Question re Wattage: How much does it really matter?

[Flip69]

Did a quick search for threads on this topic, but did not find one. Feel free to simply point me in that direction if you know of one. Also, not sure if this is the best forum for this post, but here goes.

I had a guy come in to look at a Pioneer SX-1250 I had restored. He did not buy it because it was not noticeably louder than the SA-9500 he already owned. That potentially triggers an entirely different discussion. However, it got me thinking about watts versus volume. When I did some quick research online, I found that in a typical system with an 8 ohm load, doubling wattage produced a 3 decibel increase in volume. According to the article I found, 64 watts creates 108 decibels, 128 watts creates 111 decibels, 256 watts creates 114 decibels, etc. The article said a 10 decibel increase sounds twice as loud to the ears. I take that to mean that a 3 decibel increase equates to a 30% increase in volume. So, the 160 watt SX-1250 is 30% louder than the 80 watt SA-9500 at max volume.

I am sure my analysis is overly simplistic. However, the point remains: more wattage does not necessarily mean that much more volume.

So, what does more wattage do? I understand the issue of low efficiency versus high efficiency speakers. Obviously, you need enough juice to power your speakers properly. I also understand that a small room has different needs than a big room.

But what if all of the various factors are equal? I have a Marantz 2220B in one of my systems, played through ADS L710 speakers. The room is small, and the speakers are relatively efficient. The 2220B sounds good, very good in fact, at least to my ears. I have a 2270 that I recently finished restoring. I am thinking about substituting it for the 2220B in that system. Before deciding, I will do a side by side listening test. How much impact, if any, will the increased wattage of the 2270 play in whether it sounds better than the 2220B?

In other words, if all other things are equal, will a higher wattage receiver of the same quality always sound better than a lower wattage receiver? If the 2270 sounds better, is it because of the wattage, or is it because of other factors (e.g., better circuitry, better design, better transformer, etc.)? I expect it is probably some of all of the above. I have read comments that the higher wattage receiver will drive the speakers more efficiently, which will produce a better sound. Is that true?

Looking forward to your comments.

 

[BilboBaggins]

It all depends on the amp and the speakers synergy!

If you plug in infinity kappa 9s, the sx-1250 receiver will be straining at times as you turn it up. Plug in Klipsch Cornwalls and it will sound louder at the same volume level.

That’s a simplistic way of saying it’s much more complex. I’ve been looking for something over the years and I’m now starting to think we either don’t consider certain specs to be important, but they are, or that we don’t know what to measure yet to get a definitive answer, if it is even possible!

 

[whoaru99]

A 3dB increase sounds only a small bit louder, not roughly 1/3rd.

3dB = 2x more power. 10db = 10x more power.

So, 2x more power is only small increase in perceived SPL. 10x more power to be twice as loud, all other things equal.

160 watts is not going to sound much louder than 80 watts in terms of flat out volume. What you gain with 160 watts is the ability for the sound to remain "clean" at a volume where the 80 watt unit may end up sounding a bit harsh and strained.

In terms of sound quality, power output is only a major player when you don't have enough to cleanly reach the volume level you are trying to achieve.

 

[Rockon1]

Transients (peaks) draw a lot of power-especially bass. If you play your music loud a healthy reserve of power is essential...aka headroom. Bob

 

[BilboBaggins]

A 3dB increase sounds only a small bit louder, not roughly 1/3rd.

3dB = 2x more power. 10db = 10x more power.

So, 2x more power is only small increase in perceived SPL. 10x more power to be twice as loud, all other things equal.

160 watts is not going to sound much louder than 80 watts in terms of flat out volume. What you gain with 160 watts is the ability for the sound to remain "clean" at a volume where the 80 watt unit may end up sounding a bit harsh and strained.

In terms of sound quality, power output is only a major player when you don't have enough to cleanly reach the volume level you are trying to achieve.

Much better said, and if you look at the efficiency of my 2 examples you will see a difference, that will account for a difference in perceived volume, just by changing the speakers.

 

[BilboBaggins]

Oops! I choose those infinitys in error! I should have double checked the specs. A better comparison is Kef 105 at 86 dB vs Klipsch Cornwall at 98.5 dB.

 

[darkblue94]

it will sound louder at the same volume level.

That's impossible. If it's at the same volume level then the loudness (synonymous with volume level) will be the same. Where the volume dial is set on one amp has no direct relation to where the other amp's dial is set.

 

[swechsler]

Remember that the dB scale is exponentially related to the electrical output power. So if 1 electrical watt produces 90dB output, 10 watts will produce 100dB (twice as loud), 100 watts will produce 110 dB (4 times as loud), etc. That's the most simplistic explanation and doesn't take into account headroom, distortion, etc.

 

[BilboBaggins]

That's impossible. If it's at the same volume level then the loudness (synonymous with volume level) will be the same. Where the volume dial is set on one amp has no direct relation to where the other amp's dial is set.

You are right.

Let me reword this. At the same position on the knob of the amp.

 

[swechsler]

Oops! I choose those infinitys in error! I should have double checked the specs. A better comparison is Kef 105 at 86 dB vs Klipsch Cornwall at 98.5 dB.

I don't think any receiver would be happy with Kappa 9s. Not even a Sansui G22000.

 

[BilboBaggins]

And yet, interestingly, the 9s have an efficiency of 102 dB!

 

[shelly_d]

The first 3 posts just about covered it. I would like to add a bit about sound quality and provide a bit of math that might help with the numbers and looking at the power ratings.

First is the "other" factors that play into how well the amp behaves with a pair of speakers. The first thing to know is that there are some things that are generally true but not always true. Amps with equal power and noise specs but different distortion levels, the lower distortion level will likely sound more transparent. That is, more likely to sound like the source material, without alteration or coloration. The amp with lower noise specs is likely to sound cleaner then one with higher specs, but you need to know how to read them to know what they say. Some measure the noise below 1 watt and some measure below full output. You can convert one to the other to compare but the two are not directly comparable. With all other factors being equal, a wider bandwidth (say 10 to 25K +/- 3dB) is more likely to sound better then a more narrow one (20 to 20K +/- 3dB).

Having said that, none of these things are always true. This is because some speakers with complex crossovers can present very complex loads to the amps with many inductive and/or capacitive elements that some amps can drive with smoother responses then some others. With speakers like that, if may be a challenge to get a pairing that you are happy with.

Now on to how to guesstimate your power needs. Start with knowing your real volume needs. You hear about listing at 100 or 105 dB at home. I spend $10 on Radio Shack sound level meter and used it when listening at the "MY GOD HOW LOUD DO YOU WANT THAT!" Level. (I wrote that like I was shouting because at that level that is exactly what we need to do to talk to each other.) When I used the meter I discovered the average level was 85 dB. Indeed with a bit of searching online you find references that mention that at 85 dB, you need to shout to be heard by someone right next to you.

Now with that in mind, lets look at how much power you need. My speakers are about 86 dB/watt/meter. So I will get to that 85 dB level with only 1 watt. But that is not all of it. Music is dynamic, it has loud and soft passages. The loud parts can reach twice as loud (10 dB louder). That means you are up to 20 watts. A very well recorded piece might have even more dynamic range, perhaps another 3 to 6 dB. That now puts you at 40 to 80 watts. This is still at an average listening level of 85 dB but you can now handle peakes up to 101 to 104 dB before distorting. Then you want a cushion between the expected peaks and the clipping level of your amp. Call that 3 dB. You are now at 80 to 160 watts.

As you can see, loud escalates power needs pretty fast.

Hope this is useful for you.

Shelly_D

 

[sKiZo]

Lot depends on what sort of watts you're playing with. Tube watts tend to stay much more civilized as you crank the amp, as they "soft clip" instead of throwing harsh crunchy stuff at your speakers and ears.

And ya - it's all about headroom. Instantaneous transients can and will soak up every watt you'v egot in your arsenal, even at relatively low average volume settings. Start playing with dynamic expansion and sub synthesis, and the demands go up exponentially.

 

[E-Stat]

In other words, if all other things are equal, will a higher wattage receiver of the same quality always sound better than a lower wattage receiver?

Sometimes the reverse is true. Quantity and quality are not the same measure.

I'll take a 30 watt class A Pass Labs power amp over virtually any receiver in terms of quality.

 

[Jeff K]

You should be at least as concerned about whether the speaker presents a complex load and how a particular amp will handle it. A really strong amp that doesn’t do well when impedences fall below below 4 ohms can cause problems. Some amps can handle 2 ohm loads. Others overheat and distort.

 

[Tedrick]

102 dB for Kappa 9's is a misprint. The old Infinity website lists sensitivity as 89 dB, which seems far more realistic given that they are a sealed box design.

 

[swechsler]

89dB is also what the Kappa 8s are rated at, so I'd say that's the correct number.

 

[Drum]

A few other things to consider.

You generally have two speakers so that is like doubling the power (or adding 3 db). So if 1 speaker is 90 db at 1meter with 1 watt then 2 speakers are 93 db.

Sound diminishes with distance. So if you have 93 db coming from your speakers at 1 meter, but you sit 4 meters away then it will not be as loud. The sound diminishes by 6 db for every doubling of distance. That 93 db becomes 81 db.

Another factor is room gain. Many efficiency ratings are done in anechoic chambers. Being in a room can make things louder - especially the bass. This is harder to quantify as rooms vary so much.

 

[toddalin]

That's impossible. If it's at the same volume level then the loudness (synonymous with volume level) will be the same. Where the volume dial is set on one amp has no direct relation to where the other amp's dial is set.

Actually, Bilbo is correct in that one set of speakers can sound louder at the same volume level, even when referring to volume in dB. Because of the F/M curve, a speaker that is heavier in bass may have the same dB at X feet (as measured on a sound level meter) as a speaker that is heavy in the midrange. But because the ear is far more sensitive in the midrange, this latter speaker will sound louder.

 

[bhunter]

I don't think any receiver would be happy with Kappa 9s. Not even a Sansui G22000.

Here's the Kappa 9 graph. A flat out nasty curve for all but the most robust amps. IIRC, an Apogee Scintilla went a bit lower.