I don't play bass or have a bass amp but is it okay to connect a 4 ohm bass head to a
6 ohms cabinet with 2 parallel jacks.
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if it's SS then no. If it's tube then yes. for tube you can only go up. like 4ohms head into 8ohm speaker/cab. SS is opposite
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Quote by apak
if it's SS then no. If it's tube then yes. for tube you can only go up. like 4ohms head into 8ohm speaker/cab. SS is opposite

My understanding is that the overall speaker impedance can not be lower than amplifier's rating for either the tube or solid state amplifier.

Two speakers in a cabinet may be wired in parallel (lowering the impedance) or in series (increasing the impedance). Larger multiples will usually be series/parallel to maintain an impedance of 4 to 8 ohms. For vacuum tube amplifiers and solid state amplifiers, the overall impedance of the speakers in the cabinet must not be lower than the lower limit of the impedance of the output transformer of the amplifier or damage to the amplifier components can occur through over heating. Conventional wisdom holds that with solid-state amplifiers there is less need to precisely match the impedance of the speaker cabinet to the impedance selected on the amplifier, but as a rule, mismatches are discouraged to avoid either damage to equipment or reduction in usable power from the amplifier.

Source: http://en.wikipedia.org/wiki/Guitar_speaker_cabinet

Yes, I realize that wikipedia is not the ultimate resource of all knowledge, but every other article I found was overly technical.

This only partially addresses the original question, sorry.
If it is a solid state head then you can go as high of impedance as you like. you just can't go below the recommended impedance. You will lose some wattage but it won't hurt anything. Tube heads on the other hand have to have a specific impedance. That's why there's a switch on the back where you choose what impedance you're playing into. There's a resistor or something inside the amp head that adjusts to different impedances so that the tubes and transformer always push the same wattage.

If the amp head has a switch on the back to select impedance I wouldn't go with anything other than the set impedances but I've never seen a switch on a SS head.\

EDIT: Also, tube preamps don't count when we're talking about tube heads. It's the power(output) sections that are important when matching impedances.
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Last edited by Revelation at Mar 29, 2009,
If you go to the columns there is an article on matching speakers to amps which is fairly comprehensive. However the impedence of speakers is nominal (not exact) and varies considerably over the frequency range of the speaker. Go on to the manufacturers websites and they often publish a graph of impedance against frequency. This is all just physics.

The long and short of it is that 6ohms is near enough to 4ohms that you don't need to worry too much, tube or tranny the worst that can happen is losing a little bit of power.

For anyone reading this too high an impedance won't hurt a transistor amp and valve amps tend to burn out their output transformers into high impedances depending on the exact design but won't be damaged by normal impedances (4-16). But you have a matching transformer in a valve amp so why not use it?