Yes, it would have been around that time.
Was I supposed to signal you that the coast was clear? I'm sorry if I let my guard down and endangered your life. I must say it's been a week or two now since the Illuminati Bounty Hunters when through here searching for you!
Best Regards,
Captain "X"
Not true. Both types of device produce both odd and even order distortion. In both cases the dominant device distortion is second-order. The difference comes in the circuits, but even there the similarities exceed the differences. Push-pull cancels even-order, for both SS and valves.wadest said:
Reasonably high DF is important for good bass response with most loudspeakers. It says nothing about the rest of the frequency spectrum, where output impedance is typically higher but relatively less important provided it remains smallish and linearish.
Do valve amps sound better than SS? Only under certain circumstances:
- the listener knows which he is listening to
- the SS amp is poorly designed and/or driven into hard clipping so lots of higher order odd-order distortion occurs
- the valve amp is poorly designed (or SE) so adds significant amounts of even-order distortion - some consider this 'musical'
- the valve amp has a limited frequency range with an early HF rolloff - some consider this 'warm' or 'smooth'
Can we drop the naive SS vs. vacuum myths and get back to talking about DF?
DF, efficiency and control...
I have some Damping Factor related questions...
I am trying to figure out how to calculate the amount of controlling force an amplifier exerts on a voice coil when the amp is switched on but not sending any voltage to the voice coil ie The amp send a 10 ms impulse representing a drum strike, what happens next, over the next 10 to 200 ms or so....?
For ease of calculation I assume:
(1) 8 Ohm speaker load, flat resistive load for the moment ie ignore voice coil heating and increasing resistance.
(2) A higher than average driver efficiency of 1%.
(3) Amplifier damping factor of 100.
(4) As 99% of the electro magnetic force in a speaker driver is burned off as wasted heat and frictional losses will "massively increasing" the DF to 1,000 have a material effect?
Thanks in advance if any of you guys can point me to some peer reviewed papers on the above, or if any engineers can explain it in reasonably simple terms....I am not an electronics engineer so please keep it simple!
Cheers
Derek.
I have some Damping Factor related questions...
I am trying to figure out how to calculate the amount of controlling force an amplifier exerts on a voice coil when the amp is switched on but not sending any voltage to the voice coil ie The amp send a 10 ms impulse representing a drum strike, what happens next, over the next 10 to 200 ms or so....?
For ease of calculation I assume:
(1) 8 Ohm speaker load, flat resistive load for the moment ie ignore voice coil heating and increasing resistance.
(2) A higher than average driver efficiency of 1%.
(3) Amplifier damping factor of 100.
(4) As 99% of the electro magnetic force in a speaker driver is burned off as wasted heat and frictional losses will "massively increasing" the DF to 1,000 have a material effect?
Thanks in advance if any of you guys can point me to some peer reviewed papers on the above, or if any engineers can explain it in reasonably simple terms....I am not an electronics engineer so please keep it simple!
Cheers
Derek.
The Amplifier "listens" to the speaker cables.
The amplifier Output is actually an INPUT.
The -IN input is connected to the speaker leads.
By listening to the signals applied to the output the amplifier maintains an output impedance.
If the amplifier Damping Factor is stated as 100 for an 8ohms load, it is confirming that at some frequency the output impedance is 8/100ths of an ohm, i.e. 80milli-ohms.
Add on all the other impedances in the route from the amplifier output through cabling and connections and solder joints and inductors/resistors on the way to the speaker AND on the way back to the Output Source.
These added impedances can easily exceed 100milli-ohms and in some cases can exceed 1 ohm.
If the amplifier is specified as having a Damping Factor of 1000 @ 100Hz then you know that instead of 80 milli-ohms @ unknown frequency the amplifier has 8milli-ohms of output impedance @ 100Hz.
The amplifier Output is actually an INPUT.
The -IN input is connected to the speaker leads.
By listening to the signals applied to the output the amplifier maintains an output impedance.
If the amplifier Damping Factor is stated as 100 for an 8ohms load, it is confirming that at some frequency the output impedance is 8/100ths of an ohm, i.e. 80milli-ohms.
Add on all the other impedances in the route from the amplifier output through cabling and connections and solder joints and inductors/resistors on the way to the speaker AND on the way back to the Output Source.
These added impedances can easily exceed 100milli-ohms and in some cases can exceed 1 ohm.
If the amplifier is specified as having a Damping Factor of 1000 @ 100Hz then you know that instead of 80 milli-ohms @ unknown frequency the amplifier has 8milli-ohms of output impedance @ 100Hz.
Thanks Andrew,
Following your explanation can you calculate / estimate what % of control the amp looses ( if any) when no signal / impulse is being sent to the speaker compared to the control it has when sending the signal / impulse ?
Another question please, does the DF affect how the amp handles the back EMF from the speaker driver ie when the driver is settling down after the initial implulse?
Cheers
Derek.
Following your explanation can you calculate / estimate what % of control the amp looses ( if any) when no signal / impulse is being sent to the speaker compared to the control it has when sending the signal / impulse ?
Another question please, does the DF affect how the amp handles the back EMF from the speaker driver ie when the driver is settling down after the initial implulse?
Cheers
Derek.
No, because I am not any good at AC circuit theory.
Not really, the other resistances/impedances swamp the amplifier output impedance value.
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Unless the amp has a seriously non-linear output impedance (amounting to a directional coupler) then the two figures will be the same.Overkill Audio said:
The 'back EMF' is fully accounted for in an impedance model of the speaker, so no new phenomenon takes place. Almost all talk of back EMF is misguided, but people think of it as 'deep knowledge'.
Calvin, i'm talking about what i read in Audio Engineering Society journals. I don't know about where you got your information.
Hi,
@wadest
The source of a information or of knowledge is of no importance.
What counts is the correctness and trueth of a information.
The transconductance curve certainly tells something about the 'intrinsic' distortion of a part, but as Jan pointed out correctly, it's the complete schematic that defines level and distribution of harmonics in first place.
It's perfectly easy to build H2 dominated circuits with bipolar transistors, as it is to build H3 dominated circuits with triodes.
My critique went against the general use of the words 'tubes' and 'transistors'.
There are triodes, tetrodes, pentodes, as there are bipolar transistors and FETs (depletion and enhancement), which all differ from each other.
jauu
Calvin
@wadest
The source of a information or of knowledge is of no importance.
What counts is the correctness and trueth of a information.
The transconductance curve certainly tells something about the 'intrinsic' distortion of a part, but as Jan pointed out correctly, it's the complete schematic that defines level and distribution of harmonics in first place.
It's perfectly easy to build H2 dominated circuits with bipolar transistors, as it is to build H3 dominated circuits with triodes.
My critique went against the general use of the words 'tubes' and 'transistors'.
There are triodes, tetrodes, pentodes, as there are bipolar transistors and FETs (depletion and enhancement), which all differ from each other.
jauu
Calvin
Calvin, what about the resonance of the output transformer and the microfonics of the tubes. transistors don't have those.
Hi,
@wadest
I don´t get the point.
The use of output transformers is neither required nor restricted to tube circuits ... think of linelevel audio transformers for galvanic isolation and balancing/desymmetrizing a signal.
Think about OTL tube amps (quite popular with 6C33 tubes) like the Atma-Sphere.
Think also of certain McIntosh transistor power amps that became well known due to their useage of output transformers.
Due to the filigrane construction and parts tubes are prone to microphony, yes, but that issue may be none, as it depends only on the mounting situation.
Within a shielding case for example microphony may be no issue.
Just like tubes transistor circuits require inductors, cpacitors and resistors as surrounding parts.
Microphony may therefore also be an issue in transistor circuits, even if the transistor itself doesn´t behave microphonic.
Other sources of influence could be temperature and light (Diodes)
jauu
Calvin
@wadest
I don´t get the point.
The use of output transformers is neither required nor restricted to tube circuits ... think of linelevel audio transformers for galvanic isolation and balancing/desymmetrizing a signal.
Think about OTL tube amps (quite popular with 6C33 tubes) like the Atma-Sphere.
Think also of certain McIntosh transistor power amps that became well known due to their useage of output transformers.
Due to the filigrane construction and parts tubes are prone to microphony, yes, but that issue may be none, as it depends only on the mounting situation.
Within a shielding case for example microphony may be no issue.
Just like tubes transistor circuits require inductors, cpacitors and resistors as surrounding parts.
Microphony may therefore also be an issue in transistor circuits, even if the transistor itself doesn´t behave microphonic.
Other sources of influence could be temperature and light (Diodes)
jauu
Calvin
In his post #120 TMM asked:
If you use the term 'damping factor' in its classic definition, we have been discussing for weeks now why that is a misnomer. If you mean actual damping effect, this is why:
I am uncertain as to what you are actually referring here ....
If you use the term 'damping factor' in its classic definition, we have been discussing for weeks now why that is a misnomer. If you mean actual damping effect, this is why:
(my post #18)
I am uncertain as to what you are actually referring here ....
PS: Apology, this is a part reply to the post by OverkillAudio his post #123:
Referring to my above post and with due respect to Andrew, he inadvertently left out the main impedance in the route (circle), which is the voice coil d.c. resistance. Again not to repeat unnecessarily, past posts will show you that 'damping factor' (as per classic definition) of higher than say some 10 has negligible to zero influence.
Referring to my above post and with due respect to Andrew, he inadvertently left out the main impedance in the route (circle), which is the voice coil d.c. resistance. Again not to repeat unnecessarily, past posts will show you that 'damping factor' (as per classic definition) of higher than say some 10 has negligible to zero influence.
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As Andrew said.
Just to add: One must not confuse normal loudspeaker efficiency with how 'efficient' back-emf is translated to 'braking' undesired cone movement etc. The normally quoted efficiency concerns the efficiency with which the loudspeaker (system) 'converts' electricity to physical sound waves. The use of back emf generated by undesired cone movement (i.e. movement not caused by the signal power) is mercifully rather more efficient. It is as said previously, mainly limited by the driver voice coil d.c. resistance, but to a lesser degree by the factors mentioned by Andrew including any cross-over network dc resistance.
Trying to keep it simple, but even that is not exactly true. As undesired cone movement manifests as a.c., one must really refer to the total cicuit impedance including amplifier, cable etc. This is probably higher and complex of nature - but one thing at a time! One simplifies by starting with dc resistance; that at least denotes the lowest resistane ever present. Proper reactive analyses can become a nightmare!
So what happens immediately after the cessation of a signal is that the cone(s) 'reverberate' in a time-diminishing fashion according to their respective masses and stiffnesses of suspension plus many other influences, until stationary.
You will by now have grasped that the commonly defined definition of DF as (loudspeaker impedance)/(amplifier+cable impedance) is of little practical use. (To repeat, the denominator of this fraction rapidly becomes inconsequential related to total circuit resistance.) The exact calculation of damping/braking force is a rather complex matter because of all the rapidly changing transient phenomena involved for a (hopefully!) brief period. In practice one looks at this on an oscilloscope and can analyse it by spectrum analysis. The main thing is to get a situation of the most rapid stopping of unwanted cone movement.
Do note that damping effect (low 'generator' impedance) is always present in an amplifier. One must, kind of, look separately at the two signals (as electrical basics in fact indicate); they operate simultaneously but independently from each other.
I hope I have managed to stay simple; apology that I do not now have reading matter quotes at hand. There exist plenty on the internet, perhaps others can help. I often refer to 'E.S.P.' (Elliott Sound Products) on the 'Westhost' web. Rod Elliott is good at explaining matters simply; there are others.
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Thanks Johan,
I think I am getting more of a feel for the scale of the forces if not an exact formula or method to calculate the force.
The advice so far leads me to a couple of new questions:
If 99% of the amplifier power is wasted as heat and friction only 1 % of the energy input is emitted as sound.
What % of the 99% wasted energy is heat in the voice coil and what % is frictional losses in the spider and surround?
How would one calculate this?
Thanks again
Derek.
I think I am getting more of a feel for the scale of the forces if not an exact formula or method to calculate the force.
The advice so far leads me to a couple of new questions:
If 99% of the amplifier power is wasted as heat and friction only 1 % of the energy input is emitted as sound.
What % of the 99% wasted energy is heat in the voice coil and what % is frictional losses in the spider and surround?
How would one calculate this?
Thanks again
Derek.
"Why did you add the DC impedance of the speaker to Zo? "
Because it's in series with the motional impedance of the driver, and it dominates any real damping that occurs.
The 'idea' is that a zero amplifier output impedance will act like a brake on cone motion, but the DCR of the voice coil is in series with the current being damped.
Because it's in series with the motional impedance of the driver, and it dominates any real damping that occurs.
The 'idea' is that a zero amplifier output impedance will act like a brake on cone motion, but the DCR of the voice coil is in series with the current being damped.
Actually it is; the direction of the audio signal flow. ...Yes, no?
Then why bi-wire or bi-amp? ...Tri...
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