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All Ears
August 21st 03, 05:49 PM
"Stewart Pinkerton" > wrote in message
...
> On 20 Aug 2003 18:39:11 GMT, "All Ears" > wrote:
>
> >I had the chance to evaluate some solid state current amplifiers
> >(observations only). I had quite high expectations towards these
> >amplifiers. However, they could only match part of my expectations.
>
> Shame that it's not actually a current amplifier, just a poor voltage
> source.
>
> >The interesting part is that the bass area worked extremely well, best I
> >have heard from any amplifier so far. Very musical and detailed, unlike
any
> >other SS design I have heard.
>
> Please define 'worked extremely well'.

Apears to be very well balanced, musical and detailed. To me it seems
"natural"
>
> >Unfortunately the tonal balance and general dynamics was not too good, I
do
> >however doubt that it is the basic concept of current amplification, that
is
> >to blame.
>
> You are right to doubt that, since what you have is *not* a current
> source.

Okay, maybe is is better to call it a modified voltage source.
>
> >I spoke to a couple of speaker designers, and they both confirmed that
> >"speakers are current based devices" and they also said that the basic
idea
> >of current amplification is good, providing it is implemented the right
way.
>
> I suspect that this is not what they actually said, assuming that they
> have some competence in the field, since a current source would be
> about the worst possible way to drive most speakers.
>
> >The reason for my high expectations was, that my beloved OTL tube
amplifiers
> >works like current amplifiers (however not entirely linear)
>
> No, they most certainly do not, they are simply voltage sources with
> an output impedance of several ohms. A good current source would have
> an output impedance of many thousands of ohms.

Trying to figure out what the so called "tension gain" really does. They
must be trying to compensate for the variating impedance of the speakers?
>
> > and these has an
> >excellent tonality and the way they handle the bass area, feels just
right.
> >Actually, the way the OTLs handles the bass area, is quite similar to the
SS
> >current amplifiers, the OTLs are just not quite as detailed in the lowest
> >end.
>
> In other words, the OTL is simply a poor substitute for a SS amp....

Well, you can call it what you like, to me it is close to the ultimate
listening experience.

KE
> --
>
> Stewart Pinkerton | Music is Art - Audio is Engineering

Richard D Pierce
August 21st 03, 11:11 PM
All Ears wrote:
> I have only tested with self damping speakers.

This one statement alone would indicate, again with no
disrespect intended, that you have no idea what the term
"damping" means nor, in fact, are you aware of the fact that a
"self-damping loudspeaker" is a completely nonsense, emtpy and
meaningless term.

Damping is a VERY well understood term that has a VERY precise
definition: it is, indeed, the ration between the amount of
energy dissipated in a resonant system to the energy staored in
that resonant system. Any other definition is, frankly bogus,
and is most often the result of complete misunderstanding of
resonant systems.

Be that as it may, there, predominatly, three damping mechanisms
in a loudspeaker, in the sense that there are three means by
which energy is removed from the system, i.e., damped:

1. Electrical losses
2. mechanical losses (friction)
3. acoustical losses (the real part of the speaker's radiation
impedance.

The electrical damping occurs because current flowing through
the voice coil encounters elertrical resistance, is turned into
heat, and is thus lost from the system. SImilarily the
mechanical losses result from motion in the suspension being
converted to heat via friction and thus energy is removed from
the system. Abd, lastly (and quite insignificantly) a small
amount of energy is dissipated in the form of sound, and also,
thus, removed from the system.

The two largest damping mechanisms are, in order of importance,
electrical and mechanical. In high quality drivers, the
mechanical damping is typically on the roder of 1/4 to 1/10 that
of the electrical damping.

If you claim is that a speaker is "self damping" in the sense
that it does not require the electrcial portion of the total
damping, that directly requires that the same mechanism that
performsn the electrical damping, the motion of a conductor
through a magnetic field, must be very small, and thus the same
mechanism that generated the motion to begin with: the flow of
current through a conductor in a magnetic fidl, must ALSO be
appropriate insignificant.

If your claim is that the speaker does not depend upon
electrical damping, then you MUST ALSO BE CLAIM THE SPEAKER
CANNOT WORK AT ALL: because having no electrical damping means
that it cannot have any electrical coupling.

Thus, your term, "self-damped" is probably ill-formed and quite
incorrect.

In fact, I would submit that, in fact, you preference for this
amplifier is directly because of the large frequency reposne
pertuerbations caused by its high output impedance, which are
most likely to be the most severe in the low bass, where the
impedance swings of the speaker are their greatest.


--
| Dick Pierce |
| Professional Audio Development |
| 1-781/826-4953 Voice and FAX |
| |

All Ears
August 21st 03, 11:12 PM
"Stewart Pinkerton" > wrote in message
...
> On 21 Aug 2003 14:56:40 GMT, "All Ears" > wrote:
>
> >I'll post the description and specs for the SS "current" amplifiers here
> >also:
> >
> >"With Power Loop, the output power to the loudspeakers is constant,
whatever
> >the frequency, impedance or sensitivity. Tension and current into the
> >loudspeakers are adapted and optimised with a feedback loop monitoring
the
> >overall energy requirement.
> >
> >Product X excels with coherence and optimal transient response throughout
> >the whole frequency spectrum, and adapts to every speaker configuration
and
> >load."
>
> That is pretty much the most meaningless garbage I have ever seen used
> to describe an amplifier. BTW, even if it were possible, you wouldn't
> *want* the power input to the speakers to be constant, since they are
> designed to operate with constant *voltage* into a (sometimes wildly!)
> varying load impedance.
>
>
> >Output power 150 W rms
> > Input sensitivity 1.0 V rms for 150 W into 8 Ohms
> > 0.9 V rms for 150 W into 4 Ohms
> > Voltage gain 39.7 V (32.0 dB) into 16 Ohms
> > 34.4 V (30.7 dB) into 8 Ohms
> > 27.1 V (28.7 dB) into 4 Ohms
> > 17.2 V (24.7 dB) into 2 Ohms
> > Output signal : 1 W into 8 Ohms (0 dBr)
>
> The above measure of 'voltage gain' should in fact be labelled 'output
> voltage', and it simply indicates a coinventional amplifier with poor
> power supply regulation and/or an output impedance of a couple of
> ohms. Typical for something like an OTL tube amp, and a poor
> substitute for a *proper* amplifier.
>
> If the above is from published details of the amplifier in question,
> then it's just further evidence of their incompetence.

It sure is. Maybe it is no wonder I have problems in getting it to sound
good (or even acceptable)

If it would only sound half as good as my OTLs, I could possibly live with
it :)

KE

> --
>
> Stewart Pinkerton | Music is Art - Audio is Engineering

All Ears
August 22nd 03, 12:36 AM
"Richard D Pierce" > wrote in message
...
> All Ears wrote:
> > I have only tested with self damping speakers.
>
> This one statement alone would indicate, again with no
> disrespect intended, that you have no idea what the term
> "damping" means nor, in fact, are you aware of the fact that a
> "self-damping loudspeaker" is a completely nonsense, emtpy and
> meaningless term.
>
> Damping is a VERY well understood term that has a VERY precise
> definition: it is, indeed, the ration between the amount of
> energy dissipated in a resonant system to the energy staored in
> that resonant system. Any other definition is, frankly bogus,
> and is most often the result of complete misunderstanding of
> resonant systems.
>
> Be that as it may, there, predominatly, three damping mechanisms
> in a loudspeaker, in the sense that there are three means by
> which energy is removed from the system, i.e., damped:
>
> 1. Electrical losses
> 2. mechanical losses (friction)
> 3. acoustical losses (the real part of the speaker's radiation
> impedance.
>
> The electrical damping occurs because current flowing through
> the voice coil encounters elertrical resistance, is turned into
> heat, and is thus lost from the system. SImilarily the
> mechanical losses result from motion in the suspension being
> converted to heat via friction and thus energy is removed from
> the system. Abd, lastly (and quite insignificantly) a small
> amount of energy is dissipated in the form of sound, and also,
> thus, removed from the system.
>
> The two largest damping mechanisms are, in order of importance,
> electrical and mechanical. In high quality drivers, the
> mechanical damping is typically on the roder of 1/4 to 1/10 that
> of the electrical damping.
>
> If you claim is that a speaker is "self damping" in the sense
> that it does not require the electrcial portion of the total
> damping, that directly requires that the same mechanism that
> performsn the electrical damping, the motion of a conductor
> through a magnetic field, must be very small, and thus the same
> mechanism that generated the motion to begin with: the flow of
> current through a conductor in a magnetic fidl, must ALSO be
> appropriate insignificant.
>
> If your claim is that the speaker does not depend upon
> electrical damping, then you MUST ALSO BE CLAIM THE SPEAKER
> CANNOT WORK AT ALL: because having no electrical damping means
> that it cannot have any electrical coupling.
>
> Thus, your term, "self-damped" is probably ill-formed and quite
> incorrect.

Nevertheless, I have been told that these speakers does not really depend
signifcantly on being damped by the amplifier, which also seems to be true
from my experiences.
Adjusting the feedback does a difference, of course. A matter of preferences
which sounds the best, there do however seems to be a general agreement
among those who has listened to the system what sounds best, and it is not
when the speakers are maximum damped....

KE

>
> In fact, I would submit that, in fact, you preference for this
> amplifier is directly because of the large frequency reposne
> pertuerbations caused by its high output impedance, which are
> most likely to be the most severe in the low bass, where the
> impedance swings of the speaker are their greatest.
>
>
> --
> | Dick Pierce |
> | Professional Audio Development |
> | 1-781/826-4953 Voice and FAX |
> | |

Richard D Pierce
August 22nd 03, 03:17 AM
In article >,
All Ears > wrote:
>"Richard D Pierce" > wrote in message
...
>> If your claim is that the speaker does not depend upon
>> electrical damping, then you MUST ALSO BE CLAIM THE SPEAKER
>> CANNOT WORK AT ALL: because having no electrical damping means
>> that it cannot have any electrical coupling.
>>
>> Thus, your term, "self-damped" is probably ill-formed and quite
>> incorrect.
>
>Nevertheless, I have been told that these speakers does not really depend
>signifcantly on being damped by the amplifier, which also seems to be true
>from my experiences.

Then you either do not understand what was being said or the
person who told you this does not understand what's going on.
And I would not find it the least bit surprising if the person
who got it wrong is the person who made the speaker: the amount
of fundamental misunderstanding of the fundamental physics of
oudspeakers in the high-end community is staggering and
appalling.

>Adjusting the feedback does a difference, of course. A matter of preferences
>which sounds the best, there do however seems to be a general agreement
>among those who has listened to the system what sounds best, and it is not
>when the speakers are maximum damped....

And, again, I see no evidence to contradict the suggestion that
what you really like is a rise in the frequency response at low
frequencies that corresponds with an underdamped, equalized
bass. Because, in physical reality, that is what you have, no
matter what you want to call it.

--
| Dick Pierce |
| Professional Audio Development |
| 1-781/826-4953 Voice and FAX |
| |

chung
August 22nd 03, 05:29 AM
All Ears wrote:
> "Stewart Pinkerton" > wrote in message
> ...
>> On 20 Aug 2003 18:39:11 GMT, "All Ears" > wrote:
>>
>> >I had the chance to evaluate some solid state current amplifiers
>> >(observations only). I had quite high expectations towards these
>> >amplifiers. However, they could only match part of my expectations.
>>
>> Shame that it's not actually a current amplifier, just a poor voltage
>> source.
>>
>> >The interesting part is that the bass area worked extremely well, best I
>> >have heard from any amplifier so far. Very musical and detailed, unlike
> any
>> >other SS design I have heard.
>>
>> Please define 'worked extremely well'.
>
> Apears to be very well balanced, musical and detailed. To me it seems
> "natural"

It would appear that you favor listening to your speakers with a 3 ohm
resistor in series with the speaker cable. That, for whatever reason,
sounds the most natural to you.

>>
>> >Unfortunately the tonal balance and general dynamics was not too good, I
> do
>> >however doubt that it is the basic concept of current amplification, that
> is
>> >to blame.
>>
>> You are right to doubt that, since what you have is *not* a current
>> source.
>
> Okay, maybe is is better to call it a modified voltage source.

It is simply a voltage amplifier with a 3 ohm output impedance. The 3
ohm is either (a) intentionally there to simulate an OTL's output
impedance, (b) intentionally there to create a different sound, or (c)
there due to sheer incompetence.

Anyone who tells you it is a current amplifier is either
(a)intentionally obfuscating, or (b) simply clueless.

>>
>> (snip)
>
> Trying to figure out what the so called "tension gain" really does. They
> must be trying to compensate for the variating impedance of the speakers?

What makes you think that "tension gain" in their marketing "literature"
has to mean anything? It is most likely a term used because it sounds
good to the potential high-end customers. Trust me, there is no term
like that in electrical engineering as applied to audio amplifier design.

You don't compensate for "variating" impedance of speakers. The sensible
amplifier designer designs a voltage amplifier as close to ideal as
possible. The sensible speaker designer designs speakers to be driven by
voltage sources (used with normal, like 12-gauge, cables).

>>
>> > and these has an
>> >excellent tonality and the way they handle the bass area, feels just
> right.
>> >Actually, the way the OTLs handles the bass area, is quite similar to the
> SS
>> >current amplifiers, the OTLs are just not quite as detailed in the lowest
>> >end.
>>
>> In other words, the OTL is simply a poor substitute for a SS amp....
>
> Well, you can call it what you like, to me it is close to the ultimate
> listening experience.

There is no accounting for personal preferences. You can save a lot of
money, though, by using 3 ohms resistors in series with simple,
competent, solid-state amps. Unless you love the glow of the tubes, and
the waiting for the tubes to warm up, or the maintenance...

chung
August 22nd 03, 05:02 PM
All Ears wrote:
>
>
> Meaning? There is no such thing as a self damping speaker?

Please explain to us what you mean by "self-damping"?

Stewart Pinkerton
August 22nd 03, 05:09 PM
On Fri, 22 Aug 2003 04:29:24 GMT, "All Ears" >
wrote:

>In terms of tonal balance and dynamics, the OTLs are pretty superior to
>anything else I have tested. The SS "current" amps does not even come close.

Now *that* is an absolute statement, and furthermore, it is utterly
wrong. Any good SS amp is fundamentally superior to an OTL tube amp
both in flatness of frequency response (aka 'tonal balance') and in
dynamics, since it will have more power, lower noise and a much lower
output impedance than the OTL amp (and almost certainly wider
bandwidth also).
--

Stewart Pinkerton | Music is Art - Audio is Engineering

All Ears
August 22nd 03, 06:36 PM
I just want to thank you all for the feedback regarding this amplifier. It
is always interesting to me, to evaluate new ideas. It seems quite clear to
me now, that there are loads of practical problems in a design like this,
and that it may be sort of a dead end to try to make this work in a real
world.

What initially appealed to me, was the thought of a better way to compensate
for the impedance variations in a dynamic speaker, by using real time DSP
technology in the feedback loop.

With your help, and especially a nice guy in RATs, I now have a lot of
qualified questions to ask the manufacturer of this amp.

KE

Richard D Pierce
August 22nd 03, 09:17 PM
In article >,
All Ears > wrote:
>I just want to thank you all for the feedback regarding this amplifier. It
>is always interesting to me, to evaluate new ideas. It seems quite clear to
>me now, that there are loads of practical problems in a design like this,
>and that it may be sort of a dead end to try to make this work in a real
>world.
>
>What initially appealed to me, was the thought of a better way to compensate
>for the impedance variations in a dynamic speaker,

Okay, here's a question to ask: why does someone think it's
necessary to compensate for the impedance variations in a
dynamic speaker. Since there need be and seldom is any
connection between the frequency-dependent electrical impedance
and the frequency-dependent acoustical frequency response and
power response of the speaker when driven from a proper voltage
source, why nother? There's NOTHING to compensate for.

Look at the question another way: I can take a speaker with the
normal frequency-dependent electrical impedance and add a
passive circuit to the speaker which results in NO
frequency-dependent impedance variations, yet it will not change
the speaker's acoustical performance at all.


>by using real time DSP technology in the feedback loop.

Sorry, it does not seem to do any such thing.

>With your help, and especially a nice guy in RATs, I now have a lot of
>qualified questions to ask the manufacturer of this amp.
--
| Dick Pierce |
| Professional Audio Development |
| 1-781/826-4953 Voice and FAX |
| |

All Ears
August 23rd 03, 08:48 PM
> DEFINE "self-damping speaker" please.
>
I would assume, for the most part, stiff suspension of the woofers.

KE

All Ears
August 23rd 03, 08:49 PM
I rest my case with regards to these amplifiers. I have selected a list of
critical questions to the manufacturer.

Thanks for your assistance in raising these questions.

KE

"Richard D Pierce" > wrote in message
...
> In article <Z_g1b.220122$o%2.102568@sccrnsc02>,
> chung > wrote:
> >All Ears wrote:
> >> Trying to figure out what the so called "tension gain" really does.
They
> >> must be trying to compensate for the variating impedance of the
speakers?
> >
> >What makes you think that "tension gain" in their marketing "literature"
> > has to mean anything? It is most likely a term used because it sounds
> >good to the potential high-end customers. Trust me, there is no term
> >like that in electrical engineering as applied to audio amplifier design.
>
> AS a somewhat obsolete term for "voltage" is "tension,"
> equivalent to a mechanical analog for electromotive potential,
> one could interpret "tension gain" to simply mean "voltage
> gain." In that sense, it would appear to be yet another way of
> throwing tterms around for the purpose of confusion.
>
> >You don't compensate for "variating" impedance of speakers. The sensible
> >amplifier designer designs a voltage amplifier as close to ideal as
> >possible. The sensible speaker designer designs speakers to be driven by
> >voltage sources (used with normal, like 12-gauge, cables).
>
> This whole pile of stinking hooey around "current amplifiers"
> and the "need to compensate for the variating impedance of
> speakers" appears to be just the latest high-end buzzword fad.
> I'm not saying our good friend Mr. Ears is the culprit, indeed,
> he appears to the the happless victim of yet more high-end
> techno-babble. But it is pure nonsense.
>
> --
> | Dick Pierce |
> | Professional Audio Development |
> | 1-781/826-4953 Voice and FAX |
> | |

Richard D Pierce
August 23rd 03, 11:47 PM
In article >,
All Ears > wrote:
>> DEFINE "self-damping speaker" please.
>>
>I would assume, for the most part, stiff suspension of the woofers.

Nope, stiff suspension, in other words, low mechanical
compliance, is not damping. Damping is energy dissipation,
conversion of electrical or mechanical energy into heat so that
it no longer contrinutes to the total stored energy in the
system.

Indeed, all other things being equal, increasing the stiffness
DECREASES the total damping on a loudspeaker system

This can be readily observed by examining what happens to the Q
of the system when the total system compliance is reduced, say,
by reducing the enclosed volume of a system. "Q", a term that is
a specific measure of the ratio of the total amount of energy
storeed to the total amount of energy dissipated, is essentially
the reciprocal of damping: the lower the Q the higher the
damping. When the total system stiffness is increased, the total
Q of the system increases as a direct function.

No, implicit in the claim of a "self damped" loudspeaker is that
ALL the damping must be mechanical, since the inference was made
that changing the amplifier has no effect on system dampinbg.
Once again, if you were to explore how loudspaekers work, the
inveitable conclusion form this is that the electromagnetic
portion of the speaker must have no influence, and that's
absurd: if it has no influence, it cannot make sound when hooked
to an amplifier.

The existance of a totally "self-damped" loudspeaker is simply
not possible.
--
| Dick Pierce |
| Professional Audio Development |
| 1-781/826-4953 Voice and FAX |
| |

All Ears
August 24th 03, 07:38 AM
> No, implicit in the claim of a "self damped" loudspeaker is that
> ALL the damping must be mechanical, since the inference was made
> that changing the amplifier has no effect on system dampinbg.

Changing the feedback/output impedance does change the performance of the
bass, which I also mentioned.

> Once again, if you were to explore how loudspaekers work, the
> inveitable conclusion form this is that the electromagnetic
> portion of the speaker must have no influence, and that's
> absurd: if it has no influence, it cannot make sound when hooked
> to an amplifier.
>
> The existance of a totally "self-damped" loudspeaker is simply
> not possible.

However there are differences in the settling time of the woofers, depending
on the construction of these, and the general construction of the speaker?

KE

> --
> | Dick Pierce |
> | Professional Audio Development |
> | 1-781/826-4953 Voice and FAX |
> | |

Dick Pierce
August 24th 03, 07:24 PM
In article >,
All Ears > wrote:
>> No, implicit in the claim of a "self damped" loudspeaker is that
>> ALL the damping must be mechanical, since the inference was made
>> that changing the amplifier has no effect on system dampinbg.
>
>Changing the feedback/output impedance does change the performance of the
>bass, which I also mentioned.

Then the speakers CANNOT be totally self damped. In fact, what
you are demonstrating is that, just like the VAST majority of
speakers out there, the largest part of the damping is
electrical.. That means, contrary to your wishes, once the
output impedance of the amplifier rises above a certain point,
the speaker is no longer adequately damped.


>> Once again, if you were to explore how loudspaekers work, the
>> inveitable conclusion form this is that the electromagnetic
>> portion of the speaker must have no influence, and that's
>> absurd: if it has no influence, it cannot make sound when hooked
>> to an amplifier.
>>
>> The existance of a totally "self-damped" loudspeaker is simply
>> not possible.
>
>However there are differences in the settling time of the woofers, depending
>on the construction of these, and the general construction of the speaker?

I would really recommend you start going down the path of
educating yourself on how speakers actually work.

In brief, once again, damping specifically refers (except in
cases where the term is grossly misused by those unfamiliar with
the principals, often in the high-end press) to the amount of
energy that is removed from a resonant system, If no energy is
removed from a resonant system, it will resonate forever. These
mechanisms are referred to, properly, as "losses." They LOSE
energy from the system, where it can no longer participate in
keeping the energy-exchanging mechanism that is resonance going.
The greater these losses in proportion to the energy stored, the
greater the damping and the more rapidly the system is brought
to a stop (to a point).

Thus, damping is a measure of the RATE at which the energy is
removed from the system, and is, as has been mentioned several
times already, is proportional to the energy removed by the
system through losses to the energy stored in the system by
reactive, energy storing elements such as mechanical stiffness,
mass, inductance or capacitance, for example.

There are several important loss mechanisms in loudspeakers that
are responsible for damping, listed here in order of decreasing
importance:

1. Electrical resistance in the voice coil, where electrical
energy is turned to heat. Once turned to heat, it can no
participate in the motion of the voice coil. It is, by far,
the LARGEST loss in speakers have ANY pretensions to high
fidelity, usually on the order of 4 to 15 times or more than
all other loss mechanisms combined.

2. Mechanical friction in the suspension elements of the driver
which turn mechanical energy of motion or tension into heat.
Moving the suspension causes internal friction which turns
the energy of motion into heat in precisely the same fashion
that the brakes on your car slow the car and get hot. They
have turned all the motion of the car into a lot of heat, but
theres no way (practical) to turn that heat back into motion.

3. Acoustic absorption losses, This is mechanical friction of
the air molecules passion through fibrous tangles in the
stuffing in the enclosure.

4. Acoustic radiation losses: this is the sound you actually
could hear. Yes, it's a "loss" because unless the speaker
lost SOME energy through sound, you'd never hear it. It
is, in most speakers the tiniest loss of the many, often
comprising a fraction of a percent of the total system
losses and is, not coincidentally at all, precisely the
electroacoustic efficiency of the system.

Yes, all speaker have mechanical and acoustical losses, BUT
ALMOST TOTALLY WITHOUT EXCEPTION THEY ARE INSUFFICIENT TO
PROPERLY DAMP THE SYSTEM. If they were properly damped without
any electrical damping, they could not produce sound at all,
because no electrical damping means no control by the voice
coil, and if the voice coil ain't controlling it, it ain't
moving it. An adverting brochure or a manufacturer's 'white
paper' may claim otherwise: they're wrong.

The electrical losses, as we said, are, by far, the largest. The
single largest factor which determines that electrical damping
is simply the total DC series loop resistance of which the voice
winding is an integral part. The damping is inversely
proportional to the total equivalent DC resistance of the loop.
The larger the resistance, all other things being equal, the
less the electrical damping. It's that simple. Raise that series
resistance enough, and the damping is materially affected.

That is PRECISELY what you high-output-impedance, "current
amplifier" IS DOING, regardless of what the manufacturer or
some high-falutin' magazine writer claims. Strenuous, wishful
thinking or strident claims to the contrary will not change that.

If the additional series resistance is small, on the order of
less that 1/10 the resistance of the voice coil or less, then
the total damping on the system is not materially affected.

More specifically, the total damping D' on the system can be
directly calculated if we know the voice coil resistance Re and
the resistance added by the amplifier Rg and the zero-source-
impedance damping of the speaker D as precisely:

D' = D * Re / (Re+Rg)

which means that is the figures you gave us are correct, and
this misnamed "current amplifier" has an output impedance of
about 3 ohms, and the woofer in your speaker has a voice coil
resistance of 6 ohms, the electrical damping on the system has
been compromised by:

= Re / (Re + Rg)

= 6 / (6 + 3)

= 6/9

or, the system has lost a third of the electrical damping it originally
had connected to a low-source-impedance amplifier.

Unless that speaker was explicitly designed to be driven
from a source impedance of 3 ohms by the designer, IT'S DAMPING
WILL BE SIGNIFICANTLY COMPROMISED AND BE WORSE THAN THE DESIGNER
INTENDED.

Them's the facts.


+---------------------------------------+
| Dick Pierce |
| Professional Audio Development |
| Acoustics and Digital Audio |
| 1-781.826.4953 Voice and FAX |
| |
+---------------------------------------+

All Ears
August 25th 03, 12:17 AM
> Unless that speaker was explicitly designed to be driven
> from a source impedance of 3 ohms by the designer, IT'S DAMPING
> WILL BE SIGNIFICANTLY COMPROMISED AND BE WORSE THAN THE DESIGNER
> INTENDED.

Actually, the speakers are designed towards amplifiers with a high output
impedance. The designer prefers to use the feedback setting that gives a 3
ohm output impedance, personally, I normally prefer the 2 ohm setting. I
believe the the actual description was "critically damped" speakers.

Thanks for an (as usual) competent answer.

KE

>
> Them's the facts.
>
>
> +---------------------------------------+
> | Dick Pierce |
> | Professional Audio Development |
> | Acoustics and Digital Audio |
> | 1-781.826.4953 Voice and FAX |
> | |
> +---------------------------------------+
>
>

Richard D Pierce
August 25th 03, 04:13 PM
All Ears wrote:
>> Unless that speaker was explicitly designed to be driven
>> from a source impedance of 3 ohms by the designer, IT'S DAMPING
>> WILL BE SIGNIFICANTLY COMPROMISED AND BE WORSE THAN THE DESIGNER
>> INTENDED.
>
> Actually, the speakers are designed towards amplifiers with a high output
> impedance.

What speakers are these?

> The designer prefers to use the feedback setting that gives a 3
> ohm output impedance, personally, I normally prefer the 2 ohm setting. I
> believe the the actual description was "critically damped" speakers.

"Critically damped" DOES NOT MEAN SELF-DAMPING!

All has suddenly become VERY clear.

Critically damped means, very simply, that the total Qtc at
resonance is 0.5. That's precisely and exactly what it means. It
DOES NOT MEAN they are "self damped." Critically damped has this
very precise, well understood and agreed upon meaning
(everywhere, it seems, but in the high-end).

A critically damped resonant system, as I said, will have a Qt
at resonance of 0.5. That results in several characteristics: it
has what's called a maximally flat time response, i.e., it has
the shortest settling time in response to a transient, but it
also has a severely drooping response in the bass.

Let's just pretend, for the moment, that the system was designed
to be critically damped with a low source impedance, i.e., less
than 1/10 that of the speaker's DC resistance. This is, by far,
the most reasonable way, since a low source impedance is the
only source that can be reasonably expected to exist.

Let's further pretend the woofer voice coil has a DC resistance
of about 6 ohms.

Hooked to a low source impedance amplifier, the system will have
its Qt or 0.5. But hooked to the 3 ohm output impedance
amplifier, the Qt WILL CHANGE. In fact, the new Qt will be,
approximately:

Qt' ~= Qt (Re + Rg) / Re

or

Qt' ~= 0.5 (6 + 3) / 6

Qt' ~= 0.5 * 9 / 6

Qt' ~= 0.75

This is a REMARKABLE result for one very significant reason:
this speaker, with it's Qt of 0.5, when hooked to a
low-source-impedance amplifier, WILL SOUND LIKE IT HAS NO BASS!

And as soon as you hooked it to this high-source impedance
amplifier: THE SPEAKER WAS NO LONGER CRITICALLY DAMPED AND NO
HAD MORE BASS!.

This is important: assuming the scenario I described above: the
speaker, hooked to this amplifier CANNOT BE CRITICALLY DAMPED.

It has a bass response that is NO different than any other
speaker with the same cutoff frequency and a Qt of 0.75.

I really hope you grasp what's being said here: the assertion
that you have been making now has a technically rational, if not
somewhat absurd, explanation (the absurdity is not your;s, it's
the designers). Basically, as in all cases, the speaker and
amplifier work together to make an integrated system. This
designer, assuming the scenario I described above is correct,
and it is completely plausible, has designed a speaker that can
ONLY work with one amplifier, and an amplifier that can ONLY
work with one speaker, and the two together do not peroform ANY
different that ANY speaker/amplfiier combination that has a Qt
of about 0.75.

If the sceanrio is true, this is simply yet another example of
the absurd, narrow-visioned, uneducated and wrong-headed
nonsense that sets, unfortunately, the high-end audio business
apart from all others.

Do mention, if you will, the name of this amplifier and speaker
so that they may take their rightful place in the audio Rogue's
Gallery, an honor that they have so richly earned for
themselves.

Lety me repeat the important point here in the hopes that you
can understand the implications:

If the designer of this speaker designed it so that it was
critically damped using the common formula for doing so, then
hooked ti to an amplifier whose output impedance is 2-3 ohms. IT
IS NO LONGER CRITICALLY DAMPED.

Please, again, understand that "critically damped" DOES NOT MEAN
"self damped." Critically damped simply means that it has a Qt
of 0.5, a maximally flat time response and a significantly
drooping frequency response in the bass, and most people who
hear critically damped systems consider them to be significantly
bass-shy. But if you hook it to an amplifier with a high output
impedance, it won't be bass-shy anymore AND IT WON'T BE
CRITICALLY DAMPED.

--
| Dick Pierce |
| Professional Audio Development |
| 1-781/826-4953 Voice and FAX |
| |

All Ears
August 25th 03, 05:08 PM
"chung" > wrote in message
news:yXe2b.188731$Oz4.51341@rwcrnsc54...
> All Ears wrote:
> >> Unless that speaker was explicitly designed to be driven
> >> from a source impedance of 3 ohms by the designer, IT'S DAMPING
> >> WILL BE SIGNIFICANTLY COMPROMISED AND BE WORSE THAN THE DESIGNER
> >> INTENDED.
> >
> > Actually, the speakers are designed towards amplifiers with a high
output
> > impedance. The designer prefers to use the feedback setting that gives a
3
> > ohm output impedance, personally, I normally prefer the 2 ohm setting. I
> > believe the the actual description was "critically damped" speakers.
> >
> > Thanks for an (as usual) competent answer.
> >
> > KE
> >
>
> Be very leery when someone says that the speakers are designed for amps
> with high output impedances. The reason is that both the amp's output
> impedance and the speaker's impedance are complex in nature, i.e., they
> are not pure resistances, but that there is a non-zero phase angle
> associated with that impedance that changes with frequency. As a result,
> you cannot get flat power transfer across all frequencies.

This could be the reason that he recommends a Zobel network?
>
> What's wrong with designing speakers to be driven by voltage sources
> (i.e. low output impedance)?

From a technical point of view, probably no major issues. I do however have
a quote from a review of the OTL tube amplifiers, that could be interesting
to get some comments on:

"JB's listening has convinced him that the lower impedance of solid state
designs leads to an excessive damping, which plays havoc with the harmonic
structure of the bottom two octaves of the music. Such damping may, he says,
give the lows more "punch" but at the price of musical truth ("it swallows
the harmonics"). The harmonics collapse (the Telarc bass syndrome of the
Eighties?). and the bass, while powerful, becomes an undifferentiated mass.
To some extend you can hear the harmonics go to pot if you (using a speaker
like the Maggies or the Pipedreams) turn the feedback control on the amps to
their maximum position. He says his early models lacked bass "punch" - and
they did - which the judiciously applied feed-back remedied without any loss
of harmonic accuracy in the lower frequencies. Additionally, he notes,
over-damping in the bass causes "less bloom in the midrange and treble,"
moreover," the tighter you get the bass, the less realistic and satisfying
it is." You can add the maximum feed-back on his amp, and with the wrong
speaker, "all the beauty will go away and the music will sound more like a
salad."

This matches my own experiences pretty well.

Do these speaker designers match their
> speaker *only* to a particular model of tube amp?

No, but he does two versions of this speaker, one optimized for SS designs
and one for tubes.

I do however have some of the speaker designers favorite amplifiers, also
the amplifiers he has been using in shows, for many years.

>
> When you change the output impedance from 3 ohm to 2 ohm, you are
> changing the frequency response of the amp as measured across the
> speaker terminals. You may like the resulting sound, but be aware that
> you are essentially applying complex tone controls.

Funny enough, the speaker designer and the designer of the OTL tube amps
does not agree entirely about which setting that sounds the best (they are
using each others products for development etc.)

Anyway, I like having the possibility of doing minor changes to the sound.
Furthermore, I think that often, the desire to change the sound a little,
comes from the, sometimes strange, output from the recording studios. I have
a feeling that improving the recording techniques would benefit transparent
audio reproduction equipment a lot. Actually there are good recordings that
I find great pleasure in listening to on SS equipment, seems for the most
part to be live recordings and (primarely) older recordings without too much
hokus pokus involved.

KE


>

Richard D Pierce
August 26th 03, 03:49 PM
In article <unC2b.199337$Oz4.53781@rwcrnsc54>,
chung > wrote:
>All Ears wrote:
>>> Be very leery when someone says that the speakers are designed for amps
>>> with high output impedances. The reason is that both the amp's output
>>> impedance and the speaker's impedance are complex in nature, i.e., they
>>> are not pure resistances, but that there is a non-zero phase angle
>>> associated with that impedance that changes with frequency. As a result,
>>> you cannot get flat power transfer across all frequencies.
>>
>> This could be the reason that he recommends a Zobel network?
>
>Is "he" the amp designer or the speaker designer?
>
>The Zobel network is commonly used as a load on an amp to keep it
>stable.

NOT IT IS NOT, for the umpteenth time. The circuit used on the
output of an amplifier is NOT a "Zobel" circuit. It is there for
stability by assuring there's an adequate phase margin at high
frequencies. IT IS NOT A ZOBEL CIRCUIT.

A Zobel circuit is to compensate for the non resistive impedance
of a system so that a passive filter, e.g., a crossover, can be
loaded proeprly and operate correctly.

>Such a network should not have audible consequences, because
>the
>effect at audio frequencies is negligible (assuming the amp is stable).
>
>I would say that any amp designer who specifies that the amp be used
>with a Zobel network is showing incompetence.

I would say 1) that a manufacturer that uses the term "zobel" in
this fashion does not know what he is talking about and 2) if a
true zobel IS needed, the amplifier is GROSSLY misdesigned and
3) the recommendation in any case for the use of such is a sure
sign of incompetence, because a Zoble, being a complex conjugate
for the load impedance MUST be designed SPECIFICALLY for the
speaker: there is nor can there be such a beast as a "universal
zobel" for loudspeakers: this blindly and incorrectly assumes
that every loudspeaker has the same impedance vs frequency
function, which is an absurd assumption.

>>> What's wrong with designing speakers to be driven by voltage sources
>>> (i.e. low output impedance)?
>>
>> From a technical point of view, probably no major issues. I do however have
>> a quote from a review of the OTL tube amplifiers, that could be interesting
>> to get some comments on:
>>
>> "JB's listening has convinced him that the lower impedance of solid state
>> designs leads to an excessive damping, which plays havoc with the harmonic
>> structure of the bottom two octaves of the music.

Then the addition of simple series resistor fixes this problem.

Another amusing line from this quote "the harmonic structure in
the bottom two octaves" By defintion, you CAN'T HAVE much
"harmonic structure" in the btoom two octaves. You simply can't
fit a lot of harmonics in there.

>> This matches my own experiences pretty well.
>
>This really sounds like the speaker designer is doing his design by
>touch and feel, instead of using sound engineering principles and
>measurements.

Sounds like it to me, as well.

--
| Dick Pierce |
| Professional Audio Development |
| 1-781/826-4953 Voice and FAX |
| |

All Ears
August 26th 03, 04:04 PM
snip
> >> Be very leery when someone says that the speakers are designed for amps
> >> with high output impedances. The reason is that both the amp's output
> >> impedance and the speaker's impedance are complex in nature, i.e., they
> >> are not pure resistances, but that there is a non-zero phase angle
> >> associated with that impedance that changes with frequency. As a
result,
> >> you cannot get flat power transfer across all frequencies.
> >
> > This could be the reason that he recommends a Zobel network?
>
> Is "he" the amp designer or the speaker designer?

The speaker designer recommends trying if a Zobel network gives improvement
by connecting at speaker terminals or amplifier terminals.
>
> The Zobel network is commonly used as a load on an amp to keep it
> stable. Such a network should not have audible consequences, because the
> effect at audio frequencies is negligible (assuming the amp is stable).
>
> I would say that any amp designer who specifies that the amp be used
> with a Zobel network is showing incompetence.
>
> >>
> >> What's wrong with designing speakers to be driven by voltage sources
> >> (i.e. low output impedance)?
> >
> > From a technical point of view, probably no major issues. I do however
have
> > a quote from a review of the OTL tube amplifiers, that could be
interesting
> > to get some comments on:
> >
> > "JB's listening has convinced him that the lower impedance of solid
state
> > designs leads to an excessive damping, which plays havoc with the
harmonic
> > structure of the bottom two octaves of the music. Such damping may, he
says,
> > give the lows more "punch" but at the price of musical truth ("it
swallows
> > the harmonics"). The harmonics collapse (the Telarc bass syndrome of the
> > Eighties?). and the bass, while powerful, becomes an undifferentiated
mass.
> > To some extend you can hear the harmonics go to pot if you (using a
speaker
> > like the Maggies or the Pipedreams) turn the feedback control on the
amps to
> > their maximum position. He says his early models lacked bass "punch" -
and
> > they did - which the judiciously applied feed-back remedied without any
loss
> > of harmonic accuracy in the lower frequencies. Additionally, he notes,
> > over-damping in the bass causes "less bloom in the midrange and treble,"
> > moreover," the tighter you get the bass, the less realistic and
satisfying
> > it is." You can add the maximum feed-back on his amp, and with the wrong
> > speaker, "all the beauty will go away and the music will sound more like
a
> > salad."
> >
> > This matches my own experiences pretty well.
>
> This really sounds like the speaker designer is doing his design by
> touch and feel, instead of using sound engineering principles and
> measurements.

The quote is from a review of the OTL tube amplifiers....

>
> When you have different frequency response irregularities due to
> different and significant values of output impedances, you can have any
> number of different perceived responses from a speaker. Everything is
> subjective in his description. When you hear him say "harmonics go to
> pot", you may want to ask him to explain in technical terms.

I think this particular expression is from the reviewer.
>
> When you change the frequency response, you can perceive differences
> that may not appear like they are due to frequency response: image
> opening up, proper harmonic balance, blooming, etc. A change in the
> upper mid-range can cause a different perception of the bass
> performance, too.

Yes this is probably true, but as long as I can get acoustic instruments,
voices, etc. to sound natural and realistic to me, I am pretty well contend.

>
> How does music sound like a salad?

My imagination would assume something like little pieces of stuff mixed
together.... :)

How tight should the bass be?

I tend to use an acoustic bass to determine this, and listen for "body" of
the instrument. If I get the bass too tight, it is like the lowest part of
the instrument does not really follow the music, if it is not tight enough
the detail in the bass will be fleshed out.


> >
> > Do these speaker designers match their
> >> speaker *only* to a particular model of tube amp?
> >
> > No, but he does two versions of this speaker, one optimized for SS
designs
> > and one for tubes.
> >
> > I do however have some of the speaker designers favorite amplifiers,
also
> > the amplifiers he has been using in shows, for many years.
> >
> >>
> >> When you change the output impedance from 3 ohm to 2 ohm, you are
> >> changing the frequency response of the amp as measured across the
> >> speaker terminals. You may like the resulting sound, but be aware that
> >> you are essentially applying complex tone controls.
> >
> > Funny enough, the speaker designer and the designer of the OTL tube amps
> > does not agree entirely about which setting that sounds the best (they
are
> > using each others products for development etc.)
>
> Just like no two people will set up an equalizer the exact same way.
>
> >
> > Anyway, I like having the possibility of doing minor changes to the
sound.
>
> No one will tell you your preferences are wrong. But some of us will say
> that it may not be a good idea to put in permanant tone controls.
>
> > Furthermore, I think that often, the desire to change the sound a
little,
> > comes from the, sometimes strange, output from the recording studios. I
have
> > a feeling that improving the recording techniques would benefit
transparent
> > audio reproduction equipment a lot. Actually there are good recordings
that
> > I find great pleasure in listening to on SS equipment, seems for the
most
> > part to be live recordings and (primarely) older recordings without too
much
> > hokus pokus involved.
> >
> > KE
> >
> >
> >>
> >
> >
>

chung
August 26th 03, 08:22 PM
All Ears wrote:
> snip
>> >> Be very leery when someone says that the speakers are designed for amps
>> >> with high output impedances. The reason is that both the amp's output
>> >> impedance and the speaker's impedance are complex in nature, i.e., they
>> >> are not pure resistances, but that there is a non-zero phase angle
>> >> associated with that impedance that changes with frequency. As a
> result,
>> >> you cannot get flat power transfer across all frequencies.
>> >
>> > This could be the reason that he recommends a Zobel network?
>>
>> Is "he" the amp designer or the speaker designer?
>
> The speaker designer recommends trying if a Zobel network gives improvement
> by connecting at speaker terminals or amplifier terminals.

Did he give any details on how to build the network?

>>
>> The Zobel network is commonly used as a load on an amp to keep it
>> stable. Such a network should not have audible consequences, because the
>> effect at audio frequencies is negligible (assuming the amp is stable).
>>
>> I would say that any amp designer who specifies that the amp be used
>> with a Zobel network is showing incompetence.
>>
>> >>
>> >> What's wrong with designing speakers to be driven by voltage sources
>> >> (i.e. low output impedance)?
>> >
>> > From a technical point of view, probably no major issues. I do however
> have
>> > a quote from a review of the OTL tube amplifiers, that could be
> interesting
>> > to get some comments on:
>> >
>> > "JB's listening has convinced him that the lower impedance of solid
> state
>> > designs leads to an excessive damping, which plays havoc with the
> harmonic
>> > structure of the bottom two octaves of the music. Such damping may, he
> says,
>> > give the lows more "punch" but at the price of musical truth ("it
> swallows
>> > the harmonics"). The harmonics collapse (the Telarc bass syndrome of the
>> > Eighties?). and the bass, while powerful, becomes an undifferentiated
> mass.
>> > To some extend you can hear the harmonics go to pot if you (using a
> speaker
>> > like the Maggies or the Pipedreams) turn the feedback control on the
> amps to
>> > their maximum position. He says his early models lacked bass "punch" -
> and
>> > they did - which the judiciously applied feed-back remedied without any
> loss
>> > of harmonic accuracy in the lower frequencies. Additionally, he notes,
>> > over-damping in the bass causes "less bloom in the midrange and treble,"
>> > moreover," the tighter you get the bass, the less realistic and
> satisfying
>> > it is." You can add the maximum feed-back on his amp, and with the wrong
>> > speaker, "all the beauty will go away and the music will sound more like
> a
>> > salad."
>> >
>> > This matches my own experiences pretty well.
>>
>> This really sounds like the speaker designer is doing his design by
>> touch and feel, instead of using sound engineering principles and
>> measurements.
>
> The quote is from a review of the OTL tube amplifiers....

Who's JB? According to this review, he appears to be the amp designer.
Are you saying he's ther reviewer? He seems to be saying that there are
all kinds of effects due to different output impedances reacting with
speaker impedance, which is pretty obvious.


>
>>
>> When you have different frequency response irregularities due to
>> different and significant values of output impedances, you can have any
>> number of different perceived responses from a speaker. Everything is
>> subjective in his description. When you hear him say "harmonics go to
>> pot", you may want to ask him to explain in technical terms.
>
> I think this particular expression is from the reviewer.

But it was in quotation marks, so I assume it was coming from JB, no?

All Ears
August 27th 03, 02:36 AM
"chung" > wrote in message
...
> All Ears wrote:
> > snip
> >> >> Be very leery when someone says that the speakers are designed for
amps
> >> >> with high output impedances. The reason is that both the amp's
output
> >> >> impedance and the speaker's impedance are complex in nature, i.e.,
they
> >> >> are not pure resistances, but that there is a non-zero phase angle
> >> >> associated with that impedance that changes with frequency. As a
> > result,
> >> >> you cannot get flat power transfer across all frequencies.
> >> >
> >> > This could be the reason that he recommends a Zobel network?
> >>
> >> Is "he" the amp designer or the speaker designer?
> >
> > The speaker designer recommends trying if a Zobel network gives
improvement
> > by connecting at speaker terminals or amplifier terminals.
>
> Did he give any details on how to build the network?

They are included with the speakers...

>
> >>
> >> The Zobel network is commonly used as a load on an amp to keep it
> >> stable. Such a network should not have audible consequences, because
the
> >> effect at audio frequencies is negligible (assuming the amp is stable).
> >>
> >> I would say that any amp designer who specifies that the amp be used
> >> with a Zobel network is showing incompetence.
> >>
> >> >>
> >> >> What's wrong with designing speakers to be driven by voltage sources
> >> >> (i.e. low output impedance)?
> >> >
> >> > From a technical point of view, probably no major issues. I do
however
> > have
> >> > a quote from a review of the OTL tube amplifiers, that could be
> > interesting
> >> > to get some comments on:
> >> >
> >> > "JB's listening has convinced him that the lower impedance of solid
> > state
> >> > designs leads to an excessive damping, which plays havoc with the
> > harmonic
> >> > structure of the bottom two octaves of the music. Such damping may,
he
> > says,
> >> > give the lows more "punch" but at the price of musical truth ("it
> > swallows
> >> > the harmonics"). The harmonics collapse (the Telarc bass syndrome of
the
> >> > Eighties?). and the bass, while powerful, becomes an undifferentiated
> > mass.
> >> > To some extend you can hear the harmonics go to pot if you (using a
> > speaker
> >> > like the Maggies or the Pipedreams) turn the feedback control on the
> > amps to
> >> > their maximum position. He says his early models lacked bass
"punch" -
> > and
> >> > they did - which the judiciously applied feed-back remedied without
any
> > loss
> >> > of harmonic accuracy in the lower frequencies. Additionally, he
notes,
> >> > over-damping in the bass causes "less bloom in the midrange and
treble,"
> >> > moreover," the tighter you get the bass, the less realistic and
> > satisfying
> >> > it is." You can add the maximum feed-back on his amp, and with the
wrong
> >> > speaker, "all the beauty will go away and the music will sound more
like
> > a
> >> > salad."
> >> >
> >> > This matches my own experiences pretty well.
> >>
> >> This really sounds like the speaker designer is doing his design by
> >> touch and feel, instead of using sound engineering principles and
> >> measurements.
> >
> > The quote is from a review of the OTL tube amplifiers....
>
> Who's JB? According to this review, he appears to be the amp designer.
> Are you saying he's ther reviewer? He seems to be saying that there are
> all kinds of effects due to different output impedances reacting with
> speaker impedance, which is pretty obvious.

The reviewer is quoting JB who is the designer of the amps. (The Absolute
Sound, issue 115, reviewer initials HP?)

>
>
> >
> >>
> >> When you have different frequency response irregularities due to
> >> different and significant values of output impedances, you can have any
> >> number of different perceived responses from a speaker. Everything is
> >> subjective in his description. When you hear him say "harmonics go to
> >> pot", you may want to ask him to explain in technical terms.
> >
> > I think this particular expression is from the reviewer.
>
> But it was in quotation marks, so I assume it was coming from JB, no?

Not that exact phrase.

KE
>

chung
August 27th 03, 06:07 AM
Richard D Pierce wrote:
> In article <unC2b.199337$Oz4.53781@rwcrnsc54>,
> chung > wrote:
>>All Ears wrote:
>>>> Be very leery when someone says that the speakers are designed for amps
>>>> with high output impedances. The reason is that both the amp's output
>>>> impedance and the speaker's impedance are complex in nature, i.e., they
>>>> are not pure resistances, but that there is a non-zero phase angle
>>>> associated with that impedance that changes with frequency. As a result,
>>>> you cannot get flat power transfer across all frequencies.
>>>
>>> This could be the reason that he recommends a Zobel network?
>>
>>Is "he" the amp designer or the speaker designer?
>>
>>The Zobel network is commonly used as a load on an amp to keep it
>>stable.
>
> NOT IT IS NOT, for the umpteenth time. The circuit used on the
> output of an amplifier is NOT a "Zobel" circuit. It is there for
> stability by assuring there's an adequate phase margin at high
> frequencies. IT IS NOT A ZOBEL CIRCUIT.
>
> A Zobel circuit is to compensate for the non resistive impedance
> of a system so that a passive filter, e.g., a crossover, can be
> loaded proeprly and operate correctly.
>

You're right, a Zobel network goes between the crossover network and the
driver so that the crossover sees a more or less constant resistance.
When I read that the speaker (or the amp) designer recommends an
external Zobel network, I assumed that he was talking about a series R-C
circuit (often also called Zobel, which is technically wrong) to be
connected to the output of a power amp to keep the amp stable.

It does not make any sense for the speaker designer to recommend a Zobel
network, since he should have put one in the speaker. It's not something
that the user can do.

If an amp designer recommends a series RC circuit to be connected to the
said amp's output terminals, that is a sign of incompetence.

Richard D Pierce
August 27th 03, 04:06 PM
In article <01X2b.271709$Ho3.36014@sccrnsc03>,
All Ears > wrote:
>snip
>> >I would say that any amp designer who specifies that the amp be used
>> >with a Zobel network is showing incompetence.
>>
>> I would say 1) that a manufacturer that uses the term "zobel" in
>> this fashion does not know what he is talking about and 2) if a
>> true zobel IS needed, the amplifier is GROSSLY misdesigned and
>> 3) the recommendation in any case for the use of such is a sure
>> sign of incompetence, because a Zoble, being a complex conjugate
>> for the load impedance MUST be designed SPECIFICALLY for the
>> speaker: there is nor can there be such a beast as a "universal
>> zobel" for loudspeakers: this blindly and incorrectly assumes
>> that every loudspeaker has the same impedance vs frequency
>> function, which is an absurd assumption.
>
>The Zobel network is supplied with, and made for the speakers.....

Then why is it not IN the speakers?

How is it connected? In serires with the speakers? In parallel?

What does this circuit look like?

--
| Dick Pierce |
| Professional Audio Development |
| 1-781/826-4953 Voice and FAX |
| |

All Ears
August 29th 03, 12:20 AM
snip

> If that is the case, then when someone uses such a network with an
> OTL-type amp, he will notice a pretty significant difference in sound
> compared to without that network. The sound now may appear closer to
> when the speakers are driven by low output impedance amps.
>
> Perhaps Mr. Ears can clarify if that is the case.

It is an R-C network in series, placed across the speaker terminals. It
consists of:

Strange resistor, looking like a semiconductor, with the text: MP 820, 10.0
1%, and a capasitor: Musicap .01/1600V +- 5%

It is supposed to make the amplifier see a more resitive like load.

I have not done any listening with out the network, so I really cannot say
how big the difference is with and without. The speaker designer knows the
amplifiers I use, and they are all on the list of amplifiers where the
network is recommended. Even the SS amplifiers with a damping factor "far
greater than 1000"

KE

chung
August 29th 03, 01:30 AM
All Ears wrote:
> snip
>
>> If that is the case, then when someone uses such a network with an
>> OTL-type amp, he will notice a pretty significant difference in sound
>> compared to without that network. The sound now may appear closer to
>> when the speakers are driven by low output impedance amps.
>>
>> Perhaps Mr. Ears can clarify if that is the case.
>
> It is an R-C network in series, placed across the speaker terminals. It
> consists of:
>
> Strange resistor, looking like a semiconductor, with the text: MP 820, 10.0
> 1%, and a capasitor: Musicap .01/1600V +- 5%

Does the resistor look like the ones in this sepc sheet?
http://www.caddock.com/Online_catalog/Mrktg_Lit/MP800_Series.pdf

If so, it is a 10 ohm resistor rated at 20W.

Is the cap like this one (1st one on the list)?
http://www.hovlandcompany.com/pdf/prices/MusiCapsPrc.pdf

If so, it is a 0.01uF capacitor.

>
> It is supposed to make the amplifier see a more resitive like load.

Assuming those are the right components, that network acts like an
impedance of 800 ohms at 20KHz, so it does not do anything in the audio
band.

>
> I have not done any listening with out the network, so I really cannot say
> how big the difference is with and without. The speaker designer knows the
> amplifiers I use, and they are all on the list of amplifiers where the
> network is recommended. Even the SS amplifiers with a damping factor "far
> greater than 1000"

If it's a .01uF in series with 10 ohms to be connected in parallel with
speaker terminals, then it is not a Zobel network, but rather something
to keep incompetently designed amps stable. I doubt if it has any effect
on sound, unless your amp is incompetently designed and requires the
network to maintain stability.

If you have access to a DVM that measures AC voltages, and a test CD
with test tones, you can measure the voltage across the speaker
terminals (keep the level low), and see if whether the network is
connected in parallel makes any difference. It shouldn't.

>
> KE
>
>

Richard D Pierce
August 29th 03, 02:53 AM
In article >,
All Ears > wrote:
>snip
>
>> If that is the case, then when someone uses such a network with an
>> OTL-type amp, he will notice a pretty significant difference in sound
>> compared to without that network. The sound now may appear closer to
>> when the speakers are driven by low output impedance amps.
>>
>> Perhaps Mr. Ears can clarify if that is the case.
>
>It is an R-C network in series, placed across the speaker terminals. It
>consists of:
>
>Strange resistor, looking like a semiconductor, with the text: MP 820, 10.0
>1%, and a capasitor: Musicap .01/1600V +- 5%
>
>It is supposed to make the amplifier see a more resitive like load.

It is most certainly NOT a "zobel" circuit in that there is no
reactive component in any loudspeaker that has the conjugate
properties of this circuit. And, thus, is does not, indeed, it
CANNOT "make the amplifier see a more resistive load."

The ENTIRE point to such "zobel circuits," i.e., complex
conjugate compensation circuits, is to develop the conjugate
function of a non-resistave load. A series resistor-capacitor as
you describe will compnesate for the effective series
inductance- resistance of a dynamic speaker's voice coil. But to
do so the magnitude of the reactance has to be correct, this one
is off by a factor of ONE HUNDRED!

A typical conjugate "zobel" for a tweeter, for example, would
have a capacitor on the order of 1-5 uF and would apply
compensation in the realm of a few kHz, whereas assuming
you've read the values properly, and I have no doubt that you
were careful in doing so, this circuit has a capacitor that is
too small in value by a factor of 100-500. That means it has no
effect until around a half a megahertz!

To claim that this circuit "is supposed to make the amplifier
see a more resitive like load," if that what the manufacturer is
claiming, is patently absurd.

Further, the mild inductive load presented by most dynamic
speakers out of band has NEVER been a problem to drive by even
barely competent amplifiers. Capactive loads are another
issue, as the worsen the phase margin of marginally stable
amplifiers. Inductive loads, if anything, HELP the stability.

If this manufacturer is claiming that this circuit is necessary
or even that it makes a difference, then that manufacturer is
effectively admitting that the amplfiier is GROSSLY
incompetently designed. I would even posit that such an
amplifier is NEGLIGENTLY designed. Jesus, you'd have to work
REALLY HARD to make an amplifier so awfully bad for such a
circuit to make any difference.

And, if what you are relating is true, it is a CLASSIC
example of the gross imcompetence OR the outright flim-flammery
of some people in the high-end audio business.

>I have not done any listening with out the network, so I really cannot say
>how big the difference is with and without. The speaker designer knows the
>amplifiers I use, and they are all on the list of amplifiers where the
>network is recommended. Even the SS amplifiers with a damping factor "far
>greater than 1000"

First, as has been said many time, the "damping factor" is pure
nonsense, unless, of sourse, you want to talk about the
preposterously low damping factors exemplified by amplifiers
with output impedances in the realm of 3 ohms. Second, such a
"zoble" has ABSOLUTELY NOTHING to do with "damping factor" of
any sort.

This sort of technical bullsh*t never ceases to amaze and, to a
great extent, sadden me. This sort of pervasive attitude that
manufacturers can make such preposterous claims is what has
resulted in driving not a small amount of REAL engineering
talent AWAY from this realm.

--
| Dick Pierce |
| Professional Audio Development |
| 1-781/826-4953 Voice and FAX |
| |

All Ears
August 29th 03, 07:01 PM
> This sort of technical bullsh*t never ceases to amaze and, to a
> great extent, sadden me. This sort of pervasive attitude that
> manufacturers can make such preposterous claims is what has
> resulted in driving not a small amount of REAL engineering
> talent AWAY from this realm.

I have been looking a little more in the manual for the speakers, the
network is described as an RC network. It is also strongly recommended
listening to the system with and without the network, to see which is
preferred. It is said however, that only a small percentage of amplifiers
will not benefit from the network.

Taken the overall performance of the speakers into concideration, I really
can't complain that such a device is included, it is optional to use it.

Included with the speakers is also an alignment tool to set optimal toe-in
and a tool to level the speakers. This is of course also optional to do so,
but I do prefer to use the recommendation as starting point.

Furthermore, the manual describes the Golden Rule to determine initial
speaker placement, which is seldom seen in speaker manuals.

KE

>
> --
> | Dick Pierce |
> | Professional Audio Development |
> | 1-781/826-4953 Voice and FAX |
> | |

chung
August 29th 03, 11:34 PM
All Ears wrote:
>> This sort of technical bullsh*t never ceases to amaze and, to a
>> great extent, sadden me. This sort of pervasive attitude that
>> manufacturers can make such preposterous claims is what has
>> resulted in driving not a small amount of REAL engineering
>> talent AWAY from this realm.
>
> I have been looking a little more in the manual for the speakers, the
> network is described as an RC network. It is also strongly recommended
> listening to the system with and without the network, to see which is
> preferred. It is said however, that only a small percentage of amplifiers
> will not benefit from the network.
>
> Taken the overall performance of the speakers into concideration, I really
> can't complain that such a device is included, it is optional to use it.

If you like the way those speakers sound, that's great. However, the
fact that designer (or marketeer?) stated that "only a small percentage
of amplifiers will not benefit from the network" is an indication that
his opinion is not always to be taken literally. I would take his
speaker cable recommendations with skepticism. If he can hear
differences as a result of that network, he is liable to hear
differences from cables that you and I cannot detect.

>
> Included with the speakers is also an alignment tool to set optimal toe-in
> and a tool to level the speakers. This is of course also optional to do so,
> but I do prefer to use the recommendation as starting point.
>
> Furthermore, the manual describes the Golden Rule to determine initial
> speaker placement, which is seldom seen in speaker manuals.

What is the "Golden Rule"? Most speakers manuals come with placement
tips. How's his Golden Rule different?

>
> KE
>
>>
>> --
>> | Dick Pierce |
>> | Professional Audio Development |
>> | 1-781/826-4953 Voice and FAX |
>> | |
>

All Ears
August 30th 03, 03:56 AM
"chung" > wrote in message
.net...
> All Ears wrote:
> >> This sort of technical bullsh*t never ceases to amaze and, to a
> >> great extent, sadden me. This sort of pervasive attitude that
> >> manufacturers can make such preposterous claims is what has
> >> resulted in driving not a small amount of REAL engineering
> >> talent AWAY from this realm.
> >
> > I have been looking a little more in the manual for the speakers, the
> > network is described as an RC network. It is also strongly recommended
> > listening to the system with and without the network, to see which is
> > preferred. It is said however, that only a small percentage of
amplifiers
> > will not benefit from the network.
> >
> > Taken the overall performance of the speakers into concideration, I
really
> > can't complain that such a device is included, it is optional to use it.
>
> If you like the way those speakers sound, that's great. However, the
> fact that designer (or marketeer?) stated that "only a small percentage
> of amplifiers will not benefit from the network" is an indication that
> his opinion is not always to be taken literally. I would take his
> speaker cable recommendations with skepticism. If he can hear
> differences as a result of that network, he is liable to hear
> differences from cables that you and I cannot detect.

I do like the speakers a lot, and it seems like I'm not the only one, since
these speakers have recieved more than 70 best of show accolades, and most
of the reviewers that has evaluated the speakers actually bought them. It is
of course up to the individual buyer how to use the speakers, and which
equipment to combine it with, but it would indicate to me that the designer
actually knows what he is doing.
>
> >
> > Included with the speakers is also an alignment tool to set optimal
toe-in
> > and a tool to level the speakers. This is of course also optional to do
so,
> > but I do prefer to use the recommendation as starting point.
> >
> > Furthermore, the manual describes the Golden Rule to determine initial
> > speaker placement, which is seldom seen in speaker manuals.
>
> What is the "Golden Rule"? Most speakers manuals come with placement
> tips. How's his Golden Rule different?

It's late, I'm tired... I'll post this part of the manual tomorrow...

>
> >
> > KE
> >
> >>
> >> --
> >> | Dick Pierce |
> >> | Professional Audio Development |
> >> | 1-781/826-4953 Voice and FAX |
> >> | |
> >
>

Stewart Pinkerton
August 30th 03, 04:10 PM
On Fri, 29 Aug 2003 18:01:18 GMT, "All Ears" >
wrote:

>> This sort of technical bullsh*t never ceases to amaze and, to a
>> great extent, sadden me. This sort of pervasive attitude that
>> manufacturers can make such preposterous claims is what has
>> resulted in driving not a small amount of REAL engineering
>> talent AWAY from this realm.
>
>I have been looking a little more in the manual for the speakers, the
>network is described as an RC network. It is also strongly recommended
>listening to the system with and without the network, to see which is
>preferred. It is said however, that only a small percentage of amplifiers
>will not benefit from the network.
>
>Taken the overall performance of the speakers into concideration, I really
>can't complain that such a device is included, it is optional to use it.

Sounds like a pretty useless device, and it belongs in the amp, not
the speaker. Only incompetent designs like some Naim power amps would
require such additional stabilisation assistance.

>Included with the speakers is also an alignment tool to set optimal toe-in
>and a tool to level the speakers. This is of course also optional to do so,
>but I do prefer to use the recommendation as starting point.

It's always a good idea to start with the manufacturer's
recommendations. In any particular room, that may of course not be
where you finish!

>Furthermore, the manual describes the Golden Rule to determine initial
>speaker placement, which is seldom seen in speaker manuals.

For the very good reason that it is inapplicable to speaker placement.
Speakers of different dispersion will have different placement and
toe-in requirements, and to invoke the Golden Rule smacks of the same
numerology nonsense perpetrated by George Cardas for his cables.

Mind you, given the meaningless technobabble that this manufacturer
has perpetrated in general terms, it's all pretty consistent!
--

Stewart Pinkerton | Music is Art - Audio is Engineering

All Ears
August 31st 03, 12:59 AM
"Stewart Pinkerton" > wrote in message
...
> On Fri, 29 Aug 2003 18:01:18 GMT, "All Ears" >
> wrote:
>
> >> This sort of technical bullsh*t never ceases to amaze and, to a
> >> great extent, sadden me. This sort of pervasive attitude that
> >> manufacturers can make such preposterous claims is what has
> >> resulted in driving not a small amount of REAL engineering
> >> talent AWAY from this realm.
> >
> >I have been looking a little more in the manual for the speakers, the
> >network is described as an RC network. It is also strongly recommended
> >listening to the system with and without the network, to see which is
> >preferred. It is said however, that only a small percentage of amplifiers
> >will not benefit from the network.
> >
> >Taken the overall performance of the speakers into concideration, I
really
> >can't complain that such a device is included, it is optional to use it.
>
> Sounds like a pretty useless device, and it belongs in the amp, not
> the speaker. Only incompetent designs like some Naim power amps would
> require such additional stabilisation assistance.

It is stated that the RC network is not to be used, if the amplifier has
this one included already. It is also said that most amplifiers do not have
this network included?

Would you generally say that Naim equipment is incompetently designed?
>
> >Included with the speakers is also an alignment tool to set optimal
toe-in
> >and a tool to level the speakers. This is of course also optional to do
so,
> >but I do prefer to use the recommendation as starting point.
>
> It's always a good idea to start with the manufacturer's
> recommendations. In any particular room, that may of course not be
> where you finish!
>
> >Furthermore, the manual describes the Golden Rule to determine initial
> >speaker placement, which is seldom seen in speaker manuals.
>
> For the very good reason that it is inapplicable to speaker placement.
> Speakers of different dispersion will have different placement and
> toe-in requirements, and to invoke the Golden Rule smacks of the same
> numerology nonsense perpetrated by George Cardas for his cables.

Okay I'll quote the getting started chapter:

" If you have a rectangular room use the Golden Rule to determine initial
speaker placement. Multiply the ceiling hight by .681 to determine the
distance from the rear wall to the front baffle. Then multiply the room with
by .276 to determine the distance from the side wall to the center of the
tweeter. I would then measure the lenght of the room to see whether the
running lenght has been divided into quasi 1/4s or 1/3s. The use of 1/4s
will null the major nodes within the listening space. Utilizing 1/3s
(relative to seating position) will tend to embellish the boundary
reinforcement of the bass. This procedure will minimize boundary reflections
of the mid and high freq. while utilizing the boundary reinforcements of the
bass 1/4s being neutral and 1/3s being additive.

When positioning the speakers on a long wall or in a square room it is our
recommendation that you space them approx. 6.5" apart center to center (up
to a 7" max.). Spacing in excess of 7" will tend to decrease image density,
body and impact. You will gain stage width but lose some ot the extreme
layering potential. I would then measure the running lenght of the room and
position the speakers using the quasi 1/4s or 1/3s rule. For the very best
results make sure that the distance from the floor to the woofer center does
not equal the distance from the woofer center to rear of side walls. The
same rule is true for the distance from the woofer center to the ceiling and
rear wall."

The toe-in is taken care of, and I would assume that he has some idea to the
speakers dispersion pattern.

KE
>
> Mind you, given the meaningless technobabble that this manufacturer
> has perpetrated in general terms, it's all pretty consistent!
> --
>
> Stewart Pinkerton | Music is Art - Audio is Engineering

Stewart Pinkerton
August 31st 03, 04:30 PM
On Sat, 30 Aug 2003 23:59:54 GMT, "All Ears" >
wrote:

>"Stewart Pinkerton" > wrote in message
...
>> On Fri, 29 Aug 2003 18:01:18 GMT, "All Ears" >
>> wrote:
>>
>> >> This sort of technical bullsh*t never ceases to amaze and, to a
>> >> great extent, sadden me. This sort of pervasive attitude that
>> >> manufacturers can make such preposterous claims is what has
>> >> resulted in driving not a small amount of REAL engineering
>> >> talent AWAY from this realm.
>> >
>> >I have been looking a little more in the manual for the speakers, the
>> >network is described as an RC network. It is also strongly recommended
>> >listening to the system with and without the network, to see which is
>> >preferred. It is said however, that only a small percentage of amplifiers
>> >will not benefit from the network.
>> >
>> >Taken the overall performance of the speakers into concideration, I really
>> >can't complain that such a device is included, it is optional to use it.
>>
>> Sounds like a pretty useless device, and it belongs in the amp, not
>> the speaker. Only incompetent designs like some Naim power amps would
>> require such additional stabilisation assistance.
>
>It is stated that the RC network is not to be used, if the amplifier has
>this one included already. It is also said that most amplifiers do not have
>this network included?

Most (but certainly not all!) amplifiers are adequately stable, and
don't *need* any such device.

>Would you generally say that Naim equipment is incompetently designed?

The old amps were marginally stable, hence the insistence by Naim on
the use of their own highly inductive cable, and their CD players are
invariably 5 years out of date when they are launched. Naim gear is
known to have a 'house sound', which is another way of saying that it
is not accurate.

>> >Furthermore, the manual describes the Golden Rule to determine initial
>> >speaker placement, which is seldom seen in speaker manuals.
>>
>> For the very good reason that it is inapplicable to speaker placement.
>> Speakers of different dispersion will have different placement and
>> toe-in requirements, and to invoke the Golden Rule smacks of the same
>> numerology nonsense perpetrated by George Cardas for his cables.
>
>Okay I'll quote the getting started chapter:
>
>" If you have a rectangular room use the Golden Rule to determine initial
>speaker placement. Multiply the ceiling hight by .681 to determine the
>distance from the rear wall to the front baffle. Then multiply the room with
>by .276 to determine the distance from the side wall to the center of the
>tweeter.

Totally meaningless advice, and horrifyingly incompetent. If the
speaker has been 'voiced' to take account of boundary effects, then
the recommendation should be for particular distances from side and
back walls, not some fraction of the room dimensions. BTW, these
quoted fractions don't seem to have any obvious relation to the Golden
Ratio, which is approximately 1.62:1

>I would then measure the lenght of the room to see whether the
>running lenght has been divided into quasi 1/4s or 1/3s. The use of 1/4s
>will null the major nodes within the listening space. Utilizing 1/3s
>(relative to seating position) will tend to embellish the boundary
>reinforcement of the bass. This procedure will minimize boundary reflections
>of the mid and high freq. while utilizing the boundary reinforcements of the
>bass 1/4s being neutral and 1/3s being additive.

Horribly bad advice, since 1/4 of the room dimension is the very
*worst* place to put a speaker, it will reinforce the natural
resonance. You should use 1/5 or 1/3.

>When positioning the speakers on a long wall or in a square room it is our
>recommendation that you space them approx. 6.5" apart center to center (up
>to a 7" max.). Spacing in excess of 7" will tend to decrease image density,
>body and impact.

I presume that these are feet, not inches! This is also bad advice,
since it's the *angle* between the speakers that matters for imaging,
not the absolute distance. You might want them ten feet apart in a
long room, or only four feet apart in a small room.

> You will gain stage width but lose some ot the extreme
>layering potential. I would then measure the running lenght of the room and
>position the speakers using the quasi 1/4s or 1/3s rule.

Again, that should be 1/5, most definitely *not* 1/4.

> For the very best
>results make sure that the distance from the floor to the woofer center does
>not equal the distance from the woofer center to rear of side walls. The
>same rule is true for the distance from the woofer center to the ceiling and
>rear wall."

That at least is sensible advice, but it would be more helpful to
suggest good ratios, such as 1.6:1, rather than just 'not equal'.

>The toe-in is taken care of, and I would assume that he has some idea to the
>speakers dispersion pattern.

From most of the above, I would assume that this designer is
*horrifically* ignorant of acoustic basics. This does not fill one
with confidence regarding his ability to design a loudspeaker!

>> Mind you, given the meaningless technobabble that this manufacturer
>> has perpetrated in general terms, it's all pretty consistent!

He's certainly maintaining a perfect score in this respect...........
--

Stewart Pinkerton | Music is Art - Audio is Engineering