Modelling/real life vs driver spec

jimbo1968 · 16th December 2005, 04:58 PM

This may be a very dumb question, but why does the winISD response fall of so very far short of the FR125S published response?

jimbo1968 · 16th December 2005, 05:00 PM

winisd

Vikash · 16th December 2005, 09:46 PM

The low end conditions of the published graphs are unknown. I wouldn't compare low end response with that graph for sure

Best thing to do is measure the nearfield response of your design and then compare to winisd to see if there is any discrepency.

John Sheerin · 16th December 2005, 11:15 PM

The measured response is on an IEC baffle. This is a big baffle with no rear chamber on the driver. The driver will play down to its resonance and then roll off. When you put the driver in a sealed box, you increase the resonance of the system - the air spring of the box makes the entire 'suspension' of the system stiffer than the speaker's suspension alone, so the resonant frequency goes up compared to just the driver.

jimbo1968 · 17th December 2005, 01:38 AM

It's the non-existant top end in the winISD model that's confusing me.

I took some test tone readings with a SPL meter but they were all over the place, and moving my head I could hear really bad destructive interference. I guess this is reflections? I knew my room was bad for echos.

So how should I measure? TrueRTA and pink noise?

John Sheerin · 17th December 2005, 03:16 AM

Quote:

Originally posted by jimbo1968
It's the non-existant top end in the winISD model that's confusing me.

Oh, that's just the rolloff due to the Le you entered that WinISD is showing. It has no other information, like narrowing of the polar pattern and cone breakup caused by cone material properties and cone shape, so it can't predict high frequencies any better than what it does.

Quote:

I took some test tone readings with a SPL meter but they were all over the place, and moving my head I could hear really bad destructive interference. I guess this is reflections? I knew my room was bad for echos.

So how should I measure? TrueRTA and pink noise?

Sine waves do that. You can use warble tones, band limited pink noise, or go to a computer based system. I like Speaker Workshop.

Vikash · 17th December 2005, 10:11 AM

Hi Jim, just to put it in a different way, T/S modelling apps are to model low end response only.

16th December 2005, 09:46 PM	#3
Vikash diyAudio Moderator Emeritus Join Date: May 2003 Location: UK	The low end conditions of the published graphs are unknown. I wouldn't compare low end response with that graph for sure Best thing to do is measure the nearfield response of your design and then compare to winisd to see if there is any discrepency. __________________ "The human mind is so constituted that it colours with its own previous conceptions any new notion that presents itself for acceptance." - J. Wilhelm. (But I still think mine sounds better than yours.)

17th December 2005, 10:11 AM	#7
Vikash diyAudio Moderator Emeritus Join Date: May 2003 Location: UK	Hi Jim, just to put it in a different way, T/S modelling apps are to model low end response only. __________________ "The human mind is so constituted that it colours with its own previous conceptions any new notion that presents itself for acceptance." - J. Wilhelm. (But I still think mine sounds better than yours.)

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16th December 2005, 11:15 PM	#4
John Sheerin diyAudio Member Join Date: Nov 2003 Location: Pittsburgh, PA	The measured response is on an IEC baffle. This is a big baffle with no rear chamber on the driver. The driver will play down to its resonance and then roll off. When you put the driver in a sealed box, you increase the resonance of the system - the air spring of the box makes the entire 'suspension' of the system stiffer than the speaker's suspension alone, so the resonant frequency goes up compared to just the driver.

17th December 2005, 01:38 AM	#5
jimbo1968 diyAudio Member Join Date: Nov 2004 Location: UK, bristol	It's the non-existant top end in the winISD model that's confusing me. I took some test tone readings with a SPL meter but they were all over the place, and moving my head I could hear really bad destructive interference. I guess this is reflections? I knew my room was bad for echos. So how should I measure? TrueRTA and pink noise?

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