importance of pin hole pressure equalization and how to make one safely

[poobah]

Right...

All of the energy sent to a speaker gets turned into heat (or reflected back to the amp... again, heat). only about 2 or 3 % gets out of the enclosure (sound)... the other 97% stays inside (a sealed enclosure anyway).

[sdclc126]

Poobah -

"A lot of complexity here... and all of it avoidable."

"This is about common sense... don't ask an audiophile."

Please tell me I have misinterpreted the meanings of these two statements - they both sound like slaps in the faces of all of us participating in this discussion.

Exactly what is "avoidable" here - debate and discussion? Educated opinions? Personal experience? And has every single one of us NOT been using common sense?

[poobah]

CLC, my apologies,

Yes and no... all of your remarks are dead on the money. Something about someone not understanding Linkwitz set me off.

[mazurek]

Haha, poobah, the exploding kayak story is a convinving case that I can deal with making one small hole in the box. Off to find some small tubing to glue in. That sounds like the best idea so far for adding a hole smaller than drill bits. (Being that all my changes should be reversible, I don't want to modify the dust cap as one poster suggested)

[poobah]

Cool,

Any hole will make a little noise... probably ultrasonic... but you wont hear next to it sub.

Please don't write back explaining how it messed up your imaging, transparency, soundstage..............................

[sdclc126]

Originally posted by poobah
CLC, my apologies,

Yes and no... all of your remarks are dead on the money. Something about someone not understanding Linkwitz set me off.

Well thanks Poobah - that is a perfectly acceptable answer - and perhaps I am easily set off myself, and easily misinterpret.

About something regarding not understanding Linkwitz that set you off, I think that was Post #12 by Noah. I hope you're not referring to my response to that post!

Anyway, I took no offense at Noah suggesting that I had misunderstood Linkwitz' reason(s) for using a pinhole - there's a ton of stuff Linkwitz says I don't understand - he doesn't exactly speak in layman's terms all the time - the guy's a Ph.D in electrical engineering and obviously (to me) brilliant.

I should read his section about the Thor subwoofer again in detail some time, but to the best of my recollection the pinhole relieves the driver from the "spring" effect of the air in a sealed chamber - I simply could have been mistaken about the benefits.

Cheers.

[dscline]

Originally posted by sdclc126
to the best of my recollection the pinhole relieves the driver from the "spring" effect of the air in a sealed chamber - I simply could have been mistaken about the benefits.

I'm quite sure the intent is to equalize the pressure inside and outside the cabinet, which could become out of balance due to heat, barometric changes, etc. A 1mm hole simply wouldn't be big enough to have any real effect on the driver induced spring effect at the frequencies we're talking about.

[poobah]

Yep,

While the hole will relieve the spring effect... the driver will not see it.

It's usually never an issue... but then rowboats aren't supposed to explode.

[BAM]

The idea is to create a hole that's resistive enough that the pressure differentials during operation inside the enclosure won't create any serious air movement through the hole, but air can very slowly pass through it to do the pressure equalization thing.

I wonder if this would be more important in car audio, where the temperature differentials tend to be bigger and create more of the expansion and contraction. However, I cannot imagine that this would be important enough to do with today's long throw drivers where an offset of even 1 millimeter isn't doing anything terrible.

[dscline]

Originally posted by BAM
I cannot imagine that this would be important enough to do with today's long throw drivers where an offset of even 1 millimeter isn't doing anything terrible.

Unless my math and wild guesses in the posts above are way off, I think pressures in excess of 25lbs can EASILY be realized on a driver under the temperatures that could easily be reached, IF the box were absolutely air tight. That would certainly be enough to push the driver more than 1mm. It'd be enough to push it to the end of its ecursion. Obviously though, this is not typically an issue with most sub construction. The biggest unknown here is how leaky a "tight" box really is.