Music Fidelity - Techy Explanation of their Advert

Tel

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As I received an email regarding MF's original Ad and a follow up, I sent a reply asking them the basis for their claims.

No one was more astonished when I actually got a reply from Emma Cleverden. I don't delude myself that this isin any way a unique personal reply but fair play to MF for at least having something ready for the 'outragedMusic Centre' owners emails!

Technical background to our dynamic range/power claims.

This section is slightly technical and may take you a few minutes to read.

We would like to take you through to the basic technical elements that make

up a hi-fi system and explain how they go together.

Loudspeaker sensitivity

Loudspeaker sensitivity is a measure of how much sound a loudspeaker will

give for 1 watt at 1 metre. It is critical to note that the basic measure

of sensitivity is at 1 metre and not at a typical listening distance of

about 10 feet or 3½ metres.

Sound attenuates (reduces) over distance at the rate of 6dB with each

doubling of the distance. At 2 metres distance from the loudspeaker its

perceived sensitivity is reduced by 6dB. At a normal listening distance of

about 10 or 11 feet from the loudspeaker its perceived sensitivity will be

reduced by approximately 10dB.

This is the factual basis for our claims about how much power a system would

need for a decent hi-fi dynamic range. We reiterate that this is not made

up or marketing hype, it is scientific fact.

Loudspeaker sensitivity – is it real?

Regrettably, most loudspeaker sensitivity ratings are not particularly

accurate and are regularly overstated by 2 or 3dB. We have seen several

examples of respected manufacturers’ products specifications overstating

their sensitivity by 5dB or more.

This does not sound like a big deal, but it has tremendous implications for

the power required by the loudspeaker to deliver proper dynamic range.

Amplifier power – confusion reigns.

This is the source of much misunderstanding. Amplifier power is specified

in watts, which are a measure of heating power. They have no apparent

relationship to what we hear, as they are a linear measure. Loudspeakers

(and our ears) perceive things in dB (decibel) steps. These are based on a

logarithmic relationship.

This is the fundamental mismatch between what your ears perceive and how

amplifiers are specified. The solution to the problem is to recalibrate

watts into dB steps. The results are below, in a chart of watts converted

to dB steps. For convenience we have started our chart at 50 watts. These

figures are not made up they are fact.

dBW Watts dBW Watts

17 50 24 251

18 63 25 316

19 79 26 400

20 100 27 500

21 126 28 630

22 156 29 795

23 200 30 1000

As you can see, as soon as you calibrate amplifier power in dB watts, you

get a dramatically different view of what amplifier power really means.

First off, you can see that what looks a large increase in amplifier power,

for example from 50 watts to 100 watts, only gives an increase of 3dB.

Things get really interesting as when you get to higher powers. You start

need vast amounts of power for each dB step. For example, only 1dB

(remember 1dB is the smallest change in sound pressure level that the human

ear can perceive UNDER IDEAL LISTENING CONDITIONS) is the difference between

400 watts and 500 watts. If you really wanted to hear a difference above

400 watts you’d probably need to go to 800 watts (3dB) which should be

audible.

You can see why amplifier manufacturers want to sweep these figures under

the nearest carpet; they make most of their claims look ridiculous as they

predict that most loudspeaker/amplifier combinations will have only limited

dynamic range.

How much dynamic range do I need?

Some years ago John Atkinson (current editor of the Stereophile) made some

measurements of live music using accurate equipment. He recorded 109dB

peaks (brass and percussion) and the quietest was 63dB (solo violin) a

variation of 46dB from the quietest to the loudest moments – a huge dynamic

range.

The question is what sort of dynamic range a really good hi-fi system should

have.

In our opinion, an ability to produce unclipped peaks of 105dB is the

minimum starting point for a really good hi-fi system. You are welcome to

debate different figures, but that is our basic position.

If you listen to small scale chamber music or usually listen at quiet

levels, you will not need the peak capacity we deem necessary. But if you

are trying to recreate the listening experience at reasonable levels, 105dB

peak is not overly generous.

How do you put all this together.

Assuming that you have accepted the scientific facts this is how you

determine what your system can produce.

1. Take your loudspeaker sensitivity (better yet check back to a technical

review to find out what its sensitivity really is). Deduct around 10dB for

the SPL (sound pressure level) attenuation over distance. And then add back

3dB because there are two loudspeakers in the room.

Now you have arrived at the practical, real world, in-room sensitivity of

your loudspeaker system.

2. Decide what peak level you want to achieve. We think 105dB is about

right. Some people think 110dB is more appropriate. It’s up to you.

3. Deduct the result of 1 above from your decision about 2. This is how

much amplifier power you require in dB watts.

4. Use the chart above to translate your dB watts result in to ordinary

watts.

General overview.

None of this is intended as criticism of amplifier or loudspeaker

manufacturers. You could regard it as a criticism of magazines and shops

for not bringing it to your attention. We have been banging on about this

for about ten years and many people have reacted adversely because they

believed it was just marketing hype. This is not marketing hype, this is

scientific fact. Many people do not like the result of a scientific

analysis of their equipment but that does not alter the scientific facts.

People have objected to our position claiming that their system sounds

great. It might. However, you can’t escape the fact that, if they have a

low powered amplifier and relatively insensitive loudspeakers, the system

must be clipping, distorting and limiting regularly, which must dominate the

listening experience. Maybe the listeners like distortion clipping. Well,

each to his own and good luck to them. If you want your hi-fi system to

produce as close an approximation to the real live performance as you can

get, then you must ensure, for a start, that your amplifier is not clipping.

 

mosfet

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I don’t see anything disagreeable with the reply Tel. It’s not marketing hype, it’s competent engineering. MF have just gone up a number of notches in my opinion and they were not a brand I’d given much consideration to before.

MF are critical of the hi-fi magazines for dumbing-down to appeal to subjectivism. I wouldn’t disagree with this either.

 

Davewhityetagain

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Tel wrote:

As I received an email regarding MF's original Ad and a follow up, I sent a reply asking them the basis for their claims.No one was more astonished when I actually got a reply from Emma Cleverden. I don't delude myself that this isin any way a unique personal reply but fair play to MF for at least having something ready for the 'outragedMusic Centre' owners emails!

Technical background to our dynamic range/power claims.

This section is slightly technical and may take you a few minutes to read.

We would like to take you through to the basic technical elements that make

up a hi-fi system and explain how they go together.

Loudspeaker sensitivity

Loudspeaker sensitivity is a measure of how much sound a loudspeaker will

give for 1 watt at 1 metre. It is critical to note that the basic measure

of sensitivity is at 1 metre and not at a typical listening distance of

about 10 feet or 3½ metres.

Sound attenuates (reduces) over distance at the rate of 6dB with each

doubling of the distance. At 2 metres distance from the loudspeaker its

perceived sensitivity is reduced by 6dB. At a normal listening distance of

about 10 or 11 feet from the loudspeaker its perceived sensitivity will be

reduced by approximately 10dB.

This is the factual basis for our claims about how much power a system would

need for a decent hi-fi dynamic range. We reiterate that this is not made

up or marketing hype, it is scientific fact.

Loudspeaker sensitivity – is it real?

Regrettably, most loudspeaker sensitivity ratings are not particularly

accurate and are regularly overstated by 2 or 3dB. We have seen several

examples of respected manufacturers’ products specifications overstating

their sensitivity by 5dB or more.

This does not sound like a big deal, but it has tremendous implications for

the power required by the loudspeaker to deliver proper dynamic range.

Amplifier power – confusion reigns.

This is the source of much misunderstanding. Amplifier power is specified

in watts, which are a measure of heating power. They have no apparent

relationship to what we hear, as they are a linear measure. Loudspeakers

(and our ears) perceive things in dB (decibel) steps. These are based on a

logarithmic relationship.

This is the fundamental mismatch between what your ears perceive and how

amplifiers are specified. The solution to the problem is to recalibrate

watts into dB steps. The results are below, in a chart of watts converted

to dB steps. For convenience we have started our chart at 50 watts. These

figures are not made up they are fact.

dBW Watts dBW Watts

17 50 24 251

18 63 25 316

19 79 26 400

20 100 27 500

21 126 28 630

22 156 29 795

23 200 30 1000

As you can see, as soon as you calibrate amplifier power in dB watts, you

get a dramatically different view of what amplifier power really means.

First off, you can see that what looks a large increase in amplifier power,

for example from 50 watts to 100 watts, only gives an increase of 3dB.

Things get really interesting as when you get to higher powers. You start

need vast amounts of power for each dB step. For example, only 1dB

(remember 1dB is the smallest change in sound pressure level that the human

ear can perceive UNDER IDEAL LISTENING CONDITIONS) is the difference between

400 watts and 500 watts. If you really wanted to hear a difference above

400 watts you’d probably need to go to 800 watts (3dB) which should be

audible.

You can see why amplifier manufacturers want to sweep these figures under

the nearest carpet; they make most of their claims look ridiculous as they

predict that most loudspeaker/amplifier combinations will have only limited

dynamic range.

How much dynamic range do I need?

Some years ago John Atkinson (current editor of the Stereophile) made some

measurements of live music using accurate equipment. He recorded 109dB

peaks (brass and percussion) and the quietest was 63dB (solo violin) a

variation of 46dB from the quietest to the loudest moments – a huge dynamic

range.

The question is what sort of dynamic range a really good hi-fi system should

have.

In our opinion, an ability to produce unclipped peaks of 105dB is the

minimum starting point for a really good hi-fi system. You are welcome to

debate different figures, but that is our basic position.

If you listen to small scale chamber music or usually listen at quiet

levels, you will not need the peak capacity we deem necessary. But if you

are trying to recreate the listening experience at reasonable levels, 105dB

peak is not overly generous.

How do you put all this together.

Assuming that you have accepted the scientific facts this is how you

determine what your system can produce.

1. Take your loudspeaker sensitivity (better yet check back to a technical

review to find out what its sensitivity really is). Deduct around 10dB for

the SPL (sound pressure level) attenuation over distance. And then add back

3dB because there are two loudspeakers in the room.

Now you have arrived at the practical, real world, in-room sensitivity of

your loudspeaker system.

2. Decide what peak level you want to achieve. We think 105dB is about

right. Some people think 110dB is more appropriate. It’s up to you.

3. Deduct the result of 1 above from your decision about 2. This is how

much amplifier power you require in dB watts.

4. Use the chart above to translate your dB watts result in to ordinary

watts.

General overview.

None of this is intended as criticism of amplifier or loudspeaker

manufacturers. You could regard it as a criticism of magazines and shops

for not bringing it to your attention. We have been banging on about this

for about ten years and many people have reacted adversely because they

believed it was just marketing hype. This is not marketing hype, this is

scientific fact. Many people do not like the result of a scientific

analysis of their equipment but that does not alter the scientific facts.

People have objected to our position claiming that their system sounds

great. It might. However, you can’t escape the fact that, if they have a

low powered amplifier and relatively insensitive loudspeakers, the system

must be clipping, distorting and limiting regularly, which must dominate the

listening experience. Maybe the listeners like distortion clipping. Well,

each to his own and good luck to them. If you want your hi-fi system to

produce as close an approximation to the real live performance as you can

get, then you must ensure, for a start, that your amplifier is not clipping.
have trouble with there 6db claim I go with this lot and 3db claim

LINK

 
M

murray johnson

Guest
I wonder how MF now, with hindsight, regard one of their most successful and highly acclaimed products, the 20W A1.

I didn't think it was as catastrophically bad as their figures might suggest. Indeed I'd go so far as to say it was one of the better (not difficult) amplifiers they've actually made.

I share their concern re the relationship between amplifier power & speaker sensitivity, however in my experience making more powerful amplifiers with more gain stages & more complexity is a crude and ignorant way of addressing the problem (albeit one that appeals to spec minded fools who link the size & power of their hifi with the size of their genitals.) A better approach is to develop and use speakers that convert more than a half or one percent of the power fed to them into sound rather than heat and to drive them with simpler better amplifiers that aren't hamstrung by unnecessary complexity.

 
A

Alex A

Guest
I listen at about 5ft. With 88dB speakers I end up with 86dB 'real world' sensitivity. Which means I need 79W to achieve 105dB. Since I have 200W (4ohms) that makes 109 max dB. And that doesn't account for sound reflections (I think).

I suspect a lot of people fall short of the 10ft listening distance, and can probably achieve fairly close to 105dB unclipped with 89/90dB speakers in medium sized rooms.

 

JANDL100

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murray johnson wrote:

A better approach is to develop and use speakers that convert more than a half or one percent of the power fed to them into sound rather than heat and to drive them with simpler better amplifiers that aren't hamstrung by unnecessary complexity.
I agree in principle. But you can go too far with this approach as well - very high sensitivity (> 100 dB/W say) can make very taxing demands on amplifier S/N ratio. Loudspeaker tonal colourations and bass extension can be a real problem as you go up in efficiency too.

 
A

Alex A

Guest
murray johnson wrote:

I share their concern re the relationship between amplifier power & speaker sensitivity, however in my experience making more powerful amplifiers with more gain stages & more complexity is a crude and ignorant way of addressing the problem (albeit one that appeals to spec minded fools who link the size & power of their hifi with the size of their genitals.) A better approach is to develop and use speakers that convert more than a half or one percent of the power fed to them into sound rather than heat and to drive them with simpler better amplifiers that aren't hamstrung by unnecessary complexity.
I do agree with your analysis Murray. And you're far more of an expert on amplifier construction than I'm likely to every be, but with transistors need circuits necessarily be complex and have multiple gain stages?

To take a topical example, the MF A5 has, I believe, quitea simple circuit with 2 power transistors per channel. Yet it puts out 250WPC. I'm sure some other high power SS amps are similarly simple (well, at least relative to most).

Personally speaking, I'vetended to prefer inefficient speakers given some proper welly to efficient horns etc being driven by <10W. Maybe it's reflective of the music I listen to and the expectations and prejudices I've developed. Would love to hear your kit at some point nontheless.

 

Ant

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murray johnson wrote:

I wonder how MF now, with hindsight, regard one of their most successful and highly acclaimed products, the 20W A1.I didn't think it was as catastrophically bad as their figures might suggest. Indeed I'd go so far as to say it was one of the better (not difficult) amplifiers they've actually made.

I share their concern re the relationship between amplifier power & speaker sensitivity, however in my experience making more powerful amplifiers with more gain stages & more complexity is a crude and ignorant way of addressing the problem (albeit one that appeals to spec minded fools who link the size & power of their hifi with the size of their genitals.) A better approach is to develop and use speakers that convert more than a half or one percent of the power fed to them into sound rather than heat and to drive them with simpler better amplifiers that aren't hamstrung by unnecessary complexity.
however, MF know their target audience have ineficient loudspeakers.
 

Biscuit

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the main issue for me is that I never listen at a level that would necessitate the amp to drive 105-110dB peaks, so I'd rather have something that excels in other (personally more important) aspects of the sound than loudness.

 

julian2002

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yeah unfortunately most of us have neighbors, significant others, kids etc. so banging out music at 105db would get your kit impounded by the council noise abatement squad quick-smart or a melt down by the s/o.

 

mrwippy

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Well if I get a chance this week, I'll get out the SPL meter and see what peaks I get at my normal listening levels and see if I can get 105db.

 
M

murray johnson

Guest
In the late 1950's such serious speakers that existed were generally quite large and quite sensitive. In 1956 Edgar Vilchur (AR) invented a smaller cabinet enclosure (acoustic suspension) which traded sensitivity for bass extension. With the advent of lower cost, higher powered solid state amplification many such smaller 'high quality' speakers that could be driven to satisfactory levels became widely available. The ease with which these designs could be assimilated into the home, made such speakers the norm and the larger, more efficient but old fashioned type of speakers fell out of favour.

Achieving realistic low frequency playback from small drivers in compact enclosures requires significant cone excursion. This in itself brings problems not only in designing magnetic circuits that can provide a nice linear field in which the voice coil can move but also in the need to make drivers robust enough to withstand such large repeated movements and to dissipate the heat generated by applying large amounts of power to them. As a result drivers have become heavier slower and less capable of resolving low level information although they will now go very LOUD!

The pursuit of compactness & domestic/aesthetic compatibility is a different quest to the pursuit of high fidelity (however cleverly it is marketed otherwise)

I would agree with the notion that there were many truly dreadful old high efficiency speakers. Not all though. The original Tannoy GRF's or Vitavox 191 (Klipschorns) can give fantastic results. By incorporating some more modern materials and driver technology some of the newer high efficiency designs are capable of tremendous performance. Avant Garde are a good example of this as are some of the newest JBL high end offerings. Such speakers can give these results with relatively simple low powered amplifiers and can resolve dynamic range & low level detail in a way that no combination of megawatt amplifier & inefficient speaker ever will.

Before complaining how much such speaker systems cost, tot up what you could spend on a full Naim or Linn based system (just as an example). Figures of £50K-£60K are quite easily reached.

imho this isn't the best or wisest way to spend such sums.

EDIT: At the recent Manchester show Mr C had an SPL meter and we tried measuring the levels in the show room. 90 dB+ was plenty loud enough never mind 105 dB!

 

Hawk

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I notice the MF chart doesnt go low enough for someone with 94dB speeks
71_71.gif.90e48c720ca56a2d2fa0532dd3380cc7.gif


Looking at this though based on 1m 1 speaker ill need about 11 Watts
biggrin.png


http://www.noteworthyaudio.co.uk/page21.html

 

Lefty

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remember 1dB is the smallest change in sound pressure level that the human ear can perceive UNDER IDEAL LISTENING CONDITIONS
Where do they get that from? I really hope it isn't something they have just made up - for their sake. I have to say their explanation has made them go down in my estimation. If they are going to make such statements, they have to be backed up. Why did they say "remember" as if this is common knowledge?

They do make some valid points but there is stll too much waffle and pseudo science for me.

Amplifier power is specified in watts, which are a measure of heating power.
Why heating power? A bit strange. Watt is the unit of power full stop. It can be used to measure heating if you like. Did they copy and paste that line from an electric heater manufacturer's website or something? :lmao:

Lefty

 

El Seano

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Lefty wrote:

remember 1dB is the smallest change in sound pressure level that the human ear can perceive UNDER IDEAL LISTENING CONDITIONS
Where do they get that from? I really hope it isn't something they have just made up - for their sake. I have to say their explanation has made them go down in my estimation. If they are going to make such statements, they have to be backed up. Why did they say "remember" as if this is common knowledge?
1dB is regarded as the standard. 3dB is often used outside of ideal listening conditions as the just noticable difference. However this does vary from person to person and depends on the conditions present.

 

Cable Monkey

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Lefty wrote:

Amplifier power is specified in watts, which are a measure of heating power.
Why heating power? A bit strange. Watt is the unit of power full stop. It can be used to measure heating if you like. Did they copy and paste that line from an electric heater manufacturer's website or something? :lmao:

Lefty
The actual definition of a watt is the amount of heat energy dissipated by a 100% efficient resistance when a current of 1 amp is drawn across a potential difference of 1 volt (sorry, laymans interpretation) so the most basic manifestation of energy is heat. A heater element is one of the best ways of demonstrating this, so the answer to your question is quite possibly yes!

 

Lefty

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El Seano wrote:

1dB is regarded as the standard. 3dB is often used outside of ideal listening conditions as the just noticable difference. However this does vary from person to person and depends on the conditions present.
Really? I'm genuinely intrigued by this (not trying to be difficult) can you show me where this comes from?

Lefty

 

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