I am attempting to build a small distributed sound system form parts I have on hand. I have a mono utility amp that has both 70v output, a 4Ω output, and an 8Ω output.I have 6 ceiling speakers that are 8Ω. I know it would be best to have a transformer at each speaker but but that is not an option for this el-cheapo build. Help me under stand the best way to wire this system with the equipment that I have. The runs from the amp are not very long.

I know connecting a load lower than what the amp is rated for is very bad for the amp. So wiring these six speakers in parallel is out of the question that would see about 1.3Ω

As I understand it if I wire the speakers in a series the amp will see a load of 48Ω

and if I use a series/parallel wiring configuration the amp will see a load of 8Ω


I know the parallel configuration is out of the question. It appears that both the series and the series/parallel configuration are safe but which one is a better choice? I understand the end result of the series wiring vs the parallel wiring is that with the series the volume per speaker will be lower compared to the parallel configuration What would be the effective result of the series/parallel configuration.

I also understand that with the series configuration that attenuation at any speaker isn't possible. I'm OK with that but what would the effect be if I attempted to attenuate a single speaker in the series/parallel config?

Any help would be greatly appreciated.

Thanks,
Josh

 

The series-parallel configuration will give a lower sound per speaker than if you had just one speaker but it is the only way to give the proper impedance to the amp without transformers.

If you adjust a single speaker volume it will affect the volume of the other speakers in series. To adjust the speaker volume individually you could use impedance matching volume controls. They allow you to connect all the speakers in parallel since they have a built-in transformer with selectable taps to obtain the proper impedance.

 

Connecting speakers in series destroys the excellent damping of their resonances by the direct connection to a modern amplifier that has an extremely low output impedance but might be fine for speech. Low frequencies will sound "boomy" at the resonance frequency of the speakers.

It is simple to calculate the output power of series or parallel speakers.

 

The system would be for some background music and possibly voice.

I'm curious how pronounced the effect that Audioguru mentions would be and if the series/parallel configuration would make any difference in sound quality compared to a straight series configuration.

 

Series speakers have a boomy sound quality that is used with some electric guitars.
The frequency of the "boom" depends on the size of the speakers. The amount of boom depends on the design of the speaker and its enclosure. It is noticed on a hi-fi but might be fine for this el-cheapo PA system.

 

Thanks for the info. Off I go to experiment