Semi active?

[bunnerrabbit 10+ year member]

Is there such thing as semi active? Like limiting high pass on headunit 100hz and using low pass on amp for mid-range and other 2 channels to tweeter using high pass? I know it would be a ton easier just to use component set but want to play around and see how things work.

P900.5 amp x731bt head unit.

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[trumpet 5,000+ posts]

Is there such thing as semi active? Like limiting high pass on headunit 100hz and using low pass on amp for mid-range and other 2 channels to tweeter using high pass? I know it would be a ton easier just to use component set but want to play around and see how things work.
P900.5 amp x731bt head unit.

That is fully active.

 

[bunnerrabbit 10+ year member]

My understanding of fully active is using the head unit or crossover to control signal to amps. What im explaining is using multiple items to have similar outcome.

 

[honkyg 10+ year member]

active is defined as adjustable digital processing in the low voltage signal chain before amplification, whether be it from head unit, crossover, dsp, or on-board amplifier controls, i.e.; no solid state components used for primarily separating the signal between drivers after amplification, however, savvy people will incorporate passive filtering components on actively controlled amplified drivers as a fail safe in keeping them from getting destroyed, such as 80hz bass blockers used on midbass drivers that are actively crossed over at 200hz, for example.

 

[Jeffdachef 5,000+ posts]

its Still active but limited active whenever an amp crossover is involved. amp only has 12 db slopes and limited frequency ranges so your results arent that good especially those ppi crossovers that just makes everything sound like complete @ss when turned on.

 

[honkyg 10+ year member]

depends on the amp, jeff. alot of newer amplifiers with active crossovers will have switchable 6 or 12db per octave slopes, but there are also many with 18 and 24db options, like db drive and jl slash series,.. even more so in the higher end sound quality gear. older amplifiers with crossover cards and chip sets such as orion xtr, kicker zrx and rf dsm ix can be changed out or modified to tailor the freq and slope for the application.

 

[Boomin_tahoe 5,000+ posts]

What's the difference between 6, 12, 18 and 24 slopes?

 

[honkyg 10+ year member]

how attenuated the signal amplitude is in decay (roll off) or attack (roll in) before or after the crossover point,.. taking an arbitrary crossover point, lets say 80hz,.. attenuation doubles for every octave (doubling or halving of frequency) above or below the crossover point, so high passing at 6db per octave will roll the lower frequencies to effectively attenuate the signal by 6db at 40hz (3db at 60hz - half octave, 12 db at 20 hz- 2 octaves, 24db at 10hz - 3 octaves), whereas low passing will roll the higher frequencies off at a rate of 6db at 160hz (3db at 120hz - half octave, 12db at 320hz - 2 octaves, 18db at 480hz - 2.5 octaves, 24db at 640hz - 3 octaves). higher db/octave slopes will attenuate at a faster rate over the same frequency band.

a good dsp will have the ability to adjust the slope on each channel, allowing for overlapping and underlapping of crossover points,.. for instance, a midbass high passed at 80hz and the sub low passed at 120hz (overlapping) if there's a dip in response around the 100hz region. just the inverse configuration would be underlapping needed if theres a peak.

also, different slope rates can be used on either side of the crossover point to blend two corresponding drivers'. takes alot of trial and error without an rta and all the different configurations you can apply, but what sounds best to your ear is most important, imo.

 

[Jeffdachef 5,000+ posts]

What's the difference between 6, 12, 18 and 24 slopes?

6, you'll still hear a lot of the frequencies you cut but it slowly dies(rolls off) out after a certain point so for example if you low pass at 500hz, you'll still somewhat hear 1000hz and very little of 1500hz and slowly nothing. 24 is almost a straight up cut off low pass at 500, you'll be lucky to hear 800hz