what the max Air velocity of bass reflex port?

Audist · 7th February 2005, 02:14 PM

Dear all,

What the good Air velocity for the bass reflex pip port? 5 m/s peak is okay? have a problem with this?

What the maximum? I read in some website "keep less from 17 m/s". Is truth?

Thanks

Ron E · 7th February 2005, 06:33 PM

Lower is always better, but 17m/s is often given as a practical maximum value. Once the port diameter equals the driver diameter, you probably wouldn't gain much by increasing port diameter. Basically , port size is a compromise based on what you can fit into a box. If you can't fit a large enough diameter port, you need to either live with port noise or use a PR. Flaring both ends of the port can help a great deal, BTW.

Audist · 7th February 2005, 07:31 PM

Thank you very much,

My port show 4.5 m/s in peak, even a little less...
My question if the diameter not less from 5 cm (internal) for the port, and the Air velocity is 4.5 m/s or 5 m/s peak. I can hear the port noise?

simon5 · 7th February 2005, 07:39 PM

You will not hear it.

Ron E · 7th February 2005, 09:43 PM

At what power level are you seeing 4.5 m/s?

IF you never plan to use above that power level, you are probably OK. Safest thing is to post your entire design so that errors in input, etc can be checked; but if you are confident you made none and that whatever program you used is correct, you are probably safe.

As a rule of thumb, a 5cm port should typically be safe up to 17cm driver and 7.5cm port up to a low excursion 25cm driver. Above that, you may need one or more 10cm ports.

7th February 2005, 02:14 PM	#1
Audist diyAudio Member Join Date: Dec 2004 Location: N/A	what the max Air velocity of bass reflex port? Dear all, What the good Air velocity for the bass reflex pip port? 5 m/s peak is okay? have a problem with this? What the maximum? I read in some website "keep less from 17 m/s". Is truth? Thanks

7th February 2005, 06:33 PM	#2
Ron E diyAudio Member Join Date: Jun 2002 Location: USA, MN	Lower is always better, but 17m/s is often given as a practical maximum value. Once the port diameter equals the driver diameter, you probably wouldn't gain much by increasing port diameter. Basically , port size is a compromise based on what you can fit into a box. If you can't fit a large enough diameter port, you need to either live with port noise or use a PR. Flaring both ends of the port can help a great deal, BTW. __________________ Our species needs, and deserves, a citizenry with minds wide awake and a basic understanding of how the world works. --Carl Sagan Science is a way of thinking much more than it is a body of knowledge. --Carl Sagan

7th February 2005, 07:39 PM	#4
simon5 diyAudio Member Join Date: Nov 2004 Location: Québec, Québec	You will not hear it. __________________ DIYaudio for President !

7th February 2005, 09:43 PM	#5
Ron E diyAudio Member Join Date: Jun 2002 Location: USA, MN	At what power level are you seeing 4.5 m/s? IF you never plan to use above that power level, you are probably OK. Safest thing is to post your entire design so that errors in input, etc can be checked; but if you are confident you made none and that whatever program you used is correct, you are probably safe. As a rule of thumb, a 5cm port should typically be safe up to 17cm driver and 7.5cm port up to a low excursion 25cm driver. Above that, you may need one or more 10cm ports. __________________ Our species needs, and deserves, a citizenry with minds wide awake and a basic understanding of how the world works. --Carl Sagan Science is a way of thinking much more than it is a body of knowledge. --Carl Sagan

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7th February 2005, 07:31 PM	#3
Audist diyAudio Member Join Date: Dec 2004 Location: N/A	Thank you very much, My port show 4.5 m/s in peak, even a little less... My question if the diameter not less from 5 cm (internal) for the port, and the Air velocity is 4.5 m/s or 5 m/s peak. I can hear the port noise?

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