# Port Air Speed



## Mike P. (Apr 6, 2007)

I'm familiar with air speed in subwoofers but not speakers. I've been modeling some full range ported speakers and the port being used is 1.75" diameter. Maximum air speed is 17 m/s at 50 hz. Is this acceptable?


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## brandonnash (Sep 11, 2006)

That is acceptable. If its st all audible you wouldn't be able to hear it unless you were listening directly to the port. The sound from the drivers at that point would be much louder than the port.
_Posted via Mobile Device_


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## Mike P. (Apr 6, 2007)

Thank you Brandon!


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## SteveCallas (Apr 29, 2006)

Hmm, I would double check that with Collo's Flare it program. I'm at relatives now so I can't check, but 17ms at 50hz with a 1.75" diameter port seems like it would be problematic :time-out:


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## Mike P. (Apr 6, 2007)

I checked around and for speakers they say 5% of the speed of sound, that works out to 17 m/s.


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## GPM (Jan 14, 2007)

Yeah, ~5% is what I use and it's never failed me, but FWIW, Richard Small concluded that 4.5% +/-10% or a 4.9% upper limit was a good rule-of-thumb. Oh well, what's 0.1% among friends?  Since we're more likely to hear sharp edge diffraction noise at these low vent machs, a slight rounding over is more important than whether a stock pipe size bumps it up to 6%. 

GM


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## Mike P. (Apr 6, 2007)

Thanks for the input, GM. It's appreciated. :T


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## GPM (Jan 14, 2007)

You're welcome!

BTW, here's the papers that started it all: http://www.readresearch.co.uk/html/articles.htm

GM


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