Speaker Selection.

[premkumar9]

That you can understand by looking on to the picture I have attached. Disconnecting one from a series connected speakers will disconnect the others also.
The amplifier will have certain load impedance. Simply disconnecting will affect the effective load. Adding resistance in place of that is not a good method because a speaker is not actually a resistance, but an inductive load.
If you really want a switch for each speaker, there's no other way I think unless otherwise you have separate channel for each speaker!

What I meant was that if the speakers are connected in parallel (not series parallel combination), then disconnecting one speaker may not create any problem. Is it not?

 

[transistor495]

The amplifier will have certain load impedance. Simply disconnecting will affect the effective load. Adding resistance in place of that is not a good method because a speaker is not actually a resistance, but an inductive load.

Same answer
Suppose you are connecting four 8Ω speakers in parallel. Formula is:
1/R=1/R1+1/R2+1/R3+1/R4
ie,1/R=1/8+1/8+1/8+1/8 = 2Ω in place of required 8Ω for the amp.
Removing the speaker from a parallel connection will increase the total resistance, just reverse in case of series connection. Got it?
So adding more number of speakers parallely may appear as a short circuit for the amp and burn it!

 

[Diver300]

The problem if you connect lots of speakers in parallel is that the impedance gets very low when they are all on. The result is that you won't be able to find a suitable amplifier and the cable will need to be very big.

I think that a simple resistor instead of each speaker will be close enough to the speaker impedance.

The problem with that is that you will get clicks on all speakers as any one switches, and a broken speaker or switch would stop several speakers working.

A traditional solution is to use a 100V amplifier, and then have a transformer for each speaker. You can turn each speaker on and off without stopping the others. The transformer primaries are all in parallel. The impedance stays high so currents are low and cables are not too big. PA (Public Address) amplifiers are designed for this.

Here is a typical transformer:-

Oxford Electrical Products | Transformers | Transformers | Audio Transformer | PCB and Chassis Mounting

 

[premkumar9]

Same answer
Suppose you are connecting four 8Ω speakers in parallel. Formula is:
1/R=1/R1+1/R2+1/R3+1/R4
ie,1/R=1/8+1/8+1/8+1/8 = 2Ω in place of required 8Ω for the amp.
Removing the speaker from a parallel connection will increase the total resistance, just reverse in case of series connection. Got it?
So adding more number of speakers parallely may appear as a short circuit for the amp and burn it!

I asked about disconnecting a speaker without substituting it with a resistor. That will only reduce the load (reduce load current). It should not cause any problem. Right?

 

[transistor495]

That's what I told dude
Without a resistor, simply disconnecting a parallel connected speaker will increase the effective load. Result is degraded sound.
Also you cannot simply go for a parallel connection for your requirement.
Look at the picture I have attached. That's the way you have to go. Anyhow you have to get a total of 4-8ohm speaker impedance for an 8ohm amplifier load. Calculate it according to that.
As Diver300 told impedance matching transformers are the alternative way. They are usually used for PA systems.
That will be horrible for your requirement I think.

 

[audioguru]

Are all 30 people watching the same TV show?

 

[premkumar9]

Are all 30 people watching the same TV show?

Yes. A big one mounted on wall.