Wednesday 20 April 2016

current - Lower than expected power consumption from speaker drivers


I'm using two Visatron FRS 5X-8 Speakers in a project. The amplifier being used is a Dayton KAB-215. Powering the whole thing from my power supply at 12V, I see a current draw of ~50 mA even at full volume. I'm a bit confused by this result.


My math suggests that for the two 5W RMS (8W Max) speakers I should see around 10W of power draw or ~.8A @ 12V. While I realize they may not operate continuously at this power during music, there is a big spread between 600 mW and 10W.


It seems like both the power supply (150W) and the amplifier board (2X 15W @ 8 Ohm) have tons of headroom here, so I don't really understand the low power draw. The bluetooth board doesn't have a volume knob on it currently, which the datasheet indicates should result in "full volume" on the amplifier side. My phone volume is maxed (when testing), and yet the power draw is super low. The speakers are fairly loud but not insanely so. I do have SPL measuring equipment that I can use to try to validate if the output is close to what it should be, but I'm still a bit perplexed.



I look forward to your thoughts on what is limiting the current draw, and whether this is a surprising result or not.




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