Calculations says I need a power amp with 250 watts for KEF R11.

[TLS Guy]

How about forget what I said, but take a look of what manufactures said about power requirement, handling etc.etc., keep in mind this is one area they don't typically exaggerate their rating because of warranty concerns. If you have to time to read them all, you will conclude as I have, that it really depends, so imo if we will safe to not make general blanket statements.

Enjoy!

Dali:
How power handling affects your loudspeakers (dali-speakers.com)

The power handling of a loudspeaker is very much dependent on the type of music reproduced. Since a music signal simultaneously consists of a broad range of frequencies, it is not possible to define maximum power handling in meaningful terms.

In the real world, large amounts of clean, un-distorted power from a big amplifier is better than the distorted output of a small amplifier pushed beyond its limits.


KEF
Recommended Amplifier Power (kef.com)

Rule of Thumb:

In the real-world, it’s best to ignore the low-end spec. That’s shown to show the minimum amount of power needed to move the voice coils in any appreciable manner.

A good match is an amplifier capable of producing between 60% and 110% of the recommended maximum.

For example, the R5 shows a Recommended Amplifier Power of 15 to 200 WPC. A good match for this speaker would be an amplifier that produces between 120 Watts per Channel ((200x.6)*100) and 220 WPC ((200x1.1)*100). In terms of performance and damage potential, an amp rated lower than 60% of maximum poses far more danger to the loudspeaker than an amp rated above the maximum.


Paradigm:
What amplifier would you recommend for my Paradigm speakers? : Paradigm Support

What amplifier would you recommend for my Paradigm speakers? Print
Modified on: Thu, 6 Sep, 2018 at 3:50 PM

For the best pairing we recommend using Anthem amplifiers.

Amplifier Distortion — The #1 Culprit! When choosing an amplifier or any similarly high-quality amplification, always select an amplifier with a power rating greater than that of the speaker. Using a 100 watt per channel amplifier on a 50 watt speaker allows the amplifier adequate headroom in order to provide a distortion free signal. Conversely, using a 40 watt per channel amplifier on a 50 watt speaker limits the amplifier’s headroom. This causes the amplifier to enter its distortion level much sooner, potentially damaging the speaker.


Klipsch:
Choosing the Right Receiver/Amplifier – Klipsch

Choosing the Right Receiver/Amplifier
Follow
To give you the best balance of power and performance, select an amplifier or receiver that delivers continuous watts (many times also referred to as “RMS”) in accordance with the speaker’s continuous power handling rating.
For example, a Klipsch RP-8000F is a floorstanding speaker with a nominal impedance of 8 Ohms, rated at 150 Watts continuously. So, any receiver or amplifier that delivers right around 150W per channel at 8 Ohms with full frequency bandwidth (20Hz - 20,000Hz) would be a good match.
NOTE: To ensure you do not damage your speakers, Klipsch recommends the AV receiver or amplifier you choose is no less than 80% of the recommended continuous power handling, and no more than double the continuous power handling. For example, the RP-8000F requires an AV receiver with a bare minimum of 120W per channel (8 ohms), and no more than 300W per channel (8 ohms).


I can keep searching for more, I bet you will see the very similar kind of messages from manufacturers, and finally if all fails try Audioholic.com:

The Truth About Matching Amplifier Power to Loudspeakers | Audioholics

May also be interesting see the spectrums of musical instruments:
The Frequencies of Music - PSB Speakers

View attachment 55253

Those are just the fundamental frequencies, there will be huge second harmonic content also which if the fundamental X2. When I look at my DAW metering you can see the power distribution on a moment to moment basis, and the power band is primarily between 80 Hz and 5 KHz.

I have posted this video before, of my DAW playing back one of my recordings.

If you look a the meters on the lower right and the lower second from right in particular, You will see what I am talking about is correct.

That is why on a budget, a two way speakers is a much better bet. A truly powerful three way speaker is a formidable affair and most in the commercial market are just not up to the job.

 

[fmw]

Allow me to fix your calculations. The speaker system is rated at 90db. That means it will produce an SPL of 90db with 1 watt at a 1 meter listening distance. 9 db more SPL would require 17 watts at 1 meter and a bit more since you are listening at 1 1/2 meters. How much overhead do you think you need?

 

[PENG]

Those are just the fundamental frequencies, there will be huge second harmonic content also which if the fundamental X2. When I look at my DAW metering you can see the power distribution on a moment to moment basis, and the power band is primarily between 80 Hz and 5 KHz.

I have posted this video before, of my DAW playing back one of my recordings.

If you look a the meters on the lower right and the lower second from right in particular, You will see what I am talking about is correct.

That is why on a budget, a two way speakers is a much better bet. A truly powerful three way speaker is a formidable affair and most in the commercial market are just not up to the job.

May be we are missing each other's point. You are correct for what you play I suppose, but not when you play something else. I was only saying you were (or would be) wrong if you meant what you said as something that is always true, i.e. generalizing..

 

[Pogre]

Allow me to fix your calculations. The speaker system is rated at 90db. That means it will produce an SPL of 90db with 1 watt at a 1 meter listening distance. 9 db more SPL would require 17 watts at 1 meter and a bit more since you are listening at 1 1/2 meters. How much overhead do you think you need?

Looks like he's saying 105 dB nominal with room for more...

Calculations say I need a power amp with 250 watts for KEF R11 if I want to listen to music at 105db with some headroom.

Which is pretty unrealistic. However since it's an 8 Ohm speaker then the good ol' homestead spl calculator should work well enough to give us an idea...

Peak SPL Calculator

 

[ryanosaur]

However since it's an 8 Ohm speaker

with a 3.2 ohm minima.
Recommended Amplification is 15-300w.

Is it our concern if dude wants to take a pair of $3000 speakers and blow them and his hearing trying to relive his favorite rock concert?

 

[ryanosaur]

Allow me to fix your calculations. The speaker system is rated at 90db. That means it will produce an SPL of 90db with 1 watt at a 1 meter listening distance. 9 db more SPL would require 17 watts at 1 meter and a bit more since you are listening at 1 1/2 meters. How much overhead do you think you need?

Am I missing something? A doubling of power is required to gain 3dB SPL, right?
So 1w = 90
2w = 93
4w = 96
8w = 99
16w = 102
32w = 105
...all @ 1m distance

 

[Pogre]

with a 3.2 ohm minima.
Recommended Amplification is 15-300w.

Is it our concern if dude wants to take a pair of $3000 speakers and blow them and his hearing trying to relive his favorite rock concert?

Hey, I said several posts back that you don't even need justification for a beefy amp. I didn't for mine! Lol. I do think it's important people understand spl levels and their hearing tho. 105 dB is downright dangerous for any meaningful length of time.

 

[AcuDefTechGuy]

with a 3.2 ohm minima.
Recommended Amplification is 15-300w.

Is it our concern if dude wants to take a pair of $3000 speakers and blow them and his hearing trying to relive his favorite rock concert?

The KEF R11 are $6,000 per pair.

And I think we can conclude that it is OKAY to use a 200-300WPC amp with his $6,000/pair KEF R11, but he just needs to use sensible volume, not DEAF-volume that could permanently damage is hearing and his speakers.

 

[ryanosaur]

The KEF R11 are $6,000 per pair.

Indeed. $3000 Speakers... x2...

And I think we can conclude that it is OKAY to use a 200-300WPC amp with his $6,000/pair KEF R11, but he just needs to use sensible volume, not DEAF-volume that could permanently damage is hearing and his speakers.

Something in this makes me think of rainbows...

Ah, that's it... the "sensible" part.

 

[fmw]

Am I missing something? A doubling of power is required to gain 3dB SPL, right?
So 1w = 90
2w = 93
4w = 96
8w = 99
16w = 102
32w = 105
...all @ 1m distance

Correct. I stopped at 100 db which is as loud as it is standing next to a gas powered lawn mower. I wasn't trying to explain that he doesn't need 250 watts.

 

[john20182050]

Thanks a lot, everyone. I was stupid, there is a big misunderstanding on my side on what dB level I listen to and how the receiver volume controls work. Before I read all of your replies, the following was my understanding

1. THX recommendation of 105 dB (I knew it must be the peak dB)
2. But I thought when I properly configure my receiver with R11 and Monolith Sub 15 inch, I thought the receiver is sending enough/required power to speakers to produce 105 dB combined when I set volume control at 0dB (while using the decibel scale in volume control)

Now, I realize point 2 above is totally wrong. Most of the time I listen to music by setting -20db in the receiver volume control, but frequently I listen by setting volume control on the receiver at 0dB (but I don't do this continuously for more than 2 hours), and sometimes twice a week or so, I set the receivers volume control at +10db but with that I only listen to music for 30 minutes max.

So, originally when I said to listen at 105db with headroom with KEP R11, I need 250 watts, I was totally wrong and that was based on my wrong assumption of how the receiver volume controls work when I set volume control at 0dB.

I never measured sound pressure before. Today I measured with three different apps. Tried to measure with three volume levels in the receiver volume control (-20dB, 0dB, 10dB). The average dB differences measured on the phone app are not hugely different between those settings (about 5dB in two apps, and about 10dB in one app). I also measured using three different apps. One app always shows about 10dB more than the others, and I don't know why and which is correct. Please see the screenshot for the volume control set at 10dB on three different apps. One app shows the peak as 114. The other two app doesn't go above 90dB in max even if I set the max volume on the receiver.

Details for questions my below.

1. I always use monolith 15 subs with R11 for stereo music, AVR4400H gives a max of 125 watts per channel.
2. I sit about 12 feet from the front speakers.
3. Frequently I set 0dB in the receiver volume control (continously 2 hours max)
4. I sometime set 10dB in the receiver volume control (continouly 30 minutes max)
5. Currently I have 1 monolith 15 sub inch, I'm planning to get 1 more monolith 15 inch sub

Question:
With all of your replies and with my new understandings, looks like 125 may be enough to reach peaks of 105 dB even if I sit 12 feets away and set volume control 0dB to 10dB. Is that correct? or do you think I will still get benefit if I buy power amp since I sometime set 10dB in the receiver volume control? If yes, which one I should buy?

Also check my audyssey setting screenshot, I set to reference offset of 10dB for better music optimization. I don't really understand how that works and whether that also need to considered while deciding whether to buy power amp or not.

 

[3db]

Yeah, 105 dB peaks is one thing. Listening at 105 dB and expecting to need headroom on top of that is just... literally, dangerously a recipe for permanent hearing loss!

Sweet Baby Jesus!!!! My ears are ringing from just reading this.

 

[Pogre]

Some great replies, and thanks for doing a little bit of homework. I think we're all clear now on what you're wanting.

With all of your replies and with my new understandings, looks like 125 may be enough to reach peaks of 105 dB even if I sit 12 feets away and set volume control 0dB to 10dB. Is that correct? or do you think I will still get benefit if I buy power amp since I sometime set 10dB in the receiver volume control? If yes, which one I should buy?

I'm still digesting your whole post but wanted to address this right off. 125 probably is enough, but... if you regularly crank it to 0 and like it loud (me too sometimes) it wouldn't hurt for you to get a separate amp. If for any reason to take a little heat off your receiver. That's my justification and my receiver does indeed run much cooler now, especially with eco mode turned on. If you're using a separate amp eco mode won't choke back your power like it does when using the receiver's amps.

I think a 200-250 wpc amp is a fair number to shoot for in that it will give you at least a decent bump in power and should cover your peaks.

 

[ryanosaur]

Thanks a lot, everyone. I was stupid, there is a big misunderstanding on my side on what dB level I listen to and how the receiver volume controls work. Before I read all of your replies, the following was my understanding

1. THS recommendation of 105 dB (I knew it must be the peak dB)
2. But I thought when I properly configure my receiver with R11 and Monolith Sub 15 inch, I thought the receiver is sending enough/required power to speakers to produce 105 dB combined when I set volume control at 0dB (while using the decibel scale in volume control)

Now, I realize point 2 above is totally wrong. Most of the time I listen to music by setting -20db in the receiver volume control, but frequently I listen by setting volume control on the receiver at 0dB (but I don't do this continuously for more than 2 hours), and sometimes twice a week or so, I set the receivers volume control at +10db but with that I only listen to music for 30 minutes max.

So, originally when I said to listen at 105db with headroom with KEP R11, I need 250 watts, I was totally wrong and that was based on my wrong assumption of how the receiver volume controls work when I set volume control at 0dB.

I never measured sound pressure before. Today I measured with three different apps. Tried to measure with three volume levels in the receiver volume control (-20dB, 0dB, 10dB). The average dB differences measured on the phone app are not hugely different between those settings (about 5dB in two apps, and about 10dB in one app). I also measured using three different apps. One app always shows about 10dB more than the others, and I don't know why and which is correct. Please see the screenshot for the volume control set at 10dB on three different apps. One app shows the peak as 114. The other two app doesn't go above 90dB in max even if I set the max volume on the receiver.

Details for questions my below.

1. I always use monolith 15 subs with R11 for stereo music, AVR4400H gives a max of 125 watts per channel.
2. I sit about 12 feet from the front speakers.
3. Frequently I set 0dB in the receiver volume control (continously 2 hours max)
4. I sometime set 10dB in the receiver volume control (continouly 30 minutes max)
5. Currently I have 1 monolith 15 sub inch, I'm planning to get 1 more monolith 15 inch sub

Question:
With all of your replies and with my new understandings, looks like 125 may be enough to reach peaks of 105 dB even if I sit 12 feets away and set volume control 0dB to 10dB. Is that correct? or do you think I will still get benefit if I buy power amp since I sometime set 10dB in the receiver volume control? If yes, which one I should buy?

Also check my audyssey setting screenshot, I set to reference offset of 10dB for better music optimization. I don't really understand how that works and whether that also need to considered while deciding whether to buy power amp or not.

Not all music is recorded to THX References (0dB =85dB). 105dB is the +20dB Dynamic Peak that THX specs for Movie theaters to reproduce sound.

The impact of noise adds up over a lifetime. If you are exposed to loud sounds on a regular basis, your risk for permanent damage increases over time. Even a single but long-lasting loud event can cause damage. Sounds at or below 70 dBA are usually considered safe, even if they last a long time. Noises are more likely to damage your hearing if they are:

• 85 dBA and last a few hours.
• 100 dBA and last at least 14 minutes.
• 110 dBA and last at least 2 minutes.

It is worthwhile to buy a decent quality SPL meter and know what you are doing.
I use one of these:

Amazon.com: RISEPRO Decibel Meter, Digital Sound Level Meter 30 – 130 dB Audio Noise Measure Device Backlight MAX/MIN, Data Hold Auto Power Off Dual Ranges HT-80A: Garden & Outdoor

Buy RISEPRO Decibel Meter, Digital Sound Level Meter 30 – 130 dB Audio Noise Measure Device Backlight MAX/MIN, Data Hold Auto Power Off Dual Ranges HT-80A: Sound & Noise Meters - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

It's not the best, but affordable and will work better than a phone app.

 

[PENG]

I'm almost positive he means 105 dB continuous with headroom on top of it.

Impedance - 8 ohms
Sensitivity - 90 dB
10' seating distance
250 watts would be *over 113 dB at ten feet!

*2 speakers. Of course 110 dB with only one.

**Even 50 watts would be enough for 105 dB peaks at ten feet with 2 speakers, right? Am I wrong?

I hate to keep saying it depends, but it depends. If you consider THX standard, then with one speaker, no room he would actually need about 250 W for 105 dB peak.

More realistically, say assume 3 dB room gain and two speakers producing the same SPL, then he would need just 100 W, assuming the actual nominal impedance is closer to 6 ohm then the specified 8 ohms.

Again, we are all talking "peak". If he wants to listen to 105 dB average then to allow for 10 dB peak he would need 10X of the calculated 100 W, or if he allows for 20 dB peak then he would need 100X, or 10,000 W.

 

[Pogre]

I hate to keep saying it depends, but it depends. If you consider THX standard, then with one speaker, no room he would actually need about 250 W for 105 dB peak.

More realistically, say assume 3 dB room gain and two speakers producing the same SPL, then he would need just 100 W, assuming the actual nominal impedance is closer to 6 ohm then the specified 8 ohms.

Again, we are all taking "peak". If he wants to listen to 105 dB average then to allow for 10 dB peak he would need 10X of the calculated 100 W, or if he allows for 20 dB peak then he would need 100X, or 10,000 W.

Yeah, on top of that I bungled that post all up, lol.

 

[PENG]

Yeah, on top of that I bungled that post all up, lol.

I didn't notice that at all lol.., I thought you got it within the ball park.

 

[Pogre]

I didn't notice that at all lol.., I thought you got it within the ball park.

I accidentally clicked the "in a corner" button and it inflated everything by 6 dB! I was way off. More like 150-200 watts, but as you correctly point out, that depends. Ryan noted a 3.4 Ohm minima too. I'm actually on the side of him getting a 200-250 watt amp now. At least for the fronts. He likes it loud too.

 

[-Jim-]

Some great replies, and thanks for doing a little bit of homework. I think we're all clear now on what you're wanting.

I'm still digesting your whole post but wanted to address this right off. 125 probably is enough, but... if you regularly crank it to 0 and like it loud (me too sometimes) it wouldn't hurt for you to get a separate amp. If for any reason to take a little heat off your receiver. That's my justification and my receiver does indeed run much cooler now, especially with eco mode turned on. If you're using a separate amp eco mode won't choke back your power like it does when using the receiver's amps.

I think a 200-250 wpc amp is a fair number to shoot for in that it will give you at least a decent bump in power and should cover your peaks.

Gents,
Wouldn't it be worthwhile to get a couple 120mm USB fans on top of the receiver and keep it cool for the infrequent 2 hours that @john20182050 is driving it hard? If he's getting a second monolith 15 inch sub, I'd expect it to lighten the load on the AVR-X4400H a bit too. Just sayin...

 

[TLS Guy]

May be we are missing each other's point. You are correct for what you play I suppose, but not when you play something else. I was only saying you were (or would be) wrong if you meant what you said as something that is always true, i.e. generalizing..

I think you would have to play program with very little harmonic content for what I maintain not to be true. It would have to be a selection of all bass instruments, like double bass, bass brass instruments or bass guitars. That would be a limited repertory that I have not personally seen, even among the material others have brought here to master that are not my musical choice.