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Old 9th April 2002, 02:13 AM   #1
JoeBob is offline JoeBob  Canada
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Default +3dB at the crossover point.

Well, I've pretty much finished designing my preamp/crossover and am just waiting for a few parts to begin building it. My questions is, I'm making my crossover point 600Hz, but at 600Hz, neither the high or the low is being attenuated, correct? Therefore there would be a +3dB increase at 600Hz because of both the low and the mids reproducing it, correct again? In that case would it be a good idea to attenuate by 3dB at 600Hz? And since I'm using a 12dB per octave crossover, it would be even better if the attenuation rolled of at the same, right?

Or would I be better off attenuating less then 3dB? I don't know if in reality it ever does achieve the +3dB bost, since the mids and woofers and physically quite a ways apart (relatively speaking that is).
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Old 9th April 2002, 02:18 AM   #2
paulb is offline paulb  Canada
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Well, the crossover frequency is usually defined to be the 3dB down point. Or is it the half-power point? Something like that. Anyway, summed together they should equal 0.
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Old 9th April 2002, 02:23 AM   #3
JBL is offline JBL  Canada
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The crossover point is defined at minus 3bd wich is half the power. So it will give a flat curve.
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Old 9th April 2002, 02:25 AM   #4
JoeBob is offline JoeBob  Canada
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Ah, silly me, I guess this makes things easier for me then, thanks.
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Old 9th April 2002, 02:33 AM   #5
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Actually, for the majority of home listening, you will find that if each driver is -3dB, the nett effect will be +3dB @ the crossover point. So, each driver must be -6dB @ the crossover point to gain a flat response. Off the top of my head, this makes Linkwitz Riley alignment crossovers particularly useful as they are -6dB @ the crossover point. If the drivers are physically quite a distance apart, then each driver will need a little less than 6dB attenuation @ the crossover point but it will still be relatively more than 3dB.
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Old 9th April 2002, 02:47 AM   #6
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I seem to remember reading that if you are using 12 dB/octave crossovers, both drivers should be -6dB at the crossover point. But if you are using 6 dB/octave crossover, the drivers should be 3 dB down at the crossover point.

Of course, these were for a passive crossover system.
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Old 9th April 2002, 02:52 AM   #7
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Quote:
Originally posted by kelticwizard
I seem to remember reading that if you are using 12 dB/octave crossovers, both drivers should be -6dB at the crossover point. But if you are using 6 dB/octave crossover, the drivers should be 3 dB down at the crossover point.

Of course, these were for a passive crossover system.
Butterworth alignment both drivers are -3dB @ crossover

Linkwitz Riley alignment both drivers are -6dB @ crossover
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Old 9th April 2002, 09:31 PM   #8
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In point of fact, after you consider both the phase
and frequency response of both the filters and the
speakers, you can't count on anything. All you can do
is give yourself some wiggle room on the filter
parameters and adjust for the best result.
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Old 9th April 2002, 10:58 PM   #9
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I couldnt agree more Nelson, when it comes to passive crossovers, there are just to many factors.
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