I've got a question for you guys...

[RAM_Designs 5,000+ posts]

I've got a question for you guys. I just recently got the 21" Autotek sub running off of a SAZ-1500D, and I've been running tones though it, testing it out a little.

I notice that when I'm doing the tones near full volume, or I guess near as loud as I'd be comfortable playing it, the cone starts to slowly oscillate at about 2 cycles per second, as well as playing the tone. The oscillation probably has 1/2" p2p movement.

Is this an effect from having too large of a box, where there isn't enough of an air spring to keep the cone in check? With the 1500 watts I'm running right now, I can damn near make the sub reach mechanical limits, even right around tuning. So I'm thinking that shrinking the box down to 7 cubes, from 8.5 cubes, would do it some good....what do you think?

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[helotaxi 5,000+ posts]

It sounds like cone breakup because the cone is too big for its own good. Cone rigidity is insufficient for the size of the cone. There's a reason that 18s are usually the biggest subs made. For a bigger cone, rigidity must increase exponentially with cone diameter and mass must increase exponentially as well to achieve this. Heavy moving mass reduces the sub's efficiency so big subs are usually underbuilt for their size (there are notable exceptions).

 

[brtnboarder3241 5,000+ posts]

It sounds like cone breakup because the cone is too big for its own good. Cone rigidity is insufficient for the size of the cone. There's a reason that 18s are usually the biggest subs made. For a bigger cone, rigidity must increase exponentially with cone diameter and mass must increase exponentially as well to achieve this. Heavy moving mass reduces the sub's efficiency so big subs are usually underbuilt for their size (there are notable exceptions).

what he said

//content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

 

[kovemaster559 5,000+ posts]

he sounds rite

 

[RAM_Designs 5,000+ posts]

It sounds like cone breakup because the cone is too big for its own good. Cone rigidity is insufficient for the size of the cone. There's a reason that 18s are usually the biggest subs made. For a bigger cone, rigidity must increase exponentially with cone diameter and mass must increase exponentially as well to achieve this. Heavy moving mass reduces the sub's efficiency so big subs are usually underbuilt for their size (there are notable exceptions).

so cone breakup by itself will cause it to slowly oscillate like that? Is there anything else that could be the issue?

 

[helotaxi 5,000+ posts]

Not likely. Making the box smaller will exert more force on the cone and make matters worse, not better.