# idea for (new?) metric?

Discussion in 'Sound Science' started by AutumnCrown, Sep 23, 2018.
1. When looking at FR response, I find it difficult to estimate how much of the total energy of a headphone a given band (e.g. 7-10 khz) represents. For example, the SR009 and LCD3's FR's look fairly similar overall, when in fact one is rolled off a bit on top, and the other is a bit bright.

Would it be easy to represent the FR response as a table where the percent of energy for a given band is given? EG:

20-60 hz 12%
61-120 hz: 10%
121-200 hz:12%
201-400 hz: 10%
...and so on to 20 hz or so

Perhaps this could be normalized against the harman target response, so for a headphone that met the response perfectly it would read

20-60 hz +0%
61-120 hz: +0%
121-200 hz: +0%

20-60 hz +5%
61-120 hz +5%
121-200 hz +5%

It would be surprised if this hasn't been thought of before. But it seems like it would make reading FR responses easier. Sort of like having the "area under the curve" in statistics be in a chart, because it's a lot of information to remember. And that's for a single curve. It would also help in comparing graphs from different measurement systems and with different compensations.

2. Contributor
so all in all how many values do you figure this thing would have? 10? 15? you expect somebody who's lost by 2 FR to make sense of that easily? I just don't see it.

IMO everybody is much better served with the basic tool of placing 2 headphone curves on the same graph. maybe matching the levels at 1khz could be adjusted on demand as sometimes headphones could have a big area with similar response but the difference at 1khz shifts everything and may give the wrong subjective idea. but it's still IMO the most explicit way of showing differences in FR.

sam6550a likes this.
3. You are right they do look similar except that STAX bass lower in the subs. Interesting thing is, they don't sound similar. I find STAX do not sound like how the measurement are represented. Treble sounds more prominent than the Audeze, and Audeze seems more representative of the response. You will find that the bass response is different as well. Stats tend to not have such a low-end body.

Despite the graphs, expect different sounding headphones.

Last edited: Sep 23, 2018
sam6550a likes this.
4. It depends on the signal itself how much "energy" you get. Bass-heavy music gives you more "energy" at low frequencies.

Energy is the integral of power over time. One second of one watt [W] power equals 1 Ws or one joule [J] of energy. So if you listen to a record 10 minutes instead of 1 minute you get probably 10 times more (assuming the power of the music is pretty constant) energy blasted at your ears.

Mathematically frequence response it derived from impulse response (taking the magnitude value of the complex-valued impulse response). Impulse response describes a linear time-invariant (LTI) system completely. Frequence response loses the phase information of the impulse response and does not describe a LTI system completely. Two different systems can have identical frequence responses, but completely different phase responses so that the systems sound different.

Linear system means that the following are true:

f(x+y) = f(x) + f(y)
f(a*x) = a*f(x)

Time-invariance means that the system doesn't change in time. In practice everything changes, but usually slow enough for the assumption to hold. In other words, your headphone sounds today the same it did yesterday, but maybe not 10 years from now. 100 % linear systems hardly exists, but audio products are often linear-enough to appear completely linear to our ears.

Our hearing is very complex and it isn't easy to come up with numbers that predict how bright a pair of headphone sounds.

5. It seems a serious problem to me that there are infinite different measurement systems and configurations. Ideally, if this system were implemented by measurers, it would make all of them comparable to each other without any superimposition or adjustment.

6. Contributor
getting differences can't be helped so just forget about reasoning with that as a starting point. obviously we'd all want a complete perfect standard that's accurate within 0.5dB from 20hz to 20khz, but even the 2 drivers of the same headphone don't have that consistency, let alone measurements of them.