so whats the deal with Fs?

[buggsson 10+ year member]

I don't mean to come off rude; I'm just trying to promote a little inquisitive thinking. What is the definition of subsonic, and what relevance does it have to a high-pass filter?

I've just seen a definition of a subsonic filter. Unfortunately, it is in swedish, so I hope I get my translation somewhat correct. It says that a subsonic filter is all but a normal highpass filter, and that the only difference is that it works with the frequencies at the very bottom end of what the human ear can detect. What do you all think of that explanation?

 

[buggsson 10+ year member]

ok so im in car audio school, and im learning stuff, (weird i know) so fs is important for mids and highs because they dont have enclosures to keep them inline and they cant take music below their Fs?
- Yes they can

so im confused how do you design a box then and how do you know how low it will play?

For a closed box, you use Qts, Fs and Vas. Vb will then give you the Qtc you are after, for example, the flattest response=Qtc 0.707. I've been told that for a sealed, a Qtc of 0.8 will sound even better, I don't know. 0.8 will however give you a smaller box than 0.707. For a sealed box, you will get a lower frequency response than the F3, I think it is because it rolls off with 12dB/octave. I'm not that knowledgeable myself, still learning as well.

To see how a closed box calc. works, you can check here (I hope it is somewhat correct): http://www.carstereo.com/help2/Articles.cfm?id=30

 

[bass_lover1 10+ year member]

that is super-sonic id10t

Sorry, I should have put BELOW mach 1, that would have made more sense. You on the other hand, still couldn't put the two together.

 

[squeak9798 5,000+ posts]

Second, Sub-sonic IS NOT and will NEVER be sound not audible to the human ear. Think fighter jets and Mach 1, then give it some more thought, and you'll realize you're all idiots, ok except Neil.

sub·son·ic (sŭb-sŏn'ĭk) Pronunciation Key

adj.

1. Of less than audible frequency.

2. Having a speed less than that of sound in a designated medium.

The American Heritage® Dictionary of the English Language, Fourth Edition

Copyright © 2006 by Houghton Mifflin Company.

Published by Houghton Mifflin Company. All rights reserved.

 

[squeak9798 5,000+ posts]

third i have built transimission lines with extreme low frequecy output and extention.. more felt than heard but down to around 18hz it was definitally audible... just like any other transducer your hearing has a roll off... you might have a 50db slope that starts @ 25... someone elses might vary slightly...

When people "hear" these low frequency sounds, they are typically hearing the harmonics and not the fundamental frequency.

 

[dman4486 5,000+ posts]

Sorry, I should have put BELOW mach 1, that would have made more sense. You on the other hand, still couldn't put the two together.

even though you have been here since '04, you still do not recognize sarcasm when you see it.

 

[bass_lover1 10+ year member]

sub·son·ic (sŭb-sŏn'ĭk) Pronunciation Key adj.

1. Of less than audible frequency.

2. Having a speed less than that of sound in a designated medium.

The American Heritage® Dictionary of the English Language, Fourth Edition

Copyright © 2006 by Houghton Mifflin Company.

Published by Houghton Mifflin Company. All rights reserved.

sub⋅son⋅ic

   /sʌbˈsɒnɪk/ Show Spelled Pronunciation [suhb-son-ik

–adjective

1. noting or pertaining to a speed less than that of sound in air at the same height above sea level.

2. infrasonic.

//content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[dman4486 5,000+ posts]

for the original question, since the rest of you are arguing over bananas and oranges, a SSF in terms of amplifiers is a high pass filter, sometimes adjustable, which cuts lower frequencies in order to prevent subwoofer unloading.

And yes, a SSF cuts frequencies on a curve. Not just boom everything below the SSF is gone.

 

[squeak9798 5,000+ posts]

sub⋅son⋅ic   /sʌbˈsɒnɪk/ Show Spelled Pronunciation [suhb-son-ik

–adjective

1. noting or pertaining to a speed less than that of sound in air at the same height above sea level.

2. infrasonic.

//content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

I'm not disagreeing that subsonic can also be defined as less than the speed of sound.

But you stated it does not and never will mean less than audible frequency, which is undeniably FALSE, as identified by the definition provided above which indicates subsonic can be defined as both being less than audible frequency and speed less than the speed of sound.

Welcome to the English language. Hope you stick around and enjoy the scenery.

EDIT: Oh yeah....and notice the 2nd definition provided there in your quote.....INFRASONIC.

Subsonic = Infrasonic, per the definition you provided.

 

[newusername 10+ year member]

Well now we've got a problem, because the dictionary seems to acknowledge the common misuse of the term.

Subsonic and supersonic describe only one thing: the speed of an object relative to the speed of sound in a sound-propagating medium. If something is travelling faster than the speed of sound, than it is supersonic. If it is travelling slower than the speed of sound, than it is subsonic.

Whether something is above or below our hearing range is a question of ultrasonic or infrasonic. We've already seen those two defined so we won't go over that again.

Suppose we have an item travelling above the speed of sound but with a frequency of 10 Hz. This is below the common bandwidth of human hearing, but is it subsonic? Not at all.

Amplifiers use the term SSF to denote a high-pass filter. I wonder how you can filter low-frequency content if you have a filter that removes anything travelling below the speed of sound. As you can see, that makes no sense. Instead, your amplifier has an InfraSonic Filter, which does do as described.

It is very much a semantical argument, but it is important to note the difference between the actual meaning of words, and the uninformed marketing that has existed in car audio for a couple decades. We've stopped saying a lot of silly things, but some just keep on going (watts RMS is another good example).

 

[dman4486 5,000+ posts]

Well now we've got a problem, because the dictionary seems to acknowledge the common misuse of the term.
Subsonic and supersonic describe only one thing: the speed of an object relative to the speed of sound in a sound-propagating medium. If something is travelling faster than the speed of sound, than it is supersonic. If it is travelling slower than the speed of sound, than it is subsonic.

Whether something is above or below our hearing range is a question of ultrasonic or infrasonic. We've already seen those two defined so we won't go over that again.

Suppose we have an item travelling above the speed of sound but with a frequency of 10 Hz. This is below the common bandwidth of human hearing, but is it subsonic? Not at all.

Amplifiers use the term SSF to denote a high-pass filter. I wonder how you can filter low-frequency content if you have a filter that removes anything travelling below the speed of sound. As you can see, that makes no sense. Instead, your amplifier has an InfraSonic Filter, which does do as described.

It is very much a semantical argument, but it is important to note the difference between the actual meaning of words, and the uninformed marketing that has existed in car audio for a couple decades. We've stopped saying a lot of silly things, but some just keep on going (watts RMS is another good example).

the issue with your statement is that a SSF is adjustable up into the audible range and therefore an infrasonic filter would not be the correct term either.

 

[newusername 10+ year member]

Infrasonic is correct since it's intent is to roll-off damaging music below the bandwidth of your hearing. The fact that you choose to roll-off response earlier is a choice made by you, and allowed by the manufacturer. Regardless, it is still more ISF than it is SSF.

 

[dman4486 5,000+ posts]

Infrasonic is correct since it's intent is to roll-off damaging music below the bandwidth of your hearing. The fact that you choose to roll-off response earlier is a choice made by you, and allowed by the manufacturer. Regardless, it is still more ISF than it is SSF.

its intent is to roll off below enclosure tuning to prevent unloading or in the case of sealed enclosures to prevent reaching mechanical limits of the driver.

to state that it is to remove inaudible frequencies is to me silly.

however I do agree that subsonic does not fit the bill either, but is too well known of a term to throw away ATP

 

[GregU 10+ year member]

OK im def talking outta my ***... if you do some research people have heard as low as 3hz.. in paticular a space shuttle launch is audible, measured 3 cycles at 202db if i remember correctly... another time is reports from several 100s people complaining of very low frequency sounds causing them to be unable to sleep... i don't recall where, but if you watch discovery and the mitillary channel you will probably see the eposide.. third i have built transimission lines with extreme low frequecy output and extention.. more felt than heard but down to around 18hz it was definitally audible... just like any other transducer your hearing has a roll off... you might have a 50db slope that starts @ 25... someone elses might vary slightly...

They are hearing the overtones......

 

[newusername 10+ year member]

Why would you want to remove any audible frequencies? I agree that it is there to prevent mechanical damage, but from inaudible frequencies. Granted, many people have different purposes, but I'm supposing that we're trying to reproduce the recording here.

You mention it is a well-known term; I assert the opposite.