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Does anyone have any experience with these devices? According to the Mtronics website both the speaker and the driver are waterproof. Can the driver be placed outside the pressure hull?
Joel Labow
Joel Labow
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They are mylar coned speakers. I would not say they are 100% waterproof. The cone itself is, but the magnet assembly and voice coil will still corrode over time.
Getting decent sound into a submarine is a difficult trick to say the least, ask me how I know! -
I thought it looked too simple...how about the electronic drivers? I am collecting my options for a Revell 1/72 Gato build and the only way that I can see to manage it at this scale is to place both the speakers and the electronics out side the pressure hull.
Thanks for your thoughts,
JoelComment
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Instead of having the speaker transducer rattle a cone, get rid of the cone, and glue the transducer to the deck. Just like a guitar or other stringed instrument - the body resonates at audible frequencies.
As a Diver we used 'bone-phones' that rattled our skull, making noise. Not Hi-Fi quality, but we could make out the Supervisor cussing us out clear enough.
DavidWho is John Galt?Comment
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David,
Since I just shelled out for my Robbe F16 twin throttle ($502...ouch! I made the mistake of waiting until after the election to order...the decline of the dollar cost me an extra $25!) i was thinking about a separate speaker for each throttle. I did this with my 1/124 Graf Spee and found that it gave a more complex realistic sound.
JoelComment
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On American Diesel-electric submarines since the mid-30's -- when we de-coupled the shafts from the diesels forever -- you won't hear diesel engine sound changes with changes in bell. The motors are the only prime-mover connected to the shaft and normally work off the battery as the diesel-generators 'float' the battery charge, i.e. the generator cranks in the make-up current, stored in the battery chemistry, then yanked out by the load -- ships services and motors. So, no direct correlation to bell and engine sound. Sorry.
DavidWho is John Galt?Comment
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That's precisely what I was playing around with on the Yellow Submarine. I was using nxt drivers, which essentially are voice coils built to directly mount onto a surface, and excite that into producing sound.
My experiments proved that using smaller drivers doesn't work well on stiff substrates like GRP. Also if you have a hull with a lot of curves like the yellow sub, it stiffens it up even further, resulting in virtually no output or very poor efficiency.
There is a nxt driver produced that is designed to work well with thick or stiff substrates. However it's very heavy, and takes a fair few watts to drive it.
When placed on something light and flat e.g. a flat sheet of expanded foam, the drivers work exceptionally well. For a boat like the Gato, with it's wide flat deck, you may get this to work better. I got my nxt drivers from Partsexpress.com. Great company for unusual speakers, and I wish we had something like that available here in the UK. They're very cheap, so you won't have to fork out much to experiment.
For instance four of these drivers wired in parallel will present a 4 ohm load for an amp to drive-
Here's a link showing the full range of tactile transducers
They also do some neat full range miniature loudspeakers. Models produced by Hiwave, Peerless and Dayton Audio are high excursion design, meaning you can get a good frequency response from a small diameter driver. Also meany of these smaller speakers use plastic cones (as opposed to doped paper), so that part should work okay in the water, you still need to find a way of sealing the voicecoil, spider and magnet- perhaps dipping in a rubber solution might work. Boxing them would be ideal in sonic terms, problem is, as you dive the cone will compress, and your boat will lose it's trim.
Last edited by Subculture; 11-10-2012, 07:23 AM.Comment
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great minds think alike, Andy.Who is John Galt?Comment
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David,
Wouldn't the sound intensity vary depending how many engines were on the line? Or were all 4 always running?
JoelComment
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No, the mains were not all on the line. When you need to make electricity you run what you need to get the charge up AND carry the load of the main motors. In peacetime, as long as you could float the battery for the bell you were cruising on, a slow charge was fine if you could do it with two mains without beating them to death -- pulling too much of a load from an engine shortened its between-overhaul life.
The electrical load relates to torque presented by the generator directly coupled to the diesel engine. Increase the electrical load (charging the batteries AND supplying the propulsion motors AND dealing with ships services means more fuel, more strain on the crankshaft, wrist-pins, connection rods; and hotter operation), so most often at least two mains were cranking when making electricity with hydrocarbons.
If you were heading home you usually ran all of them (three mains on the TRUTTA) unless you wanted to screw the in-port watch-section, keeping them up all night pier side topping off the batteries, as the rest of us hit Duval Street.
But, there would be no noise variation with bell changes if you had 1,2,3, or 4 main engines on the line. Bell changes would make the engines 'grunt' if the battery was not between them and the motors to smooth the surge, but even that sound was very subtle.
It was a good engineering practice to stagger engine operation to keep about the same hours on all so that when you went in for a yard period, all the engines would have racked up the permissible run-time. We had no problem watching the hours as we had Fairbanks-Morse diesels and there were plenty of spares out there (our engines were very much like those used by the railroad guys with they're diesel-electric plants, so the system was full of spares). The GM equipped boats had to tip-toe with their diesels, particularly those boats still using the pancake GM's. (What stoped use of the ALBACORE was the absolute non-availability of pancake diesel engine spares).Who is John Galt?Comment
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