Hard to say without a measurement, and that would not be of much use anyway. You are loading the crossover at the expense of the tweeter, where you end up may have little to do with flat impedance. Trying for flat at first is a reasonable start as a first guess.
You are trading off many variables in your experiments, I suspect it's just better to do trial and error.
enjoy
jn
That’s exactly why I asked Joe the question. If you have current thru an L you have a field and that’s stored energy.
It's about time you went active Bob, then you'd be able to fiddle about with FR and phase to your heart's content
Thanks Pavel,
that makes sense because i’m Having a hard time deciding if this perceived focus improvement actually involves accuracy......from what you just said probably not. Still gonna try a couple of lower value caps just to get a better handle on it.
Yes but shouldn’t one crawl a little while before walking.....plus i’m Thinking hybrid active/passive!
It is quite trivial and common practice to measure inductance using an AC voltmeter with any AC source, does not matter voltage or current, please consult your EE friends.
There's something to be said for that, but there's also something to be said for passive systems have a greater entanglement of parameters. Active makes it a lot easier to be much more direct in action. DSP takes it another step.
The problem is in general especially the inductance of a speaker motor is level dependent, you really need to have a grasp of everything that is going on to make sense of the measurements.
The toughy part is communicating circuit behavior to a virgin (of Kirchoff's law).
Bob, altering the load on the crossover HPF (tweeter or tweeter+zobel) will alter the effective rollover/crossover frequency, so adding a zobel across the tweeter will also require adjustment of HPF values. Putting the zobel across the crossover input should not appreciably alter tweeter FR but it does damp HF energy and eliminate energy reflections back to the amplifier. As suggested by Pavel this is in effect a lower impedance HF load than the non zobeled load and can be expected to cause increased distortion at the amplifier output terminals BUT this comparing apples to oranges.......ie comparing amplifier output terminal distortion with higher impedance reactive load to lower impedance resistive load and as such is not the same. IME such zobels across drivers or across loudspeaker inputs does cause reduction in highs and ultra highs, BUT these are false highs due to distortion mechanisms. Your finding of subjectively increased mids distortion with zobel across crossover input may be a result of unmasking due to cleaner/clearer highs and infact showing up your cable/amp as not as good as you thought. If you are running fig8 cable you can try connecting 100R or so across each end, IME this works very well in reducing/eliminating distortions due to reflections/RF pickup.
Do you mean lower impedance load or lower resistance load......totally not the same thing. I have also found Class AB amplifier to run cooler and go louder with compensated (resistive) load compared to typical rising reactive impedance.
This has been thrashed to death here. The amplifier simply supplies the current needed to ensure that the output voltage meets the demands of the feedback so that V non-inverting = V inverting at the input diff stage.
There is a misconception that unless the phase angle between the voltage and current is low, or unless the overall amplifier current remains ‘flat’ across frequency, more distortion will result.
I would argue distortion is more likely to go up with the EQ network since the amplifier must now provide power into the speaker proper and the EQ network.
Agreed.
Bingo!
Alas, it is actually the high source impedance and hence the current is not reactive as it is in series. Note the current phase angle becomes zero. The fact that feedback is the cause of the high series Z is of a secondary issue, the how is not as important as the fact, the source A.
I am not seeking an argument, just trying to focus on the issue.
You say that the voltage is determined by the reactive load. That may be the straight talk in an EE book sense, but consider perhaps a fuller understanding of what is going on. We know the current is constant and will be maintained. Let us consider that the current is also flowing through the Re of the voice coil, say 6 Ohm for an 8 Ohm driver. This will generate heat. But let is say that the total impedance at our test frequency is 18 Ohm. That means that 12 Ohm is not dissipating heat. This little fact has been confirmed. But if connected to a voltage source, only 1/3rd of the current will pass through the voice coil.
But of course, we are discussing a current source, hence the full current will be maintained. But the voltage will increase because the 12 Ohm part of the impedance is, in fact, a voltage source that is opposing the current in series with Re. Because the amplifier is a current source, the full voltage generation will be seen caused by back-EMF (force+voltage). This 12 Ohm is what I call the back-EMF impedance. It is a voltage source (something that others have recognised). Most likely inductive back-EMF (Faraday's Law of Induction) that creates that voltage, but only with a current source.
We, of course, tend to use voltage sources, hence that voltage will be generated, but the 12 Ohm impedance is as a result of that back-EMF. This will se a reduction in current. It will also allow the current of the amplifier to change and deviate from zero degrees.
Even calling it back-EMF indicates this is happening. The back means backward and F in EMF stands for force, and that means a voltage. A friend of mine with a mathematical background suggested "anti-voltage" as a description. He certainly had no problem understanding the above.
Now for your thoughts, respectfully.
Joe R.
PS: Can a load be called "reactive" when driven by a current source? Or is there no such thing as a reactive load, only reactive current? The potential is there, but passive components don't know themselves?
PPS: The rest of your post is fine with me. In fact, it was all good.
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Reading KSTR, I can see that he fully understands the mechanisms involved. Reading yours, I'm 'confused'.
May be it shouldn't be about understanding the above, but understanding beyond the above?
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