KatieandDad, the effect discussed here is so small that I'm ignoring it. Being able to dispense with passive crossovers is a big drawcard of going active. These threeways you are building....are they a well known documented design? Keep in mind that designing passive crossovers is by no means a trivial task. Getting them right first time would be pretty unusual. Going active means it is much easier to make changes later.
The main point of going active is to remove the crossover. You could just leave a capacitor in series with the mid and treble drivers for protection, at least during initial testing. If you want to leave them in permanently, you can either make sure they are sufficiently large to have minimal effect at the crossover frequency (might not protect the driver though), or use them as the first order of the crossover itself.
I would take them out personally, but please don't blame me if it goes wrong and you fry something.
Brian
Hey Peter,
Good to see some measurements in the midst of all this high brow speculation.
Note that the HF rolloff apears to be intrinsic in your amplifier and is in an opposite direction to any effect of inductance (inductance rise will tend to flatten that amp).
I'd note to others that these are minor response issues and I assume that there would be a tuning/refinement phase to any of these designs. At that point any fine tuning would easily correct for the trivial response effects of having or not having Zobels.
David
A few thoughts, just to 'chum the waters'.
The tweeter selected is a high quality one, and may or may not have a lower bump in the impedance, and may or may not be flatter than others that are not nearly so nice.
Another thought is that the very nice distortion figures for amplifiers typically are made looking into a resistive load. Which, is best case. Many amplifiers are not so "happy" when driving any reactance. The "zobel" network on the output of most amplifiers is to keep the amp from killing itself trying to drive a very low Z load at higher than audio frequencies. The effects of this network are not benign at all once you look at what the amp does into a reactive load. Some, of course would contend that it's not audible - a different discussion.
So, the small amplitude variation is only part of the story once one factors in the amp + cable + speaker as a complete entity.
KatieandDad, this discussion says nothing about using a passive vs. active xover. Each has different merits and different problems to solve.
The tweeter selected is a high quality one, and may or may not have a lower bump in the impedance, and may or may not be flatter than others that are not nearly so nice.
Another thought is that the very nice distortion figures for amplifiers typically are made looking into a resistive load. Which, is best case. Many amplifiers are not so "happy" when driving any reactance. The "zobel" network on the output of most amplifiers is to keep the amp from killing itself trying to drive a very low Z load at higher than audio frequencies. The effects of this network are not benign at all once you look at what the amp does into a reactive load. Some, of course would contend that it's not audible - a different discussion.
So, the small amplitude variation is only part of the story once one factors in the amp + cable + speaker as a complete entity.
KatieandDad, this discussion says nothing about using a passive vs. active xover. Each has different merits and different problems to solve.
They are Wilmslow Audio Prestige Platinums, supplied as a kit complete with three way crossovers. Each driver has its own crossover.
Leaving a cap in series with a tweeter is a good idea in most cases because the coil reacts to very small amounts of DC, and even small clipping peaks can destroy the tweeter. The cap should be large enough that it does not cause significant effects at the crossover frequency. Normally I use a very oversized cap, for example for a XO point of 1.6KHz I am using 230uF (220uF||10uF film).
I'm not sure this is true as I have seen measurements of amps into Inductive loads where they are quite happy to drive them. (Capacitive loads are another matter). The inductive rise of a tweeter is less than first order so the phase angle is minimal. Don't forget as well that many amps have an inductor on the output for stability reasons. Leaving your tweeter a little inductive = more stability and a guarantee of reduced current requirements at highest frequencies.
Like many audiophile notions, this sounds like "the impedance is flatter so it must be better". If nobody has any measurements of higher distortion (or blind test results) then these have to fall into the speculation and hearsay column.
David
That is not at all what is happening.
One does have to consider what current is traveling down the wire,
dave
I know what current is, however it seems you're talking in riddles. My response was an answer to your one-line answers. 'Current'ly this 'lead's nowhere…
As I see it, you compensate the lack of upper bass/lower midrange with higher impedance of the cable. Get over it and use a proper circuit instead….
As I see it, you compensate the lack of upper bass/lower midrange with higher impedance of the cable. Get over it and use a proper circuit instead….
I use pairs of 6 gauge single wires, lightly twisted together, normally 10' or less long. This makes a very worthwhile, low cost improvement
compared to smaller wire. You can get this wire cheaply by the foot at a local electrical contractor. Ring lugs are necessary most of the time
with larger wire. There are usually two kinds of wire like this, with different stranding, you should get the kind with more strands.
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The 6ga is fairly inductive, I am led to believe. The twist adds capacitance, this allegedly "compensates" for the inductance, they say.
I say nothing works out quite like one would expect or prefer.
I think at this point in time every possible variation in speaker cable has been tried - are there any that have not?
_-_-
Thin wire often sounds "good" on tweeters. Why? No idea. Dunno.
sometimes thick wire sounds good. Why? Dunno.
They never sound the same it seems. Why? Dunno.
I say nothing works out quite like one would expect or prefer.
I think at this point in time every possible variation in speaker cable has been tried - are there any that have not?
_-_-
Thin wire often sounds "good" on tweeters. Why? No idea. Dunno.
sometimes thick wire sounds good. Why? Dunno.
They never sound the same it seems. Why? Dunno.
For single conductors:
The inductance of 20 gauge is 400 nH/foot, and the inductance of 6 gauge is 302 nH/foot.
The resistance of 20 gauge is 10.15 mOhm/foot, and the resistance of 6 gauge is 0.395 mOhm/foot.
There's no inductive penalty for larger wire, in fact it's somewhat lower.
The 6 gauge wire is a factor of over 25 lower in DC resistance. This is significant.
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