Frequency Response Graphs- Physical Interpretation from measurements ??

[mahajanrahul]

Hi..
 
I was looking at the frequency response graph of (Sennheiser HD202, AKG k712 and Hifiman He-400) and came across very unusual thing. The graph was showing the low end response of HD202 to be less than K712 and He-400 which according to me should not be the case as they are open headphones. From what i can recall HD202 have very much audible mid-bass and sub-bass which i don't
think either of these can provide with that much impact. Are these measurements true/ false/ mean something else??? 
 
 
 

Thanks for replies...

 

[billybob_jcv]

When you ran your own listening, how did you ensure that you exactly volume matched between your tests? These graphs are normalized so that they all pass through zero at 1000 Hz. That means that the curves are all exactly the same volume level at 1000 Hz. It is very, very unlikely that your casual testing can achieve this. It is possible that in your own listening, you subconsciously increase the volume until the higher frequencies match. If you do that, then because the HD202 has the typical "Sennheiser Veil" in the treble, you will be shifting the entire HD202 curve up, and in the process, the bass moves up.

Secondly, what many people think of as "bass" in songs is not nearly as low in frequency as they might think. I have read elsewhere that a kick drum peaks at ~50-60Hz. The HD202 bass peaks at 80 Hz, and that might be what you are actually hearing in most of your songs. The HD202 falls off below 50 Hz.

 

[KG Jag]

Don't think these graphs measure "impact".  The bass on some cans is deep (extended) but fast (quick decay).
 
They (at least this type of graph) certainly don't measure sound stage, clarity, resolution or detail.
 
Graphs, for me, are a tool.  They are usually helpful, but sometimes are misleading.  My ears give the final exam.

 

[mahajanrahul]

When you ran your own listening, how did you ensure that you exactly volume matched between your tests? These graphs are normalized so that they all pass through zero at 1000 Hz. That means that the curves are all exactly the same volume level at 1000 Hz. It is very, very unlikely that your casual testing can achieve this. It is possible that in your own listening, you subconsciously increase the volume until the higher frequencies match. If you do that, then because the HD202 has the typical "Sennheiser Veil" in the treble, you will be shifting the entire HD202 curve up, and in the process, the bass moves up.

Secondly, what many people think of as "bass" in songs is not nearly as low in frequency as they might think. I have read elsewhere that a kick drum peaks at ~50-60Hz. The HD202 bass peaks at 80 Hz, and that might be what you are actually hearing in most of your songs. The HD202 falls off below 50 Hz.

1. This means if i equalize the volume so that at 1000 Hz all cans have the same loudness level, then akg and hifiman will give me more audible low frequencies (sub-bass and mid-bass both) than hd 202 ??
2. If i equalize the volume using my player say (from 75%- 80%) for all headphones then it would serve as a reference for me...so if i do that then also it will give me same measurements as i have increased the volume levels for all cans by equal amount given the senstivity is same for all headphones?  

 

[billybob_jcv]

1. The bass response should match the curves you see more closely.

2. Humans are not very good at volume matching by ear. 1 dB is defined to be the smallest difference in sound the average human ear can discern - according to Wikipedia, this is roughly equivalent to a mosquito that is 3 meters away. However, this minimum level actually varies with frequency. There is a concept called the "equal loudness contour" that describes this perceived variation:




What this tells us is that humans do NOT perceive low frequencies nearly as well as we do sounds around 2 KHz. This is why calibrated dummy heads in sound chambers are used to take measurements. Your ears can be fooled quite easily.