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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => SR Forum Archives => LAB Lounge FUD Forum Archive => Topic started by: Dana Osmun on February 17, 2011, 11:32:00 am

Title: Active crossover into Sub with passive crossover
Post by: Dana Osmun on February 17, 2011, 11:32:00 am
I have a pair of Yamaha subs with built in crossover.  I want to use an active crossover with these subs.  Is it best to bypass the internal crossover of the subs or will it be fine though the passive crossover?  I am assuming bypassing the internal crossover is the best option.

Tops: Yamaha SM12IV's
Subs: Yamaha A15W
Title: Re: Active crossover into Sub with passive crossover
Post by: jeff harrell on February 17, 2011, 06:04:57 pm
i would bypass the internal xovers. you will get a little less DC resistance if you bypass the internal crossover and that will allow a little more damping to control the woofer cone. coils are used in series and if they are iron core which most are they can saturate and cause a little distortion. active crossovers are always the best way to go. however i like using a Solen polypropolene cap on the HF drivers with a xover point about 50hz below the active xover point for a added HF driver protection.
Title: Re: Active crossover into Sub with passive crossover
Post by: Tim Padrick on February 18, 2011, 01:44:50 am
Don't just move the woofer plus from the XO out to the + input, as this will leave the unterminated XO across the amp - not a good thing.
Title: Re: Active crossover into Sub with passive crossover
Post by: Dana Osmun on February 19, 2011, 08:16:03 am
Thanks guys.  I ended up removing the crossovers from the input plate.  I originally was going to keep them on so I could have a choice of using them or bypassing them but it was easier to just eliminate them for now.
Title: Re: Active crossover into Sub with passive crossover
Post by: Art Welter on February 20, 2011, 04:11:46 pm
jeff harrell wrote on Thu, 17 February 2011 16:04

i would bypass the internal xovers. you will get a little less DC resistance if you bypass the internal crossover and that will allow a little more damping to control the woofer cone. coils are used in series and if they are iron core which most are they can saturate and cause a little distortion. active crossovers are always the best way to go. however i like using a Solen polypropolene cap on the HF drivers with a xover point about 50hz below the active xover point for a added HF driver protection.

The protection capacitor was a very good idea when using amps that can dump power supply DC voltage (Phase Linear, AKA Flame Linear)on the output when they fail.

A capacitor "about 50hz below the active xover point" would add an additional 90 degree phase shift.

A capacitor in series with a HF driver seldom will provide an acoustic 6 dB per octave "protection", it may actually cause an out of band increase in power level several octaves down from the nominal crossover point.

If you are using DC protection capacitors, it is best to spec them at least an octave below the active crossover.