TS parameters and added series coil

jamikl · 2nd June 2011, 07:18 AM

I have asked this on another thread but no response. Panomaniac and a few others have suggested that sometimes a series coil should be added to the woofers on an open baffle, presumably to cut the high end a bit. Does doing this alter the TS parameters in anyway or is it only the resistance of the coil which makes a slight difference to Qes?
jamikl

AllenB · 2nd June 2011, 10:07 AM

They both have an effect but the resistance is normally the only one worth worrying about, and you may even be able to ignore that.

flg · 2nd June 2011, 11:11 AM

Of coarse you are refering to Inductive Reactance? But, there is also resistance(DCR). And they both play a role in the voltage/frequency across the driver.

speaker dave · 2nd June 2011, 11:36 AM

Quote:

Originally Posted by jamikl

I have asked this on another thread but no response. Panomaniac and a few others have suggested that sometimes a series coil should be added to the woofers on an open baffle, presumably to cut the high end a bit. Does doing this alter the TS parameters in anyway or is it only the resistance of the coil which makes a slight difference to Qes?
jamikl

Thiele Small parameters are an idealized look at the woofer bottom corner response and as such don't capture the effect of woofer impedance beyond DCR. (As you say, impacting Qes) External crossover components should be considered as a secondary response shaping block preceeding the T/S defined woofer/cabinet response system. It is complex in the end, because high inductance can shift electrical resonance somewhat.

T/S predictions really work best for systems in 2 pi (half space) with minimal network or inductance.

David S.

jamikl · 2nd June 2011, 11:57 AM

Thanks to AllenB, flg and speaker dave.
jamikl

woody · 2nd June 2011, 01:27 PM

Here is a calculator to find the effect on qts with an added resistance.

http://www.mh-audio.nl/newqts.asp

rabbitz · 3rd June 2011, 05:42 AM

Generally keep the DCR of the inductor to < 10% of the driver's Re for a small as possible change in driver Q (Theile JAES 1976).

There is another figure of < 5% of the driver load impedance (incl impedance comp circuit) at the xo frequency.

2nd June 2011, 07:18 AM	#1
jamikl diyAudio Member Join Date: May 2005 Location: Melbourne	TS parameters and added series coil I have asked this on another thread but no response. Panomaniac and a few others have suggested that sometimes a series coil should be added to the woofers on an open baffle, presumably to cut the high end a bit. Does doing this alter the TS parameters in anyway or is it only the resistance of the coil which makes a slight difference to Qes? jamikl

2nd June 2011, 11:11 AM	#3
flg diyAudio Member Join Date: Jul 2005 Location: North East	Of coarse you are refering to Inductive Reactance? But, there is also resistance(DCR). And they both play a role in the voltage/frequency across the driver. __________________ “Be who you are and say what you feel because those who mind don't matter and those who matter don't mind.” Dr. Seuss

3rd June 2011, 05:42 AM	#7
rabbitz diyAudio Member Join Date: Jul 2003 Location: Newcastle, Australia	Generally keep the DCR of the inductor to < 10% of the driver's Re for a small as possible change in driver Q (Theile JAES 1976). There is another figure of < 5% of the driver load impedance (incl impedance comp circuit) at the xo frequency. __________________ No longer DIY active

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2nd June 2011, 10:07 AM	#2
AllenB diyAudio Member Join Date: Oct 2008	They both have an effect but the resistance is normally the only one worth worrying about, and you may even be able to ignore that.

2nd June 2011, 11:57 AM	#5
jamikl diyAudio Member Join Date: May 2005 Location: Melbourne	Thanks to AllenB, flg and speaker dave. jamikl

2nd June 2011, 01:27 PM	#6
woody diyAudio Member Join Date: Jan 2002 Location: Tyrone Ga. U.S.A.	Here is a calculator to find the effect on qts with an added resistance. http://www.mh-audio.nl/newqts.asp

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