Can I run an 8ohm cabinet if my head has a 4ohm output? And why are Ohms important?

Question

What about 16ohm cabs? Can anyone shed some light on this? What about useing TWO cabinets of equal ohms? ARRRRGGGGH!!!!!

Answer 1

Probably-

A 4-ohm head will transfer maximum output to the speakers if the speaker impedance is 4 ohms. In general, you should be able to safely drive speakers if their impedance is between 50 and 200% of the head's output impedance, but the output level will not be quite maximum if at either limit. Recommend consulting the docs on your head.

Some heads, especially tube heads, have taps on their output transformer that will let you match impedance. Again, consult the docs.

If you have 2 cabs of 8 ohms each, when they are in parallel they will be 4 ohms, thus matching your head. Likewise, 4 16-ohm heads in parallel will appear as 4 ohms to the head. feel free to email me if not clear or for more info.

PS- Hey, thanks Johnny-

Answer 2

I am familiar with this question in guitar amplifiers and speaker cabinets. For optimal performance, the output from the transformer should match the net speaker impedance, e.g., 8 ohms to 8 ohms. The general rule is that you can go *one* level higher on the speaker load safely, but with some deterioration in perfromance. So a 16 ohm cab is OK with an 8 ohm output. However, going the other way, with a 4 ohm cab on an 8 ohm output may lead to damage of the transformer

Remember that speaker ohms add up ilke resistors in series or parallel. So, two 16 ohm cabs in parallel are 8 ohms, and four 16 ohm cabs in parallel are 4 ohms.

Answer 3

Listen to Gary, he has it right on.

Answer 4

No clue what you are talking about, and I'm guessing no one esle does.