Would an 800w amp work with 2 400w cabs at 8 ohms each?

[slightly_basic]

Before I start I'll say I did read the post all about ohms and how they work and how many cabs you can use, I couldn't find anything that made sense to me about my issue. I've been looking at the MarkBass 102P and the 151P amps, each at 400w at 8 ohms. I'm wondering what amp I would need to maximize volume from each cab. Just an example, the Little Mark 800 is rated at 800w for 8 ohms, and 500w for 4. Is that what I would need to get the most volume out of each cab? Am I totally misunderstanding? Any advice is appreciated!

 

[Al Kraft]

First off, here are the correct specs for your head (cut and paste from the Markbass website):

• OUTPUT POWER: 800W RMS @ 4 ohms / 500W RMS @ 8 ohms

Solid state heads almost always produce more (sometimes the same) power as the output impedance drops. So this Markbass head follows a perfectly logical pattern for solid state heads. Heads like this also have limitation on the allowable load impedance they can be safely operated with. Some are limited to 4 Ohms, others can go to as low as say 2 Ohms.

Second, the Markbass 102P and 151P are cabinets (cabs) not amplifiers or amps.

Third, according to Markbass the 102P is available in 4 or 8 Ohm impedance versions, so be sure which you have (or end up getting). The 151P is shown as 8 Ohm impedance only. Both appear to be rated at 400 Watts.

So, the head would be able to deliver 400 Watts to each of the 8 Ohm cabs (as the combined cabs would present a 4 Ohm load to the head). To an individual 8 Ohm cab your head would be able to deliver 500 Watts (I would not panic over that, just be careful how hard you drive a single cab).

The 102P in a 4 Ohm configuration (if you had one, not recommended IMO) operated by itself would be potentially facing 800 Watts from your head. Serious caution would be required there and I would personally not like to run a head and cab together with that much of a mismatch. That 4 Ohm cab paired with the 8 Ohm 151P would also cause your head to try and operate below its 4 Ohm minimum rating...and if the head wasn't constantly shutting down in a protection mode, something would most likely fail internally probably sooner rather than later.

I hope that helps clear things up a bit.

 

[dbase]

An 800 watt amp would see two 8 ohm cabs as a 4 ohm load and deliver 800 watts. Here you go ....

 

[slightly_basic]

First off, here are the correct specs for your head (cut and paste from the Markbass website):

• OUTPUT POWER: 800W RMS @ 4 ohms / 500W RMS @ 8 ohms

Solid state heads almost always produce more (sometimes the same) power as the output impedance drops. So this Markbass head follows a perfectly logical pattern for solid state heads. Heads like this also have limitation on the allowable load impedance they can be safely operated with. Some are limited to 4 Ohms, others can go to as low as say 2 Ohms.

Second, the Markbass 102P and 151P are cabinets (cabs) not amplifiers or amps.

Third, according to Markbass the 102P is available in 4 or 8 Ohm impedance versions, so be sure which you have (or end up getting). The 151P is shown as 8 Ohm impedance only. Both appear to be rated at 400 Watts.

So, the head would be able to deliver 400 Watts to each of the 8 Ohm cabs (as the combined cabs would present a 4 Ohm load to the head). To an individual 8 Ohm cab your head would be able to deliver 500 Watts (I would not panic over that, just be careful how hard you drive a single cab).

The 102P in a 4 Ohm configuration (if you had one, not recommended IMO) operated by itself would be potentially facing 800 Watts from your head. Serious caution would be required there and I would personally not like to run a head and cab together with that much of a mismatch. That 4 Ohm cab paired with the 8 Ohm 151P would also cause your head to try and operate below its 4 Ohm minimum rating...and if the head wasn't constantly shutting down in a protection mode, something would most likely fail internally probably sooner rather than later.

I hope that helps clear things up a bit.

Thanks for the info! Yeah, I knew the cabs weren't amps, I just mistyped. So what you're saying is that as long as I had both cabs in the 8 ohm version, it would work fine and not overload the cabs? Or have I totally misunderstood you?

 

[abarson]

Thanks for the info! Yeah, I knew the cabs weren't amps, I just mistyped. So what you're saying is that as long as I had both cabs in the 8 ohm version, it would work fine and not overload the cabs? Or have I totally misunderstood you?

1 x 8 ohms cabinet = 8 ohms total load: Good!
2 x 8 ohms cabinets = 4 ohms total load: Good!

1 x 8 ohms cabinet + 1 x 4 ohms cabinet = 2.67 ohms total load: Bad!

 

[Al Kraft]

Thanks for the info! Yeah, I knew the cabs weren't amps, I just mistyped. So what you're saying is that as long as I had both cabs in the 8 ohm version, it would work fine and not overload the cabs? Or have I totally misunderstood you?

You are 100% good to go with two 8 Ohm cabs (which will show you amp its minimum allowable load - 4 Ohms) and IMO (being a little careful) you're just fine using that head to play either of the 8 Ohm cabs individually.

Now a final word of caution, if you crank the low EQ to the max and crank the output to the max, don't assume the cabs will be fine. Cabs have two key power ratings. One is thermal (or heat) and that is what is usually given when you only see one rating. The other limitation is a mechanical power rating (which is offered by some manufacturers as well) and it is often lower and especially so at very low frequencies. Some well-designed, higher end cabs will have mechanical and thermal rating very close or the same.

Do not let this keep you up at night, just be aware that even when you match up gear perfectly, you as the operator are still required to use some good judgement during operation. Even an amp with a lower advertised power rating than your cab can overpower a speaker and cause damage. Simply be aware as you play and don't blindly assume that maxing out everything on the amp into a cab with the same rating will always end in a good outcome.

You will hear when you are asking too much of your amp/cab(s) and then it's time to add a cab(s) and perhaps upgrade your amp so you're not running out of headroom. IMO the gear you have selected should work fine.

 

[LuckyScott]

Yep, I do it all the time. And it sounds Amazing......
GK 800 watt amp and two 4 X 10 cabs

 

[Downunderwonder]

Yep, I do it all the time. And it sounds Amazing......
GK 800 watt amp and two 4 X 10 cabs

OP proposal has about half the real world power handling in the cabs though.

There's every chance for a sucessful outcome so long as OP doesn't overpower the cabs with too much low end