I can't find it in the FAQ's....

[TravTrav]

When you have a solid state head that runs at 300 watts at 8ohms, you can run a single 8 ohm cabinet that handles 400 watts....so lets say this same head runs at 500 watts @ 4ohms. If you run two 8 ohm cabinets that handle 400 watts will this be okay?

Adding up the cabs will you have the capability of running 800 watts @ 4 ohms? Or will the head run 500 watts to each cabinet exceeding their capabilities?

[PJMiDi]

Originally Posted by TravTrav

Adding up the cabs will you have the capability of running 800 watts @ 4 ohms?

this so it would be fine

[TravTrav]

Thanks, duder.

[parsons]

the head will run at whatever the manufacturer says itll run at the given impedance. That said, if your head runs 500w @ 4ohms, your cabs are getting 500w run through them. If the cabs are plugged in parallel, you can think of them as one large 4ohm cabinet.

[BBEgo]

Yes, but the cabs will only get 500w, theoretically splitting it 250w each.

[RickenBoogie]

except that the wattage ratings on the cabs are all but meaningless. an 800 watt cab can't actually handle 800 watts in most cases. and then there's the matter of what frequency it's measured at, and the fact that ANY amp can potentially blow ANY cab.

[Caca de Kick]

Originally Posted by TravTrav

.so lets say this same head runs at 500 watts @ 4ohms. If you run two 8 ohm cabinets that handle 400 watts will this be okay?

Yes, it's plenty fine. it really doesn't matter how many cabs you run as long as you don't go below the minimum impedance (most amps are 4ohm, some go to 2ohm)

Adding up the cabs will you have the capability of running 800 watts @ 4 ohms? Or will the head run 500 watts to each cabinet exceeding their capabilities?

1) In a rough nutshell yes
2) but the head will still only put out 500w. It will divide that power to the quantity of cabinets you're using. So in this case two cabs are 8ohm each, so each cab will see 250w from the head.

[WhoDidTheElf]

Originally Posted by RickenBoogie

except that the wattage ratings on the cabs are all but meaningless. an 800 watt cab can't actually handle 800 watts in most cases. and then there's the matter of what frequency it's measured at, and the fact that ANY amp can potentially blow ANY cab.

Case in point, I was at GC and there was a couple of kids noodling around on an Little Mark III head into a Ampeg 8x10E. The head puts out around 500 watts and the cab can take 800 Watts RMS.

They had the volume pretty high up there and were using a EBMM Ray. Problem; they had the bass knob on the ray full tilt, the volume on the ray cranked to the moon, full gain on the head and full lows and low mids, ect...

The room sounded...bad...and there was a funny smell, maybe burning coil, I don't know to be honest. Needless to say when I came back a week later the cab was gone. Either sold or blown up. No clue which but if I were a betting man I'd put my money on the later rather than the former.

Either way, just looking at the watts that shouldn't have happened, but I have a feeling that those speakers where pushed beyond their mechanical limits.

[TravTrav]

^^^That's kind of a funny story. Thanks for all the insight guys.

SO. Another question for ya'll.....how bad would it be to have two different brands of cabs, but they each have the same model speaker? Like, if I were to have a peavey cab and an ampeg cab, but each had a Celestion BN15 400s.

Sorry for all the questions, but I'm n00b and am trying to put together a ragtag rig of sorts.

[billfitzmaurice]

Originally Posted by TravTrav

.how bad would it be to have two different brands of cabs, but they each have the same model speaker? Like, if I were to have a peavey cab and an ampeg cab, but each had a Celestion BN15 400s.
.

If you mean BN15 400S8, they'd both fart out with more than 60 watts input. That's because that driver has only 2mm xmax, and it's xmax that limits driver output, not the thermal rating of the voice coil.
When you get down to it the wattage ratings of cabs mean next to nothing.

[lbwdog]

Originally Posted by TravTrav

When you have a solid state head that runs at 300 watts at 8ohms, you can run a single 8 ohm cabinet that handles 400 watts....so lets say this same head runs at 500 watts @ 4ohms. If you run two 8 ohm cabinets that handle 400 watts will this be okay?

Adding up the cabs will you have the capability of running 800 watts @ 4 ohms? Or will the head run 500 watts to each cabinet exceeding their capabilities?

Do yourself a favor. Remember this:
1; Forget watts on cabs except when comparing one cab to another. Ferinstance, if a particular 410 claims 100 watts, and another claims 1000 watts, you can bet the first cab has cheaper, flimsier speakers than the second cab, and won't take as much power or abuse. Speaker wattage rating just gives you a loose idea of what it can handle.

2; Just because you flip the "ON" switch on a 500 watt (or 800w or 1500w, etc) head, doesn't mean that it will be producing 500 watts at all times. At normal playing levels, the output will be a fraction of that (unless you push the volume to "TEN" and go blasting away, in which case you'll probably be busting speakers left and right!). The wattage rating means it is capable of producing that.

In the old days (sixties?), specs on equipment was not as focused on as it is today. In fact, most young players didn't
know Ohms from rabbit turds. We just plugged in and played. If it distorted, we knew we needed a bigger rig with more speakers!

[TravTrav]

Originally Posted by billfitzmaurice

If you mean BN15 400S8, they'd both fart out with more than 60 watts input. That's because that driver has only 2mm xmax, and it's xmax that limits driver output, not the thermal rating of the voice coil.
When you get down to it the wattage ratings of cabs mean next to nothing.

I meant my question in a completely different instance. Basically all I'm getting at is, whether I'd notice something weird with my rig if I ran two different sized cabs with the same speakers. Like, how some people claim that things get weird when you run 10's with a 15.

[Bass_Pounder]

Originally Posted by TravTrav

^^^That's kind of a funny story. Thanks for all the insight guys.

SO. Another question for ya'll.....how bad would it be to have two different brands of cabs, but they each have the same model speaker? Like, if I were to have a peavey cab and an ampeg cab, but each had a Celestion BN15 400s.

Sorry for all the questions, but I'm n00b and am trying to put together a ragtag rig of sorts.

Originally Posted by TravTrav

I meant my question in a completely different instance. Basically all I'm getting at is, whether I'd notice something weird with my rig if I ran two different sized cabs with the same speakers. Like, how some people claim that things get weird when you run 10's with a 15.

How did BOTH cabs from different makes come to have the same speakers ?

If someone swapped out the speakers (or you are planning to do it) without first measuring the internal volume of the cab and modeling the speakers in design software, one or both cabs could end up sounding like ass.

Additionally, if both cabs are different sizes, then it is almost a given that at least one will sound bad since the tuning frequency will be different between the two.

[steveksux]

Originally Posted by RickenBoogie

except that the wattage ratings on the cabs are all but meaningless. an 800 watt cab can't actually handle 800 watts in most cases. and then there's the matter of what frequency it's measured at, and the fact that ANY amp can potentially blow ANY cab.

That's true. I'm running 2 cabs rated at 500W driving them with a 1500W amp, 750 watts apiece, for >10 years and haven't blown them yet. So a cab rated at 800w can't handle 800w, it can likely handle substantially more than that.

Randy

[Bass_Pounder]

Originally Posted by steveksux

That's true. I'm running 2 cabs rated at 500W driving them with a 1500W amp, 750 watts apiece, for >10 years and haven't blown them yet. So a cab rated at 800w can't handle 800w, it can likely handle substantially more than that.
Randy

It's actually opposite.

The thermal rating of most speakers are FAR above what they can handle mechanically.

In your case, you have the POTENTIAL to feed each cab 750 watts - you certainly are not even coming close.

[steveksux]

Originally Posted by Bass_Pounder

It's actually opposite.

That's funny, considering the general rule of thumb is to use an amp rated 1.5 to 2x the RMS rating of the cabs.

The thermal rating of most speakers are FAR above what they can handle mechanically.

If you use crappy speakers in poorly designed enclosures.

In your case, you have the POTENTIAL to feed each cab 750 watts - you certainly are not even coming close.

In so far as the wattage going to the cabs vary according to the loudness of the music, you are correct, I'm not feeding the cabs a steady diet of 750 watts apiece all the time. However on louder gigs without PA support, I have seen the clip lights on the amp engage before. So yes, I have fed those cabs plenty of power, with no ill effect. I don't have my EQ set with a lot of boost at crazy freqs in the lower end of the spectrum either though.

Randy

[Bass_Pounder]

Apparently then, you have not been reading or paying attention to posts made by all the speakers designers on the forum.

[WhoDidTheElf]

Originally Posted by steveksux

That's funny, considering the general rule of thumb is to use an amp rated 1.5 to 2x the RMS rating of the cabs. If you use crappy speakers in poorly designed enclosures.

I don't know if I would consider an Ampe SVT 810E a crappy enclosure.

[steveksux]

Originally Posted by WhoDidTheElf

I don't know if I would consider an Ampe SVT 810E a crappy enclosure.

I don't know if I would consider it likely that the speaker was blown by the LMIII head while you were watching, and wasn't damaged earlier. Not saying its impossible, if someone sets the EQ on "stupid" like that kid in the store did.

But I still say that's not what happened, because if you really smelled coil burning, then that would indicate the thermal limit was reached, rather than the mechanical limit, and the thermal limit isn't going to be reached with a 500W amp driving an 800W cab in a half hour of noodling around no matter how badly the EQ is set. I'm assuming the Ampeg is honestly rated at 800W, its not a 2nd rate cab.

Keep in mind, that RMS 800w rating is continuous long term average. Every space between notes, every pause between songs, the power is essentially zero, and the voice coil gets a break to cool off, and the average power drops as a result. Its like the difference between you driving at 80 mph on a trip, take a few breaks, your average speed ends up much lower due to the breaks taken at zero mph.

On the other hand, keep in mind that the 500W amp can put out peaks in excess of 500W also.

The most likely explanation is the cab was already in trouble before that kid plugged it in.

Randy

[steveksux]

Originally Posted by Bass_Pounder

Apparently then, you have not been reading or paying attention to posts made by all the speakers designers on the forum.

I believe that would be you who are not paying attention.

Randy