Impedance Question

jwatts · 1st June 2006, 01:19 PM

Can I estimate the frequency response of a loudspeaker by using a plot of its impedance?

soongsc · 1st June 2006, 03:07 PM

No.

Cal Weldon · 1st June 2006, 03:36 PM

The high end will be tough to guage but if you have the impedance graph, you can tell the resonant frequency and have a good idea how low it can go as not too many drivers are much good below it.

jwatts · 1st June 2006, 05:11 PM

What is the best way to determine it? Can I calculate somehow from the woofers Thielle Small parameters?

Cal Weldon · 1st June 2006, 07:54 PM

Why don't you post what you know about the driver and we'll see what we can do.

jwatts · 1st June 2006, 11:01 PM

I was asked to find the Thielle Small parameters and properties of a subwoofer for a friend of mine. All I need is the frequency response. The parameters I have found so far are listed below. I can set up and do a near field frequency response measurement but if I could just calc it somehow it would make my life easier.

Fs(Hz) = 33.79
Qms = 5.2537
Qes=.4616
Qts=.4883
Vas(ft^3)=.83
Bl(N/A)=7.82
Efficiency(%)=.09
Rvc(Ohms)=1.79
Le(uH)=652.19
Xmax(In) Peak to Peak = 1.17
Sensitivity 85 db@1w/1m
SdIn^2) = 51.84
Vd(ft^3) = .035
Inverted Cone Volume(ft^3) = .047
Magnet and Cone Volume(ft^3) = .092
Mounting hole ID 9-1/4(In)
Mounting depth 8 inches (In)
Continuous power 500 watts RMS
80 oz double stacked magnets

ocool_15 · 2nd June 2006, 12:05 AM

your frequency response of a sub(any speaker) will be dependent on the enclosure. You can get an idea of its response <~300hz from the T/s parameters but measuring a speaker with a mic will be most accurate when done properly.

jwatts · 2nd June 2006, 12:08 AM

How about the low end? What is the lowest possible frequency this sub can produce? Can I get that from these parameters or impedance curve.

ocool_15 · 2nd June 2006, 12:14 AM

fs is an indication. get WinISD(free!) and check how it performs, you will have cabin gain to add to the low end. This looks like a car sub that is not optimized for sealed or ported specifically.

F3 is when output power has dropped down to half and it used most often

soongsc · 2nd June 2006, 12:25 AM

There are three basic things that limit the low end Fo, driver area(size), and Xmax. The LinkWitz Lab site has a maximum SPL calculatorwhich is convenient.

1st June 2006, 01:19 PM	#1
jwatts diyAudio Member Join Date: Jan 2004 Location: Erwin, Tennessee	Impedance Question Can I estimate the frequency response of a loudspeaker by using a plot of its impedance?

1st June 2006, 03:07 PM	#2
soongsc diyAudio Member Join Date: Mar 2005 Location: Taiwan	No. __________________ Hear the real thing!

1st June 2006, 03:36 PM	#3
Cal Weldon Speakerholic diyAudio Moderator Join Date: Jan 2004 Location: British Columbia	The high end will be tough to guage but if you have the impedance graph, you can tell the resonant frequency and have a good idea how low it can go as not too many drivers are much good below it. __________________ Next stop: Margaritaville Some of Cal's stuff \| Cal Weldon Consulting

1st June 2006, 05:11 PM	#4
jwatts diyAudio Member Join Date: Jan 2004 Location: Erwin, Tennessee	Measurements What is the best way to determine it? Can I calculate somehow from the woofers Thielle Small parameters?

1st June 2006, 07:54 PM	#5
Cal Weldon Speakerholic diyAudio Moderator Join Date: Jan 2004 Location: British Columbia	Why don't you post what you know about the driver and we'll see what we can do. __________________ Next stop: Margaritaville Some of Cal's stuff \| Cal Weldon Consulting


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1st June 2006, 11:01 PM	#6
jwatts diyAudio Member Join Date: Jan 2004 Location: Erwin, Tennessee	10 Inch Sub I was asked to find the Thielle Small parameters and properties of a subwoofer for a friend of mine. All I need is the frequency response. The parameters I have found so far are listed below. I can set up and do a near field frequency response measurement but if I could just calc it somehow it would make my life easier. Fs(Hz) = 33.79 Qms = 5.2537 Qes=.4616 Qts=.4883 Vas(ft^3)=.83 Bl(N/A)=7.82 Efficiency(%)=.09 Rvc(Ohms)=1.79 Le(uH)=652.19 Xmax(In) Peak to Peak = 1.17 Sensitivity 85 db@1w/1m SdIn^2) = 51.84 Vd(ft^3) = .035 Inverted Cone Volume(ft^3) = .047 Magnet and Cone Volume(ft^3) = .092 Mounting hole ID 9-1/4(In) Mounting depth 8 inches (In) Continuous power 500 watts RMS 80 oz double stacked magnets

2nd June 2006, 12:05 AM	#7
ocool_15 diyAudio Member Join Date: Nov 2004 Location: sk	your frequency response of a sub(any speaker) will be dependent on the enclosure. You can get an idea of its response <~300hz from the T/s parameters but measuring a speaker with a mic will be most accurate when done properly.

2nd June 2006, 12:08 AM	#8
jwatts diyAudio Member Join Date: Jan 2004 Location: Erwin, Tennessee	Low End How about the low end? What is the lowest possible frequency this sub can produce? Can I get that from these parameters or impedance curve.

2nd June 2006, 12:14 AM	#9
ocool_15 diyAudio Member Join Date: Nov 2004 Location: sk	fs is an indication. get WinISD(free!) and check how it performs, you will have cabin gain to add to the low end. This looks like a car sub that is not optimized for sealed or ported specifically. F3 is when output power has dropped down to half and it used most often

2nd June 2006, 12:25 AM	#10
soongsc diyAudio Member Join Date: Mar 2005 Location: Taiwan	There are three basic things that limit the low end Fo, driver area(size), and Xmax. The LinkWitz Lab site has a maximum SPL calculatorwhich is convenient. __________________ Hear the real thing!

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