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Port distortion

drummerman

New member
Jan 18, 2008
540
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Mmmh, something I haven't noticed much before, even at high volume;

Listening to Bjorks Telegram CD, last track 'Headphones Remix', the deep bass makes both my Ushers and Mission's ports distort like crazy (reasonably high volume).

I have plently of bass heavy music, a lot of double bass on my jazz stuff and some electronica but never noticed it to that extend.

Its not so much mid/bass driver doubling (normal for smaller drivers when over driven) but the actual ports farting/distorting like mad ... Amplifier independent too, both with the higher power Sony and cyrus.

regards
 

alchemist 1

Well-known member
Mar 28, 2012
85
2
18,545
drummerman said:
Mmmh, something I haven't noticed much before, even at high volume;

Listening to Bjorks Telegram CD, last track 'Headphones Remix', the deep bass makes both my Ushers and Mission's ports distort like crazy (reasonably high volume).

I have plently of bass heavy music, a lot of double bass on my jazz stuff and some electronica but never noticed it to that extend.

Its not so much mid/bass driver doubling (normal for smaller drivers when over driven) but the actual ports farting/distorting like mad ... Amplifier independent too, both with the higher power Sony and cyrus.

regards Sounds like brussel sprout syndrome ......:)
 

drummerman

New member
Jan 18, 2008
540
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0
David@FrankHarvey said:
Some manufacturers pay more attention to port design than others.
Indeed.

Ports, the work of the devil but almost inevitable in todays designs, should be flared on both sides. Needless to say mine aren't.

However, I'm on the case.

regards
 

davedotco

New member
Apr 24, 2013
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I am never entirely comfortable putting really deep bass into smallish ported loudspeakers. Clearly at some point (frequency) the bass cone will become 'unloaded' and you will get excessive cone movement causing the speaker to try and move a lot of air through the port.

Do you have any way of filtering out the very low frequences that might be causing these issues?

On the other hand it might simple be your speakers giving their opinion on Bjork's music.... :silenced:
 

gramps23

New member
Mar 7, 2011
3
0
0
drummerman said:
Mmmh, something I haven't noticed much before, even at high volume;

Listening to Bjorks Telegram CD, last track 'Headphones Remix', the deep bass makes both my Ushers and Mission's ports distort like crazy (reasonably high volume).

I have plently of bass heavy music, a lot of double bass on my jazz stuff and some electronica but never noticed it to that extend.

Its not so much mid/bass driver doubling (normal for smaller drivers when over driven) but the actual ports farting/distorting like mad ... Amplifier independent too, both with the higher power Sony and cyrus.

regards
Port distortion, or 'chuffing', is caused by too much air being pushed through, which happens at the bottom of the speakers operating range, when the port is active and the wick turned up.

It might well be that the notes you're hitting with the Bjork track are bang on where the resonant frequency of the ports are, and that's the problem.

I've seen Ushers which use relatively long travel bass-mid drivers in small cabinets (718's etc). Small cabinets mean that there are constraints on the apperture of the port, as the bigger the aperture of the port, the longer it must be to tune it to the same frequency, and you simply can't fit a massive port in a small box. So, with a small loudspeaker, that's aiming for decent bass extension and the capacity to go fairly loud with a long travel driver, you might well encounter problems with port distortion.

If you have larger speakers with the same problems, then it's very unfortunate, and possibly something that you might want to speak to the manufacturers about, as it's a design fault which should have been ironed out before the model was released (really, with smaller models this should also be the case, but it's not so uncommon).

Hope that helps, and that my ramblings are intelligable!
 

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