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volume is not absolute!!


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On 10/10/2002 2:48:55 AM maxg wrote:

Yes - a lot off questions - and it is a bit difficult to answer them all.

I suppose the best place to start is how watts translate into db.

The basics are that for every 3dB jump in volume you need to double the power.

Starting with your speakers as the basis (99 dB/w/m):

99 dB - 1 watt

102 dB - 2 watts

105 dB - 4 watts

108 dB - 8 watts

111 dB - 16 watts

114 dB - 32 watts

117 dB - 64 watts

120 dB - 128 watts

From memory your speakers in common with most Klipsch models can handle upto 100 watts continuous / 400 watts peak.

Therefore the maximum continuous volume your system is capable of producing is theoretically about 118-119 dB which is ear damagingly loud for exposures beyond about 10 minutes.

I should add that these are the ratings in an anechoic chamber at a distance of 1 metre. For every metre further away you can reduce the dB by 6. Therefore if you are sitting 3 metres from your speakers with 32 watts comming from your amp you should be listening to music at something around 102 dB or thereabouts.

In my language 102 dB is plenty loud - far louder in fact than I would ever listen to music. The highest figure (continuous) in my listening position I use is about 90dB and then only when the wife and baby are out and only for rock music. (Note - there are others on this forum that will laugh out loud at that figure but I am keen on retaining my hearing for the foreseeable future and imho they are taking a risk).

As most of my listening is done at about 84 dB, even taking into account I am 3 metres from my speakers you can see that with your speakers I will be running at 96 dB from a distance of 1 metre or 0.1 watts from the amp.

This is where the advantage of tubes comes in. At outputs of less than 1 watt it is generally accepted that tubes are less distorting than SS amplification.

The issue is not that a 3 watt tube amp will play louder than a 3 watt SS amp (if such a thing existed) but that for the majority of normal listening the tube amp will suffer less distortion that the SS amp.

I should add that some makes are notorious for over-stating their outputs. Just because a given make of receiver is declared to be 100 watts does not mean that it actually is. There appear to be a variety of tricks the manufacturers use to make these numbers look bigger as watts sell amps.

In summary a 3 watt tube amp will not play louder than a genuine say 30 to 70 watt SS amp. At 104 dB it will probably clip like the devil on the peaks, but, at levels of, say 95 dB it should sound gloriously better.


Nice analysis, Max, only you tend to forget two important things:1) Speakers (yes, even the most sensitive ones...) transform the bigger part of amplifier power into heat! 2) That said, one should also add that an important part of - almost any - music are transients. And correct reproduction of these transients demands huge amounts of power for very short periods of time. Hence the "school of thought", recommending the use of sensitive loudspeakers with powerful amps, for best reproduction of music in the home.

Of course, like in every thing Hi-Fi, what you choose to drive your speakers is (and, I am afraid, it will always be...) a matter of personal tastes and priorities. An 250W/ch transistor amp coupled to a pair of KH's, will never have the magic and "inner light" of a small SET, although it could be expected to do bass and dynamics better, than its smaller sibling. And, of course, there are innumerable "middle of the road" solutions out there. Last but not least, sensitive loudspeakers in addition of having a big headroom combined with low distortion, offer their proponents the flexibility of being able to audition, say, Shirley Horn on a 45 amp and Mahler's symphony of the thousand on a x100 more powerful amp. That's exactly what I do!

But I digress: Just put a dB meter in your listening position and try the music you like best, played by different amplifiers. You will quickly discover that the amp finally chosen (if only one!), will be the one which most satisfies your personal criteria. Not the theory! At the same time, another person will very probably choose an amp with quite different characteristics and be as happy.

See you next week,

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"1) Speakers (yes, even the most sensitive ones...) transform the bigger part of amplifier power into heat! "

This is, I think, one of the reasons you have to keep doubling the power for a lowly 3 dB increase, although I must say I thought it was amps that generated the heat rather than the speakers.

Basically the more power you generate to drive your speakers (wherever the main loss actually is) the smaller the proportion of that power that is translated into sound.

In other words - not forgotten - merely another way of saying the same thing.

As regards a week on Sunday I think you are down to visit Tony's. Planning to pop over to me too?? I have a piece of vinyl you are looking for if you do (unless you want me to give it to Tony).

See you soon anyway.

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Methinks I had a technical problem! Here's the reply:


You always need to double amp power for a 3dB increase in SPL and this, regardless of speaker technology or sensitivity. If, for example, you need 0.25W for a given SPL, at a certain point, with a sensitive speaker, then for SPL+3dB you will need 0.5W. With a less sensitive speaker, you might need 40&80W for the same result. So much with the theory... Yes, but of which speaker are we talking about? Because, you may have a, say, 91dB/W/m speaker with such a complex impedance profile (i.e. strong phase shifts, goes down to 1Ohm in critical parts of the spectrum etc) that no tube amp, which is essentially what we call a "voltage amplifier", will be ever be capable to do it full justice. Here, you absolutely need a transistor amp able to deliver high current into low impedances and - believe me - only some of those have the necessary capabilities. I have seen a 2x250W Rotel Michi power amp unable to drive a pair of Apogee Ribbons. Something an YBA2 HC did easily with only 2x50W! I could go on and on...

It is, indeed, a very complicated world! That's why "Try before you buy" is still the best advice one could give for all things audio. I surely intend to visit you on Oct. 20. But please give the vinyl to Tony, as I would like to give it a listen on his system. Thanks!

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Yes - you got me with low impedance speakers, or rather with speakers with vicious impedance curves that can throw any calculation into the dust.

However, from what I remember the original poster has Klipsch speakers which, if anything, suffer the opposite effect in that in parts of the spectrum the impedance goes well above rather than below the nominal 8 ohms specified.

I seem to remember reading that my own Heresies reach levels of 30 ohms in parts which is why - despite the high sensitivity - they are still a bugger to drive.

On the reverse side I will raise your Apogees a pair of Final 0.3's. Frankly I dont know how low these really go but it has to be the wrong side of an ohm. Ask Tony - his Accuphase just died whilst trying to drive them (170 wpc into 8 ohms) whilst a 50 wpc Electrocompaniet played them fine (if not particularly beautifully). For beautiful the only amp we have seen drive them is the AudioNet Monoblocks with the same companies SS pre-amp that was at the last high end show here.

Those Finals are probably the worst speakers I have ever seen for their demands on the amp. The sad thing is that properly done they create a simply exquisite sound.

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Where did I come up with my "1 tube watt is roughly the equivilent of 2 to 3 solid state watts" statement.

I've heard that a few times before.

I'm very new to tubes.

My experience with tubes is totally centered around the push-pull configuration.

The push-pull I have, seems to support that theory when compared to my SS.

My 40 watt tube amp pushes my Quartets to almost as high of levels as my 140 watt Solid State.

They almost match Db outputs at the equal volume knob positions.

I guess I bought into that theory before getting all the facts.

But, it seems to make sense.

Oh, BTW, I just recently read that peticular "rule of thumb" on the Jolida website in the Tube Audio - FAQ section1.gif

Tubes are cool.3.gif

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The only thing that could support the theory of the "stronger" tube watt, is that tubes have much smoother clipping characteristics than transistors. That said, you can overdrive (whithin reason!) a tube amp, without great sonic penalty...

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When SS state amps go beyond their rated power, they immediately go into pure distortion. The "clipping" is extremely dirty and unforgiving.

When a tube amp goes beyond it's rated power, the clipping is very subtle, and usually not even noticable. It takes some serious cranking on the volume control before it's audible.

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You said it yourself:"Properly done...". Now, this - apparently simple -"Properly done..." is not simple at all! 1)Even easy to drive speakers can be very selective as to the rest of the set-up and the room and 2)You can create a technically correct (i.e. balanced...) stereo system and still not like the end result...Why? Because you cannot really communicate with music through it.

To cut a long story short, my humble opinion is that to reach audio nirvana takes time and - unfortunately - there are no ready made recipies that apply. On the contrary, reading or exchanging views on the subject is very helpful in determining one's criteria i.e. what to try and what to avoid.

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Yup 2. I will buy that big time.

Hey - I never said I was providing a means of selectiing anything. Just providiing some generic measures for the meaning of power in terms of dB.

and dont talk to me about testing. You think I set out to have a stereo in every room in the house??

(BTW - anyone know a way to waterproof Heresies for use in a bathroom?? (Just kidding).

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SS makers also use different levels of distortion to create their ratings. For example, my amp is rated at 125w/c. But, they cleanly produce 91w/c, and have a max somewhere in the neihborhood of 145w/c. They could have really picked any number inbetween 90 and 145 for the rating. It just depends on the amount of distortion that a person is willing to accept for the stated rating.

To me, my usable power is 91w/c (.005%THD). The 145 is at 1% THD, and 125 is .1% THD.

Another thought is, given the calculations from previous posters, to get another +3db above my 91w/c my amp would need to go to a clean 182w/c. Way past even the 145 mark.

So, how much more sound pressure is crated by pushing it to 100, 125, or 145? Not enough to notice, and it would do more harm than good.

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