Aquariam hose barometric equalizer?

[aceinc]

I read somewhere about a DIY sealed sub that the fellow built and added a length of 1/8" aquarium hose, venting to the outside air. The stated purpose was to equalize the pressure when the weather changed, and after the air in the box heated up from use.

I would assume that a few feet of 1/8" hose coiled up in the cabinet venting to the outside would allow very restricted/slow quantities of air to pass. I wouldn't imagine it would allow enough air to pass so as to change the box to an aperiodic style, but I'm guessing.

The sealed subs I'm building will be .5-.6 cubic feet with a 10" dayton titanic.

Has anyone heard of this, better yet has anyone used this approach, and what were the results?

If there is no actual experience, what are your thoughts?

Paul

[Sonnie]

This is definitely a new one on me.... interesting. I wonder if we have any test measurements that prove it might work? Of course I doubt I'll go to the extreme of venting holes to the outside.

[Bent]

I remember that post somewhere too, it was a sub installed high up on the wall behind a cabinet of some sort.

I can't see it being a bad thing, plus the length of the tube/hose vs. the diameter would allow an exceptionaly low tuning freq. LOL.

or, it just isn't becessary due to the enclosre inevitably "breathing" anyways.

There are better folks who can comment on this one than me.

[WillyD]

You don't need to do anything like that.

You won't be putting enough power through that titanic to cause the internal air to rise much anyway...and enough power would probably destroy the woofer anyway.

The whole idea of a sealed sub is to literally make sure the enclosure is air tight. Otherwise, go ahead and build a ported.

[Exocer]

Cool idea but Will hit the nail on the head.

Either way, the amount of heat in the voice coil will fluctuate during use depending on how much power is being sent to it. Adding a small "vent" will not have a large effect on Vc heating IMHO, and the idea behind an acoustic suspension design is to be completely sealed. I'd assume with any type of air leakage going on there will be more than a 2db/octave loss in output below the enclosure resonance.

[Chrisbee]

I vaguely remember something about heating being a good thing for a sealed box. Since air becomes more rarefied with increasing temperature. It was claimed (decades ago now) that stuffing a sealed box with a particular fluffy material fools the driver into thinking the box is larger. This was due to the frictional heating effect on the stuffing material. I believe the stuffing recommended was long fiber/fibre wool. This is supposed to slightly lower the resonance of the system. If all this is true then a leakage would not be beneficial.

My own fuzzy logic suggests that heating the air causes it to expand. Which would increase the pressure and fool the driver into thinking the box was actually smaller than it is.

[Danny]

As said in earlier posts it's unlikely that the driver will cause much heating to the surrounding air, even my driver (600Watts) doesn't heat up that much. Air does expand when it is heated but to get any pressure increase that would affect the driver performance significantly the air would have to be heated a lot. Me thinks that ambient temperature will affect box pressure more.

[Chrisbee]

It wouldn't be difficult to check a sealed sub's response with different ambient temperatures using REW. The sub and the microphone position would have to be carefully controlled to avoid random variations. This assumes a test room without any climate control. Otherwise there would be little to measure except barometric pressure. Perhaps an outdoor test is best to prove whether temperature variations are worth worrying about? There may be members here able to save us some effort lugging heavy subs about if they have some existing data on temperature v response?

[ThomasW]

Does no one understand how much noise will be created as air is forced through a hole this size?

Read the Linkwitz site from information about this....

[Sonnie]

Without reading the Linkwitz site, I suspect it could be noisy.

[Exocer]

I didnt even think noise was worth mentioning, its that obvious to me at least.

[aceinc]

Thanks for all the replies, I've been busy building the subs (and working) and haven't had a chance to reply 'til now.

I suspect the noise would be negligble because the length of the hose in relationship to the diameter would not allow much air to be displaced rapidly. Slow air makes little noise. If you don't believe me, take 2 feet of 1/8" ID hose put it to your mouth and blow as hard as you can, I suspect the only noise you will hear is your pulse pounding in your temples, until you pass out.

I chose not to implement this, as I felt that I'm not such a good cabinet maker that these subs would be hermetically sealed. I thought of a way of fixing part of the sealing problem, get thick latex house paint and paint (or pour, slosh around and empty) the inside of the box before finishing. You can pick up gallons at HD or Lowes for $5.00, just ask for their "oops" paint. I've painted most of the inside of my house with this stuff by buying light colors by the gallon, and dark colors by the quart, and mixing to taste, my wife's taste of course. But the color doesn't matter for this application.

BTW, if I ever say I am going to use T-Nuts in a speaker ever again, please shoot me.

I will be posting pictures of the unremarkable looking subs and test results in a different thread.

Paul

[crackyflipside]

http://bass.consumes.us

There. He was also my inspiration for building the Rythmik servo sub.

His response:

[Exocer]

aceinc wrote:

Thanks for all the replies, I've been busy building the subs (and working) and haven't had a chance to reply 'til now.

I suspect the noise would be negligble because the length of the hose in relationship to the diameter would not allow much air to be displaced rapidly. Slow air makes little noise. If you don't believe me, take 2 feet of 1/8" ID hose put it to your mouth and blow as hard as you can, I suspect the only noise you will hear is your pulse pounding in your temples, until you pass out.

I chose not to implement this, as I felt that I'm not such a good cabinet maker that these subs would be hermetically sealed. I thought of a way of fixing part of the sealing problem, get thick latex house paint and paint (or pour, slosh around and empty) the inside of the box before finishing. You can pick up gallons at HD or Lowes for $5.00, just ask for their "oops" paint. I've painted most of the inside of my house with this stuff by buying light colors by the gallon, and dark colors by the quart, and mixing to taste, my wife's taste of course. But the color doesn't matter for this application.

BTW, if I ever say I am going to use T-Nuts in a speaker ever again, please shoot me.

I will be posting pictures of the unremarkable looking subs and test results in a different thread.

Paul

Cool. Looking forward to that thread