Question about wattage and speakers

[ThisBass]

@ThisBass, I believe the case is worse than you stated. RMS watts is a misnomer. If watts is stated as a sine wave, then the volts, is a square root sine function. I believe the RMS is a voltage reference.
If you look at the power formula, it's VI, Il, or VV, which means watts is sine squared function. Which means the area factor is 0.5 not 0.707. I believe the area to peak value ratio can be called RMS.

As stated, square waves can generated by clipping sine waves, but they can also be generated by adding harmonics, particularly odd harmonics. Something, effects can be designed to do.

sine wave
1 Vpeak => 0.707 Vrms (root mean square)
1 Vpeak => 0.6366 Varv (average rectified value)

square wave
1V peak => 1 Vrms
1V peak => 1 Varv

P=SQR(Vrms) / Z
Both signals at 1 Ohm pure resistive Z will provide
sine wave: 0.5 Watt
square wave: 1 Watt

Symmetrical waveform Harmonics spectrum like square wave and trangle waveform is all of odd order Harmonics
While asymmetrical waveform spectrum like saw tooth and MI signals is of even and odd order Harmonics.

Combined (complex) signals like envelope decay generate a second (transient) spectrum that equals an gaussian bell curve that spreads from (theoretical) DC to infinite Hz.
These are the things we try hard to challange with sound designs especially at overload range cause way to often a system seems to be as time-variant just to provide a distinct musical sounding property.

 

[Drgonzonm]

Tell you what. If you can cite your reference, I'll defend your non-troll status.

I did some Eminence + underpower + speaker googling and came up with this.

Can under-powering a Guitar speaker do damage? | Eminence Speaker

It's probably not what you read as they say it's... well read for yourself what they say.

If you can provide a link to the Eminence information you mentioned, I would be interested in reading it.

That being said, please note that I specifically discussed that speakers are not damaged by under-powering them.
See post #41.
That's not to say I wouldn't be interested to read subjects about under-powering in other contexts.

Also please note that woofers and bass guitar speakers are different tools intended for different uses.

Thanks

from Understanding Loudspeaker Data | Eminence Speaker
Power handling
This specification is very important to transducer selection. Obviously, you need to choose a loudspeaker that is capable of handling the input power you are going to provide. By the same token, you can destroy a loudspeaker by using too little power.
It doesn't say much, I suspect, that its possible to fry speakers, in some of the more complicated internal wiring for two and three way speakers. Something, I have seen in bass cabinets. I am guessing, that some of the filtering methods require a mininum power, to properly work.
I agree that subwoofers and bass speakers are have different applications. as the subwoofer, I have has inductor coils, that I am guessing require the wattage just get the inductors working.
IMO, there is not a lot of information, provided about the cabinet, and the replacement speaker to make more than general comments. For all we know, the replacement speaker was a guitar speaker, and the OP uses effects and a 5 string bass.

 

[Drgonzonm]

@Thinkbass, your link, may provide insight to the failure mechanism of the OP's speaker. Eminence rates their speakers on thermal limits. if some of the mechanical limits had been exceeded, and I am talking about the core.
It would be nice to know, cabinet models and replacement speaker models. With a little luck, it might be possible to find data on the speakers. Resonance frequency value on the original speaker and the replacement would be helpful. It would also be helpful to know if the cabinet is two or three way.
I wish the OP would have been more specific in what data he presented.

 

[Drgonzonm]

....

Combined (complex) signals like envelope decay generate a second (transient) spectrum that equals an gaussian bell curve that spreads from (theoretical) DC to infinite Hz.
These are the things we try hard to challange with sound designs especially at overload range cause way to often a system seems to be as time-variant just to provide a distinct musical sounding property.

I prefer log-normal curves, instead of gaussian curves. I am guessing that we don't have to worry too much about infinite Hz, on class D amps, do we?

 

[ThisBass]

I re-iterate: Too much power dissipated by the voice coil is what leads to burnt voice coils. It doesn't matter how you get there, the end result is the same.

You can argue this and that, but it doesn't change this simple fact.

So I might also power a 300 Watt RMS/AES rated woofer with DC power 300 Watt for about 30 minutes without damage the VC?

If it was only too much of power power that burns the VC then the VC should also survive any of it as long as the power did not exceed the manufacturers power rating, even for DC.

Or might there indeed be a distinct relationship of power versus frequency versus crest number versus spectrum distribution?

 

[ThisBass]

I prefer log-normal curves, instead of gaussian curves. I am guessing that we don't have to worry too much about infinite Hz, on class D amps, do we?

At least these additional Harmonics give enough reason to protect woofers from overxcursion with a HPF. No, its not the Fundamental of the lowest tuning of the instrument that gives enough reason for protecting aims with a HPF.
The Gaussian bell curve appears in the frequency domain so of course it is log-normal scaled.
However the power density is hard to predict but normally settles at the lowish side of the spectrum and spreads a very broad bandwidth. It adds musicality to the tone but also can harm woofers with ease if there is no protection with a HPF

 

[byacey]

So I might also power a 300 Watt RMS/AES rated woofer with DC power 300 Watt for about 30 minutes without damage the VC?

If it was only too much of power power that burns the VC then the VC should also survive any of it as long as the power did not exceed the manufacturers power rating, even for DC.

Or might there indeed be a distinct relationship of power versus frequency versus crest number versus spectrum distribution?

This sounds like a rather foolish suggestion. I don't know of any manufacturer that rates their loudspeakers to withstand a continuous RMS signal level for an extended period of time. Nor do they rate amplifiers at a 100% duty cycle, if you remember back to a previous similar thread about amplifier ratings.

 

[Drgonzonm]

This sounds like a rather foolish suggestion. I don't know of any manufacturer that rates their loudspeakers to withstand a continuous RMS signal level for an extended period of time. Nor do they rate amplifiers at a 100% duty cycle, if you remember back to a previous similar thread about amplifier ratings.

I agree with you if we stay within the realm of MI amplifiers. While researching ultra-low frequency speakers, it appears some of the armed forces are developing subsonic speakers as offensive weapons.
Another area, that uses speakers with continuous signals is ultrasonics. Look at ultrasonic cleaners, some of the higher end vaporizers. Again these are outside the MI amplifiers so I will go find a warm spot under a bridge.

 

[byacey]

Ultrasonic transducers are usually a piezo element, not a moving coil.

 

[ThisBass]

This sounds like a rather foolish suggestion. I don't know of any manufacturer that rates their loudspeakers to withstand a continuous RMS signal level for an extended period of time.

Many small boutique manufacturers rate exactly the number the loudspeaker manufacturer rates the woofer. These are average continuous numbers representing a broadband signal (almost always) withstanding +6dB crest. Its the cab manufacurers responibility to adjust mechanical power handlng versus "thermal" power handling but, no need to accuse they would not state (thermal) continuous numbers. Actually they state these numbers for a distinct crest number. And these numbers are pretty much serious numbers as long as the numbers are taken in (heavy duty) pratical sense rather than "hopeless idealistic"

Nor do they rate amplifiers at a 100% duty cycle, if you remember back to a previous similar thread about amplifier ratings.

If I remember correctly there had been many of these threads.
Just telling about my 70's svt amplifier the svt growl is already there at about 1/4 duty cycle, 1/2 duty is good enough to play stoner rock sounds at its best and if somebody needs more of dirt out of the svt power amp really should buy a different amplifier cause the legendary svt amplifier worns out quickly if stressed with 100% duty cycle over time.
There are better options to get 100% duty cycle like with pedal boards or preamp drive settings BUT, the power amp and cabs should be designed accordingly just to handle these sounds savely over time IF these sounds are the main prefered sounds all along the line at high level volume!

No its not a trick question but I don't understand the benefits that a continuous 100% duty cycle rated amplifier would outperform my 70's svt amplifier?

May be the 100% duty cycle subject was good enough to open a new thread with the question:
What benefits do you expect for you in practice from a 100% duty cycle amplifier?

 

[bumperbass]

There's no guarantee that the 1000 watt head did ALL the damage. It could have been out it's way out anyhow with the 700 watt head. 10 years is a long time in speaker life. Voice coils sometimes may change shape after that long, and yours probably rubbed a bit without you noticing. I also agree a 1000 watt head is too much for one speaker. Why do you think you need that much power? More cone area wins over more power, all other things equal.

 

[ThisBass]

So here we are
What benefits do you expect for you in practice from a 100% duty cycle amplifier?

 

[Djadja]

A couple of observations...

The head is 700 watts into 8 ohms (likely the load of a single speaker).

The replacement speaker being considered only goes up to 1K... given the rest of the discussion here, I’m assuming there is no tweeter in the cab... so this speaker alone would sound like poop.

The recommendations to scrap the cab and purchase a new cab strike me as being the wisest and best bang for the buck in the long term.

As for needing to double the RMS rating of the amp in your cab... naw. The key is simply to pay attention. You can still destroy the speakers in a cab that is rated at 800 watts using a 400 watt cab or even less (read all of the discussions about mechanical vs. thermal ratings) if you push the speakers too hard. FWIW, I run a Genzler Magellan 800 (400 watts into 8 ohms) into a single Genzler BA12-3 (8 ohm cab, rated 350 watts). If I had two of the cabs, giving me 4 ohms, the head would be 800 watts and the cabs rated at 700. Genzler designed this head and these cabs to run together.

 

[dejavoodoo]

what is your tone setting? it takes a LOT more power to replicate the lower tones, and boosting the bass knob will send more power to the speaker.

also measure the internal dimensions of the cab to determine if the speaker will work. talk to someone @ Eminence, or US Speaker, and they can guide you to what speaker will work best in that box.

 

[dejavoodoo]

Also.......
4 or 5 string? Bass boosted on an open B string with some volume = speaker death way too often. A constant struggle for me

 

[byacey]

So I might also power a 300 Watt RMS/AES rated woofer with DC power 300 Watt for about 30 minutes without damage the VC?

If it was only too much of power power that burns the VC then the VC should also survive any of it as long as the power did not exceed the manufacturers power rating, even for DC.

Or might there indeed be a distinct relationship of power versus frequency versus crest number versus spectrum distribution?

I don't know of any musicians that walk on stage with a bunch of test gear monitoring the output of their amplifier to prevent burning up the speakers. It would make it kind of hard to concentrate on playing.

 

[Old Garage-Bander]

It wouldn't change a bit cause even for a slightly clipped sine the flat top of the signal then would show same changes as shown for the square.
Its either way questionable to try to explain amplifier overload characteristic and pending power with sine waves and its (transient) crossing up to a square.
The consideration is (of course) very easy to understand and also helpful to explain some basic things but, probably also suitable to be a good soil just to let grow any kinds of myths (sorry for direct words).

Nice metaphor. Good soil to grow myths.

 

[Old Garage-Bander]

sine wave
1 Vpeak => 0.707 Vrms (root mean square)
1 Vpeak => 0.6366 Varv (average rectified value)

square wave
1V peak => 1 Vrms
1V peak => 1 Varv

P=SQR(Vrms) / Z
Both signals at 1 Ohm pure resistive Z will provide
sine wave: 0.5 Watt
square wave: 1 Watt

Symmetrical waveform Harmonics spectrum like square wave and trangle waveform is all of odd order Harmonics
While asymmetrical waveform spectrum like saw tooth and MI signals is of even and odd order Harmonics.

Combined (complex) signals like envelope decay generate a second (transient) spectrum that equals an gaussian bell curve that spreads from (theoretical) DC to infinite Hz.
These are the things we try hard to challange with sound designs especially at overload range cause way to often a system seems to be as time-variant just to provide a distinct musical sounding property.

Waaaah Haaaanh Haaaanh Why can't I just plug in my bass and play?

 

[Old Garage-Bander]

from Understanding Loudspeaker Data | Eminence Speaker
Power handling
This specification is very important to transducer selection. Obviously, you need to choose a loudspeaker that is capable of handling the input power you are going to provide. By the same token, you can destroy a loudspeaker by using too little power.
It doesn't say much, I suspect, that its possible to fry speakers, in some of the more complicated internal wiring for two and three way speakers. Something, I have seen in bass cabinets. I am guessing, that some of the filtering methods require a mininum power, to properly work.
I agree that subwoofers and bass speakers are have different applications. as the subwoofer, I have has inductor coils, that I am guessing require the wattage just get the inductors working.
IMO, there is not a lot of information, provided about the cabinet, and the replacement speaker to make more than general comments. For all we know, the replacement speaker was a guitar speaker, and the OP uses effects and a 5 string bass.

Thanks for citing the reference.
Comments later, if necessary, after taking some time to digest it.

 

[Drgonzonm]

Waaaah Haaaanh Haaaanh Why can't I just plug in my bass and play?

The math is a good reason to play an electric acoustic bass unplugged. Maybe three or four people can hear you, but think about quiet it would be. But we still have to fire the drummer for being so loud.
(Could you imagine the roadies putting up and taking down the the shell of the the Hollywood bowl for every concert? No more t-shirts and jeans, just tuxes)