Bathroom audio

[Bill]

Today's unexpected question was from a lady friend who is having her bedroom redone and wants to have a small stereo system put, hidden away, into the bedroom with speakers in the en-suite so she can shower/bathe or whatever and listen to the radio. The people fitting out the rooms have given her a spec and she has asked me for comments.

They have suggested a simple mini system with AM/FM and CD, but cabled to some waterproof speakers in the en-suite area. The thing that struck me as odd was that the stereo is 8-ohm output, but the speakers say "fitted with 100volt transformer". Looking up waterproof speakers on the 'net, I see that most of them are indeed 100-volt line devices, although I seem to have found one 8-ohm pair.

The question is, is it normal to just connect a standard stereo to one of the tappings on a 100-volt speaker for this sort of use? If installing something like this, are there legal implications such as a requirement for isolating transformers in the speaker cabling? Their proposed speakers look like little round ones in a housing like car door speakers.

[John]

I believe such speakers will have been made for large public address / hotel / hospital type of installations

[John]

See:

would have thought that conventional ones would exist.

[Bob Minchin]

100v speakers deliver their rated power with 100v rms drive. Transformer tappings reduce this 100v to drive the speaker at a lower levels. Assuming the amplifier is designed for an 8 ohm system, it would have to ouptut 1250 watts rms to deliver 100v rms. So assuming a much lower output then the speakers are not likely to not be very loud. Ignoring any safety requirements, the 100v line units could have the transformers removed. Or another pair of 100v line transformers of the correct power, could be used to step the amplifier output up to 100v ready to drive the 100v speakers.

Bob

[tony sayer]

You can look at that like High Voltage power distribution where the power in this case the audio is "transformed" up to a higher voltage then stepped back down to a lower one.

The high voltage transmission overcoming the resistive losses of the long lines used in these applications..

Seems a bit over the top for a simple application like this tho!..

[Mike Barnes]

No.

CPC sell a variety of splashproof speakers in 4 ohm and 8 ohm versions, which would be more normal. They're generally similar in style to car door speakers, but white rather than black, for boats, caravans, pool areas, etc. Sizes vary from 2" to 6.5". Some are IP56 rated.

[Bill]

In message , Bill writes

100V line speakers are normal speakers, 8 ohm 4 ohm etc. with a transformer feeding them, just dis' the transformer and connect directly to the speaker. >

[Bill]

Hmmm, why didn't I think of looking at CPC? They also do a much cheaper

5" black 20watt one. The Panasonic stereo system is rated at 10watts rms per channel into 4ohms.

Their speakers don't seem to have the partly covered backs of the bathroom designer's ones, but I'd have thought that that wouldn't matter much as they would be built into a panel.

The other question remains.... are there any legal safety requirements regarding running speaker cables into a bathroom? The spec sheet of the Panasonic doesn't say whether it's double insulated or earthed, but I presume the latter.

I'll feed her some info to query with the bathroom people. I'm aiming to be more consult-i-y rather than d-i-y.

[Dave Plowman (News)]

Just disconnect the transformers and connect direct to the speaker - it will be nominally 8 ohms.

[Dave Plowman (News)]

Assuming the amp etc isn't in the bathroom, no. The maximum voltage the amp could supply to the speakers is not lethal. It might or might not have a reference to true earth.

[Adrian C]

A friend has normal HiFi speakers in his bathroom. Small 2-way Missions bookshelf types on wall brackets. They don't sound as if they are suffering from the occasional steaming.

[Tim S]

Bill coughed up some electrons that declared:

Although I see you have other lines of thought in progress, I think it might be worth adding for the record that it would be unwise[1] to take 100V into Zone 1 (above bath or shower base, crudely speaking), no matter what the IP rating of the speakers.

[1] IEE Wiring regs, 17th - SELV only permitted, with additional limitations.

Zone 0 - max 12v RMS AC or 30V smooth DC, both SELV + IPx7 Zone 1 - max 25V RMS AC or 60V smooth DC, both SELV + IPx4 or IPx5 if water jets.

Zone 2 would be allowed, if the equipment met IPx4 or IPx5 (jets).

The fact it's not a power circuit doesn't affect the applicability of the regulations.

In the light of that, and as I think I gather, you are looking at normal speakers, it would be a good idea to take extra care with the speaker wiring, and the amplifier to ensure there's minimal risk that mains could become present on the speaker circuit. I would use mains voltage rated cable for the speaker wires and keep them as far from any mains wiring as practical. But then I'm a bit paranoid :)

Cheers

Tim

[geoff]

In message , Bill writes

ITYF its illegal to transmit Spice girls down such cables ...

[Trevor Smith]

All you need are speakers with mylar cones

Smith

[Dave Plowman (News)]

In a normal domestic bathroom ordinary speakers will do just fine. I've got some ceiling ones - originally with 100v line transformers - which came from TLC, although they don't do them anymore. 8" unit so plenty of bass when mounted in the ceiling.

[tony sayer]

In article , Bill scribeth thus

Do you get to test it to spec whilst shes in there under "operational conditions";?...

[The Natural Philosopher]

That's correct. I have even installed such. They are, with the proper transformers, usable over long lengths of wuite thin cable, and, as we discovered, proof against most near misses from lighnting strikes that used to destroy the back end of any low impedance audio amp they were attached to.

Two points.

1/. Its probably OK to use 8ohm stuff in a bathroom.

2/. If you do use em, simply get a pair of 8ohm to 100volt line transformers for the other end of the wires

[The Natural Philosopher]

If you have plastic cones they wont.

3 years installing audio eqpt., in S Africa showed what lasts in difficult envirionments and what does not.

Paper cones came bag like tissue paper after being exposed to sunlight (UV), or like blotting paper after a storm. Amps came back fried from lightning near misses.

The weak points are

- anything biodegradable biodegrades. That is the cones themselves, if paper, the surrounds - foam surrounds are bad, but rolled rubber last reasonably well out of direct sunlight, and occasionally spiders went. Probably through overpowering.

- copper wire and soldered joints corrode badly in the presence of damp air if any sort of acid flux residue is left, and even normal flux aint perfect. Clean and apply varnish...you should see what a beach environment with salt in the air does to aluminium based chassis as well..

But a tacky placky set of car speakers is probably the way I would go. They are mainly plastic and synthetic rubber, and corrosion will probably not be great in a well ventilated bathroom, only used occasionally.

[Dave Osborne]

Can you tell me which specific regulation applies here, Tim?

[Mike Barnes]

Added to which they're cheap and easy to replace if they fail.