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How to avoid clipping with a weaker amp

rochester21

rochester21

Active Member
I always wonder, especially after reading "Amplifier sensitivity, decibels and you" how exactly I can use my amps efficiently, meaning getting ~full power but without getting into clipping territory.

I will give an example. I am building a secondary system around a pair of Dali Zensor 3 bookshelf speakers(88db), thinking of pairing it with a small amp, which I have two of. One of them is a Sony dhc-md333 mini reiceiver, which has a declared power of 25+25w DIN/6 ohm.

In theory, this means I can push the Dali speakers up to around 40w without damaging them, but I'm not sure how loud 40w is. I assume plenty?

The position of the volume knob is not relative here, so I'm into guessing territory. I don't listen to really loud levels, but I want to be able to feel the music, so I can't be wisper quiet either.

The main thing Is not to damage the Dali speakers, because I like them a lot.

Even if I upgrade the amp to something better but also small, the question remains, how to avoid clipping on any speaker/amp combo.

I trust my common sense and my ear, just wanted to hear other people's opinion on this. I have never pushed a speaker past a certain point specifically because I wasn't sure how loud I can really go without damaging something.
 
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Most people will tell you to trust your ears.
It should be pretty apparent when speakers are being overdriven.
They will start to sound different in a bad way.

But it is the amplifier that is clipping and not the speakers. Speakers can be overdriven with too much power but an amplifier clips when it is being asked to produce more power than it can.

I often rock the house -I always look forward to my wife taking a shower!- and let my ears be the judge. My amps -Adcom GFA555 II's- also have "instantaneous distortion" LED's that are supposed to start working before clipping occurs. I've driven things hard enough to get them to flash on occasion -usually on some big bass hit or something like that- but by that point I am already being cautious despite how loud it may be.
 
It's not particularly precise, but you can use an SPL meter to measure peaks in output.

And you can do the math to figure out how loud your speakers will get with your amp's maximum rated RMS output at a given listening distance. Or use an online SPL calculator to do it for you.

Play some dynamic music and watch the SPL meter as you gradually nudge up the volume. When you start seeing peaks close to the maximum SPL that you calculated, you are at the amp's limit. Beyond it, you are clipping the signal.

Minor clipping is not a major concern, but it will ramp up quickly.

That amp would drive those speakers to a continous output in the mid-80 dB range, at a normal indoor listening distance, while maintaining an adequate reserve for peaks. A bit louder if the recording is heavily range compressed (like most mainstream pop/rock music).

Curious as to your 40 watt calculation?
 
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odcics2 said:
Hmm, in my room, 16 x 12, 8-foot ceiling, 1-2 watts is a normal listening level.

My days are over driving speakers to ear splitting levels and melting tweeters!
Click to expand...

That might be loud, quiet, or somewhere in between...depends on the speakers, your listening distance, and room characteristics.

Are you referring to continous output or peak?
 
If you are listening to music that is at a fairly constant level (which describes most popular music), you can gradually turn up the volume control until you start to hear the sound distorting, and then turn it down until the distortion goes away. That will generally be the loudest your system can safely play. (That won't tell you whether it is the amplifier or the speakers that are limiting you, but at least one of them is, so you need to turn it down to the point where you don't hear distortion.) Of course, this procedure assumes you are not deaf and can hear when it distorts.

However, you cannot rely on that position of the volume control always being okay, because a stronger signal coming into the preamp will result in a stronger signal going out of it.

Also, that is not much help for playing something like the original Telarc CD of Tchaikovsky's 1812 Overture, as the cannons are a sudden increase in volume, and if you were playing the music before it at the loudest safe volume, the cannons would be too loud, potentially damaging your system. The same idea applies to all music with a wide dynamic range. The best I can do for you is this: Do the "test" in my original paragraph, and then when playing Tchaikovsky's 1812 Overture, go to the part with the loudest cannon (make sure you get that right, as a mistake can result in damage if you pick a softer cannon blast), and slowly and carefully adjust the volume until the canon is equally loud with what you came up with in that test. That will be the loudest you should play that disc, and I cannot tell you where on your volume control that will be, or whether you will find that loud enough during the soft portions of the music. If you have ordinary speakers and a low powered amplifier, very likely, you will not be able to play that disc at a satisfactory volume.

This brings me to another point. If you want to properly listen to music with a very wide dynamic range, you need to either have a lot of power (along with speakers that can handle a lot of power), or very high sensitivity speakers, or both, to be able to get the full dynamic range and have the soft portions of the music loud enough to properly hear them. In other words, a cheap system may be fine for most music, but properly playing something like the original Telarc CD of Tchaikovsky's 1812 Overture requires a pretty good system.

Also, of course, music with a very wide dynamic range is not suitable for background music, because in order for the soft parts to be properly audible, the loud parts will be very loud. If you go listen to a live symphony orchestra, with no amplification (just listening directly to the instruments), they can play so softly in a concert hall that one can barely hear them, and so loud that one can barely stand it, with all possible volume in between. A good system can reproduce that.


Edited to add:

It is easier if you have power meters, as you then can judge based on the readings when you are approaching the limits of your amplifier. When I had a Pioneer SX-780, which is rated at 45 watts per channel and has power meters, I used the meters, and when they were jumping up a little past 45 watts, I did not turn up the volume any higher, and so I did not turn it up until it audibly distorted to find approximately the highest safe level for it. But, if you get distortion before you turn it up that high, you need to turn it down. It would mean that the speakers can't take the power, assuming that the amplifier is properly functioning.

Most of the time, when I was using that receiver, the power output was around a watt or two, but when, on relatively rare occasions, I wanted to listen to something fairly loud, the power demands go up fast (as it takes a doubling of power for each little 3dB increase in volume), and then 45 watts was not enough to get what I wanted.
 
odcics2 said:
Hmm, in my room, 16 x 12, 8-foot ceiling, 1-2 watts is a normal listening level.

My days are over driving speakers to ear splitting levels and melting tweeters!
Click to expand...
That's what I've heard as well, meaning I am in the safe range at normal listening levels in a small room. Thanks!
 
Your Sony amp is rated at 25 watts (RMS), but at 10% distortion. I would guess its RMS rating at 1% would be more like 10-12 watts...and maybe even less.

With your Dali speakers, and using my assumption about RMS power, you would get a continuous output (SPL) of around 85dB at 8 feet in a typical room, while maintaining a 9dB "reserve" for transient peaks. 82dB with a 12dB "reserve".

Low to mid-80s is fairly loud, but not LOUD. As you drop below that, you are at conversational levels, and then down to background levels.

I try to size my amps to provide at least a 15dB reserve above the loudest continous output I want to be able to achieve on a sustained basis, but 9dB is probably adequate with music of moderate dynamic range.

In any case, if the sound starts changing (harsher, compressed, notably distorted, etc), turn it down; either the amp or the speakers are reaching their limits.

As mentioned by @daveshel, try to avoid boosting bass with the tone control or loudness function, as doing so will substantially reduce available power.
 
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The thing to pay attention to is the efficiency of the speaker. A more efficient the speaker is, the less you have to pull from the amp.
 
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