Speaker and Amplifier compatibility. - AVS Forum
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post #1 of 12 Old 02-17-2014, 06:21 AM - Thread Starter
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Hi,

I've received an amplifier (pioneer vsx 1123) to help me start my home theatre set up and have been looking at the Jamo c607 for a while now, so i'll be looking at purchasing them soon.

I've read up a bit about power and the speaker sensitivity and was hoping someone could shed some light on this topic for me, i don't quite seem to understand it very well.

Will i have any issues running the speakers with this amplifier?

The speakers are rated at 150w/220w but the receiver is only rated at 150w peak (I'm assuming) and the speaker sensitivity is 89dB. I've been reading the amplifier RMS should match up with the speakers. Just wanted to make sure if i use the amp it would ruin the speakers (until i have the money to invest in a better amplifier ).

 

Thanks.

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post #2 of 12 Old 02-17-2014, 06:29 AM
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Originally Posted by dragong87 View Post

Hi,
I've received an amplifier (pioneer vsx 1123) to help me start my home theatre set up and have been looking at the Jamo c607 for a while now, so i'll be looking at purchasing them soon.
I've read up a bit about power and the speaker sensitivity and was hoping someone could shed some light on this topic for me, i don't quite seem to understand it very well.
Will i have any issues running the speakers with this amplifier?

None whatosever.
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The speakers are rated at 150w/220w but the receiver is only rated at 150w peak (I'm assuming) and the speaker sensitivity is 89dB. I've been reading the amplifier RMS should match up with the speakers. Just wanted to make sure if i use the amp it would ruin the speakers (until i have the money to invest in a better amplifier ).

Thanks.

A "better amplifier" won't make any difference.
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post #3 of 12 Old 02-17-2014, 06:34 AM - Thread Starter
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thanks for the quick reply.

good to know i'll be fine running this set up.

Pictures to possibly come up soon once it is set up =D

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post #4 of 12 Old 02-17-2014, 08:02 AM
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Enjoy the new home theater.
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post #5 of 12 Old 02-17-2014, 08:51 AM
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Originally Posted by dragong87 View Post

Hi,
I've received an amplifier (pioneer vsx 1123) to help me start my home theatre set up and have been looking at the Jamo c607 for a while now, so i'll be looking at purchasing them soon.
I've read up a bit about power and the speaker sensitivity and was hoping someone could shed some light on this topic for me, i don't quite seem to understand it very well.
Will i have any issues running the speakers with this amplifier?
The speakers are rated at 150w/220w but the receiver is only rated at 150w peak (I'm assuming) and the speaker sensitivity is 89dB. I've been reading the amplifier RMS should match up with the speakers. Just wanted to make sure if i use the amp it would ruin the speakers (until i have the money to invest in a better amplifier ).

Both amplifier and speaker power ratings are significantly inexact. The amplifier ratings are inexact because most of them are based on tests with pure sine waves and resistive loads, as opposed to music and speaker loads. The speaker ratings are inexact because there are no generally agreed upon, generally adhered to standards for the power capacity or acoustic sensitivity of the speaker.

There is an audiophile myth that using a speaker with an amplifier that is too small will permanently damage it. I suspect that part of its charm is that it runs against common sense, and another big part of its charm is that it can be used by agressive sales persons to bully people into buying more expensive amplifiers.

Referencing:
http://www.pioneerelectronics.com/PUSA/Home/AV-Receivers/Pioneer+Receivers/VSX-1123-K

If we wish to even roughly estimate the actual amount of power that you need, we need the following pieces of information:

(1) The preferred maximum loudness (SPL) in dB.
(2) The actual sensitivity of the speaker, not the "Marketing number" that some manufacturers bandy about
(3) The distance from the speaker to your preferred listening location to the speakers

For example using:

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

And:

Amplifier music power 165 watts/channel
Loudspeaker sensitivity 89 dB/W
Listening distance: 8 feet
Number of speakers:3 (LCR)
Speakers located near a wall

gives

112 dB SPL

Anything above 105 dB would be more than fine for even a fairly loudness-centric audiophile.
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post #6 of 12 Old 02-17-2014, 09:12 AM
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Originally Posted by arnyk View Post


Both amplifier and speaker power ratings are significantly inexact. The amplifier ratings are inexact because most of them are based on tests with pure sine waves and resistive loads, as opposed to music and speaker loads. The speaker ratings are inexact because there are no generally agreed upon, generally adhered to standards for the power capacity or acoustic sensitivity of the speaker.



le.

Absolutely Correct!!

The tiny amount of distortion almost any amplifier produces when driving a resistive load is no indication of how much distortion it will produce when driving an actual speaker, which is a much more difficult load for an amplifier to drive due to capacitive and inductive reactance.

The actual distortion driving a speaker may be 100 times as much. That is why it is critical to LISTEN to the amplifier and speaker COMBINATION you are considering; not just one or the other. You can look at numbers all day and find out more by LISTENING for 20 minutes.

Cheap amplifiers and AVRs generally produce much greater distortion when asked to drive real speakers, compared to better-designed amplifiers. Looking at specifications is only a starting point. Anyone who tries to draw conclusions based on them alone is making a big mistake, because they only give you a very limited amount of information.

Testing an amplifier with only a resistive load is like testing a high-performance car only on a dynomometer and never on the road. You get only a very small amount of useful information in both cases. That is why published specifications tend to be almost useless as an indicator of actual audio performance in the real world.
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post #7 of 12 Old 02-17-2014, 11:10 AM
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ummm, actually, afaik while the differing impedance presented by speakers can theoretically challenge an amp, it all depends . . . for example, if a speaker dips to 2 ohms at say 60 Hz, then when there's a 60 hz component to the sound, the amp does not see a 2 ohm impedance. Instead it sees something like the sum of the complex impedances at all the frequencies it's reproducing. If the 60 Hz component is even 25% of the power requirement for a particular sound, it still may be well within the amp's comfort range even at 2 ohms because the power requirement is not pushing the amp very hard. . .

Moreover, as Arny frequently points out, actual music is a lot easier to reproduce than a sine wave. A sine wave has essentially zero dynamic range. Music has lots. Until the master is very very compressed, the leading edges that are going to distort first may be 3 to 10 dB above the average, and last something like a 20th of a second. Once you get the power requirement cut in half or by a factor of 10 (ie after that 20th of a second) any distortion will go away. It may be that people actually like the sound of distorted leading edges (I like tube amps for audio as well as for my guitar, although I push the tubes significantly harder in my guitar amps). My enjoyment is almost certainly related to INaccuracies of specific tube amps in hifi, not to some imaginary increased ability to pull out more detail or otherwise sprinkle magical fairy dust on the audio. I just happen to like the particular set of inaccuracies (distortion, compression, frequency response anomalies especially at the frequency extremes). I don't happen to have any tube components in my sound reproduction system these days though. Although I have 3 different tube guitar amps (horses for courses) and would, if I had the means, probably have at least a dozen.
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post #8 of 12 Old 02-17-2014, 12:00 PM
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Originally Posted by commsysman View Post


The tiny amount of distortion almost any amplifier produces when driving a resistive load is no indication of how much distortion it will produce when driving an actual speaker, which is a much more difficult load for an amplifier to drive due to capacitive and inductive reactance.

It is true that there are several other parameters that need to be considered when predicting the distortion delivered to a real world load:

Major influences are the source impedance of the amplifier and the actual degree of nonlinearity of the speaker load.

The source impedance of a power amplifier is its rated impedance divided by the damping factor. A typical SS amp has a damping factor of 100 or more with an 8 ohm load, so its source impedance is 0.08 ohms or less.

The fact that the speaker load has reactive components does not automatically force the amplifier to spew large amounts of nonlinear distortion. Those reactive components in a speaker are generally fairly linear or have a high impedance. Put the low source impedance of the amplifier together with the natural linearity of speakers and the additional nonlinear distortion is generally below 0.1% and therefore either very hard to hear or totally inaudible. It is generally lower than the distortion in the loudspeaker itself.
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The actual distortion driving a speaker may be 100 times as much.

Not under even normal peak level listening conditions. Not true at all for normal levels.
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Popular priced amplifiers and AVRs generally produce much greater distortion when asked to drive real speakers, compared to better-designed amplifiers.

Not at all. Popular priced amplifiers such as are found in AVRs have low source impedance and low distortion just like any other good SS amplifier. There is only so much that can or even needs to be done to lower the distortion of SS power amps. The SS devices and the parts that go with them have become widely available and competitively priced.
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Testing an amplifier with only a resistive load is like testing a high-performance car only on a dynomometer and never on the road.

Tests of both AVRs and stand alone power amps with speaker like loads do not generally reveal any surprises. To study this issue further, about 15 years ago I built a loudspeaker simulator that has an impedance curve that is similar to a fairly demanding loudspeaker:



Note that it dips about twice as low as the one used by a well known high end magazine:



When I tested amplifiers with this loudspeaker simulator I found that the power drain and heating was far less than with a regular 8 ohm resistive load. The loudspeaker simulator included some nonlinearity, but distortion measurements made using it did not increase dramatically, and in fact they were often less.

Here is a test summary for a low cost power amp with resistive and loudspeaker simulator loads:



This is a measurement of the source impedance provided by this power amp:



The scale of this graph is that 1.0 on the graph corresponds to a source impedance o 0.01 ohm.
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post #9 of 12 Old 02-17-2014, 07:13 PM
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Originally Posted by JHAz View Post

ummm, actually, afaik while the differing impedance presented by speakers can theoretically challenge an amp, it all depends . . . for example, if a speaker dips to 2 ohms at say 60 Hz, then when there's a 60 hz component to the sound, the amp does not see a 2 ohm impedance. Instead it sees something like the sum of the complex impedances at all the frequencies it's reproducing. If the 60 Hz component is even 25% of the power requirement for a particular sound, it still may be well within the amp's comfort range even at 2 ohms because the power requirement is not pushing the amp very hard.
Unfortunately the impedance is insufficient to make such a determination. You must also have the phase response. That tells you how much current and voltage are out of sync. The more they are out of sync, the harder it is on the amplifier. This is something that does not happen with resistive loads. Notice how the stereophile graph that Arny post has this phase response (dashed line overlayed the solid impedance graph) but his own dummy load does not. We have no idea then how hard of a load Arny's dummy load really is.

A 2 ohm impedance with 45 degree out of phase is a far different load than the same 2 ohms with 0 degrees. At the (unrealistic) extreme, the current could be completely out of phase with voltage. This means that the amplifier will see a dead short and yet still has to provide lots of current. This is a far more difficult load than 2 ohms with zero phase difference.

So this analysis can only be done if the measurements of both phase angle and impedance of speaker versus frequency is available. Manufacturers almost never provide this so you are at the mercy of Stereophile for such information.

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post #10 of 12 Old 02-18-2014, 02:44 AM
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Quote:
Originally Posted by amirm View Post

Quote:
Originally Posted by JHAz View Post

ummm, actually, afaik while the differing impedance presented by speakers can theoretically challenge an amp, it all depends . . . for example, if a speaker dips to 2 ohms at say 60 Hz, then when there's a 60 hz component to the sound, the amp does not see a 2 ohm impedance. Instead it sees something like the sum of the complex impedances at all the frequencies it's reproducing. If the 60 Hz component is even 25% of the power requirement for a particular sound, it still may be well within the amp's comfort range even at 2 ohms because the power requirement is not pushing the amp very hard.


Unfortunately the impedance is insufficient to make such a determination. You must also have the phase response. That tells you how much current and voltage are out of sync. The more they are out of sync, the harder it is on the amplifier. This is something that does not happen with resistive loads. Notice how the stereophile graph that Arny post has this phase response (dashed line overlayed the solid impedance graph) but his own dummy load does not. We have no idea then how hard of a load Arny's dummy load really is.

It is amazing to me how many will damn the darkness and refuse to politely ask for a candle! Ask and ye shall receive!





Again, a copy of the same data for the well-known load from the GE magazine:



As you can see, my load is more taxing in both ways, both impedance magnitude and also impedance phase angle. Would you expect anything less from me? ;-)

One irony is that I developed my load using impedance curves from the same source. I threw out one or two outlers and made my load the equal or superior (in terms of difficulty) to the rest.

One advantage that I have is that I will never place my load across the terminals of a > $100,000 and be tempted to try to explain away the mess that results to please an advertiser or manufacturer that I am representing.

BTW I challenge one and all to provide the results of tests of power amplifiers that are as complete as this summary information, in regards to performance with resistive and loudspeaker-like loads:

Cheap PA amp:



Well known, widely respected high end amp costing the proverbial many times more:

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post #11 of 12 Old 02-18-2014, 07:04 AM
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Originally Posted by amirm View Post

Unfortunately the impedance is insufficient to make such a determination. You must also have the phase response. That tells you how much current and voltage are out of sync. The more they are out of sync, the harder it is on the amplifier. This is something that does not happen with resistive loads. Notice how the stereophile graph that Arny post has this phase response (dashed line overlayed the solid impedance graph) but his own dummy load does not. We have no idea then how hard of a load Arny's dummy load really is.

A 2 ohm impedance with 45 degree out of phase is a far different load than the same 2 ohms with 0 degrees. At the (unrealistic) extreme, the current could be completely out of phase with voltage. This means that the amplifier will see a dead short and yet still has to provide lots of current. This is a far more difficult load than 2 ohms with zero phase difference.

So this analysis can only be done if the measurements of both phase angle and impedance of speaker versus frequency is available. Manufacturers almost never provide this so you are at the mercy of Stereophile for such information.


+1
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post #12 of 12 Old 02-18-2014, 10:26 AM
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A 2 ohm impedance with 45 degree out of phase is a far different load than the same 2 ohms with 0 degrees. At the (unrealistic) extreme, the current could be completely out of phase with voltage. This means that the amplifier will see a dead short and yet still has to provide lots of current. This is a far more difficult load than 2 ohms with zero phase difference.

Every impedance has a real (resistive) and imaginary (reactive component). The real component of a loudspeaker's impedance is generally primarily established by the DC resistance of various components of he speaker. Therefore impedance minima occur when the reactive component is minimized.



The above is a typical 3 way direct radiator loudspeaker system and we see that the points of minimum impedance (300, 1200, and 17 KHz) correspond to minimum (about zero degrees) phase angle.



The above is a 2 way electrostatic loudspeaker with an active woofer and again we see that the points of minimum impedance (400, 20 KHz) approximately correspond to lesser phase angles. The correspondence is not as tight as with the conventional direct radiator, but 30 degrees and a magnitude > 6 ohms still indicates a reasonable load.




The above is the impedance curve of a ribbon speaker and again the region of minimum impedance magnitude (2-4 KHz) is approximated by the region of minimum or low phase angle.
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