How much excursion is too much? - diyAudio
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Old 8th April 2005, 11:28 PM   #1
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Default How much excursion is too much?

I have an 12 cu. ft. box tuned to 19Hz with a 4" x 5" port.
The driver is a 15" Dayton Quatro.

Here's the question:
My driver excursion can get quite high in the 23-25Hz range, how do I know if its too far? Is xMax a strict value to be observed (do i need to worry about damaging the driver) or will it just stop outputting past that point?
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Old 9th April 2005, 12:58 AM   #2
Bricolo is offline Bricolo  France
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When the cone lays on the floor, it's been too much excursion

More seriously: I think that Xmax is the maximum linear range. (linear may mean <10% distortion).
Beyond this point, the sound will distort much more rapidly WRT sound volume. And even beyond, you can permanently damage the driver.

So, stay within Xmax. Even if a little more won't destroy the driver, it won't sound good.
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Old 9th April 2005, 01:33 AM   #3
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An example of when it gets long enough to worry is the Oliphant scene in LotR:RotK. The excursion is def. a bit longer than xMax, but only at the very beginning of each step. Is this okay, since its not for extended periods?
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Old 9th April 2005, 03:08 AM   #4
Bricolo is offline Bricolo  France
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I THINK that there are different states, in rising order: (this is yet to confirm)

-Xmas, it begins to distort heavilly but no damage is done
-maximum long term excursion: distorts like hell, and is the excursion that you can reach for a long time without damage
-maximum short time excursion: a level you can keep for a fex minutes without causing permanent damage
-absolute maximum excursion: if you reach it even for a transient, you make some damage to your driver

But I'm not aware of any manufacturer giving all those specs
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Old 9th April 2005, 03:38 AM   #5
DcibeL is offline DcibeL  Canada
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Back in highschool I wanted to see if the cone would tear of a speaker before it fried the voice coil. The aim was to see if I could launch the cone across the room like on a music video I saw. So a cheap car speaker was hooked to the biggest amp I could find. The voicecoil launched right out of the magnetic gap, and moved a little to one side so that it would not fall back into place. What fun that was.

That is too much excursion
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Old 9th April 2005, 03:50 AM   #6
Mark Kravchenko --- www.kravchenko-audio.com
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Default Check this out

http://linkwitzlab.com/images/graphics/wedge-micro.gif

THis little gizmo when taped to your woofer dust cap will give you a good idea how much your woofer is really woofing.

The explanation is here:

http://linkwitzlab.com/faq.htm#Q4

It's under Q29

One note is that ideally X max is the lenghth of the voice coil minus the thickness of the top plate and then divided by two. What is normally quoted is X-max plus 10% Still not to much distorsion at that excursion. X-mech is the actuall suspension limits. Exceed this and you will have ripped spiders , voicecoil to spider glue line ripped surround and or torn surround adhesive.
Been there done that you can't have my T-shirt though.

Mark
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Old 9th April 2005, 04:08 AM   #7
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But it would be fairly safe to say you guys think i'll be alright exceeding xMax every once in a while in short bursts?
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Old 9th April 2005, 05:28 AM   #8
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I can't see a problem with your situation. If you're approaching the mechanical limits of the suspension you may have a problem though.

The occasional journey outside of the electrical Xmax shouldn't be a problem. Unless you have an Extremis or something like that, Xmech should be considerably larger than Xmax. As was said before, you will have more distortion, but there shouldn't be any physical harm. If you're hurting the driver you will probably be able to hear its distress.

EDIT: I'm not badmouthing the Extremis, I have six of them. They're sweet. I'm merely saying that their Xmax is so large that is is nearly equal to the Xmech which is atypical.
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Old 9th April 2005, 06:05 AM   #9
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Thanks all.

Just finished fixing my gainclones and my system is running very nicely now.

A little tinny in places, but I'll EQ that out.
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Old 9th April 2005, 08:34 AM   #10
mike.e is offline mike.e  New Zealand
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ALot of cheap plate amps have boost at 35hz ,this is useless if your using a ported box with maximally flat alignment!!

Xmech on HT woofers is usually not much more than the Xmax!This means dont go crazy.

Xmax on music/prosound woofers tends to be quite tiny,while the xmech still large with a large area in between where distortion occurs but not in a dangerous fashion.

If it sounds like its distorting,turn it down.
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