Matching speakers to reciever wattage

[mrboomble]

I have a Denon 2805. (100 watts per channel), is it safe to attach Klipsch RB-25 rated at 75 watts to the system? Can I easily "blow" these speakers with a higher wattage amp?

I would appreciate any info.Thanks.

If anyone knows a detailed article on the subject, I would appreciate it.

 

[MDS]

The power ratings of speakers are very conservative and most speakers can take far more power than their rating for a short period of time.
You should not have any problems with the Denon and Klipsch combination.

It is far easier to blow speakers (usually the tweeters) by using an underpowered amp and pushing it real hard; ie turning it up near its limits. This is because as power output increases, distortion increases as well. Driving an underpowered amp past its limits causes the waveform to clip (begins to look like a square wave) and that is what damages tweeters.

You can of course just as easily blow speakers by using a high powered amp; that is if the amp can put out CLEAN power without clipping that is far in excess of your speakers rating.

Remember too that a large majority of the time your amp won't be putting out anywhere near 100 watts. Don't sweat it.

 

[MacManNM]

Its always better to have more power than your speakers can handle. Pure power rarely blows speakers, clipping kills them.

 

[Nick250]

I have a Denon 2805. (100 watts per channel), is it safe to attach Klipsch RB-25 rated at 75 watts to the system? Can I easily "blow" these speakers with a higher wattage amp?

I would appreciate any info.Thanks.

If anyone knows a detailed article on the subject, I would appreciate it.

I suspect you would experience hearing damage way before damage to the Klipschs since the Klipschs are pretty darn efficent.

 

[annunaki]

Its always better to have more power than your speakers can handle. Pure power rarely blows speakers, clipping kills them.

Please explain how that happens. When an amplifier fully clips it doubles it's output. I would say this additional power, combined with a speaker going into power compression, is what actually blows speakers. That and someone who cannot hear distortion.

For those that do not know what power compression is:

Power compression is when additional power is applied to a speaker beyond it's rms rating with no additional gain in output. All additional power becomes wasted in additional heat, as the speaker can no longer cool the voice coil effectively. The more time spent in power compression, the closer the speaker comes to voice coil failure.

 

[MacManNM]

Please explain how that happens. When an amplifier fully clips it doubles it's output. I would say this additional power, combined with a speaker going into power compression, is what actually blows speakers. That and someone who cannot hear distortion.

For those that do not know what power compression is:

Power compression is when additional power is applied to a speaker beyond it's rms rating with no additional gain in output. All additional power becomes wasted in additional heat, as the speaker can no longer cool the voice coil effectively. The more time spent in power compression, the closer the speaker comes to voice coil failure.

The DC component of clipping creates the compression because the fields of the VC are saturated. So clipping kills speakers.

 

[MacManNM]

Please explain how that happens. When an amplifier fully clips it doubles it's output. I would say this additional power, combined with a speaker going into power compression, is what actually blows speakers. That and someone who cannot hear distortion.

Plus power compression usually doesn't happen until a power level of 10-20% above the speakers wattage rating. Depending on the MFGR, I have measured as high as 60% on some brands.

 

[annunaki]

Rather than explain (which I can be clumsy at once in awhile), I will use a post from another forum. The post sums up what I would have said but in probably fewer words: (the second paragraph is what I am refering to)

Rob M
CS&P ULTRA Member
Member # 4612

posted October 22, 2004 05:01 PM
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quote:
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Originally posted by Inno:
Ok, first post here so I better make it count!

Lets start with the basics. Every amplifier uses a positive and a negative (DC) voltage to reproduce the audio signal (theres much more to it but this will do for now). It is a set voltage but will vary depending on the amp. Now, when the audio is being played the speakers are moving back and forth with the fluctuating voltage, if the input signal drives the outputs to their maximum voltage, that's the most they can put out. Driving the signal any harder will only cause the voltage to stay at it's highest limit for a longer period of time, thus causing a straight DC signal to be sent to the speakers at the peaks of the waveform.........this, when viewed as a waveform with an oscilloscope looks like a regular audio signal with the tops cut off, or "clipped". So not only are you missing the dynamics of the music, you're damaging the speakers and over-taxing the amp.
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You're right until the "straight DC signal" part; wrong thereafter. When an amp is driven hard into clipping the output stage dissipates LESS energy because the transistors are either off (high voltage across the transistor, no current through it = no power dissipation) or on (low voltage across the transistor, high current through it = low power dissipation). The power supply might not be able to handle the increased demand, but that usually only results in the internal +/- rails in the amp dropping.

As far as damaging speakers, it's just the extra power with the amp putting out more voltage longer when clipping rather than "DC." A speaker doesn't care about clipping; it's still moving and getting cooled with even a clipped wave. And since the speaker is a low-pass filter, it can't respond immediately to the sharp corner in the clipped output of the amplifier so it just keeps moving and doesn't "hang up."

 

[MacManNM]

Rather than explain (which I can be clumsy at once in awhile), I will use a post from another forum. The post sums up what I would have said but in probably fewer words:

Rob M
CS&P ULTRA Member
Member # 4612

posted October 22, 2004 05:01 PM
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quote:
--------------------------------------------------------------------------------
Originally posted by Inno:
Ok, first post here so I better make it count!

Lets start with the basics. Every amplifier uses a positive and a negative (DC) voltage to reproduce the audio signal (theres much more to it but this will do for now). It is a set voltage but will vary depending on the amp. Now, when the audio is being played the speakers are moving back and forth with the fluctuating voltage, if the input signal drives the outputs to their maximum voltage, that's the most they can put out. Driving the signal any harder will only cause the voltage to stay at it's highest limit for a longer period of time, thus causing a straight DC signal to be sent to the speakers at the peaks of the waveform.........this, when viewed as a waveform with an oscilloscope looks like a regular audio signal with the tops cut off, or "clipped". So not only are you missing the dynamics of the music, you're damaging the speakers and over-taxing the amp.
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You're right until the "straight DC signal" part; wrong thereafter. When an amp is driven hard into clipping the output stage dissipates LESS energy because the transistors are either off (high voltage across the transistor, no current through it = no power dissipation) or on (low voltage across the transistor, high current through it = low power dissipation). The power supply might not be able to handle the increased demand, but that usually only results in the internal +/- rails in the amp dropping.

As far as damaging speakers, it's just the extra power with the amp putting out more voltage longer when clipping rather than "DC." A speaker doesn't care about clipping; it's still moving and getting cooled with even a clipped wave. And since the speaker is a low-pass filter, it can't respond immediately to the sharp corner in the clipped output of the amplifier so it just keeps moving and doesn't "hang up."

Clipping turns the output into essentially a square wave. At the top and bottom of the square wave there is a DC level, usually near the rail voltage. The speaker sees this as DC. The fields in the speaker saturate, causing it to go into compression, heating the VC and smoking it. So I guess I should have said pulsed DC. I believe we are saying the same thing. I work in a world where I measure 100 fs pulses, so to me a 10 KHz square wave, has an eternity of DC content. Either way, this clipping, is what causes speakers to blow more often than not.

 

[annunaki]

What I am trying to get across, is that "clipping" itself is not doing the damage. It is the excess power generated when the clipping occurs. The dynamic range compression developed by the waves being clipped raises the average power over time. The higher average power (i.e. excess heat) causes a voice coil to fail.

I have run a 100 watt amplifier fully clipped for more than 20 minutes into a speaker before to prove this point. The speaker's power handling was well above 200 watts (500 watts rms). It had absolutely no issues with the clipped power. No smoke no failures. The magnet assembly was not even warm. The speaker's power handling limits were not exceeded thus no failure. granted, it sounds horrible, but there was no failure mechanical or thermal.

 

[MacManNM]

What I am trying to get across, is that "clipping" itself is not doing the damage. It is the excess power generated when the clipping occurs. The dynamic range compression developed by the waves being clipped raises the average power over time. The higher average power (i.e. excess heat) causes a voice coil to fail.

I have run a 100 watt amplifier fully clipped for more than 20 minutes into a speaker before to prove this point. The speaker's power handling was well above 200 watts (500 watts rms). It had absolutely no issues with the clipped power. No smoke no failures. The magnet assembly was not even warm. The speaker's power handling limits were not exceeded thus no failure. granted, it sounds horrible, but there was no failure mechanical or thermal.

Thats because the output of a 100 watt amp fully clipped really can't exceed 200 watts. A clipped output has more RMS power than a clean sine wave.

If that was a 150 watt speaker, it would have been fried.

 

[annunaki]

I understand that. That is what I have been trying to explain to you. Clipping in and of itself does not kill the speaker's coil. It is the extra power generated when it happens. Saying "clipping fries voice coils" as a blanket statement, is completely incorrect. Too much average power over time (exceeding a speaker's power handling), induced by clipping is what fries voice coils.

 

[MacManNM]

I understand that. That is what I have been trying to explain to you. Clipping in and of itself does not kill the speaker's coil. It is the extra power generated when it happens. Saying "clipping fries voice coils" as a blanket statement, is completely incorrect. Too much average power over time (exceeding a speaker's power handling), induced by clipping is what fries voice coils.

So clipping is the prelude to blowing speakers, I stand corrected.

Most people dont understand the physics behind what happens. It's much easier to tell someone in terms they understand. A lot of people don't know what clipping is, but they know its bad. 90% of speakers that burn out voice coils happen in the real world because someone is overdriving thier amp, causing tons of IMD, THD, and clipping. It's not what you say, it's how people interpret what you say. Buy getting an amp that has slightly more power, a person is less likely to gernade their system.

In the end, a person that fries his speakers ,with a 110 w/ch receiver, and a pair of 175-watt speakers, it was because he ran the amp into clipping. Probably because he was already deaf, or listened to distorted metal all the time and couldn't tell the difference between loud and crap.

By the way, did you do that clipping test with a woofer or a tweeter? I guess it doesn't make a difference. Or does it?

 

[Buckeyefan 1]

What I am trying to get across, is that "clipping" itself is not doing the damage. It is the excess power generated when the clipping occurs. The dynamic range compression developed by the waves being clipped raises the average power over time. The higher average power (i.e. excess heat) causes a voice coil to fail.

I have run a 100 watt amplifier fully clipped for more than 20 minutes into a speaker before to prove this point. The speaker's power handling was well above 200 watts (500 watts rms). It had absolutely no issues with the clipped power. No smoke no failures. The magnet assembly was not even warm. The speaker's power handling limits were not exceeded thus no failure. granted, it sounds horrible, but there was no failure mechanical or thermal.

Did you run that test with a flat eq setting? Boost the parametric eq settings of 8 and 16 kHz to "max" and rerun that test. Or use an old school 10 band BSR eq and boost the last three bands. I bet the tweeters don't last 15 minutes unless you are running horns.

 

[annunaki]

I ran the test with a woofer. Tweeters do succomb to clipping induced power compression much faster than a woofer, as the cannot move enough air to cool their coils. That is why tweeter protection circuits are used to scale back wattage. that is also why tweeters without protection tend blow fairly easily with highly distored/clipped signals.

 

[Buckeyefan 1]

I ran the test with a woofer. Tweeters do succomb to clipping induced power compression much faster than a woofer, as the cannot move enough air to coil their coils. That is why tweeter protection circuits are used to scale back wattage. that is also why tweeters without protection tend blow fairly easily with highly distored/clipped signals.

I hate when I coil my coils

 

[rschleicher]

The reason why clipping tends to blow tweeters is that clipping creates higher-order harmonics of the clipped signal.

A 500 Hz sine wave, driven to extreme clipping, starts to look like a 500 Hz. square wave. But this isn't DC. If you do a Fourier analysis of this square wave, you can see that it is actually a superposition of a 500 Hz. fundamental, plus all of its odd and even harmonics. In other words, in addition to the 500 Hz. fundamental, you now have a 1000 Hz component, plus a 1500 Hz. component, plus a 2000 Hz. component, plus a 2500 Hz. component, etc. etc. So you are creating lots of higher frequency components that the crossover network of the speaker directs at the tweeter.

 

[annunaki]

That is correct. The odd/high order harmonics sent through the crossover are still usually above the powerhandling of the tweeter. Thus causing excessive heat and eventually voice coil failure.

 

[mrboomble]

Thanks for all the great wisdom.

have now matched the Denon 2805 with the Klipsch RB-25's and Definitive Tech Pro Sub 80, and it all sounds great.

 

[HookedOnSound]

What's funny about the all the posts trying to explaining sources of speaker damage is no one mentionned the fact that we're talking about an electromechanical device.

Yes voice coil damage is real, so is power compression, clipping, distortion, harmonics, etc... But no one mentionned the fact that speakers can also be damaged mechanically by driving it beyond what the suspension can handle. Mechanical damage is generally caused by driving the speaker with too much power.

Most of the time, thermal damage to the voice coil is probably more common but don't forget mechanical damage.

Out of all the practical comments posted, I agree more so with MacManNM.

More Amplifier Power than Speaker rating is not a bad ideal, as long as you don't go to the extreme either like double the recommended speaker power rating.

That you would just plain silly!

The posts seemed pretty intense, lighten up folks! Listen to the music and have a great day!