Using Two or More Cabs, Is Wattage Cumulative/Additive?

[selowitch]

Kind of a dumb question, but if I am using two bass cabinets simultaneously with one head, do I add the wattage of each together to arrive at the total wattage the pair can handle? For example, if each cabinet is rated for 300 watts, can the two together handle a total of 600 watts from the head?

 

[Kro]

You got it, add them together.

But keep in mind the amp will send the power equally to both if they both have the same impedence (8ohm and 8ohm for instance).

Power ratings for a combination are only as strong as the weakest link.

So using a 500w amp with one 400w cab and one 100w cab would not mean it can handle 500w from a power handling/ratings standpoint.

There are lots of complicating variables, not the least of which are the ratings themselves, but suffice to say the 100w cab might not be happy in that arrangement.

 

[rickdog]

And, remember that impedance depends on frequency. Power will be distributed equally to both cabinets at all frequencies only if they are identical. If you mix cabinets, at some frequencies most of the power might go to just one.

 

[selowitch]

It seems like this would be especially important for relatively low-wattage cabinets like the Phil Jones C2 I have my eye on. It's rated at 200w, so if use two C2s that would bring me to 400w. I believe they run at 8ohms, so a 200-watt amp would put out perhaps 350watts into those two cabinets, which seems like a good setup to me.

 

[two fingers]

Not really. Let's say you have a 600W amp.

In essence, each cab it still living up to its own rating. The power from the amp is divided equally (assuming identical ohm ratings) between the two cabs. So two 300W cabs would each he getting 300W from the head (max).

But....

If you have a 500w cab and a 100W cab (assuming ohm ratings are identical) you are still sending (max) 300W to each cab. In that respect, no, the output rating of the cab system is not "added". You're going to fry that 100W cab. It isn't a "600W speaker system". It's technically a 200W system due to the limitations of the 100W cab. You shouldn't send any more than 200W down the line.....100W to each cab. In other words, the speaker system will only take whatever the lowest rated cab can handle X2 since power is ÷2 with half going to each cab.


(This is all thermal and theoretical. You can still blow a 100W speaker with a 100W amp.)

 

[selowitch]

My plan is to use two cabinets of the same wattage rating.

 

[jnewmark]

It seems like this would be especially important for relatively low-wattage cabinets like the Phil Jones C2 I have my eye on. It's rated at 200w, so if use two C2s that would bring me to 400w. I believe they run at 8ohms, so a 200-watt amp would put out perhaps 350watts into those two cabinets, which seems like a good setup to me.

A 200 watt amp in to what ohm rating ? If its rated at 200 watts in to 4 ohms, your two 8 ohm cabs, run parallel, would be a 4 ohm load, which would be 100 watts per cab.

 

[Al Kraft]

It seems like this would be especially important for relatively low-wattage cabinets like the Phil Jones C2 I have my eye on. It's rated at 200w, so if use two C2s that would bring me to 400w. I believe they run at 8ohms, so a 200-watt amp would put out perhaps 350watts into those two cabinets, which seems like a good setup to me.

This is sound logic and should work fine. Two 8 ohm 200 Watt cabs in parallel (resulting in a 4 Ohm load being seen by the amp) would have each cab getting 175 Watts from a head that has a 350 Watt output at 4 Ohms.

 

[jnewmark]

This is sound logic and should work fine. Two 8 ohm 200 Watt cabs in parallel (resulting in a 4 Ohm load being seen by the amp) would have each cab getting 175 Watts from a head that has a 350 Watt output at 4 Ohms.

He said the amp is rated at 200 watts. How does that get to a 350 watt output ? ( see my post above )

 

[selowitch]

He said the amp is rated at 200 watts. How does that get to a 350 watt output ? ( see my post above )

That's a theoretical amp I don't own yet. I was thinking it would provide 200w at 4ohms and 350w at 8ohms. My Markbass amps work that way, don't they?

 

[jnewmark]

That's a theoretical amp I don't own yet. I was thinking it would provide 200w at 4ohms and 350w at 8ohms. My Markbass amps work that way, don't they?

More like 200 watts at 4 ohms, somewhat less than that at 8 ohms. For example, the Little Mark III is rated at 500 watts at 4 ohms, 300 watts at 8 ohms.

 

[selowitch]

Well, taking my Markbass Minimark 602 as an example, its power output is 250W RMS @ 4ohms, 150W RMS @8 ohms. So it operates at 8ohms when just using the internal speakers for 150 watts, but if you add a second 8-ohm cabinet that's a 4-ohm load so the output jumps to 250 watts ... or do I have that wrong? This is not my area of expertise. :-|

 

[jnewmark]

Well, taking my Markbass Minimark 602 as an example, its power output is 250W RMS @ 4ohms, 150W RMS @8 ohms. So it operates at 8ohms when just using the internal speakers for 150 watts, but if you add a second 8-ohm cabinet that's a 4-ohm load so the output jumps to 250 watts ... or do I have that wrong? This is not my area of expertise. :-|

yes, 250 watts in to TWO cabs, each one getting 125 watts.

 

[pie_man_25]

That's a theoretical amp I don't own yet. I was thinking it would provide 200w at 4ohms and 350w at 8ohms. My Markbass amps work that way, don't they?

What others are saying about cabs is right - two identical cabs basically doubles your power handling, and if they're daisy-chained in parallel (honestly so common nowadays that it's almost a given) your impedance will drop by half.

As for how much power your head would put out at that impedance, I would find the manual for the exact head that I'm using and refer to that. My last bass head was 250 watts at 4ohms, and 125 at 8 - my current one is 500 watts at 4 ohms, 300 at 8. Your head would likely put out more wattage at 4 ohms than at 8 ohms, unless it's a tube amp which puts out the same wattage assuming you're using the proper tap on your output transformer. I don't think there's anything about a Markbass head that would put out more wattage at 8 ohms than at 4, but I'm not working at Markbass.

This stuff can sometimes be confusing and model-specific sometimes - kinda like cars. I had a dude lecture me about how I should check my car's hydraulic power steering reservoir and the timing belt for a power steering issue - even though MY car used a timing chain and had electronic power steering. In the same vein - I could tell you generalities, but I could easily be wrong and if you e-mail the manufacturer's help desk OR read a manual that's just about the only way to be %100 certain.

 

[Al Kraft]

He said the amp is rated at 200 watts. How does that get to a 350 watt output ? ( see my post above )

He said the amp is rated at 200 watts. How does that get to a 350 watt output ? ( see my post above )

I was replying to this part of one of the OP's posts: "...so a 200-watt amp would put out perhaps 350watts into those two cabinets, which seems like a good setup to me." I assumed (not always a good idea) he was referring to a head that could deliver 200 Watts into 8 Ohms and 350 into 4 Ohms.

I may have misunderstood...and it wouldn't be my first time.

 

[JeezyMcNuggles]

Kind of a dumb question, but if I am using two bass cabinets simultaneously with one head, do I add the wattage of each together to arrive at the total wattage the pair can handle? For example, if each cabinet is rated for 300 watts, can the two together handle a total of 600 watts from the head?

Yes. They also only get half the wattage of your amp each.

 

[JeezyMcNuggles]

That's a theoretical amp I don't own yet. I was thinking it would provide 200w at 4ohms and 350w at 8ohms. My Markbass amps work that way, don't they?

Nope. It's about 2/3 of the power every time ohms number doubles. So, it's about 150 ish at 8 ohm if it 200 at 4.

 

[Passinwind]

As for how much power your head would put out at that impedance, I would find the manual for the exact head that I'm using and refer to that. My last bass head was 250 watts at 4ohms, and 125 at 8 - my current one is 500 watts at 4 ohms, 300 at 8. Your head would likely put out more wattage at 4 ohms than at 8 ohms, unless it's a tube amp which puts out the same wattage assuming you're using the proper tap on your output transformer. I don't think there's anything about a Markbass head that would put out more wattage at 8 ohms than at 4, but I'm not working at Markbass.

This stuff can sometimes be confusing and model-specific sometimes - kinda like cars. I had a dude lecture me about how I should check my car's hydraulic power steering reservoir and the timing belt for a power steering issue - even though MY car used a timing chain and had electronic power steering. In the same vein - I could tell you generalities, but I could easily be wrong and if you e-mail the manufacturer's help desk OR read a manual that's just about the only way to be %100 certain.

Yep. Modern Class D and/or SMPS amps often get much closer to the theroretical doubling or halving of output with doubling or halving of load impedance than many old school designs.

 

[Rip Van Dan]

Kind of a dumb question, but if I am using two bass cabinets simultaneously with one head, do I add the wattage of each together to arrive at the total wattage the pair can handle? For example, if each cabinet is rated for 300 watts, can the two together handle a total of 600 watts from the head?

Yes, just remember that as long as the ohms rating of the cabinets are the same, the power that comes out of your amp will be evenly split between them. This can be a problem if you have cabs that have significantly different power handling capability.

For instance say you have a 210 cab that will handle 200-watts rms and a 410 cab that ill handle 400 watts. If you're driving those cabs with your 600-watt amp and you're pushing to max, it will send 300-watts to each cab. That's fine for the 410 cab because it can handle up to 400-watts, but can blow the speakers in the 210 because it can only handle 200-watts and you're sending 300-watts to it. But if you're using 2 cabs that have the same power-handling ratings, it should be no problem to add those two power-handling ratings up and use an amp of that will provide that total wattage rating.

In some cases, mine for instance, you can use an amp that will be able to send more power than they can handle if you don't run it at max. But you really need to pay attention and listen to what your are playing. With most amps, the master control is the "watts sent" control. I used my 800-watt amp to drive two 112 cabs that could handle 300-watts rms each. I plugged one into each channel of my dual-powerblock amp and it "could" feed those cabs as much as 400-watts each, which is 100-watts more than they can handle and would blow them. But I never got anywhere close to that power level because I didn't need anywhere near that much power to drive them to gig level in medium-sized venues where I used it.

I've since replaced those with my DNS210 cab which will handle 700-watts rms and I run my amp bridged with 800-watts "available" into 8 ohms. Just because that much power is available, doesn't mean that's how much I'm using. That cab will put out a max SPL of 134db with 700-watts and that's well above the threshold of pain. I typically run my master on my 800-watt amp at 10 o'clock on large indoor venues and 9 o'clock to 9:30 everywhere else indoors. So I'm not coming anywhere close to the max my amp will put out.

The one caveat you really have to bear in mind though when you have an amp that is capable of blowing the speakers you're using though, is how hard are you driving that amp. Will your speakers give you gig-level sound with a lower power setting or will you be tempted to keep turning it up to keep up with the rest of the band (guitarists are usually the ones who exacerbate this situation)? If you use speakers that have different power-handling capabilities, put the lowest power-handling cab on top closest to your ears so you can hear more easily when or if you are stressing them.

If you start to get anywhere close to dangerous levels for your speaker and you use a clean, clear sound, listen to what's coming out of them. If you start hearing farting noises, you are stressing your speakers and if you don't fix it at once, you will permanently damage them - don't wait for the end of he song, fix it now! If you use distortion or a lot of effects in your signal chain, it becomes geometrically more difficult to detect this stress on your speakers before you've ruined them.

 

[selowitch]

The one caveat you really have to bear in mind though when you have an amp that is capable of blowing the speakers you're using though, is how hard are you driving that amp.

I'm trying to plan ahead to minimize the chance of blowing the amp or the speakers.