back to  fEARful


 

  fEARful crossovers by greenboy

  1. fEARful CHEAP BUT GOOD crossovers
  2. fEARful 12/6 with Alpha6 or Alphalite6
  3. fEARful 12/6 with 6NM410 or 6ND410
  4. fEARful 12sub
  5. fEARful 1212/6
  6. fEARful 15/6
  7. fEARful 15sub
  8. fEARful 1515/66
  9. high-pass for 3-way fEARfuls
  10. L-pad resistors
  11. inductor spacing & orientation
  12. component substitution
  13. Danger, Will Robinson!


fEARful CHEAP BUT GOOD crossovers

Designs subject to revision ...

Don't be fooled by the fairly low parts count. To the neophyte this may seem to indicate 2nd or 3rd order slopes, but these networks are in fact tailored to driver-specific in-enclosure impedance and phase plots using a design technique I call Over-Damping, wherein value selections of primary and secondary components are radical compared to simplistic generic "textbook" selections. This provides steeper slopes at chosen thresholds and better off-axis summing. Textbook and generic design don't address specific drivers in actual enclosures.

Properly applied over-damping allows one to use beefier components while still keeping the build simple, the parts count low, and weight manageable. In the case of the fEARful, this is a better choice than using more components but of lesser power handling - both in terms of longevity and performance.

Over-damping could have been taken even further without destroying nice phase/time plots were one not concerned about nominal impedances presented to amplifiers when multiple cabs are used, ie: we want to keep cabs within safe 8-ohm ratings - or 4-ohm ratings for dual driver configurations. I have not ignored the "difficult load" issue so many designers sweep under the rug, nor have I had to de-rate enclosures to SIX ohms.

Linked Shopping Lists shown below are merely guidelines to assure proper values and ratings are known. Feel free to use like values from elsewhere as long as quality is assured.

Be aware that one merely need replicate the lowpass sections of 15/6 or 12/6 when doing crossovers for 15sub or 12sub if meant to be used as part of a 15/6 or 12/6 bass/keyboards/drums stack. For PA use an active crossover is recommended, set at a suitable lower frequency between 80 and 125 Hz.

Note that SpeakerHardware.com now has an entire section for fEARful crossovers in kit and completed form, as well as other fEARful components, kits, and finished enclosures.



fEARful 12/6 with Alpha6 or Alphalite6

This is the one to use if you WON'T be stacking with a 12sub or 15sub.

  • midrange highpass

12.0µF Erse PulseX 250v Metallized Polypropylene Film Capacitor

4.0mH Erse EQ 18AWG 1.091O 300w Air Core Inductor

  • woofer lowpass

3.0mH Erse ESQ 16AWG .178O 500w Solid Core Inductor

33.0µF Erse PulseX 250v Metallized Polypropylene Film Capacitor



fEARful 12/6 with 6NM410 or 6ND410

This is the one to use if you later wish to stack with a 12sub or 15sub.

  • midrange highpass

11.0µF Erse PulseX 250v Metallized Polypropylene Film Capacitor

1.5mH Erse EQ 18AWG .597O 300w Air Core Inductor

24.0µF Erse PulseX 250v Metallized Polypropylene Film Capacitor

  • midrange L-pad/attenuation

THREE 10.0O Erse 25w 5% Wirewound Resistor - 2 parallel on leg, 1 on shunt

  • and to toggle the padding on and off for possible stack with 12sub or 15sub - or if you want copious upper-mids

SPDT Switch

  • woofer lowpass

3.3mH Erse ESQ 16AWG .187O 500w Solid Core Inductor

33.0µF Erse PulseX 250v Metallized Polypropylene Film Capacitor



fEARful 12sub

  • woofer lowpass

3.3mH Erse ESQ 16AWG .187O 500w Solid Core Inductor

33.0µF Erse PulseX 250v Metallized Polypropylene Film Capacitor



fEARful 1212/6

  • midrange highpass

11.0µF Erse PulseX 250v Metallized Polypropylene Film Capacitor

24.0µF Erse PulseX 250v Metallized Polypropylene Film Capacitor

1.2mH Erse EQ 18AWG .567O 300w Air Core Inductor

  • woofer lowpass

1.5mH Erse ESQ 16AWG .163O 500w Solid Core Inductor

68.0µF Erse PulseX 250v Metallized Polypropylene Film Capacitor



fEARful 15/6

  • midrange highpass

15.0µF Erse PulseX 250v Metallized Polypropylene Film Capacitor

1.3mH Erse EQ 18AWG .567O 300w Air Core Inductor

  • midrange L-pad/attenuation

THREE 7.5O Erse 25w 5% Wirewound Resistor parallel on leg

TWO 40.0O Erse 25w 5% Wirewound Resistor parallel on shunt

  • option to toggle the padding on and off for possible stack with 12sub or 15sub - or to provide differing upper-mid presence:

SPDT Switch

  • woofer lowpass

2.7mH Erse ESQ 16AWG .163O 500w Solid Core Inductor

30.0µF Erse PulseX 250v Metallized Polypropylene Film Capacitor



fEARful 15sub

  • woofer lowpass

2.7mH Erse ESQ 16AWG .163O 500w Solid Core Inductor

30.0µF Erse PulseX 250v Metallized Polypropylene Film Capacitor



fEARful 1515/66

  • midrange highpass

27.0µF Erse PulseX 400v Metallized Polypropylene Film Capacitor

0.56mH Erse EQ 16AWG .227O 500w Air Core Inductor

56.0µF Erse PulseX 250v Metallized Polypropylene Film Capacitor

  • midrange L-pad/attenuation

FOUR 6.0O Mills 50w 1% Non-Inductive Resistor - parallel on leg

TWO 75.0O Mills 50w 1% Non-Inductive Resistor - parallel on shunt

  • woofer lowpass

TWO 2.7mH Erse ESQ 16AWG .163O 500w Solid Core Inductor - coils paralleled to get 1.35mH value

62.0µF Erse PulseX 400v Metallized Polypropylene Film Capacitor



high-pass for 3-way fEARfuls

To use an optional HF (high frequency) section comprised of compression driver and waveguide - aka "tweeter" - you will also need at least a partial crossover for it, something like this:


A high-pass filter is essentially half a crossover. The idea is to let the midrange driver (Alpha6A/Alphalite6A or 6ND410/6NM410) roll off naturally. The tweeter then just fills in the top of the spectrum. The difference in mid driver sensitivities and user tastes can be compensated for by using a variable L-pad.

The ASD1001 (cheapest reccomended compression driver for all but the 1515/66) is a PA-style compression driver that is quite a bit more capable than what's commonly found in bass cabs. And with a ~6.0K Hz third-order (18dB per octave) high pass filter, it's not being pushed hard at all in this application. The waveguides are constant-directivity devices, which means they don't beam the high frequencies - unlike most horns in bass cabs. The tonal balance stays fairly uniform across a 90-degree frontal arc so that nice, wide sweet spot characteristic of the fEARfuls can be extended up near the top of the spectrum. Also, the flare geometries of these waveguides means less of that boxy horn mouth distortion.

¤ highpass parts:

0.10mH Erse Perfect Lay 18AWG .121O 300w Air Core Inductor

1.0µF Erse PulseX 250v Metallized Polypropylene Film Capacitor

2.7µF Erse PulseX 250v Metallized Polypropylene Film Capacitor

Erse 8ohm 100w L-Pad

0.18mH Erse Perfect Lay 18AWG .169O 300w Air Core Inductor

or for 12/6 or 12/6cube with 18 Sound mid driver

0.15mH Erse Perfect Lay 18AWG .154O 300w Air Core Inductor



L-pad resistors

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 (nor should they be against each other). Cutting holes beneath each resistor network/bank aids free air passage so that thermal buildup is minimized. 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. Thermal shedding is GOOD.

In spite of the unsuitability of variable L-pad use with midrange drivers, some companies take the tempting shortcut of putting these "attenuators" in their cabs' midrange circuits. But to pad properly in this most important voicing range, fixed resistor networks are much better. Read why here: I WANT TO BELIEVE (in variable L-pads on mid drivers) -- But I Can't.

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:

Here's a handy series & parallel resistors/coils/caps calculator using those formulas to show how multiple components combine to values.



inductor spacing & orientation

Shown in the chart below, some possibilities of coil spacing and alignment and their effect on accurate audio performance. Don't be confused by the difference between solid-core and air-core designs. Though their shapes vary, what is important is the wire wrapping orientation.




component substitution

In general, the spec'd parts are very stout compared to those found in commercially available crossovers and can handle anything you can throw at a fEARful over a very long duty life. But if you are paranoid, for longevity and increased performance when driving very powerful amplifiers hard - ones that can take a fEARful to the top of its output and beyond - you might want to 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.

Also, BRAND NAME is not specifically important. What is important are ratings (voltage or wattage), values (mH, uF, ohms), tolerances (%), and type (solid core or air coil, cap type). If it's a quality line from a brand like Solen, Jantzen, Dayton, etc then it's fair game for use.

If I were to recommend higher-rated parts at all, it would be for dual-woofer 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 to upgrade components that are inline to the driver. After that, look at the ones on shunts to ground if you really like throwing money at things. ;  }

If it's likely you won't be using more than 300 or 400 watts into a single fEARful enclosure, you could drop back to 18AWG solid core coils on the lowpass, and 19AWG air coils on the highpass, and using PeX 250v caps instead of PulseX. This will shave your crossover cost. But realize that if you do  get a substantially more powerful amp later you'll then have to do component upgrades to assure reliability. In my estimation lowballing is a mistake.



Danger, Will Robinson!

Don't swap driver models when using these designs if you want predictable results and safe operation. Be aware of specific padding values because the padding isn't always just padding. Often the resistor values used also allows cap and coil values that otherwise would be unadvisable because of phase response or impedance.

With the impedance curve the crossover systems are designed for - with the values used - it's all good. But nilly-willy swapping of drivers presents scenarios where the impedance response fluctuates wildly enough to push some amplifier designs toward unstable operation, and significantly degrades enclosure performance too.



back to  fEARful