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How to wire 8 ohm speakers to 4-16 ohm amplifier

Last response: in Home Audio
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March 17, 2011 2:45:14 PM

Hello,
i have a Adastra A120TUD Mixer Amplifier and i need to connect 7 80Watt Max. speaker with 8 ohm. The amplifier have 4 screw in the output panel:
1: com
2: com
3: 4-16 Ohms
4: 100V

i don't know how to connect serial or parallel the 2 line of my speakers... can you explain me?

Thank you
March 18, 2011 9:10:47 PM

the user manual says COM is the negative output
then put the positive wire on the 4-16 ohm tab

the amplifier specifications arent extremely clear, the data given says the amp is 120 watts RMS.. but doesnt say for what impedance.

to be safe, you need a minimum of 32 ohms.
otherwise you need to wire them for a lower impedance and be careful with the volume knob.

if you wire ALL speakers in series = 56 ohms

maybe the amplifier doesnt sound very good when a 56 ohm load is connected.
and in that case, you need to wire THREE speakers in series.. then the other FOUR speakers in series.
....connect those two sets in PARRALLEL for a total of 13.7 ohms

since those speakers are 80 watts each.. that means you need 80 x 7 = 560 watts
the amplifier is 120 watts

you said 80 watts MAX
you need to know if that 80 watts is continuous or only an instant peak.

maybe those speakers are less than 80 watts for all day/night.

you might want to connect less than 7 speakers to the amplifier so that the watts match up much more closely.
but that depends on how good the speakers sound with much less power than maximum.

sometimes using many speakers with much less than maximum power is better than running only a few of the speakers at full power.

one reason is because more speakers = more air moving
another reason is because sometimes speakers sound much better at low volume compared to high volume. (the speaker might play with distortion)

to run those speakers at full 80 watts, you need to run 1.5 speakers (rounding up makes two speakers)

you really need to try all three options and use your ears to see which way sounds the best.

personally, i think hooking up all 7 speakers is more fun.
you can place 7 speakers in different places of the room to make the room fill up with sound.
two speakers wont fill up the room with sound unless you do some sound processing (time alignment and reverb and phase correction)

anyways.. its really hard to make only two speakers sound exactly the same at the opposite end of the room.
its just easier to place two more speakers on the other end of the room.

the major difference between using 2 speakers vs 7 speakers is the amount of pressure in the room.
and this is where the situation gets crazy.. because two speakers might have more force because they have the power to shove the air.
but if all of the speakers are efficient, 7 speakers will shove the air less.. but when you add up all 7 - you might have more pressure (you might have the same amount of pressure.. and you also might have less pressure)

pressure is important for bass.
some people want it, some people dont.
you can have pressure for midrange and treble too.
but again, some people want it and some people dont.
its all about creating pressure or creating a vacuum (or creating a tornado to hide the pressure)

the simple way to remove the pressure is to flip the phase.
but that means the speaker uses the box for 'response'
if the box is not made for it, the result sounds dull and sometimes you can hear an echo inside of the box (known as transients or harmonics.. depending on how thick or hard the box is)

i didnt mean to make things overly complicated..
i just wanted you to know your options.

and its not that hard really.
you try both impedances.
and try all 7 speakers vs. 2 speakers.
then simply change the positive and negative wires on the amplifier to change the phase 180 degrees.

concert speakers are known to sound totally different when you wire them to the amplifier positive to negative instead of positive to positive.

good luck..!
you have a few tricks up your sleeve now.
!