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Discussion Starter #1
So, I had read the article from Adire Audio on resistively damped operation (shorting a unused coil of a DVC sub) and planned to use it on a DVC 12" sub with a Qts of .44 in a IB install. But, I noticed the article says that it doubles Qes, which in turn sends the woofer out of control when modeling it in WinISD. Doubling Qes sends excursion through the roof, far beyond the limits of the driver and I can't avoid overexcursion without using A LOT less power or A LOT higher crossover, is this really true to what would happen in the real situation? Should I worry? Should I try it anyway?

Thanks,
Travis
 

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I have not read it, but you will have half the power handling using one VC. A given sub generally can only use half its box power rating when used IB (unless it has a specific IB rating). So you might be at 1/4 its original rating give or take.

With IB if you want to tune it you generally want a low Fs (or expect it to play down near Fs and then roll off) and you want a higher qts, which contains qes. The higher qts boosts output down by Fs, it will end up more flat when run IB where you don't have the box to push Q up.

You don't have to tune a sub IB, it can sound like crap and you just EQ it and feed it more power long as the sub is capable of handling that. And you might already know this.

Make sure its not how you put the stuff in winISD, I never put qts in unless I do not have the other two. It will make qts on its own.

Note that a higher qts means the speaker is less damped at Fs, it wants to move there easier, somewhat like a bell rings at X frequency. The compression of a box makes the cone less compliant and thus it raises resonance to higher frequency (higher Q, or Qtc). A less damped high qts sub is more sensitive to enclosure volume and that shows up as a huge Vas. Low qts subs are more dampened and don't care about the box near as much that is why they can handle small boxes. That makes them inefficient, but large amps are cheap.
 

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Discussion Starter #3
Adire says to "de-rate" the power handling by 25%, not 50%. Half seems logical but it is true that the shorted coil absorbs some power and dampens the woofer.

I'm not so sure I have my model correct after review the article again today, I've got to run through the math again.

The problem is the sub I intended to do this with supposedly only has 5mm of xmax, that's bad - so my power handling is terribly limited anyway, but I still thought it might be doable. I need to get a strong model before I determine if I say nay or yay.
 

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not sure I would run a sub with 5mm of xmax IB. ported is about all I would consider.
 

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Ms is mass. If you want to try IB you can get the pyle 15s I run for under 50 shipped. I dunno how the 12 works the Fs is higher as usual, or run a 15 into a 12 hole if you can fit.
http://www.the12volt.com/caraudio/thiele.asp
 

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Adire says to "de-rate" the power handling by 25%, not 50%.
As a rule of thumb this one is pretty good. You still have the extra thermal mass provided by the other coil windings. I agree with the other posters about not using a sub with a RATED 5mm xmax in an IB configuration. If it is rated at 5mm what are the real characteristics? Typically less than the rating. IMO look at something with more throw and just EQ the curve to get what you want (keep in mind you are going the get some cabin gain as well - EQ may not even be required).
 
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