Does power(watts) affect listening ?

Have a simple question:

How much would the wattage of the speaker/amp setup affect in music listening ?

Apart from volume, is there any advantage in buying a 100W speaker over a 80W speaker ??

Would the diaphragm of a 100W speaker move, more back & forth, than that of a 80W speaker setup ?

Most speakers have a lower and upper limit in terms of their wattage. The lower number represents the minimal power needed to drive the speaker. The higher number represents the power at which the speaker will start clipping or distorting. It is not advisable to drive a speaker near it's upper power handling capacity.

Wattage by itself may not give the complete picture. You have to consider two other factors. One is sensitivity. This is measured in dB and represents the efficiency with which the speaker converts the power supplied to it into sound. The higher the number, the more efficient the speakers are. For example, a 3dB increase in sensitivity can produce the same amplitude of sound as doubling your amps output. Speaker sensitivity defines the quantum sound output delivered by a speaker with one watt of power input from an amplifier. Sensitivity is needed to determine the amount of power necessary to drive a speaker.

Another factor is called impedance. Impedance is measured in Ohms, and represents the amount of resistance the speakers provides to electrical current. The lower the impedance, the easier it is to drive a speaker. Impedance is also specified for a amp. Generally it is advisable to drive a 8m ohms speaker with an amp that can deliver x watts of power at 8 ohms. Many people are attracted to drive a 4 ohms speaker with an amp that is rated at, let us say, 50 watts at 8 ohms. They do this thinking that the amp will now be delivering 100 watts at 4 ohms which is the impedance of the speaker. Though in theory this is correct, the speaker will be clipped very quickly and start distorting. It is important to match the speaker and amp's impedance and wattage as close as possible.

Sound is transferred by air pressure. So theoretically what you say is true. A speaker with more wattage or power should push more air. But this may not be true in terms of the movement of the diaphragm of the speaker. The air pressure is not produced by the movement of the diaphragm alone. The cabinet construction also plays a major part

Diaphragm movement depends a lot on the material used for making the diaphragm. Many speakers use silk and paper cones for easy movement of the diaphragm. But there are speaker that are made of special material such as Kevlar. These material are stiffer and thus the resistance of the speaker will be higher. Such speaker need more power, but deliver a smoother and more transparent sound.

Thus it is not just the wattage, but a combination of wattage (or power handling capacity), sensitivity, and, impedance that go to define speaker.

Cheers

Wattage ratings on speakers are pretty meaningless, IMO. I don't regard the specification, except as a cautionary measure. The rating is a measure of power handling, not output.

The closest example I can point you to is an appliance that draws 100 watts from the mains. This is about .5 amperes. If you connect it to a 5 amp socket, it will perform identically to when it is connected to a 15 amp socket.

Speakers and amplifiers follow this logic, only slightly differently. Speakers transform electrical power into sound pressure. A "100 watt speaker" and an "80 watt speaker" of identical sensitivity will provide exactly the same sound pressure given the same amount of power input. The 100 watt is to be taken as a input limit, not a measure of output.

That said, it is wise to oversize the amplifier when choosing a combination. Modern speakers have very low sensitivity (<88dB/W) and require at least 50 watts of clean power. Amplifiers on the other hand, are mostly over-rated and can clip at the top end of their power range. Clipping generates high power square waves at high frequencies, which can damage speakers. Tweeters are specially vulnerable.

Amplifiers, depending on how they are built, will provide their best electrical performance at some defined output level. It is wise to choose a combination that will allow the speakers to provide normal listening levels at this sweet spot of amp performance. The Pass First Watt for example, is an amp line that is optimised for superb measured performance in the ~1watt range, which is where most of us listen at anyway (unless, like me, you have 85dB/W speakers). Chipamps also provide superb linearity in those kind of outputs, and so these are to be mated with high-sensitivity speakers (90dB/W or greater). Most low-bias tube amps show most of their THD+N in lower output levels (there are exceptions, but I prefer tube amps when they are operating near the top of their range), and mass-market cool running amps need to be cranked the middle of their powerband but run out of steam at the top end.

In most cases you will hear speakers in distress, as they die of mechanical failure much quicker than electrical. The former is caused by over-excursion and the voice coil hitting the stops, the second by cranking it till the voice coil melts. Unless you're deaf or blind (or both), it's tough to damage a speaker with too much power. The only reasons for VC failure are due to DC at amp outputs, or some subtler physical effects such as spider sag or foreign matter in the VC gap.

Watts do make a difference, but it's not as simple as you think. They need to mate well to your speakers, your room, your tastes. If you want speakers that move in and out, maybe you need a sine wave generator and a subwoofer, that will move in and out a lot. For music, things get a little complicated. Excursion is governed by driver dimensions and construction, cabinet design and kind of music being played. A 12" subwoofer will have to move a lot less to move the same air as a 4" driver, or will go much deeper and louder for the same movement.

At a general level, high power equipment is less stressed at a given output level, provided the additional power is not wasted on less efficient speakers. In no way is a 200 watt speaker better or worth more than a 20 watt speaker.

dont worry about watts too much. its the sound quality thats more of an issue. during normal listening you dont use more than 30w. perhaps 50 in some cases - by then its already very loud. so dont let the diff between 80w and 100w be the judge for choosing

duh! Do you mean to use solid state class D amps as generic term for chipamps?
I didnt understand the following logic of why chipamps need high sensitivity speakers...

duh! Whats a low-bias tube amp?

Regards

I read my post six times over, and cannot find a single reference to "Solid State Class D". Would be grateful if you pointed it out to me. Even Microsoft Word could not find it in the post - much as I mistrust the company, the word search works fine. As a matter of fact, even the words "solid", "state" and "class" don't feature anywhere. I don't mind you tearing my posts apart, but do extend me the courtesy of reading them.

As for your post, let me try and reply.

Chipamps are the generally accepted term for single-chip Class AB amps such as those built by National (LM 3xxx series), SG (TDA72xx), and BB (OPA 5xx) among others. Technically the Tripath and TI chips which are Class D on one chip are also "chip" "amps" but the community which has coined the term "chipamps" (of which I am one) does not extend the definition to these. Also the Sanyo STK series are not chipamps, they are hybrid amps with discrete components, mounted on to one die and encapsulated with plastic. Anyway,

Generally due to their compact size it is challenging to get more than 50 watts of power out of these chips, and at those levels distortion is quite high with little headroom. Would you like to see the datasheets? Head over to National or TI, or if you want, PM me your email ID and I'll send them to you.

This is common for almost all amps with under 50 watts of power output. Unfortunately, most chips have very aggressive protection circuitry which tends to cut in at the chip limits - and most of us using these kind of chips seem to think it cuts in a little earlier. So we don't advocate running these much beyond the half-power mark for a given chip. That's 30 watts or so, at the most. Which is the exact spec of, say, the Cambridge Audio 340A, which uses a 70 watt chip by NatSemi. 30 watts, you do the math now as to what efficiency you need on your speakers to fill an average room with sound.
As to your question on bias:

In general Class-A SET amps are operated at anywhere between 100mA and 200mA of plate current. These would be high-bias amps.

A typical PP tube amp, on the other hand, would operate at less than half that. 30mA is a safe bet, sometimes even lower. These amps sound best in the middle or the top end of their performance range due to the rise in residual plate noise at low output levels. SETs operate at a much higher current and therefore have less issues with noise, though tube life is shorter.

I can't explain it in any more simple terms, sorry about that.

I think I need to reopen this thread to get more focussed info on my doubts.

My doubts are slightly different. How does the 'Wattage' value of the 'AMPLIFIER' affect listening.

For example, Lets say I drive a same set of speakers with amps C315BEE and C325BEE. Now, There is not much difference between the two amps except the continuous output power rating of 40W vs 50W. But the difference between the prices of these two amps is 7k. Is the 10W power increase justify the price increase of 7k?

On reading the above posts, I am forced to believe that there is not much difference between a 40W and 50W amp, all other parameters being same. Given that who will buy a high powered amp for non-linear high price?


Also, Let us say a speaker has a input range of 20W - 200W @8ohms. Assuming I hear the music @ sane volumes and am not going to make my doors vibrate, Can I better of go about buying a low wattage (25W) amp from a more audiophile level manufacturer than compromising for a 150W amp by a lesser quality manufacturer? What will be the difference in sound quality in that case?
In short, What is the difference between the listening experience using a 150w amp and a 30w amp @ the SAME volume level?

If output wattage of amps have such low importance (as I understand), Why are high wattage amps manufactured at all? Can't all the amps be manufactured with say 50 wps so that comparison becomes more easy?

Thanks,

Watts can affect SQ with same spk.
I took audition of Norge2060(80w) & 1000(100w) with my Tany F1 & found that 1000 gave better sound than 2060 ,may be due to wattage of 1000 is100w.

though my spk can match with 20 to 50w amp,100w sound was pleasant.

You are asking a lot of questions which I will try to answers in generic terms:

All that the wattage is saying is how much power the amp can deliver when asked to do so by the speaker. The metric is very misleading due to how manufacturers tend to report them.

For the most part its not much as most efficient (8 ohm impedence speakers) are very easy to drive and will hardly test the limits of the amp. The closest analogy is the odometers in our cars. Even though the one may have the max speed of 120 km/hr vs. 160 km/hr, the limits will hardly be tested when everyone is driving at 20 km/hr.

WRT to the NAD amps, people are saying there is not much difference because these typically are not stressed to hear even though theoretically there should be a difference between them.

Reason people buy higher powered amps is that there are certain parts during audio when the amp will be stressed to its limits (also called peak power). During these times, it is easier for a higher power amp to handle than a lower powered ones. Mind you these are rare occurances but they do occur. Going back to my analogy above, if you end up driving at 100 km/hr then the more powerful car can easily achieve this than the latter.

Hi Blasto,

You have asked, I think, some very relevant questions. I also do have very similar questions in my mind and of late have bored people to death by asking very similar questions in my very long amp thread.

I can try to explain my current level of understanding at this point.

Let's first clarify one thing: the 40 Watts or 50 Watts that you are talking about in your post are what is called the rms power continuously deliverable at a given speaker load (usually given for 8 Ohms). However, the continuously deliverable rms rating is NOT the maximum power that the amp is capable of delivering. A well-constructed amp may be able deliver for a very short time period an amount of power much much higher than that power rating. This is very important for music reproduction, because in music there are quieter periods, and then there are sudden bursts of energy. Because of this the above mentioned power-reserves, called dynamic headroom, are a must.

The other aspect is the amount of power that the amp can deliver for different speaker-loads. As the music flows, it involves different frequency components at different times. The speaker impedances change with frequency. That actually means that the amp sees the speakers as loads where the impedance is changing continuously with time. Now from the Physics formula relating power, voltage and impedance you would discover that as the load-impedance is lowered the power requirement is higher if you keep the voltage fixed. So you see, as the music is being played, the amp is doing a tremendously non-trivial job of delivering an expected level of power to a load where the impedance is continuously changing.

That's why more than the speaker sensitivity, its impedance as a a function of frequency (this in general depends also on the power) is an important aspect. On the amplifier side, some of the things to look for is the available power as the impedance changes and also as the frequency changes.

Now you can guess what would be the ideal situation. For the speaker, the ideal situation should be the impedance completely independent of frequency (at least within the relevant range of 20 - 20KHz). This is usually called the flat response because an impedance vs frequency plot would look perfectly parallel to the frequency-axis of the plot.

The ideal amp (at least with respect to the things we are discussing here) would be one which would exactly compensate for a reduction of speaker-impedance. For example, a 50 wpc@8 Ohm amp would become a 100 wpc@4 Ohm or a 200 wpc@2 Ohms or 400 Watts@1 Ohm. BTW, this does not usually happen for low-priced amps.

Also, ideally, at a given speaker impedance, the amp should deliver power independently of the frequency.

Obviously, there are many many other aspects for the amp (and also for the speakers), especially with respect to distortions. The THD rating given as an amp spec. is also very misleading. Two amps having the same THD can have very different distortion patterns. In addition, distortions in lower harmonics are generally considered better. Also odd and even harmonics make a difference. To top it all, all these can change at different power.

So after all this mumbo jumbo, what is the conclusion? What we common people should do?

To answer one of your questions, yes, a 50 Wpc@8 Ohms amp should be enough for all kinds of listening at home, even for large rooms and at deafening volumes (look at my table in a recent post in my amp thread), provided the amp is close to having the ideal characteristics as described above and also having enough dynamic headroom to accommodate a sudden 15db or so (at a max, even good recordings usually do not have this kind of dynamic range) volume increase.

Obviously in the budget segment, you do not often find an amp of 50 wpc@8 Ohm to have even close to the nice characteristics described above. But this discussion should be a pointer to a few things. For example you would notice that in the market there are some 50 wpc amps at less than 20K and some other 50 wpc amp at 40 or 50 K. There are even 25 wpc amp at close to a lakh. Obviously some of the price difference can be due to business-related economics, but in general there IS a difference.

At least for SS (solid state) amps, that's why people want to make sure that at least some of the ideal characteristics are somewhat approached by buying an amp having a power rating much higher than the actual requirement.

So, if all the ideal characteristics are met including the one for dynamic headroom, there should not be any difference of sound between the 40 wpc Nad 515 and 50 wpc Nad 525 producing the same volume at the same speaker-set (assuming the two amps are 'voiced' the same way). Now based on the above discussion, you know that there is enough reason to believe that there can be many other significant differences between the two amps which can make a real difference in the sound produced by the two amps.