Pushing a cabinet - Question

[Ryan Schmoll]

Hopefully some of you can help clarify for me. I have a 1000-watt amp and one 4x10 cabinet that is rated for only 500. I keep asking the question about pushing the cab too hard but I get conflicting answers. Here are some of the answers I've received -

• It's fine. You're already pushing 1000 watts regardless of your volume.
• You should be fine if you don't push the master volume too hard. (I keep it at halfway out of fear, currently).
• Be careful, you'll blow your speakers if you go past halfway. Add another cabinet.

Obviously there has to be a right answer here, so I'm hoping some of you smart fellas can confirm what I should do.

Thank you!

 

[smeet]

Knob positions don't tell you much about how power the amp is putting out. Just use common sense - listen for any sounds of distress from the speakers (farting out, etc.). And watch your volume, don't try to make a 410 sound like an 810.

What amp and cabinet are we talking about?

 

[ddnidd1]

Hopefully some of you can help clarify for me. I have a 1000-watt amp and one 4x10 cabinet that is rated for only 500. I keep asking the question about pushing the cab too hard but I get conflicting answers. Here are some of the answers I've received -

• It's fine. You're already pushing 1000 watts regardless of your volume.
• You should be fine if you don't push the master volume too hard. (I keep it at halfway out of fear, currently).
• Be careful, you'll blow your speakers if you go past halfway. Add another cabinet.

Obviously there has to be a right answer here, so I'm hoping some of you smart fellas can confirm what I should do.

Thank you!

I don't know who's giving you advice, but they aren't particularly knowledgeable.

The wattage out is varied by the volume control(s). It does not run at 1000 all the time.

The position of the knob doesn't tell you Anything about the number of watts being output to the speakers

Generally, assuming you're not using distortion, you can Hear when the speakers are straining and breaking up. Also, the more low end your pushing to the point of being somewhat excessive, the harder it is on the speakers and the greater the potential for damage.

Basically, it just comes down to listening to your amp and using common sense.

 

[RustyAxe]

It's fine. You're already pushing 1000 watts regardless of your volume.

No, you are not. The output power is dependent on volume.

You should be fine if you don't push the master volume too hard. (I keep it at halfway out of fear, currently).

This is correct. At the first sign of distortion you'd better throttle back though. Nothing will kill speakers like overdriving them by running the amp into clipping (not your problem) or driving the speaker into distortion.

Be careful, you'll blow your speakers if you go past halfway. Add another cabinet.

First part is true. Second part is true, too, but it's not that you can run more power to the cab (actually, your amp will put out more power at a given volume setting into a lower impedance) but that an additional cab will provide much more speaker surface area, producing more volume from the same power. Add another identical 4x10 and you'll hear the difference (and feel it when your pant legs start flapping!).

 

[HolmeBass]

The thing about output wattage. It being directly related to master volume knob position is tricky. I will try to explain it.

The each stage of the amp multiplies the sing along by some amount, determined by the knob position of that stages's gain/volume knob. But the output is not a constant, it is a multiple of the input value. So hotter signal in, hotter signal out for a control at the same position, up to the point that the amp is maxed out.

So output master knob position could be giving you all 1000 watts even at 50% ( noon) if the input signal to the output stage is hot enough. That would include the output strength of your bass plus the amount of gain added by the pre-amp and any active EQ you may have applied.

So in the end, you have to rely on your ears, and not knob positions to get a feel if you are stressing your speaker cabinet.

Also be aware of two possible failure modes: thermal, which is too high avg signal level melting the internals of the speaker, and over-excursion, caused by too much low frequency content.

 

[EastCoastThump]

So in the end, you have to rely on your ears, and not knob positions to get a feel if you are stressing your speaker cabinet

^This.

In general, *power amp* ratings characterize the ability to amplify a test signal (under specified and controlled conditions) without noticeably distorting it. Your amp is rated at 1000 watts w/ a specified input signal into a specified load while not distorting the input signal beyond the specified THD.

As an imperfect analogy, imagine a car that has two speed ratings:
1) a speedometer whose uppermost marking indicates the fastest speed the car could hit under perfect conditions (downhill track, tailwind, etc).
2) a manufacturer's rating that indicates how fast the car can be run at sustained speed on the test track without overheating.

You've been thinking of your amp's THD power rating to be like #1. It's more like #2 (a focused measurement of one aspect of performance under controlled conditions, not a measure of how fast the car will be moving when you've wrung every last drop of Go! out of it).

Now, imagine your cab's rating to be like the speed rating on a spare tire. "Vehicle speed should not exceed 50 mph when using this tire." That's a measure of the performance limit at which the product will start to be destroyed. Note that the tire's rating has a purpose that has little to do with either of the speed ratings of our imaginary car; it's a different kind of measurement.

Does this mean that I can't drive my car with a donut spare? No, I just need to be careful to use it within limits.

 

[walterw]

besides, what impedances are we talking about here? into an 8Ω cab, i doubt you're really anywhere near 1000 watts unless you're bridging a PA power amp.

 

[Geri O]

Good call, Walter...

 

[Downunderwonder]

Now that OP is somewhat educated, some more caution.

Say you follow the good advice to limit your low end demands. It's entirely possible to have a thermal failure, which is somewhat harder to avoid by listening.

What you "hear" first is less apparent headroom. At this stage the natural instinct is to grab a little more of the loud knob. If this fails to excite you need your spidey senses to go off. You have hit the thermal limit and your drivers are beginning to toast.

Now, why are you needing to push 4x10 hard? Ime that's very loud, any louder and you're drowning out drums and vocals in your typical bar gig situation, if not already.

 

[ddnidd1]

besides, what impedances are we talking about here? into an 8Ω cab, i doubt you're really anywhere near 1000 watts unless you're bridging a PA power amp.

How can you make that statement? There is no information re: the Amp, the Cabinet.

 

[walterw]

How can you make that statement? There is no information re: the Amp, the Cabinet.

right, just an educated guess. typical 4x10 cabs are 8Ω, and typical bass amps are not 1000w at 8Ω.

a hartke lh1000 in bridge mode for example is 1000w at 4Ω, and more like 750w at 8Ω.

 

[ddnidd1]

right, just an educated guess. typical 4x10 cabs are 8Ω, and typical bass amps are not 1000w at 8Ω.

a hartke lh1000 in bridge mode for example is 1000w at 4Ω, and more like 750w at 8Ω.

Yeah, but your 'Educated guess', could lead him to blowing up his cab. It doesn't take 1000 watts to fry his speakers - probably a LOT Less.

Could end up being the 'Typical' blown up cabinet.

 

[Geri O]

How can you make that statement? There is no information re: the Amp, the Cabinet.

Because if you deal with several types and brands of cabinets and amplifiers, that's an easy general statement to make. If there's a Peavey TNT 112 or an double-810 cab SVT, then you'll be a little off. But how may of those do you see every day? And if those rigs were the case, I'd hope the OP would mention it.

And it's not brain surgery. If you want to make it into brain surgery, then pull out the voltmeter and measure what the amp can actually do at a given load. Do the math and the conversions (volts converted to watts at the given impedance and so on). You can then assess exactly what the cabinet will handle

But wait....

 

[Geri O]

Yeah, but your 'Educated guess', could lead him to blowing up his cab. It doesn't take 1000 watts to fry his speakers - probably a LOT Less.

Seriously, dude, let's not get over-excited about this. There's waaay more that the OP can do to blow up his cab than to listen to an educated guess on a bas forum.

 

[ddnidd1]

Seriously, dude, let's not get over-excited about this. There's waaay more that the OP can do to blow up his cab than to listen to an educated guess on a bas forum.

So if I understand you correctly, pushing an amp, never mind a relatively powerful amp (arbitrarily 1000 watts ), with maybe too much low end, is not a concern as far as frying speakers?

So how many watts are Safe to push with 'Some' amp and 'Some' Cabinet?

Your answer will Finally settle Many TB threads on the subject.

 

[Matt O]

I agree with the get another cab advice that the OP received. Either two cabs that can handle that load and give you some headroom or a get a different single cab that can handle it. Sure, you could run the thing below half volume as it is and be safe, hopefully, but that begs the question: why do you have a 1000 watt amp?

 

[ddnidd1]

But you Cannot know where (TRUE) Half (or SAFE) Volume is by the O'Clock
setting of the Volume Knob(s).

If I were you, I would do a search on TB for answers to this question.

It has been covered, in detail, by Very Knowledgeable players, more so than myself or the other Experts in this thread.

Do a bit of research on TB so you know how to get the most out of your amp without frying speakers and later having to post 'I blew up my amp. What did I do wrong?

I only had the volume knob set at ? o'clock'.

 

[Matt O]

It has been covered, in detail, by Very Knowledgeable players, more so than myself or the other Experts in this thread.

I would learn to speak for yourself. You have no idea what my experience level is.

OP: I suggest again, get a cabinet, or two, that will handle that load or get a different head. I would rather play through a 300 watt head that I could push without fear than a 1000 watt head that I'm scared is going to fry my speakers.

 

[ddnidd1]

I agree with the get another cab advice that the OP received. Either two cabs that can handle that load and give you some headroom or a get a different single cab that can handle it. Sure, you could run the thing below half volume as it is and be safe, hopefully, but that begs the question: why do you have a 1000 watt amp?

I would learn to speak for yourself. You have no idea what my experience level is.

OP: I suggest again, get a cabinet, or two, that will handle that load or get a different head. I would rather play through a 300 watt head that I could push without fear than a 1000 watt head that I'm scared is going to fry my speakers.

I certainly don't know what Your experience level is. Please check in with the knowledgeable TB respondents.

However, the OP is asking about potentially over driving and frying His speakers. The OP needs to understand that there is a variety of ways to overdrive and cook his speakers.

Again, to the OP. please do a search on TB regarding over driving speakers.

 

[SunnBass]

However, the OP is asking about potentially over driving and frying His speakers. The OP needs to understand that there is a variety of ways to overdrive and cook his speakers.

Well, then stop arguing with everyone and tell him already.