Greenboy passive crossovers

From TalkBass Wiki

Revision as of 19:11, November 1, 2009

Designs subject to improvement but every one of these babies will do considerably better than generics. Coming soon - versions for:

1. 15sub (lowpass only)

fEarful 12/6 with Alpha6

° Midrange 2nd-order highpass (reverse polarity):

12.0μF Erse PulseX 250v Metallized Polypropylene Film Capacitor - $4.12

4.0mH Erse EQ 18AWG 1.091Ω 300w Air Core Inductor - $15.23

° Woofer 2nd-order lowpass:

3.0mH Erse IXQ 16AWG .242Ω 400w Solid Core Inductor - $11.46

33.0μF Erse PulseX 250v Metallized Polypropylene Film Capacitor - $8.65

$39.46 before shipping

fEarful 12/6 with 6ND410

° Midrange 3rd-order highpass (reverse polarity):

11.0μF Erse PulseX 250v Metallized Polypropylene Film Capacitor - $3.82

1.5mH Erse EQ 16AWG .407Ω 500w Air Core Inductor - $10.88

24.0μF Erse PulseX 250v Metallized Polypropylene Film Capacitor - $6.25

° L-pad attenuation

SIX 20.0Ω Erse 25w 5% Wirewound Resistor - $3.60 - 4 paralleled on series leg, 2 paralleled on shunt

or for ultimate audio quality and power handling

THREE 10.0Ω Mills 50w 1% Non-Inductive Resistor - $16.35 - 2 paralleled on series leg, 1 on shunt

and to toggle it on and off

Radio Shack DPDT Red Rocker Switch - $3.99

° Woofer 2nd-order lowpass:

3.3mH Erse ESQ 16AWG .187Ω 500w Solid Core Inductor - $17.34

33.0μF Erse PulseX 250v Metallized Polypropylene Film Capacitor - $8.65

$54.53 or $67.28 before shipping

fEarful 12sub

° Woofer 2nd-order lowpass:

3.3mH Erse ESQ 16AWG .187Ω 500w Solid Core Inductor - $17.34

33.0μF Erse PulseX 250v Metallized Polypropylene Film Capacitor - $8.65

$25.99 before shipping

fEarful 15/6 or fEaRB15

° Midrange 2nd-order highpass (reverse polarity):

15.0μF Erse PulseX 250v Metallized Polypropylene Film Capacitor - $4.97

1.3mH Erse EQ 18AWG .567Ω 300w Air Core Inductor - $7.93

° L-pad attenuation

FIVE 12.0Ω Erse 25w 5% Wirewound Resistor - $3.00 paralled on series leg

THREE 51.0Ω Erse 25w 5% Wirewound Resistor - $1.80 paralleled on shunt

or for ultimate audio quality and power handling

THREE Mills MRC50 7.5Ω 1% Non-Inductive Resistors - $16.35 paralleled on series leg

TWO Mills MRC50 40.0Ω 1% Non-Inductive Resistors - $10.90 paralleled on shunt

° Woofer 2nd-order lowpass:

3.0mH Erse IXQ 16AWG .242Ω 400w Solid Core Inductor - $11.46

30.0μF Erse PulseX 250v Metallized Polypropylene Film Capacitor - $8.09

$37.25 or $59.70 before shipping

fEarful 1515/66

° Midrange 3rd-order highpass (reverse polarity):

22.0μF Erse PulseX 400v Metallized Polypropylene Film Capacitor - $7.00

0.7mH Erse EQ 16AWG .254Ω 500w Air Core Inductor - $7.00

47.0μF Erse PulseX 250v Metallized Polypropylene Film Capacitor - $10.55

° L-pad attenuation

FOUR Mills MRC50 5.0Ω 1% Non-Inductive Resistor - $21.80 - paralleled on series leg

TWO Mills MRC50 60.0Ω 1% Non-Inductive Resistor - $10.90 - paralleled on shunt

° Woofer 2nd-order lowpass:

3.0mH Erse IXQ 16AWG .242Ω 400w Solid Core Inductor - $11.46

2.7mH Erse IXQ 16AWG .226Ω 400w Solid Core Inductor - $10.91 - paralleled with coil above to get 1.64 mH

62.0μF Erse PulseX 400v Metallized Polypropylene Film Capacitor - $16.95

$96.57 before shipping

Component Substitution

For even better performance and power handling, and less dB insertion loss, one can substitute 14AWG solid core inductors and 16AWG air core inductors and 400 volt capacitors of the same essential values. Erse's site often shows upgrade substitutes for the components, but sometimes it misses them too. So do look at the indexes for each part type if you don't see one listed.

I'd especially recommend higher-rated parts for 1212/6 and 3015LF-based systems with a lot of power amp behind them. If you don't want to substitute everything, the order of precedence for improvement would be:

1. solid core inductor (low pass)
2. air core inductor (high pass)
3. and last, capacitors

If you are absolutely certain you won't be using more than around 350 watts into a single fEarful enclosure you can drop back to 18AWG solid core coils on the lowpass and 19AWG air coils on the highpass, and use PeX 250v caps instead of PulseX. This will shave a little more off your crossover cost. But if you get a more powerful amp then it's kind of a Pyrrhic victory... and why build down after coming this far?

L-pad Resistors

Resistors can be arranged in parallel or in series to arrive at needed values and ratings. In some of these crossover plans you will need to place multiple resistors in parallel or series, into a network/bank, using wire to connect appropriately. On either the series leg or the parallel shunt the schematics show only a single element and the total value for that, but the text in the parts list details this. Arrangements and formulas:

Resistors take the energy that's been attenuated and convert it to HEAT. As such, it's good to have supporting standoffs at each end of them so they are not against the circuit board (not should they be against each other). Cutting holes beneath each resistor network/bank can also aid free air passage. Make sure each hole is wider than the resistor network that sits above it so that hot air from beneath can easily escape around the sides.

Danger, Will Robinson!

Don't swap drivers with these driver-specific crossover designs if you want smooth predictable results and safe operation. Especially don't use the designs without the specific padding values - because the padding isn't always just padding. Sometimes it also allows component values that couldn't otherwise be applicable. With the impedance curve the crossover systems are designed for, with the values used, it's all good. But nilly-willy swapping presents a few scenarios where system impedance drops low enough to potentially cause unstable amplifier operation.

back to Fearful™ 12/6 & 15/6