Two amps running in stereo.

[4001]

So, I was talking to someone today about my soon to arrive, brand new GK 700RB II heads.
They are 480W each. I was asked if I'm running them together in a stereo rig, should I consider the amps together as a 960W system?
I'm only using one cab for each head.

I was perplexed at the answer of that question.

I have no idea. Anyone else?

[TrevorOfDoom]

why are you using this configuration? one head per cab? i'm confused.
i'm not knocking it, but i'm curious the logic behind the decision.

and for the record, to use them both would be, in most folks minds, stereo.

[4001]

Originally Posted by TrevorOfDoom

why are you using this configuration? one head per cab? i'm confused.
i'm not knocking it, but i'm curious the logic behind the decision.

and for the record, to use them both would be, in most folks minds, stereo.

My basses are wired for true stereo. Rickenbacker and Fender Jazz bass....
One amp per pickup. Ultimate tone control.

[TrevorOfDoom]

fair enough.

now back to your question... uhhh, what was the question?

[4001]

Originally Posted by TrevorOfDoom

fair enough.

now back to your question... uhhh, what was the question?

Do I add the power of the two heads and call it a 960 watt system or just two 480 W heads running at the same time??

[AwkwardLoudness]

Originally Posted by 4001

...should I consider the amps together as a 960W system?

In a word, yes. But, the power handling, driver excursion (Xmax), and efficiency of each cab are more important for maximizing the volume ceiling. If each cab farts out or reaches max volume at 250 watts, for example, then any power above that matter. If the speakers are inefficient, then the power is not being utilized to potential, although sometimes that is desired especially in tube amps that only reach tube saturation (the sweet spot) at loud volume (not applicable to a 700RB).

[4001]

So, how do you measure where the amp's power is at at any given volume setting?
How would I know if, say the amp is at 250W when/if the speakers are starting to "fart out"?

Wow. I guess I have to be a rocket scientist to be a bass player.

[AwkwardLoudness]

So, how do you measure where the amp's power is at at any given volume setting?

One could bench test an amp's power using a sturdy multi-meter, but I don't recommend it unless you take the proper safety pre-cautions and know what you're doing.

Generally speaking, an amp has reached it's RMS rated power when cleans start to distort in the power section. One can sort of estimate the output power below that point using a dB meter and knowing the relationship between power and volume. Volume decreases 3 dB when power is halved (all other factors being equal, of course).

How would I know if, say the amp is at 250W when/if the speakers are starting to "fart out"?

Output power (watts) is not the only factor. The EQing of the low end frequencies is the other major factor in this as far as the amp is concerned. Many more variables come into play with the cabs: speaker magnet maximum excursion, speaker frequency range, cab design, etc.

[JimmyM]

let me make it simple for you...use your ears. if your cab starts to fart out, it's not important that you know where the wattage is. just turn it down till it stops.

[4001]

So I guess system total power is a 'potential' power.


It's basically a 960 watt system (two 480 watt heads) ON PAPER.

So, when someone says " I have a ____-watt amp, it's what it's potential is?

I DO have to get a degree to understand this. Bwaaaah!

Jimmy, I hear you about using my ears. I always do that anyway.
I was telling someone about the amps and the question came up about if there's two 480 watt heads is it a 960 watt system and I said , "You know, I don't know. I guess, technically it is because that is the power listed."
Not that I'm trying to kill everyone around me and I'll never be cranking it just to try anyways, I was just curious as to how this is figured.

Who cares anyway I guess. if it sounds good, you're good to go.

[christw]

Originally Posted by 4001

So I guess system total power is a 'potential' power.


It's basically a 960 watt system (two 480 watt heads) ON PAPER.

So, when someone says " I have a ____-watt amp, it's what it's potential is?

I DO have to get a degree to understand this. Bwaaaah!

Jimmy, I hear you about using my ears. I always do that anyway.
I was telling someone about the amps and the question came up about if there's two 480 watt heads is it a 960 watt system and I said , "You know, I don't know. I guess, technically it is because that is the power listed."
Not that I'm trying to kill everyone around me and I'll never be cranking it just to try anyways, I was just curious as to how this is figured.

Who cares anyway I guess. if it sounds good, you're good to go.

480 watts is what the 700RB's maximum clean RMS power rating is. (Usually specified around 5% total harmonic distortion.) That's what amp's power ratings refer to.

[4001]

Originally Posted by christw

480 watts is what the 700RB's maximum clean RMS power rating is. (Usually specified around 5% total harmonic distortion.) That's what amp's power ratings refer to.

Right. To the point where it starts clipping.

Right?

[christw]

Approximately. The THD spec varies by manufacturer so some amps still have more steam while others might be red lined by the time they hit their rating. Just keeps getting more complicated, doesn't it?

[lbwdog]

So far, nobody has mentioned what the cab's impedances are.
Each 700 RBII will put out 320w into 8 Ohms or 480w into 4 Ohms.

Like Jimmy said, there's no practical way to know what the amp is outputting at any given moment when on stage. Wattage is continuously varying depending on frequency and impedance (which varies as well).

Just use your ears and back off the volume when you hear the speakers starting to complain. I will say that the 700 is a very powerful head so be careful!

[4001]

Originally Posted by lbwdog

So far, nobody has mentioned what the cab's impedances are.
Each 700 RBII will put out 320w into 8 Ohms or 480w into 4 Ohms.

Like Jimmy said, there's no practical way to know what the amp is outputting at any given moment when on stage. Wattage is continuously varying depending on frequency and impedance (which varies as well).

Just use your ears and back off the volume when you hear the speakers starting to complain. I will say that the 700 is a very powerful head so be careful!

The cabs are two Acoustic model 106 2X15 cabs rated at 4 ohms.

[4001]

Originally Posted by lbwdog

I will say that the 700 is a very powerful head so be careful!

I can only imagine what the 1001 RB is like.
Overkill?

[hachi kid]

as far as the original question. if each head has it's own separate cab, it's just two 480w heads running at the same time. I do the same thing.

[4001]

Originally Posted by christw

Approximately. The THD spec varies by manufacturer so some amps still have more steam while others might be red lined by the time they hit their rating. Just keeps getting more complicated, doesn't it?

Well, like a car that has let's say 400 HP.
It's not using that 400 HP at a red light.
(Although you can hear it just waiting to be unleashed)

[4001]

Originally Posted by hachi kid

as far as the original question. if each head has it's own separate cab, it's just two 480w heads running at the same time. I do the same thing.

I was thinking along those lines as well.
It only makes sense.

[christw]

Originally Posted by 4001

Well, like a car that has let's say 400 HP.
It's not using that 400 HP at a red light.
(Although you can hear it just waiting to be unleashed)

I like that analogy.

Originally Posted by 4001

I can only imagine what the 1001 RB is like.
Overkill?

It's like having one of those huge turbo diesel trucks. 99% of the time you aren't using it to close to it's potential but when you have to you're thankful that you can.