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Interesting Observation/Subwoofer Power
#324949 10/06/10 03:46 PM
Joined: Aug 2009
Posts: 71
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I'd like to report some interesting observations about my HT setup as well as ask a question to all the smarty/technical people who understand this stuff much more than I do.

I recently purchases a Kill-A-Watt meter to make sure that my computer's power consumption was not exceeding the rated specification of its power supply. Anyway, last night I took the meter down into the HT to test the "real-world" power draw of my components.

I was happily surprised to find that all the HT stuff did not draw nearly as much power as I expected. I must also give a "BRAVO" to my Axiom speakers as they seem to sip power. My HT receiver (Denon AVR-790) draws 48W when idle. When playing rock music at -20 db (wall shaking, unhealthy loud level in my small room) using Dobly Music ProLogic II, the receiver averaged 55W and peaked at 75W every so often. Does this really mean that my speakers (M22's, VP150, QS4's) are only using between 7 and 25W? If so, this is the best use of 25 watts I have ever known grin !

When playing movie soundtracks, the receiver used between 50 and 68W, even during intense action sequences with multiple channels being driven at "theater sound levels."

I then plugged my EP350 subwoofer into the Kill-A-Watt meter. When the sub is in standby mode, it draws 17W from the wall. Once it becomes active but idle, the power draw increases to 28W. Surprisingly, even when playing extremely "bassy" music or movies the power draws stays unchanging at 28W. What gives? The receiver's power draw bounced all over the place during playback, providing the varying power levels the speakers were requiring. I would have expected the subwoofer's power draw to change as well when it was working hard. If anyone can explain to me why the subwoofer's power draw does not change, I would appreciate it.

As a final note to anyone who is interested, I also checked the power consumption of my 65" Panasonic plasma (I think the model number is TC-P65S1). The manual states that the maximum power consumption of the TV is over 700W. I found that the power required varied from 75W to 375W depending, of course, on what was onscreen. The average power use was around 250W.

Re: Interesting Observation/Subwoofer Power
BWeasner #324950 10/06/10 03:58 PM
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My guess on the TV, is that the 700W would be peak wattage with all of the brightness options turned up all the way.

Re: Interesting Observation/Subwoofer Power
CatBrat #324963 10/06/10 05:03 PM
Joined: Dec 2003
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J
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J
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The sub draws less than a receiver would as it is only doing one thing so the receiver's input supply jumping around is no surprise considering what it is doing, audio and video. I would also suspect the amp section/power supply of the receiver is not as robust as the subs amp so it has to throttle the power intake to maximize use. While the subs amp section needs a minimum of 28 to provide the SPl you are demanding from it. I am sure if you turned up the volume on the subs amp the draw would go up as well.


Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70
Re: Interesting Observation/Subwoofer Power
BWeasner #325070 10/07/10 01:32 AM
Joined: May 2002
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Brandon, your results in general reflect the real-world realities of amplifier power use, which are often imagined to be far higher than actually required in typical home use.

No, the 75 watt max reading above the 48 watt idle reading doesn't mean that only about 25 watts of additional consumption are being used for maximum speaker output. The watts at idle are being "wasted" to keep things ready. When the speakers are actually being driven, that power that was used at idle is put to use in actual acoustic output. So, much of the 75 watt consumption(some goes for auxiliary circuits other than amplification)is for amplification for the speakers.

As to the observation about the sub consumption remaining at 28 watts, that does not compute. If the sub is actually outputting a high level of sound(are you sure?), more power consumption above the idle level will sometimes be required.


-----------------------------------

Enjoy the music, not the equipment.



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