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Power requirements
Power requirements
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Old 1st August 2012, 05:35 PM   #11
Mooly is offline Mooly  United Kingdom
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Power requirements
Quote:
Originally Posted by Vaughan View Post
Please elaborate more on this.
It's because damping factor in the real world has to take into account the whole "network" hung on the speaker terminals and not just the actual speaker drive unit. It has to include the crossover network etc. So although the damping factor of the amplifier itself may be "impressive" at the terminals on the PCB of the power amp, by the time the signal has passed through an output inductor, relay contacts, speaker leads, a fuse ?? then the damping factor is greatly reduced anyway.

Remember damping factor is the output impedance of the source (amplifier) divided by the impedance of the load. And the output of the amplifier is really the speaker end of the speaker cable.

So a high or low damping factor in reality makes little difference. Where differences can occur is where a designer deliberately wants to increase the output impedance of an amplifier by adding a small series output resistor. (this is something I favoured with my FET amp and B&W 703'S and I added a 0.22 ohm).

As to craving power and all that... well it sounds just like marketing waffle. I crave the wonderful detailed three dimensional sound stage the B&W's give yet they do that with only a couple of watts and an amplifier with very low damping factor.

I don't do bass management
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Old 1st August 2012, 06:17 PM   #12
Vaughan is offline Vaughan
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So the idea that more power can better control the woofer cones is really just audiophile nonsense.

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I don't do bass management
Blasphemy!
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Old 1st August 2012, 06:49 PM   #13
Mooly is offline Mooly  United Kingdom
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Power requirements
Quote:
Originally Posted by Vaughan View Post
So the idea that more power can better control the woofer cones is really just audiophile nonsense.
I would say so yes. It is just marketing talk in the same way that amplifier classes of operation can be talked up to be something they are not.

Power doesn't "control" or exercise control over the speaker cone in the way I think you mean.

That said, amplifiers of varying circuit topologies certainly do differ in their sound presentation but that's not due to power ratings (or damping factor) being able to control the speaker better.

It's also worth noting that speakers with a genuinely large power handling capacity and high efficiency do have the very real ability to play loud, probably far louder than you would ever want in a typical domestic setting.

I had a similar thread to Panos' here,
http://www.diyaudio.com/forums/solid...listening.html
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Old 1st August 2012, 07:09 PM   #14
Vaughan is offline Vaughan
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Quote:
Originally Posted by Mooly
Power doesn't "control" or exercise control over the speaker cone in the way I think you mean
What other way would I mean?

Quote:
That said, amplifiers of varying circuit topologies certainly do differ in their sound presentation but that's not due to power ratings (or damping factor) being able to control the speaker better.
Unless the amplifier was clipping ... that could subjectively sound different vs one that has ample headroom to spare? Since the topic is veering off slightly (and I am guilty of this), what makes up the sonic signature of an amplifier, excluding power and/or damping. There is a case to be made that all amplifiers sound alike when kept within their operating limits, but I wouldn't know a thing about that.

Quote:
It's also worth noting that speakers with a genuinely large power handling capacity and high efficiency do have the very real ability to play loud, probably far louder than you would ever want in a typical domestic setting.
Well that's the thing. You have big B&W speakers, a spec sheet with a 50-500 watt rating and we don't have any clue how they conducted their power handling tests! Which means their power handling figures are meaningless, really. 500 watts at 1kHz for 0.5 seconds, or 500 watts at 800 Hz for 1 sec, or "insert any example".

I mean if a speaker has a 90 dB sensitivity and you are seated 3 meters away, 100 watts could be more than sufficient to drive you out of the room. Years ago I was always under the impression that by simply adding more power, like doubling the power, would suddenly make your system sound much better.

But then I wonder .. how can anything sound better if I'm not making use of the extra reserves? It's just a load of nonsense. Of course there are plenty of people who would disagree, I'm sure.

Quote:
I had a similar thread to Panos' here,
Thanks! I'll take a look. I do appreciate your input in this thread!

Last edited by Vaughan; 1st August 2012 at 07:11 PM.
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Old 1st August 2012, 07:17 PM   #15
MarcelvdG is offline MarcelvdG  Netherlands
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Quote:
Originally Posted by Mooly View Post
It's because damping factor in the real world has to take into account the whole "network" hung on the speaker terminals and not just the actual speaker drive unit. It has to include the crossover network etc. So although the damping factor of the amplifier itself may be "impressive" at the terminals on the PCB of the power amp, by the time the signal has passed through an output inductor, relay contacts, speaker leads, a fuse ?? then the damping factor is greatly reduced anyway.

Remember damping factor is the output impedance of the source (amplifier) divided by the impedance of the load. And the output of the amplifier is really the speaker end of the speaker cable.
One thing to keep in mind, though, is that all contributions except the amplifier output impedance and loudspeaker cable impedance are under control of the loudspeaker designer. The effect of loudspeaker voice coil resistance is already included in the Thiele and Small parameters that are usually the basis for the box design, and the loudspeaker designer can compensate for the effect of things like crossover inductor DC resistance by calculating with slightly changed QES and QTS values that are corrected for this effect. The loudspeaker designer can not compensate for the amplifier output impedance or the cable resistance if he or she doesn't know what amplifier and cable are going to be used.

That being said, it indeed doesn't matter much whether the amplifier damping factor is 50 or 50000, as long as the output impedance is totally negligible compared to the voice coil resistance.
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Old 1st August 2012, 07:37 PM   #16
Mooly is offline Mooly  United Kingdom
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Power requirements
Different sonic signatures of amplifiers is a term many designers don't like and some I think even deny it even exists.

A couple of examples of differing sonic signatures as I have found them. The first is what has become known as the "blameless" topology that on paper offers remarkable performance. Based on the classic long tailed input pair (LTP) it has been refined and optimised to a remarkable degree. It sounds clean and sharp with an almost etched quality. While it can't be faulted as such it can be described as being uninvolving to listen too. It's the amplifier where a few recordings sound great but many many more don't. Although you want to sit down and listen to the music your mind is wandering and your bored and so go and do something else instead. I have built and bought amplifiers of this topology and I would say they all had this underlying characteristic to some degree.

Then there is the other extreme, circuits of less technical ability in numbers but circuits that produce an amplifier that sounds great pretty much whatever is played. Your compelled to listen, you don't want to switch off.

There's a lot in between those two examples such as amplifiers that use lateral FET's, amplifiers that use valves and so but I find the "blameless" type always seem to produce this uninvolving sound to some degree. That is a personal view though Amplifiers such as the classic JLH69 (a 10 watt 4 transistor design) which use what is termed a "single ended" rather than differential input stage which tends to produce even harmonic distortion as opposed to the more predominantly odd order of the LTP always seem much more musical and relaxing to listen too.

I'd have to look back to Panos' thread where I posted detailed measurements and used an SPL meter but for me more than a few watts is unbearably loud in my room. You would have to put the speakers in a large hall to be able to make use of 100+ watts of power.

There's no right and wrong answer to all this. It comes down to what you want and like to listen too.
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Old 1st August 2012, 07:42 PM   #17
Mooly is offline Mooly  United Kingdom
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Power requirements
Thanks for the clarification Marcel.

I'm afraid speaker design itself and TS modelling isn't one of my strong points.
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Old 1st August 2012, 08:42 PM   #18
Vaughan is offline Vaughan
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Quote:
Originally Posted by Mooly
It's because damping factor in the real world has to take into account the whole "network" hung on the speaker terminals and not just the actual speaker drive unit. It has to include the crossover network etc. So although the damping factor of the amplifier itself may be "impressive" at the terminals on the PCB of the power amp, by the time the signal has passed through an output inductor, relay contacts, speaker leads, a fuse ?? then the damping factor is greatly reduced anyway.
Makes complete sense. But then what of valve amplifiers? You read in the magazines how valve amps produce tubby bass, "loose" sounding bass. It all sounds ridiculous.
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Old 1st August 2012, 09:26 PM   #19
MarcelvdG is offline MarcelvdG  Netherlands
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Some valve amplifiers, especially those without overall feedback, have very low damping factors indeed, meaning that the output impedance is anything but negligible compared to the voice coil resistance. That can indeed give substantial errors in the bass response.

By the way, they used to do it quite differently in historic valve radios. Those often had a pentode output stage with no feedback, resulting in a damping factor smaller than unity. The resulting bump in the low-frequency response was used to compensate for the acoustic roll-off caused by the perforated back of the radio enclosure (and the roll-off of the output transformer). In the end the amplifier output impedance just needs to be close to what the loudspeaker designer expected.
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Old 1st August 2012, 10:03 PM   #20
Vaughan is offline Vaughan
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Thanks the explanation Mark! That goes for everyone who posted, I appreciate your views on this.
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