Power requirements - does more power matter that much?

Alrainbow

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Dec 12, 2013
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#21
I hear you , im only going by what other designers have said and what i have read it doesn't matter if the 3db + is 1K thats the standard for measuring sensitivity, what if the speakers are 5db plus at 100 , then all sensitivity means nothing if you can pick highest peak as your spec ...!


BTW are yours active or passive units
 

sbo6

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May 19, 2014
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#23
10w for 86db means the speaker has a sensitivity of about 77db... who uses anything like? And btw it'd be 640w to get to 103db.

A 20w for 89DB is the same as a 10w for 86db.
Please see above, the 10W to yields 86DB was at 4 meters distance to the sweet spot.
 

sbo6

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May 19, 2014
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#25
Passive woofers the whole system is passive .
Those designers are also right off course if the industrial sensitivity standard is measured at 1 K .
But much better is it imo to draw a median line through the average response and take that as sensitivity/efficiency number
Completely agree.
 

Robh3606

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Aug 25, 2010
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#26
1k is center frequency , you are +/- in relation to 1K. i dont think efficiency is measured there thou only Sensitivity , maybe Duke can chime in about efficiency ..
Hello Alrainbow

Efficiency is a fixed number. It's the conversion efficiency of a driver or a speaker system that is the percentage of electrical power that is converted into acoustic power. It's typically a very low number say 1-2%. The rest is heat in the voice coils or crossover components.

Sensitivity is a measurement that can be done at any power level and distance from the source. Our current standard is 1 watt 1 meter which has changed over the years. One manufacturer used to do 1 watt 15 feet as an example.

Not everyone use sensitivity @ 1K it depends on what is being measured an example would be bass drivers and wideband drivers. For example woofers measured from 100-500Hz and wide bands from 500-2.5K.

Even if it is measured at 1k as long as the speaker is reasonably flat through the bass and midband the power requirement will track with the 1K measurement.

Rob :)
 
Last edited:
Jan 23, 2011
4,794
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#27
My music power house Cat jl 2 sign .
I live in the past i know i never read reviews.

As taken from the Ml 3 review.

http://www.soundstagenetwork.com/revequip/lamm_ml3_signature.htm




The CAT JL2 Signature Mk 2 is in the middle in terms of power -- 100Wpc -- and it's a stereo amp, but that one chassis can pound out the music with greater authority than most amps I've heard -- and better than any tube amp.


Its says something its even mentioned with much higher priced amps.
To me its dead neutral , plus the start - stop speed of the amp " rivals " live sounds , unlike any solid state i ve heard , exception may be halcro .
Its not only about power , its how fast can it get delivered
 
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Audiophile Bill

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Mar 23, 2015
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#28
I spent a bit of time running the numbers to see about how much amplifier power matters as part of a FB post. I thought some folks might find it interesting and may be able to correct me if I'm incorrect in my quick assessment. I appreciate any feedback and comments.


Here are my thoughts on power and what I call speaker efficiency falsehood:

Speaker efficiency is commonly measured by applying 2.83V (assumes 1 W with an 8 ohm load) @ 1KHz @1 meter measured on axis. The current works out to be .35 Amps btw.
For a speaker with a nominal 8 ohm impedance and an efficiency rating of 88DB:
- +3DB requires 2x power, +10DB = 10x power. So let’s say we want to achieve an average (not peak) of 94DB (pretty loud). You would need 4x the power = 4 watts. For 104DB you’d need 10x = 40 watts. And for 107DB you’d need 2x = 80 watts.

- Now take into account the sweet spot distance to the speakers. Using the SPL to DB calculation and using our 88DB efficient speaker (measured @ 1 meter) let’s say our listening chair is 4 meters away = -12DB reduction. So now 80 watts yields 95DB (107DB – 12 DB for distance).

- There are other variables like efficiency gain via 2 speakers = +3DB depending on proximity, decrease in efficiency via room treatment (especially absorption) , speaker phase swings and voice coil impedance changes over high power / high temps, and other factors.

However here’s the biggest flaw I see in speaker efficiency and required power estimates: When is the last time you played a song that is a 1KHz tone? Music is incredibly complex spanning ~20 – ~20KHz simultaneously and often in bursts with dynamic swings. So all the calculations and resulting power estimates above are mostly meaningless because they are predicated on the signal equating to one frequency (and a fairly high frequency at that). Woofers are notorious for drawing significant current and are primarily excluded at 1KHz, so IMO you need much more than 80 watts to achieve 95DB @ 4 meters. Based on impedance and phase graphs for many speakers I’d take a swag and say you need 2x the average power to avoid compression, clipping, etc. For peaks I'm sure significantly more is required. And that, IMO is why power matters.
Interesting observations and a very relevant post imho.
Without wishing to bang the horn drum again, things do get much easier when you have super high sensitivity and speaker efficiency at least for the amplifiers I like to use (SET).
A friend texted me today about the recommendation to drive the cube audio speakers (93dB) with 3.5 watts 2a3 amplifier and I relayed the sums to him - one quickly realised that really low power amps do need very sensitive speakers IF you want to have big dynamic range and listen at live type spl.

Best.
 
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LL21

Well-Known Member
Dec 26, 2010
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#29
This was a post from Paul McGowan of PS Audio last week about power requirements for treble vs bass. I kept it in the file and thought it might be relevant here.

"Paul McGowan <paul@psaudio.com> Unsubscribe
10:01 AM (3 hours ago)​

One of the ever-interesting subjects a lot of us get confused with is tweeter power. If your amplifier outputs 1,000 watts and most tweeters can only handle maybe 50 watts max, how in the world is it more tweeters aren’t burned to a crisp?

The answer lies in the power distribution of music itself. Have a look at this analyzer’s output capturing some typical music.



Note how much power is needed for something like a kick drum at 50Hz (the bottom horizontal series of numbers denotes frequency) vs. even the 200 to 500Hz range where voices are. That’s a rather dramatic example of the uneven power distribution of music.

It takes a ton of energy to reproduce bass notes, but not a great deal as the scale goes upwards. Fact is, most tweeters never see more than a few watts.

It doesn’t matter how big your amplifier is when it comes to tweeters. A 1kHz capable amp still only outputs a few watts at tweeter frequencies when playing music."
PS Audio - Power Graph.jpg
 

Alrainbow

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Dec 12, 2013
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#30
Gee if I may ask one question
it’s a given any amp can clip ! so how is it almost always
mid to treble that we hear ? Has anyone posted any amps showing at the point it starts to clip. my point is in music there are very fast transients and most need far more power for it.
 

Alrainbow

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Dec 12, 2013
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#31
This was a post from Paul McGowan of PS Audio last week about power requirements for treble vs bass. I kept it in the file and thought it might be relevant here.

"Paul McGowan <paul@psaudio.com> Unsubscribe
10:01 AM (3 hours ago)​

One of the ever-interesting subjects a lot of us get confused with is tweeter power. If your amplifier outputs 1,000 watts and most tweeters can only handle maybe 50 watts max, how in the world is it more tweeters aren’t burned to a crisp?

The answer lies in the power distribution of music itself. Have a look at this analyzer’s output capturing some typical music.



Note how much power is needed for something like a kick drum at 50Hz (the bottom horizontal series of numbers denotes frequency) vs. even the 200 to 500Hz range where voices are. That’s a rather dramatic example of the uneven power distribution of music.

It takes a ton of energy to reproduce bass notes, but not a great deal as the scale goes upwards. Fact is, most tweeters never see more than a few watts.

It doesn’t matter how big your amplifier is when it comes to tweeters. A 1kHz capable amp still only outputs a few watts at tweeter frequencies when playing music."
View attachment 69045
Have Paulie post one up on a full scale opera with Orchestra .. :)


All that graph by Paulie shows is that specific recording requirements , a full Drum kit at full twack would have shown how much money is wasted buying single point source speakers for 100K plus ..


Whats next 50cents its my Birthday .. :)
 

DonH50

Member Sponsor & WBF Technical Expert
Jun 23, 2010
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#32
Gee if I may ask one question
it’s a given any amp can clip ! so how is it almost always
mid to treble that we hear ? Has anyone posted any amps showing at the point it starts to clip. my point is in music there are very fast transients and most need far more power for it.
It's easier to hear frequencies in the midrange, and clipping in the bass generates higher-frequencies easier to hear.

Clipping overview: https://www.whatsbestforum.com/threads/clipping-101.8484/#post-147098
 

sbo6

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May 19, 2014
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#33
Hello sbo6

I think are looking at this from the wrong direction and making it much harder than it needs to be. First of all your statement saying all speaker sensitivity is based on a 1 K tone is simply incorrect. Even if a 1K tone was used if the system was full range and +/_ 3db 20-20K of your tone the calculations would essentially be correct.

The easiest way to determine amp power needed is to know what your max SPL requirement is at your listening position and go from there. If you have enough power to meet your Max target SPL you will be fine. All passive speakers are set up typically using the woofer sensitivity as the reference level for sensitivity. You are not likely going to need much more power at 100Hz vs 1K to reach the same SPL.

As far as speakers as loads considering impedance and phase angles again you just pick an amp that can safely drive them.

I do not think running calculations or using available on line calculators is a meaningless exercise. They are actually a handy tool to do a quick snapshot and let you know how much power you need.

Here play with this:

http://myhometheater.homestead.com/splcalculator.html#anchor_13193

Rob :)
Thanks Rob. Firstly, I don't think my statement that all speaker sensitivity is based on a 1KHz tone is incorrect, it's a fact if it adheres to the conventional 1KHz tone at 1 meter at 2.83V. Now, you make a good point in that if that speaker's frequency response is close to flat or as you say +/- a few DB that irrespective of the test tone the sensitivity would be the same. However one piece is missing - the speaker's frequency response assumes that the amplifier can handle the speaker load irrespective of impedance dips or challenging phase shifts. Similarly, your comment that, "All passive speakers are set up typically using the woofer sensitivity as the reference level for sensitivity. You are not likely going to need much more power at 100Hz vs 1K to reach the same SPL". We'll have to agree to disagree. For example my own Vivid Audio Giya G2s dip to around 4 ohms from 50 - 100Hz which is a somewhat hefty current load while the front firing drivers span >=220Hz are >=10 ohms, a very easy load. So while the speaker may be primarily flat 30 - 20Khz the current required to achieve this across the drivers is not linear.
 
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Alrainbow

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Dec 12, 2013
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#34
 

Alrainbow

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Dec 12, 2013
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#35
A one pulse or freq does not show all we need. most amps clip for psu design while some can at over load input. Oddly as paulie has my speakers and I’m willing to bet his own amps clip plenty on his setup at a given volume and songs. but this is why power is needed. it’s been a long time since I woke up long gone memories on this topic. why tweeters get fried is due to harmonic distortion high above our hearing range. Lower freq if I recall correctly are closer to rms values and allow an amp to cope better in some cases. but it’s a combination of real world music playing that causes clipping. Clipping can be amd mostly is a simple phrase or syllable while being sung. it’s very predictable once you hear it. Lowering the volume 3 dB then 6 hells diagnose it. it’s a shout now why my guess is the fast rise and large power needed at this point. most times a symbol crash is less then what a piano strike and female vocal needs.
Dianne krall is a good example as she varies her tone on singing.
the above attachment is nice but like Paulies graph not real world facts. I tried a few amps to stop it at my place. while my amps are nearly 800 pounds and perhaps over kill they do whatever the speakers need at precision levels
even playing low amps can clip if the need that is many times typical level arises. Gloria E Mia tiara made this happen at less then listening levels.
 

sbo6

Well-Known Member
May 19, 2014
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Round Rock, TX
#36
This was a post from Paul McGowan of PS Audio last week about power requirements for treble vs bass. I kept it in the file and thought it might be relevant here.

"Paul McGowan <paul@psaudio.com> Unsubscribe
10:01 AM (3 hours ago)​

One of the ever-interesting subjects a lot of us get confused with is tweeter power. If your amplifier outputs 1,000 watts and most tweeters can only handle maybe 50 watts max, how in the world is it more tweeters aren’t burned to a crisp?

The answer lies in the power distribution of music itself. Have a look at this analyzer’s output capturing some typical music.



Note how much power is needed for something like a kick drum at 50Hz (the bottom horizontal series of numbers denotes frequency) vs. even the 200 to 500Hz range where voices are. That’s a rather dramatic example of the uneven power distribution of music.

It takes a ton of energy to reproduce bass notes, but not a great deal as the scale goes upwards. Fact is, most tweeters never see more than a few watts.

It doesn’t matter how big your amplifier is when it comes to tweeters. A 1kHz capable amp still only outputs a few watts at tweeter frequencies when playing music."
View attachment 69045
This is one of several reasons why I cross over my mains at ~80Hz to 4 JLA Fathom subs. My amp for the woofers only has to handle 220Hz - 80Hz. Subs do below and combined have thousands of watts.
 

LL21

Well-Known Member
Dec 26, 2010
11,686
570
658
#37
This is one of several reasons why I cross over my mains at ~80Hz to 4 JLA Fathom subs. My amp for the woofers only has to handle 220Hz - 80Hz. Subs do below and combined have thousands of watts.
I can appreciate that! Even our 1 x Velodyne DD18+ sub has a Class D 1250 watt amp. If we went 2 x dual 18s with someone like Funk, it would be more like 8,800 watts A/B between the 2 subs.
 
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