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RF T30001bd Clamped
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<blockquote data-quote="IgnoreMe" data-source="post: 3572871" data-attributes="member: 551352"><p>you made a mistake...</p><p></p><p>and i know exactly what it is....why? because i made the same one when i was still somewhat new to car audio and got my *** chewed out by immacomputer (glad he did it though, even though i was too pissed off to admit it).</p><p></p><p>you do not measure battery voltage, and then amperage up underneath the hood. you need to do it at the amp. for example, stick 1 dmm lead into the positive speaker terminal and one on the negative speaker terminal. then place the clamp around the speaker wire going to the subs. get a voltage and an amperage reading at the same exact time.</p><p></p><p>multiply them to get wattage.</p><p></p><p>divide voltage by amperage to get impedance.</p><p></p><p>as you can see, using ohms law you are sitting at .06 ohms, even though you're wired up to 1.33 ohms.</p><p></p><p>this would mean you are getting ~2kw @ .06 ohms out of an amp thats suppose to do 3k+ @ 1 ohm. see what i mean? easy to see the problem now, i hope //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif.</p><p></p><p>BTW: even doing it the way i mentioned above will still give you "apparent power" and not real world power. however, the closer you are to the DCR, the more accurate results. what im getting at is, if you wired to a 1 ohm load, and are getting 4 ohms as your lowest impedance after box rise, your power calculation is going to be a good bit off and not very accurate. however if you're wired @ 1 ohm and rise to say 1.5 you are a good bit more accurate. remember the closer to DCR, the more accurate the results. its the same reason you see guys with 2.5kw @ 1 ohm amps, clamping and then calculating out 2kw @ 4 ohms. this is apparent power, and not what the sub is actually seeing. you can calculate it all out using some kind of math (ask immacomputer, i just saw a thread explaining out to calculate power factor and all that good stuff) and a "power triangle" (IIRC thats what he called it)</p></blockquote><p></p>
[QUOTE="IgnoreMe, post: 3572871, member: 551352"] you made a mistake... and i know exactly what it is....why? because i made the same one when i was still somewhat new to car audio and got my *** chewed out by immacomputer (glad he did it though, even though i was too pissed off to admit it). you do not measure battery voltage, and then amperage up underneath the hood. you need to do it at the amp. for example, stick 1 dmm lead into the positive speaker terminal and one on the negative speaker terminal. then place the clamp around the speaker wire going to the subs. get a voltage and an amperage reading at the same exact time. multiply them to get wattage. divide voltage by amperage to get impedance. as you can see, using ohms law you are sitting at .06 ohms, even though you're wired up to 1.33 ohms. this would mean you are getting ~2kw @ .06 ohms out of an amp thats suppose to do 3k+ @ 1 ohm. see what i mean? easy to see the problem now, i hope [IMG]//content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif[/IMG]. BTW: even doing it the way i mentioned above will still give you "apparent power" and not real world power. however, the closer you are to the DCR, the more accurate results. what im getting at is, if you wired to a 1 ohm load, and are getting 4 ohms as your lowest impedance after box rise, your power calculation is going to be a good bit off and not very accurate. however if you're wired @ 1 ohm and rise to say 1.5 you are a good bit more accurate. remember the closer to DCR, the more accurate the results. its the same reason you see guys with 2.5kw @ 1 ohm amps, clamping and then calculating out 2kw @ 4 ohms. this is apparent power, and not what the sub is actually seeing. you can calculate it all out using some kind of math (ask immacomputer, i just saw a thread explaining out to calculate power factor and all that good stuff) and a "power triangle" (IIRC thats what he called it) [/QUOTE]
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