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is this something you can do your self or do you have to go to a shop to get it done? I was thinking, for a ported system you would have to find the resonant freq and then tune your ports to it, to get max spl. Was my thinking right? What freq are resonant freq's around?
------------------ 2 Fosgate Power Dvc 15's and 2 Power 1100a2's comming soon! www.sounddomain.com/2592
posted
I am about to travel just that road my friend. I just ordered a sound level meter from Radio Shack. Hopefully it'll be here by Friday. I was told exactly what you questioned, find your car's resonant frequency then tune your box to match it. I've never used one of these meters, or even seen it used, but I compete and I want to win so I'll do what I can to be the best. The meter I bought is $60, but they offer a cheaper one for $35.
$60 sound level meter goes to 126 dB, but it's digital and I'd sayeasier to read. I wonder why audio shops that know your competing don't have this on hand to help you out, instead of having to buy it yourself? None of them have the expensive RTA's either. Kinda dissapointing for Phoenix.
[This message has been edited by KLW designs (edited 01-10-2000).]
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I'm not an expert at this, but this is how it was explained to me: basically, a simple way to do it is to take the meter and run a sweep, or play frequency tracks, until you find the loudest one. use that. or, a more complicated way i was told to try is to make a simple box for a single sub. measure the output in an open area, like a driveway or yard. Keeping the mic the same distance from the speaker, do the exact same test in the car. this will show you how much cabin gain you'll get at which frequency. The radio shack meters (at least the cheap one) only goes to 130db, so most likely you'll have to use a lower volume, but the frequency will be the same. hey KLW any idea how high the more expensive meter will go?
------------------ You will hear the thunder before you see the light Why do my JL's have to be so ugly? W6's are SQ subs? Who says? not me!
Posts: 1930 | From: state college, pa | Registered: Sep 1999
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posted
the radioshack goes up to 125db at which point they are not accurate. Keep it under 120db to be safe. Maybe Thunder-N-Light talking about a different model. guess that parts not important anyway. but ya, listen to Thunder-N-Light.what he said is correct.
Also I built a wall in my car. to figure out my gain I divided something like 1152( the speed of sound) by twice the largest dimension and came up with a number like 95hz. This is where my car starts a 12db/octave gain. that means at 47.5hz my car gain is +12db and at 23.75hz my gain is +24db. well I calculated this before I put the wall in my car. then i added the gain to what the speaker box program calculated. and when I measured the response in my car with a meter and tone generator I got almost exactly what I predicted. I was pretty impressed. I always hear that math does'nt work in the real wourld. It did for me!
Posts: 1269 | From: Fullerton. CA ,USA | Registered: Oct 1999
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I just want to throw in some real world experience I came across to try and help out....I have found that when you build a box to a certain frequency, say 40hz, your peak frequency is about 12 hz above that. Not sure why, but it is very accurate. I competed all year long with a car that was never tuned, and hit all my highest numbers at 12 hz above what my box was built for. This is not a freak occurance or one time deal....I have noticed all competitors have found this out... Tony Jordan MAD
------------------ Stop asking dammmm you....No one is tryin to steal my Lucky Charms
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the guy that has helped my shop design boxes for years has always told me that never under stood why but hew seems to be right Posts: 78 | From: Holland,Mi,USA | Registered: Nov 1999
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posted
Thunder is right. What he is talking about was explained in an issue of AS&S last year( i believe) in their "SPL Series" by Chris Lewis. ( if that helps)
Gabriel anyone else in TX?
Posts: 3901 | From: San Antonio,TEXAS !!!! | Registered: Nov 1999
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