ceiling speakers

[petermurphy1]

Hi there.
Can anyone give me advice with ceiling speakers. Where to get them reasonably priced and why do some seem to have transformers in them. I always thought with a speaker all you did was connect 2 wires to the terminals and off you went. To take the output from a tv or a stereo what wattage do I need.

Please help.
Thanks

Pete

 

[Spark123]

The ones with transformers are normally for where you have something like a 110v tannoy system, the sound is pumped from an amp around the system on a 110v line and each speaker (can be a lot of speakers) is connected along its length.
I doubt you will need this sort of speaker, assuming you are doing a domestic job!
The wattage you require depends on how loud you want them and indirectly the output of the amp driving the speaker - too many watts from an amp and you can blow the speaker. You also need to consider the impedance of the speaker and that of the amp (don't think it is as critical now as it used to be, but always nice if the numbers add up!)

 

[breezer]

as spark123 said ideally they should be "matched" to the amplifier.

try google there are lots out there, depends what style you you want and what they are for

 

[Space cat]

1) Solid state amplifiers (nearly all of them these days) have a minimum impedance that they will drive properly. If this is 8 ohms (a common value) you can put an 8 ohm speaker on it. If your amp says it can drive 4 ohms you can still use an 8 ohm speaker - or you could use a 4 ohm speaker or, more likely, two 8 ohm speakers in parallel. If you put a 4 ohm load on an amp only designed for 8 ohms you could damage it.

2) The maximum power output from your TV/stereo is already fixed. As Spark123 points out, your speakers must be able to handle this or you risk blowing them. When I used to build disco equipment, a good rule of thumb was "two watts of speaker for each watt of amp". That's a wise rule if you habitually turn your amp up to the limit and then some! For home use you can relax it a bit but don't use speakers smaller than your amp's power rating.

3) Volume depends not only on power but also on efficiency. Paradoxically, the higher the sound quality of the speakers, the less efficient they tend to be. Efficiency also drops with cone size. For what it's worth, my 15W 8" speakers (in 1.5 cu ft bass reflex boxes) can put out disco level sound in a living room.

4) The enclosure is as important as the speaker. Having them in a ceiling void does not eliminate the need for careful design.

5) For expert advice on all things audio try www.hydrogenaudio.org.

 

[electronicsuk]

2) The maximum power output from your TV/stereo is already fixed. As Spark123 points out, your speakers must be able to handle this or you risk blowing them. When I used to build disco equipment, a good rule of thumb was "two watts of speaker for each watt of amp". That's a wise rule if you habitually turn your amp up to the limit and then some! For home use you can relax it a bit but don't use speakers smaller than your amp's power rating.

Obviously each to their own, but this is completely the opposite of what I've always been taught/heard. My rule of thumb would be to use an amplifier with an RMS output 1.5x higher than the rating of your speakers.

The reason behind this is that a 250w RMS speaker will be able to handle in excess of this rating with typical music material, in fact many speakers will also be marked with a program power rating which is usually around 2 times the RMS. You can google for the specifics if you're interested, but this is all essentially because of the way RMS power for a speaker driver is determined, the test signal has a higher power content than typical music.

By using an underpowered amplifier not only are you not getting the most from your speakers, you also play a far higher risk of damage. If some idiot turns the gains control up to full then there's a good chance the amp will start to clip, you'll probably see a lot of bedroom DJs with red lights flashing on their amp to the bass beat because 'it looks cool'.

Clipping is caused because the amp is working at its limits, the output voltage on the speaker terminals is at or very near the voltage on the supply rails and hence simply cannot rise any further. Where there would normally be a nice output waveform, you have now effectively sliced off the top and bottom halves. The more you go into clipping the worse this will be, until eventually (in purely hypothetical situation) you would be left with just a square wave.

Tweeters, piezo horns and compression drivers do not like square waves, and a clipped amp is usually a pretty fast way to destroy them. So in short, using an underpowered amplifier offers no real protection to your speakers.

 

[Lectrician]

Cable size is also important. Too small a cable results in losses.

 

[gman76]

Far more likely to damage speaker HF units with an under powered amp, due to clipping.

My 2p worth.

 

[Space cat]

Clipping is caused because the amp is working at its limits, the output voltage on the speaker terminals is at or very near the voltage on the supply rails and hence simply cannot rise any further. Where there would normally be a nice output waveform, you have now effectively sliced off the top and bottom halves. The more you go into clipping the worse this will be, until eventually (in purely hypothetical situation) you would be left with just a square wave.

Perfectly true.

Tweeters, piezo horns and compression drivers do not like square waves, and a clipped amp is usually a pretty fast way to destroy them.

I can see the logic in that but ---

If some idiot turns the gains control up to full then there's a good chance the amp will start to clip

Isn't that same idiot just as likely to do this with a bigger amp?

I think your reasoning goes like this:

1) You want lots of volume out of your speakers.

2) Your amp won't give you what you want without clipping.

3) You get a bigger amp and take care NOT to turn it up too high.

Why not get a bigger amp AND bigger speakers?

Cable size is also important. Too small a cable results in losses.

That's why the old 100 volt system was used on very long cables - and also why the National Grid doesn't use 230 volts! You do sometimes see speakers connected up with something resembling undersized bell wire. It's not unusual on cheap audio equipment. Compared to the price of decent speakers, cable is cheap. Don't skimp on it!

 

[In Your Face]

Kef cavity speakers

 

[electronicsuk]

1) You want lots of volume out of your speakers.

2) Your amp won't give you what you want without clipping.

3) You get a bigger amp and take care NOT to turn it up too high.

Why not get a bigger amp AND bigger speakers?

OK, I see your point, but needlessly upgrading the speakers when a slightly more powerful amplifier would do the job seems like a waste of money. Granted that idiot X with a more powerful amplifier is more likely to overheat the voice coils, but the same idiot with a smaller amp will probably damage the HF components of the speakers.

I suppose there is also power compression to consider, as beyond a certain point (especially with cheap drivers) much of that extra power will just be wasted as heat, so the argument depends on exactly what speakers we're using.

I suppose the best compromise is to have a limiter or speaker management unit somewhere in the system, but we're digressing - the OP only wants some speakers to stick in the ceiling of his house!

 

[ban-all-sheds]

Obviously each to their own, but this is completely the opposite of what I've always been taught/heard. My rule of thumb would be to use an amplifier with an RMS output 1.5x higher than the rating of your speakers.

The reason behind this is that a 250w RMS speaker will be able to handle in excess of this rating with typical music material, in fact many speakers will also be marked with a program power rating which is usually around 2 times the RMS. You can google for the specifics if you're interested, but this is all essentially because of the way RMS power for a speaker driver is determined, the test signal has a higher power content than typical

http://www.hifi-writer.com/he/misc/rmspower.htm

 

[petermurphy1]

Hi Guys,
Thanks for your interest but I don't really understand all the tech talk.
All I want to do is to use my pc to store the music files, connected to an amp and played through some ceiling speakers. I dont need disco levels of volume just enough to turn up fairly loud when I have a party. If I said to you would a 60W amp and 35 w speakers be enough or do I need to up that?

Pete

 

[electronicsuk]

Hi Guys,If I said to you would a 60W amp and 35 w speakers be enough or do I need to up that?

I much doubt that there is anyone on this forum that can give an honest yes/no answer that question, let alone with the information you've provided.

There are far too many factors to take into account, such as size and shape of the room, your preferred style of music, sensitivity and frequency response of the speakers, where you choose to mount them - the list goes on.

The only thing I can really suggest is that you buy the parts you're interested in and experiment to see how they sound. You mention the speakers must be 'reasonably priced', to my mind this would mean sub-£50. I would expect the performance of such a pair of speakers to be about equal to a midi system of similar cost, don't expect miracles, and if possible buy from a shop where you can demo beforehand.

 

[GC1971]

When I used to build disco equipment, a good rule of thumb was "two watts of speaker for each watt of amp". That's a wise rule if you habitually turn your amp up to the limit and then some! For home use you can relax it a bit but don't use speakers smaller than your amp's power rating.

Sorry mate; but if that's how you used to design PAs then you must have made some pretty terrible noises..
That rule of thumb flies in the face of every PA I've ever designed, worked on or that you will hear in a pro environment.. these systems operate on pretty much the exact opposite; you want 1.5x the amp power ( at least) to cope with the transients.
The cabinet's rating is pretty useless actually.


3) Volume depends not only on power but also on efficiency. Paradoxically, the higher the sound quality of the speakers, the less efficient they tend to be. Efficiency also drops with cone size. For what it's worth, my 15W 8" speakers (in 1.5 cu ft bass reflex boxes) can put out disco level sound in a living room.

Sorry to knock you again, but No, they don't.... (both the sound quality bit and the disco level bit..)

Back to the OP question; what you need to check is:

How much money do you have?
How many speakers do you need?

You can then work out the total wattage of the system; (add all the speakers up); and how you can wire it up to keep the impedance within the amps range. (tell me what impedance they are and I'll work it out coz i'm nice like that).

 

[ban-all-sheds]

Or you could just go and buy a proper hi-fi system.....