Changing cab impedance

[nos]

The bass player in my band wants to try a different impedance rating in his bass cab. It is a single speaker rated at 8 ohms. The head he bought from me sounded really good through my 4 ohm cab but I sold it to someone else. He wants the 4 ohms without buying another cab.

 

So here's what I want to do: I want to simulate adding another speaker to the cab by putting 8 ohms of 200W wire-wrapped resistors in parallel with the existing speaker. I'd put it in an external box with heatsinks.

 

Do you think this would accomplish what we're looking for? Any idea how it would affect tone?

[mrbrown49]

Just get a 4ohm speaker.

[crapo]

Yep, get a new speaker. Your converting your amp power into heat through that resister, not getting a louder sound. The 4ohm cab may have sounded better becuase it was louder (amoungst any other reasons).

 

Also the 200w resister may be rated at 200 watts if properly heatsinked (heatsunk??), maybe needing a fan or something to keep the heat down. I'd go for a new speaker cone - loook for the same type that was in your old cabinet if you liked the tone.

 

The tone was probably your old cabinet, not the 4 ohm impedance

[el_tonto]

The amp driving a 4-ohm load will have lower damping than when it drives an 8-ohm load. Rather than lowering the load impedance that the amp "sees", why not increase the source impedance that the speaker "sees"? That will lower the damping too, and won't smell like burning resistors.

 

There's a lot of factors involved, and frankly parallelling a purely-resistive load with the speaker won't at all make it "look" like any 4-ohm speaker, especially not the specific one you used to have.

[isaac42]

What they said.

 

Cabinet impedance by itself makes very little difference in anything. There's a measurable difference in power, but not usually an audible one. By far the largest difference in how different cabinets sound is frequency response, which has nothing to do with nominal impedance.

[nos]

Thanks for the advice, people. I'm overcomplicating it, I guess. I'll advise him to buy another speaker.

 

Man I shoulda made sure he got that Ampeg cab instead of selling it to someone else. It sure sounded magical. It was 4x12 and very rare. He'd be hard pressed to find another one.