wouldn't the port material itself resonate?

PreSapian · 26th July 2010, 09:14 AM

it's a general practice to cover the entire enclosure on the inside to reduce the resonance. but why does the port always get left out of the treatment? the port itself is made out of plastic, which i should think can be excited easily sonically. and when it's a flared port, such as mine, the flange adds extra inches of diameter from the port that is left filled with void when the hole in the enclosure is cut out to accommodate the flare. i should think that the reasonable thing to do is to fill the reverse side of the flare to to address the void- with such molding material as concrete, which i shall be using. also cover the port itself with some felt or other acoustic absorbents as it has been done to the rest of the enclosure that the port will be residing in. of course im a novice builder and this is purely speculation based on my version of common sense. so i'd appreciate lots of inputs, thank you very much.

stoc005 · 26th July 2010, 12:17 PM

Maybe. Engineering is all about sweating the details and knowing which details matter. It is more important to get the length and diameter right than worrying about the plastic port resonating. If it bothers you, attach some damping material to the outside of plastic pipe.

454Casull · 26th July 2010, 12:34 PM

My guess is that there are no forces on the port which would cause it to resonate.

Brett · 26th July 2010, 01:47 PM

If you're using a cylindrical tube it's going to be pretty stiff anyway.

Andrew Eckhardt · 26th July 2010, 01:54 PM

Funny transmission of sound pressure from inside the cabinet at higher frequencies than the intended bandwidth of the port is a lot bigger problem than the port material moving, and anything you do to reduce this transmission except at quite high frequencies is a tradeoff against passband performance.

LineArray · 26th July 2010, 02:01 PM

I also guess the port material resonating itself being no
serious problem with BR.

Nevertheless a passive radiator might be the more "noble"
BR implementation, addressing problems like noise and
(organ pipe) port resonances.

26th July 2010, 09:14 AM	#1
PreSapian diyAudio Member Join Date: Sep 2009 Location: seoul	wouldn't the port material itself resonate? it's a general practice to cover the entire enclosure on the inside to reduce the resonance. but why does the port always get left out of the treatment? the port itself is made out of plastic, which i should think can be excited easily sonically. and when it's a flared port, such as mine, the flange adds extra inches of diameter from the port that is left filled with void when the hole in the enclosure is cut out to accommodate the flare. i should think that the reasonable thing to do is to fill the reverse side of the flare to to address the void- with such molding material as concrete, which i shall be using. also cover the port itself with some felt or other acoustic absorbents as it has been done to the rest of the enclosure that the port will be residing in. of course im a novice builder and this is purely speculation based on my version of common sense. so i'd appreciate lots of inputs, thank you very much.

26th July 2010, 12:34 PM	#3
454Casull diyAudio Member Join Date: Jan 2004 Location: Toronto, ON, Canada	My guess is that there are no forces on the port which would cause it to resonate. __________________ Building a 2.1 system out of a 3/4"x4'x8' sheet

26th July 2010, 02:01 PM	#6
LineArray diyAudio Member Join Date: Mar 2008	I also guess the port material resonating itself being no serious problem with BR. Nevertheless a passive radiator might be the more "noble" BR implementation, addressing problems like noise and (organ pipe) port resonances. __________________ Oliver, RFZ believer (?) www.dipol-audio.de

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26th July 2010, 12:17 PM	#2
stoc005 diyAudio Member Join Date: Feb 2007 Location: Midwest in the USA	Maybe. Engineering is all about sweating the details and knowing which details matter. It is more important to get the length and diameter right than worrying about the plastic port resonating. If it bothers you, attach some damping material to the outside of plastic pipe.

26th July 2010, 01:47 PM	#4
Brett diyAudio Member Join Date: Jan 2002	If you're using a cylindrical tube it's going to be pretty stiff anyway.

26th July 2010, 01:54 PM	#5
Andrew Eckhardt diyAudio Member Join Date: Nov 2005 Location: PA	Funny transmission of sound pressure from inside the cabinet at higher frequencies than the intended bandwidth of the port is a lot bigger problem than the port material moving, and anything you do to reduce this transmission except at quite high frequencies is a tradeoff against passband performance.

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