Home » Audio » Speaker » Cancellation in car trunk
Cancellation in car trunk [message #14794] Mon, 22 November 2004 05:44 Go to next message
Adrian Mack is currently offline  Adrian Mack
Messages: 568
Registered: May 2009
Illuminati (1st Degree)
General thinking would say that you cant get cancellation at subbass frequencies in the trunk of a car because reflections or multiple subs cant really sum to 180 degrees apart (or between 135deg and 225deg to be destructive).

However some positions do result in what sounds like cancellation, such as having theh subbox face right up towards the front wall of the trunk with the drivers firing into the wall. However it doesnt seem that phase cancellation could be the source for this issue - anyone know what could cause this in the trunk?

Re: Cancellation in car trunk [message #14795 is a reply to message #14794] Mon, 22 November 2004 06:56 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18789
Registered: January 2001
Illuminati (33rd Degree)
Hi Adrian,

If you're using a pair of subs, you might get an oscilloscope and see if the signals sent to the two are phased. I used to enjoy using the left and right channels to generate Lissajou patterns and I was surprised how many recordings had bass with content phased more than 90o between channels. If your signals are already phased 135o then the distances to create a 180o shift are smaller. And in a small space, two sound sources would be tightly coupled and highly combinative.

Wayne

Re: Cancellation in car trunk [message #14796 is a reply to message #14795] Mon, 22 November 2004 07:41 Go to previous messageGo to next message
Adrian Mack is currently offline  Adrian Mack
Messages: 568
Registered: May 2009
Illuminati (1st Degree)
Hi Wayne

That makes sense, good point. Crossover filters etc also add additional phase shift, so I'd guess these would also mean distances to create destructive phase shifts are smaller.

Adrian

Re: Cancellation in car trunk [message #14797 is a reply to message #14796] Mon, 22 November 2004 08:14 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18789
Registered: January 2001
Illuminati (33rd Degree)
Yeah, check all that stuff out. Make some measurements and move things around to see if you can isolate the symptoms to a particular situation. Might model the system with the trunk as a lossy sealed chamber and find something there too. Let us know what you find; Maybe post in the CarAudio forum too for future reference. Might help someone with a similar situation.

Found this page interesting [message #14800 is a reply to message #14794] Tue, 23 November 2004 13:05 Go to previous message
clbeanz is currently offline  clbeanz
Messages: 2
Registered: May 2009
Esquire
Placement certainly changes things in a box in a box.

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