Finding Resonant Frequency

[CrazyKenKid 64]

So I have heard to get optimum spl out of my box and best proforance out of my sub I would have to find the resonant frequency of my car. So I fired up the SSA forum seachers and i didn't come across so I imediatly fired up the google machine and did some seaching and here is my findings:

I can use math by:

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.

or using a sealed box a sub and a meter.

here are the 2 site i borrowed info from:

http://forum.realmofexcursion.com/competitions-organization-meets-discussion/28614-how-figure-out-your-cars-frequency.html

and

http://audioforum.termpro.com/cgi-bin/ubb/ultimatebb.cgi?ubb=print_topic;f=6;t=000944

now I haven't done either of these yet but i will try out the measurment idea tomrrow ish and get back to you at what i get. also it has been recommend to me to use 41.5hz!! so we will see how close i get with math.

NOW onto my question who has done either of these methods and more importantly has anyone done both of these methods and then compared them? If so what did you find? is it best to use a speaker or jsut work it out with math?

thanks for your time and input

Kenneth

[jcarter1885 995]

So I have heard to get optimum spl out of my box and best proforance out of my sub I would have to find the resonant frequency of my car. So I fired up the SSA forum seachers and i didn't come across so I imediatly fired up the google machine and did some seaching and here is my findings:

I can use math by:

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.

or using a sealed box a sub and a meter.

here are the 2 site i borrowed info from:

http://forum.realmofexcursion.com/competitions-organization-meets-discussion/28614-how-figure-out-your-cars-frequency.html

and

http://audioforum.termpro.com/cgi-bin/ubb/ultimatebb.cgi?ubb=print_topic;f=6;t=000944

now I haven't done either of these yet but i will try out the measurment idea tomrrow ish and get back to you at what i get. also it has been recommend to me to use 41.5hz!! so we will see how close i get with math.

NOW onto my question who has done either of these methods and more importantly has anyone done both of these methods and then compared them? If so what did you find? is it best to use a speaker or jsut work it out with math?

thanks for your time and input

Kenneth

From what I read about shizzzon and others trying to compete that you should just build a simple box and play tones on up to 80hz I believe (or less) and see have a mic handy (doesnt have to be accurate) to see what frequencies your hitting higher dbs at and that should tell you your cars' resonant frequency. If Im wrong then the SPL gods on here will help you, but check under the SPL thread on this forum and Im sure its a few topics that this is posted in. Good luck man.

[ncacoates 104]

I think to find your true frequency its trial and error as so many variables effect it. Right now mine is 44hz with my box tuning at 30hz. Say i tune my box to 35hz my frequency may shift upwards to say 50hz. Iv seen it happen like this before in many applications but it may not hold true in all cases. If you want to find your present resonance frequency find someone with a meter and run a sweep from say 80-20hz at half volume. If your using a TL itll tell you at what frequency it was loudest.

[CrazyKenKid 64]

question do i have to use a sub? or can I just use a mid bass (6.5inch speaker or a 6x9 in a sealed box) b/c if i play it half volume i shouldn't bottem out my speaker right? as for the sweep i got some tones on my pc i can play.

one more question once i get my resonant frequency would i subtract a few hz's from the tuning of my box? like if my resonant freq was 48 i would tune my box to 42? is that what you were getting at MemphisMzd ?

and thanks so far for your help you guys have help out so far!! and i will for sure give those spl boards a read once i get out of school!

thanks again

Kenneth

[Thumpper 266]

you need to build a simple sealed box and do several sweeps with it facing in different directions...

you will get different readings....just average it out and go with the one in the middle...you will be close

[coreycgarner 1]

you need to build a simple sealed box and do several sweeps with it facing in different directions...

you will get different readings....just average it out and go with the one in the middle...you will be close

I agree.. I was thinking you are also supposed to take the sub and sealed enclosure out of the vehicle and place the meter so many inches in front of the sub to find the frequency of the sub.. not sure though!

[Basshead 3]

I think to find your true frequency its trial and error as so many variables effect it. Right now mine is 44hz with my box tuning at 30hz. Say i tune my box to 35hz my frequency may shift upwards to say 50hz. Iv seen it happen like this before in many applications but it may not hold true in all cases. If you want to find your present resonance frequency find someone with a meter and run a sweep from say 80-20hz at half volume. If your using a TL itll tell you at what frequency it was loudest.

that is not the resonant frequency of the vehicle, that's just the peak frequency of the box, hence why you change tuning, your peak changes. thumpper has it right. a small sealed box. find the peak (or peaks and average them) and that'll be the vehicles resonant frequency

[CrazyKenKid 64]

okay lets go one step forward lets say i find my resonant frequency of my car, so once i get that number how does that help to determine my sub's box frequency?

i know my car's resonant frequency isn't what i tune my box to so what would i tune my box to say if my resonant frequency in my car was 50hz?

also does it matter what sub i use? can i use an 8inch in a sealed box? or does it have to be like a 12?

[CrazyKenKid 64]

i think i found out how to do it!

thanks guys!!!

and

[shizzzon 461]

if u have a tlab, sweeping at near max volume will only get u close.

Tlab is still inaccurate i see a lot about finding peak note from a sweep.

Whatever tlab tells u your peak is from a sweep, subtract 2 and add 2 from this number and try burping all 5 of those frequencies until u find the loudest one.

Once u know ur peak, then it's trial and error port-wise to get the best performance from your port.

[CrazyKenKid 64]

i got another question know. if i set my tuning in my box to the PERFECT tune and i am not competeing full time was all that just a waste? like ppl who perfectly tune there car's are like spl head ppl and hit high ass numbers on the meter and what not plus they sink all kinds of time and money into these builds and live for shows and the next big one! so is it really worth it for me to go though all of this and building multiple box's! and what not. or should i jsut tune it to 41.5hz and call it a day lol.

[shizzzon 461]

no, u should find ur peak so u know what tone to play, then start trying ports over and over until they reach full tilt.

You can change volume afterwards and start testing that but if u are not a truly dedicated competitor, then u can answer your goals yourself.

[CrazyKenKid 64]

no, u should find ur peak so u know what tone to play, then start trying ports over and over until they reach full tilt.

You can change volume afterwards and start testing that but if u are not a truly dedicated competitor, then u can answer your goals yourself.

wisely put! thankyou very much for your input and help!!

Kenneth