resonant frequency determination

[damonhargroves07 0]

i have a 1997 mercury mountaineer (ford explorer). does anyone know what the resonant frequency is of my truck. when i find the resonant frequency what will that acomplish? do i need to catch my 1/4 wave at the dash at the frequency? im not quite catching this theory.thanks for any and all help

[damonhargroves07 0]

anything?

[ANeonRider 3]

Get a meter, a sealed enclosure & tones and measure away.

[farriswheel 0]

speed of sound is 1130f/s. Inches is better for vehicles, easier to calculate. so 12" times 1130 is 13,560 inches/second.

Now you measure the distance from the cone to the meter(the whole path it takes). remember the soundwave comes out of the front of the cone at 90 degress(straight) and out the back at 180. once you get the distance from the cone to the meter placement in inches, you divide that into 13,560. you will probobly get a high number, which is suspected. Since its 90 degrees, 1/4 waveform will be used. So 13,560/distance=x/4.

[almond 0]

that will probably get you close, but the cabin accoustics are going to play a huge role in the RF of the car.

[farriswheel 0]

the ports also have to take 3x as long to get to the meter as the sub, I THIINK.

[Tommythecat 0]

What the hell have you been smoking?

[farriswheel 0]

The idea is to align the rear wave with the front wave. This means that the front wave starts at 0 degrees and reaches the reference point at the dash at 90 degrees. On the flipside, the rear wave of the speaker starts at 180 degrees and reaches the dash in-phase with the front wave at 90 degrees. This means that the rear wave of the speaker must be exactly three times the length of the front. In equation form: 3A = B + C + D

what do you mean,"what have i been smoking"? please, tell me why i am wrong.

lottsa rude people here

[almond 0]

in a perfect scenerio that would work, more for a wall than anything else. but as far as daily drivers the acoustics of the vehicle are going to shift the rf.

[farriswheel 0]

lol you really like to argue with me.

[almond 0]

no, but i read the same article. it was about a guy building a crx. the way he was doing it is measureing from the sub to the mic and had to make sure the back of the sub to the mic was 3x the distance. the distance from the sub to the mic is the one that you use for finding out you frequency of burping. however in a daily environment that gets thrown out the window because the cabin is going to have a huge difference in where that rf is. that math isn't pefect for this situation. i understand what you're saying, but your misaplying your logic to this scenerio. know what i mean??

[farriswheel 0]

i think i do.. does it make a huge diff?

[almond 0]

i'm not sure. i've never measured my RF. never had a need to. the cabin volume should also play a huge role in rf. for two cars where the distance from sub to mic may be the same, but cabin volume is different the rf should be different as well.

[almond 0]

I know some one else like devildriver understands this better than i d, maybe they will chime in soon??

[damonhargroves07 0]

yea... lets hear it devildriver and thanks guys for your input!!

[///M5 2,833]

Get a meter, a sealed enclosure & tones and measure away.

You already had your answer...

[damonhargroves07 0]

i wanna stay away from building a new enclosure due to the fact mine is bolted to the frame. my vehicle is common so i figured someone would know!

[mrray13 30]

the problem is, no two vehicles are exactly the same. pulling down your visors will change things. adding a dahsmounted gps will change things. seats upright or laid back, all of those affect what a meter will read at the dash.

aneon hit the nail right on the head. if nothign else, seal up your current box (will make for a pretty accurate reading seeing it's the exact same box in the exact same location), grab your tones and a meter.

wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee

[///M5 2,833]

i wanna stay away from building a new enclosure due to the fact mine is bolted to the frame. my vehicle is common so i figured someone would know!

If you don't want to build another enclosure you aren't going to be able to use the information then anyway. It will take you multiple iterations to really dial things in. If you are serious about wanting the max output, get ready to build multiple enclosures not just one.