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Discussion Starter · #1 ·
I seem to recall there was an old rule of thumb that stated the following. Don't buy a pair of speakers unless they are rated at twice the power of the amp feeding them. A 50 watt amp would need a speaker that is rated at 100 watts or higher for example.


Does this still hold true today? Since technology has changed a bit over the years, I was wondering if I still need to buy speakers that have a higher power handling capacity than the amp I use to drive them.
 

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Nope, I'm using a 180W (into 8 ohm, 270W into 4 ohm)) amp into 200W 4ohm speaker, 125 6ohm, 200W 8ohm, 200W 4ohm. No problems.
 

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Quote:
Originally Posted by WILWRadio  /t/1524217/amp-power-to-speaker-wattage-rating#post_24526623


I seem to recall there was an old rule of thumb that stated the following. Don't buy a pair of speakers unless they are rated at twice the power of the amp feeding them. A 50 watt amp would need a speaker that is rated at 100 watts or higher for example.


Does this still hold true today? Since technology has changed a bit over the years, I was wondering if I still need to buy speakers that have a higher power handling capacity than the amp I use to drive them.

Speaker power ratings are not as well-defined as amplifier power ratings, so there is quite a bit of latitude in matching the power ratings of amps and speakers.


The power rating of the amplifer needs to be matched to the following in concert:


(1) Speaker efficiency

(2) Listening distance

(3) Listener preference for loudness or not so much loudness.


The general rule of thumb is that if you overpower a speaker it will start sounding bad before it gets really hurt. When amps are overdriven and start to clip and they can surprise people by delivering far more power than people expect. In the end it is excess power that destroys speakers.
 

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Quote:
In the end it is excess power that destroys speakers.

I'd say the opposite, distortion destroys speakers. A amp that is say 3W output would probably cause distortion, and therefore damage your speakers. You'll never drive a 200W amp into distortion, your speakers would blow up from very high SPL way before then, and if you listen to music at 110dB....that's your fault
 

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Too little power can lead to clipping which can damage your speakers. Generally too much power is not an issue because for most people their ears will give up before the speakers do.
 

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Yup in both cases frying a blown treble driver was due to lack of power. Yamaha AV amplifier, and 60W Hi-Fi amplifier. I used a NAD 30W amplifier and it just sounded bloaty, I think that's early sign when bass comes bloaty like that.
 

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Old myth. You don't blow speakers because of distortion. Speakers don't care how nice the music is or what the sound is that they are reproducing. You blow them because too much current passes through the voice coil and it overheats.
 

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Funny then how the treble driver died on me after playing music loud on a Yamaha AV amplifier. Replaced with a dedicated stereo integrated amp with real rated power and no problems since.
 

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Quote:
Originally Posted by fatbottom  /t/1524217/amp-power-to-speaker-wattage-rating#post_24526665


I'd say the opposite, distortion destroys speakers.
Distortion/clipping never destroys speakers, only over-powering does. In the case of tweeters it's the increased harmonic content of a clipped signal that overpowers them and burns them out. That's because a tweeter typically only receives 5% of the total system power. With a 100 watt speaker the tweeter normally will receive no more than 5 watts. But if you use a 40 watt amp driven to 50% THD the tweeter will receive 10 watts, over-powering it and burning it out.
Quote:
Funny then how the treble driver died on me after playing music loud on a Yamaha AV amplifier. Replaced with a dedicated stereo integrated amp with real rated power and no problems since.
That's called anecdotal evidence. You correctly identified the result, but not the cause. To understand the cause on must know all of the facts, in this case specifically the effect on the high frequency power density of a clipped versus clean signal, and the normal power distribution with respect to frequency of an audio signal. An in-depth explanation can be found here:
http://forum.qscaudio.com/forum/viewtopic.php?f=29&t=2736
http://www.jblpro.com/pub/technote/lowpower.pdf
 

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Quote:
Originally Posted by fatbottom  /t/1524217/amp-power-to-speaker-wattage-rating#post_24526743


Funny then how the treble driver died on me after playing music loud on a Yamaha AV amplifier. Replaced with a dedicated stereo integrated amp with real rated power and no problems since.

Stories like that fill the web. In the end the circumstances were 100% under the control of the advocate of big expensive power amps, so we are not exactly talking an unbiased scientific test.


Maybe you've never worked with really powerful amps, as one has to step outside of the sacred halls of consumer audio to find them. Trust me, if you ever have worked with really big amps a lot you would likely know that ultimately it is excess power that destroys speakers. All the shouting nets out to be a discussion of how that power comes into lives of the speaker drvers. With big amps, toasted drivers with the magic smoke gone are just a flick of the wrist or any number of innocent accidents away. Fuses can be your friend!
 

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Watt would go first? Throwing 400 watts RMS at my 1000 watt RMS speakers OR my ears?
 

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Quote:
Originally Posted by fatbottom  /t/1524217/amp-power-to-speaker-wattage-rating#post_24526743


Funny then how the treble driver died on me after playing music loud on a Yamaha AV amplifier. Replaced with a dedicated stereo integrated amp with real rated power and no problems since.

Less current has passed through the voice coil.
 

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That's why I use a 20 WPC tube amp on 105db efficient speakers. It gets too loud before the amp clips, at least to my ears. Years ago, I used a Phase Linear 400 on some AR-2ax. They needed power to get louder sounds out of these hogs, but too much current blew the tweet and the mid. Remember, it is a magnet moving a wire, I.e. coil.
 

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Quote:
Originally Posted by WILWRadio  /t/1524217/amp-power-to-speaker-wattage-rating#post_24526623


I seem to recall there was an old rule of thumb that stated the following. Don't buy a pair of speakers unless they are rated at twice the power of the amp feeding them. A 50 watt amp would need a speaker that is rated at 100 watts or higher for example.


Does this still hold true today? Since technology has changed a bit over the years, I was wondering if I still need to buy speakers that have a higher power handling capacity than the amp I use to drive them.

Much good and correct advise given already regarding the ultimate cause of the magic smoke - too much power. But my rule of thumb is to size the amp for the program power of the speaker, not the continuous or RMS wattage rating. This way I am comfortable that peaks are delivered cleanly and with the lowest possible distortion. Unfortunately, in the consumer space the distinction is often not made or specified and you're shooting in the dark. But that's why I stay away from the consumer stuff...
 

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Discussion Starter · #15 ·

Quote:
Originally Posted by Gooddoc  /t/1524217/amp-power-to-speaker-wattage-rating#post_24527273


Much good and correct advise given already regarding the ultimate cause of the magic smoke - too much power. But my rule of thumb is to size the amp for the program power of the speaker, not the continuous or RMS wattage rating. This way I am comfortable that peaks are delivered cleanly and with the lowest possible distortion. Unfortunately, in the consumer space the distinction is often not made or specified and you're shooting in the dark. But that's why I stay away from the consumer stuff...

I've never heard the term "program power used in the context of describing a loudspeaker". Can you elaborate?
 

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Discussion Starter · #16 ·
The amp I am planning to purchase is the following.

http://www.parts-express.com/topping-tp60-tripath-ta2022-50wpc-(80wpc-4-ohm)-mini-amplifier--310-326


Since this is a Class T amp, I am pretty unsure of how to proceed with a speaker purchase. Right now I also have a Topping T21 that could not drive 8 ohm Castle Conway 3 speakers very well at all. Currently using it with Jamo C601's and those being 6 ohm seem to match up better. Can't really crank it up without distortion but at least low to moderate audio levels sound fine.


It is likely my next pair of speakers will either have to be front ported or not ported at all thanks to the odd shape of my back wall in the living room. Budget is around $400 or less. Was looking at the Polk RTI A3 which Stereophile gives a thumbs up to but it seems to be a little bass heavy which is something I want to avoid. I like the sound of the Jamo's a lot but they are rear ported. Need to find a pair of speakers that are either very neutral or a bit warm like the Jamo's that also have plenty of detail, a clear high end (not bright like Klipsch) and balanced midrange that is not going to be over powered by the bass.


Was thinking of buying the following but it is rated at only 65 watts per channel and apparently at 8 ohms.

http://www.parts-express.com/dayton-audio-rs621cck-speaker-kit-pair-curved-cherry--302-963


I am thinking that I will need at least 100 watts per channel at 8 ohms if I am going to safely drive the T60 Topping amp.


Any additional suggestions will be welcome.
 

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You are going about this backwards. Find the speakers you want, and then get an amplifier to power them. It doesn't matter what the speaker's power ratings are, the sensitivity is what is important. A speaker that has a sensitivity of 90dB, only needs 1 watt to play that loud at 3 feet away. As you move away, the SPL decreases. To increase your SPL by 3dB, it takes twice as much power. So at 3 feet away, you need 2 watts of power to hit 93dB, and 4 watts to hit 96dB. Anything over 95dB is starting to get uncomfortably loud. Now as you move away, the SPL decreases, I think some studies say around -10dB at 3 meters, but this isn't a linear relationship, nor an exact number; just an approximation. So at 10 feet from your speakers, that 4 watts now produces ~86dB, and 8 watts produces ~89dB. generally this is where those little t-amps start to hit their max before distortion increases, so yes cranking up speakers with a t-amp is not going to work well in most cases.


If you want a powerful compact amp, that will drive anything louder than you care to listen, go with an Emotiva mini-x a-100 . For a speaker in the $400 range, I would take a look at the NHT Absolute Zero, it is incredibly accurate, and also sealed so you won't have port issues or boomy sound you want to avoid.
 

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Quote:
Originally Posted by WILWRadio  /t/1524217/amp-power-to-speaker-wattage-rating#post_24529976


I am thinking that I will need at least 100 watts per channel at 8 ohms if I am going to safely drive the T60 Topping amp.

Any additional suggestions will be welcome.
Don't over-think this. Most speakers can't use more than half their rated input power before the drivers reach their excursion limits. If you have more power available that's fine, that's why amps have volume controls, but chances are you won't actually use it. By and large if you have speakers rated at, say, 100w, then anything between 50w and 200w amplifier power is appropriate.
 

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Quote:
Originally Posted by fatbottom  /t/1524217/amp-power-to-speaker-wattage-rating#post_24526665


I'd say the opposite, distortion destroys speakers. A amp that is say 3W output would probably cause distortion, and therefore damage your speakers. You'll never drive a 200W amp into distortion, your speakers would blow up from very high SPL way before then, and if you listen to music at 110dB....that's your fault

So... excess power doesn't kill speakers, but speakers blow up from very high SPL. See a contradiction?
 
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Quote:
Originally Posted by WILWRadio  /t/1524217/amp-power-to-speaker-wattage-rating#post_24529949


I've never heard the term "program power used in the context of describing a loudspeaker". Can you elaborate?

It is essentially a number used to guide amplifier selection. It's used to indicate the maximum recommended amplifier power to account for crest factor, or brief power handling capability. It's often a simple product of average power × 2, but when manufacturers specify only program power, they usually don't specify how they derived the number.
 
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