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Sam

...tube amps and speakers arent rocket science...

Rockets are quite simple...even hi-fi rockets. They don't need much
bandwidth. As a control problem, a rocket lies somewhere between a
valve amp and a washing machine, I would say.

cheers, Ian

On 13 Nov 2004 22:13:12 -0000, Anonymous
wrote:


A good rule of thumb is that a symphony orchestra playing full fortissimo in an
acoustically sound hall will reach a punter in a good seat (say about four to six
rows back, directly or nearly directly behind the conductor) at 90dB. In a theater
with drapes on the walls and other soft furnishings, the sound pressure will be less.
The purpose of high fidelity is the nearest approach to the concert hall. We can
thus say that a lover of orchestral music who wants to reproduce the concert
hall experience requires 90dB acoustic level at his ears, regardless of where
he sits. That 90db will then take care of any possible peak in the sound for
most of the time the acoustic level will be much lower.

The above is incorrect. Typical measured values in realconcert halls
commonly approach 105-108dB with a full syphony orchestra playing a
crescendo. That puts all your subsequent calculations out by a factor
of about twenty. I can understand why you wish to use 100dB/w/m
speakers (Lowthers) for this exercise, but the above is simply
misleading to those with speakers of normal 85-90dB/w/m sensitivity,
which require several hundred watts to achieve true fortissimo levels.
A good rule of thumb for a high-quality system is an ability to reach
110dB peaks, while a favoured few can reach 120dB, leaving plenty of
'breathing room' for the majority of music - and ensuring much greater
linearity below 110dB.

So how many watts should my projected amp produce to drive the ESL63
when they arrive? Well, the Quad literature supplies the interesting information
that the speakers are not intended to run at more than 10Vrms continuous,
that distortion sets in at 40Vrms, and that the maximum permitted peak is
50Vrms. But we know that Quads own tranny amps have output limiters
at 20V when they are used with the ESL63!

Incorrect, the limiting is at 40 volts and 5 amps, hence the 405
designation of that tranny amp, like the 303 before it. The 606 was
not intended for use with Quad ESLs.

The literature also claims the ESL63s sensitivity as 86dB for
2.83V but reliable friends have measured it in my room as
85dB, so we shall work with that.

That seems about right, but in practice you get another 3dB or so, due
to the farfield effect of the backwave.

Here we go: 1W gives 85dB at one meter, double to 2W for 88dB,
double again to 4W for 91dB, which is more than enough for the
loudest music I play. So we have 4W at one meter but I sit 5ft away,
say 1.5 meters. Lets call it 2 meters and allow the rest for an
additional margin, so 4Wx4 is 16W for two speakers, or 8W per
speaker. Allow one quarter reduction for the room effects, so
the barest minimum is 6W per side. But lets not be mean with our
margins. Lets double that, or treble it, as the theory demands.
So now we have 12W to 18W, including generous margins. Remember
too that this theoretical approach always overestimates the power required.

Nope, your approach understimates the power required, because your
original acoustic figure for a full orchestra was about 15dB too low.
This is of course exactly why the Quad ESL63 has a reputation for
being unable to play realistic orchestral peaks levels, even when
driven by the 100 watts per channel of the 405.

So what can we conclude? Surprise, surprise. You dont need
horns to enjoy single ended tubes to their fullest, indeed to painful
volume levels! And, unless you choose your speakers while operating
on auto-pilot, or drive them at psychopathologically anti-social levels,
around 8 or 9 watts will do all the business you will ever require.

Sorry, this is just totally untrue, unless you are indeed using
extremely sensitive speakers such as Lowthers or Avantgardes. If *you*
prefer to play music quietly, that's just fine, and I'm sure this
thread will produce some fascinating topics for discussion, but please
don't pretend that less than 10 watts is all that is required to
produce realistic full orchestra fortissimos with conventional
speakers, let alone less sensitive designs such as the Quads.
--

Stewart Pinkerton | Music is Art - Audio is Engineering

Stewart Pinkerton wrote:

On 13 Nov 2004 22:13:12 -0000, Anonymous
wrote:

A good rule of thumb is that a symphony orchestra playing full fortissimo in an
acoustically sound hall will reach a punter in a good seat (say about four to six
rows back, directly or nearly directly behind the conductor) at 90dB. In a theater
with drapes on the walls and other soft furnishings, the sound pressure will be less.
The purpose of high fidelity is the nearest approach to the concert hall. We can
thus say that a lover of orchestral music who wants to reproduce the concert
hall experience requires 90dB acoustic level at his ears, regardless of where
he sits. That 90db will then take care of any possible peak in the sound for
most of the time the acoustic level will be much lower.

The above is incorrect. Typical measured values in realconcert halls
commonly approach 105-108dB with a full syphony orchestra playing a
crescendo. That puts all your subsequent calculations out by a factor
of about twenty. I can understand why you wish to use 100dB/w/m
speakers (Lowthers) for this exercise, but the above is simply
misleading to those with speakers of normal 85-90dB/w/m sensitivity,
which require several hundred watts to achieve true fortissimo levels.
A good rule of thumb for a high-quality system is an ability to reach
110dB peaks, while a favoured few can reach 120dB, leaving plenty of
'breathing room' for the majority of music - and ensuring much greater
linearity below 110dB.

So how many watts should my projected amp produce to drive the ESL63
when they arrive? Well, the Quad literature supplies the interesting information
that the speakers are not intended to run at more than 10Vrms continuous,
that distortion sets in at 40Vrms, and that the maximum permitted peak is
50Vrms. But we know that Quads own tranny amps have output limiters
at 20V when they are used with the ESL63!

Incorrect, the limiting is at 40 volts and 5 amps, hence the 405
designation of that tranny amp, like the 303 before it. The 606 was
not intended for use with Quad ESLs.

The literature also claims the ESL63s sensitivity as 86dB for
2.83V but reliable friends have measured it in my room as
85dB, so we shall work with that.

That seems about right, but in practice you get another 3dB or so, due
to the farfield effect of the backwave.

Here we go: 1W gives 85dB at one meter, double to 2W for 88dB,
double again to 4W for 91dB, which is more than enough for the
loudest music I play. So we have 4W at one meter but I sit 5ft away,
say 1.5 meters. Lets call it 2 meters and allow the rest for an
additional margin, so 4Wx4 is 16W for two speakers, or 8W per
speaker. Allow one quarter reduction for the room effects, so
the barest minimum is 6W per side. But lets not be mean with our
margins. Lets double that, or treble it, as the theory demands.
So now we have 12W to 18W, including generous margins. Remember
too that this theoretical approach always overestimates the power required.

Nope, your approach understimates the power required, because your
original acoustic figure for a full orchestra was about 15dB too low.
This is of course exactly why the Quad ESL63 has a reputation for
being unable to play realistic orchestral peaks levels, even when
driven by the 100 watts per channel of the 405.

So what can we conclude? Surprise, surprise. You dont need
horns to enjoy single ended tubes to their fullest, indeed to painful
volume levels! And, unless you choose your speakers while operating
on auto-pilot, or drive them at psychopathologically anti-social levels,
around 8 or 9 watts will do all the business you will ever require.

Sorry, this is just totally untrue, unless you are indeed using
extremely sensitive speakers such as Lowthers or Avantgardes. If *you*
prefer to play music quietly, that's just fine, and I'm sure this
thread will produce some fascinating topics for discussion, but please
don't pretend that less than 10 watts is all that is required to
produce realistic full orchestra fortissimos with conventional
speakers, let alone less sensitive designs such as the Quads.

I have been to several concerts at the ANU School of Music
and to the Llewellen Hall which seats about 1,200.
The Canberra Symphany Orchestra is about 40 members strong,
and I enjoy sitting about 30 feet away, just to enjoy the panash of being
fairly close.
I don't like being seated away in the "gods" seats way up the back.

During crescendos the level does not appear to be as loud as when
a pair of 25 watt amps can push my 90 dB speakers when I am 3 metres away.

Maybe if there were 120 musicians all busy, then their audio power would be 3 times
greater than
CSO, so levels could be up to about 9 dB higher, and I might feel pain instead of
rapture when I am up close.

But if I was an oboe player sitting in the middle of the other players,
I think the SPL would for me be quite intolerable, and musicians
do have troubles with the long term exposure to loud music.
I recall someone saying any orchestra couldn't produce more than 110 dB SPL
anywhere, including right in its centre.

Has anyone taken a meter to a concert?

What does some other authority say?


However, I am wary of just using a vrms volt meter to read the amplifier level voltage,
because the
peaks in the music are way higher than the average levels indicated by
a flickering meter needle.

So I suggest the use of a peak reading meter, to allow the recording of the highest
voltage peaks within a recording, and if there is no clipping, and its under the
maximum amplifier voltage output and sufficiently realistic levels are percieved,
then the amp has enough power.

I don't want to hear music played or songs sung any louder than they are
when I go to a concert, although I am sorely tempted to
turn up the wick where somebody plays a harsicord which
in actaul fact is rather quiet.

I have been to the Albert Hall here where the Aria operatic contests have been held, and I
have
heard singers entertain 800 souls easily, and I don't like it any louder.
I wouldn't be seen dead at a Pearl Jam concert able to be heard miles away.

I couldn't stand being next to a grand piano in full flight.
I suspect up close it gives more than 90 dB.

90 dB is too loud for me and 95% of all the folks I know.

I recall the average maximum levels folks like is 88 dB for men, and 84 dB for the ladies,

and there is a lot of info in RDH4 on the topic.

In 1960, many speakers were 95 dB/w/m, and most folks got by with
triode PP Williamson amps with 16 watts, or a couple of 6L6/807
in UL for 25 watts, or more typically 2 x EL84 which gave 12 watts.
10 watts would give 105 dB to each speaker, so total
would be 108dB for 2.
With average loud levels being 85 dB from each speaker only
0.1 watts is needed per channel.

The same amps would be not quite right with modern speakers all mostly
averaging 89 dB/w/m since they need 4 times the power to produce the same SPL
as their 1960 95 dB forerunners.
Still only 0.4 watts is needed for the 85 dB levels.
I like 50 watt amps, but 25 still do it for me, since the levels I like
are not all that high.
I had a rock musician client who was very dissapointed with a pair of 40 watt tube amps I
fixed
even when tested with 93 dB/w/m speakers I had at the time.
I had fingers in my ears, and he says "they didn't go very loud...."

He wanted head banger levels, and he needed at least 100+ watts.
With all due respect, the nature of the music he listened to and made
when he was working in the band did not warrant the use of a fine tube amp,
and any old transistor amp would have done ok.

I know plenty of ppl who are happy with their 8 watt 300B SET amps.

So Stewart, perhaps consider that not all members of the public would
have equal preferences for the volume control knob setting, and in fact
there have been many a murder committed over control knob settings,
and where people live close by each other in large numbers, noise complaints
over music levels are a menace.
Most old folks homes don't allow speakers in the rooms; you must only
use headphones.


Patrick Turner.

On Mon, 15 Nov 2004 00:42:45 +1100, Patrick Turner
wrote:

Stewart Pinkerton wrote:

If *you*
prefer to play music quietly, that's just fine, and I'm sure this
thread will produce some fascinating topics for discussion, but please
don't pretend that less than 10 watts is all that is required to
produce realistic full orchestra fortissimos with conventional
speakers, let alone less sensitive designs such as the Quads.

big snip

I know plenty of ppl who are happy with their 8 watt 300B SET amps.

So Stewart, perhaps consider that not all members of the public would
have equal preferences for the volume control knob setting, and in fact
there have been many a murder committed over control knob settings,
and where people live close by each other in large numbers, noise complaints
over music levels are a menace.
Most old folks homes don't allow speakers in the rooms; you must only
use headphones.

Which part of my statement above has any relevance to your reply? I
wasn't talking about personal preference or social convenience, I was
talking about recreating a realistic SPL, and Andre's incorrect
assumptions in this regard. As it happens, I live in a detached house
of very solid construction, with no other dwelling within twenty
yards, so neighbour nuisance isn't an issue for me - but high fidelity
music reproduction is!
--

Stewart Pinkerton | Music is Art - Audio is Engineering