Originally Posted by tezster
What I would be interested to learn, is whether anyone has tried to run one of these AVRs under conditions which forces it to draw a lot of power i.e. outputting a test tone to all channels at reference level, using inefficient speakers, for the purposes of recording an audible difference with the ECO mode set to ON vs. OFF.
Great point. I decided to do a couple of tests to see
Test #1 – continuous sine waves: Using REW, a UMIK-1 microphone, and a Marantz SR7010 driving 7 channels of Goldenear SuperSat 50s/60s speakers, at the listening position, I have verified that even at very high volumes, at 93dB (which +7dB over the 85dB “reference’ level), I saw no real difference of SPL or distortion comparing ECO Mode On versus OFF (AUTO is the same case, but irrelevant since AUTO would be the same as ON).
Test #1 VIDEO illustration:
So in that test, my AVR was driving 7x91dB sensitive speakers to 93dB overall summed, and likely pushing somewhere between 10-20 watts (14w estimated). And it was REALLY REALLY LOUD.
Summary: ECO mode makes no difference with sine waves, so best to leave it ON in this case.
Test #2 – burst tone test: Using REW, a UMIK-1 microphone, and a Marantz SR7010 driving 7 channels of Goldenear SuperSat 50s/60s speakers, at the listening position, I set a 1Khz burst tone that peaks at 106dB, which is right near reference level peak (105dB is 20dB over 85dB reference). In this case, you can clearly and audibly hear a difference between ECO ON vs. ECO OFF. The tone/note changes considerably. I did not notice THD or SPL differences between the two, but mainly because I’m not sure I know how to yet account for them in the burst test procedure. But the sound change is clear. 0:55-1:05 is OFF/AUTO, 1:05 is ON. (Note: for some reason, the very first tone is the series doesn’t sound any different. It’s only the 2nd peak tone and every tone thereafter that sounds different. The only way I can theorize this is that it takes time for the residual high voltage to dissipate, which is achieved on the 1st tone. Since the 1st tone dissipated the extra power in the amplifier, then 2nd tone was limited to whatever the voltage limit is)
Test #2 VIDEO illustration:
So in test #2, my AVR was driving 7x191dB sensitive speakers to 106dB overall summed, which is 16dB over 1w, and likely pushing upwards of 196 watts given a 14X increase in power requirement.
Summary: ECO mode OFF vs ON has a noticeable
difference with peak tones, and it’s best to leave ECO in OFF in this case
So why the conflicting information, where in one case it works fine, but in the other case it doesn’t? Easy answer can be illustrated with the ATTACHED chart and can be simplified with the following phase: “Most movies and music aren’t sine waves, they have dynamic content with peaks and valleys.”
To properly figure out how much amplifier power you need, you have to figure out the maximum volume level you ever want to run at, figure how much power you need at PEAK levels (the same thing as the maximum of the maximum), and then add in all the other components, such as your room, your speakers’ sensitivity, distance from the listening position.
For anyone wanting to deliver 105dB peaks, even using really good (high sensitivity speakers), you still need 10 times the voltage or 100 times the power over 85dB reference for those peaks. Remember, too, that every doubling of distance from the speaker either decreases output by 6dB, or you have to add 6dB of power to get the same levels (4x the power, or double the voltage).
One final thought: my speakers were tested at 1Khz, but even more power is needed for bass. So for those considering ECO Mode to drive full range speakers, or even speakers set to SMALL at crossed over at 80Hz, you may very need considerably MORE power than my 1Khz tone. I may do a 100hz test tone and see at what dB level I can hear a noticeable change in that tone. I would be using the below