DIY biamp 6-24 crossover

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#144
Trying to get up to speed here on something new. I need a four pole crossover for both high and low pass at 2.5kHz. The PDF says,
Also you can't see the value for C in the filters: That is determined by the center frequency that you want. Normally we will use the same value for C everywhere,with C/2 being half that value, as will be discussed shortly
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😕

Regards,
Dan
 
#148
Most of the commentary here has been about crossover functionality.

Be also mindful of differences in power amp and or driver sensitivity.

The goal is to find the right balance of noise and headroom. This is a SE circuit with about 5 volts output as l recall. So you want to have an amp input sensitivity of 1.4 volts ref 100 Watts (8 ohms) no higher than 2.8 volts ref 100 watts (8 ohms) to maintain a margin of headroom. This corresponds to 26 dB and 20 dB of power amp gain. Match power amp gain is preferred. A difference of 6 dB in power amp gain is acceptable provided headroom margin is observed to avoid clipping the crossover.

If you are using a horn of 107 dB sensitivity with is typical and a woofer of 95 sensitivity pad back the horn with a 10 dB passive attenuation between the amp and the horn to reduce noise.
 
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#151
Here’s a link to Mike Rothacher’s component value calculator that Nelson refers to on page 11 of the write-up, it’s pretty neat! It looks like you’ll want to be somewhere around 100-150nF (0.1-0.15uF) using the default resistor values in the calculator. 0.15uF is a standard value for Wima, unfortunately 0.075uF is not. Another smart design feature is the frequency is adjustable by the potentiometers, so you’ll have some adjustment range. For such a low crossover frequency you might set the center point a bit higher just to have a more useable range - since there aren’t too many (audio) applications for a crossover frequency below 30Hz.

PASS XO CALC

Leicaphile27 said:
Hi Everyone,

Can anyone recommend C & C/2 values which allow for a hi-low crossover point of 70-80hz? Is such a thing feasible with this circuit? Please let me know...Thanks!
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#152
macka said:
Most of the commentary here has been about crossover functionality.

Be also mindful of differences in power amp and or driver sensitivity.

The goal is to find the right balance of noise and headroom. This is a SE circuit with about 5 volts output as l recall. So you want to have an amp input sensitivity of 1.4 volts ref 100 Watts (8 ohms) no higher than 2.8 volts ref 100 watts (8 ohms) to maintain a margin of headroom. This corresponds to 26 dB and 20 dB of power amp gain. Match power amp gain is preferred. A difference of 6 dB in power amp gain is acceptable provided headroom margin is observed to avoid clipping the crossover.

If you are using a horn of 107 dB sensitivity with is typical and a woofer of 95 sensitivity pad back the horn with a 10 dB passive attenuation between the amp and the horn to reduce noise.
Click to expand...

This is interesting.
When you mean passive attenuation, do you mean something like a pot (or resistor) or something more complex like a B1 buffer?

Thanks,
-Josh
 
#153
Mike Rothacher's filter application has proven its worth for me already by letting me verify the capacitor values I need for my desired 2.5kHz starting point.

Regards,
Dan :wave:

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