Ohm help please

[6Tones]

My VHT amp internal speaker is 8ohm,and I want to run a 16ohm extension cab with it,the amps selector switch is 4,8,16 ohms, what should I set it too?
Also what if I used a 8ohm extension cab,would I set the ohm selector switch rating to 4?
Thanks in advance!

 

[John Phillips]

If the internal speaker is 8-ohm, and the extension is 16, the total impedance is 5.33 ohms - assuming the sockets are in parallel, which in most amps they are.

This is a safe mismatch from either the 4 or 8 ohm settings (it 'sounds' closer to 4, but actually it's a 33% mismatch from either if you work it out!). Try both and see which sounds better. If you can't tell any difference, it probably doesn't matter at all either way. If I had to pick, I'd probably go for 4 since mismatching fractionally upward is a little less hard on the tubes than downward. Also, it may be worth mentioning that 2/3 of the power will go to the 8-ohm speaker and only 1/3 to the 16-ohm extension cab.

If you're using an 8-ohm extension cab, set the amp to 4, yes. The power is divided equally between the internal and external speakers.

 

[6Tones]

Ok Ill go with the 4ohm setting.
Thanks John!

Originally posted by John Phillips
If the internal speaker is 8-ohm, and the extension is 16, the total impedance is 5.33 ohms - assuming the sockets are in parallel, which in most amps they are.

This is a safe mismatch from either the 4 or 8 ohm settings (it 'sounds' closer to 4, but actually it's a 33% mismatch from either if you work it out!). Try both and see which sounds better. If you can't tell any difference, it probably doesn't matter at all either way. If I had to pick, I'd probably go for 4 since mismatching fractionally upward is a little less hard on the tubes than downward. Also, it may be worth mentioning that 2/3 of the power will go to the 8-ohm speaker and only 1/3 to the 16-ohm extension cab.

If you're using an 8-ohm extension cab, set the amp to 4, yes. The power is divided equally between the internal and external speakers.

 

[J.T.]

Is the 16 ohm cab a 2x12 ? It might be easier to re-wire the 2x12 for 8ohms that paired with the internal 8 ohms will give you 4 ohms total with out a mismatch

 

[6Tones]

Originally posted by J.T.
Is the 16 ohm cab a 2x12 ? It might be easier to re-wire the 2x12 for 8ohms that paired with the internal 8 ohms will give you 4 ohms total with out a mismatch

No its a 1x12 16 ohm extension cab