Home Brew Al K Universal crossovers.

Based on di/dt you should have severe phase lag , not a total cancelling??
 
laatsch55 said:
So , how they are wound and what they are wound with is a science unto itself ??
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There are a lot of ways to make an inductor but the basics as I understand them are insulated wire wrapped around a core - sometimes the core is air but more commonly the core is soft annealed iron- the wire typically is the same as what is used in transformers. There are a number of variables that change the characteristics of an inductor but there are formulas available to calculate the characteristics of a particular inductor in a circuit. It does get a bit complex tho... I'll defer to the expert.

That is why speaker performance is so difficult to define as the inductance and other parameters contribute to the final product.
 
laatsch55 said:
So , how they are wound and what they are wound with is a science unto itself ??
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Yes, you could say that. Winding in a coil allows for a compact way to get a lot of wire in a small volume. Also creates a lot of ampere-turns (i.e. magnetic flux) by looping the wire back on itself in this coil structure.

Maybe an (pretty close) analogy will help.

Imagine a mile long 6 inch diameter water pipe with water flowing through it at a constant and very rapid rate (v). Imagine the mass of that mile long length of water (m) flowing at that very rapid rate, pretty immense. Imagine the kinetic energy (1/2 x m x v^2) trapped in that mass of water flowing at that very rapid rate. Now imagine that you had a magic valve that could instantaneously shut off that flow. Likely either the pipe would burst or the valve would blow out. That kinetic energy example is analogous to the energy stored in an inductor.

Imagine that same pipe with that flow and you had to instantaneously double the flow rate. It would take a huge amount of energy to do that. However if you were to gradually increase the flow rate and then gradually decrease the flow rate it would be much easier to do without expending much energy at all (the low frequency case). The more you increased the rate of increase followed by an equal decrease, the more energy you would be required to expend (the higher frequency case).

That same mile long pipe could be wound in a much more compact length and width by coiling it up in a circular coil. You will see that most of the gross dynamics of the example above do not change much but it starts looking more like the inductors in your crossover in that type of example.

Any better help in your understanding?
 
Joe , I have shut valves on a mile long moving column of water....depending on the rating of your stuff it usually blowed the fuck up.....done it many times....
 
Not really Joe because water does not create magnetic fields that alter it's behavior.....trying to wrap head around this....
 
Ok Joe, the high frequendies are still there, just not in phase and at a much reduced level??
 
laatsch55 said:
Ok Joe, the high frequendies are still there, just not in phase and at a much reduced level??
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As with any single pole low pass filter Lee, the high frequencies are always still there, just severely attenuated (at 6dB/octave) and approaching 90 degrees lagging to the filter input signal at any frequency higher than the Fc (critical frequency) of the filter.
 
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Ok, now that makes sense....it was the idea that they no longer existed that was cock locking me...
 
Does it take significantly more energy to amplify and transmit a 20KHZ signal compared to a 20HZ signal....
 
laatsch55 said:
Not really Joe because water does not create magnetic fields that alter it's behavior.....trying to wrap head around this....
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Hi Lee
In the water case, the moving mass of the water is storing the energy. In the inductor case, the current through the wire generates a magnetic field surrounding the wire proportional to the current. That magnetic field stores energy as the current is increasing and gives it back when the current decreases. Capacitors also store energy but they do it with an electric field generated between the adjacent plates rather than a magnetic field.

Capacitors and inductors are quite analogous in behavior to each other at a high level, the first uses electric field and the latter magnetic field to store energy.

E= 0.5*C*V^2 for the capacitor
E= 0.5*L*I^2 for the inductor

See the similarity?
 
laatsch55 said:
Does it take significantly more energy to amplify and transmit a 20KHZ signal compared to a 20HZ signal....
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At a high level, if you are driving into a purely resistive load and your transistors etc, are perfect devices then the answer is no. Loads are rarely if ever purely resistive and components are rarely perfect devices.

If the load looks like a resistor in parallel with a capacitor to ground then you will expend more energy driving into this load at higher frequencies (capacitive load).
If the load looks like a resistor in series with an inductor to ground then you will expend more energy driving into this load a lower frequencies (inductive load).

Generally speaking, the internal circuits of the amplifier appear capacitive in nature so the dissipation internal to the amp at higher frequencies is also higher. Sort of in the same way your truck engine has more frictional losses at higher RPMs and deliverable output horsepower and torque roll off.

Hope this helps and not hurts your understanding.

PS: I would not say significantly, but it is more.
 
Gepetto said:
At a high level, if you are driving into a purely resistive load and your transistors etc, are perfect devices then the answer is no. Loads are rarely if ever purely resistive and components are rarely perfect devices.

If the load looks like a resistor in parallel with a capacitor to ground then you will expend more energy driving into this load at higher frequencies (capacitive load).
If the load looks like a resistor in series with an inductor to ground then you will expend more energy driving into this load a lower frequencies (inductive load).

Generally speaking, the internal circuits of the amplifier appear capacitive in nature so the dissipation internal to the amp at higher frequencies is also higher. Sort of in the same way your truck engine has more frictional losses at higher RPMs and deliverable output horsepower and torque roll off.

Hope this helps and not hurts your understanding.

PS: I would not say significantly, but it is more.
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Yes it does Joe...hence higher distortion at higher frequencies......
 
Gepetto said:
The value of your inductor, like 1.1 milli-henry, that is inductance
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Yes I do see a similarity, the square of the product, I understand the relationship but lack the prerequiste understanding for it to make sense in the context we are talking about it...
 
laatsch55 said:
Yes it does Joe...hence higher distortion at higher frequencies......
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That is one component of higher distortion at higher frequencies, the bigger component of higher distortion is running out of loop gain at higher frequencies. That tends to limit the achievable power bandwidth any amplifier.

High loop gain can compensate for distortion in the signal using the global loop negative feedback. If the loop gain is lower, the negative feedback is less effective in correcting for small errors.

If your loop gain is 100,000V/V at 10 Hz, it could be 10,000 at 100 Hz, 1000 at 1000 Hz, 100 at 10KHz 10 at 100 KHz. You see the trend, much less corrective gain at your disposal at higher frequencies. That rolloff in gain is by design to ensure stability once the poles and zeroes caused by real world transistors start to come into play.
 
How does negative feedback correct for errors and why does it have to be "negative" feedback?? And what "errors"?
 
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