Responsible use of amp power

[Wasnex]

When you have a head that does 350W and a speaker that is rated for 225, it's like having a car that can go 180, but sits on tires that are rated for 140. Your car will SAFELY do 140. There might be more in it, but that also might include a wheel flying off at speeds where that is not even remotely funny.

Great example that anyone who has lived in Germany better understand. If you drive your tires above their speed rating, your are very likely to experience a blow out because the tires will overheat. This is relevant to people in the US when you put a little dinky spare on, as they are generally rated for lower speeds than standard tires; typically 50mph. The good thing is you car has a speedometer so you can easily make sure you stay below your tires speed rating.

The allegory to a speedometer in an amp would be a wattmeter, and you would need both a peak and RMS meter. The peak meter would tell you the maximum instantaneous power, and the RMS meter would tell you the average power over time. You need to be mindful of both to ensure you don't blow a speaker.

 

[ThisBass]

Your comment insults the intelligence of Leo Fender and Jim Marshall. They knew more than we will ever know.

You are missing the point cause ignorance does not interfer with intelligence.

Leo was trained as an accounting major and he started to teach himself in electronics in 1928.
Its questionable if Leo really had reasonable skills in mathematics to train himself in electronics the same way such as electronic science was teached on university this time era in the very past.

Furthermore electronic science was much improved way later by folks such as Hendrik Wade Bode and Claude Shannon just to name two of them.

Hendrik Wade Bode - Wikipedia
He also made important contributions to control system theory and mathematical tools for the analysis of stability of linear systems, inventing Bode plots, gain margin and phase margin.

Hendrik Wade did his fundamental work in 1938 for bell laboratories and its questionable Leo really did know about these principles.
Keep in mind that Leo started his own radio repair shop in 1838.


Claude Shannon - Wikipedia
Claude Shannons fundamental work on Entropie and Enthalpie on signals showed clearly that a steady state sine wave does not store no information nothng at all.



In both information theory and as well signal theory engineers try to figure the properties of a transfering channel and also the properties of a given signal and what happens to the signal properties in particalar once the signal was transfered from a transmitter to a receiver.

We have got the oscillating string on the instrument that can be roughly considered as source and the air pressure deviation (SPL) that can be roughly considered as "receiver". Anything between shall be considered as transfering channel that shows distinct transfer properties.

Of course its possible to pick up just one part of the transfer channel (in particular amplifier and loudspeaker) and figure the properties.

Most of the time amplifiers act as proportinal controller device cause the output terminals are linked back to the inverting input stage of the amplifier.
I'm not sure if Leo and Jim really used the engineering tools of phase margin and stability (Bode) when they designed their very first amplifiers.

Leo once did a noticeable design fault cause he loaded the cathode C with a way oversized capacitance. If he would have known better one or two things about systemtheorie than he very likely would had notice the issue coming along with emphasized subharmonic transient noise.
Interestingly Jim Marshall copied the design error just 1:1 once he started to design the Marshall amps.

Leo's first bass combo missed completely the back panel of the cab. Didn't he really not know better when he designed the bass combo this way?
This bass combo proved to be impractical for bass frequencies, against such crap Paul Klipsch (he was used to be a mining engineer) designed the famous Klipsch horn that is still regarded to be a very decent cab and still serves HiFi demands.



A steady state sine wave does not store no information nothng at all. Actually that's the reason WHY it is possible to design 1/3 duty cycle MI amplifiers without sound disadvantage in real practice vers 100% duty cycle amplifiers. Its even possible to draw less power at the wall than the amplifiers power rating at the output, because amp ratings are figured with a steady state sine wave, but hey, as Claude Shannon already told its meaningless to discuss signals that don't store any information.
So it makes absolutely no sense to try to consider a signal that saturates that simultaneously does not carry any information anyway.


You may consider the transfering channel properties (filter and sound processing properties), the power amp capability, the power handling of the loaded driver(s) to the cab, cab tuning, HPF protecting etc


Then you may consider the properties of the signal (the source) cause its anything but never a sine wave. Then in total you may get a picture about how much power (average RMS) will be send to the loudspeaker and how much power density and also peak power in relation to frequency will be send to the loudspeaker.
And if the loudspeaker was not protected by a HPF then the loudspeaker will be strained with (transient) power way down below the lowest tuning of the instrument

I think its not so bad when Eminence suggests a guy to use common sense.
They can't predict "accurately" by numbers any demands and boundaries in real world practice.
Even Leo and Jim could not predict what actually happened in real world practice.

edit,
if you have a feel there was any confusion due to language barrier feel free to ask any question. English isn't my first language you know

 

[Downunderwonder]

The phrase ''store information'' is out of place to me. Notes on a page store information. A 80hz sine coming out of a speaker carries the information that someone is holding down a E on a synthesizer somewhere. Very confusing.

 

[ThisBass]

'Responsibly' is simple enough. It means that you know the weakest link in your chain and will not push the level past that links comfort zone.
When you have a head that does 350W and a speaker that is rated for 225,

That's about rather smallish 5dB Peak to RMS ratio for the signal that comes off your amplifier just to match the thermal handling of the loudspeaker
So if you have fun to play distorted sounds such Lemmy did all along the line on your show? So what.

 

[ThisBass]

The phrase ''store information'' is out of place to me. Notes on a page store information. A 80hz sine coming out of a speaker carries the information that someone is holding down a E on a synthesizer somewhere. Very confusing.

bro, you may remember we discussed this issue some time before, isn't it?
Actually a steady state 80Hz sine wave demands the system for narrow 80Hz channel bandwidth.
If we do it differently and push a couple of repeated bursts of 80Hz then the channel bandwidth must be enlarged from (theortically) 0Hz to infinite.
Just the moment when any sine wave (respectively any signal) starts or stops the demanded bandwidth is quite broad.

Similar things do happen in real practice. Just the moment a player hits the string the frequency bandwidth is very broad and equals noise. Little later, after the envelope may have settled down the Fourier spectrum tries to dominate.

 

[Steve Dallman]

Pretty sure the SWR Triad actually has a reputation for blowing drivers. I believe the problem is something like the 10" is run full range instead of being crossed as a mid range.

Edit: Triad Schematic Attached. Looks like the 10" has a 6dB HPF at around 40hz.

Being that it’s a 4 ohm cabinet, the HPF for the 10 would be closer to 90Hz, but still too low and shallow.

 

[el murdoque]

So if you have fun to play distorted sounds such Lemmy did all along the line on your show? So what.

Lemmy used two stacks of 4x15 and 4x12, each with a 100W head on them. When you know your amp can take running on full throttle, the cabinets won't pose as the weak link in this scenario. Your ears do.

This would be entirely different to the scenario when you use an 800 Watts head on top of a 110 cabinet in a band playing rock. When you crank the master way past what the cab can take, you also get distortion, only it won't last long.

 

[Downunderwonder]

bro, you may remember we discussed this issue some time before, isn't it?
Actually a steady state 80Hz sine wave demands the system for narrow 80Hz channel bandwidth.
If we do it differently and push a couple of repeated bursts of 80Hz then the channel bandwidth must be enlarged from (theortically) 0Hz to infinite.
Just the moment when any sine wave (respectively any signal) starts or stops the demanded bandwidth is quite broad.

Similar things do happen in real practice. Just the moment a player hits the string the frequency bandwidth is very broad and equals noise. Little later, after the envelope may have settled down the Fourier spectrum tries to dominate.

If we discussed sines having ''no information'' before I think I would remember it but quite possibly I didn't understand.

It sounds like your informationless sines get reproduced with no losses?

 

[ThisBass]

So, in a nutshell:
Some amps have way more or way less power than advertised which is irrelevant because the figures that are printed on the cabs are no way near exact as well. You will have to use a combination of your ears and your common sense.

At the other hand side which standard could be best as long as there is no standard out there how to play the bass guitar?
I'd vote for a standard how to play the bass guitar.
In the second step based on reliable standard how to play the instrument I'd estimate a standard for reliable power numbers.

 

[ThisBass]

Lemmy used two stacks of 4x15 and 4x12, each with a 100W head on them. When you know your amp can take running on full throttle, the cabinets won't pose as the weak link in this scenario. Your ears do.

This would be entirely different to the scenario when you use an 800 Watts head on top of a 110 cabinet in a band playing rock. When you crank the master way past what the cab can take, you also get distortion, only it won't last long.

5dB crest consideration

'Responsibly' is simple enough. It means that you know the weakest link in your chain and will not push the level past that links comfort zone.
When you have a head that does 350W and a speaker that is rated for 225, it's like having a car that can go 180, but sits on tires that are rated for 140. Your car will SAFELY do 140. There might be more in it, but that also might include a wheel flying off at speeds where that is not even remotely funny.

Both the rating on the head as well as the rating on the speaker are rough guidelines:
-There are companies known for writing more than twice of the actual continuous output on their amps.
-There are companies that understate that number, sometimes by a few hundred watts.
-Most speakers are rated for how much juice the voice coil can take before it melts - the speaker itself will usually not die the thermal death of a melted voice coil, but die a more violent mechanical death well before the coil melts.


So, in a nutshell:
Some amps have way more or way less power than advertised which is irrelevant because the figures that are printed on the cabs are no way near exact as well. You will have to use a combination of your ears and your common sense.

I ain't feel no need to teach myself but 5dB crest equals the sound that Lemmy did.

 

[Wasnex]

Being that it’s a 4 ohm cabinet, the HPF for the 10 would be closer to 90Hz, but still too low and shallow.

I assumed the 10" is an 8 ohm driver. If the both 10 and 15 are 8 ohms you get 4 ohms nominal for the expected band pass of the box.

 

[ThisBass]

If we discussed sines having ''no information'' before I think I would remember it but quite possibly I didn't understand.

It sounds like your informationless sines get reproduced with no losses?

IIRC you argued this way that even a tune that carries nothing but pure sine waves tranferes information.
And that's right cause different pure sine waves that do change frequency over time do allready store information.
While a steady state sine wave on its own does not.

 

[Downunderwonder]

Major disconnect.

If a monk sits in the square chanting ommmmmm under a blanket for a minute between breaths and twenty people walk past they all get the information there's a monk under that blanket chanting ommmmmm even if they missed the 'o' attack.

Substitute in synth playing E.

 

[el murdoque]

5dB crest consideration



I ain't feel no need to teach myself but 5dB crest equals the sound that Lemmy did.

You lost me at 5dB crest.

 

[iiipopes]

You are missing the point cause ignorance does not interfer with intelligence.

Leo was trained as an accounting major and he started to teach himself in electronics in 1928.
Its questionable if Leo really had reasonable skills in mathematics to train himself in electronics the same way such as electronic science was teached on university this time era in the very past.

Furthermore electronic science was much improved way later by folks such as Hendrik Wade Bode and Claude Shannon just to name two of them.

Hendrik Wade Bode - Wikipedia
He also made important contributions to control system theory and mathematical tools for the analysis of stability of linear systems, inventing Bode plots, gain margin and phase margin.

Hendrik Wade did his fundamental work in 1938 for bell laboratories and its questionable Leo really did know about these principles.
Keep in mind that Leo started his own radio repair shop in 1838.

Claude Shannon - Wikipedia
Claude Shannons fundamental work on Entropie and Enthalpie on signals showed clearly that a steady state sine wave does not store no information nothng at all.

In both information theory and as well signal theory engineers try to figure the properties of a transfering channel and also the properties of a given signal and what happens to the signal properties in particalar once the signal was transfered from a transmitter to a receiver.

We have got the oscillating string on the instrument that can be roughly considered as source and the air pressure deviation (SPL) that can be roughly considered as "receiver". Anything between shall be considered as transfering channel that shows distinct transfer properties.

Of course its possible to pick up just one part of the transfer channel (in particular amplifier and loudspeaker) and figure the properties.

Most of the time amplifiers act as proportinal controller device cause the output terminals are linked back to the inverting input stage of the amplifier.
I'm not sure if Leo and Jim really used the engineering tools of phase margin and stability (Bode) when they designed their very first amplifiers.

Leo once did a noticeable design fault cause he loaded the cathode C with a way oversized capacitance. If he would have known better one or two things about systemtheorie than he very likely would had notice the issue coming along with emphasized subharmonic transient noise.
Interestingly Jim Marshall copied the design error just 1:1 once he started to design the Marshall amps.

Leo's first bass combo missed completely the back panel of the cab. Didn't he really not know better when he designed the bass combo this way?
This bass combo proved to be impractical for bass frequencies, against such crap Paul Klipsch (he was used to be a mining engineer) designed the famous Klipsch horn that is still regarded to be a very decent cab and still serves HiFi demands.

A steady state sine wave does not store no information nothng at all. Actually that's the reason WHY it is possible to design 1/3 duty cycle MI amplifiers without sound disadvantage in real practice vers 100% duty cycle amplifiers. Its even possible to draw less power at the wall than the amplifiers power rating at the output, because amp ratings are figured with a steady state sine wave, but hey, as Claude Shannon already told its meaningless to discuss signals that don't store any information.
So it makes absolutely no sense to try to consider a signal that saturates that simultaneously does not carry any information anyway.

You may consider the transfering channel properties (filter and sound processing properties), the power amp capability, the power handling of the loaded driver(s) to the cab, cab tuning, HPF protecting etc

Then you may consider the properties of the signal (the source) cause its anything but never a sine wave. Then in total you may get a picture about how much power (average RMS) will be send to the loudspeaker and how much power density and also peak power in relation to frequency will be send to the loudspeaker.
And if the loudspeaker was not protected by a HPF then the loudspeaker will be strained with (transient) power way down below the lowest tuning of the instrument

I think its not so bad when Eminence suggests a guy to use common sense.
They can't predict "accurately" by numbers any demands and boundaries in real world practice.
Even Leo and Jim could not predict what actually happened in real world practice.

edit,
if you have a feel there was any confusion due to language barrier feel free to ask any question. English isn't my first language you know

I am not questioning the technical aspects you quoted. I am saying that unless these technical aspects are applied consistently from input jack to speaker cabinet as a system, then there is no way to tell except subjectively if an amplifier from one manufacturer will actually work well with a speaker cabinet from another manufacturer for a given application or genre of music. You do allude to that, but underestimate the importance of the transition. That is where the subjectivity takes over from the objective technical. The concept that at some point the subjectivity has to take over from the objective is a very difficult concept for those, including me, steeped in the accuracy and precision of numbers (from owning my first TI-30 calculator in 1978 as a 15-year-old, and which I still use to this day), to realize. Moreover, it is absolutely necessary that the subjectivity take over, as that is the very foundation of music itself, leaning more into the philosophical, indeed spiritual, and keeps the music alive instead of gathering dust on a science library shelf.

Since you like to quote the technical, read the Hemholz treatise, "On the Sensation of Tone," that attempts to explain why audio signals, including music, do what they do to the human ear, and which I read as an undergraduate in 1981:
Sensations of Tone - Wikipedia
And since German is your primary language, link to the 5th German Edition:
Die lehre von den tonempfindungen als physiologische grundlage für die theorie der musik

And by the way, I learned about Leo's biography and origins 40 years ago, and I own a copy of the same edition of the same RCA circuits book that he used, and which I used when I repaired my own Fender amplifiers decades ago. And as a corollary to my post, Leo was more concerned about the practical aspects of getting musical instruments into the hands of musicians than he was about the raw theory of why they work. That is an intelligence of a different matter, and is not necessarily ignorance of the subject matter, as is the position of your premise.

And now that you have shown your mastery of the technical, it is time for you to appreciate how the technical must be transcended to the other realms of human existence. I suggest starting with the philosophical works of Kierkegaard, especially his concept of "leap of faith," in which he describes the paradox of the limits of the objective in understanding the larger issues of existential truth. Then you can proceed from there to Buber and his philosophy of dialog, Nietzsche and his philosophy of the meaning of existence, Bonhöffer on the integration of the spiritual with the temporal, and so on, to give context as to why the numbers are meaningful, but not an end in themselves.

 

[ThisBass]

Sensations of Tone - Wikipedia

Any kind of science in general have vey much improved since this book was published about 140 years ago.

Even music has much advanced since Franz Liszt began to compose quite "complex" music.

I'm not sure Helmholtz did know that a sine burst generates a very similar frequency spectrum like generated by a pulse.
Furthermore a system can show time variant properties as well as time invariant properties.
I think Helmholtz would have wrote a different textbook if he would have had the tools of systemtheorie.

In the meanwhile we do know that even the Fletcher Munson curves for equal-loudness contours are faulty cause the curves are derived from (meaningless) sine waves.
We do also know that even the common standard of dB(A) measurement may deliver very faulty results for (random) dynamical signals.

As the dbA measurement may deliver quite faulty outcomes in the EU its more common to use the ITU-R 468-weighting
Invalid Link Removed

 

[Downunderwonder]

Riddle me this: how does something with frequency and amplitude at the same time have no information?

 

[ThisBass]

Riddle me this: how does something with frequency and amplitude at the same time have no information?

For example if there was a steady state sine wave that shows both steady frequency and steady amplitude over (infinite) time duration then there is no information stored.

There could be information stored IF the sine wave could also be switched to OFF.

Regarding Shannon theorem the least storable information equals flipping a coin. The information given will equal pitch-and-toss, head or tail.
A coin that would show "head" on each side of the coin could be flipped but would not provide (respectively store) information anymore.
Flipping a coin like this would equal very much a steady state sine wave.

 

[seamonkey]

Riddle me this: how does something with frequency and amplitude at the same time have no information?

 

[Downunderwonder]

For example if there was a steady state sine wave that shows both steady frequency and steady amplitude over (infinite) time duration then there is no information stored.

There could be information stored IF the sine wave could also be switched to OFF.

Regarding Shannon theorem the least storable information equals flipping a coin. The information given will equal pitch-and-toss, head or tail.
A coin that would show "head" on each side of the coin could be flipped but would not provide (respectively store) information anymore.
Flipping a coin like this would equal very much a steady state sine wave.

I think I see the disconnect. That's digital information. Humans take note of the steady state with a fast enough refresh rate making it ''new info'' again and again.