Zobel effect on LF

Sony · 22nd August 2005, 11:23 AM

The impedance of my 8ohm woofers has these aproximate values:

30Hz: 24 ohm
35Hz: 30 ohm
40Hz: 26 ohm
50Hz: 18 ohm
60Hz: 12 ohm
100Hz: 8 ohm

If I use a Zobel (RC) in the woofer 2nd order passive fileter I can make this rise in the impedance almost disappear.

What results (win-lose) can I expect in the bass from doing so?

4real · 22nd August 2005, 11:28 AM

I thing that as long as you don't X-over in that region, that it will not make a difference.

richie00boy · 22nd August 2005, 12:13 PM

You should have measured above 100Hz. The zobel will counteract the rise in impedance due to voice coil inductance, and occurs higher up the band than the impedance peak due to box interaction -- which you have measured there.

As said, it won't change much unless your crossover is around that region. If you have a fussy amp it might make it a bit easier to drive due to it compensating the lagging current.

Sony · 22nd August 2005, 12:32 PM

Between 100Hz and xo point (750Hz) the impedance is stable at 8 ohm.

The bass amplifier is a 3-stage class A amplifier with lots of current that handles well low impedances such as 2 ohm (Pass Aleph 0). It doubles the power with half the impedance - at 2 ohms it delivers 4 times

the power at 8 ohm.

Using the Zobel wouldn't have any effect in the woofer curve response around 20-60Hz?

4real · 22nd August 2005, 12:38 PM

Don't think that you will be able to put more power into your woofer. The extra power the amp gives will simple dissipate as heat in the zobel

Sony · 22nd August 2005, 12:48 PM

That's what I've suspected. No point in using it then, since the impedance near the xo point is the expected one.

Thanks for the help!

22nd August 2005, 11:23 AM	#1
Sony diyAudio Member Join Date: Sep 2004 Location: Portugal	Zobel effect on LF The impedance of my 8ohm woofers has these aproximate values: 30Hz: 24 ohm 35Hz: 30 ohm 40Hz: 26 ohm 50Hz: 18 ohm 60Hz: 12 ohm 100Hz: 8 ohm If I use a Zobel (RC) in the woofer 2nd order passive fileter I can make this rise in the impedance almost disappear. What results (win-lose) can I expect in the bass from doing so?

22nd August 2005, 12:13 PM	#3
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	You should have measured above 100Hz. The zobel will counteract the rise in impedance due to voice coil inductance, and occurs higher up the band than the impedance peak due to box interaction -- which you have measured there. As said, it won't change much unless your crossover is around that region. If you have a fussy amp it might make it a bit easier to drive due to it compensating the lagging current. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

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22nd August 2005, 11:28 AM	#2
4real diyAudio Member Join Date: May 2004 Location: Arnhem	I thing that as long as you don't X-over in that region, that it will not make a difference.

22nd August 2005, 12:32 PM	#4
Sony diyAudio Member Join Date: Sep 2004 Location: Portugal	Between 100Hz and xo point (750Hz) the impedance is stable at 8 ohm. The bass amplifier is a 3-stage class A amplifier with lots of current that handles well low impedances such as 2 ohm (Pass Aleph 0). It doubles the power with half the impedance - at 2 ohms it delivers 4 times the power at 8 ohm. Using the Zobel wouldn't have any effect in the woofer curve response around 20-60Hz?

22nd August 2005, 12:38 PM	#5
4real diyAudio Member Join Date: May 2004 Location: Arnhem	Don't think that you will be able to put more power into your woofer. The extra power the amp gives will simple dissipate as heat in the zobel

22nd August 2005, 12:48 PM	#6
Sony diyAudio Member Join Date: Sep 2004 Location: Portugal	That's what I've suspected. No point in using it then, since the impedance near the xo point is the expected one. Thanks for the help!

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