Shiva Xmax problem (1 Viewer)

[Andrew T]

Can anyone answer why my Shiva always hits Xmax and goes crack.
Its in a twin ported 240l box and is powered by a 200W amp. Even at reasonable levels its easy to make it get to the end.
Is it possibly because the box volume offers little resistance?
Andrew

 

[Patrick Sun]

What's the tune of the box?
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PatCave; HT Pix; Gear; DIY Mains; DIY CC; Sunosub I + II + III; DVDs; Link Removed

 

[DanWiggins]

Andrew,
In a word: too big. The box size, 240L, is too large for a Shiva with lots of power. In fact, about 160W is all you can take. More than that, and you bottom the driver. This is because the cabinet is very big, the system is efficient, which means you need little power to get big SPL.
If you want more power handling, you'll need to have a smaller box. OF course, then you lose some efficiency, so it's all a tradeoff.
Dan Wiggins
Adire Audio
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[Julian Data]

I agree with Sun of Pat here.
Also, be sure you have no other leaks besides the port's hole.
If you have a leak, the driver will still try to act as though it was in "free air".
jd
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[Andrew T]

Thanks Dan, thats exactly what I wanted to hear.
It actually makes sense, with little or no resistance/elasticity due to the size of the box, the cone is free to move to Xmax.
What I would like to know is how do you calculate a maximum wattage before you hit Xmax of a cone, given a certain box volume and tuning and or other parameters?
Patrick, the box definitely has no leaks and the tune is at 20hz.
Also, (please educate me) if it were true, why would a small leak (assumption no 1 that a small leak is about 1/8" or less) make a ported enclosure act like the driver was in free air? For the volume of air that is moving thru the ports, anything in that small a size order would be of little significance in effecting the elasticity/resistance of the air in the box on the cone. If anything, it might introduce its own resonant frequency producing a whistle.......
On another note, sheesh pat, you've been a member at HTF about the same time as me and youve got 6000+ messages...... man what do you do, sit on HTF all day and never watch any movies????