How many watts do you need really

[Blue2kid3]

If my math is correct and it's 1 am so it probably isn't so that's why I'm here, to ask where I am going wrong.

I was thinking and busted out the calculator and paper.

Let's take the klipsch rp 8000f as those numbers are easy to work with (and a review is posted here)

It has a sensitivity of 92 db / 1 meter/ 2.83 V

We know the voltage and we know the resistance so let's error on the side of caution call it a 6 ohm load at 2.83v = 1.3 watts, now we really have better resistance than that at full fq response so we shall round to 1 watt.

So 92 db / 1 w / 1 meter

Now let's calculate an average listening distance from the front LCR say 4 meters to be safe. So we get 80 DB over 4 meters.

So are you telling me these klipsch speakers can hit THX reference level (75 DB) at an average if not further listening level at just one watt?!?

80db/1 watt / 4 meters above reference level without room gain factored in!

Please help explain where my math is off and if it's close does that mean most of us wouldn't need more than 20 - 30 watts per channel?

 

[Blue2kid3]

If you guys found this interesting thumb it up so maybe Gene will do a YouTube video about it as well I love his podcasts for my drive to and from work!

 

[PENG]

If my math is correct and it's 1 am so it probably isn't so that's why I'm here, to ask where I am going wrong.

I was thinking and busted out the calculator and paper.

Let's take the klipsch rp 8000f as those numbers are easy to work with (and a review is posted here)

It has a sensitivity of 92 db / 1 meter/ 2.83 V

We know the voltage and we know the resistance so let's error on the side of caution call it a 6 ohm load at 2.83v = 1.3 watts, now we really have better resistance than that at full fq response so we shall round to 1 watt.

So 92 db / 1 w / 1 meter

Now let's calculate an average listening distance from the front LCR say 4 meters to be safe. So we get 80 DB over 4 meters.

So are you telling me these klipsch speakers can hit THX reference level (75 DB) at an average if not further listening level at just one watt?!?

80db/1 watt / 4 meters above reference level without room gain factored in!

Please help explain where my math is off and if it's close does that mean most of us wouldn't need more than 20 - 30 watts per channel?

Just couple points:

-THX ref level is not 75 dB, it is 85 dB, and 105 dB for peaks
-For sensitivity, it is better to stick with XdB/2.83V/m instead of XdB/W/m

So in your example, that is, based on your calculated 80 dB at 4 meters for 1 W, it would be 100 dB for 100 W, or 105 dB for 316 W. That is, you need 316 W to avoid clipping at 105 dB SPL.

 

[highfigh]

If my math is correct and it's 1 am so it probably isn't so that's why I'm here, to ask where I am going wrong.

I was thinking and busted out the calculator and paper.

Let's take the klipsch rp 8000f as those numbers are easy to work with (and a review is posted here)

It has a sensitivity of 92 db / 1 meter/ 2.83 V

We know the voltage and we know the resistance so let's error on the side of caution call it a 6 ohm load at 2.83v = 1.3 watts, now we really have better resistance than that at full fq response so we shall round to 1 watt.

So 92 db / 1 w / 1 meter

Now let's calculate an average listening distance from the front LCR say 4 meters to be safe. So we get 80 DB over 4 meters.

So are you telling me these klipsch speakers can hit THX reference level (75 DB) at an average if not further listening level at just one watt?!?

80db/1 watt / 4 meters above reference level without room gain factored in!

Please help explain where my math is off and if it's close does that mean most of us wouldn't need more than 20 - 30 watts per channel?

First, the sensitivity spec uses the nominal impedance, so 8 Ohms is fine for most speakers. Second, using the Power formula from Ohm's Law (P=E²/R) with 8 Ohms comes to 1.001 Watt so you didn't need to do the mental gymnastics.

Speakers are tested in quasi-anechoic conditions and we listen in reflective rooms, so a 4 meter distance means that some of the energy will be reflected toward the listening position. Also, the 92dB sensitivity is for one speaker and when you add a speaker & another Watt of amplification (applies only to doubling the speakers and channel), you need to add 6dB, even without reflections. Let's assume the system has only the LCR, so add another 3dB for power and somewhat more output because of the one additional speaker, making it roughly 99dB/W/M. Move 4 meters away in an anechoic room and you'll have roughly 88dB when all channels are driven by 2.83V but you can safely add 3dB from reflections.

Your question is pretty close to the actual need, but a few things can make it necessary to be able to have access to more power- source levels and recordings aren't totally consistent and as soon as you add one person to the room, some of the energy is absorbed. Add more people, pets, furniture, etc and the SPL (perceived and actual) decreases.

 

[lovinthehd]

You can also just use this spl calculator http://myhometheater.homestead.com/splcalculator.html

Generally no, most people don't use a whole lot of power at normal listening levels.

 

[highfigh]

You can also just use this spl calculator http://myhometheater.homestead.com/splcalculator.html

Generally no, most people don't use a whole lot of power at normal listening levels.

I think it's safe to say that if the output power can be converted to whole numbers for Horsepower in systems for small rooms, it's getting close to 'enough'.

For those who don't know, 746 Watts= 1 Horsepower. For those more familiar with HVAC, 33,000 btu = 1 HP.

 

[Pogre]

You can also just use this spl calculator http://myhometheater.homestead.com/splcalculator.html

Generally no, most people don't use a whole lot of power at normal listening levels.

Heh. I almost posted this link too but figured I'd better scroll down because someone probably already did.

Yes, this is something we tell folks here all the time. Most of us only use a couple of watts most of the time. It's those occasions when you crank it up and ecounter 10 or 20 dB peaks, then that reserve power comes in handy. I like it loud sometimes and sit 15' from my speakers so I like knowing I have the power on tap, tho I don't think I've ever exceeded too much more than 100-150 watts.

 

[BMXTRIX]

Anything less than 1.21 Jiggawatts is just not enough.

 

[BoredSysAdmin]

Anything less than 1.21 Jiggawatts is just not enough.

http://imgur.com/qeiKItv

 

[Hetfield]

What the hells a jigawatt!

Sent from my Pixel 4 XL using Tapatalk

 

[Pogre]

What the hells a jigawatt!

Sent from my Pixel 4 XL using Tapatalk

Don't tell me you've never seen Back To the Future!

 

[Hetfield]

Don't tell me you've never seen Back To the Future!

Yes of course, that was the joke. Marty says "what the hells a jigawatt"!

Sent from my Pixel 4 XL using Tapatalk

 

[Audioluvr!]

You only need 1-2 watts to enjoy music but you'd better have at least 200 amps of reserve,

 

[j_garcia]

1 would be for average listening, and I would say that is more like 5-10 average. When you get a big peak with a lot of different sounds across the spectrum and you have it cranked up loud, you can't exactly predict how much you will need. You will certainly know it when you don't have enough to handle those peaks for a given SPL though.

 

[highfigh]

I prefer to state the power of my system in units that are different- Joules, btu, Horsepower, etc.

I think I may switch to Erg/sec and I think manufacturers/Best Buy should follow my lead if they want people to see a really large number- rather than showing 850W on the card in front of their receivers, they would show 8.5 Billion Erg/sec.

 

[PENG]

It doesn't even matter what power/energy unit you use, the thing that most Bestbuy reps may not know that even if their demo A-S1200's so called "wattmeter" shows say 150 W of peak deflection, we have no way of knowing how much of that was pumped into the speakers and how much was dissipated in the power amp because for electromagnetic moving coil loudspeaker (just as an example), it would depend on the phase angle, among other factors, and the phase angle would vary continuously when the speaker is playing music instead of a test tone. Depending on many things, at a given moment, the speaker could be produce the loudest spl yet consuming not much "power" as most of the "power" could be dissipated, or wasted in the amp's outage stage, making heat..

"Power" amps would have been better specified in rated current at rated voltage at a given load phase angle, not perfect, but it would still be much better than in rated power into a given impedance magnitude without a given phase angle.

The question how much power you need keep coming up, yet to answer such question one has to know the conditions of use, and if only part of the information is available one can answer by assuming the best, likely or worst conditions? I don't know but I would base on whatever info is given, and then build in a safety factor of my choice with my suggested number.

 

[Gmoney]

You only need 1-2 watts to enjoy music but you'd better have at least 200 amps of reserve,

LOL. I was going to post up something alone the line of what You posted. You beat me to it, Better to have more power than not.

 

[highfigh]

It doesn't even matter what power/energy unit you use, the thing that most Bestbuy reps may not know that even if their demo A-S1200's so called "wattmeter" shows say 150 W of peak deflection, we have no way of knowing how much of that was pumped into the speakers and how much was dissipated in the power amp because for electromagnetic moving coil loudspeaker (just as an example), it would depend on the phase angle, among other factors, and the phase angle would vary continuously when the speaker is playing music instead of a test tone. Depending on many things, at a given moment, the speaker could be produce the loudest spl yet consuming not much "power" as most of the "power" could be dissipated, or wasted in the amp's outage stage, making heat..

"Power" amps would have been better specified in rated current at rated voltage at a given load phase angle, not perfect, but it would still be much better than in rated power into a given impedance magnitude without a given phase angle.

The question how much power you need keep coming up, yet to answer such question one has to know the conditions of use, and if only part of the information is available one can answer by assuming the best, likely or worst conditions? I don't know but I would base on whatever info is given, and then build in a safety factor of my choice with my suggested number.

Did I really need to put a smiley face on that post?

People ask "How many Amps does this put out", How much Power does this have" and other questions that prove they don't understand this stuff- how would you get them to understand what you propose? They don't know the difference between Voltage and Current, don't understand impedance, phase angle or anything else- as much as I hate the thought of it, some rating system needs to be used that assigns a number, from people who understand it, to do the work for people who want something. The reality that people can't bring themselves to learn something is pathetic. I get that some people just can't grasp it, but many who should be able to won't bother. It's very similar to people who ask questions online- they don't bother to look it up, so they go through the time and effort to set up an account in a forum and ask someone to find it. It's the whole reason 'Here, let me google that for you' exists.

 

[PENG]

OP's questions have been answered, so just teasing and having fun..

 

[highfigh]

OP's questions have been answered, so just teasing and having fun..

I'm surprised nobody answered with "MORE!".