Excursion in WinISD pro vs Xmax & Xmech - diyAudio
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Old 10th July 2013, 05:42 PM   #1
Kev06 is offline Kev06  England
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Default Excursion in WinISD pro vs Xmax & Xmech

When simulating cone excursion in WinISD pro/alpha, I have the graph set to show peak, i.e. the +/- (one-way) value. So its attempting to simulate the peak of driver deviation (not the RMS or total P-P movement).

But that seems to be based on a sinusoidal wave, and WinISD can't know what my music comprises in terms of sudden transients and other pointy bits. In practice, can I more or less trust WinISD's excursion simulations for designing within Xmax, and is it safe to assume that any unusual transients will still be within safe Xmech limits or should I leave a margin for error?

Cheers
kev
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Old 10th July 2013, 05:51 PM   #2
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With Xmax is safe to design, with Xmech is not unless you have exact parameter from vendor/manufacturer, and that's what you should have protection for (EQ/limiter).
You can post your design for double checking by members late in the design process.
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Old 10th July 2013, 08:13 PM   #3
OscarS is offline OscarS  United States
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WinISD is a very basic modeling program. The results it spits out are just as a guide. Just as you said, the excursion is an approximation assuming sinusoidal inputs.

Can you attach the WinISD file?
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Old 10th July 2013, 09:53 PM   #4
Kev06 is offline Kev06  England
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Thanks for the help; very useful.

I'm really just starting out with it and wanted to get a feel for how real-world it is. It sounds like it'll be giving me at least a useful a ball-park though, so I'll continue to fiddle with it and then attach a file when I've got something worth looking at. (I'm trying to use a Linkwitz Transform and have a bit to learn first).

Cheers
kev
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Old 10th July 2013, 10:27 PM   #5
Zero D is offline Zero D  United Kingdom
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Hi, i've designed Many boxes over the years with WinISD, & they ALL turned out as expected. Plus i've never had any complaints about them, in fact just the opposite. And that's from lots of bars n clubs etc, some of them Major players

Here's the latest version http://www.linearteam.org/download/winisd-07x.exe
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Old 10th July 2013, 10:59 PM   #6
Kev06 is offline Kev06  England
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Thanks! looks like I'm using an older version.

There are a few niggles with the version I've been using (not saving filters in projects, and having to run it in compatibility mode for win7, for example) BUT its free and I'm surprised how stable and usable it is for an alpha; it can do much more than the basic version I've used before so I'm pretty happy so far. If I'd tried to manually do even half of what I've done (in seconds) in winISD there would be mistakes all over the place :-)

Cheers
kev
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Old 11th July 2013, 06:53 PM   #7
Kev06 is offline Kev06  England
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Okay I think I understand what I'm doing now. Attached are two pictures for cone excursion and SPL. These are for the SEAS L26ROY which has an Xmax of 14mm, a sensitivity of 87dB and its being fed with 50w system power. Then I've added a Linkwitz Transform with an fp=27hz and a Qp of 0,68.

I've managed to get down to around 30hz at -3db with an SPL of about 104dB@1m before I run beyond the 14mm Xmax. I did have to add a 4th order high pass filter at 16hz to contain the low frequency excursion, but maybe that'll help reduce room resonances.

I realise that this is very modest by subwoofer standards, but I'm thinking of using them as the bass driver in a 3-way rather than a stand-alone sub, so I'm only looking for SPLs that'll match a normal mid-bass range.

Does this seem reasonable?

Cheers
kev
Attached Images
File Type: jpg L26ROY_LT_30hz_50w-excursion.jpg (81.0 KB, 116 views)
File Type: jpg L26ROY_LT_30hz_50w-SPL.jpg (74.2 KB, 113 views)
File Type: jpg L26ROY_LT_30hz_50w-filters.jpg (34.2 KB, 113 views)
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Old 11th July 2013, 07:14 PM   #8
OscarS is offline OscarS  United States
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As long as you're realistic about the "50W system power", there's nothing wrong with that alignment IMO. Personally, I don't see needing 30Hz response if you plan to augment this system with a standalone subwoofer later on. You could probably get away with 35-40Hz F3 and get higher power handling. Just my take on it.
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Old 11th July 2013, 08:03 PM   #9
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Quote:
Originally Posted by Kev06 View Post
Okay I think I understand what I'm doing now. Attached are two pictures for cone excursion and SPL. These are for the SEAS L26ROY which has an Xmax of 14mm, a sensitivity of 87dB and its being fed with 50w system power. Then I've added a Linkwitz Transform with an fp=27hz and a Qp of 0,68.

Does this seem reasonable?

Cheers
kev
Seems most simulation programs show increased excursion linearly with increased power, while the reality is past Xmax there is progressively less motor force and generally more mechanical resistance of the spider and surround "putting the brakes on" excursion.
Conversely, a very "loose" suspension won't have the electric motor braking when driven past Xmax, and given a powerful peak may hammer the voice coil on the top plate.

Much past Xmax, I would not trust excursion vs power predictions.

Last edited by weltersys; 11th July 2013 at 08:09 PM.
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Old 11th July 2013, 08:27 PM   #10
OscarS is offline OscarS  United States
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Quote:
Originally Posted by weltersys View Post
Seems most simulation programs show increased excursion linearly with increased power, while the reality is past Xmax there is progressively less motor force and generally more mechanical resistance of the spider and surround "putting the brakes on" excursion.
Conversely, a very "loose" suspension won't have the electric motor braking when driven past Xmax, and given a powerful peak may hammer the voice coil on the back plate.

Much past Xmax, I would not trust excursion vs power predictions.
Fixed it for ya.
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