position or even presents of the seats?

 

hehehehe..thats the fun part..everytime you make changes to the structual integrity of the vehicle you change the resonant frequency of the vehicle..even if it is just removing the seats...seats add weight in return change the resonance of the floor and later the flow of waves in the vehicle...building a wall will change waveklengths inside the vehicle and also add weight which..ofcourse will change the resonence... by now you get the picture...
best way is to use a sealed box..find the frequency response of that box at 1 meter distance away from the mic...then find the frequency response of the vehicle with the mic in the SPL metering position...take your two response results and graph them against each other..this will show you gains and losses in your vehicle...you will see a several frequencies that peak inside of your vehicle...(this is actually called the transfer function of your vehicle) take the one that has the highest positive gain and thats what you want to tune your box to...if using a box design program there should be some type of ROOM or CABIN GAIN section...where you can input your results from your test at all the frequencies tested

 

Man, this question always comes up.

Do you have any idea how much easier it is to just build a decent box that you will use and leave the ports long? Test it liek that, find your peak, adjust ports accordingly.

I wouldn't even waste the wood on a sealed box... your test results will not really be very useful.

 

^ how could test results not be useful?? ever tried it ?

 

interesting enough I've tried both methods and got similar result.

i personally find the second option easier, just make two ported boxes, one bigger and one smaller and test with both by adjusting the port.

 

Also, you have to test at a fairly high volume!!!
You will not get the results you are looking for unless the vehicle is flexing like it would under a full burp.
It could vary by 1-5hz without doing this!!

 

what Lee said

 

Test at 2 to 3 volumes and with min power and max power to correctly find your note.

 

the other major thing is to control the variables. same power, same signal , same everyhting and just change one thing at a time. that way , you truly know if somthing is working. you cannot have acurate results if you do a plethora of changes each time. you will take a good bit of time, but you will see results that are more acurate.

the car running and not also changes the voltages, so you need to control all aspects of voltages to know if a certial hz is actually making a change. good luck

 

Don't you want to tune the box ~10 Hz lower than your res frequency?