Amplifier WATT vs Speaker WATT

[slimetcake]

Hi. I'm looking for an amplifier for my speakers, and I therefore have a very general question regarding this topic. I'm hoping that you can help me:

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Let's say that 2 floorstanding speakers have a sensitivity of 90.00 dB and a nominal impedance of 6 ohm. They also have a recommended amplifier power of 40 - 150 W (I'm guessing that's PER speaker?)

And then let's say that an amplifier had these specs:
2 x 125 Watt at 6 ohm
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Here's what I'm not sure about:

Does this mean that the amplifier gives 215 W to each speaker?
Would an amplifier with the mentioned specs be under- or overpowered?

Please make sure to explain why you answer what you answer. I'm new to this, so I need to make sure I understand

 

[asliarun]

Hi. I'm looking for an amplifier for my speakers, and I therefore have a very general question regarding this topic. I'm hoping that you can help me:

---------------------------------------------------------------------
Let's say that 2 floorstanding speakers have a sensitivity of 90.00 dB and a nominal impedance of 6 ohm. They also have a recommended amplifier power of 40 - 150 W (I'm guessing that's PER speaker?)

And then let's say that an amplifier had these specs:
2 x 215 Watt at 6 ohm
---------------------------------------------------------------------

Here's what I'm not sure about:

Does this mean that the amplifier gives 215 W to each speaker?
Would an amplifier with the mentioned specs be under- or overpowered?

Please make sure to explain why you answer what you answer. I'm new to this, so I need to make sure I understand

You'll generally not go wrong if your amplifier has a higher power rating than your speaker (1.5 times speaker rating seems to be the thumb rule). It is also preferable for the amp to support a lower impedance load (or at least equal) to your speakers.

For quite a while I was driving 100W speakers with 200W amp, and it actually sounded good - like the amp had full control of the speakers.

All the best in your amp hunt!

 

[slimetcake]

You'll generally not go wrong if your amplifier has a higher power rating than your speaker (1.5 times speaker rating seems to be the thumb rule). It is also preferable for the amp to support a lower impedance load (or at least equal) to your speakers.

For quite a while I was driving 100W speakers with 200W amp, and it actually sounded good - like the amp had full control of the speakers.

All the best in your amp hunt!

Hi and thanks for your answer! I just noticed that I wrote "2 x 215 W" on the amplifier I was talking about. I meant 2 x 125 (Stupid me)

I really want to make sure that my future amplifier has a high enough power rating for my speakers.

So wont an amplifier with the above mentioned power (2 x 125 W) not be underpowered for the speakers I also mentioned?
The recommended amplifier power for the speakers is 40-150 W, so I don't see how an amplifier with 2 x 125 W would be underpowered :licklips:

 

[ranjeetrain]

An amplifier could be underpowered only when it is being asked to deliver current it is incapable of. Here are some general rules of thumb.

(1) A speaker doesn't have a "required" power handling indicated. It has a "capable of handling" power rating indicated. There is a huge difference in the two ratings.

(2) If a speaker is designed to handle 40-150 watts, it doesn't mean anything other than that an amplifier should be capable of producing 40-150 watts. It doesn't mean an amplifier rated low will not work, or rated higher will blow it. It just indicates a range best suitable (safe) for speakers.

(3) An amplifier which is rated higher than what you need is less likely to damage your speakers than an amplifier which is rated lower.

(4) If your amplifier is rated higher or lower than your speakers are rated, don't drive them hard together. Play them at low to medium volume levels. They will play safe.

(5) An amplifier will only damage your speakers if (a) it is low-powered and you are playing at high volume (b) it is high powered and you turn the volume all the way up (c) there is a bad connection (short circuit) inside the amp or outside (such as at the speaker binding post).

 

[hydrovac]

I really want to make sure that my future amplifier has a high enough power rating for my speakers.

Ideally you should pick an amplifier that can deliver power equal to twice the speaker's continuous IEC power rating. This means that a speaker with a "nominal impedance" of 8 ohms and a continuous IEC power rating of 150 watts will require an amplifier that can produce 300 watts per ch into an 8 ohm load.

Using an amp with some extra "headroom" will help assure that only clean, undistorted power gets to your speakers. If budget restraints force you to use an amplifier with less power, extreme care should be taken to see that the amplifier is not driven into clipping which can result in damage to your speaker or system.
The bottom line is always buy the biggest amp you can afford if you plan to really turn it up!

 

[greenhorn]

Ideally you should pick an amplifier that can deliver power equal to twice the speaker's continuous IEC power rating. This means that a speaker with a "nominal impedance" of 8 ohms and a continuous IEC power rating of 150 watts will require an amplifier that can produce 300 watts per ch into an 8 ohm load.

Using an amp with some extra "headroom" will help assure that only clean, undistorted power gets to your speakers. If budget restraints force you to use an amplifier with less power, extreme care should be taken to see that the amplifier is not driven into clipping which can result in damage to your speaker or system.
The bottom line is always buy the biggest amp you can afford if you plan to really turn it up!

um, I think it should be the other way round!

Yes, if your amp is too underpowered, then it might damage the speakers, but if your speakers are rated 40-125W, you really dont have to get 250WPC amps to drive it properly. In fact if you run it at anything above the rated RMS of the speaker, you'll risk blowing it up. I Have had the cones of a THX certified 2.1 melt after playing it at full volume (and this is with a matched speaker/amp combo)

also, if an amp is running within its rated power, at the impedance it is rated at, and if the power of the amp is in the safe band required for the speakers, I don't see how an amp can end up clipping, or anything being damaged ?

In fact, if you buy an amp that is more powerful than the speaker, you'll always be worried about blowing up your speakers with too much power, and since you cannot measure/limit the power, you will be forced to run the amplifier at low levels all the time. Why not buy a lesser powered amp, and pump it up with impunity

My thumb rule is to buy an amp with around 75% Rated power of the maximum rated power of the speakers

 

[hydrovac]

The first thing to understand is that with solid-state amps, you get into increasingly nasty distortion (not the good kind) when you run at above approximately 1/3 max power (or volume). So be sure you buy an amp that will give you the power you want at 1/3. (If you want to push 100 watts of power, use a 300-watt amp.) Then get a speaker that is rated at about twice that 1/3 value. So for our example, we'd have a 300-watt stereo pushing 200-watt speakers at a max of 100 watts (or 1/3 volume). This gives the cleanest sound and drives the speakers hard enough with a safety margin and dynamic headroom.

I suppose I should add that if you run a 100-watt stereo through 200-watt speakers and crank it up high, the distortion created will ruin the tweeters on your speaker even though the stereo won't be kicking out anything above the speakers power-rating. That's why you don't run an under-power amplifier with high-power speakers...in addition it will be sounding, like poop.

Music isnt test tones, that is, loudness varies in real music. There are loud bits and not-so-loud bits. How much those vary is (more or less) the dynamic range of the music. More properly, because music has transient peaks that are 6 to 25 db above the average level, the power amplifier needs to produce enough power to handle those peaks without distortion.

Specifically, your amp must be able to not only produce a tone at a nominal listening value but be also able to support well-produced/well-recorded music that includes transient swings of up to +15dB at the listening position. Quiet to Very Loud. If your amp can do that, you are covered.

A speaker's Peak Power Handling is typically 4 times its Continuous Power Handling. The Rule-Of-Thumb is 1.6 to 2.5 times the speaker's continuous power rating is ideal. Keep in mind, though, that more speakers are damaged by too little power rather than too much.

Power is good, but more power is always better.

 

[greenhorn]

The first thing to understand is that with solid-state amps, you get into increasingly nasty distortion (not the good kind) when you run at above approximately 1/3 max power (or volume). So be sure you buy an amp that will give you the power you want at 1/3. (If you want to push 100 watts of power, use a 300-watt amp.) Then get a speaker that is rated at about twice that 1/3 value. So for our example, we'd have a 300-watt stereo pushing 200-watt speakers at a max of 100 watts (or 1/3 volume). This gives the cleanest sound and drives the speakers hard enough with a safety margin and dynamic headroom.

I thought this was valid only for Minicompos and those sort of devices which were rated at 10% THD. Most of the hi fi amps are rated at 1% (or much less) THD

Can you please elaborate on the nasty distortion solid state amps show at 1/3 their volume and above? I thought it was tube amps which start distorting (though its the more pleasant even order harmonic) at lower volumes, and gradually increase?

Solid state amps tend to play clean (in fact with decreasing THD) until they reach clipping, at which point their Distortion suddenly sets in rather abruptly

 

[ranjeetrain]

The first thing to understand is that with solid-state amps, you get into increasingly nasty distortion (not the good kind) when you run at above approximately 1/3 max power (or volume). So be sure you buy an amp that will give you the power you want at 1/3. (If you want to push 100 watts of power, use a 300-watt amp.)

Not sure if that's true. The best thing about solid-state amplifiers is the ridiculously low distortion. Most SS amps from reputed manufacturers these days have "inaudible" distortion at rated power. I am sure you are missing something basic.

 

[alphacentury100]

More power always good. With more power, the amp can control the speakers very well and will produce better sound.

 

[hydrovac]

YIKES!!!

Some basics:

Like it was said, solid state amps begin to distort at higher output power (when not designed right) so you should try not to overdrive the amplifier.

Now, to clipping: Again painting with a very broad brush, tube amps, because they use output transformers which do not pass DC, clip more 'softly' than some/most solid-state amps, and as that clipping is perceived as harsh and will also damage speakers, there is a perception that Tube amps sound better. At clipping, perhaps. And as a tube amp does sound better at clipping, often this is also mistaken for its being more 'powerful'.

I agree that it's mostly the softer clipping of a tube amp that makes it appear to have more power. They can run at higher power levels, clipping some, and not get obnoxious. For example, I've got a Gainclone style chipamp which sounds really pretty good until it gets into clipping. Once it clips, and that happens at a much lower volume than I'd figured, it sounds really bad - it's grating.

What one methodology does vs. another is more a result of a series of design decisions, not the methodology itself. A robust power-supply, good filtering, careful design, careful quality control and so forth will produce results entirely irrespective of whether the process is tube or solid-state. That there is a difference, as previously stated, and despite carefully cultivated rumors to the contrary has to do with behavior at the margins - and the perception of those differences is real, but the definition of the actual cause is often false.

 

[greenhorn]

Offtopic, hydrovac, do you work in management ?

 

[ranjeetrain]

Seems so :lol:

 

[jagdish_p]

Hi. I'm looking for an amplifier for my speakers, and I therefore have a very general question regarding this topic. I'm hoping that you can help me:

---------------------------------------------------------------------
Let's say that 2 floorstanding speakers have a sensitivity of 90.00 dB and a nominal impedance of 6 ohm. They also have a recommended amplifier power of 40 - 150 W (I'm guessing that's PER speaker?)

And then let's say that an amplifier had these specs:
2 x 125 Watt at 6 ohm
---------------------------------------------------------------------

Here's what I'm not sure about:

Does this mean that the amplifier gives 215 W to each speaker?
Would an amplifier with the mentioned specs be under- or overpowered?

Please make sure to explain why you answer what you answer. I'm new to this, so I need to make sure I understand

Yes it means that the amplifier gives 125 W per speaker - ( each channel)

That said note that power requirement from the speakers is varying dynamically based on the audio being played . Also some Amps are designed to provide give high transient power above their rated Watts and hence perform better.

Also keep in mind the following ( Extract from an online site)
For speakers with a sensitivity of 90 db:
90 db @1M = 84 db at 2M = 78 db at 4M (a little over 13 ft)

Therefore at 13 ft typical listening distance from the speakers:
1 W produces 78 db
2 W produce 81 db
4 W produce 84 db
8 W produce 87 db
16 W produce 90 db
32 W produce 93 db
64 W produce 96 db
128 W produce 99 db -- Not recommended to listen at theses levels for more then 2 Hours to avoid hearing loss.
256 W produce 102 db -- Will cause hearing loss.

Extrapolate the above based on your listening distance to arrive at Power requirement.

That said :

A high powered amp will have better control over the speakers and will sound better as it it will be able to handle the transient Highs requirement better. You will have to watch the Volume setting to ensure that you don't blow the speakers.

For the budget conscious
For a speaker power rating of 50W to 150W, the best operating level of the speakers will be around 100W. So the best amplifier for them would be the one with power output of 110W.

 

[kanwar]

Stop Misleading plz

The first thing to understand is that with solid-state amps, you get into increasingly nasty distortion (not the good kind) when you run at above approximately 1/3 max power (or volume).

This is ridiculously misleading to say that the distortion of the solid-state amplifier rises above 1/3 of its power in a nasty way. I don't know from where you have got this piece of misleading information regarding solid state amplifiers.


Have you ever measured an amplifier to support your technically ill-fated claim? Maybe you might have measured some poorly designed piece of crap equipment[no matter how big brand it could be]. The distortion profile of solid state amplifiers do not follow this 1/3 power rule. There are lots of variables which play an important role in making up the distortion spectrum of the amplifier.

Below is the T.H.D vs Power graph of typical SS amplifier, I fail to see your claimed 1/3 power 'Nasty' distortion rise thing in it. The THD jumps only when output touches clipping point.

 

[kanwar]

Time for you to get back to your basics

Some basics:

Now, to clipping: Again painting with a very broad brush, tube amps, because they use output transformers which do not pass DC, clip more 'softly' than some/most solid-state amps, and as that clipping is perceived as harsh and will also damage speakers, there is a perception that Tube amps sound better. At clipping, perhaps. And as a tube amp does sound better at clipping, often this is also mistaken for its being more 'powerful'.

Tube amps soft clip because of low feedback factor than SS amps, same thing can be achieved in solid state also. Transformer cannot alter the hard clipping to soft, only thing they do is that they saturate when presented with DC and the saturation doesn't makes it look like soft clipping behavior. Both are different things and both have different waveforms.

SS circuits with low feedback factor or with high local negative feedback but zero global feedback also tend to clip softly. Some people prefer zero global feedback factor for this very reason only.

A soft clipping SS amplifier with low negative feedback factor