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

[PENG]

No, you underestimate the power required above 400 Hz. That IS the lions share of the spectrum of most instruments. Insufficient power and resources in the region is a major failing of most speakers. Dynamic compression is a huge problem of three way designs. 400 Hz to 4 KHz is a major power band. For most midrange drivers, two are required and not one!

You are totally wrong on this because you typically started with a general statement. If you were to qualify your statement then we can debate. I have done both calculations and measurements for different scenarios, I suggest you do the same, and you will then realize as I said before, it always depend. To make generalize statement may mislead others.

 

[AcuDefTechGuy]

I will say, if op wants a powerful amp then I say just get one. It's certainly not necessary, but that hasn't stopped most of us from getting one. There's no need to justify it by claiming ridiculous listening levels tho.

Yeah, I started out in this hobby with a 200WPC amp. Got it out of my system. Right into the deep end. No baby steps.

 

[PENG]

I will say, if op wants a powerful amp then I say just get one. It's certainly not necessary, but that hasn't stopped most of us from getting one. There's no need to justify it by claiming ridiculous listening levels tho.

Right, I listen to less than 90 dB peaks 99% of the time, and I pair my 350 W/500W 8/4 ohm amp now for my R900, the predecessor of the R11. My R900 is rated 115 dB maximum, the R11 is rated 111 dB maximum.

Most speaker that has the "recommended power requirement" of 15 - 300 W such as the R900, should be able to cope with much more than 300 W on "peak" basis.

 

[Pogre]

Most speaker that has the "recommended power requirement" of 15 - 300 W such as the R900, should be able to cope with much more than 300 W on "peak" basis.

Conversely, they can perform just as well at lower levels with far less than 300 w and still get plenty loud. I'd argue 100 w is plenty for most situations. I totally get wanting a big amp tho.

Sometimes you just need a big amp...

 

[ryanosaur]

This is what can happen overdiving KEFs:

 

[Pogre]

This is what can happen overdiving KEFs:
View attachment 55250

View attachment 55251

View attachment 55252

EEK!

 

[ryanosaur]

EEK!

To be fair, I think those were smaller speakers trying to pound out some bass. Still. Not a good look.

 

[-Jim-]

@john20182050 - I just responded to your most recent question at your old thread Is AVR-4400H good enough KEF R11?

Having read this one as well, I suggest you protect your hearing at all times. Once it's damaged, there is a strong possibility it will never recover. Nothing wrong with having more power, just use it wisely.

 

[PENG]

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

 

[Pogre]

I think I have measured my ENTIRE system to be 105dB with all the subs firing away for a relatively short period of time.

The loudest I've measured in my room was with mains and subs only and juussst shy of 100 dB from 14.5 feet and it was deafening. Almost uncomfortable. Well, sober it was almost uncomfortable. For some reason a few drinks makes it more tolerable.

 

[PENG]

@john20182050 - I just responded to your most recent question at your old thread Is AVR-4400H good enough KEF R11?

Having read this one as well, I suggest you protect your hearing at all times. Once it's damaged, there is a strong possibility it will never recover. Nothing wrong with having more power, just use it wisely.

One can indeed never recover from hearing damage. I don't think anyone is suggesting the OP listens to 105 dB peak though, occasionally and for very short burst may be okay. The discussion, I believe is mainly on whether the 250 W amp he is considering would damage his speakers. So technically I have to say yes it can, but then so can a 100 W amp, because it depend!!

 

[Pogre]

One can indeed never recover from hearing damage. I don't think anyone is suggesting the OP listens to 105 dB peak though, occasionally and for very short burst may be okay. The discussion, I believe is mainly on whether the 250 W amp he is considering would damage his speakers. So technically I have to say yes it can, but then so can a 100 W amp, because it depend!!

If I'm understanding correctly he mentions the necessity for 105 dB in his op "with some headroom".

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.

Unless he means to say that the 105 dB IS the headroom he's wanting to have...

 

[Pogre]

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

And just to really drill it home, 105 dB is, truly, unrealistic unless you mean peaks. Even at that it's not recommended anyone listen at those levels for any meaningful length of time.

It's nice to have the power, sure. You might even dip into it for occasional peaks, but that kind of volume continuously is bad. Just bad. It will permanently damage your hearing, and it will only get worse with more exposure over time.

 

[PENG]

If I'm understanding correctly he mentions the necessity for 105 dB in his op "with some headroom".

Unless he means to say that the 105 dB IS the headroom he's wanting to have...

Thank you for emphasizing this point. Once again I got right into the technical and neglected the hearing loss concerns for the OP. Hopefully he does mean peak, and any headroom is just to stay clear from clipping, not that he would actually get close to using it.

 

[Pogre]

Thank you for emphasizing this point. Once again I got right into the technical and neglected the hearing loss concerns for the OP. Hopefully he does mean peak, and any headroom is just to stay clear from clipping, not that he would actually get close to using it.

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?

 

[Pogre]

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 messed that all up. I clicked "in a corner" by accident. Still tho, 150 watts per channel with 2 speakers is sufficient for 105 dB peaks

 

[AcuDefTechGuy]

The loudest I've measured in my room was with mains and subs only and juussst shy of 100 dB from 14.5 feet and it was deafening. Almost uncomfortable. Well, sober it was almost uncomfortable. For some reason a few drinks makes it more tolerable.

This was dB-C, not dB-A?

Because I think I got it to 105dBC or close to it. It was mainly BASS-HEAVY music. I didn't keep it that loud, of course. I was just TESTING.

 

[Pogre]

This was dB-C, not dB-A?

Because I think I got it to 105dBC or close to it. It was mainly BASS-HEAVY music. I didn't keep it that loud, of course. I was just TESTING.

C weighted I believe it was... lemme see if I can find it...

Ha. C and Z weighted.

 

[-Jim-]

Gents,

With the assumption his system is all dialed in, and before @john20182050 goes shopping for more power, I'd suggest he get a free sound pressure App for his cell phone (if he doesn't already have a device to measure the Sound Pressure Levels); put on his favorite music he likes to listen to loud with his existing receiver setup; and measure how loud it is for a short time. (I'd turn off the Eco Mode, or at least have it on Auto with his Denon AVR-X4400H.)

These Apps (at least on my iPhone) are reasonably close to what my SPL Meter, and Calibrated Mic with REW, indicate. Certainly close enough for this exercise. That way he'll get a feel for what his real loudness needs are, without relying totally on calculated values. Then he'll know if 105 dB (C-weighted) plus "headroom" is really where he wants to go.

Just my 2 bits...

 

[Pogre]

Gents,

With the assumption his system is all dialed in, and before @john20182050 goes shopping for more power, I'd suggest he get a free sound pressure App for his cell phone (if he doesn't already have a device to measure the Sound Pressure Levels); put on his favorite music he likes to listen to loud with his existing receiver setup; and measure how loud it is for a short time. (I'd turn off the Eco Mode, or at least have it on Auto with his Denon AVR-X4400H.)

These Apps (at least on my iPhone) are reasonably close to what my SPL Meter, and Calibrated Mic with REW, indicate. Certainly close enough for this exercise. That way he'll get a feel for what his real loudness needs are, without relying totally on calculated values. Then he'll know if 105 dB (C-weighted) plus "headroom" is really where he wants to go.

Just my 2 bits...

I have found the phone apps to be accurate enough to ballpark it for sure.