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buddhadas
27-05-2008, 23:49
I have a question about watts. I often hear/see people posting about how many watts they usually use. How in the world does one figure that out? I have a spl meter but i assumed that was for dbl's not watts.
Any input is greatly appreciated!

Peace,

Jim:confused:

Steve Toy
28-05-2008, 12:06
As you rightly state, sensitivity of speakers measured in dB per Watt per metre is more significant than wattage output of an amplifier, especially as there are a number of different methods of measuring wattage. Power output varies with impedance anyway.

Typically with a decent solid state amp the wattage doubles as the impedance halves which is why they are the amplifier choice for speakers that have an uneven impedance curve through frequency. Valve amps OTOH have to be optimised to work at a given impedance which is why they are only really suitable for speakers that measure flat in terms of impedance across the frequency range; it is not so much low impedance that valve amps struggle with but dips and peaks.

Doubling the output power of an amplifier increases the loudness headroom by only 3dB. Also, wattage tells us nothing about how capable an amp is of dynamic swings so a well designed and optimised 30 wpc valve amp with decent transformers into a fairly linear speaker, even one rated at a nominal 4 ohms, is likely to go louder than a 120 wpc rated solid state amp into the same speaker.

If you want loud get a sensitive speaker. A horn-loaded speaker at 104 dB/W/m is going to need only half a Watt to go to 101 dB - and that's bloody loud!

Mike Reed
28-05-2008, 16:44
Interesting, STEVE,

Especially the bit about the fundemental difference in valved and s/s amplification as regards the speaker impedance curve. Didn't know this, and it strikes me that it would be pretty crucial to KNOW your speakers' measurements BEFORE contemplating the method of amplification; or is that overding the case a bit?

The stuff I learn on this forum!!! Pity about my crappy memory banks, though ! (I blame the sixties!)

Mike
28-05-2008, 16:57
speakers that measure flat in terms of impedance across the frequency range

Eh?.... I'd REALLY like to see one of those matey!!!

:trust:

Steve Toy
28-05-2008, 20:36
Well, flat-ish.

Filterlab
31-05-2008, 12:57
Bud; for a really mathematical explanation of watts, have a gawps on Wikipedia.

Click here for mind bending maths. (http://en.wikipedia.org/wiki/Watt)

sacsongs
31-05-2008, 14:01
I had a local dealer mention current as a more important criteria than watts. Comments?

WikiBoy
31-05-2008, 14:16
I have a question about watts. I often hear/see people posting about how many watts they usually use. How in the world does one figure that out? I have a spl meter but i assumed that was for dbl's not watts.
Any input is greatly appreciated!

Peace,

Jim:confused:

It is just bullshite marketing that you should largely ignore.

Watts means something to a techy, and means how much tricity you use and was developed as means of counting it so you could be charged for it. That is its only purpose as far as you are concerned. But when the marketing men began to take over the audio industry they approached their techys to have some *figures* - parameters to spin their bollocks around. Watts came first then frequency response and it all spiralled from that and created specmanship which got out of control in the early to mid 70's and created the environment that the comedy sketches like the woofer and tweeter one did in making us all look stupid. It even had loudspeaker manufacturers putting watts on their specs - bloody ridiculous. Well over reaction creates opposite reaction which gave birth to the flat earth.

Specs are completely meaningless and can be spinned to mean what ever you want and can be measured in anyway you want unless you pin down the measuring requirements and parameters precisely which they never do.

OK so how do you understand potential loudness if watts are meaningless. Well it is so complex the *ONLY* safe was is to try it and see. It depends on load - how lossy / efficient, how that load interfaces withe the current source, how much voltage / current that source is capable of / can drive into that load, how big is the area you wish to fill with sound at the loudness you wish it and how echoic it is, and finally how deaf you are.

It is in reality much more complex than that as phase relationships and current v voltage drive all come in to it so if you want to understand then probably go take a degree course in electrical engineering. NO! don't want to - then just listen to music and decide if you like the way it is being reproduced, does it make the little hairs rise on the back of your neck?

buddhadas
31-05-2008, 15:50
Thanks for the responses, amazingly, I "get" most of it. My original question must have been to vague.
I simply love the way my system sounds!
I do not need to know most of these things, I was just curious.
So I will just listen to more music, and quit thinking as much.

Thanks

Jim