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Old 8th September 2003, 02:18 AM   #1
Guss is offline Guss  Canada
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Default Water chamber sub

I found this threadwater about water methods but it is not really helpfull. I now it is not a common concept but I want to give it a try. I have an idea of what I want. Logically it would be a 4th order bandpass sub with the closed section of it filled with water. The magnet would face the port in a big Pvc tube. I still need inputs on tuning and other basic things to know about water and sound. I would use a 6'' driver so a big tube may be hard to find, any idea? I did many tests on cone resistance and it seems that ''plastic'' cones doesn't react to water and moisture. any comment would be apreciated.
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Old 8th September 2003, 04:23 AM   #2
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(first, I love the profile pic... domo-kun is my favorite )

I've often wondered about the same thing. I think, however, that getting a suspension that was both waterproof and allowed the cone to move more than .5mm, would be a stretch. I suspect the final solution would be to throw a rave in an olympic-sized pool, and one side of the pool is a wall of woofers... the chamber of the woofers would probably have to be pressurized.

This cold present problems, though. If people get nasty in the water, you have all kinds of liability issues with STDs and the like.

Another alternative would be to hold the party in a pressurized room, just a few atmospheres. This gives the problem that if, for some reason, you need to get out in a hurry, you have to wait patiently for the room to get to normal pressure, or risk getting the bends.

In the end, if you're looking to increase efficiency, look into horn-loading. There's a page out there (can't be bothered to find it--google?) with a floor-horn cast in concrete that gets 110 dB efficiency (that's efficiency, not max SPL) at 10hz... and, IIRC, it's not even that big of a room, I think that would probably be big enough for your needs.

If you can come up with a driver that's waterproof though, I would love to try it...
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Old 8th September 2003, 05:41 AM   #3
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Having the magnet face the side with away from the water chamber is a good idea.

You really don't need a waterproof suspension.

I have two suggestions.

A) Take a big sheet of Saran or vinyl sheeting-much larger than the cone area-and glue it over the cone. Don't glue it over the surround, just cover the surround-the water pressure will hold it tight-and glue the remainder of the vinyl sheet to the board that separates the two chambers. This will waterproof everything.

Saran wrap is vinyl. Why vinyl? Because it has all the waterproof capabilities of the usual plastic sheeting-plus many, many glues stick to it very well. The usual plastic wrap or sheeting-polyethylene-virtually nothing sticks to very well. Several glue companies have told me this.

For any hobby project where you think of plasic sheeting, think Saran or vinyl sheeting instead. It reallly is important. Vinyl sheeting is easily and cheaply available in several thicknesses from hardware stores, where it is used as dropcloth material. Also "Everything for A Dollar" type stores carry vinyl shower curtains cheaply.

B) Don't bother covering the speaker at all-just put the water in a waterproof bag and put it in the closed chamber. The bag itself will prevent the water from spilling-not the speaker. The pressure of the water against the speaker will guarantee 100% contact between the speaker's cone and the water bag.

Will condensation have water form on the inside of the speaker cone and magnetic structure and eventually cause rust? I don't know. Maybe yes, maybe no.

Let us know how you make out.
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Old 8th September 2003, 05:49 AM   #4
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Third suggestion.

Buy a tube the speaker just fits in. If unavailable, buy a slighly gigger tube and cut a circle from wood that creates a tight seal. then cut an opeining in the cicle and mount your speaker to that.

Fill a balloon with water and make sure it is tightly sealed. Baloons are made from lates, I believe, and many glues stick to latex if you want to glue the balloon shut.



Then put that wooden piece on which you have mounted your speaker, stick it in the pipe until it makes full contact with the baloon, put the cap on the pipe which contains a hole with a tuned port, and there you go.
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Old 8th September 2003, 06:04 AM   #5
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Here is a quick drawing of suggestion number 3.
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File Type: gif water chamber speaker 2.gif (1.8 KB, 1040 views)
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Old 8th September 2003, 11:09 AM   #6
VEC7OR is offline VEC7OR  Lithuania
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the problem with last pic is that water is too dense for it, we can get a standing wave in there but we neeed a tweeter...
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Old 8th September 2003, 11:51 AM   #7
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Water is simply not compressible enough to build a sub like that !

A water-filled balloon that is only taking up a part of the space would have some effect thogh, depending upon placement. If it fits tightly into the tube's diameter and placed closely to the driver, it will increase the driver's moving mass. I do not see the advantage over attaching a solid weight to the driver however.

Because the balloon also represents a compliance it will show a resonant behaviour with a very low resonant frequency.
Maybe that would be usable trick: A passive radiator constructed as some water filled bubble !?

Regards

Charles
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Old 8th September 2003, 12:56 PM   #8
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Default Hydrolastic suspension components with your name on them??

Quote:
Originally posted by phase_accurate
Because the balloon also represents a compliance it will show a resonant behaviour with a very low resonant frequency.
Maybe that would be usable trick: A passive radiator constructed as some water filled bubble !?

Regards

Charles
Maybe some of these old suspension thingies could be used for a super-duty high-order LF system?
http://austin1800.homestead.com/Page16.html
I had one many years ago. They work. On the car, that is.
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Old 8th September 2003, 01:30 PM   #9
Wizard of Kelts
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Quote:
Originally posted by phase_accurate
Water is simply not compressible enough to build a sub like that !

A water-filled balloon that is only taking up a part of the space would have some effect thogh, depending upon placement.

Regards

Charles
Okay, then the heck with the tube and the water balloon. How about filling a non-stretch vinyl bag with water, and let the sound be propagated through that?
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Old 8th September 2003, 01:58 PM   #10
Volenti is offline Volenti  Australia
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What's stopping the weight of the water from pretty much "bottoming out" the driver, you can't rely on the air pressure in a rear sealed section since it's very difficult to get a perfect long term seal.
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