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Why some headphones are more revealing than others ?

post #1 of 29
Thread Starter 

IHi All,

While reading up on MP3 compression, I read through this concept: Auditory masking.

What this basically means is that if two sounds (tones) are played simultaneously, the tone with higher intensity will "mask" the tone at lower intensity, as long as they are within a few Hz of each other.

The listener will be unable to distinguish between these two, and hear the combination of the two tones.

For illustration, take a look:

img042.gif

 

This means that even if I remove these 'quiet' sounds from the signal, the listener will not notice. Hence the signal can be 'compressed', to take up less space. This is the concept used in MP3, and the reason why its hard to distinguish between high bitrate MP3 and lossless.

 

But here's where it gets interesting. Masking follows a pattern, based on the Masker vs Signal Frequency:

Masking-Threshold-500x269.png

 

Here, the masker is centered at ~220Hz.

The curves represent the threshold of this masking, both in intensity, and as it varies with the frequency.

Also represented is the auditory threshold, the point below which any such signal is inaudible.

 

Take a look at this pattern as well, this represents the variation in the masker intensity:

Maskingpatterns_sp11.jpg

 

Now, consider this from the point of view of Frequency Response of an Amp/Headphone/Speaker, taking the two diagrams above as example, and a typical frequency response of Shure SE425 vs Etymotic ER-4S:

 

graphCompare.php?graphType=0&graphID[]=2741&graphID[]=743

 

If you see at ~200Hz, the two curves differ by about 5dB.

 

I can think of the following implications:

  • If there is some signal just at the threshold, and being masked, elevating it by 5dB will result in it becoming discernible, meaning you'll hear something you might not have heard with other headphones. Thus, the Shures will be revealing in the low/mids, while the Etymotics in the highs.
  • Conversely, the attenuation of the signal at high frequencies also means the masker will be attenuated, and based on the curves, it'll reduce the masking effect as well. Hence, some of the signal being masked at other (higher/lower) frequencies, may be revealed.
  • If compression algorithms like MP3 can remove these masked signals, does that mean the possibility of hearing these masked signals is also reduced? In lossless that should not happen.

 

So, I put forth the following questions:

  • Why are some headphones more revealing? Does it have to do with this phenomenon? Revealing here means you hear sounds you've never heard before, missed on other headphones.
  • How can we enjoy our music fully? Headphones and speakers with a large variation in the frequency response from the original have the effect of revealing some sounds, and masking others, so there's no perfect sound. We are always hearing something at the expense of missing something else.
  • Should we be compressing our music? Even if the compression model is based on safe assumptions, signals that could've been heard are lost by compression.
  • Do we need to buy a few headphones with varying response? If every headphone hides some, reveals some, then it seems you need both kinds of headphones.
  • How much role does music production have to play? Recording music is different from playback, as the levels of different instruments and sounds are adjusted after recording.

 

Also, please feel free to correct me if I'm wrong.


Edited by proton007 - 5/15/12 at 6:37pm
post #2 of 29
Thread Starter 

Another question for discussion. These masking patters are based on tests conducted on various individuals.

It is safe to assume that some of us might have variations. Does this mean the same music will sound different to some?

post #3 of 29
You can actually play around with this concept with an EQ; set the volume relatively low and very aggressively (we're talking like 12dB or 18dB steps) adjust individual bands. It's a very different perspective on your music.

Also consider that when something is mastered, this happens even without data compression - if I have two sounds and one is louder, it "wins" - and a lot of material is put together like that.

Finally, in terms of revealing-ness of headphones, this may be a factor, but I'm more inclined to believe that resonance and transient response play a bigger factor. In other words, how fast can the driver recover. A lot of headphones have a huge boost in the treble/upper-mids that "fakes" clarity/revealingness and is simply brightness; the Beyer T70 is an example here. Compared to something like the ESP/10, which rolls off pretty dramatically over 7khz, yet is very detailed/revealing simply because the driver can recover very quickly.

Regarding individual variation - yes it's safe to assume it exists, but don't project it. We all do experience the world at least a little differently, and it can be as simple as mood congruency or as complicated as physical variation or disability.

Here's some more info:
http://www.physics.mcgill.ca/~guymoore/ph224/notes/lecture13.pdf
Edited by obobskivich - 5/15/12 at 5:53pm
post #4 of 29
Thread Starter 
Quote:
Originally Posted by obobskivich View Post

You can actually play around with this concept with an EQ; set the volume relatively low and very aggressively (we're talking like 12dB or 18dB steps) adjust individual bands. It's a very different perspective on your music.

Yes that can be tried, better yet with neutral headphones to prevent bias.

 

Quote:
Originally Posted by obobskivich View Post

Also consider that when something is mastered, this happens even without data compression - if I have two sounds and one is louder, it "wins" - and a lot of material is put together like that.

Well, yes. But I assume that even though the two sounds cannot be distinguished, they should still be recorded in the signal, right? The seemingly 'inaudible' sound will be embedded in the signal. 

But if the sounds are individually put together, which is the case with a lot of commercial music nowadays, then I guess its true.

For other, live style recordings, I hope its not true...

 

Quote:
Originally Posted by obobskivich View Post

Finally, in terms of revealing-ness of headphones, this may be a factor, but I'm more inclined to believe that resonance and transient response play a bigger factor. In other words, how fast can the driver recover. A lot of headphones have a huge boost in the treble/upper-mids that "fakes" clarity/revealingness and is simply brightness; the Beyer T70 is an example here. Compared to something like the ESP/10, which rolls off pretty dramatically over 7khz, yet is very detailed/revealing simply because the driver can recover very quickly.
Regarding individual variation - yes it's safe to assume it exists, but don't project it. We all do experience the world at least a little differently, and it can be as simple as mood congruency or as complicated as physical variation or disability.

 

Thats a good point there. I believe that amplifying certain frequencies is bound to mask others, however small the effect may be.

The recovery time also relates to how well the driver can represent individual frequencies, so I guess that headphones with poor transient response amplify this masking.

I get what you mean by clarity/revealingness, but by (genuine)revealing, I mean sounds you might not have heard before, that seem to pop up and grab attention.

 

I also read somewhere this has something to do with harshness of sound. If a headphone can reproduce frequencies more accurately (something like the HD800), the perceived loudness will be higher (from the article). Add to that the dynamics of music, and the combination may not sound very pleasing (some don't like the HD800 for this reason).

On the other hand, minor cover ups in the frequency resolution may make the sound smoother, I think. 


Edited by proton007 - 5/15/12 at 6:37pm
post #5 of 29
There's reason it's called "unforgiving" - absolute perfect and brutally honest playback is not fun for listening/music enjoyment. There's some people who dig it, but by and large I think the majority of people like a bit of "flow" to their music.

I don't think accuracy has to be the antithesis of enjoyability; 'stats can produce frequencies very accurately and don't sound harsh or aggressive while doing it. Just like there's some very "fun" cans that can still pick out details.
Edited by obobskivich - 5/15/12 at 9:41pm
post #6 of 29
Thread Starter 

Yeah, I guess thats why some earphones designed for stage monitoring are not entirely fun. They make poor recordings sound bad.

I'm surprised how little most buyers (including me) know before they go out spending money on equipments. Achieving perfection in the reproduction chain is negligible in effect when compared to the phenomenon that start playing a role after that sound is reproduced.

post #7 of 29
Quote:
Originally Posted by proton007 View Post

Yeah, I guess thats why some earphones designed for stage monitoring are not entirely fun. They make poor recordings sound bad.

They're just doing their job. etysmile.gif
post #8 of 29
Thread Starter 

Thats true.

A few points I noted from the article:

  • Whether a soft tone shows up underneath a loud tone can vary from subject to subject, particularly on their level of musical training.

        I wonder what is meant by that ? Someone who is trained in classical music ?

  • One can make plots of what “typical” listeners can or cannot hear.

        Special emphasis on typical.

  •  Masking  is  stronger  on  the  high  frequency  side  of  the  loud  tone  than  on  the  low frequency side.  That is, a deep, loud tone covers up high pitched, soft tones, but a high pitched, loud tone does not cover up deep, soft tones very much.

        I guess this is what most people mean when they say "muddier". Bass heavy headphones can have this effect I presume.

  • A loud tone played only in one ear can mask a soft tone played only in the other ear.

 

 

This is a bit of a dilemma. On one hand we strive for perfection, accuracy. This is the marketing mantra used by so many audiophile companies out there.

If perfection is not what we find pleasing, and ignorance is bliss, then it defeats the whole point of getting closer to the real-life sound.

post #9 of 29
Quote:
Originally Posted by proton007 View Post

Thats true.
A few points I noted from the article:
  • Whether a soft tone shows up underneath a loud tone can vary from subject to subject, particularly on their level of musical training.
        I wonder what is meant by that ? Someone who is trained in classical music ?
  • One can make plots of what “typical” listeners can or cannot hear.
        Special emphasis on typical.
  •  Masking  is  stronger  on  the  high  frequency  side  of  the  loud  tone  than  on  the  low frequency side.  That is, a deep, loud tone covers up high pitched, soft tones, but a high pitched, loud tone does not cover up deep, soft tones very much.
        I guess this is what most people mean when they say "muddier". Bass heavy headphones can have this effect I presume.
  • A loud tone played only in one ear can mask a soft tone played only in the other ear.


This is a bit of a dilemma. On one hand we strive for perfection, accuracy. This is the marketing mantra used by so many audiophile companies out there.
If perfection is not what we find pleasing, and ignorance is bliss, then it defeats the whole point of getting closer to the real-life sound.

On the first one, I think by "trained" they mean trained listeners. Typical is based on deviation, and the other two I just see as evolutionary traits (how many dangerous things are very high pitched and loud? how many of them come at you head on?).
post #10 of 29
Quote:
Originally Posted by obobskivich View Post

You can actually play around with this concept with an EQ; set the volume relatively low and very aggressively (we're talking like 12dB or 18dB steps) adjust individual bands. It's a very different perspective on your music.
Also consider that when something is mastered, this happens even without data compression - if I have two sounds and one is louder, it "wins" - and a lot of material is put together like that.
Finally, in terms of revealing-ness of headphones, this may be a factor, but I'm more inclined to believe that resonance and transient response play a bigger factor. In other words, how fast can the driver recover. A lot of headphones have a huge boost in the treble/upper-mids that "fakes" clarity/revealingness and is simply brightness; the Beyer T70 is an example here. Compared to something like the ESP/10, which rolls off pretty dramatically over 7khz, yet is very detailed/revealing simply because the driver can recover very quickly.
Regarding individual variation - yes it's safe to assume it exists, but don't project it. We all do experience the world at least a little differently, and it can be as simple as mood congruency or as complicated as physical variation or disability.
Here's some more info:
http://www.physics.mcgill.ca/~guymoore/ph224/notes/lecture13.pdf

clarity comes from boost of air(14k and up). anything diffused-field or free-field will either have slight bump or ''flat'' at 14khz and then take dive/roll off after that. the boost at 14k will also will help bass dispersion as well and better imaging. most stats and iem's do the same thing (giving slight bump at 14k). the brightness and annoyance(well atleast for me) is when anything from 7/8k-10k is bumped/peaked too high. around there should be dropped tad bit.
post #11 of 29
Thread Starter 
Quote:
Originally Posted by RexAeterna View Post


clarity comes from boost of air(14k and up). anything diffused-field or free-field will either have slight bump or ''flat'' at 14khz and then take dive/roll off after that. the boost at 14k will also will help bass dispersion as well and better imaging. most stats and iem's do the same thing (giving slight bump at 14k). the brightness and annoyance(well atleast for me) is when anything from 7/8k-10k is bumped/peaked too high. around there should be dropped tad bit.

 

Possible, but I feel 'clarity' should not be confused with 'revealing'. There are plenty of IEMs/Headphones that roll off frequencies beyond 10k, but highlight the mids.

Most IEMs/Headphones tend to attenuate high frequencies. (i.e. they go below 0 dB).

post #12 of 29
Quote:
Originally Posted by proton007 View Post

Possible, but I feel 'clarity' should not be confused with 'revealing'. There are plenty of IEMs/Headphones that roll off frequencies beyond 10k, but highlight the mids.
Most IEMs/Headphones tend to attenuate high frequencies. (i.e. they go below 0 dB).

Yeah, I checked a number of graphs for headphones that people commonly call "airy" or "detailed" (some 'stats, ATH-AD series, etc) and I think Rex is onto something with the 14k thing. It's still under 0 dB, but there's a second rise around 12-16k for most of them.

That said, there's stuff like the ESP/10 and HD 600 that completely foul that theory, because both of them are very detailed, revealing, etc and lack such a bump. So I think transient response comes into play as well (in other words, despite lacking a lot of treble, these are both very "quick" headphones with clean CSDs).
post #13 of 29
Thread Starter 

I found this link describing the terms used to describe speakers : http://www.diyaudioandvideo.com/FAQ/Sound/

About the high frequency peak, it seems a characteristic of coil based drivers.

The effect is airy because of how we perceive high frequency reflections, I think.(http://www.crutchfield.com/S-vdXFKNGw9Ff/learn/learningcenter/home/speakers_roomacoustics.html?page=3)

High frequency sounds have much smaller wavelength compared to the room dimensions, and so will bounce around. A small amount of reflection (too large sounds as echo) will cause that small delay (due to reflection) to sound open or airy. 

post #14 of 29
Reflections will get you into this:
http://en.wikipedia.org/wiki/Haas_effect (note that I don't think you can do this with headphones).

I'm not saying you or Rex are right or wrong; it's something I hadn't really noticed or thought about in measurements. Will have to do some more reading.
post #15 of 29
Thread Starter 

Maybe something to do with decay timings. But its just a guess. Need to get more info, as you say.

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