Interesting conversation about speakers and ohms

[BigBobbyBass]

I can't believe this is even an argument..

 

[Mark Reccord]

You are missing the point. To the average person an 800 W amp should not be able to overheat a 1000 W cab. You have to understand the difference between sine and square waves and you have to understand that many 800 W amps will deliver far more than 1000 W to a cab when overdriven in order to understand why this is possible. The average person does not understand this so to them the statement that you can blow a speaker by underpowering it is true. They actually have blown 1000 W cabs with 800 W amps so obviously it is true. They don't know that the cab doesn't meet their needs because amps are rated by their sine wave outputs. We who understand physics understand the problem but to the average person it looks for all the world like you can blow a cab by underpowering it.

You are exactly right (and I said essentially the same thing in my previous post). This is why the idea that undepowering a speaker can blow it continues to exist.

 

[khutch]

You are exactly right (and I said essentially the same thing in my previous post). This is why the idea that undepowering a speaker can blow it continues to exist.

Yes we agree. Perhaps we went to the same engineering school?

I am an engineer and a bass player but the only amp I own is a Peavey 75 W all in one keyboard amp for practicing. I play in a church band through the house system so I don't need an amp. As a result I don't know how amps are commonly rated other than they all carry sine wave output ratings. If they don't also carry maximum output ratings then they should so that people can safely mate amp to cab. In the absence of this people should double the sine wave output rating to find the required cab rating because while you are correct that the power supply and heatsink/thermal cutback of the amp may limit the output power of the amp to less than this, if an amp has a good enough power supply and heatsink you will in fact get twice the sine wave output if you drive it hard enough. Maybe we collectively know that the safe derating factor is 1.5 or 1.8 or ??? instead of 2 but people definitely do need to derate their cabs.

 

[CL400Peavey]

You are missing the point.

No. You're missing the point.

To the average person an 800 W amp should not be able to overheat a 1000 W cab.

Considering that by far most cabs meet their mechanical limits well before their thermal specs, it is a moot point. Power ratings on commercial cabs are bullsh!t spewed by marketeers. If an average person pushes a cab to the point that is sounds like it is going to blow, and then continues to push it, they deserve a broken cab for being stupid.

You have to understand the difference between sine and square waves and you have to understand that many 800 W amps will deliver far more than 1000 W to a cab when overdriven in order to understand why this is possible. The average person does not understand this so to them the statement that you can blow a speaker by underpowering it is true.

It is still over powering. It is not my responsibility to teach physics to the masses. I got paid to do that when I did, and unless someone is cutting me a check, they can learn by their own mistakes. Over powering is overpowering. If you do it with a 500 watt amp or a 2000 watt amp, the results are the same.

They actually have blown 1000 W cabs with 800 W amps so obviously it is true. They don't know that the cab doesn't meet their needs because amps are rated by their sine wave outputs. We who understand physics understand the problem but to the average person it looks for all the world like you can blow a cab by underpowering it.

As one learns from studying physics, some things are not intuitive. Not. My. Problem.

It comes down to personal responsibility. Learn about your gear. Learn about which ratings matter, and which do not. Learn about the capabilities. Learn to use your ears an listen to the system.

You are exactly right (and I said essentially the same thing in my previous post). This is why the idea that undepowering a speaker can blow it continues to exist.

And it is part of the problem. Stop watering down the discussion for those that cant step up to the metaphoric table of understanding. It may appear that they damaged a cab using an under powered amp, but if they pushed that much content through the cab with a much more powerful amp, they still would have damaged the cab.

It is time for people to give up the voodoo and mythology, and start giving them the real, if difficult for them to understand, answers.

 

[CL400Peavey]

If they don't also carry maximum output ratings then they should so that people can safely mate amp to cab.

They do provide those ratings. They specify a power output at a particular THD%.

Maybe we collectively know that the safe derating factor is 1.5 or 1.8 or ??? instead of 2 but people definitely do need to derate their cabs.

The ratings on cabs are thermal ratings. Which are crap to begin with, and mechanical ratings are well below those points. No big manufacturer posts those, as they are less marketable.

 

[the_stoot64]

You are all far too committed to arguing rather than committed to the topic if you can be bothered sorting out all those individual quotes like that...

On a slightly related note, how much effect does frequency have on wattage? Will low pass filters allow you to give your cab more of a hiding?

 

[CL400Peavey]

You are all far too committed to arguing rather than committed to the topic if you can be bothered sorting out all those individual quotes like that...

Nah. You just select the sections, and it lets you easily use the multi quote function that is built in.

On a slightly related note, how much effect does frequency have on wattage? Will low pass filters allow you to give your cab more of a hiding?

It depends.

Using a HPF will increase your amp's head room, and decrease the excursion of your drivers which may increase the useable volume. The down side of this is that the cones moving less, provides less cooling to the voice coils. So depending on all things, it may hurt you, as it pushes the thermal limits down, possibly below, the mechanical limits.

There is no magic bullet.

 

[Mark Reccord]

And it is part of the problem. Stop watering down the discussion for those that cant step up to the metaphoric table of understanding. It may appear that they damaged a cab using an under powered amp, but if they pushed that much content through the cab with a much more powerful amp, they still would have damaged the cab.

It is time for people to give up the voodoo and mythology, and start giving them the real, if difficult for them to understand, answers.

Yes, I'm clearly guilty of watering down the discussion because I've never explained what is actually happening when people claim that they blew a speaker by underpowering it before. Oh wait, I did that in my first post in this thread not to mention about 900 other times on the Amps forum over the years often in the face of vehement opposition. If you think my posts are helping perpetuate the misunderstandings around this, you're not reading them.

 

[CL400Peavey]

Yes, I'm clearly guilty of watering down the discussion because I've never explained what is actually happening when people claim that they blew a speaker by underpowering it before. Oh wait, I did that in my first post in this thread not to mention about 900 other times on the Amps forum over the years often in the face of vehement opposition. If you think my posts are helping perpetuate the misunderstandings around this, you're not reading them.

I was responding in conjunction to your response to khutch.

 

[the_stoot64]

Nah. You just select the sections, and it lets you easily use the multi quote function that is built in.

Oh, right. I'm only used to less advanced forums.

 

[CL400Peavey]

Oh, right. I'm only used to less advanced forums.

Most people dont even know it is an option.

 

[ThisBass]

You are missing the point. To the average person an 800 W amp should not be able to overheat a 1000 W cab. You have to understand the difference between sine and square waves and you have to understand that many 800 W amps will deliver far more than 1000 W to a cab when overdriven in order to understand why this is possible. The average person does not understand this so to them the statement that you can blow a speaker by underpowering it is true. They actually have blown 1000 W cabs with 800 W amps so obviously it is true. They don't know that the cab doesn't meet their needs because amps are rated by their sine wave outputs. We who understand physics understand the problem but to the average person it looks for all the world like you can blow a cab by underpowering it.

One of the problems is that power handling indeed depends on the waveform.
A pink noise with 6db crest will cause twice as much movement to the cone then a square wave that equals the power of the pink noise. A square wave has no crest!
Movement of the cone is one of the variables responsible for VC cooling.
So I would not expect just same power handling for square waves. IMO it's good practice to have power handling doubled in this case. That is meant for dirty sounds like Lemmy Kilmister.

If some "fart out" of the amplifier is audible due to some overload at the power amp there is (in most cases) no concern. Clipping starts at transients first, at next the decay will be effected, and not till clipping starts to claw the sustained signal part clipping stays inaudible. At this point the average power is far away from just to be doubled. The average at this point may be considered as a combination of compressed/clipped decay and some clipped part of the sustained note. A sustained note as well has lots of crest (more then a sine) so clipping this part of the signal "somewhat" does not immediatelly double power.

Unfortunatelly the transition to dirty sounds is fluently. Therefore there is no firm point where power starts to be doubled.

Clipping artifacts become well audible at an average of around 1/3 of rated amp power (clipping of decay and some interference of the sustained part), the more the amplifier is pushed the more power is squeezed out of the amp, and in reverse the more the crest of the signal is decreased just the same way.
In theory the power out of the amp is finally doubled, the crest of the signal smashed to continous zero!

In practice:
300 watt amplifier hard pushed, some audible clipping at E1/B0 string, so average power not more then 100 watt in this case. Any cab rated to 300 watt power handling can withstand this strain of power.

300 watt amplifier very hard pushed to a very dirty sound like Lemmy Kilmister, dirty sound at all strings of the instrument, now at this point output power probably is doubled to 600 watt average. Any 300 watt cab probably will suffer the magic smoke (sooner or later). May be a 600 watt cab will suffer some damage of the VC if strained far too long because "additional" cooling is missing due to the zero crest of the signal. The vc is missing 1/2 of ventilation because +6db crest of the signal is missing.

So I'd suggest 1200 watt power handling for the cab in this case.

To be honest, if the cab really does withstand strain like that I'm pretty sure the amplifier will show the magic smoke sooner or later.

 

[BurningSkies]

The reality is that few cabs suffer mechanical failure (or often thermal failure) without giving the user warning. The real answer is 'user error' or 'user abuse' is the cause of these problems rather than over or under-powering.

I'm OK with that. If people haven't bothered to learn how their gear works, they'll keep wrecking the stuff they spent all their money on. The reality is that it's not a 'wave type' or clipping that kills speaker cabinets. It's too much juice. If you go in without an understanding about how both speakers and amps are 'rated' you sort of get what you deserve. If you don't bother to listen to your cab while you're playing it and notice when it starts to fail, that's not the fault of your speakers impedance or the voltage coming out of your amp's output.

 

[CL400Peavey]

The reality is that few cabs suffer mechanical failure (or often thermal failure) without giving the user warning. The real answer is 'user error' or 'user abuse' is the cause of these problems rather than over or under-powering.

I'm OK with that. If people haven't bothered to learn how their gear works, they'll keep wrecking the stuff they spent all their money on. The reality is that it's not a 'wave type' or clipping that kills speaker cabinets. It's too much juice. If you go in without an understanding about how both speakers and amps are 'rated' you sort of get what you deserve. If you don't bother to listen to your cab while you're playing it and notice when it starts to fail, that's not the fault of your speakers impedance or the voltage coming out of your amp's output.

A-fugging-men.

 

[ThisBass]

Some folks prefere dirty sounds generated by overloaded "vintage" amps. So it don't makes me wonder sometimes a speaker fails allthough power handling of the cab seems to be right matched to the amplifier.
By the other hand lot of folks prefere vintage cabs as well to get their specific dirty vintage tone.
Hard pushed vintage amp versus a vintage 212 or 215 cab loaded with 1.5" VC loudspeakers I bet the VC is without a chance!

 

[Mark Reccord]

I was responding in conjunction to your response to khutch.

I don't see how that's watering anything down, though. I was simply agreeing that what khutch posted is why this myth continually pops up. I don't think either of us are suggesting that people should be left to carry on in that ignorance, even if they don't fully understand the mechanics of it. In my case, nothing could be further from the truth as I've expended considerable effort to counter the misunderstandings over the years.

The reality is that few cabs suffer mechanical failure (or often thermal failure) without giving the user warning. The real answer is 'user error' or 'user abuse' is the cause of these problems rather than over or under-powering.

I'm OK with that. If people haven't bothered to learn how their gear works, they'll keep wrecking the stuff they spent all their money on. The reality is that it's not a 'wave type' or clipping that kills speaker cabinets. It's too much juice. If you go in without an understanding about how both speakers and amps are 'rated' you sort of get what you deserve. If you don't bother to listen to your cab while you're playing it and notice when it starts to fail, that's not the fault of your speakers impedance or the voltage coming out of your amp's output.

A-fugging-men.

Fully agreed.

 

[khutch]

They do provide those ratings. They specify a power output at a particular THD%.

The ratings on cabs are thermal ratings. Which are crap to begin with, and mechanical ratings are well below those points. No big manufacturer posts those, as they are less marketable.

No, part of the problem is that there are apparently no power ratings given that would allow the great unwashed masses to safely connect amps to cabs that are appropriate for each other. The power rating you mention above is the sine wave rating. It is an important rating, people do want to know this number for many reasons. But it is NOT the rating you need when you are choosing the power handling capacity of the cab you intend to connect to youramp. When you drive an amp well past the rated THD the output power level will rise above the level it hits at the rated THD. As we have said above it could double but that depends on the amp's power supply capacity and the heatsinks on the output devices in the amp.

I don't know why you would say that cabs reach their mechanical limits before their thermal limits. It could be that you just don't understand that the power output of an 800 W at 0.1% THD amplifier will be well above 800 W when you overdrive it. If that is true then you are proving the contention that amps need a separate rating for maximum output power so that the appropriate cab ratings for an amp can be specified.

On the other hand if a cab that can safely take a 1000 W sine wave at some frequency before it reaches its thermal limit will truly blow up at, what do you want to say here, 500 W ??, with some other waveform or frequency for mechanical reasons then I would certainly agree with you that the 1000 W rating on the cab is crap, worse than useless. If a cab is rated at 1000 W then it should be able to safely absorb 1000 W regardless of the waveform and frequency. Cab manufacturers need to be honest about this. If neither cab makers nor amp makers are honest about their power ratings then there is no hope for people to safely build a system except by trial and error and of course the cost of the errors will add up very quickly in this case.

But, if I accept that everything you say about amp and cab ratings is true then it is also 100% true that a "500 W" amp can blow up a "1000 W" cab since the amp's actual output will exceed 500 W and the cab's actual power handling capacity is much less than 1000 W. If you want to make that statement untrue then you have to convince the industry to remove the quotation marks from both of those ratings. Honest and appropriate ratings communicated effectively to consumers would prevent problems in the field. Except for those idiots who choose to ignore them....

 

[CL400Peavey]

The power rating you mention above is the sine wave rating.

The mechanical or THD rating? The mechanical rating would be lower in the majority of cases, but the THD would be that "standard sine wave" rating. The distortion amount tells you how far past it was measured.

I don't know why you would say that cabs reach their mechanical limits before their thermal limits.

Because it is the reality of the matter. Most thermal power ratings are taken at 1khz, which is generally useless for bass, as the majority of their signal content is well below that point. A mechanical power rating at say 100hz would be more meaningful.

But, if I accept that everything you say about amp and cab ratings is true then it is also 100% true that a "500 W" amp can blow up a "1000 W" cab since the amp's actual output will exceed 500 W and the cab's actual power handling capacity is much less than 1000 W.

And if the circumstances are "worse case", yes you can blow a 1000 watt cab with a 500 watt amp. But if you understand what is going on, you can use a 3000 watt amp and a 100 watt cab.

If you want to make that statement untrue then you have to convince the industry to remove the quotation marks from both of those ratings. Honest and appropriate ratings communicated effectively to consumers would prevent problems in the field. Except for those idiots who choose to ignore them....

This is the true crux of the matter. While I agree that meaningful ratings would benefit many, there is no regulation of standards, so marketeers will go with what presents best. Good luck trying to change the industry.

 

[Passinwind]

. Most thermal power ratings are taken at 1khz,

Please cite who still does this rather than using band limited noise of one flavor or another, I haven't seen it in years and none of the modern standards are set up that way. I recently posted a link to Eminence's take on the subject, here it is again: [Invalid or Expired Link Removed]

 

[khutch]

This is the true crux of the matter. While I agree that meaningful ratings would benefit many, there is no regulation of standards, so marketeers will go with what presents best. Good luck trying to change the industry.

Sometimes industries will self regulate in response to consumer complaints and even the barest threat of government action. In recent years this has become fairly common although certainly not universal. Other times you do need to go to the government and demand some action. If this is a real problem for people and the industry has not addressed it then it is time to go to the governments. We TB members come from all around the world, all it would take would be for one government anywhere in the world to demand fair ratings because then we could all go to the websites of the companies that sell in that country to see the ratings on their products. If that caused the sales numbers for the other companies to tank because we would only buy products with true and appropriate ratings they would all get religion pretty fast.

Or we can just continue to beat each other up about it. As I have said none of this is a problem for me right now but if one of you wants to draft a reasonable letter or petition to the appropriate US government departments or to Congress I would support it. Other governments would probably not pay much attention to the concerns of US citizens so I can't help those outside the US, you'd need to get your own country-men and -women on board. In the end perhaps no government will perceive it to be a big enough problem to get much of a response so success is not certain, but if we don't make the effort we certainly will not get a response.