vacuum enclosure

[Shpoop]

anyone ever tried it? i was thinking some sort of small, airtight enclosure like those spheres (sorry, i forgot who did them), but add nothing inside, and make it a complete vacuum.

the sound will be obvioulsy softer, because u are effectively killing all the sound and air that is moved from the back of the speaker, but you are also killing all the distortion and unwanted resonances that come with it. The spider and cone would also meet with less resistance when trying to move.

I dont need things to be very loud, so should i give this a shot? i can imagine that it might be dangerous for the driver if done without caution, can someone elaborate on this aspect some more perhaps?

[joe carrow]

Originally posted by Shpoop
anyone ever tried it? i was thinking some sort of small, airtight enclosure like those spheres (sorry, i forgot who did them), but add nothing inside, and make it a complete vacuum.

the sound will be obvioulsy softer, because u are effectively killing all the sound and air that is moved from the back of the speaker, but you are also killing all the distortion and unwanted resonances that come with it. The spider and cone would also meet with less resistance when trying to move.

I dont need things to be very loud, so should i give this a shot? i can imagine that it might be dangerous for the driver if done without caution, can someone elaborate on this aspect some more perhaps?

All in all, that's a somewhat interesting idea. Of course, you would have to build drivers from scratch. If you ever do that, I'd love to hear how it goes!

The main problem to overcome is the force of air. Say you've got an 8 inch driver- that's 14 pounds per square inch on 50 square inches... 700 pounds!! You thought the sag from a vertically placed subwoofer was bad?

[sardonx]

A complete vacuum???

I think peole often forget how strong atmospheric pressure really is............................................. how robust do you think this driver's surround material would have to be (just one thing out of twelve that comes to mind)

[sardonx]

or how do you expect it to act as a spring when it's about to implode on a hazardous scale.. .

[Shpoop]

well i was thinking of something like a jx53... a small 5 cm diameter, and its made out of aluminum

and i dont think it would be that hazardous to the driver...i mean if you buy a belljar and experiment with vacuums, things can hold up for a while. Yes, if it was a complete vacuum, as soon as the driver tried to push out it would probably just implode, and if it was wired reverse polarity, it would probably just keep going in and implode...but im sure you can get it pretty vacuum-ized while still being pretty safe

but the thing is, would the added difficulty moving out due to pressure create a terrible loss of sound quality? or if it didnt, would it be because theres enough air in the back, so all benefits arent there anymore?


and also, you wouldnt have to build them from scratch...im sure theres a way

[joe carrow]

Originally posted by Shpoop
well i was thinking of something like a jx53... a small 5 cm diameter, and its made out of aluminum

Ok, so it's only got 40 pounds pressing on it

and i dont think it would be that hazardous to the driver...i mean if you buy a belljar and experiment with vacuums, things can hold up for a while. Yes, if it was a complete vacuum, as soon as the driver tried to push out it would probably just implode, and if it was wired reverse polarity, it would probably just keep going in and implode...but im sure you can get it pretty vacuum-ized while still being pretty safe

but the thing is, would the added difficulty moving out due to pressure create a terrible loss of sound quality? or if it didnt, would it be because theres enough air in the back, so all benefits arent there anymore?

Well.... here's a quick experiment. Take one of these drivers, and stack some weights on the cone. I'd be willing to bet you a pair of NSBs that the it would bottom out before the jx53 had more than 20 pounds on it. 40 pounds, for sure.

and also, you wouldnt have to build them from scratch...im sure theres a way [/B]

I honestly think that it could be done, if it was taken into consideration from the start. But you asked- would there be any benefits? I think that if you had two of these drivers playing bass in a bipole configuration, they could provide some benefits to linearity. The reaction forces on the cabinet would be canceled out since it's a bipole, and the lack of air could have benefits for linearity...

But you're talking about a 2 inch driver? As far as I know, we don't have a problem capturing and killing the back wave of a high/mid driver. Transmission lines with stuffing seem to be good at this- and B&W uses a stuffed tapered tube for that purpose.

In conclusion, I wouldn't recommend trying to evacuate a speaker enclosure; not even a little bit. Do it enough to have a physical effect and you'll break your driver, do it enough to count as having done it without breaking the driver, and you'll have the driver pushed way out of its equilibrium position, killing the linearity in BL and introducing all sorts of distortion.

I hope I don't sound like I'm discouraging you from asking all these questions- you're obviously new, curious, and interested in innovation.

[sardonx]

Now not to stump your idea or anything (crazy ideas are good.. everyone into diyaudio has them.. it's almost like a prerequisite) I've certainly had a few myself. But..

I think if you lowered the box pressure any significant amount (even enough to just pull it inwards 5mm) it would definetly affect sound quality. The reason this matters is because half of the signal will be compressed (no pun intended really). The outward motion of the driver that is.

You can try it but I think you'll find that it's a waste of time. Especially for such a small driver like the jx53 you do'nt need to get into manic ideas like lowering the air pressure. You should be able to completely rid of the back wave using conventional methods.

It's a nice idea. But in practicaly terms it probably won't do you much good. If you find otherwise.. you can come back and make fun of me.

[SmarmyDog]

Very insightful Shpoop!

WARNING: SHAMELESS PLUG FOLLOWS…

Check out my pending patent here , then let’s chat some more. I’ll try to get some pictures of my prototypes up on the web soon…

NOTE: If the link doesnt work, you can search uspto.gov for patent application publication number 20040136560 (Condensed speaker system).

-Casey Walsh

[joe carrow]

Originally posted by SmarmyDog
Very insightful Shpoop!

WARNING: SHAMELESS PLUG FOLLOWS…

Check out my pending patent here , then let’s chat some more. I’ll try to get some pictures of my prototypes up on the web soon…

NOTE: If the link doesnt work, you can search uspto.gov for patent application publication number 20040136560 (Condensed speaker system).

-Casey Walsh

Very interesting! You didn't happen to patent the exact opposite, did you?

[sardonx]

Shpoop.. I mean Smarmy Dog, how come the drawings of the implementation don't come up?