[FlatProblem]

Is there any technical reason why I couldnt user a set of speakers designed for a car, as celing speakers for the kitchen?

I know that car head units (usually) work at 12v rather than 240v, but does this matter at the output stage?

[paulyoung666]

the voltage is immaterial , you need to know what impedance they are , i.e 2 ohm , 4 ohm or whatever , hope that helps

[FlatProblem]

Good good, thats the answer I was hoping for - now where my drill...

[kokomo]

No problem. First fitted these in my kitchen wall and bathroom ceiling wired to lounge audio system some 25 years ago when the concept was pretty unique I can tell you!

Brian

[chrisjr]

The power supply the driving device works at is irrelevant. What is important is how many volts and amps come out of the speaker terminals.

Provided the rated power of the amplifier you are using is equal to or below the maximum rating of the speakers you should be OK.

But.....

Just double check the spec sheets for both speakers and amplifier for the Impedance figure. Many domestic amplifiers are only rated for 8 ohm speakers but a lot of car speakers are 4 or 6 ohms.

What this means is that the speaker will draw more current from the amplifier at any volume setting than an 8 ohm speaker would. At lowish volumes this should not be a problem. But at high volumes it could easily over load the amplifier making it run way too hot and, unless the amplifier has appropriate protection circuits, pop the power transistors on the output stage!

[soulboy77]

A friend of mine had a car cassette radio and speakers imbedded in his kitchen partition wall.

[FlatProblem]

Originally Posted by chrisjr

Just double check the spec sheets for both speakers and amplifier for the Impedance figure. Many domestic amplifiers are only rated for 8 ohm speakers but a lot of car speakers are 4 or 6 ohms.

I believe you are right, my amp is 8ohm, and the majority of car speakers seem to be 4ohm, so I guess I could get 2 pairs of speakers and wire them in series.

Our of interest, would wiring speakers in series give twice the perceived volume?

[niall campbell]

Originally Posted by chrisjr

The power supply the driving device works at is irrelevant. What is important is how many volts and amps come out of the speaker terminals.

Provided the rated power of the amplifier you are using is equal to or below the maximum rating of the speakers you should be OK.

But.....

Just double check the spec sheets for both speakers and amplifier for the Impedance figure. Many domestic amplifiers are only rated for 8 ohm speakers but a lot of car speakers are 4 or 6 ohms.

What this means is that the speaker will draw more current from the amplifier at any volume setting than an 8 ohm speaker would. At lowish volumes this should not be a problem. But at high volumes it could easily over load the amplifier making it run way too hot and, unless the amplifier has appropriate protection circuits, pop the power transistors on the output stage!

so 4 or 6 ohms speakers take more power to power them than 8 ohms amps. ....................... for a normal guy i thought it would be the other way 4 or 6 ohms would be ok as the amp is 8 ohms but its the reverse then?

[chrisjr]

Originally Posted by FlatProblem

I believe you are right, my amp is 8ohm, and the majority of car speakers seem to be 4ohm, so I guess I could get 2 pairs of speakers and wire them in series.

Our of interest, would wiring speakers in series give twice the perceived volume?

That would work. Two 4 ohm speakers in series would be equal to one 8 ohm one.

But no they would not be twice as loud as one. Basically each speaker has only half the voltage across it as it would if it were on it's own. so the volume from each individual speaker would be reduced as well.

And because of the way the ear works a simple doubling of the power into a speaker does not produce a doubling in perceived volume. in fact to double the perceived volume you actually have to increase the power output by a factor of ten!

ie 100W is twice as loud as 10W but to double it again you have to go up to 1000W

[FlatProblem]

Originally Posted by chrisjr

But no they would not be twice as loud as one. Basically each speaker has only half the voltage across it as it would if it were on it's own. so the volume from each individual speaker would be reduced as well.

Oh dear! So the volume in the kitchen would be quieter than the living room doing it this way? (the reverse would be ideal!)

Thanks for the advice folks!

[chrisjr]

Originally Posted by niall campbell

so 4 or 6 ohms speakers take more power to power them than 8 ohms amps. ....................... for a normal guy i thought it would be the other way 4 or 6 ohms would be ok as the amp is 8 ohms but its the reverse then?

The big factor here is the current drawn.

A four ohm speaker will draw twice as much current from an amplifier than an eight ohm speaker at any given voltage output. Current is inversly proportional to impedance. So as impedance goes down the current goes up by the same factor. There is obviously a limit to how much voltage and current any amplifier can produce.

The powewr output figure for an amplifier only has meaning if the load impedance is specified. In the case of HiFi kit the norm is for speakers to be 8 ohm so power figures are quoted for that load.

If the amplifer is capable of it then it will deliver twice as many watts into a 4 ohm speaker as a 8 ohm one because the current drawn will be doubled.

The problem lies with the limits on current and voltage that the amplifier can handle. If the amplifier can only deliver a certain maximum current it will obviously hit that limit far sooner into a 4 ohm speaker than an 8 ohm one. If you crank the volume up beyond this point either the protection circuit (which may just be a fuse) kicks in or the amplifier tries to deliver more current than it is designed to.

This can lead to the voltage getting dragged down leading to gross distortion or the power stages start getting very warm and eventually let go.

[chrisjr]

Originally Posted by FlatProblem

Oh dear! So the volume in the kitchen would be quieter than the living room doing it this way? (the reverse would be ideal!)

Thanks for the advice folks!

If you have two speakers in series each one individually will be quieter but that is compensated for by having two. So the overall volume is the same as it would be if you only had one speaker.

All you are doing by wiring two speakers in series is presenting a more acceptable load to the amplifier. So that for any given setting of the volume control it is not being driven beyond its specification.

Whether that makes the kitchen speakers louder or quieter than the living room ones is another matter.

The figure you need here is the efficiency rating. This is usually expressed as a decibel figure for a given power input into the speaker. So if one speaker produces 70dBA for a one watt input it will be twice as loud subjectively as one rated 60dBA per watt.

And there is no reason why the "louder" speaker has to be a higher power rating than the quieter one either. So having a 1000W speaker might not be any louder than a 10W speaker on the same amp.

[streekie]

personnaly i would be more worried about putting a speaker with a paper cone in what could be quite a steamy environment and you wouldnt want them disintergrating into your spaghetti bolognese. in outdoor or wet/humid environments they normally recomend using speakers with mylar cones but i have heard of people lightly coating the paper almost up to the coil with varnish to stiffen the paper and prevent water/steam damage.

[dpmiller]

Plenty car speakers are polyprop cone/ foam surround...

[FlatProblem]

Originally Posted by dpmiller

Plenty car speakers are polyprop cone/ foam surround...

Even the cheap ones seem to be P.P., the ones I am expecting today certainly are

On reflection, I may have been better off getting speakers designed for a boat, water resistant (not that it really gets wet in the kitchen with the extractor fan etc) and more importantly white! (I plan on spray painting the grills white, but it would have saved me a job).

Maybe I'll do that for the bathroom

[streekie]

i seem to recall both screwfix direct and maplin do white speaker grilles in a range of sizes which could save the paint job ?

[FlatProblem]

Originally Posted by streekie

i seem to recall both screwfix direct and maplin do white speaker grilles in a range of sizes which could save the paint job ?

Couldnt see anything in screwfix? I did look at the ones at maplin, but they look pretty naff (look a bit like extractor fans :S); I might use them as a last resort if I ruin the real ones by spraying them.

Thanks for the suggestion!

[dpmiller]

cpc.co.uk do a good range of in-wall, in-ceiling, and marine speakers...

[FlatProblem]

Hi guys,

Just a quick revisit to this.

I've got the speakers and hooked them up as a test before drilling into the celing, however, despite being the ones with the highest sensitivity, there not loud enough

So back to the drawing board, I think the way to go is to take the phono outputs from my amp (in the living room) and feed them into a second amp.

Thats straight forward enough, but the missus doesnt want an amp taking up too much room in the kitchen

I thought about getting a car stereo, but then I'd need a 12v transformer wired into it somehow and it would need to have phono inputs on the back (cheap ones dont seem to have this), and I'd need to build some sort of case for it.

I also found an amplifier that you hide inside the wall (next to your light switch for example), that was £100 and snazzy looking, so I'm guessing there must be something cheaper that will do the job? (just needs a volume control!)

I saw lots of "amplifier kits" on maplins website but I dont really fancy getting the soldering iron out if there is something small I could buy off the shelf?

Any thoughts? Quality isnt really a major issue, its just to drown out the noise of the pan sizzling

[dpmiller]

You are aware that a speaker will be much quieter in free-air than mounted correctly on a baffle?

I'm guessing the amp you're talking about is something like this:

http://cpc.farnell.com/jsp/Audio,+Vi...sp?sku=DP29135

If you really *do* need an amp, a cheaper/ easier option might be to cannibalise one from a cheapo active/ surround setup...

[FlatProblem]

Originally Posted by dpmiller

I'm guessing the amp you're talking about is something like this:

http://cpc.farnell.com/jsp/Audio,+Vi...sp?sku=DP29135

Yup thats the exact one I found