Transient response, can you tell in advance???

[cotjones 10+ year member]

I wouldn't dispute Dan or Richard... But, hey.... audiohaulic... why don't you go ahead and explain to the class why the cone excursion of a driver is cut while frequency climbs...

And how exactly are you relating cone velocity to frequency ???

Dude, you're a fvcking idiot, Audioholic is completely right.

Frequency has just as much and more to do with cone velocity than amplitude.

Answer this question and think HARD about the answer.

if I played a 20 hz signal at an amplitude of (X) how many times a second does the assembly cycle?

Now if i played a 25 hz signal at the same amplitude (X) how many times per second does it cycle.

That is how frequency is related to cone velocity.

it's only part of the equation for cone velocity, but just as big of a part as amplitude.

 

[Haunz 10+ year member]

Audioholic my appologies for calling you an idiot.. you have backed yourself up well.. I do stick my foot in my mouth from time to time; but at least I can admit it..

Cotjones... I thought he was trying to relate frequency to velocity the way you appear to be.. that because the woofer is cycling at a higher rate the cone must be moving faster; and I knew that was not right..

 

[audioholic 5,000+ posts]

Audioholic my appologies for calling you an idiot.. you have backed yourself up well.. I do stick my foot in my mouth from time to time; but at least I can admit it...

We all put our foot in our mouths from time to time. What separates us all is how well we react when we realize we have done so. That was big of you to say Haunz. You just earned a new-found respect from me.

 

[cotjones 10+ year member]

Audioholic my appologies for calling you an idiot.. you have backed yourself up well.. I do stick my foot in my mouth from time to time; but at least I can admit it..

Cotjones... I thought he was trying to relate frequency to velocity the way you appear to be.. that because the woofer is cycling at a higher rate the cone must be moving faster; and I knew that was not right..

No, that is true, at a given amplitude the fact that the cone is cycling faster means that the cone velocity is higher...

changing the frequency will require a different stroke to obtain the same SPL but this doesn't in any way mean that frequency is not a deciding factor in cone velocity...

Like i said, "at the same amplitude stroke," is there a difference in the cone velocity of a sub playing 25Hz and one playing 20Hz?

 

[thch 10+ year member]

as a fun exercise, you can try winISD, and a sealed box for any detailed woofer. This will show you SPL vs. freqeuncy, as well as SPL vs excursion.

you'll find SPL scales with amplitude / frequency^2.

this means velocity scales with amplitude / frequency.

acceleration scales with amplitude.

the key is constant SPL. if you did have a higher frequency and the same excursion, the SPL would be higher.

 

[audioinformer 10+ year member]

Just wanted to throw this out there, I have done a few test (T/S) on subs, mid bass, and tweeters and here is the one thing that I have came across when it comes to transient response (or anything else for that matter). It is more dependent on the enclosure than any other factor and the reason that inductance made a much larger difference then added mass is because the heat (which basicaly is inductance) changes how the driver is in the enclosure.

Here is a good point, if you look at the TS parameters of any mid bass of any component set, it is not the same once you hook it up in an IB with the crossover (enclosure, filter, crossover, or what ever you want to call it). It is dependent on how the crossover effects the driver and how it changes the inductance along with all of the TS parameters.

If you take any subwoofer and run the TS parameters at 1 watt 1 meter or even 2.83 volts 1 meter, it is totaly different running the TS parameters of the subwoofer in an enclosure and as you add power to the driver, you are greatly changing the inductance as well as the BL of the driver. Actually, ever TS parameter is changed greatly in this state of the driver being filtered with real power running through it (anything over 1 watt of power).

Here is the information on an RE SX. It has an eight layer flat wound 40mm wide winding voice coil with a 12mm top plate. Lets look at it only free air with out any filter or enclosure first. At 1 watt 1 meter the BL is 21 and the inductance is low. There is a minimum amount of Xmax (about 2.5 to 4 mm Xmax) during this run at 1 watt. If you run the same test 100 watts the BL drops to 18.2 and the Xmax incresses to 9 to 11 mm. The voice coil over hang is 14mm over and under the top plate and as the voice coil gets closer to the edge or goes past the edge of the top plate, the BL drops and the inductance raises greatly!

If you placed this driver in the right size enclosure with the right power, it will not over Xmax and the coil will shed more heat giving you better inductance and kepping the transient response at very high levels. BUT, if you place the driver in the wrong enclosure with too much power, cliped power, or too low of input voltage into the amplifier. The BL will drop greatly everytime the coil starts to move any distance out of the gap, the inductance will go through the roof and your transient response will drop!! (Another huge factor with inductance is having too low of input voltage or amperage to your amplifier. An amplifier even with out a cliped singel with too low of input power or not enough amperage (too weak of a power source) will cause the inductance to raise and your transient response to drop) ..

 

[snb778 5,000+ posts]

There is no such thing as 'faster' or 'slower' subs. Think this is just a theory? Its not, its fact. Alterations in woofer 'speed' change the frequency its playing (a 60hz note requires the sub oscillate 60 times in one second). So if one sub was 'faster' or 'slower' than another, they would no longer even be playing the same frequency.
The guys at Stereo Integrity did not pioneer the idea that inductance relates to transient response rather than moving mass, Dan Wigging from Adire Audio did. His tech paper on the subjkect is pretty common knowledge these days. If I wasn't so lazy, Id find the link.

so why do some companies make extra light weight cones (like paper) and some use titanium or aluminum

 

[cotjones 10+ year member]

so why do some companies make extra light weight cones (like paper) and some use titanium or aluminum

to match the other characteristics of the sub... if one was objectively better than the rest they would all be the same

 

[Kyle_Keating 10+ year member]

Just wanted to throw this out there, I have done a few test (T/S) on subs, mid bass, and tweeters and here is the one thing that I have came across when it comes to transient response (or anything else for that matter). It is more dependent on the enclosure than any other factor and the reason that inductance made a much larger difference then added mass is because the heat (which basicaly is inductance) changes how the driver is in the enclosure.
Here is a good point, if you look at the TS parameters of any mid bass of any component set, it is not the same once you hook it up in an IB with the crossover (enclosure, filter, crossover, or what ever you want to call it). It is dependent on how the crossover effects the driver and how it changes the inductance along with all of the TS parameters.

If you take any subwoofer and run the TS parameters at 1 watt 1 meter or even 2.83 volts 1 meter, it is totaly different running the TS parameters of the subwoofer in an enclosure and as you add power to the driver, you are greatly changing the inductance as well as the BL of the driver. Actually, ever TS parameter is changed greatly in this state of the driver being filtered with real power running through it (anything over 1 watt of power).

Here is the information on an RE SX. It has an eight layer flat wound 40mm wide winding voice coil with a 12mm top plate. Lets look at it only free air with out any filter or enclosure first. At 1 watt 1 meter the BL is 21 and the inductance is low. There is a minimum amount of Xmax (about 2.5 to 4 mm Xmax) during this run at 1 watt. If you run the same test 100 watts the BL drops to 18.2 and the Xmax incresses to 9 to 11 mm. The voice coil over hang is 14mm over and under the top plate and as the voice coil gets closer to the edge or goes past the edge of the top plate, the BL drops and the inductance raises greatly!

If you placed this driver in the right size enclosure with the right power, it will not over Xmax and the coil will shed more heat giving you better inductance and kepping the transient response at very high levels. BUT, if you place the driver in the wrong enclosure with too much power, cliped power, or too low of input voltage into the amplifier. The BL will drop greatly everytime the coil starts to move any distance out of the gap, the inductance will go through the roof and your transient response will drop!! (Another huge factor with inductance is having too low of input voltage or amperage to your amplifier. An amplifier even with out a cliped singel with too low of input power or not enough amperage (too weak of a power source) will cause the inductance to raise and your transient response to drop) ..

not trying to make you wrong here, but i think your confusing power compression and inductance. First of all, loading a driver in the box is not going to change the TSP's of the driver itself unless you measure them wrong. I have measured woofers in small boxes, and if done right, they produce nearly the same TSP's as free air. you have to calculate the box volume very carefully. There is a larger degree of uncertainty too and minor changes in box volume lead to major differences in the meausrements. its really hard to get right.

if you just measure an impedance plot in a box vs free air, the are going to be totally different and the program will assume its a woofer in free air so the TSP's are going to be wrong unless you tell it its a sealed box of specific volume.

here are some good resources about measurements

http://www.libinst.com/technical.htm

if you're really interested in inductance, i recommend you read this paper.

http://www.cedrat.com/applications/software/doc/voice_coil_Celestion_loudspeaker.pdf

in short, i'll give it to you. the iron makes for a very good inductor core because it has high magnetic permeability. put current around an iron core, and you have an inductor that can store and then provide large amounts of magnetic energy.

iron is in steel, but steel is also partly conductive. Steel is one of the primary materials in a motor and acts as a lossy inductor as well a shorting system (like a shorting ring)

a voice coil is AC, so its going to charge and discharge the inductor (motor) each stroke, but it also has a moving magnetic field which moves thu the steel. Steel is used to complete the magnetic circuit of the fixed magnet, but it can also be interfered with from the moving magnetic field of the voice coil. If the steel is not 100% saturated, then the voice coils magnetic field is going to modulate the magnetic flux inside the steel. - flux modulation is basically the phenomena of steel being used as a DC magnetic return path as well as inadvertently used as an AC non-linear inductor, but like i said, steel is also like a shorting ring near the surface where eddy currents travel so it partly helps itself. But this has nothin to do with the box, its simply the voice coil and the motor interacting.

audible transient response is really silly because its really a matter of the delivery of sound rather than the distortion. we're talkin time domain stuff here

if you want to learn about the psychology of distortion pertaining to the time domain, Earl Geddes has done incredible work

http://www.gedlee.com/

in summery:

inductance is not transient response in terms of what we measure or hear in the time domain.

inductance does have a transient response in terms of how it interacts as a function of current thu the voice coil, but it does not affect the impulse response in the time domain, it reduces sensitivity by increasing impedance as a function of frequency.

they are TWO totally different things.

transient response is a generic word for a state change, so i think people get confused into thinking it only means one thing.

 

[audioholic 5,000+ posts]

so why do some companies make extra light weight cones (like paper) and some use titanium or aluminum

The weight of the cone/moving mass becomes more critical at higher frequencies. This is why you see more subs getting away with using heavier cone materials than you do mids.
Titanium and aluminum cones are for nothing more than marketing and aesthetics.

 

[cotjones 10+ year member]

The weight of the cone/moving mass becomes more critical at higher frequencies. This is why you see more subs getting away with using heavier cone materials than you do mids.
Titanium and aluminum cones are for nothing more than marketing and aesthetics.

Yeah, i forgot to mention looks... cone material is slightly imporantant, i'd worry more about surround matterial to be honest, lol

There are some focal speakers with domes made of beryllium

If i made subs i'd make the cones out of palladium so they could make my car defeat iron man

 

[audioinformer 10+ year member]

not trying to make you wrong here, but i think your confusing power compression and inductance. First of all, loading a driver in the box is not going to change the TSP's of the driver itself unless you measure them wrong. I have measured woofers in small boxes, and if done right, they produce nearly the same TSP's as free air. you have to calculate the box volume very carefully. There is a larger degree of uncertainty too and minor changes in box volume lead to major differences in the meausrements. its really hard to get right.
if you just measure an impedance plot in a box vs free air, the are going to be totally different and the program will assume its a woofer in free air so the TSP's are going to be wrong unless you tell it its a sealed box of specific volume.

here are some good resources about measurements

http://www.libinst.com/technical.htm

if you're really interested in inductance, i recommend you read this paper.

http://www.cedrat.com/applications/software/doc/voice_coil_Celestion_loudspeaker.pdf

in short, i'll give it to you. the iron makes for a very good inductor core because it has high magnetic permeability. put current around an iron core, and you have an inductor that can store and then provide large amounts of magnetic energy.

iron is in steel, but steel is also partly conductive. Steel is one of the primary materials in a motor and acts as a lossy inductor as well a shorting system (like a shorting ring)

a voice coil is AC, so its going to charge and discharge the inductor (motor) each stroke, but it also has a moving magnetic field which moves thu the steel. Steel is used to complete the magnetic circuit of the fixed magnet, but it can also be interfered with from the moving magnetic field of the voice coil. If the steel is not 100% saturated, then the voice coils magnetic field is going to modulate the magnetic flux inside the steel. - flux modulation is basically the phenomena of steel being used as a DC magnetic return path as well as inadvertently used as an AC non-linear inductor, but like i said, steel is also like a shorting ring near the surface where eddy currents travel so it partly helps itself. But this has nothin to do with the box, its simply the voice coil and the motor interacting.

audible transient response is really silly because its really a matter of the delivery of sound rather than the distortion. we're talkin time domain stuff here

if you want to learn about the psychology of distortion pertaining to the time domain, Earl Geddes has done incredible work

http://www.gedlee.com/

in summery:

inductance is not transient response in terms of what we measure or hear in the time domain.

inductance does have a transient response in terms of how it interacts as a function of current thu the voice coil, but it does not affect the impulse response in the time domain, it reduces sensitivity by increasing impedance as a function of frequency.

they are TWO totally different things.

transient response is a generic word for a state change, so i think people get confused into thinking it only means one thing.

You are right, you can get the right enclosure with the right power and get the same or close ts parameters off of a driver. BUT, that is really only good in a sound lab. I would say that out of every person on this entire site, I am pretty sure that less than 1% have an enclosure that will give them the same or even close to the same ts parameters of their driver in their enclosure in their car as it does free air in a controlled envoirment.

As for inductance, here is the defination for inductance.

Inductance is that property in an electrical circuit where a change in the current flowing through that circuit induces an EMF that opposes the change in current.

So, you are telling me that heat or moving the voice coil out of the magnetic gap will not change the inductance of the voice coil. Well, as soon as the voice coil is even or moves any amount of area out of the gap, you lose a great amounts of your electrical circuit. So if "inductance" is the amount of change in the electrical circuit that is unopposed by EMF current and you add heat to the circuit it will not change drasticly or losing half of the electrical circuit will not change "inductance" then I am wrong.

Transient response is mostly effected by incressing inductance of the driver. Incressing heat and lowering the magnetic energy of the driver will most effect the inductance and change the transient response of any driver in any enclosure or free air.

 

[Kyle_Keating 10+ year member]

You are right, you can get the right enclosure with the right power and get the same or close ts parameters off of a driver. BUT, that is really only good in a sound lab. I would say that out of every person on this entire site, I am pretty sure that less than 1% have an enclosure that will give them the same or even close to the same ts parameters of their driver in their enclosure in their car as it does free air in a controlled envoirment.
As for inductance, here is the defination for inductance.

Inductance is that property in an electrical circuit where a change in the current flowing through that circuit induces an EMF that opposes the change in current.

So, you are telling me that heat or moving the voice coil out of the magnetic gap will not change the inductance of the voice coil. Well, as soon as the voice coil is even or moves any amount of area out of the gap, you lose a great amounts of your electrical circuit. So if "inductance" is the amount of change in the electrical circuit that is unopposed by EMF current and you add heat to the circuit it will not change drasticly or losing half of the electrical circuit will not change "inductance" then I am wrong.

Transient response is mostly effected by incressing inductance of the driver. Incressing heat and lowering the magnetic energy of the driver will most effect the inductance and change the transient response of any driver in any enclosure or free air.

I don't really get where heat comes from here... point me in the direct of a formal research paper.

What im getting at about the TSP's is why are you measuring them in a box? The only valuable things to really measure are the impedance, impulse, frequency (off axis if its higher frequencies) and maybe distortion at that point. The box affects everything and that's why the system complete changes, but it the same set of equations for all woofers. if we're talking about inductance affects transient response. The TSP's of the driver don't actually change in a box, you just have other variables in the equation (box volume etc) that change the final set of curves, impedance, frequency response, impulse, etc etc....if you derive a final set of TSP's in a box, they are going to be wrong for that driver unless the software knows its modeling in a box.

What you're saying is like you're trying to measure the horsepower of a car on a dyno with the wrong number for the rotational inertia of the machine you're using... its not different, its simply wrong. i dont really know how else to explain it. does a car's horsepower change when you're driving into 50 mile per hour head winds? common this is silly. God ****it, i used the frigging car analogy again, i'm gonna hate myself for that.

my point about inductance is not what it does to the proclaimed electrical circuit, but why its caused physically. The inductor is simply a non-linear current source until its fully discharged that as stated opposed the current in the wire it acts on. The solution to the diff eq explains it best, its just a first order differential solution that shows a simply decay function for the current with respect to time.

physical explanation of a speaker:

Because we're dealing with AC, the inductor is going to store energy and then oppose it every period or stroke. The amount of inductance you're going to store in the motor is direct proportional to the amount of current thu the vc and the total amount that can be stored in the motor ie. the "inductance L". Its also non-linear with respect to displacement - that i can tell you complicates the **** to all hell which is in part why there is no good equation for it, only FEA results. So for higher frequencies, the inductor does not ever fully charge and its decay effects last during the entire stroke, for lower frequencies, it can be fully charged and discharged and that transient time only accounts for a smaller percentage of the stroke of the woofer therefore its effects are diminished.

This is fundamentally why inductance is OK for lower frequencies. At lower frequencies, 5 time constants defined at L/R, inductance/resistance, does not take up a significant percentage of the period. For higher frequencies, it does. If a woofer has higher inductance, it has longer transient response in the context of an inductor NOT acoustical context, BUT!!!!! this is not audible in the way you would expect, its simply a low pass filter effect and what you measure is simply a reduction of SPL as a function of frequency. This also shows up in the impedance, the imaginary component of the resistance changes as a function of frequency because of the differential equation presented.

Lastly, voice coils don't have inductance as you say. As i said before, its the motor that is the inductor. Like you quoted from wiki, the inductor opposes the current thu the coil it acts on until its fully charged or the current changes again. I took some time to post some not-so-easy to find resources on the matter into how they pertain to acoustics. The simply electrical circuits presented by wiki are far less complex than the non-linear inductor model of a loudspeaker.

 

[audioholic 5,000+ posts]

Why do we use car analogies so often? In my experience, people dont really understand cars very well either. lol

 

[Kyle_Keating 10+ year member]

Why do we use car analogies so often? In my experience, people dont really understand cars very well either. lol

true that true that.....

i hate stupid car analogies, i need to stop using them! haha