Quick loudspeaker quistion series parallel

[SimonTHK]

I have two loudspeakers at 6 ohm each, my amplifier can go to a minimum of 4 ohm. But I want to use these two loudspeakers in a parallel system on a single output (since it is allready setup like this with 100 meter long cables).
That setup would give me 3 ohm on the setup.
My quistion is, can I just add another 3 ohm resistor in series with my setup? To increase the total resistance to 6 ohm.
I am able to buy a 60 watt resistor for 15 euro so it aint that bad and should be enough.

 

[SimonTHK]

And what if I measure the resistance through the cable, and it shows me like 3 ohm xD (since I have very long cables for some outdoor use), would that resistance maybe be enough?

 

[Diver300]

You only need 1 Ω in series. Two 6 Ω speakers in parallel is 3 Ω, so you only need 1 Ω in series with that to make it up to 4 Ω.

 

[Diver300]

If you know the cable resistance, that contributes to the resistance that the amplifier sees.

 

[SimonTHK]

so if I try and measure the cable resistance, this could maybe just be enough? Just have to be more than one ohm. Cause I might actually need a very big resistor at 120 watt, and that cost a fortune.

 

[Nigel Goodwin]

I would suggest you simply connect the speakers in series - and see how that works. The overly long leads will be adding significant resistance loss anyway, and putting them in series will reduce the losses in the cable.

However, for such extreme cable lengths you should use 100V line rather than low impedance speakers.

 

[WTP Pepper]

I don't think that 3 ohm will damage the amp. Especially with such a long distance in cabling. I agree with Nigel, such a PA system should be using 100v line to reduce losses. Note 100v line is merely a term of reference. I have measured >400V peak on such systems on full steam.

Get a pair of hefty mains transformers e.g. 240-12 and step up at the amp and step down at the speakers. It reduces the i^2 * R losses. Just like the National Grid that uses several hundred KV with step up at the power station and step down at the sub station.

Make sure the amp is off when wiring as it can give you a fairly nasty nip on the fingers if audio is present.

 

[Nigel Goodwin]

Except don't get mains transformers, which will sound crap - get proper audio 100V line transformers.