impedance plot on vented box?

dallaire · 1st January 2008, 03:44 PM

Hello, I was wondering if the impedance "high points" on a vented enclouser impedance/phase plot had to be or should be the same "height" or "impedance value" on the graph. I did notice my fist test box was a couple HZ off the design tuning frequency and the two high imp. points were not even, then after adjusting the port in length to yield the design tuning frequency, I noticed that the two impeadance peaks are now at the same level on the impedance scale. I was wondering if this means anything like proper allignment or not?
Thanks,
dallaire

Ron E · 1st January 2008, 06:08 PM

No.

Port damping will decrease the lower peak, box damping will decrease the upper peak. Leaks will reduce both and raise the trough between.

Svante · 1st January 2008, 08:48 PM

For a lossless butterworth system they are of equal height. However, real systems can be different, as RonE says:

dallaire · 1st January 2008, 09:21 PM

Thanks guy's, this helps alot! well I guess the final test box I have got tuned now is my target. The WT2 tester has kicked back the design volume and also the correct tunig frequency after triming the length of the port another half inch. I have acousiticly measured the design in the final test box and measures +-3db from 45hz thru 300 then gets flater from there. I will have to compensate for about 3db of baffle step up to about 300hz. for an in room response at the center channel listening position I am happy with the result "floor bouce included". This design is using a Peerless 6.5 inch woofer HDS Nomex driver.
Thanks agian for the input!

dallaire

1st January 2008, 03:44 PM	#1
dallaire diyAudio Member Join Date: Nov 2007	impedance plot on vented box? Hello, I was wondering if the impedance "high points" on a vented enclouser impedance/phase plot had to be or should be the same "height" or "impedance value" on the graph. I did notice my fist test box was a couple HZ off the design tuning frequency and the two high imp. points were not even, then after adjusting the port in length to yield the design tuning frequency, I noticed that the two impeadance peaks are now at the same level on the impedance scale. I was wondering if this means anything like proper allignment or not? Thanks, dallaire

1st January 2008, 06:08 PM	#2
Ron E diyAudio Member Join Date: Jun 2002 Location: USA, MN	No. Port damping will decrease the lower peak, box damping will decrease the upper peak. Leaks will reduce both and raise the trough between. __________________ 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

1st January 2008, 08:48 PM	#3
Svante diyAudio Member Join Date: Feb 2004 Location: Stockholm	For a lossless butterworth system they are of equal height. However, real systems can be different, as RonE says: __________________ Simulate loudspeakers: Basta! Simulate the baffle step: The Edge

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1st January 2008, 09:21 PM	#4
dallaire diyAudio Member Join Date: Nov 2007	Thanks guy's, this helps alot! well I guess the final test box I have got tuned now is my target. The WT2 tester has kicked back the design volume and also the correct tunig frequency after triming the length of the port another half inch. I have acousiticly measured the design in the final test box and measures +-3db from 45hz thru 300 then gets flater from there. I will have to compensate for about 3db of baffle step up to about 300hz. for an in room response at the center channel listening position I am happy with the result "floor bouce included". This design is using a Peerless 6.5 inch woofer HDS Nomex driver. Thanks agian for the input! dallaire

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