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Given a speaker is 30 watts, which is louder, the one with higher current through it or the one with higher voltage across it. Lets say both speaker has variable impedance (so we can vary both current and voltage). According to my research and analysis, the current is what drives the coil to produce vibration and thus rarrifying the air molecules around, so it turns out that a larger current would mean larger loudness. So is it safe to say that current is directly proportional to loudness?

In other words, which is louder, a speaker that is driven by a 3 Ampere current back and forth oscillating at high frequencies but with low voltage or a speaker that has very large full swing peak to peak voltage from up to bottom but low current?

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If the impedance is fixed, as in 4 Ohms in your example, then you don't get to control voltage and current independently. – Olin Lathrop Nov 24 '12 at 13:58
ok what if the impedance is not fixed??? so we can play with current and voltage, which one is louder. high current or high voltage. my intuition is going for current – vvavepacket Nov 24 '12 at 14:01
already revised the question "remove fixed impedance" – vvavepacket Nov 24 '12 at 14:01
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You have asked a bunch of questions related to the same homework. It is now clear you don't know what is going on and are apparently trying to bluff your way thru some electronics course without even basic understanding of voltage and current. You are in over your head and need to sit down and learn the fundamentals or seriously re-evaluate your career choices. Even if you manage to pass this course, then what? Who is going to hire a EE who only got the diploma but doesn't know anything? – Olin Lathrop Nov 24 '12 at 14:07
@OlinLathrop i really need to sit down and learn the fundamentals. tnx for awakening me – vvavepacket Nov 24 '12 at 14:13

closed as not a real question by Leon Heller, Anindo Ghosh, Dave Tweed, Brian Carlton, W5VO♦ Nov 29 '12 at 5:25

It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, see the FAQ.

2 Answers

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All else being equal, neither. It's the product of voltage and current that matters, i.e. power, which you have fixed at 30W.

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up vote 2 down vote

Loudness is a human perception and is not measured in Volts, Amps, or Watts unless there is a reference to convert it.

e.g. You can have a speaker resonate with high efficiency or a mid range without a crossover produce pressure waves with high efficiency. You must also understand the human ear has very different perceptions of loudness acorss the spectrum that changes with the amplitude over a 100 dB range.

The correct answer for which is loudest is the one that is preceived with the highest pressure waves often measured as dB/W @ 1KHz for general purpose comparison. Naturally this is complex and has many variables including the Fletcher-Munson curves.

For simplicity, Watts input power (rms) must be measured over the normal human hearing range with measured sound pressure ( by a calibrated microphone) to detemine relative "loudness".

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