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What's the science behind more power leading to better sound?

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#1
I understand that better amps have less noise and lower output impedance and how those affect the sound. Not too sure about the balanced vs. unbalanced amp or if it it's important.
But one thing I never really understand was how power (supposedly) gives better sound.
Obviously, more volume typically leads to a perceived better sound.
But if my phone is able to power something like the HD600 to a comfortable volume, why does an amp give (supposedly) better sound?
From what I've heard, just because you can have enough volume doesn't mean there's enough power to drive the drivers properly.
Thus, having more power is able to make the bass tighter or whatever.
I never understood this. If you can drive the headphones at volume, what other digital or electrical or analog properties are needed to make it be properly driven?

*Note* I do not own an amp at this point. Running everything out of my phone or mobo. I'm thinking of getting a JDS Atom and either SDAC or Topping D10/30 desktop stack in the future and call it there.
 

Ron Texas

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#2
More power may help in large rooms or with low efficiency speakers or it could be a waste. Up to a point louder sounds better and more powerful amps can avoid clipping, which is a very gross form of distortion and can damage speakers.
 

garbulky

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#3
I understand that better amps have less noise and lower output impedance and how those affect the sound. Not too sure about the balanced vs. unbalanced amp or if it it's important.
But one thing I never really understand was how power (supposedly) gives better sound.
Obviously, more volume typically leads to a perceived better sound.
But if my phone is able to power something like the HD600 to a comfortable volume, why does an amp give (supposedly) better sound?
For the HD600 and the HD6xx, it's not supposedly. Just plug it in. I have used the HD600 in to phones, tablets, and a variety of amps. I can hear a difference between an iphone and the bas-x A-100 though I haven't done a DBT. If you do a DBT test, there's a very good chance imo you will hear a difference. I don't know the reason though.
 
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#4
More power may help in large rooms or with low efficiency speakers or it could be a waste. Up to a point louder sounds better and more powerful amps can avoid clipping, which is a very gross form of distortion and can damage speakers.
Right, but in the context of headphones and IEMs, how do they help? For example, the Sony MDR-EX1000 apparently needs a lot of power, and even though you can get the same volume off a phone or a DAP, A/B testing supposedly gives better details and audio quality.
Also, how do powerful amps avoid clipping? From my understanding, clipping comes from having too much volume or is within the audio track instead.
 

Blumlein 88

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#5
For the HD600 and the HD6xx, it's not supposedly. Just plug it in. I have used the HD600 in to phones, tablets, and a variety of amps. I can hear a difference between an iphone and the bas-x A-100 though I haven't done a DBT. If you do a DBT test, there's a very good chance imo you will hear a difference. I don't know the reason though.
I'm pretty sure though it is powerful the bas-x a100 has a very high output impedance. This alone would likely alter the response. It also would worsen damping in the bass.
 

DonH56

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#6
The peak-to-average power ratio for music is about 17 dB (from old, old data) and for movies 30 dB has been measured. 17 dB is a power factor of 50; 30 dB is a power factor of 1000. More power provides headroom to prevent clipping, but of course the need very much depends upon your system. A pair of insensitive speakers like my old Magnepans placed 12 feet away in a very dead room need a lot more power than a pair of high-sensitivity horn speakers six feet away in a live room.

Also remember that 1 dB is scarcely notable if you increase the SPL by that much and takes about 25% (1.25x) more power. 3 dB is about the change when you increase the volume "just a little" and requires 2x (double) the power. Doubling the perceived loudness in the midrange is an increase of 10 dB and takes 10x (ten times) the power.

Putting some numbers to them:

A pair of Magnepan planar magnetic dipoles, 83 dB/W/m, 12' away in a heavily-treated room produce about 75 dB SPL at the listening position when driven by 1 W. Pushing them with 10 W produces 85 dB, and 100 W yields 95 dB. I need 2000 W to reach Dolby/THX "reference" of 105 dB SPL per speaker. Assuming they have not dissolved into charred oblivion by then.

A pair of horn speakers with 101 dB/W/m sensitivity placed 12' away will produce about 93 dB from 1 W in the same room, and if placed in the corner of a "live" (more reflective) room will produce about 99 dB with just 1 W. So, 1 W with horns in a live corner is louder than 100 W into my beloved Maggies stuck in my heavily-treated room! 10 W into those corner-loaded horns yields 109 dB; 100 W goes to 119 dB. Move the listening position to 6', half the distance, and the SPL at 1/10/100 W rises to 105/115/125 dB.

100 W for the pair of horns in the corner is plenty more than enough, but I'd need 1000 W or so driving the Magnepans to get close. So "how much power do I need" depends very much on the speakers you have, room they are in, and how far away you are from them.

See e.g. http://myhometheater.homestead.com/splcalculator.html

HTH - Don
 
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amirm

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#7
Excellent post Don. The only thing I would add is that sensitivity numbers from speaker/headphone manufacturers is not standrdized and is a valuable marketing number. So expect them to be inflated versus reality (in other words, you need more power than they may indicate).
 

DonH56

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#8
Excellent post Don. The only thing I would add is that sensitivity numbers from speaker/headphone manufacturers is not standrdized and is a valuable marketing number. So expect them to be inflated versus reality (in other words, you need more power than they may indicate).
Thanks. But, Marketing inflates things? Surely you jest... :)

IIRC the old IHF standard was measured with a sine wave (single tone) at 1 kHz and 1 m though many test systems measured at 2 m to ensure drivers had coalesced. I do not know if that was ever made official by the FTC. The big problem (and I know you know this!) is that speaker impedance varies, often widely (or maybe "wildly"), over frequency so 1 W in the midrange may be 0.1 W someplace else and 10 W at some other frequency. It'd be nice if the spec was for worst-case but that is never the case (AFAIK) and you'd still need to know where (at what frequency) that worst-case dip occurred. ESLs dip at HF but there is less signal up there so it does not matter all that much. I'd be more worried about big conventional speakers that have impedance dips in the midrange and upper bass right where we are sensitive to them.

And that is not even considering loudness curves and how our hearing sensitivity tapers off at high and low frequencies so more power is needed to hear them at the same level (loudness) as midrange frequencies.

Bottom line is you need to allow enough headroom to minimize clipping in your system at the listening levels you prefer. I listen on the quiet side compared to many so get away with a few hundred watts despite relatively insensitive speakers in a heavily-treated room. If you like it really loud, get horn speakers and the amps to drive them. And be prepared for hearing problems as you age (due to the loudness, not the horns).
 
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garbulky

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#9
I'm pretty sure though it is powerful the bas-x a100 has a very high output impedance. This alone would likely alter the response. It also would worsen damping in the bass.
The A-100 has two output impedances. One is 220 ohms which is rather high. This is due to the dropping resistor. Emotiva did mention that this high output impedance changes the FR depending on headphones allowing a sound reminicent of old stereo receivers headphone amp.

The other one is when the resistor is bypassed which is the mode I used. This one has a low output impedance and massive amounts of power though it comes at the cost of increased noise which is audible during silence. I've tried both modes, and both sound better than the iphone to the HD600 and hd6xx. Subjectively, the two modes of the a-100 sound different to each other, but it's not something that stands out instantly. I don't think I could distinguish it in a DBT - though you may be able to tell by the mild hiss on silence. I prefer the mode without the resistor.
 
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#10
Thanks for the insight Don, but that raises more questions for me and I think my main questions is still not yet answered (?)

What do you mean by peak-to-power ratio? I understand that dB is on a logarithmic scale and thanks to your post, I now understand that more power means less clipping. However, what do you mean by the "midrange" rather than the range as a whole?

I think though that the crux of my initial question is still not answered (unless I'm mistaken). Why do more powerful amps give a better sound even when compared at the same volume to weaker amps (e.g. a desktop amp vs. a phone)? Supposedly, in certain situations it can help add more detail to the bass or make the highs a bit more crisp, etc.
On some level, I kinda get it. Like if you have a diaphragm that is really stiff compared to one that is more pliable, more power is needed to "push" the stiffer diaphragm properly. But if you can get the same volume off a phone vs. a good amp, what contributes to the better sound? From my understanding, volume comes from the amp's ability to power the drivers. If my phone has a weaker amp, I just need to turn it up until there's enough voltage (or watts?) to reach the same volume as a more powerful amp, correct? So what makes the difference in "better sound" if all you need to do is turn up the volume? Provided there's not clipping or that kind of technical faults.
 

RayDunzl

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#11
Why do more powerful amps give a better sound even when compared at the same volume to weaker amps (e.g. a desktop amp vs. a phone)?
Is that true?

Better to establish that first.

It seems to me you're asking for an explanation for what could be a myth, and unhappy about not receiving an answer.
 

bigx5murf

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#12
No one mentioned the most obvious? Bass, for the most part requires the most power and control to produce accurately. When you start running out of power, it's what gets affected first. I've noticed with hard to drive headphones and speakers. The lack of power first manifests as lack of control, where the bass starts to ring, then lower bass levels compared to the rest of the frequencies, then bass distortion.
 
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#13
Is that true?

Better to establish that first.

You're asking for an explanation for what could be a myth, and unhappy about not receiving an answer.
Well that's why I've put "better sound" or "supposedly" in quotes multiple times throughout. If it's a myth, that's fine. But so far in this thread, it doesn't seem like anyone is addressing if it is a myth and if not, why it happens.
Unfortunately, I cannot establish that first because I do not have access to a good amp yet. When I do get one I'll know for myself if it really makes a difference or not.
 
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#14
No one mentioned the most obvious? Bass, for the most part requires the most power and control to produce accurately. When you start running out of power, it's what gets affected first. I've noticed with hard to drive headphones and speakers. The lack of power first manifests as lack of control, where the bass starts to ring, then lower bass levels compared to the rest of the frequencies, then bass distortion.
Right. This is the explanation I've heard the most for why more power = "better sound".
But can't you get more power simply by just turning up the volume? Assuming you don't start clipping or max out the volume knob.
Or does power unequally affect the volume of different frequencies? Doesn't that then mean that your amp itself has a distinct "frequency response"?
 

garbulky

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#15
Well what do you mean by better sound? Because I've heard sound from a 5 watt tube amp that sounded very close to my 1000 watt/channel high bias class A/AB amplifier in terms of how good I thought it sounded. They both sounded different though (subjective test no DBT)
 
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#16
Well what do you mean by better sound? Because I've heard sound from a 5 watt tube amp that sounded very close to my 1000 watt/channel high bias class A/AB amplifier in terms of how good I thought it sounded. They both sounded different though.
In the context of headphones and IEMs, from what I've heard people say, "better sound" in terms of stuff like tighter bass, more slam, firmness, and detail in the bass, and more detail/crispness in the highs. A lot of audiophile speak.
Like stuff would sound good out of a weaker amp, but when compared to a more powerful amp, the sound gets more controlled I guess?
 

garbulky

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#17
Right. This is the explanation I've heard the most for why more power = "better sound".
But can't you get more power simply by just turning up the volume? Assuming you don't start clipping or max out the volume knob.
Or does power unequally affect the volume of different frequencies? Doesn't that then mean that your amp itself has a distinct "frequency response"?
Good question. What causes the difference. I agree that if you have enough power then if there is a difference there must be a way to measure it. I just don't know what it is
 

DonH56

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#18
Thanks for the insight Don, but that raises more questions for me and I think my main questions is still not yet answered (?)

What do you mean by peak-to-power ratio? I understand that dB is on a logarithmic scale and thanks to your post, I now understand that more power means less clipping. However, what do you mean by the "midrange" rather than the range as a whole?

I think though that the crux of my initial question is still not answered (unless I'm mistaken). Why do more powerful amps give a better sound even when compared at the same volume to weaker amps (e.g. a desktop amp vs. a phone)? Supposedly, in certain situations it can help add more detail to the bass or make the highs a bit more crisp, etc.
On some level, I kinda get it. Like if you have a diaphragm that is really stiff compared to one that is more pliable, more power is needed to "push" the stiffer diaphragm properly. But if you can get the same volume off a phone vs. a good amp, what contributes to the better sound? From my understanding, volume comes from the amp's ability to power the drivers. If my phone has a weaker amp, I just need to turn it up until there's enough voltage (or watts?) to reach the same volume as a more powerful amp, correct? So what makes the difference in "better sound" if all you need to do is turn up the volume? Provided there's not clipping or that kind of technical faults.

You listen at an average level but there are peaks much louder (higher) than that. Drums in music, gun shots or explosions in movies, and so forth can have peaks much larger than the average listening level. Even single tones have a peak value higher than its average level; look up "crest factor".

Midrange is typically defined as the voice band, 300 Hz to 3 kHz, the frequency range typical of the average voice. A deep male voice down to 300 Hz, a baby's cry up around 3 kHz. Our hearing peaks (is most sensitive) at around 3 kHz. Below that range is bass or low frequencies (LF) and above treble or high frequencies (HF).

I don't know about the rest of "better". In some cases a lower-powered amp that has greater SNR (lower noise) will sound better than a high-powered amp. More powerful amplifiers have things other than higher watts as your first post said. Lower output impedance may better control the speakers. Better power supplies may sustain higher wattage for longer (yes, that is also part of "higher wattage"). If you are clipping due to the high peaks in music and movies then a higher-power amplifier may help. But I tend to think a lot of the difference is from expectation bias; you buy a new high-power amp and expect it to sound better. Many, many times I have heard "something new" when I changed a component only to go back to the old and discover it was there all along; I had ether forgotten or not focused on it before. Folk tend to listen more critically when something changes, with the expectation of sonic differences from that change, and that extra focus helps identify "new" things that were often there all along. Like tighter bass or silkier highs. Blind testing can be very revealing and vexingly humbling at the same time. At 1 W most of the time a 10 W and 100 W amp will sound the same except the 100 W amp is likely to be a little noiser (higher gain is needed to generate those extra watts from the same input signal).

Volume is a sneaky thing. If you just bump the volume 1 dB whilst watching a movie you'll hardly notice. If you compare two components and one is just a fraction of a dB louder, then the louder one invariably sounds "better". That is one of the great sales gimmicks; make the more expensive component just a hair louder, and it will sound better every time, whether it really is or not.

I consider loudness curves a separate issue; read the equal-loudness curves article on Wikipedia for an intro. Yes, at most levels much more power is needed by bass (LF) signals than by the midrange, but that goes back to how much power you need to listen in your room to your speakers at the level you want. And as Amir implied the power needed also depends upon the characteristics of the speakers. It's complicated.

HTH - Don
 
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garbulky

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#19
FWIW, I was always curious about how much I actually consumed. So on my speakers during regular playback I was consuming less than a watt using the meters on Mcintosh amps. Then on loud music the meter didn't move past I think 3 watts. My average listening level is in the low 70 db's @ listening position with peaks at about 80 db.
 

AnalogSteph

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#20
It should be mentioned that analog VU meters (a) are rarely calibrated accurately (and how could they know about speaker impedance anyway?) and (b) are far too slow to follow fast transients. Good as a rough indication of average levels, but you better keep a proverbial salt shaker handy.

In any case, any two amplifiers that provide maximum desired peak output amplitude at
* negligible distortion
with
* negligible noise
* flat frequency response
* good channel separation
* identical (or negligible) output impedance
are going to sound identical, no matter the extra headroom remaining beyond the level required. (Mind you, that's quite a number of ifs, and I haven't even qualified what this would mean in numbers yet.) Also see the Carver amplifier challenge from the '80s.

In a decently live room, 2x 1 W from 85 dB SPL / W / m speakers (a number that is slightly below average but not very much so) would produce ~85 dB SPL at typical listening distances of ~3 m. A fairly loud but by no means unreasonable level. Add 17 dB of crest factor, and we need a 50 Wpc amp. That's 102 dB SPL... more conservative estimates tend to go up to 110 dB. That would mean 316 Wpc instead. It goes without saying that the speakers would have to be able to take quite a beating then. You would probably rather want to stay away from such an unfavorable combination unless building a sub or anything else that's size-constrained. (Portable speakers tend to use all kinds of EQ and compression trickery to wring anything resembling decent levels out of what is often 75-80 dB/W/m or below.) In any case, this should probably make it clear why amplifiers rated 50 Wpc to 250 Wpc are common in the hi-fi realm.
 
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