Cabin gain/calculate?

[DBBOOM 10+ year member]

Anyone got a formula/method for figuring db gain and frequency tuning to predict effects of cabin on a tuned enclosure? I know they vary according to cu. ft, but wondering if there was a simulation program or something to play with box tuning to maximize this effect.

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[simpsonbuck 10+ year member]

Every car is different and you will just have to adjust it by ear.....imo...

 

[DBBOOM 10+ year member]

Every car is different and you will just have to adjust it by ear.....imo...

I agree, but im sure someone has a way to get an estimated peak freq. and db gain.

 

[DBBOOM 10+ year member]

wow, thought for sure someone would have an answer.

 

[LDW3RD 10+ year member]

I forget were I read this(maybe in Carstereo review) but I believe it went something like this...

I believe your are going to need a RTA so you can measure the db's of the frequencies that you choose.

Take a open air(outside the car) measurement of your sub at a given frequency, I believe the mic should be 3ft away from the sub.

And then take a measurement in the car at the same frequencies that you measured in open air again with the mic 3ft away.

And I believe the gain achieved in the car, above the open air measurement, is what is called cabin gain..

Gotta see if I can find that issue. I'm sure someone on here knows for sure,

I also think there is a standard of in-car-gain at given sub frequencies...

I believe....

 

[SPL140.2 5,000+ posts]

you can do it by a cheap radio shack meter, using a sealed box graph each frequency usually 30-70hz but keep the meter at the same place and keep the volume the same as well, once that is accomplished take the sealed box out of the car and raise it off the ground a few inches, place the cheap meter about 3-4ft away and repeat the process but keep the volume the same as you did when it was in the car, go thru the tones again and graph them. When you have the results from both tests, compare them and notice the db jump from outside to inside and note that frequency that is usually your resonant frequency of the vehicle or cabin gain. Note with using the cheap meter will give you a great starting point for which tone is the loudest, could vary in frequency 3-6hz either way when getting metered with the termlab. Hope that helps.

egg

 

[DBBOOM 10+ year member]

Kinda thought there should be a formula for the chamber created by the cabin, and it could be considered a part of the enclosure. Then you could build to suit the cu ft of the cabin by tuning the enclosure to it.

 

[DBBOOM 10+ year member]

you can do it by a cheap radio shack meter, using a sealed box graph each frequency usually 30-70hz but keep the meter at the same place and keep the volume the same as well, once that is accomplished take the sealed box out of the car and raise it off the ground a few inches, place the cheap meter about 3-4ft away and repeat the process but keep the volume the same as you did when it was in the car, go thru the tones again and graph them. When you have the results from both tests, compare them and notice the db jump from outside to inside and note that frequency that is usually your resonant frequency of the vehicle or cabin gain. Note with using the cheap meter will give you a great starting point for which tone is the loudest, could vary in frequency 3-6hz either way when getting metered with the termlab. Hope that helps.
egg

Good info, thanks.

 

[WrenchGuy 10+ year member]

I thought it was speed of sound and distance from meter type shite?

I don't remember.

 

[SPL140.2 5,000+ posts]

Kinda thought there should be a formula for the chamber created by the cabin, and it could be considered a part of the enclosure. Then you could build to suit the cu ft of the cabin by tuning the enclosure to it.

no formula would work being every vehicle is different. Example if you take 5-10 same vehicles let say a yaris for example each one may have a different resonant frequency even though its the same car, but they should be close 1-5hz either way.

 

[SPL140.2 5,000+ posts]

I thought it was speed of sound and distance from meter type shite?
I don't remember.

sometimes it works in big extreme spl vehicles ive tried that in my neon came out to be 71hz //content.invisioncic.com/y282845/emoticons/crazy.gif.c13912c32de98515d3142759a824dae7.gif way off my gain was greatest at 47hz //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif by doing the test above the results from the cheap radio shack meter was peaked at 51hz so it came pretty close to the 47hz gave a good starting point. Once you acheive that, than get on a termlab and do the cut and test method to dial in on your tone.

 

[DBBOOM 10+ year member]

no formula would work being every vehicle is different. Example if you take 5-10 same vehicles let say a yaris for example each one may have a different resonant frequency even though its the same car, but they should be close 1-5hz either way.

Thats why im saying you could build to suit the cu ft of the cabin(which ever you are working with) not a fixed number. Just gettn a general idea 1-5hz would help, as you said.