With the 3.3uF cap in parallel it seems the signal going through it never gets to the tweeter. If so would a low cost cap be as effective as a Mundorf Supreme?
Mundorf is just an expensive polypropoline capacitor.
Any make of the same specification will perform the same.
Don't fall into the money suckers trap.
Any make of the same specification will perform the same.
Don't fall into the money suckers trap.
Thanks for the reply but is it true that the signal, going through it, never gets to the tweeter?
the cap is to force the filter to a resistive load as the tweeter's inductance has an increasing impedance with freq
That series R and C is called a Zobel.
Shunt elements have just as much of a circuit function as series elements.
It is correct that some of the signal current is diverted through the Zobel network.
But that is the intention, in order to flatten the impedance of the driver.
Any resistor in a crossover network dissipates signal power.
Shunt elements have just as much of a circuit function as series elements.
It is correct that some of the signal current is diverted through the Zobel network.
But that is the intention, in order to flatten the impedance of the driver.
Any resistor in a crossover network dissipates signal power.
It could also be utilized as a drooping contour circuit to damp a rising response in a tweeter and not be meant for impedance compensation at all. It will provide a droop in impedance above the cap's Fc as well.
I've done this quite a few times on tweeters with a 2.5uF and 3-4 ohm resistor. It flattens the top octave rise.
Any poly cap will suit this job well. It's not that the freq range in query is never presented to the tweeter. It offers the range a different amount of electrical damping than below it.
I've done this quite a few times on tweeters with a 2.5uF and 3-4 ohm resistor. It flattens the top octave rise.
Any poly cap will suit this job well. It's not that the freq range in query is never presented to the tweeter. It offers the range a different amount of electrical damping than below it.
Nothing sinister or unexpected. There are just two reactive impedances in a configuration that supports resonance. It is one way that the capacitor current could indeed pass through the tweeter rather than the simpler view that it bypasses it.
Look at it this way.
1) IF you only had the tweeter there, fed from a voltage source (99% of amps out there), and then added the R2 C3 Zobel network in parallel, sound would not change, tweeter would "notice" nothing.
Amp will be heavier loaded, but we don´t hear amps directly.
Current through Zobel will not pass through tweeter nor affect it in any way.
2) BUT the full circuit is more complex, current through Zobel will come from a not zero impedance source so will affect voltage present across Tweeter terminals, big time, so it WILL affect what you hear.
That said, any competent (hint: proper capacitance) capacitor will work fine, no need for fairy dust.
Capacitor ESR IS a measurable physical parameter and will affect sound, but typical variations will be swamped by highish R2 value, so it becomes even less critical, again no need for a NASA spec part.
1) IF you only had the tweeter there, fed from a voltage source (99% of amps out there), and then added the R2 C3 Zobel network in parallel, sound would not change, tweeter would "notice" nothing.
Amp will be heavier loaded, but we don´t hear amps directly.
Current through Zobel will not pass through tweeter nor affect it in any way.
2) BUT the full circuit is more complex, current through Zobel will come from a not zero impedance source so will affect voltage present across Tweeter terminals, big time, so it WILL affect what you hear.
That said, any competent (hint: proper capacitance) capacitor will work fine, no need for fairy dust.
Capacitor ESR IS a measurable physical parameter and will affect sound, but typical variations will be swamped by highish R2 value, so it becomes even less critical, again no need for a NASA spec part.
Correct, without an upstream voltage divider this circuit will not affect the sound whatsoever. Since all tweeters should have this highpass/voltage divider in application it will affect the sound.
The "quality" of the capacitor IS as important as one in series. If you replace it with back-to-back diodes it will greatly distort the signal, just like (though not quite in the same way) it would if the diodes were in series with the tweeter.
That said, IMHO you're unlikely to hear the difference between an expensive "audiophile" capacitor and an equivalent one from Mouser or Digikey. What's more important is the capacitance being within a close tolerance, close to the stated value, and even more important, the two capacitors (and every crossover component) in that position going into the stereo pair of speakers should be as close as possible to the same value. A capacitance meter (or even a DMM that has a capacitance feature) will do for this. You could get 5 or 10 capacitors of that value, measure them, and pick the two that are closest in value. Or, what I would do for my own use (some people might object to this in production) is add one or more smaller capacitors in parallel to the cap to bring it up to the needed value.
I decided to use Mundorf Mcap Supreme EVO aluminum oil caps and Mills MRA-12 resistors for the tweeter filter. And Jantzen Superior Z 5.6uF caps and Mills MRA-12 resistors for the mid. I llke the sound improvement but the upper most piano notes are to predominate so I changed the series R56 to 8R45. That made an improvement but I will be trying a few other values to tweak the sound.
As you'd expect..
I have had some fine results with electrolytic capacitors on tweeters. What is important is your acoustic conditions and your crossover values.. also not ignoring parasitic resistances etc.
I have had some fine results with electrolytic capacitors on tweeters. What is important is your acoustic conditions and your crossover values.. also not ignoring parasitic resistances etc.
The outboard XO is making the speakers sound very good except for the overly predominate upper piano notes. That frequency range is about 2000 to 2500hz and the upper XO fc is 3000hz so I think a resistor in the mid range filter might be appropriate. All thoughts will be appreciated.
Henry,
The upper octave of a grand piano ranges from C7 at 2093Hz to C8 at 4186Hz, which also is typically the range of greatest hearing sensitivity. The harmonic level relative to the fundamental note actually decreases for the upper octave of the piano, accentuating the "clinky" and overly loud sound of those upper notes.
A really sensitive musician's playing can compensate for the tonal and level changes, but most do not, and may even hit those notes harder because they sound less "rich" to them than lower notes which have harmonics that extend just as high.
Setting crossover levels based on the sound of the upper piano notes would not be advisable- it will reduce overall clarity of the piano and anything else played through the speakers.
Art
I based the 2000 to 2500 range on a tune on a Keith Garret CD. The tune doesn't have any of the clinky keys in the top octave. So, since my XO upper Fc is 3,000 I thought I could try different resistors in the mid range filter. And I also disconnected the woofer and tweeter and the troublesome notes are clearly going through the mid range filter.