baffle Step - Page 2

rgrayton · 2nd December 2004, 12:16 PM

I am not sure why you do not think a driver is not a considered minimum phase system (at least in the bandpass). From my understanding of a minimum phase system, the phase can be completely defined by the frequency response (excess phase due to time of flight from the UUT to the driver would need to be removed). If it were not essentially a minimum phase system, most of the available measurement and modeling software for this sport would be worthless and our systems would really suck as they rely heavily on a Hilbert Bode Transform, valid on minimum phase systems only.
BG

jdybnis · 2nd December 2004, 06:47 PM

Quote:

I am not sure why you do not think a driver is not a considered minimum phase system

Read my post. Is my reasoning sound?

Quote:

If it were not essentially a minimum phase system, most of the available measurement and modeling software for this sport would be worthless

How much error is consequential? It's not an all or nothing situation.

tiroth · 2nd December 2004, 07:13 PM

Quote:

Originally posted by Pan
A simple BSC made by a resistor and inductor in paralell with eachother and then in series with the driver will only "step in" after some time has elapsed from the beginning of the impulse. The delay of the energy in the inductor is set to match the point of BSC, so the problem you are afraid of does not exist.

If what you say was true, then an equalizer could be used to correct all response anomalies caused by the room. Since these reflections cannot be corrected with a standard equalizer, they are manifestly not minimum phase.

GR. Koonce for one wrote in "Speaker Builder" 6/98 & 8/98 that diffraction is not minimum phase.

The strong implication would be that true BSC (phase as well as FR) would require FIR filters.

tiroth · 2nd December 2004, 07:20 PM

http://www.soundfirst.com/EQ_Phase.html

Quote:

When it comes to acoustic effects, these are much less likely to be significantly minimum phase since they often are due to the combination of multiple signals with delays due to the time it takes for sound to travel through air.

Quote:

Now this is not to say that if you use an EQ to smooth out the response you measure with an RTA out in the room this will result in a smooth phase response as well. There are some things that just can't be fixed with an EQ. In particular, acoustic cancellations of portions of the amplitude response can't be equalized because the response is due to two or more signals arriving with different acoustic delays.

Why would we expect BSD reflections to be any different? Good insight MarkMck!

Pan · 2nd December 2004, 08:13 PM

There are no reflections below the baffle step.

You don´t experience reflection just becasue there is diffraction around the cabinet.

Room standing waves and delayed signals are not the same thing as bafflestep.

At least this is the way I see it

edit: but when I think about it I do believe I realize what you are after... and I remember I did think in those lines also some time ago... hmm.. food for thought.

/Peter

Pan · 2nd December 2004, 08:34 PM

First, I think it´s a mistake to believe that an internal bounce/reflection and room reflection is the same thing as baffle diffraction.

Also the high frequencies will not be affected... there is no reactive element involved in the high range since that is governed by the resistor so to speak.

What I can imagine would affect the total phase response is the low range where much of the signal (most) go thru the inductor which must have a delay involved.

IOW a speaker flush mounted in a wall, or mounted in a slim box could be different in that the box would have ever so slightly higher GD due to the extra inductance.

Thoughts?

/Peter

rgrayton · 2nd December 2004, 09:03 PM

Quote:

How much error is consequential? It's not an all or nothing situation.

Obviously there must not be enough error to be consequential, maintaining my original point -- drivers are regarded by most to be minimum phase devices.
Regards,
RG

russbryant · 3rd December 2004, 04:45 AM

Hey RG what are you doing on this board?

Where did this thread originate? Seems like it started in the middle of the conversation.

Russ

jdybnis · 3rd December 2004, 01:32 PM

Since that error is proportional to the amount of harmonic distortion in the driver we just might not be accounting for it. We already assume it's going to sound bad if a loudspeaker generates a large amount of harmonic distortion. So I wouldn't be suprised if we ignored the secondary effects of distortion throwing off computer simulations and models. I'm always wary of arguments that rely on assuming the status quo is optimal. Just because everybody does it some way doesn't mean it's right.

rgrayton · 3rd December 2004, 05:06 PM

I am not sure what "right" means with regard to this subject. I would say that the present DIY models and modeling software do present an optimal solution and tool for most of us. This has been stated by many others, most likely much brighter and certainly more experienced and educated in the subject than me.
Regards,
RG

Russ, This started out as a question to Mark McKenzie, but he seems to have abandoned the discussion.

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2nd December 2004, 12:16 PM	#11
rgrayton diyAudio Member Join Date: May 2003 Location: MA	I am not sure why you do not think a driver is not a considered minimum phase system (at least in the bandpass). From my understanding of a minimum phase system, the phase can be completely defined by the frequency response (excess phase due to time of flight from the UUT to the driver would need to be removed). If it were not essentially a minimum phase system, most of the available measurement and modeling software for this sport would be worthless and our systems would really suck as they rely heavily on a Hilbert Bode Transform, valid on minimum phase systems only. BG

2nd December 2004, 08:13 PM	#15
Pan diyAudio Member Join Date: Sep 2002	There are no reflections below the baffle step. You don´t experience reflection just becasue there is diffraction around the cabinet. Room standing waves and delayed signals are not the same thing as bafflestep. At least this is the way I see it edit: but when I think about it I do believe I realize what you are after... and I remember I did think in those lines also some time ago... hmm.. food for thought. /Peter

2nd December 2004, 08:34 PM	#16
Pan diyAudio Member Join Date: Sep 2002	First, I think it´s a mistake to believe that an internal bounce/reflection and room reflection is the same thing as baffle diffraction. Also the high frequencies will not be affected... there is no reactive element involved in the high range since that is governed by the resistor so to speak. What I can imagine would affect the total phase response is the low range where much of the signal (most) go thru the inductor which must have a delay involved. IOW a speaker flush mounted in a wall, or mounted in a slim box could be different in that the box would have ever so slightly higher GD due to the extra inductance. Thoughts? /Peter

3rd December 2004, 04:45 AM	#18
russbryant diyAudio Member Join Date: Oct 2002 Location: Tucson, AZ	Hey RG what are you doing on this board? Where did this thread originate? Seems like it started in the middle of the conversation. Russ

3rd December 2004, 01:32 PM	#19
jdybnis diyAudio Member Join Date: Jul 2004 Location: Pasadena, CA	Since that error is proportional to the amount of harmonic distortion in the driver we just might not be accounting for it. We already assume it's going to sound bad if a loudspeaker generates a large amount of harmonic distortion. So I wouldn't be suprised if we ignored the secondary effects of distortion throwing off computer simulations and models. I'm always wary of arguments that rely on assuming the status quo is optimal. Just because everybody does it some way doesn't mean it's right.

3rd December 2004, 05:06 PM	#20
rgrayton diyAudio Member Join Date: May 2003 Location: MA	I am not sure what "right" means with regard to this subject. I would say that the present DIY models and modeling software do present an optimal solution and tool for most of us. This has been stated by many others, most likely much brighter and certainly more experienced and educated in the subject than me. Regards, RG Russ, This started out as a question to Mark McKenzie, but he seems to have abandoned the discussion.