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Bass boost affects more than bass

post #1 of 31
Thread Starter 

In my recent review of the iCAN amp I included the following observation in my discussion of the xBass boost that is a feature of that amp:

 

However, it is not just on bass heavy music that this X-Bass feature comes into play, even though the bass boost effect is clearly in the lowest frequencies and does not mess up the mids. I will quote Srajan from a recent review of the Zu Audio Submission sub-woofer on his 6moons.com website as he describes very clearly why low bass matters even with music that has little or no bass frequencies:

 

If you're still out in the cold wondering why one would even want 20Hz bass—surely that's fit only for the boom-truck brigade—the answer is simple. It's not about any rave, disco or reggae excess. It's about scale, soundstaging, ease, color saturation and rhythmic grip when kick/bass drums and related beat makers add weight, kick and pitch intelligibility. It might have been British REL subwoofer firm who first did girl+guitar type dealer demos with and without subwoofer. This demonstrated how recording-venue cues are seemingly associated with very long wavelengths at very low amplitude even on material that's apparently devoid of any real bass. That effect is very real. It's the first thing Martin Gateley, designer of the Wave 40, said when we added the Submission. More scale. Aside from the primitive obvious of more extended bass, the far more impressive transformation related to space and size. Everything instantly grew bigger and deeper. Save for hearing synthesized infrasonic chicanery on ambient and electronic albums which regular speakers can't reproduce fully, the primary benefit of building out the lowest octave thus isn't about more bass per se. It's what mostly instinctual (rather than directly audible) bass adds to dimensionality and participatory involvement.

 

I think the above explains part of what I am hearing with the X-Bass engaged. On some music with a strong low bass component, the effect is obvious and quite enjoyable. But on less bass heavy music, I still hear a fullness and completeness to the sound that perfectly complements the added air and space of the 3D effect (see the review efor more about the 3D efect : http://www.head-fi.org/t/654405/ican-amp-review-a-new-amp-that-gives-you-more-more-bass-more-soundstage-and-more-detail). The two together create a more realistic sense of music being played in a venue instead of inside my head. The added presence in the low frequencies gives the sense of how music pressurizes the air inside the room when using speakers, and without it the music seems thin and lifeless in comparison.

 

I wonder if anyone else experiences the same benefit of a boost in the bass on music that does not have a lot of bass. I do not listen to a lot of bass heavy music, but I still find I prefer having the bass boost turned on when I listen.

post #2 of 31

I don't think quotes from 6moons will get a lot of traction here in sound science.

 

A really really really important aspect of the question at hand is: "How does the specific bass boost circuitry/digital processor affect the frequency response?"

 

If there is zero audio content in the frequency band that is affected by the bass boost, then the is zero difference between bass boost on versus bass boost off. (I guess I ignored the phase response as well, but I  think it is reasonable that any changes in the phase response would be limited to the same frequency band)

 

So, if you're bass boost affects the sound of your "non bassy" music, then even your non-bassy music still has content at some of the same frequencies affected by the bass boost. The effect your hearing is still just the boosting of the lower frequencies in the music.

 

Again, this will depend heavily on what exactly the bass boost does to the audio.

 

Cheers


Edited by ab initio - 7/17/13 at 11:19am
post #3 of 31

So what you're saying basically is that recordings can contain information in the lowest octaves. With that I agree.

 

6moons seems to be talking about a flat response down to 20 Hz while you talk about bass boost.

 

 

From ClieOS' review.

 

 

Yes, generally speaking, boosting bass in bass anemic songs can bring out some low frequency details.

post #4 of 31
Thread Starter 
Quote:
Originally Posted by xnor View Post

So what you're saying basically is that recordings can contain information in the lowest octaves. With that I agree.

 

6moons seems to be talking about a flat response down to 20 Hz while you talk about bass boost.

 

 

From ClieOS' review.

 

 

Yes, generally speaking, boosting bass in bass anemic songs can bring out some low frequency details.


However, a lot of headphones have a response curve like this one for my ESW9s:

 

 

So the bass boost is just putting that low frequency info back that was missing. And it seems there is a lot of info in that range that creates the sense of scale or space of a live venue. I do find the music more satisfying with the bass boost on.

post #5 of 31
Thread Starter 
Quote:
So, if you're bass boost affects the sound of your "non bassy" music, then even your non-bassy music still has content at some of the same frequencies affected by the bass boost. The effect your hearing is still just the boosting of the lower frequencies in the music.

 

Again, this will depend heavily on what exactly the bass boost does to the audio.

 

Cheers

Thanks for your perspectives. And yes, it seems that even with music that clearly does not have any actual notes that go that low, that there still is some content in the lowest register....maybe some kind of room resonance. I do not know the explanation, but maybe someone else does.

post #6 of 31
Quote:
Originally Posted by Nirmalanow View Post

Thanks for your perspectives. And yes, it seems that even with music that clearly does not have any actual notes that go that low, that there still is some content in the lowest register....maybe some kind of room resonance. I do not know the explanation, but maybe someone else does.

 

Unless you are listening to pure, droning tones, the fact is, there will most likely always be some non-zero content in the lower registers because the notes being played are finite in duration in time. There is the equivalent of the uncertainty principle that says the more certain you are about the frequency content of a tone, the less certain you are about that tone's duration. the converse is also true, if you have a sound that is of finite duration (for example, a plucked string whose amplitude decays away), then the frequency content of the sound is "smeared ".

 

Let me illustrate with a simple example. The lowest string on a guitar with standard tuning is E at 82.4 Hz (assuming 440Hz A). Let's examine the frequency content of a note where the string is plucked and decays with a duration of 0.5 seconds.

 

 

(what I have done is taken a pure tone at 82.4Hz and multiplied by a window that is comprised two halves of a Guassian, the first with a 1/e^2 width of 0.01 s and the second with a 1/e^2 width of 0.5s)

 

If you look at the spectral content of this finite-length sound, you can see that the spectral content is non-zero everywhere, which may come as a surprise to those expecting to only see something at 82.4 Hz!

 

As you can see, the peak at 82.4 Hz is there, but the spectral content of the tone has been "smeared". The 40 Hz frequency content is 37 dB below the tone's main peak, which is very small, but certainly not zero (and well within the bit depth of the recording medium)

 

Let me apply a "bass boost" to this. In this case, I created something that roughly resembles the ican boost #1 curve in the image xnor linked too. This is the milder of the two "bass boosts":

When I apply this boost to the original sound, the result is a small difference between the "boosted" sound and the original sound. Here, the original is in blue, and the green is the "bo

 

osted" version. The overlap isn't perfect, hence, there is a subtle difference.

 

 

To make it a bit clearer, let me zoom in a bit on the time axis:

 

There you go. Bass boost will likely always do a little bit of something to your music, even if its just female vocals and guitar.

 

Cheers

post #7 of 31
Thread Starter 

Wow, thanks for that thorough explanation. So it is not just room ambient sounds, but actual low frequencies in the music even if the notes being played do not supposedly go that low.

 

I would have still enjoyed the bass boost even without knowing why, but now it makes sense that the sound feels fuller and has more presence even if it is vocals and guitar type music.

post #8 of 31
I was reading the title and it reminded me of an article I read a long time ago regarding exposures to infrasonic frequencies.

If you're curious about the article:
http://neuroresearchproject.com/2013/02/19/1289/
Skip down to "The Ghost in the Machine" (from the date of the post, it's obviously not the original article that I read, but does have all the details I can recall about it; I couldn't find the original article).

I wouldn't worry too much about subsonic frequency induced mind screws when it comes to music listening. But ClieOS' graph makes me curious how far below 20Hz the bass boost goes.
post #9 of 31

If it's a low shelf then down to DC.

post #10 of 31

SpectrumiCANle.png

post #11 of 31
Thread Starter 
Quote:
Originally Posted by HalidePisces View Post

I was reading the title and it reminded me of an article I read a long time ago regarding exposures to infrasonic frequencies.

If you're curious about the article:
http://neuroresearchproject.com/2013/02/19/1289/
Skip down to "The Ghost in the Machine" (from the date of the post, it's obviously not the original article that I read, but does have all the details I can recall about it; I couldn't find the original article).

I wouldn't worry too much about subsonic frequency induced mind screws when it comes to music listening. But ClieOS' graph makes me curious how far below 20Hz the bass boost goes.


I also read years ago about how it appears that Chinese Qi-Gong masters emit low frequency infrasonic sound waves that appear to have healing effects. I found this reference to the study: https://ymaa.com/forum/viewtopic.php?t=4339

 

For a while there was a Qi Gong machine that simulated the output of the Qi Gong masters. I guess now it can only be sold for animals: http://www.minglewoodsolutions.com/PerformanceEssentials/infrasonic-qi-gong-master-energy-simulator-ff80818133c945ca0133ffa741d54ced-p.html

 

I used to have a sound table, which was a massage table with sub-woofers built in. It was very relaxing to lie on the table with music with a lot of deep bass: http://vibroacoustic.org/

post #12 of 31
Thread Starter 
Quote:
Originally Posted by ClieOS View Post

SpectrumiCANle.png


Interesting. A lot of headphones (including my ESW9s) list their frequency response as 5-35 hz, so the infrasonic info is being reproduced, no matter how slight it is.

post #13 of 31

There's just a few problems here:

 

a) lower hearing limit is roughly 20 Hz, lower frequencies have an extremely high hearing threshold so even if you boost something by 10 dB there it most likely doesn't even reach this threshold with music

 

b) most recordings are mixed/mastered with a high pass filter that removes (more correctly: attenuates) this stuff

 

c) the stuff down there just causes heat in the voice coil and reduces excursion for more audible frequency content

post #14 of 31
Thread Starter 
Quote:
Originally Posted by xnor View Post

There's just a few problems here:

 

a) lower hearing limit is roughly 20 Hz, lower frequencies have an extremely high hearing threshold so even if you boost something by 10 dB there it most likely doesn't even reach this threshold with music

 

b) most recordings are mixed/mastered with a high pass filter that removes (more correctly: attenuates) this stuff

 

c) the stuff down there just causes heat in the voice coil and reduces excursion for more audible frequency content


Yes, there is no question that these frequencies are normally inaudible, but the articles linked to suggest that they still affect us. Who knows if there is any effect at the typical small and/or attenuated levels in most recorded music. Do you know where the high pass filter is usually set in the mixing/mastering process?

 

I have owned amplifiers in the past that had switchable high pass filters to prevent any extreme low frequencies causing problems in the speakers.


Edited by Nirmalanow - 7/21/13 at 10:27am
post #15 of 31

Just something to consider.... From the article in question:

 

Quote:

A more recent book by Kroemer (1994) describes the effects of low frequency vibration as follows;

‘Vibration of the body mostly affects the principal input ports, the eyes, and principal output means, hands and mouth.’(p. 287).

‘Exposure to vibration often results in short-lived changes in various physiological parameters such as heart rate…At the onset of vibration exposure, increased muscle tension and initial hyperventilation have been observed.’ (p. 280).

Tables 5-12 of Kroemer (1994) on p. 288, indicate that the resonant frequencies of body parts are; Head (2-20 Hz causing general discomfort), Eyeballs (1-100Hz mostly above 8 Hz and strongly 20-70Hz effect difficulty in seeing). However, different sources give different resonant frequencies for the eye itself. The resonant frequency is the natural frequency of an object, the one at which it needs the minimum input of energy to vibrate.  As you can see from above, any frequency  above 8 Hz will have an effect and some sources quote 40Hz.

Most interestingly, a NASA technical report mentions a resonant frequency for the eye as 18 Hz (NASA Technical Report 19770013810). If this were the case then the eyeball would be vibrating which would cause a serious ‘smearing of vision. It would not seem unreasonable to see dark shadowy forms caused by something as innocent as the corner of V.T.’s spectacles. V.T. would not normally be aware of  this but its size would be much greater if the image was spread over a larger part of his retina.

Another NASA report (NASA Technical Report 19870046176) mentions hyperventilation as a symptom of whole body vibration. Hyperventilation is characterised by quick shallow breathing and reduces the amount of carbon dioxide retained in the lungs. Note that Tempest (1976) also mentions respiratory difficulties caused by frequencies in our range. Hyperventilation can have profound physiological effects. For example, Flenley (1990) describes the symptoms of hyperventilation as ‘breathlessness usually at rest, often accompanied by light-headedness, muscle cramps, fear of sudden death and a feeling of difficulty in breathing in’.

 

A large part of the discussion was about how the infrasound interacts and affects the body. In the case of headphone+headphone amplifiers where the sound is only being reproduced at the ear, only a tiny fraction of the acoustic energy is impinging on the body as would be the case if someone was standing in a infrasonic resonant cavity. Headphones lack sufficient oomph to generate any sort of appreciable amplitude sound wave at the frequencies in question.

 

Cheers!

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