Room Response and Preference

[manoj.p]

I am no speaker designer and I am have no idea of the the technical terms you are referring to.

I referred to those terms because those were incorrectly referred few posts above. There seemed some confusion that a speaker can go lower than Fs.

Just curious, are you confusing "free air resonant" to "air free resonant"? The simplest way to determine Fs is to tap the driver with your finger and frequency where it resonates. That will be the Fs of the driver. This is is done in free air. NOT in air free vacuum.

I am not confusing these two. Did I ever said "air free" or "vacuum"?

Now taking the same woofer/driver in a cabinet, the resonance goes higher as it is no longer able to vibrate freely in free air but need to vibrate with the resistance of the air in the enclosure. Here the resonant frequency will be higher than what it was in free air. That value is called Fc.

Yes, that's what I said, without referring it as Fc.

I was just trying to reiterate that neither Fs or Fc matters. All the guide of the correct subwoofer crossover point and phase is just a guideline. Your room is a huge loudspeaker. Or imagine yourself inside your loudspeakers and listening to the sound. no one can predict how the soundwaves behave at your listening space.

If you don't do a room measurement for the subwoofer, you will compromise the sound. Try run a frequency sweep and you will be surprised to see that some frequencies can be completely in audible at your normal listening level and some may be too loud.

IMHO.

Agree completely. Although, the measurement is new addition to this discussion. Anyway, the general guide to cross-over is still valid even if one measures the room. That guidance is - cross over the subwoofer bit higher than the -3db point, unless that point is above 80 hz. Then it gets tricky because there can be issue of localizing the sound. If both subwoofer and mains can output enough bass at certain frequencies, then measurements helps in a big way for determining crossover. One can choose mains or speakers depending upon which one gives smoother response.

 

[Ambio]

..

I am not confusing these two. Did I ever said "air free" or "vacuum"? .

I probably misunderstood you when you said:-

Fs is the free air resonant frequency of a driver. Meaning, if the driver has no air resistance, this is the lowest frequency it can produce.......Bottom line is - No driver will be able to produce lower frequencies than Fs in an an-echoic chamber. Although, in actual rooms, room gain comes into picture and some speakers will give lower output.

which means you are referring to the lowest possible frequency that a driver produces without air. If there is air then there will be resistant. There is no two ways about it. Furthermore, I think drivers are way capable to go beyond Fs. The Manufacturer datasheet clearly shows that as the Morel was shown to go as low as 4Hz! even though the Fs was 39Hz.

.. That guidance is - cross over the subwoofer bit higher than the -3db point, unless that point is above 80 hz. Then it gets tricky because there can be issue of localizing the sound.

This is the most interesting part about crossover freq. Let's say your system is flat up to 81Hz and starts to drop 3dB at 80Hz. According to you, the subwoofer should be crossed just above 80Hz. Now, ignoring phase distortion,
that means to make the 80Hz to be as loud as the reference volume, let's say 85dB, you would cross the sub around 80Hz played at 82dB so that you get a flat frequencies going below 80Hz and the resultant loudness at 80Hz is 85dB.

But what would happen to 160Hz? Even taking a sub with 24dB slope, you will be having an extra energy of 58dB at 160Hz. How would that extra energy which will most likely be out of sync with the mains phase react in your room. I have posted about this on my other forums asking members to share room measurements so that we can analyze but they rather prefer to cite others opinion than experimenting themselves.


The second point is, if frequencies below 150Hz are omnidirectional, do you look under your bed trying to locate the source of the sound when you hear a thunder? You instantly knew that the thunder originates from the sky above. Even when someone plays low notes on the piano or violin, you don't suddenly unable to localize the sound. Our brain are preprogrammed to associate the omnidirectional low frequencies to a source. In the case of music, we expect it to originates from the soundstage.


A well setup sub should give you the feel that the lows are coming from music soundstage. That is difficult to explain but car sound enthusiasts know how to integrate their subwoofers to be part of the sound from their front speakers. They seemed to have better rules and system about good sound that many audiophiles.

 

[manoj.p]

I probably misunderstood you when you said:- which means you are referring to the lowest possible frequency that a driver produces without air. If there is air then there will be resistant. There is no two ways about it.

Sorry if the term "air resistance" confused you. I was simply talking about the resistance inside the box. Although, if there was a vacuum inside the box or outside, we wouldn't be talking about audio here.

Furthermore, I think drivers are way capable to go beyond Fs. The Manufacturer datasheet clearly shows that as the Morel was shown to go as low as 4Hz! even though the Fs was 39Hz.

Let's see what I said in that post.

Bottom line is - No driver will be able to produce lower frequencies than Fs in an an-echoic chamber. Although, in actual rooms, room gain comes into picture and some speakers will give lower output.

To reiterate: A driver by itself will not be able to produce lower frequencies than Fs. Now, a subwoofer box can be tuned to go lower than Fs depending upon ported or horn. Many prefer tuning above Fs to avoid distortion. Again, when tuned lower than Fs, some drivers will do fine, some will distort crazily.

Can you post the link to the Morel datasheet? I am doubtful that their measurements were done in an-echoic chamber or just the driver itself. But if it can do 4 Hz in An-echoic chamber as the specs say, then many (including me) in this world have found the ultimate low frequency sub woofer.

This is the most interesting part about crossover freq. Let's say your system is flat up to 81Hz and starts to drop 3dB at 80Hz. According to you, the subwoofer should be crossed just above 80Hz. Now, ignoring phase distortion,
that means to make the 80Hz to be as loud as the reference volume, let's say 85dB, you would cross the sub around 80Hz played at 82dB so that you get a flat frequencies going below 80Hz and the resultant loudness at 80Hz is 85dB.

But what would happen to 160Hz? Even taking a sub with 24dB slope, you will be having an extra energy of 58dB at 160Hz. How would that extra energy which will most likely be out of sync with the mains phase react in your room. I have posted about this on my other forums asking members to share room measurements so that we can analyze but they rather prefer to cite others opinion than experimenting themselves.

Yes, your points are correct that, if one crosses over at 80 Hz, then sub + mains would be 82 db each at 80 hz and sub would still be producing 58 db at 160 hz. But again how much lower the 24 db down is? Quite a lot because the loudness scale is logarithmic. The 58 db volume of subwoofer will not have much impact combined with mains. At the most it will add some weight. Just to give you an example - at crossover frequency, sub and mains are putting out 82 db each. Even if these two are co-located, the combined output would be 85 db. Every 3 db is twice as loud. Now do the math, and find out how much lower 58 db is compared to 82 db. Mains will easily mask the subwoofer.

As for measurements - I am planning to take some fresh measurements of my system. I would gladly posts the graphs. Would be interesting to see how the crossover interacts with real frequency response. Even I am curious

The second point is, if frequencies below 150Hz are omnidirectional, do you look under your bed trying to locate the source of the sound when you hear a thunder? You instantly knew that the thunder originates from the sky above. Even when someone plays low notes on the piano or violin, you don't suddenly unable to localize the sound. Our brain are preprogrammed to associate the omnidirectional low frequencies to a source. In the case of music, we expect it to originates from the soundstage.

No, I won't go look under the bed. But if I was paying attention with closed eyes (our hearing senses go up when we close eyes), I would be able to point out where the sound at 150 hz is coming from. Does not matter in real listening, but just stating it as such.

A well setup sub should give you the feel that the lows are coming from music soundstage. That is difficult to explain but car sound enthusiasts know how to integrate their subwoofers to be part of the sound from their front speakers. They seemed to have better rules and system about good sound that many audiophiles.

Not really experienced with Car enthusiasts, so can't comment about it. Most car enthusiasts I have seen are with big woofer and all you hear is one note bass. But agree with integration of subs with mains. The sub should be supplementing the mains, not overpowering those.

 

[Ambio]

Sorry if the term "air resistance" confused you. I was simply talking about the resistance inside the box. Although, if there was a vacuum inside the box or outside, we wouldn't be talking about audio here. .

I wasnt confused with "air resistance" but "no air resistance". An impossibility. Your explanation now causing more confusion. If there is a vacuum inside the box, you would still hear sound as the cone movements transfer the energy to the air molecules outside the driver.

To reiterate: A driver by itself will not be able to produce lower frequencies than Fs. Now, a subwoofer box can be tuned to go lower than Fs depending upon ported or horn. Many prefer tuning above Fs to avoid distortion. Again, when tuned lower than Fs, some drivers will do fine, some will distort crazily. .

May I ask how could sound (frequencies) appear from nowhere? If you say the lowest a driver could produce is the Fs (which, I humbly believe you are very wrong there) then how can a subwoofer box magically create sound or frequencies below the Fs. Are you mixing up Fs and F3?

Can you post the link to the Morel datasheet? I am doubtful that their measurements were done in an-echoic chamber or just the driver itself. But if it can do 4 Hz in An-echoic chamber as the specs say, then many (including me) in this world have found the ultimate low frequency sub woofer..

I did. I did. And I thought all these while we were talking based on some concrete manufacturer data in hand which I posted and based my arguments on.

.... But again how much lower the 24 db down is? Quite a lot because the loudness scale is logarithmic. .

What do you mean loudness scale is logarithmic? You are moving too fast that a novice like me struggling to understand the relevance of all terminology in this discussion.

Not really experienced with Car enthusiasts, so can't comment about it. Most car enthusiasts I have seen are with big woofer and all you hear is one note bass. But agree with integration of subs with mains. The sub should be supplementing the mains, not overpowering those.

I was talking about SQ car enthusiasts - the sound quality perfectionist in car audio. But what catches the eyes and ears are the SPL car enthusiasts - cheaper and noisier.

 

[manoj.p]

I wasnt confused with "air resistance" but "no air resistance". An impossibility.

So "No air resistance" means only vacuum and no other possibility? It's not like I said "No air".

Your explanation now causing more confusion. If there is a vacuum inside the box, you would still hear sound as the cone movements transfer the energy to the air molecules outside the driver.

Hmmm, interesting thought. But before we proceed on sound reproduction, what do you think will happen to that driver as soon as the vacuum is created in that speaker box?

May I ask how could sound (frequencies) appear from nowhere? If you say the lowest a driver could produce is the Fs (which, I humbly believe you are very wrong there) then how can a subwoofer box magically create sound or frequencies below the Fs.

As I said earlier, the driver itself (no box), in an-echoic chamber will not be able to go below Fs. Once you put it into a box, then you can tune it lower depending upon box type and changing parameters like Q. I am not speaker designer, so can't say how it works but do know that's how people are able to tune the drivers lower than Fs. Don't take my word on Fs, but do read on Thiel-Small parameters and do let me know if you read it differently somewhere.

Are you mixing up Fs and F3?

Nope. Read last para of my first post on the Fs discussion in this thread here.

I did. I did. And I thought all these while we were talking based on some concrete manufacturer data in hand which I posted and based my arguments on.

Well, I went through this thread and I did not see a datasheet posted by you which shows the output at 4Hz. If you are talking about the Morel datasheets in this post then please enlighten me where it shows that woofer has output at 4 Hz.

What do you mean loudness scale is logarithmic? You are moving too fast that a novice like me struggling to understand the relevance of all terminology in this discussion.

Not going fast or slow. Loudness scale is not linear and every 3 db increase is twice as loud. Same way, every 3 db lower is half as loud. So if you want to compare how loud 82 db is compared to 58 db, start doing the math. As for the relevance of this terminology to this discussion - its because you are talking about 58 db of subwoofer output at 160 Hz vs 85 db of mains output. You seemed to be aware about this when you said this about crossover.

Now, ignoring phase distortion,
that means to make the 80Hz to be as loud as the reference volume, let's say 85dB, you would cross the sub around 80Hz played at 82dB so that you get a flat frequencies going below 80Hz and the resultant loudness at 80Hz is 85dB.

 

[Ambio]

So "No air resistance" means only vacuum and no other possibility? It's not like I said "No air".

Hmmm, interesting thought. But before we proceed on sound reproduction, what do you think will happen to that driver as soon as the vacuum is created in that speaker box?



As I said earlier, the driver itself (no box), in an-echoic chamber will not be able to go below Fs. Once you put it into a box, then you can tune it lower depending upon box type and changing parameters like Q. I am not speaker designer, so can't say how it works but do know that's how people are able to tune the drivers lower than Fs. Don't take my word on Fs, but do read on Thiel-Small parameters and do let me know if you read it differently somewhere.


Nope. Read last para of my first post on the Fs discussion in this thread here.



Well, I went through this thread and I did not see a datasheet posted by you which shows the output at 4Hz. If you are talking about the Morel datasheets in this post then please enlighten me where it shows that woofer has output at 4 Hz.




Not going fast or slow. Loudness scale is not linear and every 3 db increase is twice as loud. Same way, every 3 db lower is half as loud. So if you want to compare how loud 82 db is compared to 58 db, start doing the math. As for the relevance of this terminology to this discussion - its because you are talking about 58 db of subwoofer output at 160 Hz vs 85 db of mains output. You seemed to be aware about this when you said this about crossover.

Dear Manoj, you raised few interesting points that I too erred in my understanding at the earlier stage of this "not very long" audiophile journey.

Once you put it into a box, then you can tune it lower depending upon box type and changing parameters like Q. I am not speaker designer, so can't say how it works but do know that's how people are able to tune the drivers lower than Fs.

There are many loudspeakers without enclosures. An example is here. You may want to compare the drivers Fs and the Loudspeakers usable frequency range. So how can these loudspeakers without enclosures(cabinets) are capable of outputting frequencies below Fs. The specs are exactly as the links I provided and you have to understand them. Please take your time.

Loudness scale is not linear and every 3 db increase is twice as loud.

I am sorry but your understanding of loudness is flawed. 3dB increase will not make it twice the louder. Nor would twice the power make it twice louder. Anyway, this a common mistake and I too once guilty of the misunderstanding.

But before we proceed on sound reproduction, what do you think will happen to that driver as soon as the vacuum is created in that speaker box?

Are you trying to say the atmospheric pressure would crush the driver? Then try small drivers. Or a mini driver where the surface pressure would not be too great for the amplifier to move the cone.

The point is - vibration of a surface of a vacuumed enclosure would transfer energy to the air next to it. Experiment yourself by vacuuming out a plastic mineral water bottle until the surface get sucked in. Now circle the indented spot and think that as a crude driver mounted in a vacuumed enclosure. Now try to press the edges of the indentation to pop it out. Do you hear a sound?

As I said earlier, the driver itself (no box), in an-echoic chamber will not be able to go below Fs.

Sorry to ask but do you really know what an anechoic chamber is? What magical property is in anechoic chamber that prevent drivers going beyond under Fs? And why even anechoic chamber is coming into Fs measurement?And do you know how Fs is determined in the first place?

I appreciate your feedback but you are making some serious misrepresentation of facts.

 

[manoj.p]

Dear Manoj, you raised few interesting points that I too erred in my understanding at the earlier stage of this "not very long" audiophile journey.

Dear Ambio,

Before you call my points as "errors", how about first proving those as errors?

There are many loudspeakers without enclosures. An example is here. You may want to compare the drivers Fs and the Loudspeakers usable frequency range. So how can these loudspeakers without enclosures(cabinets) are capable of outputting frequencies below Fs. The specs are exactly as the links I provided and you have to understand them. Please take your time.

I looked at your earlier specs and this one too. Show me one place where it shows the frequency response below Fs. Show me because you are going in circles and I do not understand where you see that there is output below Fs in all the specs you have linked to.

I am sorry but your understanding of loudness is flawed. 3dB increase will not make it twice the louder. Nor would twice the power make it twice louder. Anyway, this a common mistake and I too once guilty of the misunderstanding.

It's not my understanding. I am stating it because thats what is accepted by Audio engineers, scientists and Industry. And if you don't think 3 db increase is double the loudness, then to get 85 db, why you proposed to put sub and mains at 82 db each? Either that one is flawed or what you are saying now is flawed. You can't have it both ways.

And if 3db increase is not twice as loud, then what would be twice as loud? I would like to know.

Are you trying to say the atmospheric pressure would crush the driver? Then try small drivers. Or a mini driver where the surface pressure would not be too great for the amplifier to move the cone.

So, you don't think atmospheric pressure would crush the driver? Okay. Now, how much amp power do you think would be needed to move that cone? take just a guess.

The point is - vibration of a surface of a vacuumed enclosure would transfer energy to the air next to it. Experiment yourself by vacuuming out a plastic mineral water bottle until the surface get sucked in. Now circle the indented spot and think that as a crude driver mounted in a vacuumed enclosure. Now try to press the edges of the indentation to pop it out. Do you hear a sound?

Now this is getting very interesting. First, you assumed that "no air resistance" means vacuum and went off the tangent. Fine. But when you want to show that a vacuum chamber can make a sound, how about first creating a perfect vacuum? The mineral water bottle if completely vacuumed, it will be perfectly flat, from one side to another. In that case, you won't be able to press one part. Can you picture that? The only way you can still push on one part of the bottle is if there is air present in that bottle.

As for if a driver can move when its mounted in vacuum box - go read on Magdeburg hemisphere.

Sorry to ask but do you really know what an anechoic chamber is? What magical property is in anechoic chamber that prevent drivers going beyond under Fs? And why even anechoic chamber is coming into Fs measurement?And do you know how Fs is determined in the first place?

I do know anechoic chamber perfectly well, the question is - do you? And only reason I stated it because to take the room gain out of question when performing the measurements. You have been advocating room measurements a lot, so I assumed you know how much a room causes peaks or dips in measurements.

I appreciate your feedback but you are making some serious misrepresentation of facts.

As I said above, prove that I am misrepresenting facts before calling me out. From where I see it, you on the other hand got it all wrong.

 

[Kannan]

The driver impedance plays an important role in its frequency response. It reaches its maximum and becomes purely resistive at its open air resonance frequency (f/s) with maximum excursion.
Its impedance drops drastically below the f/s as at it becomes inductive. An improperly designed crossover, set to cover these lower frequencies can hence damage the driver.
Upward of f/s, the impedance starts to drop steadily and then shows a constant resistance for a wider frequency range for which the driver has been designed. This is normally mentioned as the nominal impedance of the driver (1 ohm, 2 ohm, 4 ohm or 8 ohm etc) in its T/S parameters.
Beyond this frequency range, the impedance again increases slowly and again becomes inductive.

To give an example, an 8 ohm driver (nominal impedance) can show a resistance of as much as 32 ohm at its f/s and drastically drop to as low as 2 ohms below the f/s, it will raise steadily beyond the f/s to 8 ohms and remain more or less constant for its designed frequency range and again slowly but steadily increase with frequency.

 

[Ambio]

The driver impedance plays an important role in its frequency response. It reaches its maximum and becomes purely resistive at its open air resonance frequency (f/s) with maximum excursion.
Its impedance drops drastically below the f/s as at it becomes inductive. An improperly designed crossover, set to cover these lower frequencies can hence damage the driver.
Upward of f/s, the impedance starts to drop steadily and then shows a constant resistance for a wider frequency range for which the driver has been designed. This is normally mentioned as the nominal impedance of the driver (1 ohm, 2 ohm, 4 ohm or 8 ohm etc) in its T/S parameters.
Beyond this frequency range, the impedance again increases slowly and again becomes inductive.

To give an example, an 8 ohm driver (nominal impedance) can show a resistance of as much as 32 ohm at its f/s and drastically drop to as low as 2 ohms below the f/s, it will raise steadily beyond the f/s to 8 ohms and remain more or less constant for its designed frequency range and again slowly but steadily increase with frequency.

Thank you! I hope now Fs becomes clearer. Fs is not the lowest frequency point of a driver. Thanks again Kannan.

 

[svvikram]

Svs subwoofers

hi, m new 2 ds forum, & i hav com across a person who goin 2 buySVS sub & claims its one of the best in the world but price wise-79ooo (PB 2000 model) so want 2 kno is it really worth every penny of it !!!! & is there any servce bakup in india for it???????? coulkd anybody dearly knows bout svs do help me out

 

[Ambio]

... Show me because you are going in circles and I do not understand where you see that there is output below Fs in all the specs you have linked to.

It is there. Understand what Fs is and you will see it in the link. See Kannan's post.

It's not my understanding. I am stating it because thats what is accepted by Audio engineers, scientists and Industry. .....
And if 3db increase is not twice as loud, then what would be twice as loud? I would like to know.

I would like to hear from the Audio engineers, scientists and Industry themselves. Show me. Anyone by asking google would have known the answer by now and yet you are still harping on this. Search for this phrase and you will have better understanding about loudness.

In the newsgroups these often misunderstood statements are explained rather less accurately. Decibels can also mean dBSPL or dBA, while a level change is always in dB. The perceived loudness of the sound depends on several factors: the amplitude, the sound pressure level, the frequency, and the time behaviour of the sound. A typical question on the internet: "Is 3 dB or 6 dB double the loudness?"
The answer is: "It is neither 3 dB, nor 6 dB ? it is closer to 10 dB".

So, you don't think atmospheric pressure would crush the driver? Okay. Now, how much amp power do you think would be needed to move that cone? take just a guess......Now this is getting very interesting. First, you assumed that "no air resistance" means vacuum and went off the tangent. Fine. But when you want to show that a vacuum chamber can make a sound, how about first creating a perfect vacuum? The mineral water bottle if completely vacuumed, it will be perfectly flat, from one side to another. In that case, you won't be able to press one part. Can you picture that? The only way you can still push on one part of the bottle is if there is air present in that bottle. As for if a driver can move when its mounted in vacuum box - go read on Magdeburg hemisphere.

No problem. Take a stronger bottle that can withstand 14 pounds per inch. Or just mount a tweeter (now don't tell me a tweeter is not a driver, ok?) on a PVC tube and vacuum it out. Or just anything to create a vacuum inside and a movement on the surface of the enclosure to see whether there will be sound or not. The question is will there be sound or not?

This is about your confusion about no air resistant. No air means no air. When there is no air then it becomes a vacuum. Fs is not caused by having no air resistant but...(I am sure you know by now after reading Kannan's post).

I do know anechoic chamber perfectly well, the question is - do you? And only reason I stated it because to take the room gain out of question when performing the measurements. You have been advocating room measurements a lot, so I assumed you know how much a room causes peaks or dips in measurements. As I said above, prove that I am misrepresenting facts before calling me out. From where I see it, you on the other hand got it all wrong.

This is another place where you are wrong, again and again. Why do you think they need to use anechoic chamber to measure Fs? Read Kannan's clue.

This thread was suppose to discuss about room response and preference. Then out of nowhere you brought:-
1) Fs and drivers cannot produce frequencies beyond that - which is totally irrelevant.
2) No air resistant - common sense says if there is air then there will be resistant. You argument is like telling a car's cruising speed reaching a point of "no air resistant". Illogical.
3) Then suddenly you brought in "Quite a lot because the loudness scale is logarithmic." and I am still trying to figure out why and how this is relevant.
4) I was rebutting your point that you say if there is vacuum then there wont be sound and you brought in Magdeburg hemisphere. Say in simple word that the atmospheric pressure would not be possible to make the cones to move. Maybe yes. But it might work for a condenser speaker or a tweeter with sealed enclosure.


Again, 3dB increase would not make it twice louder. Download free SPL apps and measure the 3dB difference. Or use online demo.

 

[Thad E Ginathom]

Hyphens are very useful.

I admit that much of the conversation is well beyond my technical understanding, but I have been wondering, for a few posts, if you guys are talking about no air resistance or no-air resistance.

 

[Ambio]

Hyphens are very useful.

I admit that much of the conversation is well beyond my technical understanding, but I have been wondering, for a few posts, if you guys are talking about no air resistance or no-air resistance.

Maybe. Never paid attention to my language lessons.

What do you understand by these? With and without hyphens...

1) Quote:

Fs is the free air resonant frequency of a driver. Meaning, if the driver has no air resistance, this is the lowest frequency it can produce.......; or

2)

Fs is the free air resonant frequency of a driver. Meaning, if the driver has no-air resistance, this is the lowest frequency it can produce.......

Probably, I misunderstood Manoj. But either sentence points to resistant being absent due to non existence of air. I maybe wrong and I stand corrected.

 

[sdurani]

But either sentence points to resistant being absent due to non existence of air.

You would have to be hyper-pedantic or attempting a game of semantic 'gotcha' to interpret it that way. Seems pretty clear that Manoj was talking about the resonant frequency of a driver in free air, as opposed to in an enclosure where the air is acting like a spring. No mention of non existence of air nor vacuum until you brought it up.

 

[Thad E Ginathom]

What do you understand by these? With and without hyphens...

Well, OK, I am more confused now.

But... by no air resistence I'm thinking that there is air, but it is free to move, not constrained by a box. By no-air resistance I suppose am absence of air. I don't know if that can even exist. Pump the air out of a sealed speaker cabinet, and the cabinet, let alone the drivers, would probably collapse (remember the tin can at school?).

Don't shout at me if my premises are wrong. As I said, technically I am out of my depth.

(cross-posted with sdurani who seems to have hit the nail on the head. With or without air.)

~

 

[Ambio]

You would have to be hyper-pedantic or attempting a game of semantic 'gotcha' to interpret it that way. Seems pretty clear that Manoj was talking about the resonant frequency of a driver in free air, as opposed to in an enclosure where the air is acting like a spring. No mention of non existence of air nor vacuum until you brought it up.

Good morning.

Did you read the whole thread? Since you mentioned that it is the resonant frequency of a driver in free air, which I agree, where did the part of no air resistant come about?

The reason i picked on that was because the Fs wasn't relevant at all for subwoofer crossovers setting. But I could be wrong and asked him to explain as I thought he could be very knowledgable of speakers parameters. He chose to introduce Fc while attempting to describe Fs. Again both were irrelevant to the subwoofers setting referred to in the previous posts. But he was repeating the same thing over and over again. No air resistance. So how can you explain the possiblity of a driver overcoming air resistance. Either it is totally irrelevant or there can be a magical moment at a specific frequency the driver suddenly frees itself from air resistant. That what's interest me.


In case you miss the earlier post,

Fs is the free air resonant frequency of a driver. Meaning, if the driver has no air resistance, this is the lowest frequency it can produce. The air in speaker cabinet acts like a spring and does not allow the driver to move freely, so it can't achieve Fs. This happens more so in a sealed box than vented

And rest of the twice loudness stuff. Waiting for your interpretation on that.

 

[Ambio]

Well, OK, I am more confused now.

But... by no air resistence I'm thinking that there is air, but it is free to move, not constrained by a box. By no-air resistance I suppose am absence of air. I don't know if that can even exist. Pump the air out of a sealed speaker cabinet, and the cabinet, let alone the drivers, would probably collapse (remember the tin can at school?).

Don't shout at me if my premises are wrong. As I said, technically I am out of my depth.

(cross-posted with sdurani who seems to have hit the nail on the head. With or without air.)

~

The confusion started because Manoj and you attempting to interpret in isolation. He described free air resonant of the driver with his own words.

Free air means :* air not under restraint (as by pressure or flow).

No air resistant is not the same as free air.

I was involved in some speaker evaluation for a friend who wanted to go big scale designing or modifying a certain brand of china made speakers. My role is limited to listening tests only. I have seen this person who is a qualified engineer with another sound engineer measuring the driver to see if matches the manufacturer specs. The Fs was measured on the workbench and not in anechoic chamber. Anechoic chamber measurement and testing is done for other things but for Fs it is more of electrical stuff.

 

[sdurani]

Since you mentioned that it is the resonant frequency of a driver in free air, which I agree, where did the part of no air resistant come about?

He was comparing it to air acting like a spring in an enclosure. He starts the sentence with "free air" but then uses the term "no air resistance". Apparent to me what he was describing, but then I wasn't playing a semantic game of gotcha: aha Manoj, you said "no air", and I'm going to deliberately interpret that to mean a complete vacuum.

And rest of the twice loudness stuff. Waiting for your interpretation on that.

Whenever I see anyone use the terms "3dB" and "twice" in the same sentence, it is obvious what they are talking about, whether they use the term output, power, loudness, SPL, volume, level, volume level, etc. I'm more interested in the point they are trying to get across than nitpicking the particular terms used.

 

[Ambio]

He was comparing it to air acting like a spring in an enclosure. He starts the sentence with "free air" but then uses the term "no air resistance". Apparent to me what he was describing, but then I wasn't playing a semantic game of gotcha: aha Manoj, you said "no air", and I'm going to deliberately interpret that to mean a complete vacuum. Whenever I see anyone use the terms "3dB" and "twice" in the same sentence, it is obvious what they are talking about, whether they use the term output, power, loudness, SPL, volume, level, volume level, etc. I'm more interested in the point they are trying to get across than nitpicking the particular terms used.

Be rational. I am being specific but you are now accusing me what I am not. And i have exercised restraint. Just like you, I am too interested in the point they are getting across. But it is my right to correct an error even if he is my friend because if I don't then I would look like an idiot defending the indefensible.

Sorry I don't buy any layman would say that a 3dB increase means twice the loudness. It is usually Somone reading audiophile forums or magazines that come up with "if one speaker is 90 dB then two would be 93dB". So two speakers means it is twice the loudness. That's what exactly happened here.

Is it so difficult to say that your friend erred in his explanation and got mixed up? And again, that's what happened here.

 

[sdurani]

Be rational.

I am being rational, just not pedantic.

Sorry I don't buy any layman would say that a 3dB increase means twice the loudness.

No one is asking you to buy it, just pointing out that I understand what someone is trying to say when they use the terms "3dB" and "twice" in the same sentence.

If someone tells me that their girlfriend eat like a bird, I understand what they're trying to say and have no urge to point out that birds eat 3-4 times their own body weight per day, because I know that's not what they meant.