Resonant Freq. of Dodge Ram - help.

[avs20 10+ year member]

Ok, got a radioshack meter(I know a TL would be better, but there isnt one close to here) and played tones from 45-65hz. I tried it at 2 diff volumes.

Results w/first volume(60):

45-46hz - 111

47-48hz - 112

49-50hz - 113

51hz - 114

52-53hz - 115

54hz - 116

55-56hz - 117

57-61hz - 118

62hz - 117

After this it started dropping, so I quit writing.

Results w/second volume(50):

45-47hz - 101

48-50hz - 102

51hz - 103

52hz - 104

53-54hz - 105

55hz - 106

56-57hz - 107

58-59hz - 108

60-61 - 109

62-63 - 107

What do you guys make of the difference between the two tests?

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[the_flatlander 10+ year member]

well then 60-61 is your resonant frequency I could be wrong so don't quote me

 

[avs20 10+ year member]

Jmac..there are NO shops around here with a mic..and 60 is what I normally run/burp my system at...

 

[req 5,000+ posts]

i am also interested in finding an inexpensive way to meter\test my cars freq's and things. anyone know?

i dont know of any shops round here eaither. but i could be wrong.

 

[squeak9798 5,000+ posts]

well then 60-61 is your resonant frequency I could be wrong so don't quote me

Not necessarily.....that could have just been where his box peaks. To come close to finding the resonant freq, you'd need to perform the same test with the box in an open area (like your yard). Record the same frequencies with the meter at the same volume levels. The frequency with the greatest difference in db level (between in vehicle and out of vehicle responses) is close to the res freq.

But as Jmac mentioned, there are things that will affect the res freq; like volume level, sub placement, etc etc

 

[avs20 10+ year member]

How does the box 'peak' if it is sealed?

 

[squeak9798 5,000+ posts]

How does the box 'peak' if it is sealed?

All boxes have a peak frequency and a certain response curve.....sealed included. Sealed's frequency response isn't just a flat line.

Most ported boxes just have an exaggerated peak and/or peak to a higher SPL than sealed.

 

[Moe Lester 10+ year member]

The resonant frequency of the vehicle changes with the amount of flex in your body panels. That could be one of the reasons the meter detected the peaks slightly differently. On the other hand, that radioshack meter could just not be accurate enough.

If you were building a box, i would tune around 48-53 and burp at around 58/59

 

[avs20 10+ year member]

Ok. So if the res. freq of every vehicle changes with box placement, volume, etc..how can you even find the res. freq? Does finding the 'peak' with a meter just give you an estimate of where to start from?

This box will have a port plug...just need to find out what to tune to for burps so I can get to building it..

 

[squeak9798 5,000+ posts]

Follow this: http://www.bladeice.com/resfreq.htm

 

[Moe Lester 10+ year member]

the freq doesnt change drastically, but it does change. From your testing, and the results you got, i would say your peak is right around 59/60 hz. If you are currently using a sealed box, and burping at 60, then thats about where you wanna burp with your ported box. Build a box with changable ports, not just a plug. Make a few ports for a few diff tuning frequencies, and find out which tuning is loudest.

 

[avs20 10+ year member]

I'm not running a sealed box. Im just using it to find the res feq. I ran a ported box before tuned to 35hz. I'm going to be building a 20ft^3 box..tuned low with a port plug for daily, and tuned high for comps..