# What will happen if built a box tuned at the Fs of the sub?



## koolkool (Jun 13, 2008)

What will happen if i build a ported box which is the same freq as the Fs of the subwoofers ?


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## Volenti (Feb 17, 2010)

First you need to find the _new_ Fs of the driver in the enclosure, and then nothing particularly special will happen, other than being tuned to that frequency.


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## koolkool (Jun 13, 2008)

Im into SPL and just think if i tune my ported enclosure to the Fs of my sub ( eg 50 Hz is the Fs of my sub) will it increase the SPL ?Yes i will take a look again of the Fs of the sub inside the enclosure with LIMP software.
What will happen to the sub if i tune that way ? will it do good ? or will be a destructive issue will happen to the sub ?


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## TREETOP (Feb 11, 2009)

koolkool said:


> What will happen if i build a ported box which is the same freq as the Fs of the subwoofers ?


Sometimes, a better question to ask oneself, is "What will happen if I search first?"

http://www.diymobileaudio.com/forum/spl-science/83904-tuning-ported-enclosure-below-drivers-fs.html


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## koolkool (Jun 13, 2008)

TREETOP said:


> Sometimes, a better question to ask oneself, is "What will happen if I search first?"
> 
> http://www.diymobileaudio.com/forum/spl-science/83904-tuning-ported-enclosure-below-drivers-fs.html


I read the link, but in my case ,SPL , i dont really concerned about the distorsion or else as long as i get the highest score possible, but my concern is ,is it safe for the sub to play at its resonant frequency ?


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## TREETOP (Feb 11, 2009)

If you're looking for a true SPL setup, you'll be tuning your enclosure relative to _your vehicle's_ resonant frequency anyway, not your sub's. It will be higher than your sub's Fs.


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## subwoofery (Nov 9, 2008)

TREETOP said:


> If you're looking for a true SPL setup, you'll be tuning your enclosure relative to _your vehicle's_ resonant frequency anyway, not your sub's. It will be higher than your sub's Fs.


He's got a point  

Kelvin


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## koolkool (Jun 13, 2008)

I thought that if maybe i can get a subwoofer which has a Fs the same to my cabin gain frequency ,and made a box tuned at the Fs ,it will do good ? ..


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## Mr.Lovr (Mar 29, 2010)

doesnt the driver itself's impedance dramatically rise at its FS though . (way less power)
or that is out the window also with box tuning


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## mattyjman (Aug 6, 2009)

also in that thread listed there is talk about the fs of the driver changing once you put it in a box anyway... almost a useless spec. but you probably saw that already. 

find the peak of your cabin gain, tune your box to that frequency and go from there


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## Oliver (Jun 25, 2007)

Mr.Lovr said:


> doesnt the driver itself's impedance dramatically rise at its FS though . (way less power)
> or that is out the window also with box tuning


*Bingo ^^^*

How does one change the natural resonating frequency of an object ?

If you mass load a tuning fork or shave off some metal it will vibrate at a different frequency . . . albeit not as it was designed 



> *Fs Driver free air resonance, in Hz. This is the point at which driver impedance is maximum. *"This parameter is the free-air resonant frequency of a speaker. Simply stated, it is the point at which the weight of the moving parts of the speaker becomes balanced with the force of the speaker suspension when in motion. If you've ever seen a piece of string start humming uncontrollably in the wind, you have seen the effect of reaching a resonant frequency. _It is important to know this information so that you can prevent your enclosure from 'ringing'._ With a loudspeaker, the mass of the moving parts, and the stiffness of the suspension (surround and spider) are the key elements that affect the resonant frequency. As a general rule of thumb, a lower Fs indicates a woofer that would be better for low-frequency reproduction than a woofer with a higher Fs. This is not always the case though, because other parameters affect the ultimate performance as well."


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## tinctorus (Oct 5, 2009)

TREETOP said:


> If you're looking for a true SPL setup, you'll be tuning your enclosure relative to _your vehicle's_ resonant frequency anyway, not your sub's. It will be higher than your sub's Fs.


Does a 3 wheel bicycle even HAVE a resonant frequency???:laugh::laugh:


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