resonant frequency

[KARLEON 10+ year member]

Ok, fund are really low right now, so i dont even have 50 bucks to buy one of those cheap radio shack meters. And i really want to do my best at the sound off on the 25th so im trying to figure out my resonant frequency. Yesterday i done searches after searches after searches on numerous forums on the topic. I was hoping to find someone with the same exact car as mine who has already found out their resonant frequency, and i know it can still vary, but atleast that would have been my best guess.

Anyways, i came across a formula and say it a few times, but i just wanted to know who all has used it and does it work out pretty well....

Basically you are suppose to measure the center of the sub perpendicularly (straight out) until you hit the dash. this gives you the length of the 1/4 wave. Now multiply that by 4 and divide by 1130

then i heard 1130 divided by (what ever the length was) and divide that by 4 instead of multiplying it by 4.

I really really need some help with this resonant frequency thing. Im going to do my best to try and get this meter, at the least, find someone i can borrow the money from, get the meter, use it, and take it back and make up some story about thats not the right kind of meter. but anywayz.... any help is appreciated

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[KARLEON 10+ year member]

urgh, i dont think that formula works or im doing something wrong, because i came up with 31. That seems a little low for my resonant frequency. By the way, its a 1996 Honda Accord Lx, if anyone has already figured it out for their honda or know where it says it online

 

[KARLEON 10+ year member]

Ok, i came across a little bit of money so im going to buy me one of those cheap radio shack meters to find my Resonant frequency. But before i get started on this tomorrow, i want to make sure im on the right track.

Set EQ and everything at 0

have a sealed box

play every frequency and write down what the meter reads.

When i find my peak i should tune my box accordingly.

Im not getting this octave stuff. Do i tune my box 1/2, 1/4, or 1/8 below my resonant frequency?

And is there anything i have left out that i need to make sure i do.

Please respond ASAP guys. really really need your help

 

[XDrkmanX 10+ year member]

I'm trying to find my as well.

What I did was play test tones 60-30hz and try to see which one measured the highest on my Epic-150. I think I got a little carried away with it, I could start to smell my voice coils burning.

Good luck and let me know if that formula works.

 

[KARLEON 10+ year member]

Ok, this is what i did. I had my cheap radio shack meter. I heard you are suppose to use a sealed box with a 10 or 12. But i dont have a sealed box just laying around nor do i have the extra cash to buy some wood to make one. So i just used my subwoofer enclosure i have now for my Magnum D2s. Its tuned to 29hz, but i just done my best to plug it up. My drill was giving me problems, so i couldnt just tighten another piece of wood over my vent. I found a scrap piece of wood i had from making that enclosure and put it in there. It was still very loose, so i took 2 of my school shirts, folded them up real tight and stuff them in there as well. To top it off, i duck taped the crap out of all of it. So you can basically say i had a sealed box.

First, i went ahead and set my head units EQ to 0 (or basically just made everything flat with no negatives or postives) On my sub level, i had that on 2 of 12. And my head unit volume i set at 0 with no negatives or positives. So basically everything was flat as i could make it.

The cd i used had tones from 20hz-80hz. I only played and recorded from 30hz-56hz. My accord ended up peaking at 49hz. I then went and played with my amplifier settings. I got my lil sister to hold the meter while i just turned up settings to its max and back down to its least to see where i would be getting the most of my amp at. I set all of that accordingly.

All i need to know now is, when designing my subwoofer enclosure. Im still lost on how many octaves below tuning should it be. The 1/2, 1/4. or 1/8. Im pretty sure its not the 1/2, but one of you SPL heads on here needs to help me out. Please //content.invisioncic.com/y282845/emoticons/toast.gif.bc0657bf54b9ee653b6438524461341e.gif Other than that, i think i am fine. Soon as im done, the meter is going back to radio shack, so i can get my money back to go to Lowes to buy my enclosure stuff. lol. Anyways, please help if you all know where would it be best to tune my box too if my resonant frequency is 49hz

 

[ghs_wrestler189 10+ year member]

mattj knows how to do it, send him a PM

 

[ghs_wrestler189 10+ year member]

I'm not 100% sure, but I think you tune your box to the resonant frequency to maximize SPL.

 

[ghs_wrestler189 10+ year member]

I don't think your formula is accurate, it's 91.5 inches from the center of my sub to the dash, which gives a res freq of 3.45???

 

[Benny212 10+ year member]

try using winisd to model your frequency response for your box, tune the box to where you peak at 49 hz. I think that should be 1/8th of an octave but I could be wrong, anyways that would be an easy way to figure out which one is right

 

[KARLEON 10+ year member]

I don't think your formula is accurate, it's 91.5 inches from the center of my sub to the dash, which gives a res freq of 3.45???

Which formula? The very first one i posted? I know that was wrong. Thats just something i discovered while doing searches on the topic. I came across some money and bought a radio shack meter, and i pretty much think its accurate. And im thinking it's 1/8 of an octave too. A thread on termpro.com had a small break down of it, and it said

1/2 octave below = frequency x 0.75

1/4 octave below = frequency x 0.875

1/8 octave below = frequency x 0.9375

So if i peaked at 49... 1/2 below = 36.75

1/4 below = 42.875

1/8 below = 45.9375

So if its 1/8 then i would tune my box to 46hz and play that 49hz test tone and watch the crowed go ooooooo aaaaaaaa //content.invisioncic.com/y282845/emoticons/cool.gif.3bcaf8f141236c00f8044d07150e34f7.gif

 

[fintheman 10+ year member]

blah, stop this talk

I just hope putting me RE SX 15" in 4.5 Cubes 32hz is gonna sound fine.

Get me worried with all the peak/linear talk

-fin //content.invisioncic.com/y282845/emoticons/cop.gif.57eb2cc10a7efd04d31083ca3c30d53c.gif

 

[KARLEON 10+ year member]

blah, stop this talk
I just hope putting me RE SX 15" in 4.5 Cubes 32hz is gonna sound fine.

Get me worried with all the peak/linear talk

-fin //content.invisioncic.com/y282845/emoticons/cop.gif.57eb2cc10a7efd04d31083ca3c30d53c.gif

It should sound fine. Right now i have my Magnums tuned to 29hz, and boy can i feel my bass. In my opinion, i have a very nice setup. I hear people talking about the real SPL guyz find their resonant frequency, and ladda ladda ladda to put up high numbers, so i figured i'd see what i can hit by doing so. Last time i hit 142.3 and i really didnt even try at all. i went to the comp. just to chill but after i saw and heard some of those people set ups, i had to rush and put mine in. I ended up winning my class on my first comp. I figured people have peeped me out, so now they are trying to top me, so i stripped out my 4 gauge and replaced it with 0 gauge. Bought an 180amp alternator. About to build me a higher tuned box. So yea, i'm ready to kick *** and take names again

 

[XDrkmanX 10+ year member]

I wanna hit 147-150 at the SLAP show by me this weekend. Last year I hit a 143.7 on two XXX 12 w/ 1000 watts each. I was actually a little disapointed by my score. Then I found out that one of my amp was shot. So I actually hit 143 on a single XXX 12.....better, I guess.

I know if I had the proper size box for my sub 150 should be relatively easy.