I saw the JBL horn tweeter design, for their high end model they never use series R to connect to their compression driver, instead, using a R to parallel the driver.
Do you know the benefit of Shunt R vs. the Series R ? Purity, dynamic or something else.
I seldom see the use of Shunt R to attenuate the Tweeter level for dome type tweeter, most design use series R. I am just thinking that the Shunt R for tweeter attenuation would be much better in term of transient response, sound purity etc.
What do you think if I modify my Proac 2.5 tweeter section by replacing the series R with Shunt R ? And how do I figure out the right value of Shunt R ?
Regards,
Eric
Do you know the benefit of Shunt R vs. the Series R ? Purity, dynamic or something else.
I seldom see the use of Shunt R to attenuate the Tweeter level for dome type tweeter, most design use series R. I am just thinking that the Shunt R for tweeter attenuation would be much better in term of transient response, sound purity etc.
What do you think if I modify my Proac 2.5 tweeter section by replacing the series R with Shunt R ? And how do I figure out the right value of Shunt R ?
Regards,
Eric
Eric,
seriously, is there something wrong with how high
frequencies sound to you on your Proac 2.5?
seriously, is there something wrong with how high
frequencies sound to you on your Proac 2.5?
If the crossover is already designed and has a series resistor, you cannot do the change you propose without upsetting the crossover frequency.
series resistor attenuates the SPL
and it lowers xo point some, relatively
attenuation + the raised impedance could result in even lower 'xo point'
which might mostly be noticed as phase change, or ressonance
parallel resistor on a compression driver might also be there to deal with the problematic impedance ressonances this type of tweeter has (causes trouble to the crossover function)
in general, I prefer small series attenuation only
this may have resulted in the introduction of ScanSpeak 4ohm tweeters, a long time ago
that said, the common practice to do tweeter attenuation is by series and parallel resistors
this is to minimise impedance changes
and the only way to avoid influences on crossover function
and it lowers xo point some, relatively
attenuation + the raised impedance could result in even lower 'xo point'
which might mostly be noticed as phase change, or ressonance
parallel resistor on a compression driver might also be there to deal with the problematic impedance ressonances this type of tweeter has (causes trouble to the crossover function)
in general, I prefer small series attenuation only
this may have resulted in the introduction of ScanSpeak 4ohm tweeters, a long time ago
that said, the common practice to do tweeter attenuation is by series and parallel resistors
this is to minimise impedance changes
and the only way to avoid influences on crossover function
The shunt resistor is there for burning the power.
Its role is to subtract power from the driver, which is too sensitive.
Its role is to subtract power from the driver, which is too sensitive.
it is true that a 1ohm series resistor attenuates more effectively when a parallel resitor is added
to achieve the same attenuation with a series resistor only, it would need to be bigger
to achieve the same attenuation with a series resistor only, it would need to be bigger
and so it is, unfortunately
maybe you can remove the series resistor if you also make the tweeter cap slightly bigger ... but, it is very tricky
you could try an experiment, and make the series resistor smaller, simply by paralleling it with another resistor of same value
meaning, placing one on top of the other
and you are 100% certain noone else have messed with your speaker before this, changing caps etc ?
maybe someone else could have changed tweeter phase, accidentally, or intentionally ?
btw ... is it original Proac, or a clone ?
I'm not sure I see the connection between what's been done with a compression driver on a horn, and what's appropriate for a dome tweeter. Unless I'm missing something.
In a usual voltage driven amplifier/speaker system a resistor
parallel to the load changes nothing:
It is just lowering the load impedance, thus increasing
the current but the voltage at the tweeter's terminals
will stay the same if connected directly to the amp.
A resistor in parallel may smoothen the impedance-
peak at the resonance frequency of the tweeter and also
the impedance rise caused by the voice coil inductance.
But usually special RLC-members (resonance compensation)
and RC-members (Lvc compensation) are used for that
specifically.
Together with a series resistor, a parallel resistor can reduce
the level significantly (... forms an L-Pad) and the level
reduction may be more constant with frequency,
because of the mentioned smoothening effect on the tweeter's
impedance.
Hower this is not always desired, because sometimes
tweeters need a voltage rising with frequency.
If e.g. a passive first order highpass is applied to the tweeter
(e.g. just a series capacitor) with lower cutoff far above the
tweeter's resonance, a parallel resistor might contribute to
make (more) use of the tweeter's inherent damping due to
back EMF (Electro Motoric Force), which does not contribute
that much otherwise in this case, because the impedance of
the capacitor is high below the cutoff frequency.
A (rather low valued) parallel resistor will thus contribute
to the tweeter's damping at resonance ( as a kind of substitute
for the low impedance of the amp, which is not "seen anymore"
at the tweeters terminals at lower frequencies , due to the capacitor).
But if level reduction is desired, one won't get around a series
resistor first.
Kind Regards
parallel to the load changes nothing:
It is just lowering the load impedance, thus increasing
the current but the voltage at the tweeter's terminals
will stay the same if connected directly to the amp.
A resistor in parallel may smoothen the impedance-
peak at the resonance frequency of the tweeter and also
the impedance rise caused by the voice coil inductance.
But usually special RLC-members (resonance compensation)
and RC-members (Lvc compensation) are used for that
specifically.
Together with a series resistor, a parallel resistor can reduce
the level significantly (... forms an L-Pad) and the level
reduction may be more constant with frequency,
because of the mentioned smoothening effect on the tweeter's
impedance.
Hower this is not always desired, because sometimes
tweeters need a voltage rising with frequency.
If e.g. a passive first order highpass is applied to the tweeter
(e.g. just a series capacitor) with lower cutoff far above the
tweeter's resonance, a parallel resistor might contribute to
make (more) use of the tweeter's inherent damping due to
back EMF (Electro Motoric Force), which does not contribute
that much otherwise in this case, because the impedance of
the capacitor is high below the cutoff frequency.
A (rather low valued) parallel resistor will thus contribute
to the tweeter's damping at resonance ( as a kind of substitute
for the low impedance of the amp, which is not "seen anymore"
at the tweeters terminals at lower frequencies , due to the capacitor).
But if level reduction is desired, one won't get around a series
resistor first.
Kind Regards
Last edited:
That's more like it, clone you say. Would you post
a schematic, maybe then can be helped further.
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