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Where on winisd do i check for xmax?


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#1 of 23 Anthony*gw

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Posted November 20 2003 - 05:05 AM

Greetings all, I am using winisd pro and have designed a 140L enclosure for a shiva driver tuned to 20hz,(box is already completed,just waiting for driver). I think i understand alot about the software,but how do i check to see if a driver is close to xmax in a certain alignment(140L,shiva)?
It will be powered by a 2ch stereo amp 200wpc and 300wpc 4ohm load.i will be wiring the driver in parallel so it will be 300w going to the driver.could someone explain how much power it will take to pass the xmax on the shiva driver in this size box(140L)and at what frequencies?
Nuff respect to all d massive

#2 of 23 Pete Mazz

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Posted November 20 2003 - 05:32 AM

Cone excursion. WinIsd uses point to point, so if your driver has a 1 way Xmax of 15mm, look for where the excursion graph shows 30mm.

Pete

#3 of 23 Anthony*gw

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Posted November 20 2003 - 05:47 AM

Thanks pete,
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#4 of 23 RichardHOS

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Posted November 20 2003 - 05:51 AM

I'm just using the standard version, and I haven't played around with WinISD as much as LspCAD, but I've never seen the plot for cone excursion.

??

#5 of 23 Anthony*gw

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Posted November 20 2003 - 05:59 AM

Quote:
I'm just using the standard version, and I haven't played around with WinISD as much as LspCAD, but I've never seen the plot for cone excursion.


its in the pro version
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#6 of 23 Anthony*gw

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Posted November 20 2003 - 06:25 AM

I played with winisdpro and check the cone excursion for my enclosure and got 2.043mm at 30hz,thats the highest peak between 20hz-50hz and 2.043mm at 17hz.it just keeps getting higher when you go below 17hz.so i am basically getting the same reading at 17hz and 30hz.what do these numbers say? at 17hz and 30hz my shiva will most likely bottom out at high volumes?Posted Image
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#7 of 23 Pete Mazz

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Posted November 20 2003 - 09:09 AM

Looks like the Cone Excursion shows one way Xmax now.

Click on the signal tab and under System Input Power, enter, in your case 300W. The CE graph should now show overexcursion at just above and below tuning. Entering 225W into Input Power would run it to full excursion....theoretically.

Pete

#8 of 23 michael-e

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Posted November 20 2003 - 02:24 PM

Dont forget,you dont HAVE to use every mm of excursion as every mm you go,will be more distortion.

Also the suspension will be less linear moving further.

thats if your looking for low distortion..for HT its not so critical

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#9 of 23 Brian Tatnall

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Posted November 20 2003 - 02:30 PM

Quote:
Dont forget,you dont HAVE to use every mm of excursion as every mm you go,will be more distortion.


Not when they are looking at Xmax which is LINEAR movement.
By definition it is inaudible distortion.
Which includes the lesser of Xsus (suspension distortion) and Xmag.

#10 of 23 michael-e

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Posted November 20 2003 - 05:58 PM

Hold up
Woofers seem to distort differently even with similar xmaxes''

Xmax is the smaller of Xmag and Xsus,
and that is where its 70% of BL or
70% of suspension linearity

that speaks NOTHING directly, of what the speaker distortion output is!

look at mfk-projects.com
the woofers are all at the same conditions,and distort differently yet no where near xmax(i think)

Non linear suspension will be worrying below Fs(eg below Fcb in sealed boxes)

i would love to test similar speakers like that,id make sure the output DbA was constant rather than constant Vin ...

i may not be right but its just my opinion...
Cheers!Posted Image


#11 of 23 Anthony*gw

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Posted November 20 2003 - 11:35 PM

Hey thanks for all the input guys greatly appreciated
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#12 of 23 Anthony*gw

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Posted November 20 2003 - 11:53 PM

Quote:
Click on the signal tab and under System Input Power, enter, in your case 300W. The CE graph should now show overexcursion at just above and below tuning. Entering 225W into Input Power would run it to full excursion....theoretically.


I was just about to try it but i couldn't see the signal tab ??
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#13 of 23 Anthony*gw

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Posted November 21 2003 - 01:35 AM

Quote:
I was just about to try it but i couldn't see the signal tab ??


I have the alpha version,could this be the reason i am not seeing that signal tab?
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#14 of 23 Anthony*gw

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Posted November 21 2003 - 02:07 AM

My bad,i saw it.forget what i said abovePosted Image
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#15 of 23 Anthony*gw

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Posted November 21 2003 - 04:06 AM

back with some numbers:

at 30hz,winisdpro gives me a reading of 35mm which is the highest point on the graph between 20hz-50hz,30hz being the peak .and i am getting the same reading at 17hz(35mm)after 17hz it just keeps going higher and higher,no worry though, for i am not really interested in frequencies under 17hz.keep in mind that i built a 140L 80/20(HT/music)tuned to 20hz using one 4" flared port,will be using the shiva and throwing 300watts at it.
tell me if i got this right.at the frequencies 30hz and 17hz the driver will be passing it's xmax and with enough power i can bottom out my driver? should i worry if my driver reaches 35mm
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#16 of 23 Brian Tatnall

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Posted November 21 2003 - 07:33 AM

Quote:
Hold up. Woofers seem to distort differently even with similar xmaxes''Xmax is the smaller of Xmag and Xsus,
and that is where its 70% of BL or 70% of suspension linearity. That speaks NOTHING directly, of what the speaker distortion output is! Look at mfk-projects.com
the woofers are all at the same conditions,and distort differently yet no where near xmax(i think)
i may not be right but its just my opinion...
Cheers!

Point 1:
I think that Xmax speaks VOLUMES directly about speaker distortion. BL drops or Xmag and you get distortion Kms drops or Xsus and you get more distortion. You defined Xmax maybe you don't understand how it translate into distortion. If Xmax doesn't tell you about distortion there is a SERIOUS problem.

I'm not denying that speakers have different amounts of even kinds of distortion within Xmax. I think they do. Much of it depends on whether or not BL is maintained. Inductance and suspension. Then you have cone material and a host of other things.

If BL drops to 75% right away and somehow maintains itself for awhile then the speaker is going to have more distortion because it will be creating square like waves instead of sine waves. Compare it to a motor that keeps 98% of its BL and your going to have a different amount of distortion.

This is an example of multiple motor typologies showing the different amounts of distortion within Xmax.
http://www.adireaudi...L2TechPaper.pdf

Point 2:
Most research shows that you need at least 3% distortion for it to be audible. These tests are done in the human vocal range where are ears are most sensitive. For detectable distortion levels below 80hz I've heard ranges from 6% to 10% but never below 5%.
http://www.silcom.co....htm#Distortion

The more important question is "Does this actually effect what I'm hearing." After all we are listeners and not machines. If we can't detect it what does it matter.

I've heard the distortion differences above 70hz concerning BL changes before reaching Xmax, but I am still hesitent to say it is as effective below 70hz. Especially two tones below 80hz.
http://acoustic-visi....?showtopic=984


Point 3:
Quote:
thats if your looking for low distortion..for HT its not so critical


This is where I didn't agree with you because you say we can be critical about distortion within Xmax concerning subwoofers. It seems that you implied we could detect the nonlinearities or distortion. I still am very skeptical concerning this. That's my opinion. Our ears become less and less accurate as the frequency goes lower and it becomes nonlinear.

I'd appreciate it some else who has more knowledge about the human ear and distortion could comment.

#17 of 23 michael-e

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Posted November 21 2003 - 07:04 PM

point 1
if xmax directly was related to THD,then why is it defined by % of BL or kms not THD @ mm excursion...

Does 70% BL on one woofer, and 70% BL on another,have equal THD at that point/??

point 2

www.linkwitzlab.com
'thor' subwoofer
see his measurements on the subwoofer he made and distortion requirements

I think that THD <5% is important even in the bass region.If one can attain a more true-er signal with not much hassle,why not!

point 3

oh,sorry when i said 'HT' i meant explosion effects,rumbles etc,rather than music.


The reason i dont want high distortion, is if the 2nd and 3hd harmonics are equal in sound perception as the fundamental 20hz for example, WHAT exactly are we listening to?
No wonder people try 20hz sine and think they can hear it..


#18 of 23 Brian Tatnall

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Posted November 21 2003 - 07:59 PM

Point 1
Quote:
Does 70% BL on one woofer, and 70% BL on another,have equal THD at that point/??


The adire link. It addresses that issue directly. I'll quote myself concerning that problem also. "an example of multiple motor typologies showing the different amounts of distortion within Xmax."

BL at 70% is NOT the same between different woofers. Because BL at rest is different. Agreed. Speakers have different motor strength, I thought that was obvious. Different frequencies require different amounts of air displacement and therefore different amounts of motor strength.

However, it is wrong to say that Xmag speaks NOTHING directly concerning distortion. Losing BL = introducing distortion. A speaker is no longer able to produce a wave accurately since the motor strength can not get it to where it needs to be. Thus creating an inaccurate wave. Which is distortion.


Quote:
if xmax directly was related to THD,then why is it defined by % of BL or kms not THD @ mm excursion...


When you lose Kms and BL you get distortion. Xmax is defined by losing Kms and Bl. It's that simple.

Xmax isn't considered linear movement for kicks.

Xmax is defined by % because not all drivers need the same amount of BL or Kms like a tweeter vs a sub or vs a midrange. Mentioned before.


Point 2
Quote:
I think that THD <5% is important even in the bass region.If one can attain a more true-er signal with not much hassle,why not!


Who cares if you can't hear it! Think about it...Your ear is not capable of detecting distortion well that low. You are not a machine. Even if the measurements show distortion it doesn't matter if you can't hear it.

You need to determine how well you are able to hear at that level before determining its importance.

Example. Do I care if my tweeter is flat from 100khz-300khz? No because eventhough a machine shows its flat. I can't hear it. Although my dog might like my new speakers better.

Concerning Linkwitz Lab. Notice what they have to say, "Non-linear distortion limits the maximally useable output of any subwoofer. The non-linear behavior of a subwoofer increases rapidly as cone excursions become large, because force factor Bl, compliance Cms, and voice coil inductance Le, change with displacement from the resting position."

Non-linear distortion/behavio - that which is outside Xmax since it becomes unusable or audible as BL and Cms change/lower. Even Linkwitz uses Xmax all throughout the development of the Thor to determine AUDIBLE distoriton.

Point 3
Quote:
oh,sorry when i said 'HT' i meant explosion effects,rumbles etc,rather than music.


Does the speaker all of a sudden distort differently because your playing explosions instead of music? If the distortion is inaudible concerning both? HT and music do have different expectations, but can the results be any different if it all is inaudbile anyway?

Quote:
The reason i dont want high distortion, is if the 2nd and 3hd harmonics are equal in sound perception as the fundamental 20hz for example, WHAT exactly are we listening to?


Then we are listening to both the 2nd and 3rd harmonic frequency as well as the 20hz fundamental. Posted Image

I assume your talking about this. "The importance of low distortion at very low frequencies can be deduced from the equal loudness contours. The threshold of hearing is around 70 dB SPL at 20 Hz. This is at the level of normal conversation. With increasing frequency the threshold drops rapidly. The loudness contours have an initial slope of 80 dB/dec, or 24 dB/oct, at low perceived volume levels (phon).This means that if the 40 Hz 2nd harmonic of a 20 Hz tone is at a 24 dB lower level, then it will sound equally as loud as the fundamental. This corresponds to 6% 2nd harmonic distortion. The 3rd harmonic distortion would have to be below 1%, or over 38 dB down, in order that it is less loud than the 20 Hz fundamental. It all leads to very low distortion requirements. The fundamental frequency sound pressure level needs to be above 70 dB to even become audible and it should not be masked by higher frequency distortion products. "

Notice this is theory. Good theory, but think about it in an acutual application.

So I model a shiva up and put 16watts into it in a .707 Q box using Adire's version of Lspcad. Sounds pretty fair to me very little power with a staple box alignment. 20hz = 93db @ 13mm p-p. That's 93db not 70db using only 13mm of the 31.6mm available. 70 is just the threshold of hearing and many subs can do that easily. You start cranking the shiva like above in the 93db range and your perception of the 20hz is going to dominate any 2nd or 3rd harmonic.

#19 of 23 michael-e

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Posted November 21 2003 - 10:12 PM

lol,i realised we are discussing this in this guys thread,when it doesnt really concern him,so will pursue this discussion with PMs rather than thread-hog.

Cheers Brian


#20 of 23 Brian Tatnall

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Posted November 22 2003 - 03:43 AM

Excellent idea Michael. YGPM.


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