Re: Subwoofer Discussion (originally from NSAG thread)

[adrian4454]

Doesn't matter la.. been wondering on the sensation of how it feel like, when double plucking cello in some albums and deep deep bass on some pop songs.. some "low level" fun~

[WongKN]

Adrian,
perhaps a visit to Seremban ? Maxx Audio Trading.....

[musicmusic]

(Re-post)
http://en.wikipedia.org/wiki/Infrasound
Human reactions to infrasound
Twenty Hz is considered the normal low frequency limit of human
hearing. When pure sine waves are reproduced under ideal conditions and
at very high volume, a human listener will be able to identify tones as low as 12 Hz.[15] Below 10 Hz it is possible to perceive the single cycles of the sound, along with a sensation of pressure at the eardrums.


Ref. [15]: ^ Olson, Harry F. (1967). Music, Physics and Engineering. Dover Publications. p. 249. ISBN 0486217698.

Mugenfoo

You said “And BTW, average Humans CAN hear below 20Hz (albeit at much reduced sensitivites, hence the Fletcher-Munson curves or the updated ISO 226:2003 curves). The 20Hz measurement limit was imposed because back in the early part of the 20th century, Misters Fletcher & Munson did not have a decent apparatus to generate, nor measure 20Hz reliably for their human hearing tests”


The 2003 revision reiterated the 20hz limit. You don’t see it going beyond that. See the graph.


Then you come up with Wikipedia sourced 1967 materials about infrasound to justify your earlier statement. How is that related to the 2003 revision bro? Did the revision now say human can hear beyond 20hz under normal circumstances?

The revision specifically did not mention anything about hearing below 20hz.

Talking about humans hearing infrasound, then you should read about more recent study about the effect of windmill low frequencies (about 8hz, maybe?) on some individuals.

They are also some individuals can pick telepathy.

Some can hear frequencies above 20khz if you blast at 140db.

Some can’t hear anything. Maybe, millions of them.

We call them freaks or deaf. They are not part of the statistics.

[htkaki]

Adrian, I am using the SVS lowest model cylindrical sub. I think it is PCB-12 or something like that. For tuning, this is one of the reasons why I bought my Marantz SR-5005 AV amp - it has Audyssey built in which I use to set-up the whole 5.1 speakers.

It's PC12-NSD.



* Smoothed, quasi-anechoic frequency response: Measured with high
resolution instrumentation via "ground plane" technique, outdoors, at
two meters' distance, a minimum of 70 feet from reflective boundaries.
Predecessor PC12-NSD FR temporarily shown.

Actually, there is another one sub that is 'affordable' and could go down to 14Hz. Rythmik F12 sealed subwoofer at RM3,299. (sorry, admin or mod. Not trying to promote but it is a fact that NO SUB at this price that could go below 20Hz let alone 14Hz) PJ / KL folks can go to Acoustiques System at Amcorp Mall to test it.

[mugenfoo]

The revision specifically did not mention anything about hearing below 20hz.

"Did not mention" doesn't imply that it completely STOPS there. One should learn to read and then DEDUCE the information as presented. Not just take a snippet of info here and there as the ultimate truth. This is akin to falling into the same trap as those who till today, stubbornly believe that the CD has fulfilled the "perfect sound forever" promise.

Talking about humans hearing infrasound, then you should read about more recent study about the effect of windmill low frequencies (about 8hz, maybe?) on some individuals.

Re. infrasonics, its as quoted from the well established book as referenced. If you think you can do better, go ahead and publish your new findings in a public forum. Or better yet, pen a dissertation and earn your Ph.D as well.

If you can reference a better textook source to show otherwise, then show it here objectively.

They are also some individuals can pick telepathy.

Some can hear frequencies above 20khz if you blast at 140db.

Some can’t hear anything. Maybe, millions of them.

We call them freaks or deaf. They are not part of the statistics.

Take a step back first. By your own opinions, seems like you're the only odd one out here. So don't be so quick to label any minority as "deaf" or "freaks". But do take a look in the mirror first.

[uncle_vic]

Hi Mugen, U are right again! I've at least 4 class A subs and 6 class B subs!

Mugen wrote........

"Well, the RM1K sub would probably be in unker Vic's "Type-A" sub classification.... "

But dun worry, we all got to start somewhere , right ?

[musicmusic]

"Did not mention" doesn't imply that it completely STOPS there. One should learn to read and then DEDUCE the information as presented. Not just take a snippet of info here and there as the ultimate truth

DEDUCE? You mean buat cerita like measuring PF of the wall like you try to con a reader here before?

You are just blurting without knowing what the revision was all about.

Only 3 studies out of the 12 taken in to the revised ISO standard ever did measurement beyond 20hz.

None reported hearing anything below 20hz under the normal conditions.

So nothing to DEDUCE if the experiment itself already reported none heard them.

Your Olson wasn’t even mentioned, referred or considered anywhere in the revision.


Sorry, you won't find it on Google. But if you are a good kaki google who knows?

[sflam]

interesting read on infrasound in nature, the earth and universe.



http://www.watersciences.org/documents/Infrasound-Marrin.pdf

[sflam]

how infrasound can affect the human body...
from http://www.lowertheboom.org/trice/infrasound.htm



Studies show the different ways in which infrasound affects the human body. As infrasound pitches, or cycles per second, decrease, deadly effects on the body increase. Infrasound disrupts the normal functioning of the middle and inner ear, leading to nausea, imbalance, impaired equilibrium, immobilization, and disorientation. Exposure to even mild doses of infrasound can lead to illness. Increased intensities of infrasound can result in death.
These are a few examples of low frequency (below 500 Hz) and infrasound (below 20 Hz.) levels and their effects:



12 Cycles Per Second (Hz) - Walt Disney and his artists accidentally experienced infrasound on one occasion. A cartoon sound effect was slowed from 60 cycles per second to 12 cycles per second via a tape-editing machine and was amplified through the theater system. The resulting tone, though brief in duration, produced in the entire crowd nausea that lingered for several days.
100 Cycles Per Second (Hz) - At this level, a person experiences irritation, "mild nausea, giddiness, skin flushing, and body tingling." Following this, a person undergoes "vertigo, anxiety, extreme fatigue, throat pressure, and respiratory dysfunction." (source; the Sonic Weapon of Vladimir Gavreau, by Gerry Vassilatos)


60 - 73 Cycles Per Second (Hz) - "coughing, severe sternal pressure, choking, excessive salivation, extreme swallowing pains, inability to breathe, headache, and abdominal pain" were present. In the post exposure phase, test subjects continued to cough, exhibit fatigue, and have skin flushing for up to four hours. (Source - THE SONIC WEAPON OF VLADIMIR GAVREAU, by Gerry Vassilatos)
WALL CURRENT - In the United States, wall current is 60 cycles per second (Hz). In Europe, the wall current is 50 cycles per second. Since European current has a lower cycle, an observer can actually see light bulbs slightly flicker.


43 - 73 Cycles Per Second (Hz) - lack of visual acuity, IQ scores fall to 77% of normal, distortion of spatial orientation, poor muscular coordination, loss of equilibrium, slurred speech, and blackout.
1 - 10 Cycles Per Second (Hz) - "Lethal infrasonic pitch lies in the 7 cycle range. Small amplitude increases affect human behavior in this range. Intellectual activity is first inhibited, blocked, and then destroyed. As the amplitude is increased, several disconcerting responses have been noted. These responses begin a complete neurological interference. The action of the medulla is physiologically blocked, its autonomic functions cease." (source; the Sonic Weapon of Vladimir Gavreau, by Gerry Vassilatos)


50 - 100 Cycles Per Second (Hz) - at 150 dB and higher, "intolerable sensations in the chest and thoracic region can be produced - even with the ears protected. Other physiological changes that can occur include chest all vibration and some respiratory rhythm changes in human subjects, together with hypopharyngeal fullness (gagging). The frequency range between 50 and 100 Hz also produces mild nausea and giddiness at levels of 150 - 155 dB, at which point subjective tolerance is reached. At 150 to 155 dB (0.63 to 1.1 kPA), respiration-related effects include substernal discomfort, coughing, severe substernal pressure, choking respiration, and hypopharyngeal discomfort." (source; 'Acoustic Trauma: Bioeffects of Sound,' by Alex Davies)
7 Cycles Per Second (Hz) - The most profound effects at this infrasonic level occur here. Seven Hz "corresponds with the median alpha-rhythm frequencies of the brain. It is also commonly alleged that this is the resonant frequency of the body's organs and hence organ rupture and death can occur at high-intensity exposures." (source; 'Acoustic Trauma: Bioeffects of Sound,' by Alex Davies)


Scientific Applications and Research Associates (SARA) - This agency's alleged infrasound research showed, "infrasound at 110 - 130 dB would cause intestinal pain and severe nausea. Extreme levels of annoyance or distraction would result from minutes of exposure to levels 90 to 120 dB at low frequencies (5 to 200 Hz), strong physical trauma and damage to tissues at 140 - 150 dB, and instantaneous blastwave type trauma at above 170 dB. At low frequencies, resonance's in the body would cause hemorrhage and spasm/ in the mid-audio range (0.5 to 2.5 kHz), resonance's in the air cavities of the body would cause nerve irritation, tissue trauma and heating; high audio and ultrasound frequencies (5 to 30 kHz) would cause heating up to lethal body temperatures, tissue burns, and dehydration; and at high frequencies, or with short pulses, bubbles would form from cavitation and micro-lesions in tissue would evolve." (source; 'Acoustic Trauma: Bioeffects of Sound,' by Alex Davies)
Infrasound Toxicological Summary, November 2001 - "When male volunteers were exposed to simulated industrial infrasound of 5 and 10 Hz and levels of 100 and 135 dB for 15 minutes, feelings of fatigue, apathy, and depression, pressure in the ears, loss of concentration, drowsiness, and vibration of internal organs were reported. In addition, effects were found in the central nervous system, the cardiovascular system, and the respiratory system. Synchronization phenomena were enhanced in the left hemisphere. Visual motor responses to stimuli were prolonged, and the strength of the effect was reduced. Heart rate was increased during the initial minutes of exposure. Depression of the encephalic hemodynamics with decreased venous flow from the skull cavity was observed. Heart muscle contraction strength was reduced. Respiration rate was significantly reduced after the first minute of exposure."


The U. S. Navy has an anti-submarine device called Low Frequency Active (LFA) sonar. It emits 240 dB. Damage was possibly done to whales and dolphins, causing them to beach. Whales avoid areas with 120 dB or above. The Navy sets 140 dB as the maximum level of safe exposure to humans.
Long pipe organs, such as those found in churches and cathedrals produce infrasound. In one UK study, the extreme bass frequencies instilled strange feelings at a concert hall. Effects were "extreme sense of sorrow, coldness, anxiety, and even shivers down the spine." (source; Organ Music Instills Religious Feelings,' by Jonathan Amos, 9/8/2003)

[WongKN]

I doubt if any hifi system can produce those kind of sound levels. 130dB ? I think we go deaf at not much above 100dB. In fact it is said that prolong exposure to 90dB is enuf to destroy our hearing.

[sflam]

musicmusic wrote:

There is no such thing as sub should be felt but not heard unless your restrict it to below 20hz where almost 99.999% music do not have any frequencies within that range. In principle, in this case, you can see and feel ( knowing that you have a sub) the presence of the subwoofer but it is not doing anything.

i hv been googling around (sieving out the bullshit of course) and found that there are quite a number of test cds and special effects cds with signals below 20Hz.

even classical music cds can have notes below 20Hz - for e.g. tchaikovsky's 1812 overture (telarc) has a 7Hz note while 'battle music of beethoven and liszt' (telarc) has a 5Hz note.

check the list of 30 cds with infrasonic music here http://home.provide.net/~djcarlst/basscds.htm

it's only a question of whether the cd player can reproduce the infrasonic sound cos most cd players are rated at only 20Hz-20kHz whilst the marantz cd5004, for eg, is rated at 2Hz - 20kHz.

[uncle_vic]

I don't think(if someone here can show that I'm wrong) many setups, maybe none at all, can reproduced down to 20Hz to a neat 0dB! 20Hz at maybe -24dB is already an achievement, even with subwoofers a -12dB already will cause a stir among forummers and maybe instigate a name calling session already!

[mugenfoo]

Thanks guys ... i believe it's very clear who knows what they are talking about here, and who's just making useless noises.

[WongKN]

sflam,

Your problem is you only looked at HALF of the specification of frequency response. Frequency response is listed as a frequency range followed by the maximum deviation. I.e. the frequency response of a CD player is not just 20Hz to 20kHz. It is 20Hz to 20kHz +/- 0.5dB (for e.g.) The key is the +/-. This means that outside of the boundary, it does not mean there is strictly no signal (actually there -should- be no signal above 22kHz on a well designed CD player because of the function of the low-pass filter). But unless there is a high-pass filter for 20Hz specifically designed into the CD player, else, even if the frequency response for the player is 20Hz - 20kHz, it will still produce signal below 20Hz, just that it will be lower by more than 0.5dB (or whatever is the deviation listed in its specification).

For example, frequency response for NAIM CD555 CD player is listed as Frequency response: 10Hz–20kHz, +0.1dB/–0.5dB.

If you go and google for the Red book CD specification (official), you will not see any statement saying RBCD must have a frequency response of 20Hz to 20kHz and nothing beyond either boundary. But of course theory says with only 44.1kHz sampling rate, we cannot have anything above 22kHz sound frequency. But there is no statement about the lowest frequency allowed.

[mugenfoo]

The key is the +/-. This means that outside of the boundary, it does not mean there is strictly no signal

Exactly. Just because things are rated to just within a certain range, it doesn't mean that what happens beyond these boundaries are non-existant.

Deja Vu ....

[sflam]

wongkn,



u r right.



i hv found out that when they came up with the red book specs, they were more worried about the nyquist issue and cd player manufacturers just added a brickwall filter at 20khz to solve it. the manufacturers were not that bothered abt what happened below 20hz, but some added a filter to cut off below 20Hz cos they were worried about passing dc to the amp.

that's why some cd players cannot output infrasonic music.

[mugenfoo]

DEDUCE? You mean buat cerita like measuring PF of the wall like you try to con a reader here before?

Ok lets put this "PF" matter to rest once and for all.

And to further illustrate for clarity's sake, i shall include some extremely technical diagrams that hopefully isn't beyond anyone's understanding.


How to measure PF at the wall. (means, not at the power-station, not at the sub-station, or even the roadside DB box).
Step 1: Plug the PF meter on the wall.
Step 2: Plug an electrical load onto the PF meter's outlet.
Step 3: Operate the PF meter according to the mfg's instructions and note the readings.



But just in case, some mr. dear_all-alone_in_his_misinformed_opinions could miscontrue all the above and mis-attempt such measurements, I have taken the liberty to also include a "Don't Do" scenario (for safety's sake, of course). After all, we're all talking about home electrical systems and it does have a certain amount of hazard and risk involved.



Cheers & enjoy the diagrams.

[musicmusic]

Nice try

[carz]

musicmusic,

what you you trying to proof ? It is just a picture with a fluke meter and the text below it with Mugen commenting about the importance of power factor.

[jchong]

I don't think(if someone here can show that I'm wrong) many setups, maybe none at all, can reproduced down to 20Hz to a neat 0dB! 20Hz at maybe -24dB is already an achievement, even with subwoofers a -12dB already will cause a stir among forummers and maybe instigate a name calling session already!

You mean a system that is flat down to 20Hz? I assume that's what you're saying by "down to 20Hz to a neat 0dB".

That's very possible in room with a capable subwoofer. Many of the capable subwoofers have a -3dB point in the high teens (like 17Hz, 18Hz) and this is measured anechoically. In room with gain, these subs can go even lower.

For a demo just visit htkaki, his setup is flat down to 20Hz and below!

[jchong]

I doubt if any hifi system can produce those kind of sound levels. 130dB ? I think we go deaf at not much above 100dB. In fact it is said that prolong exposure to 90dB is enuf to destroy our hearing.

I think it's important to define the frequencies relative to the loudness levels.

In general, OSHA prescribes 90dB for 8 hours as maximum before damage occurs. At 100dB - 2 hours. At 110dB - 30 mins. But I believe this is measured as dBA and centers around the frequencies the ear is most sensitive towards. You're right, I doubt any domestic hifi set can hit even 110dBA without blowing some drivers or be plagued by massive distortion.

However, for hifi or home theater we normally use dBC, which weights the bass more. And with the addition of big subwoofers, it is very possible to hit 110dBC during the big explosive scenes, but this is only for a few seconds.

[jchong]

the frequency response of a CD player is not just 20Hz to 20kHz. It is 20Hz to 20kHz +/- 0.5dB (for e.g.) The key is the +/-. This means that outside of the boundary, it does not mean there is strictly no signal

Agreed. Do you find that outside the boundary, the deviation starts to then increase very rapidly?

Don't know about CD players, but like for speakers they will normally specify +/- 3dB, but once outside the boundary it will very quickly drop to -6dB, -12dB.... i.e. steep roll off.

[WongKN]

For most hifi equipment yes. But for high-end equipment, not necessarily. I remember the famous Mark Levinson No. 23 power amp. It was rated at 200WPC by ML and it was tested by Stereophile to deliver 200WPC at the normally accepted specifications in the high-end industry.

Then ML came out with the updated No. 23.5. It was still spec'ed at 200WPC but was so powerful that when Stereophile tested it, they found that the 23.5 delivered right up to 300WPC when measured at the standard specifications (distortion level was the measuring criteria I think). So Stereophile told ML that they are not going to bother about what they (ML) define the 23.5 to be but they (stereophile) decided to call the 23.5 a 300WPC power amp.

So we had the unusual situation where the manufacturer markets the ML 23.5 as a 200WPC power amp but a well respect hifi magazine INSISTS on calling it a 300WPC power amp. Stereophile's stand is that it is not fair representation of the capability of the 23.5 to call it 'only' a 200WPC, not when other people are using lower standards for their 200WPC power amps.

I think if we research the Stereophile website, we can see this kind of relationship. I.e. a highend CD player might be spec'ed for 20-20k +/- 0.5dB but might well be only slightly worse at 10Hz lower. Whether the manufacturer decides to exploit this for marketing purposes depends on the individual manufacturer of course.

[uncle_vic]

jchong wrote.......




You mean a system that is flat down to 20Hz? I assume that's what you're saying by "down to 20Hz to a neat 0dB".

That's
very possible in room with a capable subwoofer. Many of the capable
subwoofers have a -3dB point in the high teens (like 17Hz, 18Hz) and
this is measured anechoically. In room with gain, these subs can go even
lower.

For a demo just visit htkaki, his setup is flat down to 20Hz and below.




I've listened to HTKaki's demo last year at the klaiv2010 with the SVS subs.............I know what it can do!


But did u guys go into the TBI room @kliav2011 to listen to the sub sound, ie. low bass sound in 3D soundstaging?

[mugenfoo]

jchong wrote.......

very possible in room with a capable subwoofer. Many of the capable
subwoofers have a -3dB point in the high teens (like 17Hz, 18Hz) and
this is measured anechoically. In room with gain, these subs can go even
lower.

Small rooms are often times not condusive for low freqs, especially when the wavelengths are very long with respect to the room dimensions. There will be alot of desctructive interference and the bass actually rolls-off sooner than its anechoic specs.

Best is to have the proper measurement equipment and software to really deduce that would be the real-world response of the entire setup incl the room conditions. Removes the guessing and theorising out of the equation.

[uncle_vic]

Hi Mugen, That's written by Jchong..............

I just rry to reproduce it here to answer him...........

[uncle_vic]

http://www.tbisound.com/_pdf/tbi200.pdf

[jchong]

I've listened to HTKaki's demo last year at the klaiv2010 with the SVS subs.............I know what it can do!

But did u guys go into the TBI room @kliav2011 to listen to the sub sound, ie. low bass sound in 3D soundstaging?

htkaki's demo at KLIAV 2010 while quite good, is not as good as the setup in his own shop.

Which exhibitor showcased TBI stuff? I don't recall seeing it.

[jchong]

Small rooms are often times not condusive for low freqs, especially when the wavelengths are very long with respect to the room dimensions. There will be alot of desctructive interference and the bass actually rolls-off sooner than its anechoic specs.

Best is to have the proper measurement equipment and software to really deduce that would be the real-world response of the entire setup incl the room conditions. Removes the guessing and theorising out of the equation.

Yeah small rooms can be quite problematic for low freq.

I agree that measurements can shed a lot of light into freq response. That's what made me invest in a REW setup to take the guess work out of it.

[mugenfoo]

Yeah small rooms can be quite problematic for low freq.

I agree that measurements can shed a lot of light into freq response. That's what made me invest in a REW setup to take the guess work out of it.

You are definitely on the right track. The next step would be also to get a calibrated measurement mic and it doesn't need to cost a bomb. There is a company called Cross-Spectrum Labs that sells calibrated Behringer and Dayton mics. It comes with a CD that has a calibration file that can be loaded into REW for best accuracy in measurements.

Another neat thing about REW is the ability to measure decay times across the audible spectrum. This will give alot of insight into the sonic signature at various places around the room & also how speaker placement interacts with the room as well. These are the "waterfall plots" and if one knows how to use and read the info off there, it is an extremely powerful measurement device for sonic diagnosis.

A waterfall plot is actually a 3D measurement of not only a room's freq response, but also how the Freq response spectrum "decays" over a period of time.

Visualising on an X-Y-Z plane: X = Frequency (e.g. 15Hz to 20KHz), Y = Magnitude (e.g. 0dB to -60dB), Z = time (e.g. 0ms to 500ms).

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