Simple Amp/Cab Ohms questions - Well, simple to you :)

[Mattfig]

Hey guys,

While I've found a million google hits for this, I'm still a little unclear on something and was hoping to score some help from some of you...

I am putting together a killer system that ends with a Randall RT2/50 amp heading into a 4x12 cab...

Two questions...

Since I'm using the left and right input (not using output from cab) on the 4x12 do I match the impedence directly? Meaning do I set each (amp and cab the same) at 8 or 16 or whatever matches? Or do I consider each connection to the cab its own and change the impedence?

Lastly, will my 4x12 only use two speakers for each input? I've never run a stereo amp before and while I'm only really using it mono - I'm confused...

Thanks in advance,
Fig

 

[GuitarGuyLP]

Your cab should have a stereo/mono switch, and would typically be mono 8 ohms, stereo 16 ohms. Make sure that switch is set to Stereo, and that the impedance of your power amp is set to match. Each side of the power amps will be running two speakers, that is what gives you the stereo effect. If you post the make/model of the cab I can give you a bit more info.

 

[Ancient Alien]

If your cabinet is a mono/stereo cabinet, you match the impedance.
If the cabinet is 16 Ohms mono, each 2 speaker sets will be 8 Ohms, and you set the power amp to 8 Ohms per side.
Just make sure that your cabinet is not a single mono cabinet with a through.
If it is, you can simply re-wire it for a pair of speakers per jack.

 

[Ancient Alien]

Your cab should have a stereo/mono switch, and would typically be mono 8 ohms, stereo 16 ohms. Make sure that switch is set to Stereo, and that the impedance of your power amp is set to match. Each side of the power amps will be running two speakers, that is what gives you the stereo effect. If you post the make/model of the cab I can give you a bit more info.

You got the Ohms backwards.

 

[GuitarGuyLP]

4 8 ohm speakers in a series parallel config makes 8 ohms. Then the stereo will be running two speakers which are usually in stereo at 16 ohms. But can also be configured to run at 4 ohms a side depending on how it is wired.

4 16 ohm speakers will give you 16 mono, and 8 stereo.

It all depends on what the impedance of the speakers is.

 

[Mattfig]

Thanks guys...Just to clarify a bit...My cab has a left and right input (which will each be connected to their respective output on my poweramp...The cab itself is capable of 8ohms stereo and 4 or 16 ohms mono...With the left and the right connected, is there a way to connect the power amp to the cab to run both left and/or right together - in other words use all 4 speakers for both settings? I'm not looking for true stereo operation, my power amp can switch between 6L6 and EL34s and that's why I'm using both outputs...Speaker impedence is 16ohm Celestion V30s (16 ohm I think)...

So what would you recommend I do at this point?

Thanks!!!

 

[GuitarGuyLP]

I have actually wondered the same thing about the channel switching in the RT2-50. You might want to ask over in the Egnater section of Rig-Talk since Bruce Egnater designed it for Randall, and some guys over there have that same power amp.

 

[Mattfig]

Good call....WIll do that...

 

[Mattfig]

Your cab should have a stereo/mono switch, and would typically be mono 8 ohms, stereo 16 ohms. Make sure that switch is set to Stereo, and that the impedance of your power amp is set to match. Each side of the power amps will be running two speakers, that is what gives you the stereo effect. If you post the make/model of the cab I can give you a bit more info.

You got the Ohms backwards.

16 Ohm speakers FYI...Thanks!

 

[Ancient Alien]

Your cab should have a stereo/mono switch, and would typically be mono 8 ohms, stereo 16 ohms. Make sure that switch is set to Stereo, and that the impedance of your power amp is set to match. Each side of the power amps will be running two speakers, that is what gives you the stereo effect. If you post the make/model of the cab I can give you a bit more info.

You got the Ohms backwards.

16 Ohm speakers FYI...Thanks!

 

[GuitarGuyLP]

Your cab should have a stereo/mono switch, and would typically be mono 8 ohms, stereo 16 ohms. Make sure that switch is set to Stereo, and that the impedance of your power amp is set to match. Each side of the power amps will be running two speakers, that is what gives you the stereo effect. If you post the make/model of the cab I can give you a bit more info.

You got the Ohms backwards.

Only if the speakers are 16 ohms, which as it turns out they are. For 8 ohm speakers I was right.

 

[Mattfig]

So then I select 4ohms and the cab to match? Or 16 ohms on each? Which is preferred?

Thanks!