Room Acoustics

Should You EQ to the Harman Target Curve?

Before a child is born, parents agonize over a name. They know that if they choose wrong, that child could suffer devastating social consequences. This is true of many things in life. Give a product or concept the wrong name and the name will overtake the meaning. This seems to be the case with the Harman Target Curve. Many people feel that the Harman Target Curve is some standard to which they should EQ. This is not the case and is generally inadvisable. Let’s discuss!

Author’s Note:

This article stems from a discussion I had with Rob H. on the AV Rant podcast. Check out the full discussion here.

What is the Harman Target Curve?

The Harman Target Curve is a model of what to expect if you put a very accurate speaker in a room and measured its response. The process used to derive this curve is detailed in the paper, “The Measurement and Calibration of Sound Reproducing Systems” (link to full paper) by Dr. Floyd Toole. The curve, taken from the paper, is shown below:

Looking at the X-axis, we see the frequency in Hz from 20 to 20,000 (the full range of human hearing). The Y-axis shows the relative change in dB. As we said, this curve predicts how a very accurate speaker will measure in a room. Very accurate means that anechoically, the speaker measures flat (the dotted line in the graph above best shows a flat response). The roll-off at the top end (right side of the graph) is because of air attenuation. This means that those higher frequencies are losing power because of the distance between the speaker and the microphone). The left side is more interesting.

Bass and the Harman Target Curve

The left side of the graph shows two dashed lines and a grey area above the dotted line that follows the 0dB mark on the Y-axis. The thin dashed line is for highly reflective cinemas and the bold dashed line is for “typically reflective” cinemas. The grey area shows that other rooms (ones that are more or less reflective) would fall into that area. No room falls below the 0dB line as bass will not be reduced in a typical home theater (or anechoic chamber for that matter). It is only boosted by being reflected around the room.

What Does the Harman Target Curve Mean?

It’s important to understand that the curve is descriptive and not prescriptive. The Harman Target Curve was never meant as a goal for your EQ. It was designed to answer one very simple question. “If you put very linear speakers in a normal room, how would they measure?”

The Harman Target Curve shows that, in a range of rooms, the treble is predictably reduced by air attenuation. It also shows that the bass is boosted (less predictably) by room reinforcement. If you were to measure your speakers in the same way that Harman did, you should expect a graph to look like the Harman Target Curve.

Assuming your speakers were accurate.

If you see another line, or one that does not look very much like the Harman Target Curve, then your speakers are probably not as accurate as you thought. Or your room is really weird (more absorptive or reflective at certain frequencies). Or something else. In the end, the Harman Target Curve is NOT a goal for your EQ, it is a predictive model for how accurate speakers sound in traditional rooms.

Wrap Up

Trying to EQ your system to the Harman Target Curve is exactly wrong. The goal of the Harman Target Curve is to give you some insight into how your speakers would measure in an anechoic chamber. If your un-EQ’ed speakers measure close to the Harman Target Curve (using the same measurements that Harman used), then they would probably measure relatively flat in an anechoic chamber.

You would then want to EQ to a curve of your choosing. The point of adding room treatments and using room correction is to overcome the effects of the room on our sound. Using the Harman Target Curve as your EQ goal just reintroduces the room effects back into your sonic experience! Instead, you should be using your EQ to create a more accurate sound that also sounds good to you. That might be a flat line, it might look exactly like the Harmon Target Curve, or it might look totally unique. We would recommend a flat line. From there, you can adjust the curve (generally boosting the bass slightly) to your personal taste.

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