loudspeakers- 2 x 8 ohm impedance = total impedance?.- 2x 8 ohm in parallel = total impedance ?

Answer 1

Although both impedance Z and resistance R are expressed in Ohm (Ω), the impedance is slightly different from the resistance as it is a function of the frequency of the signal which affects the phase difference between the current and the voltage.

In audio, the term 'nominal impedance' is losely used and is consiered to be achieved when the load of the speaker is fairely resistive which is the point where the impedance is almost minimal (hence the nominal current almost maximum),

Assuming Z=R
1/Req= (1/R1)+(1/R2)=(R1+R2)/(R1.R2)
Req=(R1.R2)/(R1+R2)
if R1 =R2 then Req=R²/2R=R/2=8/2=4Ω

By connecting two 8Ω speaker in parallel you will divide by two the resistance so the output current of your amplifier will be multiplied by 2. The thing to remember is that the lower the impedance the higher the current pulled from the output of the amplifier so you need to make sure that the amplifier can cope because current also means a lot of heat in your transistors

When using an amplifier, I would always recommend to limit the volume to 3/4 and no more to avoid distortions and putting your amplifier on its knees.

Answer 2

Simply, 2 x 8 ohms in series, total impedance is 16 ohms.
2 x 8 ohms in parallel provides a total impedance of 4 ohms.

Answer 3

Two in series would be 8 + 8 = 16 ohms.
To find two in parallel you must use the formula :
1/R = 1/R1 + 1/R2
so
1/R = 1/8 + 1/8 = 1/4
So R = 4 ohms.

Answer 4

Series 8 Ohm speakers = 16 Ohms
Parallel 8 Ohm speakers = 4 Ohms

Make sure they are in 'phase'.

In parallel, both ground wires connected together, both 'hot' leads in parallel.

In series, wire:speaker1 hot to amp hot, speaker 1 ground to speaker 2 hot, ground 2 to ground amp.

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