posted
Just wondering if anyone has tryed tuning boxs and ports with an impedance meter for SPL. My understanding is a ported box has two peaks in the impedance. If you tune a sealed box(by changing the volume) to the resonant frequency of the car by measuring the highest impedance. Then trim a port untill you get the highest impedance. Would this give the best SPL box for my car. I ask this as I don't have a SPL meter witin 500km and can build a cheap impedance meter.
Note: All testing done in car at high volume.
-------------------- Street C 147.1dB 1 X ddz1 1 X AUDIOBAHN 18 Posts: 14 | From: Australia | Registered: Aug 2004
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posted
Send me an email with a copy of your plan to build this meter- sounds like an interesting project! I would think, though, you would want the lowest impedance under a burp possible to get the most outta yer amps. This is one thing to consider when going for the high spl numbers, ey!
posted
I'll try to get a circuit diagram done up. The highest peak in your impedance is were the box is most efficent(resonant frequency). With a ported enclosure there is 2 peaks one for the driver and one for the port. When I get some spare time and a use of a mic I will give it ago.
Why can alot of people get away with very low impedances for amps during burps? Well most of the time their impedance is alot higher than they think. How many people measure they're impedance at the frequency they burp. Your 1ohm coil may be 4ohms! How much power are you really running.
-------------------- Street C 147.1dB 1 X ddz1 1 X AUDIOBAHN 18 Posts: 14 | From: Australia | Registered: Aug 2004
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IT's a good idea (impedance meter).. i am presently building a power meter(measure rms power that goes to the woofer. the wiring of it is simple and easy to use. Two wire that need to be plugged to the amp and two other to the woofer. A 40A shunt is between one of those wire and i use the voltage across the shunt to get the current that pass to the woofer coil. with arithmetic analog chip ( division, and multiplication) i get the impedance and the power. i also get the voltage and the current,, so this litytle gadget can be use to ajust amplifier gain without multimeter.
tThe idea with this is to be able to measure all those parameter with the woofer connected to the amp.. and to get the real value
I use operational amplifier to amplify the low signal of the shunt (like 50mV for 40A) and i use direfct voltage of the woofer wire that i divide and with those two signal it's simple to get any of voltage, current, impedance or power with simple circuit operation. some IC can multiply or divide signal..
after thao you have just to buy a digitasl panel meter (0-200mv at input) at digikey and adjust gain factor and you will get the right result to the panel
spec: ---0-2000Wrms (limited by the digital display i use) ---0-150Vrms ---0-35A 0.1 to 2000ohms
the last step to terminate this gadget is to build a +/-15V power supply for the operational amplifier) because this stuff will be portable
I will finish to draw the shematic and i will share it to everyone taht would that
Doc
-------------------- Street A "not legal but not outlaw!" Score in my integra: -152.34 dB 51Hz TL sensor -157,1dB 51Hz AC mic
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CRAZY TESTs: ||||||THE ONLY 6.5" TO SCORE 168.9dB(TL)OUTLAW IN THE WORLD with 6 Watts.|||||| -Crazy 5.25 Bose sub 1.1cu box: 138.0dB TL mic 55Hz with ONLY 100W ! ---------------------------------- www.teamxmax.com Posts: 643 | From: Quebec city | Registered: Mar 2000
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quote:Originally posted by team basket kase: Send me an email with a copy of your plan to build this meter- sounds like an interesting project! I would think, though, you would want the lowest impedance under a burp possible to get the most outta yer amps. This is one thing to consider when going for the high spl numbers, ey!
I think that I have said too much....................I must go now................the SPL Ninja's are upon me Need more power? UP YOURS!! with Excessive Amperage! Posts: 6070 | From: Northern California | Registered: Nov 1999
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I think that I have said too much....................I must go now................the SPL Ninja's are upon me Need more power? UP YOURS!! with Excessive Amperage! Posts: 6070 | From: Northern California | Registered: Nov 1999
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