Higher Watt vs Lower Watt Amplifier, listen at the same loudness. Is there any benefit?

[Denman]

A clear explanation to your question can be found here:
https://www.gcaudio.com/tips-tricks/the-interrelationship-of-speakers-and-amplifiers/

In short, the power needed by a speaker is determined by the sounds it needs to reproduce.
An average volume is not indicative of the power your speaker might need to be able to reproduce peaks (peaks in low frequencies usually, where more power is needed to move the speaker coil) in the music.

How much power you need is up to your gear and your personal preference of the produced sound.

 

[EB1000]

It depends on many factors, like how much headroom you got left, and the dynamic range of the music played. Also, the class of amp matters. Class-D amp behaves differently than class-AB in terms of THD vs output power. At low power output (low voltage magnitude and low modulation depth), the class-d THD is relatively high, at some medium power, THD becomes optimal, and then at high power, it deteriorates again. This is because of two main factors:

1) THD is defined as the sum of all unwanted harmonics (squared) over fundamental ( wanted) harmonic. Hence, the lower the output power, the lower the magnitude of the denominator, hence the higher the THD.


2) At higher magnitudes, due to non-linearities of the low pass filter's components, as well as saturation effect due to over modulation, the unwanted harmonics content (nominator) increases, resulting in higher THD.

Therefore, THD in class-D has a sweet spot. This is why class-D is better suited for low-efficiency speakers because this will draw more power at lower volume levels, which helps the amp approach its THD sweet spot...

We see the same behavior at our lab in my work when evaluating our multilevel power inverters, which are essentially high power class-d amps for a 50 or 60Hz sinewave...

Edit:

Attached is THD vs power of a class-D (ICEpower 125ASx2). Notice the sweet spot at 50W (its a 125W into 8 ohms amp).

To overcome this limitation with our power converters, we alter the output power (magnitude) by operating the inverter at its sweet spot, and adjusting the output voltage by a pre-converter made od a DC-DC converter which can have its output voltage varied to adjust the ac voltage at the inverter's output.

 

[LTig]

I thought it's +6db for double the perceived loudness which equals 4 times the power.

Depends on the frequency. Look at the Fletcher-Munson equal loudness curves. At medium frequencies the curves are more apart, hence 10 dB = 10 times the power for perveived double loudness. At very low frequencies the curves are closer, hence 6 dB = 4 times the power for perveived double loudness.

 

[LTig]

Hi, thanks for the input,
For more specific example. Currently I'm using 70w DIY Nap140 clone amp, with DIY Peerless speakers.
Planning to try Class D amp using IcePower or NCore module.
For example,
- NCore NC122mp amp (75w/ch at 8 ohm)
- NCore NC252mp amp (125w/ch at 8 ohm)
Would the NC252mp will be better than the NC122mp at the same loudness?

Not the answer to your question, but anway: The NC122mp might have less peak power than the NAP140 clone. Most class D amps have regulated power supplies so peak power is not higher than continuous power. So replacing the NAP140 clone by NC122mp you may end up with less peak power.

 

[Frank Dernie]

30-50% volume

The position of the volume control is a poor indicator of how much power you are using since it is a log controller (usually) and max power with an input receiving the rated input sensitivity is often around 1 o'clock on the volume control, not maximum (to allow for sources with lower outputs).

 

[PolkFan]

10 is considered to be double but its not a standard but for me 6db is for sure not double.

 

[PolkFan]

Ok.
No one knows for real.
Thank you.

Doubling the amplifier power increases the acoustic power by 3dB.

We do know that for sure and 3db is not twice as loud either is 6


This is why chasing for more power isn't as important as getting more sensitive speakers.

 

[PolkFan]

The 120W amp could go 2.3dB louder.
Here is the thing about amp specs though.

It could well be that the 70W spec'd one is specified at a low distortion for instance and such amp could have more 'peak' headroom (which is what music is about) and could well offer more output power.
The 120W amp may well have been spec'd at say 1% distortion and have little dynamic headroom.
In such a specific case there could not be any audible differences at all.

Could also be that the 70W amp is absolute max rated and doesn't have extra peak headroom and the 120W is spec'd conservatively and can reach much higher peak levels.

So... hard to tell but going of specs the 120W and 70W are not worthwhile differences.

Besides, as the question stands when used below 50W there are no differences, assuming both amps are competently designed.
It could well be that one of them is of a cheap and crappy design.

Agreed the biggest joke in the industry is receivers with their 100W rating per channel most of the time its 100 watts for a SINGLE channel not 5 or 7 used to just be able to look at the power supply and see what it can really do but now its not that easy.

 

[A800]

Doubling the amplifier power increases the acoustic power by 3dB.

We do know that for sure and 3db is not twice as loud either is 6


This is why chasing for more power isn't as important as getting more sensitive speakers.

Agreed.
Sensitivity is king.

 

[Blumlein 88]

For the power thing, don't get confused with voltage.

Doubling voltage is 6 db.
Doubling power is 3db.

Why? Note if you double voltage, you also double current. As power is voltage x current, then doubling voltage quadruples power. Increasing voltage 3 db (1.41x) increases current 1.41x which means you doubled the power.

So 10 db increase on a speaker is 10x the power (and 3.16x the voltage).

Generally it is agreed increasing level by 10 db is going to sound twice as loud. But it does vary and quite a few people seem to hear 6db as twice as loud.

 

[mhardy6647]

I think that's why they call it loudness.
As opposed to brightness.
In my day, TVs has brightness controls.
I used to turn them up, but it never seemed to help the programs any.

Most hifis never had brightness controls -- but now folks use wires cables interconnects.

Agreed.
Sensitivity is king.

About 104 dB per watt at 1 meter here. Why make the amplifier do the heavy lifting?


EDIT: Actually, my snark notwithstanding, there's a simple answer to my rhetorical question. It's cheap and easy to make a powerful amplifier of good quality. It is difficult and expensive indeed to make a high sensitivity driver of good quality.

 

[A800]

About 104 dB per watt at 1 meter here. Why make the amplifier do the heavy lifting?

Nice.
Exactly.
99 dB/w/m here.

 

[beefkabob]

Every amp has different sweet spots of power delivery. So distortiono on an amp depends on how loud you listen. But really, you're probably only going to notice a problem if the amp is clipping or broken. So all things being equal, just go for more power to make sure there is less a chance of clipping. Unless you listen real quiet.

 

[beefkabob]

Rated or actual efficiency? There's a difference.

 

[A800]

Yes.
Measured average.
Anything else is useless.

 

[PolkFan]

Every amp has different sweet spots of power delivery. So distortiono on an amp depends on how loud you listen. But really, you're probably only going to notice a problem if the amp is clipping or broken. So all things being equal, just go for more power to make sure there is less a chance of clipping. Unless you listen real quiet.

Something i tend to notice on AVR's is about the 2/3 rule once you get over lets say 70% you start to lose "bass" and it just gets sloppy.

To add more like some of the previous statements its not so much about the same loudness as lower frequency's need more power then higher ones. I'm out of my scope here but i'm not even sure smaller speakers use less power i thought i read a article awhile ago stating that they can use more power which doesn't make sense to me at all.


In multi-channel systems its best to use a 80hz crossover anyways its good for the amp its good for the room you are in and its recommended by THX.

I don't even care if you have 20 inch speakers that doesn't change what i said above

 

[Blumlein 88]

snip
To add more like some of the previous statements its not so much about the same loudness as lower frequency's need more power then higher ones. I'm out of my scope here but i'm not even sure smaller speakers use less power i thought i read a article awhile ago stating that they can use more power which doesn't make sense to me at all. snip

There is a relationship between low frequency response, box volume and efficiency for a given sized woofer. With the proper driver and porting it is possible to get a small woofer to respond down to low frequencies at the cost of efficiency. Or using the same sized woofer you could use a bigger box to the same low frequency at higher efficiency. Usually mid-ranges and tweeters are more efficient than woofers. So woofer efficiency more or less sets the efficiency level for the whole speaker.

 

[mhardy6647]

DSC_8282 (2) by Mark Hardy, on Flickr

Altec 515B
JBL 2441 on EMILAR EH-500-2
B&C DE35
All first order XO

no, haven't measured 'em. Maybe only 100 or 101, but fit for purpose.

oh, plus a semi-DIY powered subwoofer (2 x 15" woofers) with DSP.

DSC_0484 (2) by Mark Hardy, on Flickr

for completeness, here's the other - bottom mounted - driver

DSC_8307 by Mark Hardy, on Flickr

 

[A800]

So woofer efficiency more or less sets the efficiency level for the whole speaker.

Exactly.
That's why you should use them in multiples.

 

[Sal1950]

For the power thing, don't get confused with voltage.

Doubling voltage is 6 db.
Doubling power is 3db.

Why? Note if you double voltage, you also double current. As power is voltage x current, then doubling voltage quadruples power. Increasing voltage 3 db (1.41x) increases current 1.41x which means you doubled the power.

So 10 db increase on a speaker is 10x the power (and 3.16x the voltage).

Generally it is agreed increasing level by 10 db is going to sound twice as loud. But it does vary and quite a few people seem to hear 6db as twice as loud.

There he goes with all that math again. BLAH