Le inductance Relevency in Subwoofers

[annunaki]

I also think that the "tight" bass comes from the mid range speakers. A properly crossed over subwoofer can sound accurate, but tight is not a phrase I would use.

Accuracy, regardless of size, is largely dictated by Le or inductance. It is the electrical "weight" of the driver. The lower the Le the more accurate the speaker. Assuming of course it (the subwoofer driver) uses a fairly linear motor and suspension.

A small woofer will have to move farther to produce the same output and /or frequency (if the frequency is low) of a larger driver.

For instance, say we have a 15" subwoofer playing a 30hz note at 80db. It is moving just 5mm peak to peak (i.e. linear p2p of 15mm for the 15" driver). For a 10" driver (i.e. 10" woofer linear p2p is 20mm) to produce the same level of output it may have to move about 15mm to equal the 15. We are getting close to the linear limits of the 10" woofer. It is running near it's maximum output levels. Where as with the 15" woofer we have much more to go.

Note:These numbers are all examples and are not real world ratios.

 

[WmAx]

Note: This thread was not originally about the topic that is now the thread title. Originally, Le was mentioned casually, and the thread was later split by a moderator. Please consider this when you start from the top of this thread.

Accuracy, regardless of size, is largely dictated by Le or inductance. It is the electrical "weight" of the driver. The lower the Le the more accurate the speaker. Assuming of course it (the subwoofer driver) uses a fairly linear motor and suspension.

Le is irrelevant in a subwoofer. Le dictates the high frequency response(it acts as a 1st order low pass filter). It is not a factor for woofer quality.

For instance, say we have a 15" subwoofer playing a 30hz note at 80db. It is moving just 5mm peak to peak (i.e. linear p2p of 15mm for the 15" driver). For a 10" driver (i.e. 10" woofer linear p2p is 20mm) to produce the same level of output it may have to move about 15mm to equal the 15. We are getting close to the linear limits of the 10" woofer. It is running near it's maximum output levels. Where as with the 15" woofer we have much more to go.

Note:These numbers are all examples and are not real world ratios.

Right, not real world ratios. In real world use, in a normal size room, playing back music, two 10" high quality subwoofers, in a properly designed ported enclosure would probably move no more than 1mm at any point, if they were set to the same relative SPL as the mains. Now, for home theatre it's a little different. The LFE portions of some tracks(especially in action movies) may be of such high amplitude in relation to the rest of the soundtrack that it may cause significant movement of the same two 10" subwoofers.

-Chris

 

[MacManNM]

I also think that the "tight" bass comes from the mid range speakers. A properly crossed over subwoofer can sound accurate, but tight is not a phrase I would use.

Accuracy, regardless of size, is largely dictated by Le or inductance. It is the electrical "weight" of the driver. The lower the Le the more accurate the speaker. Assuming of course it (the subwoofer driver) uses a fairly linear motor and suspension.

A small woofer will have to move farther to produce the same output and /or frequency (if the frequency is low) of a larger driver.

For instance, say we have a 15" subwoofer playing a 30hz note at 80db. It is moving just 5mm peak to peak (i.e. linear p2p of 15mm for the 15" driver). For a 10" driver (i.e. 10" woofer linear p2p is 20mm) to produce the same level of output it may have to move about 15mm to equal the 15. We are getting close to the linear limits of the 10" woofer. It is running near it's maximum output levels. Where as with the 15" woofer we have much more to go.

Note:These numbers are all examples and are not real world ratios.

What we agree? Mark this date down! You are 100% correct.

 

[MacManNM]

Le is irrelevant in a subwoofer. Le dictates the high frequency response(it acts as a 1st order low pass filter). It is not a factor for woofer quality.

-Chris

You are totally wrong on this one. The Inductance of most woofers is too small to make a difference. A 4-ohm speaker, with 23mH inductance won’t start to cut off until around 1.7KHz. Then it’s a 6 db/octave roll off after that. The Le is what denotes a good speaker, the lower the inductance the more accurate the amp can drive it. There becomes a tradeoff, the SPL will suffer when the coil gets too small, and enormous amounts of power are required to make the fields to move the motor.

 

[WmAx]

The Le is what denotes a good speaker, the lower the inductance the more accurate the amp can drive it. There becomes a tradeoff, the SPL will suffer when the coil gets too small, and enormous amounts of power are required to make the fields to move the motor.

Le, in itself, is irrelevant to woofer quality. Le can only have an effect on the output, if said Le is of sufficient value to be reactive within the bandwidth the woofer is used within(thus it acts exactly like, and is a low pass filter). Other than Le affecting frequency response, which it won't, if a woofer is used within it's intended bandwidth, Le affects nothing else that is of audible relevance.

Based on your comment about SPL, I suspect you mean to refer to (DCR)Re, not Le. But DCR of a speaker is not as important as it's plotted impedance.

-Chris

 

[MacManNM]

Le, in itself, is irrelevant to woofer quality. Le can only have an effect on the output, if said Le is of sufficient value to be reactive within the bandwidth the woofer is used within(thus it acts exactly like, and is a low pass filter). Other than Le affecting frequency response, which it won't, if a woofer is used within it's proper bandwidth, Le affects nothing else that is of audible relevance.

Based on your comment about SPL, I suspect you mean to refer to (DCR)Re, not Le. But DCR of a speaker is not as important as it's plotted impedance.

-Chris

Do the math. 25mH, 4ohm Z, and tell me where the cutoff starts. Not like it matters, it's 6db /octave anyhow.

SPL, 1w in= Xdb out, as the inductance goes down so does Xdb out, but the accuracy of the motor increases. Basic physics.

 

[WmAx]

Do the math. 25mH, 4ohm Z, and tell me where the cutoff starts. Not like it matters, it's 6db /octave anyhow.

25mH is not represenative of any woofer of which I am aware. 1.5-3 mH is typical on large woofers. It does not make sense to use 25mH as an example.

SPL, 1w in= Xdb out, as the inductance goes down so does Xdb out, but the accuracy of the motor increases. Basic physics.

Get your facts straight. How can SPL go down as inductance goes down, at any frequency? SPL would increase as inductance was lowered, if you begin your reference at a frequency which the inductive field is reactive(filtering). Again, as you keep referring to 'accuracy', I suspect you are referring to Re, which affects total dampening factor.

-Chris

 

[MacManNM]

25mH is not represenative of any woofer of which I am aware. 1.5-3 mH is typical on large woofers. It does not make sense to use 25mH as an example.



Get your facts straight. How can SPL go down as inductance goes down, at any frequency? SPL would increase as inductance was lowered, if you begin your reference at a frequency which the inductive field is reactive(filtering). Again, as you keep referring to 'accuracy', I suspect you are referring to Re, which affects total dampening factor.

-Chris

its 2.5 mH, @ 4 ohms Z. typo Please do the math already.

You get your facts straight, as Le goes down the ability of the coil to create a field decreases, therefore you need more power to achieve the same field strength. You are thinking of impedance.

 

[WmAx]

its 2.5 mH, @ 4 ohms Z. typo Please do the math already.

I fail to understand why the result is relevant to your argument.

You get your facts straight, as Le goes down the ability of the coil to create a field decreases, therefore you need more power to achieve the same field strength. You are thinking of impedance.

It appears, in the regards of SPL, we were talking about different things. I was referring to inductive reactance, as a filter(relative to reactive and non-reactive bands), where as you are talking about the EMF in the scope of motor efficiency. But anyways, you have not yet explained what audible benefit is caused directly by lower inductance, as a sole variable, in a woofer. Please, explain.

-Chris

 

[MacManNM]

I fail to understand why the result is relevant to your argument.

You also said:

Le is irrelevant in a subwoofer. Le dictates the high frequency response(it acts as a 1st order low pass filter). It is not a factor for woofer quality.

My point is that it is not a low pass filter in the freq area in which we are working. So your statement is totaly wrong.

It appears, in the regards of SPL, we were talking about different things. I was referring to inductive reactance, as a filter(relative to reactive and non-reactive bands), where as you are talking about the EMF in the scope of motor efficiency. But anyways, you have not yet explained what audible benefit is caused directly by lower inductance, as a sole variable, in a woofer. Please, explain.

-Chris

If you would drop this whole filter thing, it's crap and meaningless. Do the math and you will see.

The lower the motor efficiency, the more control the amp has over it. There is less "feedback" generated by the motor. The motor also will act more linear, because there are no artificial fields, and the fields can be controlled by the amplifier, much faster and with greater accuracy.

 

[WmAx]

If you would drop this whole filter thing, it's crap and meaningless. Do the math and you will see.

You missed my point, apparently. It was my contention all along(if you would pay attention to my replies) that inductance does not filter the bandwidth that the woofer is designed to operate within.

The lower the motor efficiency, the more control the amp has over it. There is less "feedback" generated by the motor. The motor also will act more linear, because there are no artificial fields, and the fields can be controlled by the amplifier, much faster and with greater accuracy.

You have not yet given a satisfactory explanation. The motor efficiency, as a stand alone variable, has no meaning, just like inductance as a lone variable has no meaning to audible sound quality. Basicly, it seems your contention is much like that of those people that claim higher BL = a better driver. Again, this is a sole variable, and can not be used as a quality measure by itself, either. But it's a very similar debate to this one. You can argue better control by the amplifier, but what it all comes down to in reality is frequency response, which is not a sum of any single variable, but of many, including the bass alignment(which is a combination of driver parameters and box parameters), amplifier source impedance, wire/network Re in series to the driver, etc.. Then of course, one can also stray off into a tangent such as motor linearity in this type of discussion, which is another matter entirely(and a dynamic situation also).

-Chris

 

[MacManNM]

You missed my point, apparently. It was my contention all along(if you would pay attention to my replies) that inductance does not filter the bandwidth that the woofer is designed to operate within.

Le is irrelevant in a subwoofer. Le dictates the high frequency response(it acts as a 1st order low pass filter).

I guess I need to pay better attention.

You have not yet given a satisfactory explanation. The motor efficiency, as a stand alone variable, has no meaning, just like inductance as a lone variable has no meaning to audible sound quality. Basicly, it seems your contention is much like that of those people that claim higher BL = a better driver. Again, this is a sole variable, and can not be used as a quality measure by itself, either. But it's a very similar debate to this one. You can argue better control by the amplifier, but what it all comes down to in reality is frequency response, which is not a sum of any single variable, but of many, including the bass alignment(which is a combination of driver parameters and box parameters), amplifier source impedance, wire/network Re in series to the driver, etc.. Then of course, one can also stray off into a tangent such as motor linearity in this type of discussion, which is another matter entirely(and a dynamic situation also).

-Chris

As the inductance decreases, the reactance of the speaker also decreases. It is that simple. If you don't understand the audible benefit of that then you need to take a class on electronics.

This is pointless, you say one thing, then turn around and say the opposite.

 

[WmAx]

Originally Posted by WmAx
Le is irrelevant in a subwoofer. Le dictates the high frequency response(it acts as a 1st order low pass filter).
I guess I need to pay better attention.

Yes, you do need to pay better attention. And as I specifcally stated also: "Other than Le affecting frequency response, which it won't, if a woofer is used within it's intended bandwidth, Le affects nothing else that is of audible relevance."

So, Le does effect HF limitations/response. But I stated that it is irrelevant for woofers. The HF cutoff point is not within the intended band of the woofer.

As the inductance decreases, the reactance of the speaker also decreases. It is that simple. If you don't understand the audible benefit of that then you need to take a class on electronics.

I understand the reactions. But what are the audible ramifications? For example, explain: what differences exactly, in terms of acoustic waveform output from the driver, is going to be audible if you have two identical subwoofers, with the only difference being Le(with the alignment adjusted for each one to have an identical frequency response, since Le modifcation will affect driver Q), one at 1.5mH, one at 2mH, and you have level matched gain to within 0.1db.

So, instead of just claiming that lower Le, as a lone variable, will sound better; please explain what exactly in the acoustic output from the woofer is audibly worse. If it sounds worse, then measurable/quantifiable effects will be present in the acoustic waveform, that can be matched/correlated with perceptual research of human thresholds.

-Chris

 

[MacManNM]

Yes, you do need to pay better attention. And as I specifcally stated also: "Other than Le affecting frequency response, which it won't, if a woofer is used within it's intended bandwidth, Le affects nothing else that is of audible relevance."


So, Le does effect HF limitations/response. But I stated that it is irrelevant for woofers. The HF cutoff point is not within the intended band of the woofer.

You didn't amend this statement until you realized you were wrong. This was your first quote:

Le is irrelevant in a subwoofer. Le dictates the high frequency response(it acts as a 1st order low pass filter).

That statement isn't true in the context of this discussion.

I understand the reactions. But what are the audible ramifications? For example, explain: what differences exactly, in terms of acoustic waveform output from the driver, is going to be audible if you have two identical subwoofers, with the only difference being Le(with the alignment adjusted for each one to have an identical frequency response, since Le modifcation will affect driver Q), one at 1.5mH, one at 2mH, and you have level matched gain to within 0.1db.

So, instead of just claiming that lower Le, as a lone variable, will sound better; please explain what exactly in the acoustic output from the woofer is audibly worse. If it sounds worse, then measurable/quantifiable effects will be present in the acoustic waveform, that can be matched/correlated with perceptual research of human thresholds.

-Chris

I'm sorry you don't see how this relationship with amp / drivers really works. It would take me 1/2 a day to properly explain this, and when I got done you would say that I couldn't prove that it's audible. You and the others on this site love to use this subjective term so that there is no way for anyone to make their case. The target is always moving.

 

[WmAx]

You didn't amend this statement until you realized you were wrong. This was your first quote:



That statement isn't true in the context of this discussion.

Inductance does limit the maximum high frequency response of a woofer. I did not amend anything, I clarified that it was irrelevant in the context of the intended bandwidth in real-world application. This is like a repeat of that vinyl thread a few months back: you seem to wrongly pick things out of context, and/or just don't comprehend things very well.

I'm sorry you don't see how this relationship with amp / drivers really works. It would take me 1/2 a day to properly explain this, and when I got done you would say that I couldn't prove that it's audible. You and the others on this site love to use this subjective term so that there is no way for anyone to make their case. The target is always moving.

All I asked you to do was to demonstrate/describe the difference in the acoustic output waveform that would be audibly inferior, due to the lone variable of inductance, comparing 1.5mH to 2.0mH inductance voice coil in a subwoofer(all other parameters equal). It should be trivial for you to explain the artifacts in the acoustic output waveform from the 2.0mH VC subwoofer as compared to the 1.5mH one, that are so blatantly audible, if indeed you have the comprehensive understanding that you imply. It's also rather odd how you seem to imply that the word audible is not valid in the context of anything that you are challenged upon. If audible is not a valid term in audio as in dealing with what probability a person has in hearing something, then the entire foundation of audio science/engineering and the AES is a sham, since much of it deals with determining what probable audible thresholds and/or factors that contribute to audibility across a large statisical sample base of subjects.

-Chris

 

[Francious70]

I'm sorry Chris, but inductance is VERY important to woofers. Read this article.

http://www.adireaudio.com/Files/TechPapers/WooferSpeed.pdf

Paul

 

[WmAx]

I'm sorry Chris, but inductance is VERY important to woofers. Read this article.

http://www.adireaudio.com/Files/TechPapers/WooferSpeed.pdf

Paul

I am very familiar with the Adire audio paper. However, it is ironically evidence supporting that my prior statement was correct: inductance can only affect high frequency extension. I should make it clear that their reference to transient response seems to be a red herring, when used in the context of this(it is not a red herring in the scheme of the Adire paper itself, but it's being misapplied in this discussion) discussion. Here is why: transient response is a derivative of frequency response. Any two devices that are compared: the one with a further extended high frequency response technically has a faster transient response. But, this is audibly irrelevant within the frequency band that a large woofer/subwoofer is operated.

-Chris

 

[MacManNM]

Inductance does limit the maximum high frequency response of a woofer. I did not amend anything, I clarified that it was irrelevant in the context of the intended bandwidth in real-world application. This is like a repeat of that vinyl thread a few months back: you seem to wrongly pick things out of context, and/or just don't comprehend things very well.

If you care to go back and actually read the posts, I am the one who stated that the Le of a driver has no affect in this application, not you.




All I asked you to do was to demonstrate/describe the difference in the acoustic output waveform that would be audibly inferior, due to the lone variable of inductance, comparing 1.5mH to 2.0mH inductance voice coil in a subwoofer(all other parameters equal). It should be trivial for you to explain the artifacts in the acoustic output waveform from the 2.0mH VC subwoofer as compared to the 1.5mH one, that are so blatantly audible, if indeed you have the comprehensive understanding that you imply. It's also rather odd how you seem to imply that the word audible is not valid in the context of anything that you are challenged upon. If audible is not a valid term in audio as in dealing with what probability a person has in hearing something, then the entire foundation of audio science/engineering and the AES is a sham, since much of it deals with determining what probable audible thresholds and/or factors that contribute to audibility across a large statisical sample base of subjects.

-Chris[/QUOTE]

It is only valid if it can be referenced to a measurement. Do you agree that impedance has an effect on the performance of a driver with a given amplifier? IE, some amplifiers have a harder time with loads that vary wildly.

 

[WmAx]

If you care to go back and actually read the posts, I am the one who stated that the Le of a driver has no affect in this application, not you.

I will quote the posts at subject here, in chronological order, in an attempt to clear up this apparent confusion:

(1)WmAx: Le is irrelevant in a subwoofer. Le dictates the high frequency response(it acts as a 1st order low pass filter). It is not a factor for woofer quality.

(2)MacManNM: You are totally wrong on this one. The Inductance of most woofers is too small to make a difference. A 4-ohm speaker, with 23mH inductance won’t start to cut off until around 1.7KHz. Then it’s a 6 db/octave roll off after that. The Le is what denotes a good speaker, the lower the inductance the more accurate the amp can drive it. There becomes a tradeoff, the SPL will suffer when the coil gets too small, and enormous amounts of power are required to make the fields to move the motor.

(3)WmAx: Le, in itself, is irrelevant to woofer quality. Le can only have an effect on the output, if said Le is of sufficient value to be reactive within the bandwidth the woofer is used within(thus it acts exactly like, and is a low pass filter). Other than Le affecting frequency response, which it won't, if a woofer is used within it's intended bandwidth, Le affects nothing else that is of audible relevance.

Analysis: In (1) I state that Le is irrelevant in a subwoofer. I state that Le dictates high frequency response. It is a fact that high frequency response limits the high frequency response of a woofer. I did not say anything about this being relevant to the bandwidth in which the woofer is intended to be used. You follow up in (2) and state The Inductance of most woofers is too small to make a difference. A 4-ohm speaker, with 23mH inductance won’t start to cut off until around 1.7KHz. Then it’s a 6 db/octave roll off after that. I respond in (3) by saying Other than Le affecting frequency response, which it won't, if a woofer is used within it's intended bandwidth, Le affects nothing else that is of audible relevance. to clarify my initial statement, since you seemed to assume I meant something that I never said. I never stated that inductance affects a large woofer/subwoofer within it’s intended passband. You assumed that’s what I meant.

It is only valid if it can be referenced to a measurement. Do you agree that impedance has an effect on the performance of a driver with a given amplifier? IE, some amplifiers have a harder time with loads that vary wild

Yes, impedance can effect performance of a driver with a given amplifier. It is an issue only in the cases that a speaker has a very low nominal impedance that is below what typical amplifiers are designed to use or the amplifier has a very high output impedance(not common).

-Chris

 

[MacManNM]

The fact is that inductance is proportional to reactance. The greater the reactance the greater the delta in impedance, also the phase variance is greater (not taking into account the dc resistance of the coil because it is always there). When placed in a room, peaks and nulls are going to be greater with a higher inductance driver. Thus a difference can be measured and heard. This is not even taking into consideration the ability of an amplifier to drive a wildly changing impedance load. This will affect the quality of the output waveform. All of the effects are exaggerated when room acoustics, and amplifier linearity are considered. This is the reason some drivers are better than others.