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Two Basic Amplifier Questions

fpitas

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Sokel

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There's some interesting threads on ASR at the moment about 'real world' issues; amp behaviour under difficult loads, power over a full frequency range etc. This seems to fit onto that.

So, for a real world question: what kind of Speakers are needed to handle this sort of power? A mid-range example like Kef R3 has a recommended max power of 180W. The Kef Information Sheet does not qualify this so I don't know if that's peak (surely not) or only for a frequency and impedance range. Whatever, it's lower than 500W and nowhere near 2kW

Does this comment on 'real power' needed for a full dynamic range in music mean that most speakers can't handle the power required anyway?

Do speaker specifications describe what is needed, or is this another area where specs are not enough?
Think of 8361A and it's 5" midrange driver.
Specs for the whole speaker are 700 W Bass + 150 W Midrange + 150 W Treble.

Obviously it's little mid would even take as much as 150 W continuous,but it's enough for the peaks,so is the tweeter.
That's what many people don't take into account,they confuse peak and max power,former can be +15db from the later.
 
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fpitas

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Think of 8361A and it's 5" midrange driver.
Specs for the whole speaker are 700 W Bass + 150 W Midrange + 150 W Treble.

Obviously it's little mid would take even take as much as 150 W continuous,but it's enough for the peaks,so is the tweeter.
That's what many people don't take into account,they confuse peak and max power,former can be +15db from the later.
Yes, you have a point. But that all depends on a good crossover with reasonable filter skirts. A lot of lower priced speakers just have a capacitor as a high-pass, for example. And the woofers often go when someone decides to entertain the neighborhood.
 
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I'm using the millivoltmeter- 200kHz bandwidth in my distortion analyzer. Class AB amp, so no HF garbage to throw it off. It'll read down to 30uV or so. There's around 100uV of residual in the amplifier (65uV A-Wtd) Obviously at 2mV there is also a contribution of noise from the preamp, amp and source. But that doesn't really matter, I couldn't hear any noise at ~1ft and the absence of the tone (switched to shorted input) dropped the reading to the baseline 100uV.

The baseline is the tone- can you hear it or not and at what level can you hear it on your loudspeakers in your room.

I'll revisit the test again later when it cools down (31 degrees C here) and see if I get different numbers. I may have made a mistake- who knows. :)
Assuming threshold is reached when you raise above the noise floor of your room. -Could be as high as 40 dB. I'm fortunate to have 20-30 dB noise floor in my room according to if my HVAC is on or off. Dependent of course on the noise frequency characteristics as well but simplified nonetheless. If this is the premise I guess you can look at it as the ambient noise is reducing the "in-room speaker sensitivity". But again this is overly simplified as your ambient noise in room hopefully isn't a 1.000 Hz tone!

Source-->https://simplehomecinema.com/2023/06/25/how-noise-floor-impacts-your-sound-quality/
Real-Dynamic-Range.jpg
 

Sokel

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Yes, you have a point. But that all depends on a good crossover with reasonable filter skirts. A lot of lower priced speakers just have a capacitor as a high-pass, for example. And the woofers often go when someone decides to entertain the neighborhood.
Every pro woofer speaker advises for a high-pass so it's operating area starts at 20-25Hz or so,just to protect them.
So...
 

fpitas

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pro woofer speaker
Exactly! And it's a cliche that when people try to use "home" speakers for pro use they don't last very long.
 

Sokel

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Assuming threshold is reached when you raise above the noise floor of your room. -Could be as high as 40 dB. I'm fortunate to have 20-30 dB noise floor in my room according to if my HVAC is on or off. Dependent of course on the noise frequency characteristics as well but simplified nonetheless. If this is the premise I guess you can look at it as the ambient noise is reducing the "in-room speaker sensitivity". But again this is overly simplified as your ambient noise in room hopefully isn't a 1.000 Hz tone!

Source-->https://simplehomecinema.com/2023/06/25/how-noise-floor-impacts-your-sound-quality/
Real-Dynamic-Range.jpg
I was about to shout about that 100db orchestra crescendo but then I saw it's dbA weighted so it's ok-ish for front seats.
 

peng

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There's some interesting threads on ASR at the moment about 'real world' issues; amp behaviour under difficult loads, power over a full frequency range etc. This seems to fit onto that.

So, for a real world question: what kind of Speakers are needed to handle this sort of power? A mid-range example like Kef R3 has a recommended max power of 180W. The Kef Information Sheet does not qualify this so I don't know if that's peak (surely not) or only for a frequency and impedance range. Whatever, it's lower than 500W and nowhere near 2kW

restorer-john made the point about how "People have underestimated how much power they think they need forever.", but the opposite could also be true, as it really depends on the individual's applications.

Back to your question, as you know, KEF's specs say 15-180 W, 4 ohms nominal, 3.2 ohms minimum. In terms of "real-world" use, KEF does say a little more in their FAQ than what's in the info sheets:

Rule of Thumb:

In the real-world, it’s best to ignore the low-end spec. That’s shown to show the minimum amount of power needed to move the voice coils in any appreciable manner.
A good match is an amplifier capable of producing between 60% and 110% of the recommended maximum.
For example, the R5 shows a Recommended Amplifier Power of 15 to 200 WPC. A good match for this speaker would be an amplifier that produces between 120 Watts per Channel ((200x.6)*100) and 220 WPC ((200x1.1)*100). In terms of performance and damage potential, an amp rated lower than 60% of maximum poses far more danger to the loudspeaker than an amp rated above the maximum.

Does this comment on 'real power' needed for a full dynamic range in music mean that most speakers can't handle the power required anyway?

No, it doesn't mean that, as again, it depends on your own applications. For example, if you sit only 2 meters from your R3, that is 4 ohm nominal, 87 dB/2.83 V/m, then you will get about 81 dB spl, and that would be 2 W based on the sensitivity spec.

So, if you listen to music that has 20 dB peak dynamic (not that common, but there are plenty of such examples), based on 81 dB average, your amplifier would have to be able to output 200 W into 4 ohms without clipping. An AVR, except the likes of the Denon AVR-8500H, A1H, or the Onkyo top models could do that, but the midrange models will likely be clipping occasionally when you listen to contents that have 20 dB dynamic peaks.

If I were to size my power amp for the R3 Meta, I would get one of those buckeye amp such as the NC502MP, just as an real-world example.

Do speaker specifications describe what is needed, or is this another area where specs are not enough?

In my opinion, they typically don't and practically speaking it would be too much work for them as they have no way of knowing the various applications of their customers. In some cases, manufacturers such as KEF, B&W, SVS, Revel etc., might provide additional info in their FAQ section (such as KEF) or other publications. Or you can email them, provide them the details of your applications and listening habit, and they will likely tell you more about what you may need for amplification.
 

Bob from Florida

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Being concerned about having a 16 bit dynamic range seems ludicrous considering most recorded music is way less than 40 db dynamic range. I agree with John that everyone underestimates power requirements during musical peaks. But since clipping is going to happen at higher volumes anyway, shouldn’t we be just as concerned with how the amp recovers from the clipping episode? Another consideration is speaker efficiency- efficient speakers don’t need high power.
 

restorer-john

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But since clipping is going to happen at higher volumes anyway, shouldn’t we be just as concerned with how the amp recovers from the clipping episode?

Absolutely. But when, since the 1970s, did any magazine or reviewer bother to test for the overload recovery characteristics of any amplifier?

I test for this regularly and it isn't pretty. The quality reviewers in the 70s and 80s tested for this as a matter of course.
 

peng

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Being concerned about having a 16 bit dynamic range seems ludicrous considering most recorded music is way less than 40 db dynamic range. I agree with John that everyone underestimates power requirements during musical peaks. But since clipping is going to happen at higher volumes anyway, shouldn’t we be just as concerned with how the amp recovers from the clipping episode? Another consideration is speaker efficiency- efficient speakers don’t need high power.
"everyone"? That also seems ludicrous:D But I guess we can all exaggerate a little:) to make out points so okay.
 

PeterNL

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I'm embarrassed to ask such seemingly simple questions, but I can't seem to find the answer on my own!

1) An amplifier is rated for 60W @ 8ohm and 100W @ 4ohm. The speaker is rated as having 6ohm impedance.
Will the amplifier automatically run at 6ohm and provide power between 60 and 100W? Say, around 80W?

2) Say that a speaker is rated for handling between 100 and 200W RMS. Say that the listening volume is held constant at 70db.
Will a speaker powered by 200W, have any better sound quality than if powered by 100W, at the same 70db volume?
I'm aware that more power will enable higher volumes, but at the same volume does a speaker 'work' and sound better with more watts (within RMS)?
Wharfedale Linton are 6ohm rated but their impedance drops to +/- 3.5ohm.
Wharfedale Linton 85 (Grille On) Impedance.png


Having 100W@4ohm amplifier, it should be enough for 70dB levels or even more, but don't forget that 100W of your amplifier is measured at 1kHz, at the low end frequency, speakers need more juice than at 1kHz.
If You are going to use EQ or Dirac room correction, EQing dips for example about +6dB, You will loose 6dB of your amplifier headroom because then You should compensate 6dB boost and set your digital EQ or Dirac preamplifier to negative -6dB (preventing digital clipping).
In this case, not much headroom will be left.

Please correct me if I'm wrong, I'm not an expert.
 

fpitas

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Wharfedale Linton are 6ohm rated but their impedance drops to +/- 3.5ohm.
View attachment 321109

Having 100W@4ohm amplifier, it should be enough for 70dB levels or even more, but don't forget that 100W of your amplifier is measured at 1kHz, at the low end frequency speakers needs more juice than at 1kHz.
If You are going to use EQ or Dirac room correction, EQing dips for example about +6dB, You will loose 6dB of your amplifier headroom because then You should compensate 6dB boost and set your digital EQ or Dirac preamplifier to negative -6dB (preventing digital clipping).
In this case, not much headroom will be left.

Please correct me if I'm wrong, I'm not an expert.
Yes, if you start cranking in serious EQ at bass, the required power will soar. You may also burn out your woofers :)
 

Sokel

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Absolutely. But when, since the 1970s, did any magazine or reviewer bother to test for the overload recovery characteristics of any amplifier?

I test for this regularly and it isn't pretty. The quality reviewers in the 70s and 80s tested for this as a matter of course.
Is that what this test looks like?

recovery.PNG
 
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