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Ruark Equinox, active crossovers and tweeter attenuation

gingermrkettle

gingermrkettle

Deep vein trombonist
Just picked up a cheap pair of Ruark Equinoxes. The plan is to use them in a system which already has an active crossover in it (a 24dB/octave LR centred on 3.1kHz but which can have the crossover frequency changed through different resistor combinations), but the standard crossover has a 3.3R in series with the tweeter and a 10R in parallel which as I understand it is a standard thing to damp the Scanspeak tweeter in addition to a standard 2nd order LC network.

Could you just replicate the 3.3R/10R network on the output of the treble amp?
 
Sorry but if you don't know that.... and as you haven't mentioned important things like baffle step compensation.. I would suggest you leave well alone!
 
gingermrkettle said:
Just picked up a cheap pair of Ruark Equinoxes. The plan is to use them in a system which already has an active crossover in it (a 24dB/octave LR centred on 3.1kHz but which can have the crossover frequency changed through different resistor combinations), but the standard crossover has a 3.3R in series with the tweeter and a 10R in parallel which as I understand it is a standard thing to damp the Scanspeak tweeter in addition to a standard 2nd order LC network.

Could you just replicate the 3.3R/10R network on the output of the treble amp?
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That network does help make the impedance curve more even in addition to providing attenuation, but that only matters if you have a passive crossover.
 
Arkless Electronics said:
as you haven't mentioned important things like baffle step compensation
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Not in the original crossover in the first place.
Julf said:
That network does help make the impedance curve more even in addition to providing attenuation, but that only matters if you have a passive crossover.
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Fair enough. A back of the packet calc gives attenuation of a bit under 3dB with a 6ohm nominal driver, so the first step will be to put a divider network on the input to the treble amp of that sort of order and see how it works.
 
gingermrkettle said:
Not in the original crossover in the first place.

Fair enough. A back of the packet calc gives attenuation of a bit under 3dB with a 6ohm nominal driver, so the first step will be to put a divider network on the input to the treble amp of that sort of order and see how it works.
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Oh yeah?
 
Arkless Electronics said:
Oh yeah?
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Yep. Standard 2nd order networks on bass and treble, with the attenuation network noted above.
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It's likely that the inductor for the bass crossover, with the resistance of the voice coil, performs the baffle step correction as well as forming a second order low pass network with the capacitor.
 
Arkless Electronics said:
It's likely that the inductor for the bass crossover, with the resistance of the voice coil, performs the baffle step correction as well as forming a second order low pass network with the capacitor.
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Being pedantic, the number of components used is irelivent. It the acoustic order that counts, so this could be a 3rd or 4th order crossover.

Edit: Forgot to say that I agree that the baffle step would be formed by the large inductor.
 
fatmarley said:
Being pedantic, the number of components used is irelivent. It the acoustic order that counts, so this could be a 3rd or 4th order crossover.

Edit: Forgot to say that I agree that the baffle step would be formed by the large inductor.
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Nope... it's a second order crossover. The speakers acoustic roll-off may make it 3rd or 4th as a system but that crossover is electrically 2nd order.
 
Arkless Electronics said:
Yeah? How so?
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The driver impedance and raw frequency response of the driver is combined with a value of inductor to achieve a flat response (the order doesn't come in to it, you only care about a flat response). The capacitor forms the knee of the crossover slope, and that could be anything from 1st order to anything higher depending on the impedance, drivers raw frequency response and value of capacitor chosen.
 
fatmarley said:
The driver impedance and raw frequency response of the driver is combined with a value of inductor to achieve a flat response (the order doesn't come in to it, you only care about a flat response). The capacitor forms the knee of the crossover slope, and that could be anything from 1st order to anything higher depending on the impedance, drivers raw frequency response and value of capacitor chosen.
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OK well we'll have to completely disagree on that then! A simulation I quickly tried says I'm right....

I have a feeling we're discussing different things though...
 
Arkless Electronics said:
OK well we'll have to completely disagree on that then! A simulation I quickly tried says I'm right....

I have a feeling we're discussing different things though...
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I'm talking simulations, but with measurements I've taken from real speakers.
 
fatmarley said:
Calculators are a waste of time. You need to measure if you want accurate results.
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Hi,
The original poster asked about whether the series resistor with the tweeter, and the parallel resistor with the tweeter can be implemented in the amplifier output.

The original poster indicates that the parallel resistor is used to dampen the tweeter response and my interpretation of the series resistor is for tweeter amplitude modification in the passive crossover.

If the active crossover has any equalisation, then the tweeter dampening can be implemented here, as well as the tweeter amplitude level adjustment.

I referenced the website for the baffle step so as to indicate the options for compensation.

Regards,
Shadders.
 
fatmarley said:
I'm talking simulations, but with measurements I've taken from real speakers.
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This is theory not real speakers and on this type of simulation (ie just passive inductors, caps and resistors etc) the computer simulator is always spot on.

What I'm saying, to be clear, is that the inductor can serve two purposes and can simultaneously provide the large bass boost and treble cut required for the "baffle step correction" AND be half of the 2nd order crossover in conjunction with the capacitor. I'm not discussing acoustic response or any thing like that, just the response which the crossover is responsible for.
 
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