As subwoofers break in how are t/s parameters affected

[vehementSPL 10+ year member]

I kinda posted this on the end of another post but not in full detail and kinda wanted to start a new post on it. Ok from the point in which the sub is FIRST played. So if you tested a fresh sub for t/s parameters. ( I am sure it is sub dependent) BUT how much of a change can you expect in the t/s parameters. Also in which way does it affect the QES/QTS/QMS? like do the values go up or down after fully broken in and by how much? Also vas? what changes can you expect in vas. thanks

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[dan5505 10+ year member]

Ive heard that the FS, free air resonant frequency, goes down. But im new to t/s parameters, so dont quote me on that.

 

[munchies 10+ year member]

Example: The audioque HDC3 12'' has a fs of 43hz (when brand new). Supposedly over time as the sub breaks in, that number is supposed to drop somewhere in the neighborhood 32-35hz

As for QES/QMS/QTS, someone else will have to chime in.

 

[vehementSPL 10+ year member]

yeah I appreciate it. I knew fs dropped. Wasn't sure by how much but would like to know about the others

 

[newusername 10+ year member]

Break-in of a driver consists primarily of changes in Cms/Kms...the compliance of the suspension (Cms) increases, which is the same as saying the stiffnes of the suspension (Kms) decreases.

Since Cms is one of the primary thiele/small parameters from which all other thiele/small parameters are derived, it has a direct impact on Fs, Qes, Qms, Qts, and Vas.

I'm scrambling at the moment but I'll come back a bit later and post the math if you'd like.

 

[mrogowski 5,000+ posts]

Neil, you should put it in your signature //content.invisioncic.com/y282845/emoticons/tongue.gif.6130eb82179565f6db8d26d6001dcd24.gif

 

[vehementSPL 10+ year member]

Break-in of a driver consists primarily of changes in Cms/Kms...the compliance of the suspension (Cms) increases, which is the same as saying the stiffnes of the suspension (Kms) decreases.
Since Cms is one of the primary thiele/small parameters from which all other thiele/small parameters are derived, it has a direct impact on Fs, Qes, Qms, Qts, and Vas.

I'm scrambling at the moment but I'll come back a bit later and post the math if you'd like.

Yes PLEASE do. I know you prob won't be able to give exact changes. But typically which way will it change. like will vas go up or down. and the others. will the values go up or down and by how much (approx)

 

[80INCHES 5,000+ posts]

Neil, you should put it in your signature //content.invisioncic.com/y282845/emoticons/tongue.gif.6130eb82179565f6db8d26d6001dcd24.gif

I AGREE ALL NOOBS SHOULD KNOW THIS

80

 

[vehementSPL 10+ year member]

Ttt

 

[squeak9798 5,000+ posts]

Yes PLEASE do. I know you prob won't be able to give exact changes. But typically which way will it change. like will vas go up or down. and the others. will the values go up or down and by how much (approx)

Since Neil hasn't responded to this thread yet, suppose I'll try to be of assistance here.

Cms, as Neil previously mentioned, is the speaker's compliance (opposite of stiffness) and is the parameter that is going to change (increase) as a result of "break in" and the driver's suspension loosening up.

The change in Vas can be found by;

Vas = p * c^2 * Sd^2 * Cms

I'm not going to work out this one as the change is rather obvious. You can see that if Cms increases, Vas is going to increase proportionally....if Cms doubles, Vas will double.

Change in Fs can be found as follows;

Fs = [6.28*(Cms*Mms)^.5]^-1

So to take an example here, lets look at the Soundsplinter Rl-p;

Fs = [6.28*(.0002592*.1779)^.5]^-1 = 23.4 hz

Now let's look at what happens if Cms (compliance) increases...to make life easy lets just double the current Cms;

Fs = [6.28*(.0005184*.1779)^.5]^-1 = 16.6 hz

You can see that by doubling Cms, Fs decreased a considerable amount.

For Qes;

Qes = 2pi*Fs*Mms*Re/Bl^2

You can see that since Fs is in the numerator, if Fs decreases Qes is likewise going to decrease.

Qms = 2pi*Fs*Mms/Rms

As above, if Fs decreases Qms is going to likewise decrease.

And since Qts = Qms*Qes/Qms + Qes you can gather that if both Qes and Qms decrease, total driver Q (Qts) is going to likewise decrease.

And yes, I got lazy and didn't work out any of the other parameters besides Fs //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif But I wanted to work out Fs to show you how it changed since it affected Qes and Qms, and ultimately Qts. If you wanted to work them out yourself, the only parameter missing from most T/S lists is Rms which can be worked back out of the stated Qms figure as long as Mms is given.

 

[vehementSPL 10+ year member]

Since Neil hasn't responded to this thread yet, suppose I'll try to be of assistance here.

Cms, as Neil previously mentioned, is the speaker's compliance (opposite of stiffness) and is the parameter that is going to change (increase) as a result of "break in" and the driver's suspension loosening up.

The change in Vas can be found by;

Vas = p * c^2 * Sd^2 * Cms

I'm not going to work out this one as the change is rather obvious. You can see that if Cms increases, Vas is going to increase proportionally....if Cms doubles, Vas will double.

Change in Fs can be found as follows;

Fs = [6.28*(Cms*Mms)^.5]^-1

So to take an example here, lets look at the Soundsplinter Rl-p;

Fs = [6.28*(.0002592*.1779)^.5]^-1 = 23.4 hz

Now let's look at what happens if Cms (compliance) increases...to make life easy lets just double the current Cms;

Fs = [6.28*(.0005184*.1779)^.5]^-1 = 16.6 hz

You can see that by doubling Cms, Fs decreased a considerable amount.

For Qes;

Qes = 2pi*Fs*Mms*Re/Bl^2

You can see that since Fs is in the numerator, if Fs decreases Qes is likewise going to decrease.

Qms = 2pi*Fs*Mms/Rms

As above, if Fs decreases Qms is going to likewise decrease.

And since Qts = Qms*Qes/Qms + Qes you can gather that if both Qes and Qms decrease, total driver Q (Qts) is going to likewise decrease.

And yes, I got lazy and didn't work out any of the other parameters besides Fs //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif But I wanted to work out Fs to show you how it changed since it affected Qes and Qms, and ultimately Qts. If you wanted to work them out yourself, the only parameter missing from most T/S lists is Rms which can be worked back out of the stated Qms figure as long as Mms is given.

WOW I need to brush up on math skills. Hell I am not even sure what ^ means.... I didn't realize how rusty my math was till i seen those "problems"... wow...

 

[wong05tsx 10+ year member]

c^2 = c squared

c^3 = c cubed

c^4 = c to the 4th power

A x B = A times B

A * B = A times B

A(B) = A times B

AB = A times B

A(B+C) = (B+C) times A

A(blah x blah + blah) = Everything in paranthesis first, then multiplied by the coefficient A

Pi = 3.146583adkljgaklhdglaklgadlk

the ^ is a denotation of a superscript, since we don't have the option to do that on our keyboards

 

[vehementSPL 10+ year member]

c^2 = c squaredc^3 = c cubed

c^4 = c to the 4th power

A x B = A times B

A * B = A times B

A(B) = A times B

the ^ is a denotation of a superscript, since we don't have the option to do that on our keyboards

Ahhh thanks. sorry to sound like a complete idiot. I actually use to do pretty well in math. I just didn't recall that symbol

 

[AllDayMJ 10+ year member]

I AGREE ALL NOOBS SHOULD KNOW THIS

80

noobs dont know what a theil small paramater is even..they probably think its something like a cap and they know they need to get one ASAP..lol

 

[Eugenics 5,000+ posts]

WOW I need to brush up on math skills. Hell I am not even sure what ^ means.... I didn't realize how rusty my math was till i seen those "problems"... wow...

the latter is the value of which the former exponentially increases.

so 5^2 is 5 squared. 5x5.