I have a couple questions about the phase alignment as I think it is pretty important, and I want to get it right.
imagine 2 speakers, a tweeter and a woofer crossed over at 1.5khz.
If I use a zobel on the woofer to counteract the high frequency impedance rise from the voice coil inductance and compensate the tweeters impedance peak at fs, so that both speakers have a resistive input impedance for a few octaves on both sides of the crossover frequency, will their cones move in phase, or do I have to worry about that as well?
If they are in phase, why are zobel nets hardly ever mentioned when using active crossovers. When using active xovers, is your only option in phase alignment the physical distance of each driver to your ear?
Is the only reason to use a zobel net obtaining a constant input impedance so a passive xover doesnt shift values depending on frequency.
my audio book is pretty thin on crossovers and covers compensation networks and the phase effects of the driver, but not both in the same example. Several articles i've read cover one or the other, but not both. i.e. the articles on ESP.
Thanks a lot
jt
imagine 2 speakers, a tweeter and a woofer crossed over at 1.5khz.
If I use a zobel on the woofer to counteract the high frequency impedance rise from the voice coil inductance and compensate the tweeters impedance peak at fs, so that both speakers have a resistive input impedance for a few octaves on both sides of the crossover frequency, will their cones move in phase, or do I have to worry about that as well?
If they are in phase, why are zobel nets hardly ever mentioned when using active crossovers. When using active xovers, is your only option in phase alignment the physical distance of each driver to your ear?
Is the only reason to use a zobel net obtaining a constant input impedance so a passive xover doesnt shift values depending on frequency.
my audio book is pretty thin on crossovers and covers compensation networks and the phase effects of the driver, but not both in the same example. Several articles i've read cover one or the other, but not both. i.e. the articles on ESP.
Thanks a lot
jt
jteef,
The Zobel network is there purely for the benefit of the passive crossover. If you use an active crossover, you won't need one. That said, I believe I recall seeing someone on this site saying that they use a Zobel to even out the load presented to the amplifier. If that line of reasoning appeals to you, by all means put in a Zobel network. I don't use them, myself.
As far as time alignment goes, yes, you're going to be limited to the physical position of the drivers...until you start looking at the active crossover. Keep in mind that any filter, regardless of where it is in the system, will give you an arbitrary amount of phase shift at a given frequency. You should account for this with an active crossover just as you would with a passive crossover. You also have the option of adding a phase shifter to the active crossover if you'd like, something that is frequently done on subwoofers these days.
Grey
The Zobel network is there purely for the benefit of the passive crossover. If you use an active crossover, you won't need one. That said, I believe I recall seeing someone on this site saying that they use a Zobel to even out the load presented to the amplifier. If that line of reasoning appeals to you, by all means put in a Zobel network. I don't use them, myself.
As far as time alignment goes, yes, you're going to be limited to the physical position of the drivers...until you start looking at the active crossover. Keep in mind that any filter, regardless of where it is in the system, will give you an arbitrary amount of phase shift at a given frequency. You should account for this with an active crossover just as you would with a passive crossover. You also have the option of adding a phase shifter to the active crossover if you'd like, something that is frequently done on subwoofers these days.
Grey
ok, i can understand that
what is a "phase shifting circuit" then?
The example in my audio book uses the scenario of a closed box woofer, and closed box midrange with equal sensitivities with a 1st order crossover. It specs the midrange QTC at 1(higher than normal, but it makes the example easier). The speakers are to be crossed over in the midband of the woofer, and at the fs of the midrange.
It is easy to see how you can get phase coherence with a first order crossover in this scenario. But unfortunately, my setup will be nothing like this. to my understanding the only network that will allow the cones to move exactly in phase near the crossover frequency is the 1st order. The 2nd and 4th order filters while providing phase coherency as by themselves, fail when the transfer function of the driver itself is added to the system.
To get close to optimum results, am into a lot of trial and error with phasor diagrams, matlab, and spice simulations, and then compensating with small distance adjustments? Is this what the pros do?
I would like to use active xovers with this setup, so I am really interested in how this phase adjustment thing works.
Thanks
jt
what is a "phase shifting circuit" then?
The example in my audio book uses the scenario of a closed box woofer, and closed box midrange with equal sensitivities with a 1st order crossover. It specs the midrange QTC at 1(higher than normal, but it makes the example easier). The speakers are to be crossed over in the midband of the woofer, and at the fs of the midrange.
It is easy to see how you can get phase coherence with a first order crossover in this scenario. But unfortunately, my setup will be nothing like this. to my understanding the only network that will allow the cones to move exactly in phase near the crossover frequency is the 1st order. The 2nd and 4th order filters while providing phase coherency as by themselves, fail when the transfer function of the driver itself is added to the system.
To get close to optimum results, am into a lot of trial and error with phasor diagrams, matlab, and spice simulations, and then compensating with small distance adjustments? Is this what the pros do?
I would like to use active xovers with this setup, so I am really interested in how this phase adjustment thing works.
Thanks
jt
I'm not too knowledgable on this subject, but I do know that several high end loudspeakers do compensate for phase alignment by the driver position when not using 1st order crossovers. Take a look at the majority of JM Lab's Utopia series, or to an even further extent, Wilson's line of speakers (pyramidal shaped WATTS, odd alignment of MAXX, SLAMM, WAMM, etc).
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