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Bob365 Unregistered guest | I have a Memphis MC1000D amp that does 300 @ 4,600 @ 2,1100 @ 1. I was wondering about current draw at different ohm loads and different spl's. Take 2 subs of the same design. One has a 4 ohm DVC and the other has a 2 ohm DVC. Hook up only 1 sub at a time. With the 2 ohm DVC, I can show a 1 ohm load and get 1100 watts. This should draw more current than the 2 ohm load, correct? Now this sub is louder at full power. If I turn down the volume on my headunit so the SPL of both subs is the same (ie 1 ohm load not at full power) will I be drawing roughly the same amout of current for each setup? Thanks. |
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Gold Member Username: SouthernrebelMonroe, Louisiana USA Post Number: 1893 Registered: Mar-04 | at 1ohm the amp would pull ~120-125A...(1100wrms) at 2ohms it would pull ~70-75A (600wrms) at 4ohms ~35-40A (300wrms) |
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Bob365 Unregistered guest | So if I run it at 1ohm at 60% volume would it have the same current draw and produce the same spl as the 2 ohm at 100% volume? |
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Silver Member Username: N2audioLawrence, Ks USA Post Number: 389 Registered: Mar-04 | in a nutshell, yeah. Current draw is all about power, and the efficiency of the amp. A 600w at 1 ohm class D and a 600w at 2 ohm class D are going to draw similar current. Not exactly the same just due to differences in specific topology, but yeah - power and class are the major factors. |
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Silver Member Username: SymplestilesStockton, CA Usa Post Number: 455 Registered: Aug-04 | i was wondering the same thing actually. if i have a 600x1@2ohm amp but only turn the volume up 3/4 the way (assuming the gains are set correctly) it should only act like its drawing around 450 watts correct? this is what kinda got me thinkin about not upgrading my alt yet, i will rarely if ever reach the full amount of draw from the amp. |
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Silver Member Username: N2audioLawrence, Ks USA Post Number: 393 Registered: Mar-04 | RMS power ratings are only achieved with sine wave test tones. If you're playing music - even at full (unclipped) volume, only about 1/3 of rated power is required from the amp. So let's say your amp is capable of 600w playing test tones, and it's 75% efficient. 600/.75 = 800w Assume a duty cycle of 1/3 800/3 = 277w at 3/4 full volume it's quite possible you're only pulling 200w (or ~15A) from your alternator. I think RC took the theory a little too far in this thread -- but it definitely puts current draw in perspective. There's a lot of info on the subject at carsound. Search for duty cycle or crest factor. |