12v PC/MP3 Speakers

[Inselaffe]

I have these speakers on-board which I play my Palm PDA through.

At the moment I use my inverter to give the required 240v from my 12v battery, which I guess cant be very efficient.

Do such speakers actually work on DC, ie could I take them apart and make them work directly from 12v?

Or are there any 12v powered similar speakers on the market.

I don't have a car radio on-board so an FM transmitter isn't an option (re answers to previous poster).

 

[Como]

If you look in the extended specification for the speakers the power supply is shown as "External" so presumably a wall block type power supply is used. What is printed on the power block? If it shows 12v DC then you are in luck, just replace the power block with a direct connection to your 12v supply.

John

 

[Inselaffe]

must be a misprint, no external block /forums/images/graemlins/frown.gif

How do these things work, is there a transformer to get the voltage down and then a rectifier to convert to DC?

If internally the voltage used isn't 12v (& how would I know from looking inside?) could I somehow run direct from 12v without AC?

Or is the power consumption, even with inverted as I use now low enough that its not worth worrying about?

 

[tom52]

My PC speakers that came with my Dell have an AC plug with built in transformer that coverts tha 240v AC to 12v DC.

I am looking for another pair to use on board (with the transformer removed) directly from the boats 12v supply and plugged into my Ipod

If I unplug my Dell speakers from my PC and plug them into my Ipod it works OK.

I just need to find another pair of active PC speakers that are 12v and I am in business. Some of the others I have looked at are transformed to 9V and some just dont say.

 

[srp]

From looking at the spec of the speakers, I would think that the transformer is built into one of the speaker enclosures. The (probably rectified) output from this is then fed to a little amplifier. The audio signal will also go into this amplifier, and the output will be fed to each of the speakers (maybe via a crossover unit, since there are 2 speaker cones in each enclosure).
If you take the enclosures apart you might be lucky and find a voltage label on the transformer. If not, (and if you promise not to electrocute yourself) stick a DMM across the output terminals of the transformer while it's all plugged in. If you're not happy poking around where there is live 240v don't do it (not saying you're incompetent, but I'd hate to look over towards the East coast and see a huge incandescent glow in the sky).
The alternative is to look for a pair of computer speakers which operate from a 12v power brick, which is more or less what Como suggests, or to buy a pair of battery operated JBL on-stage speakers (which are top quality, but expensive).

 

[William_H]

From the specs of 2.5 watts RMS per channel we could surmise that the supply voltage for the amp is around 12 volts. They are not usually fussy in that an amp designed for 9 volts probably won't blow up while an amp designed for 18 volts will simply give a little less power.
Higher power equals higher voltage supply to the amp.

However the amplifiers can be run from +12 volts as in a car radio or quite often from a +12 volts and -12 volts. These voltages are easy to get from a transformer but not easy from a ships battery.
(Don't be confused I don't mean a 12+ve wire and a 12v-ve wire but 3 wires ie 12v+, ground or 0 and 12v -ve)
The use of +and -ve enables the output to go straight to a speaker hence better low frequency response and the effectively 24 volts gives more power.
So investigate the power supply arrangement but be aware this may be what they have done. There are generally large cylindrical electrolytic capacitors which store and smooth the voltage from the rectifier. If you measure a DC like 12 v across one capacitor and there are 2 caps then the voltage from a negative of one cap to pos of other cap may be double the voltage of just one. (if you get the wrong pos and neg terminals you get 0v.

if you find one cap in the power supply area with just around 12 volts then that is the place you connect your 12v ships supply. Provided only 240 or 12 is connected at any one time there should be no need to disconnect anything just add the extra wire.

As you can see this is all a bit technical (possibly dangerous). It may be easier to connect a car radio with external inputs. You can likely identify the speaker connections in your existing powered speakers. These can be connected to the car radio speakers.
Good luck olewill