posted
almost splferrell. it's voltage divided by amperage Ohm's Law states that E=I*R R is Resistance(Ohms) E is Voltage(Volts) I is Amperage(Amperes) P is Power(Watts)
R=E/I R=E^2/P R=P/I^2
Ok David. Measure you nominal resistance with power off. Now put the clamp on the + output wires from the amp to the speaker. Put the voltometer on the + and - outputs of the amp. Power everything thing up. BURP!!!! Quickly write down the voltage and amperage. If you have a termlab, THEN write down the SPL. Calculate power by multiplying Volts*Amps. Then divide Volts by Amps for reactive impedance. Subtract the nominal impedance, and you have your impedance rise for that frequency, power, and enclosure. Change one of those factors, and the rise and final impedances will change. Every few burps, get another nominal impedance measurement, since hot coils may read different
If you have a second clamp and voltometer, you can measure amplifier efficiency at the same time.
-------------------- World Record-Loudest SPL in my driveway Team Powermaster/XS-Power Hifonics Amps, Kicker subs-The way it should be....all were Stolen from me...boo hoo Zensky....World Domination at It's Finest www.zensky.com Posts: 3723 | From: Columbus, OH - formerly FL | Registered: Oct 2003
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posted
an example...on 10kW of power, you may find that you get 155.0dB on 10,540W at 58Hz. You might find that at 55Hz, you get 154.8dB on only 8kW. 20%less power should make more than a 0.2dB loss. Obviously, your output design is more efficient 3Hz lower. Find a way to bring down the note without major volume and port change, and try again. If done right, you're peak spl should be at a lower freq, but your power demands lower. Meaning the system is more efficient. If measuring amp power input as well, you can find the point where lowering coil impedance for more power, versus amplifier efficiency reaches a neutral point. at some point of lower impedance, the amp will start sacrificing efficiency quickly. Not actual measurements, but a low impedance survivor... an Ia20.1 may do 900@2ohm, 1800@1ohm. half impedance, double power. half that impedance, maybe only 30% more power. half impedance again, maybe only 16% more power. Run the amp at 0.17ohms, maybe only 3100W. Now you're at 1/6 the impedance, but only 70% more power. drop the impedance by half one more time, and only gain 4% power. no longer is the efficiency loss worth the 6 extra batteries.
-------------------- World Record-Loudest SPL in my driveway Team Powermaster/XS-Power Hifonics Amps, Kicker subs-The way it should be....all were Stolen from me...boo hoo Zensky....World Domination at It's Finest www.zensky.com Posts: 3723 | From: Columbus, OH - formerly FL | Registered: Oct 2003
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posted
But whatever your reactive load is, is the load that your amplifier sees and puts out power at. For example if you have a .25 ohm nominal load and when you calculate your rise you have a 1.08 ohms reactive load, the 1.08 ohms is what load your amp is seeing and putting out power at.
-------------------- Posts: 1026 | From: North Carolina | Registered: Jan 2008
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quote:Originally posted by D-Bass: an example...on 10kW of power, you may find that you get 155.0dB on 10,540W at 58Hz. You might find that at 55Hz, you get 154.8dB on only 8kW. 20%less power should make more than a 0.2dB loss. Obviously, your output design is more efficient 3Hz lower. Find a way to bring down the note without major volume and port change, and try again. If done right, you're peak spl should be at a lower freq, but your power demands lower. Meaning the system is more efficient. If measuring amp power input as well, you can find the point where lowering coil impedance for more power, versus amplifier efficiency reaches a neutral point. at some point of lower impedance, the amp will start sacrificing efficiency quickly. Not actual measurements, but a low impedance survivor... an Ia20.1 may do 900@2ohm, 1800@1ohm. half impedance, double power. half that impedance, maybe only 30% more power. half impedance again, maybe only 16% more power. Run the amp at 0.17ohms, maybe only 3100W. Now you're at 1/6 the impedance, but only 70% more power. drop the impedance by half one more time, and only gain 4% power. no longer is the efficiency loss worth the 6 extra batteries.
Written very well Donald.
-------------------- 95 2 door Tahoe 4 DD 9515D's, 2 Stetsom 7kd's. 154.4 Legal @42hz Super Street No Wall. 4 DD 9515D's,4 AQ 2200D's. 153.0 certified Legal TL @42hz 151.5 @32 hz Legal TL Usaci Outlaw 154.7, SB4 153.5db 2008 DB Drag Racing World Finalist. Finished 4th in Indy.Super Street No Wall. 2008 Bass Race World Finalist. Finished 4th in Indy 140-149.9. Rebuilding for 09 Posts: 219 | From: BURLINGTON, KENTUCKY | Registered: Dec 2007
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-------------------- World Record-Loudest SPL in my driveway Team Powermaster/XS-Power Hifonics Amps, Kicker subs-The way it should be....all were Stolen from me...boo hoo Zensky....World Domination at It's Finest www.zensky.com Posts: 3723 | From: Columbus, OH - formerly FL | Registered: Oct 2003
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posted
Donald said it best. I have been doing a lot of what you are trying to myself this week David
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posted
Wow what information here ,good job donald ,I tested mine and i am running at .5 ohms to each amps getting 98.6 volts x 46.2 amps and imp rise of 2.1 -.5=1.6 the amp sees .I wonder does that sound about right ?
98.6x46.2=4555.32 watts 98.6 div 46.2=2.1 voltage drops from 17.6 to 14.2 on 3 second burps i only use 7 batts turbostarts on 2 xxx 6500's
someone correct me if i am wrong on the figures
-------------------- TEAM PINNACLE TEAM SOUTHEASTSPL Personal goal is to hit 160 db's with only 2 amps Florida state finals 2nd place scored 158.1 certified ranked #24 in the world for 2008 season If all goes well watch for 2009 Posts: 2419 | From: GRN CVE SPRGS | Registered: Oct 2004
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quote:Originally posted by TeamSubGoPoof: Close Ron, you don't subtract the original impedence.
Your amps see 2.1 during a burp which is around a 4x impedence rise.
I bet you're running a pretty small enclosure?
17 cudes after displacement of port and subs . all for 4 15's
-------------------- TEAM PINNACLE TEAM SOUTHEASTSPL Personal goal is to hit 160 db's with only 2 amps Florida state finals 2nd place scored 158.1 certified ranked #24 in the world for 2008 season If all goes well watch for 2009 Posts: 2419 | From: GRN CVE SPRGS | Registered: Oct 2004
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quote:Originally posted by Sinister-David: ok so u don't subtract the original impedence? and what are somethings u can do to get your impedence rise lower?
I am wondering the same .
-------------------- TEAM PINNACLE TEAM SOUTHEASTSPL Personal goal is to hit 160 db's with only 2 amps Florida state finals 2nd place scored 158.1 certified ranked #24 in the world for 2008 season If all goes well watch for 2009 Posts: 2419 | From: GRN CVE SPRGS | Registered: Oct 2004
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quote:Originally posted by Sinister-David: ok so u don't subtract the original impedence? and what are somethings u can do to get your impedence rise lower?
I am wondering the same .
The bigger the box the less impedence rise is what I've always been told. Make the box bigger. Most serious drag cars have huge enclosure's for even 2 18's. I've seen 2 18's in 40 cubes before so if the bigger the box the less rise then that particular box must not have had a whole lot of rise to it.
-------------------- Posts: 1026 | From: North Carolina | Registered: Jan 2008
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But when you get too big the box wants to peak lower which hurts SPL.
In a normal ported box when you get it tuned in perfectly and you play around tuning it also decreases impedence rise because the woofers aren't moving as much
Impedence rise is a bitch lol, also any flexing in the enclosure will incrase impedence rise
-------------------- Posts: 6884 | From: Russellville AL | Registered: Nov 2002
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