Underwater speakers

[tylervitale]

Can anyone tell me how underwater speakers work? I tried googling it, but it seems the topic is somewhat obscure... Wikipedia has no article on them, nor can I find a place explaining them.
Or is it because they are just regular speakers, but water proof? There must be some difference though!

 

[Hero999]

That's it, they're just normal speakers but just waterproof.

The cone is obviously made of plastic, rather than paper and the electrical connections are sealed and waterproofed.

 

[Birdman Adam]

You mean something like this?

**broken link removed**

Yea, they work, quite well actually. I was surprised when I heard some in the community pool. They looked just like the one above. Honestly, they sounded almost the same as above-water speakers.

But the size and shape of the pool matters a lot. Usually, if you place it in the deep end, by the time you get to the shallow end, you can't hear it so well.

 

[Reloadron]

I Googled Underwater Speakers and got plenty of hits including this thread. Also a Google of Underwater Acoustics brought up some real interesting stuff.

Ron

 

[canadaelk]

Lowell Mfg. and Atlas Sound make (made?) them for pools. They are like regular speakers, waterproof cone and back-box. Do not expect HiFi or stereo! E

 

[Birdman Adam]

Just noticed:

I don't know about others, but the few I found were quite expensive! Like 200+ USD.

 

[Sceadwian]

The voice coil of a speaker by it's nature has to be insulated so it's already water proof. You could submerge most any speaker you can find under water and it will work probably not as well though because moving water is a lot harder than air so it's resonant properties will change dramatically. All you'd really need to do in insulate the leads that go to it, completely.

I'm sure the physical construction of underwater speakers is very different from normal speakers because of the way water moves as opposed to air simply changes the equation. The increased cost is simply because it's a niche market, only a fraction of the increased cost can be attributed to the difference in designs, especially once one has been made that can be copied or learned from.

 

[Ross Craney]

The voice coil of a speaker by it's nature has to be insulated so it's already water proof. .

Insulated is not quite the same as waterproof

 

[Hero999]

The connections to the voice coil will almost certainly not be water proof.

The cone of most speakers is also made of paper, which won't last or very long when submerged in water.

I wouldn't even trust a Mylar film conned speaker because the voice coil connections will probably not be waterproof, the voice coil former might be paper and the magnet and metalic frame will almost certainly go rusty, especially if it's submersed in a chlorine solution which is very corrosive.

I Mylar film conned speaker might work if the back is waterproofed and only the cone is in direct contact with the water; maybe you coul put it in a floating speaker cabinet, as in the picture posted by birdman?

 

[Dragon Tamer]

I took a stab at making my own under water speakers one time. I just took some small speakers from an old alarm clock radio put them in a PVC pipe and sealed it up. The problem is that I needed to drill a hole in the side of the PVC to run the signal wires back up to the surface so that you could actually hear something.

The end result was that they worked pretty well as long as the filter was not running. But they also had a nasty habit of letting water into the pipe where the wires went in. I was going to make another attempt to do better this year by using PVC that is acutally threaded so it will be easyer to get into the unit to fix a problem, as well as finding another way to get the signal into the pipe.

One way of doing this is taking stainless stell washers, nuts and bolts, and drilling several small holes into the side of the pipe, and connecting the signal wires to the outside and another set of signal wires will be connected on the inside.

 

[Hero999]

What about using a piece of pipe to couple the sound to the water and have the speaker out of the water?

You'll probably still need to use a Mylar conned speaker, as the high humidity might ruin a paper cone but at least you won't have to worry about insulating the electrical connections.

 

[Dragon Tamer]

That's a brilliant idea! I don't know why I didn't think of that! I'm going to do that. Thanks Hero

 

[Externet]

If a speaker with a pipe into water worked, sounds over the surface would be heard underwater. It does not happen.
The transducer element has to be submerged.

 

[Hero999]

If a speaker with a pipe into water worked, sounds over the surface would be heard underwater. It does not happen.
The transducer element has to be submerged.

No.
A pipe will improve the impedance matching between the cone and the water so the sound will be transferred to it more efficient.

 

[Sceadwian]

Insulated is not quite the same as waterproof

In general it is, if the wire ends are sealed as I said they should be.

Hero while you're right so is Externet, a speaker in a sealed PVC pipe would waste most of it's energy as the energy reflected off the PVC pipe many times, basically ending up as minuscule heating in the plastic, some sound would transfer through the PVC pipe but you'd need a flexible membrane in direct contact with the water moving to transfer sound efficiently. So it really goes to asking what you consider an under water speaker, one that works, or one that works well =-)

 

[Ross Craney]

In general it is, if the wire ends are sealed as I said they should be.

)

No - generally it is not. In a specific case it may be. I think that a little investigation will reveal that the voicecoil enclosure is not watertight at all.

 

[Ross Craney]

In general it is, if the wire ends are sealed as I said they should be.

)

No - generally it is not. In a specific case it may be. I think that a little investigation will reveal that the voicecoil enclosure is not watertight at all. The wires from the terminals to the voicecoil are usually not even insulated let alone watertight.

 

[Hero999]

In general it is, if the wire ends are sealed as I said they should be.

Hero while you're right so is Externet, a speaker in a sealed PVC pipe would waste most of it's energy as the energy reflected off the PVC pipe many times, basically ending up as minuscule heating in the plastic, some sound would transfer through the PVC pipe but you'd need a flexible membrane in direct contact with the water moving to transfer sound efficiently. So it really goes to asking what you consider an under water speaker, one that works, or one that works well =-)

I don't see how much of the energy could be reflected or lost inside the PVC pipe, maybe higher frequencies could be reflected back and fourth between the speaker's cone and the water's surface, if the impedance isn't well matched but I don't see how significant amounts of energy could be wasted inside the pipe, especially if it's kept as short as possible.

 

[Sceadwian]

It is impossible to match the impedance, you're talking about a water to air boundry layer, most of the sound of any frequency will bounce right off the water, it can't just seamlessly pass through that great a density change, the tendency is going to be reflecting off the denser layer. This can be easily proven by showing how well sound travels when the air and water temperature conditions over a still lake are juuuuuuust right an area thermal difference in the bulk air and the air right next to the water form a waveguide, and that's just with thermal density differences in open air, what you're talking about is a liquid to gaseous boundary layer. You'll get almost total reflection. Doubt me? Submerge yourself in water and have someone standing right next to you scream as loud as they possibly can (with their upper body out of the water) You'll barelly hear a thing because there's an air column still in your ear that meets with the water, and an air cavity at the surface of the water to the person yelling.

Make no mistake about it, it will work, but you'll get really attenuated audio with horrible peaks and valleys.

 

[Sceadwian]

Ross... I'm not sure if you actually read my post, I specifically stated that the actual electrical connections to the speaker cone would have to be insulated, this would include the naked wire up to the voice coil itself. The enamel insulation on the voice coil itself WILL insulate from water penetration at shallow depths.

All you'd need to do is take a hot glue gun and surround the wire just past the electrical connector and up to the voice coil itself. After the hot glue has dried just for pressure sealing I'd use a zip tie to create pressure as the hot glue seal alone isn't going to protect very well from pressure leakage.