With reference to a number of posts on page 2 of this thread, and latterly @Bwaze 's post above, I was interested in making a few "real world" measurements myself, just because I wanted improve my own understanding of these measurements, and what might going on in the tests.
I do not own an Audio Precision analyser, or anything remotely similar, so I am not able to repeat or challenge the measurements made by ASR, Hifi News or anyone else. But I do have a multi meter.
So, I connected some speaker plugs the cables on my multi meter, plugged it into the spare terminals on one speaker, ran a continuous 10kHz test tone, and checked the voltages at different gains on the Devialet. Initially I checked the voltage at very low gains, and then calculated the wattage this equated to. Reasonably confident that power levels were low enough, I then increased the gain. The first thing I discovered is my multi-meter is not that accurate with low voltage. You can set it for different voltage ranges, I used the 2V range and 20V range. As an example, the reading with 10Khz at -30dB was 0.1V using the 20V range, or 0.38V using the 2 V range. So one thing I have learnt is that I probably need to buy a better multi-meter, although my old one has served me well for what I need. I then repeated the above using a 15kHz tone. (which I was quite please to note that I could hear very clearly)
What I was particularly interested in understanding was exactly how much power a 10kHz or 15kHz test tone would require at anything up to 0dB gain.
To calculate the power, I needed to know the resistance that the Blades are presenting at the particular frequency. I do not have an impedance curve for the Blade, but Stereophile have published one for the Blade 2, which I think has the same HF driver, so this should be near enough. Here I conservatively took the impedance at 10kHz as 5 ohms, and at 15kHz 4.5 ohms.
These are the results:
10kHz tone:
-30dB gain, 0.08V, approximately 0.001W
-20dB gain, 0.38V, approximately 0.03W
-10dB gain, 1.44V, approximately 0.41W
0dB gain, 5.8V, approximately 5.8W
15kHz test tone:
-30dB gain, 0.02V, approximately 0.0001W
-20dB gain, 0.21V, approximately 0.01W
-10dB gain, 0.88V, approximately 0.17W
0dB gain, 4.0V, approximately 3.6W
In an earlier post @ogs made the point "Your Blades are quite sensitive at 91dB (2.83V/1m). 90dB SPL at your listening position would be around 2 watts..." In terms of normal listening, I agree with ogs here. Normally I use HQPlayer with upsampling, and run HQPlayer at -4 dB to prevent issues with inter-sample clipping. Even with this, I am usually at -20dB or lower, and rarely go above -10dB even with "quiet" recordings played loudly. I mention this because with the above figures, HQPlayer was set to 0.0dB, so even with a level of gain way above what I would ever normally use, the highest wattage I have measured is 5.8W for the HF tone. In normal use, running my system with 0dB gain would lead to very high volumes, certainly enough to cause hearing damage, possibly enough to cause speaker damage.
This makes me think that to get higher wattages during the kind of tests ASR and Stereophile are doing, you would need to run a very high voltage, equivalent to huge positive gain, into the Devialet's analogue input. This is the only way I can see how you could get to 20 or even 10 watts. Have I got this right? If so, I assume the Devialet sees the high voltage on the analogue input, it thinks this is wrong, and shuts down. I am speculating a little here, so would be interested in the views of others here.
In practical terms, say if you wanted to use your Devialet for something like listening to music at a reasonably high volumes, I would say the above numbers suggest this testing anomaly is not of too much concern. Thankfully, trying this test did not cause my Devialet to shut down, and it has not fried my speakers. For this I am very grateful (I was a little worried about trying this) and I shall now proceed to using my Devialet for the above mentioned purpose.
I do not own an Audio Precision analyser, or anything remotely similar, so I am not able to repeat or challenge the measurements made by ASR, Hifi News or anyone else. But I do have a multi meter.
So, I connected some speaker plugs the cables on my multi meter, plugged it into the spare terminals on one speaker, ran a continuous 10kHz test tone, and checked the voltages at different gains on the Devialet. Initially I checked the voltage at very low gains, and then calculated the wattage this equated to. Reasonably confident that power levels were low enough, I then increased the gain. The first thing I discovered is my multi-meter is not that accurate with low voltage. You can set it for different voltage ranges, I used the 2V range and 20V range. As an example, the reading with 10Khz at -30dB was 0.1V using the 20V range, or 0.38V using the 2 V range. So one thing I have learnt is that I probably need to buy a better multi-meter, although my old one has served me well for what I need. I then repeated the above using a 15kHz tone. (which I was quite please to note that I could hear very clearly)
What I was particularly interested in understanding was exactly how much power a 10kHz or 15kHz test tone would require at anything up to 0dB gain.
To calculate the power, I needed to know the resistance that the Blades are presenting at the particular frequency. I do not have an impedance curve for the Blade, but Stereophile have published one for the Blade 2, which I think has the same HF driver, so this should be near enough. Here I conservatively took the impedance at 10kHz as 5 ohms, and at 15kHz 4.5 ohms.
These are the results:
10kHz tone:
-30dB gain, 0.08V, approximately 0.001W
-20dB gain, 0.38V, approximately 0.03W
-10dB gain, 1.44V, approximately 0.41W
0dB gain, 5.8V, approximately 5.8W
15kHz test tone:
-30dB gain, 0.02V, approximately 0.0001W
-20dB gain, 0.21V, approximately 0.01W
-10dB gain, 0.88V, approximately 0.17W
0dB gain, 4.0V, approximately 3.6W
In an earlier post @ogs made the point "Your Blades are quite sensitive at 91dB (2.83V/1m). 90dB SPL at your listening position would be around 2 watts..." In terms of normal listening, I agree with ogs here. Normally I use HQPlayer with upsampling, and run HQPlayer at -4 dB to prevent issues with inter-sample clipping. Even with this, I am usually at -20dB or lower, and rarely go above -10dB even with "quiet" recordings played loudly. I mention this because with the above figures, HQPlayer was set to 0.0dB, so even with a level of gain way above what I would ever normally use, the highest wattage I have measured is 5.8W for the HF tone. In normal use, running my system with 0dB gain would lead to very high volumes, certainly enough to cause hearing damage, possibly enough to cause speaker damage.
This makes me think that to get higher wattages during the kind of tests ASR and Stereophile are doing, you would need to run a very high voltage, equivalent to huge positive gain, into the Devialet's analogue input. This is the only way I can see how you could get to 20 or even 10 watts. Have I got this right? If so, I assume the Devialet sees the high voltage on the analogue input, it thinks this is wrong, and shuts down. I am speculating a little here, so would be interested in the views of others here.
In practical terms, say if you wanted to use your Devialet for something like listening to music at a reasonably high volumes, I would say the above numbers suggest this testing anomaly is not of too much concern. Thankfully, trying this test did not cause my Devialet to shut down, and it has not fried my speakers. For this I am very grateful (I was a little worried about trying this) and I shall now proceed to using my Devialet for the above mentioned purpose.
1000 Pro - KEF Blade - iFi Zen Stream - Mutec REF10 - MC3+USB - Pro-Ject Signature 12
