110 volt PA systems

[Steve]

I need a gizmo that will effectively control volume of 4 speakers in a PA system. The speakers are all 110 volt type with transformers.

The reason I cant use the amp's volume knob is that i need speakers elsewhere to be much louder, but cannot raise the volume of these 4 speakers. Single output amp.

Is anything available that can do this?

 

[Spark123]

Change the tappings on the transformers if poss? Is it viable to install a potentiometer between the transformer and speaker on the ones you want to be quieter and up the main amp output?

 

[bernardgreen]

[1] Quick fix

If the reduction in volume needed is quite a lot try wiring two speakers in series across the "110 volt" feed. This effectively give "55 volts" to each speaker and the volume drops to about 1/4 of the previous volume but is only "sounds" like about half volume.


[2] The best method is to tap change on the output side of each transformer at the loudspeaker or a potentiometer between transformer and speaker.

 

[Steve]

So theres no way to install a variable resistor or anything between the amp and the transformers? I was hoping for something i could put in the office where the wire emerges from the amp.

I had a gander inside the two I need to be louder, and was amazed at the sound difference when they are off the wall. Very tinny! The type that hook over a piece of MDF screwed to the wall and have no back.

Why do they use transformers? Is it something to do with voltage drop?

 

[Spark123]

Not between the amp and transformers!!
I meant between the transformers and speakers at each unit. I think the purpose of it is do do with volt drop but not 100% sure. Have you looked at the ones you want turned up? Do they have different wattage taps on the transformers? Otherwise if you are needing 2 volume levels you might need to use a separate amp for the louder speakers.

 

[bernardgreen]

Why do they use transformers? Is it something to do with voltage drop?

It is the same principle as is used to distribute power.

If 230 volts was used all the way from power station to houses the losses would be more than actual used in the houses. So 132,000 volts with is used for the long hauls as one kilowatt at 132,000 volts is 0.0076 amps to transmit compared to 4.35 amps at 230 volts so far less resistance heating losses in the network.

 

[RF Lighting]

Also using a higher voltage allows the use of smaller (and therefore cheaper) cables.


Crafty, would this be any good?

 

[Steve]

Also using a higher voltage allows the use of smaller (and therefore cheaper) cables.


Crafty, would this be any good?

um . . a 5 amp MCB?

 

[RF Lighting]

http://www.canford.co.uk/commerce/categorybrowse.aspx?TreePosId=2002065

 

[Lectrician]

Would be easier to get a smaller 100v amp for just those speakers - seperate volume guaranteed. Also seperate tone etc.

Just common the inputs, or use the slave out/in if present.





Another way - Two 100v line transformers - one to transform down, then potentiometer - then transform back up to feed the string of speakers. I am fairly confident this would work.