tonyee, sorry no time for elaborate reply but you've got it quite well! Few quickies: Dynamic drivers have this stuff, coil and magnet. Mass is there, except it's cancelled by spring at resonance! for both bass woofers and treble tweeters. So basically a driver has two operating modes within it's bandwidth, with and without mass. Impedance peak at drivers resonance is pure motional impedance, solely due to current backEMF generates, and basically the electrical damping. BackEMF is voltage, and would always be there, regardless of amp, it's generated when ever the transducer has velocity. Thing is, only current makes force in the driver motor, voltage could be anything and the driver wouldn't move unless current flows. Basicaly any current means acoustic output, which means any anomalies in the current like driver otor magnetic hysteresis and other phenomena turn into distortion in current, the more the smaller the circuit impedance is.
Now that the basic idea seems to be quite clear to you, you are able to reason further, all mysteries ready to be cracked 🙂 like about the heat: when voice coil heats up it's Re goes up. With a constant voltage amp current in circuit would reduce with increasing Re as per abstract pointed out, which compresses acoustic output, and basically protects the driver some. With current amp you could maintain current and acoustic output regardless of heat increasing copper re and the voice coil would burn more easily, a thermal runaway kinda.
I bet you'll find this article interesting, same thing accompanied with simple math. I like to suggest readers to ignore colorful language considering war between voltage and current amplifier, just concentrate on how the driver works 🙂
https://www.edn.com/loudspeaker-operation-the-superiority-of-current-drive-over-voltage-drive/
I also suggest to find out what "jump resonance" is, if further interested about this. And to think about how loudspeaker box alignments relate to all this, what damping and Q actually means here and so on. Furher, how to interpret driver impedance measurements to spot issues with a speaker, what this all means for active and passive speaker alleged sound differences, and in general, how to make best possible sounding systems includidng amps and speakers. It's very interesting to really imagine and try to deeply understand how a transducer works I think 🙂
ps. I don't know much what actually happens inside an amplifier, how and where current is going, I just use basic circuit analysis replacing actual amp with ideal voltage or current source, ornmore rralistically just a voltage amp with series resistor representing output impedance.
Now that the basic idea seems to be quite clear to you, you are able to reason further, all mysteries ready to be cracked 🙂 like about the heat: when voice coil heats up it's Re goes up. With a constant voltage amp current in circuit would reduce with increasing Re as per abstract pointed out, which compresses acoustic output, and basically protects the driver some. With current amp you could maintain current and acoustic output regardless of heat increasing copper re and the voice coil would burn more easily, a thermal runaway kinda.
I bet you'll find this article interesting, same thing accompanied with simple math. I like to suggest readers to ignore colorful language considering war between voltage and current amplifier, just concentrate on how the driver works 🙂
https://www.edn.com/loudspeaker-operation-the-superiority-of-current-drive-over-voltage-drive/
I also suggest to find out what "jump resonance" is, if further interested about this. And to think about how loudspeaker box alignments relate to all this, what damping and Q actually means here and so on. Furher, how to interpret driver impedance measurements to spot issues with a speaker, what this all means for active and passive speaker alleged sound differences, and in general, how to make best possible sounding systems includidng amps and speakers. It's very interesting to really imagine and try to deeply understand how a transducer works I think 🙂
ps. I don't know much what actually happens inside an amplifier, how and where current is going, I just use basic circuit analysis replacing actual amp with ideal voltage or current source, ornmore rralistically just a voltage amp with series resistor representing output impedance.
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Current amp is basically all solid state amplifiers, tube are limited in amps but they have plenty of voltage drive.
The biggest factor of a driver at Lower frequency is the air compression of the box and yes all the basket and rubber surround , the surround is what generates 3rd harmonics , 2nd by the voice coil and basket
I have some experience with that, but for dynamics it is the voice coil and copper shorting ring which helps
The biggest factor of a driver at Lower frequency is the air compression of the box and yes all the basket and rubber surround , the surround is what generates 3rd harmonics , 2nd by the voice coil and basket
I have some experience with that, but for dynamics it is the voice coil and copper shorting ring which helps
Just note that there is a formal definition in electrical engineering for source types, which can be extended to "amp" types, since an amp is basically a source.
Current Source or Current Amp is the device that fix a certain current (so varying the voltage) to the load regardless of the load impedance.
Voltage Source or Voltage Amp is the device that fix a certain voltage (so varying the current) to the load regardless of the load impedance.
Most solid state amps (class AB, class D, H, G etc) are Voltage Amps.
And it needs to be this way.
Simple test if you have any passive woofer or subwoofer
1) With the speaker terminals disconnected, hit the cone with your fingers (gently) and hear how it resonate and takes sometime to stop (underdamped response). This is not desirable. The cone is not being controlled by electrical forces since circuit is opened (high impedance).
2) Now, short the speaker terminals and hit your finger again. It will not resonate, cause the electromagnetic forces will not allow the cone to move - This is electrical dampening, where the speaker is under control.
Same will happen if you connect the speaker to a solid state amp and turn it on - Amp will behave like a short to the speaker. A voltage source has very low impedance, ideally zero. The current generated by the speaker when you hit the cone will be absorbed by the amplifier - if there is no signal at the amp input, the amp will force (fix) no signal in the output (zero volt) by flowing necessary current to make that happen. It's the definition of a Voltage Source.
Current Source or Current Amp is the device that fix a certain current (so varying the voltage) to the load regardless of the load impedance.
Voltage Source or Voltage Amp is the device that fix a certain voltage (so varying the current) to the load regardless of the load impedance.
Most solid state amps (class AB, class D, H, G etc) are Voltage Amps.
And it needs to be this way.
Simple test if you have any passive woofer or subwoofer
1) With the speaker terminals disconnected, hit the cone with your fingers (gently) and hear how it resonate and takes sometime to stop (underdamped response). This is not desirable. The cone is not being controlled by electrical forces since circuit is opened (high impedance).
2) Now, short the speaker terminals and hit your finger again. It will not resonate, cause the electromagnetic forces will not allow the cone to move - This is electrical dampening, where the speaker is under control.
Same will happen if you connect the speaker to a solid state amp and turn it on - Amp will behave like a short to the speaker. A voltage source has very low impedance, ideally zero. The current generated by the speaker when you hit the cone will be absorbed by the amplifier - if there is no signal at the amp input, the amp will force (fix) no signal in the output (zero volt) by flowing necessary current to make that happen. It's the definition of a Voltage Source.
Thanks for the clarification. It does sound deeper when I short the terminals, when they are not shorted the magnetic flux kinda stops the motion and it is higher pitched and sounds more resonant. Yes , with my amp on it has the same effect.
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It's the opposite, right? When terminals are shorted the magnetic flux and the coil (thus electromagnetic) stop the motion and force the cone to not resonate.
Hmm.. .when the terminals of the speaker are shorted then there is no impedance so the current can flow and the back EMF is cancelled?
shorted terninals make electrical circuit for the backEMF current and electrical damping happens, the driver dampens itself, controls itself. With open circuit this doesn't happen. Or, if say very long cable that the series impedance gets significant and electrical impedance is reduced enough there starts to be audible difference. Or with amp output impedamce, or aky impedance network between amp and a driver.
Yeah one can make this finger drumming test without amplifier, or with amp. Unhook your speaker and drum the woofer, it sounds literally like a drum due to very little damping. Short speaker terminals with piece of wire or with a screw driver, you can do this with one hand while drumming with the other. Very easy to detect significanse of electrical damping doing it like this.
Exact same thing happens if normal amplifier is connected, unhook one speaker wire so you can make or break the circuit with one hand.
Conclusion from such test is damping factor of a screw driver is high 🙂
With a transformer coupled output the voltage get through the OT and in the earth ground , in ss there is I think in many amps a path to ground too but without much inductance
In tube amp:
I bet it makes an audible difference if you disconnect the ground of the output transformer terminal (float output)because there is only the amp to damp the generated extra signal from speaker imperfection, air damping / stray / abrupt phase changes emf
In tube amp:
I bet it makes an audible difference if you disconnect the ground of the output transformer terminal (float output)because there is only the amp to damp the generated extra signal from speaker imperfection, air damping / stray / abrupt phase changes emf
Another way to understand the electrical damping, is to look at the speaker electrical equivalent model.
I modeled the woofer I use in my speakers as it would be installed in a sealed box just for simplicity (port speakers need extra components in the model).
This is a real model considering the woofer plus the enclosure.
When the cone is moving, the energy is stored mainly in the L12 and C11.
When there is no or low damping from the amplifier, the speaker terminals see more like an open circuit.
The energy stored in L12 and C11 will be dissipated in R31 (39ohms). This resistance represents the mechanical/acoustic dissipation.
But if the amp has a very low impedance (high damp factor), the speaker coil resistance (R20) will be shorted to the ground and it has a much lower value (3.7ohms) so it can dissipate very quickly the energy stored in L12 and C11, which represents stopping the cone from moving.
R20 will be in parallel with the RLC circuit.
L6 has a low value and only plays a role in higher frequencies (>300Hz in this case), which, in general, don't reach the woofer, since the crossover filters them. This woofer is more like a subwoofer.
Equivalent 8" woofer sealed box
Impedance curve - very typical
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Yeah, and at high frequencies, C11 goes short, and L6 becomes significant. Notice also that the intuitive concept of a braking force "opposing" the cone velocity (and reducing the Q of resonances) becomes null and void. Cone velocity is reduced, and there's a significant phase lag.
The back noise could make amplifiers ring , but not oscillate as long as the feedback is low pass properly and has enough stability margin
I advance a supposition that we can easily hear that ringing and that can solely almost determine how the amplifier will behave with a music signal, sent a sine/square wave and abruptly cut the signal , everything you hear is what will pollute the music at a lesser extent
Also the start impulse noise is a good indicator and at which power it will become problematic
You can hear it back in the tweeter when you cut off a 20hz strong signal
I advance a supposition that we can easily hear that ringing and that can solely almost determine how the amplifier will behave with a music signal, sent a sine/square wave and abruptly cut the signal , everything you hear is what will pollute the music at a lesser extent
Also the start impulse noise is a good indicator and at which power it will become problematic
You can hear it back in the tweeter when you cut off a 20hz strong signal
Production and reproduction is different thing. In sound production you can add distortion as you want. But not in reproduction. Did you judge your recording quality with TV sound system?
You keep repeating this lie over and over bimo. Who are you to tell people how they should listen to their audio system?
If someone adds 1% distortion, and if we use Fuzzy Logic type thinking, then maybe their system has 99% membership in the set of things comprising "reproduction," and 1% membership is the set of things comprising "production." Since most speakers are likely to have, say, maybe 1% distortion (or more) under some conditions, then the choice to use those speakers instead of large panel electrostatics is already a choice for partial membership in the set of things "production."
Choice is mostly dictated by wallet. Large electrostatic loudspeakers are expensive.
There is also that interesting experience that orders of magnitude higher distortion from the loudspeakers doesn’t mask entirely, very small differences in reproduction of other components in the audio chain. It is the same, from the opposite side, with turntable and vinyl as input.
Sure, and maybe WAF too?
However, the real underlying point was that no reproduction system is perfect. Also, I'm not so sure that the quest for perfection is only or even primarily a matter of nonlinear distortion and noise floor. I mean, once those things get good enough then they may be at a level similar to other remaining non-idealities which are more difficult to measure (in a meaningful way).
That statement follow basic logic using the definitions of the included words (production and reproduction). The gist is that by reproduction, we mean a non altered, true copy, of a production. So hence, it the can't be a lie. If the production is altered, it needs to be called Enhanced, Altered or Distorted Re-issue if it was on purpose. If not on purpose it would be just failed or bad reproduction.
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Here’s an old paper that adds credence to the idea that higher order harmonics are bad and it is actually the linearity at low levels that matters most. It also talks about the GedLee metric. We can do this now using tools like REW. Why aren’t we doing it? @AKSA