There are lots of sites that provide headphone measurements. However, they all use measurement equipment and protocols ("rigs") that differ from those that were used by Harman to derive the Harman target curve. Sean Olive pointed this out in his twitter feed, linked on ASR
This means that the Harman target curve, as published by Harman, cannot be simply be plotted on headphone FR charts that were produced using a different measurement rig - yet this is exactly what sites are doing. The reason is that the Harman target curve would be shaped differently if plotted correctly. Perhaps this explains why following published EQ recommendations based on this invalid comparison end up making the headphones sound worse (or only marginally better).
Nevertheless, there is a strong desire to be able to compare measured headphones to the Harman target curve. One idea is to compare measurements made on the test rig vs Harman-provided measurements. Unfortunately, the conversion factor isn't simple, according to experts on this forum. Another way would be to re-measure a series of headphones on the new test rig to create a rig-specific Harman target. Harman has apparently done this, but they're not sharing the new curve (for obvious reasons).
But what if we could do what Harman is doing at home? All we would need to do is take headphones that have known Harman measurements and measure them on our own test rigs. And then to make the target curve customized for our own ears/headphones, we could use our own ears. Could this work?
To test this possibility, I did the following:
1) Utilized REW to measure a set of AKG 701 and JBL 701BT headphones, both of which have Harman-published measurements that sort of match the Harman-published target curve. Each headphone was measured 5 times, strange curves discarded, and averaged in REW. I used in-ear binaural headphones that fit at the opening of my ear canal.
The product is the Sound Professionals SP-TFB-2 (no affiliation), photo from their website.
2) I then took the Harman-published measurements of these two headphones (such as the one above), as measured on the Harman rig, and generated a CSV file to "correct" the headphone response to the Harman target.
3) Using REW's A-times-B function, I then re-created the Harman target on my own test rig. In theory, this curve could be used to make rough corrections against with any other headphone I measure, with some limitations.
Results:
Surprisingly, using this method, the two extrapolated Harman targets agreed:
50Hz-200Hz: -2dB to 1.5dB <-- and likely seal-related and something easily adjusted to taste anyway
200Hz-600Hz: -1.5dB to 0dB
600Hz-2khz: 0dB to 3dB
>2khz: pretty bad, but people usually don't equalize a whole lot above this range anyway other than perhaps applying a treble tone control or EQ'ing out a peak
Blue is based on the 710BT, and green is based on the 701.
Ideally, I would have more Harman-measured headphones that I could do this with.
However, based on this quick test, it seems like between 200Hz and 2kHz, the likely range of interest of EQ anyway, this could be a way to correct headphones to closer match the Harman curve with more customization.
Sharing this in case there's interest.
This means that the Harman target curve, as published by Harman, cannot be simply be plotted on headphone FR charts that were produced using a different measurement rig - yet this is exactly what sites are doing. The reason is that the Harman target curve would be shaped differently if plotted correctly. Perhaps this explains why following published EQ recommendations based on this invalid comparison end up making the headphones sound worse (or only marginally better).
Nevertheless, there is a strong desire to be able to compare measured headphones to the Harman target curve. One idea is to compare measurements made on the test rig vs Harman-provided measurements. Unfortunately, the conversion factor isn't simple, according to experts on this forum. Another way would be to re-measure a series of headphones on the new test rig to create a rig-specific Harman target. Harman has apparently done this, but they're not sharing the new curve (for obvious reasons).
But what if we could do what Harman is doing at home? All we would need to do is take headphones that have known Harman measurements and measure them on our own test rigs. And then to make the target curve customized for our own ears/headphones, we could use our own ears. Could this work?
To test this possibility, I did the following:
1) Utilized REW to measure a set of AKG 701 and JBL 701BT headphones, both of which have Harman-published measurements that sort of match the Harman-published target curve. Each headphone was measured 5 times, strange curves discarded, and averaged in REW. I used in-ear binaural headphones that fit at the opening of my ear canal.
The product is the Sound Professionals SP-TFB-2 (no affiliation), photo from their website.
2) I then took the Harman-published measurements of these two headphones (such as the one above), as measured on the Harman rig, and generated a CSV file to "correct" the headphone response to the Harman target.
3) Using REW's A-times-B function, I then re-created the Harman target on my own test rig. In theory, this curve could be used to make rough corrections against with any other headphone I measure, with some limitations.
Results:
Surprisingly, using this method, the two extrapolated Harman targets agreed:
50Hz-200Hz: -2dB to 1.5dB <-- and likely seal-related and something easily adjusted to taste anyway
200Hz-600Hz: -1.5dB to 0dB
600Hz-2khz: 0dB to 3dB
>2khz: pretty bad, but people usually don't equalize a whole lot above this range anyway other than perhaps applying a treble tone control or EQ'ing out a peak
Blue is based on the 710BT, and green is based on the 701.
Ideally, I would have more Harman-measured headphones that I could do this with.
However, based on this quick test, it seems like between 200Hz and 2kHz, the likely range of interest of EQ anyway, this could be a way to correct headphones to closer match the Harman curve with more customization.
Sharing this in case there's interest.