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tuning versus resonance frequency


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yourm0m1 
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Posted: July 05, 2006 at 7:12 PM / IP Logged  
i am wondering what the differecne is basically if i enter the resonance frequency of a particular sub in the port calculator tool versus a particular tuning frequency? thanks for the information sorry im new to ported box building
aznboi3644 
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Posted: July 05, 2006 at 8:31 PM / IP Logged  
It's however you want your tuning...some say its ok to tune around the sub's Fs and some say to not...But its up to you.
stevdart 
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Posted: July 05, 2006 at 10:27 PM / IP Logged  

The resonant freq of the sub is not a limiting factor in tuning the box.  There are cases where the best result comes from tuning the box below Fs.  For example, a sub whose measurements and T/S parameters dictate that it should be used in a sealed box, but you choose to vent.  Oftentimes an unusually bad response curve occurs when the box is tuned to "normal" car audio ranges.  To get best response, a lower tuning freq is chosen.  Read this recent thread for a good example of this phenomena.

You will simply get little port output when the box is tuned like this.  But venting the box isn't always all about increasing SPL by adding the port response.  In the case as linked above, it's to get some deeper sub base from the sub that the sealed box wouldn't allow.  But the trade-offs can be a put-off.

The box tuning, on the other hand, once chosen and implemented becomes the limiting factor.  At below Fb (box tuning freq), the box has no control over the movement of the sub.  So when these lower sub tones arrive, the sub movement will be out of control.  This out of control flapping can easily damage the sub.  You could have a sub with a Fs (resonant freq) of 24 Hz in a vented box tuned to 40 Hz, and the sub can be damaged with tones well above its Fs.  The damage isn't done because you've allowed tones to arrive below Fs, but because you didn't limit the tones below box Fb.  So a strong signal at 34 Hz could wack your sub out.

Most vented sub applications require the use of a subsonic filter to keep out these too-low freqs.

Recommended:  learn all you can and enjoy your vented box-building experience.  I would say with all modesty that the sticky above "Guide: Using WinISD" is a good way to start.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
aznboi3644 
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Posted: July 06, 2006 at 1:37 AM / IP Logged  
Steve...exactly what I was gonna say but I was too lazy to type.
yourm0m1 
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Joined: April 25, 2006
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Posted: July 06, 2006 at 5:54 PM / IP Logged  
thanks for the help guys....im deff struggling with winISD.... here is an image of what i have does it look correct at all?
https://img523.imageshack.us/img523/9826/comp103mm.jpg
aznboi3644 
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Posted: July 06, 2006 at 9:26 PM / IP Logged  
Well that curve is alright...what is your tuning freq??
Your F3 is around 36hz with that tuning...should be fine though.
yourm0m1 
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Posted: July 09, 2006 at 5:08 PM / IP Logged  
well i went with the dimensions that i figured up with the calculators on here and so far id say it came out pretty damn good....world of difference vs. my dual chamber sealed box
heres a quick pic...ill start another thread with my build sometime thanks again for the info
yourm0m1 
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Member spacespace
Joined: April 25, 2006
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Posted: July 09, 2006 at 5:31 PM / IP Logged  
opps forgot the image
http://xs.to/codes.php?f=inside2.JPG&h=xs103&d=06281

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