Speaker sensitivity, amp power calculation and bass management

[Kegemusha]

It is confused, but it has to depend on the distance also. My room is 19m2, and I listen at 3,8m, my speakers are 88db/4 Ohm.
I had an emotiva amp 80W class AB and now I have another class AB 20W. At this distance I cant listen more than around 80-85dB, maybe I have sensitive ears
But to me 20W is more than enough and the volume is around 11 O'clock. I do have a DAC/Preamp at max volume on the other hand.

So I can understand when people wonders how many watts are enough I still not sure but some 50W could be more than enough for many.

 

[EdTice]

It is confused, but it has to depend on the distance also. My room is 19m2, and I listen at 3,8m, my speakers are 88db/4 Ohm.
I had an emotiva amp 80W class AB and now I have another class AB 20W. At this distance I cant listen more than around 80-85dB, maybe I have sensitive ears
But to me 20W is more than enough and the volume is around 11 O'clock. I do have a DAC/Preamp at max volume on the other hand.

So I can understand when people wonders how many watts are enough I still not sure but some 50W could be more than enough for many.

You are not confused at all. 85db is the THX standard for movie theaters. When you say 85db, do you mean that it says 85db on the dial or did you measure it with an SPL meter? The dial may or may not be accurate but if its as loud as you are comfortable we will assume that it's 85db.</p>

The reason that you might need more power is that sound is a distance-squared property. If you sit twice the distance away, you need 4x as much power! Also the decibel scale is logarithmic. Assuming I did the math correctly in my head, you would be using 2watts to listen at 85db. However, the THX standard says you should be able to go to 105db (85db+20db) for the very loud scenes such an explosion. Loudness is a logarithmic scale and to get 20db higher (4x as loud), you need 100x the power! If you don't have that much power, the sounds effect won't be as loud and will get distorted. But it also wont hurt your ears! For many people that's a good thing. It takes much more power to make the loudest sounds so if you really want to hear at the same volume as a theater, you need a lot of extra power in the amplifier. This also means that if the amplifier is exactly the right size for the room, you will normally be running at 1% of the maximum power. </p>

If you look at all of Amir's reviews, he always measures SINAD at 5watts even when dealing with an amplifier that can produce hundreds of watts. The reason for this is that, most of the time, you will be listening with such little power and the headroom is only needed for brief periods of loud sounds. An amplifier that can produce a 70 SINAD at 5 watts and a 105 SINAD at 500 watts isn't very useful. On the other hand, an amplifier with a 105 SINAD at 5 watts and a 60 SINAD at 500 watts would probably sound great and work well for just about anybody. My space is about twice as large as yours and I once estimated that when my wife is home we listen at about 1 watt and when she's not home, I listen at about 10 watts. The extra power for the amplifier is only there so that you will jump out of your chair when somebody plays a loud bass note or there is a gunfire scene. </p>

Note that the 85db/105d is the "THX" standard for movie theaters so home theater setups try to be able to reproduce it. But you will also notice that most people don't like to listen that way at home. The AVRs all have a "dynamic range compression" feature so that you can still hear the whisper scenes in the movie even if the dishwasher is running in the next room without risking damaging your hearing or scaring your children during a loud scene. </p>

The way that AVRs are actually used tends to be much different than how they are marketed. Fortunately Amir tests for what's actually important.</p>

In a small room especially you want an amp that sounds good at lower power not one that can get insanely loud.

 

[Jdunk54nl]

Also note, that a lot of those explosions are happening at lower frequencies where your subs are taking over, so you only really need that power there, and those amps are fairly cheap for subs and distortion/SINAD is even less important.

If you don't have an active sub, it is an easy way to get the power you need for the big explosions/crashes.

I've got about 550 watts on my sub on a crown xls 1502 amp. It has the meter on it, and for very loud scenes (my wife and I literally can't talk to each other without having to turn the volume down), the clipping light never illuminates and it is VERY rare for the lights to go above the second light illuminating, which is the -20db light. The -10db light sometimes illuminates but not often.

Getting to 105db on those frequencies is much easier.

I actually measured the other day with my office sub on and off, with the sub off, about 75db was loud listening, that corresponded to 80-85db with the sub turned on. This was using REW and DB z weight. I checked with my decibel x app and verified the results with z weighting on the app.

 

[EdTice]

Also note, that a lot of those explosions are happening at lower frequencies where your subs are taking over, so you only really need that power there, and those amps are fairly cheap for subs and distortion/SINAD is even less important.

If you don't have an active sub, it is an easy way to get the power you need for the big explosions/crashes.

I've got about 550 watts on my sub on a crown xls 1502 amp. It has the meter on it, and for very loud scenes (my wife and I literally can't talk to each other without having to turn the volume down), the clipping light never illuminates and it is VERY rare for the lights to go above the second light illuminating, which is the -20db light. The -10db light sometimes illuminates but not often.

Getting to 105db on those frequencies is much easier.

I actually measured the other day with my office sub on and off, with the sub off, about 75db was loud listening, that corresponded to 80-85db with the sub turned on. This was using REW and DB z weight. I checked with my decibel x app and verified the results with z weighting on the app.

Indeed, the question I was answering was "why would anybody need more than about 100 watts" and the answer seems to be that the vast majority of people don't which is why most integrated systems have ratings around 100W! I wish that, when I was even newer at this, I had totally ignored power ratings and focused 100% on how to get good sound out of the L/R/C.

 

[Jdunk54nl]

Indeed, the question I was answering was "why would anybody need more than about 100 watts" and the answer seems to be that the vast majority of people don't which is why most integrated systems have ratings around 100W! I wish that, when I was even newer at this, I had totally ignored power ratings and focused 100% on how to get
good sound out of the L/R/C.

Totally agree, the more I learn about how much power actually gets sent to speakers, the more I realize most need very little to get very loud! It’s the same with car audio (how I got started in audio). People put 500w amps on tweeters...then minimize gains and turn down even farther in the dsp to get the 1-2 watts needed.

 

[solderdude]

I see no objections to having too much power on tap. Even when one normally doesn't use more than 1W.
Would be more bummed when I had to little of it and sound turns 'nasty' before it becomes too loud.
The whole issue here is that if you want to go just a little louder than loud and don't want it to turn 'nasty' sounding you need a whole lot more power.
Going from 70 to 150W seems a lot but is just 3dB louder which isn't a lot.
For this reason a lot of people feel their 5x40W is enough but those that have slightly less sensitive speakers or a bigger room to fill may need 5x200W.

 

[EdTice]

I see no objections to having too much power on tap. Even when one normally doesn't use more than 1W.
Would be more bummed when I had to little of it and sound turns 'nasty' before it becomes too loud.
The whole issue here is that if you want to go just a little louder than loud and don't want it to turn 'nasty' sounding you need a whole lot more power.
Going from 70 to 150W seems a lot but is just 3dB louder which isn't a lot.
For this reason a lot of people feel their 5x40W is enough but those that have slightly less sensitive speakers or a bigger room to fill may need 5x200W.

I don't think that there is any objection to "too much power" (If you've ever watched the TV show "Home Improvement," "more power" is all the rage!) The challenge is that most of us have finite amount of money and neither power nor sound quality come cheap. So most of us have to make some sort of trade-off. There are people out there who like to listen at reference. I'm currently listening at -57db as I type. I have a device that measures power consumption but my guess is that I'm not using a measurable amount more than what the AVR uses turned on with no content playing. It's not that some people don't need more power (you clearly do). The statement here is that, for many people, more power is either not helpful or not as helpful as lower distortion at low power. As the vast majority of casual users play both movies and music with their home theater setup, it's usually the former that suffers.