The 8 ohm tap produces a higher voltage (for a given input signal level), and will therefore sound louder. Loudness does not imply a better match. However, this higher voltage comes at the cost of reduced current capability, so the maximum power capability will be less if the load is not matched to the amp's output.
If the speakers are 6 ohms average I guess it makes sense to use either 4 or 8. As Shadorne suggests, pick the one you like, and don't worry about it.
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If the speakers are 6 ohms average I guess it makes sense to use either 4 or 8. As Shadorne suggests, pick the one you like, and don't worry about it.
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