wanting to learn about crossovers....help?

[regal8r 5,000+ posts]

hey, i was wondering if someone on here, like squeak, could teach me about crossovers...like the differences between active and passive, etc...thx.

Click to read more...

 

[PESteele 10+ year member]

theres a sticky on it i forget which one just look around

 

[PESteele 10+ year member]

its the speaker faq in the speaker section

 

[regal8r 5,000+ posts]

k thx //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[PESteele 10+ year member]

np

 

[alphakenny1 10+ year member]

the difference between active and passive is pretty simple. a passive crossover is a crossover that has a set the crossover frequencies and crossover slopes for the speakers. like when you buy components, it should come usually with a passive crossover in which the crossover slopes and frequencies are preset, you cannot change it.

an active crossover is where the user can choose the crossover frequencies and slopes unlike a passive crossover. such in my case, i am running an active setup where my mids are bandpassed (LP and HP) at 63hz @ 12db/oct and 2.5khz @ 12db/oct. my tweeters are High passed at 3.15khz @ 24db/oct. My sub is lowpassed at 80hz @ 12db/oct. But if i wanted to, i could change the crossover pts and slopes for example i could HP my tweets at 2.5khz @ 18db/oct if i choose. and same thing with the others. here's a good site, http://www.bcae1.com/xovrslop.htm. notice how the bigger the slope the steeper it is. so 24db/oct is much steeper than 6db/oct. any other questions, feel free to ask.

 

[thch 10+ year member]

i had a nice long reply. but the site gimpped me.

i can answer any Qs.

if you have a background in algebra or caclulus, i can do even better.

if you know about complex numbers. well it would help.

 

[jaygeorge1979 10+ year member]

another important crossover fact: whether it is active or passive depends on exactly where in the entire system you crossover the signal....if you have the crossovers installed in the speaker wire right before the speaker, it is a passive setup, but if you have a crossover used on the signal wire coming out of your source (that is, BEFORE the signal gets to the amplifier) then it is called active crossover:

CD player line out --> amplifier --> crossover --> speakers (this is PASSIVE)

CD player line out --> crossover -->amplifier --> speakers (this is ACTIVE)

 

[squeak9798 5,000+ posts]

another important crossover fact: whether it is active or passive depends on exactly where in the entire system you crossover the signal....if you have the crossovers installed in the speaker wire right before the speaker, it is a passive setup, but if you have a crossover used on the signal wire coming out of your source (that is, BEFORE the signal gets to the amplifier) then it is called active crossover:
CD player line out --> amplifier --> crossover --> speakers (this is PASSIVE)

CD player line out --> crossover -->amplifier --> speakers (this is ACTIVE)

I like this explaination much better than alphakenny1's. It's not so much fixed points/slopes vs. flexible points/slopes (since there are some very flexible passive xovers out there with adjustable points/slopes, and some very inflexible active xovers with maybe only two xover points and that's it)....but rather where in the signal path the xover is located. An active xover is located prior to amplification (either in the HU, between the HU and the amplifier, or in the amplifier). And a passive xover is located after amplification (between the speakers and amplifier).

 

[jaygeorge1979 10+ year member]

good point squeak...i didnt disagree with alphakenny because in most typical situations, his explanation can be correct...i dont find adjustable passive crossovers to be as common as fixed ones, and i also dont find fixed active crossovers to be as common as adjustable

HOWEVER you are indeed correct

 

[squeak9798 5,000+ posts]

good point squeak...i didnt disagree with alphakenny because in most typical situations, his explanation can be correct...i dont find adjustable passive crossovers to be as common as fixed ones, and i also dont find fixed active crossovers to be as common as adjustable
HOWEVER you are indeed correct

But I guess if we really wanted to be fickle about it, we could use Fmods as an example of a "passive" xover that comes prior to amplification //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif//content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif

Hrmph. Guess maybe we need to come up with a better definition.......Let's try;

An active crossover is a crossover that needs a power input. A passive xover is an xover that operates without a power input. Active xovers are typically located in the signal path prior to amplification (in the HU, between the HU and amp, in the amp), while passive xovers are typically located after amplification between the amplifier and the speaker. Active xovers are typically much more flexible by offering adjustable xover frequencies and possibly xover slopes, while passive xovers typically offer only fixed frequencies and slopes.

 

[jaygeorge1979 10+ year member]

An active crossover is a crossover that needs a power input. A passive xover is an xover that operates without a power input. Active xovers are typically located in the signal path prior to amplification (in the HU, between the HU and amp, in the amp), while passive xovers are typically located after amplification between the amplifier and the speaker. Active xovers are typically much more flexible by offering adjustable xover frequencies and possibly xover slopes, while passive xovers typically offer only fixed frequencies and slopes.

*applause*

as long as we arent getting fickle //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[thch 10+ year member]

for the system layout there are 2 types of filters -- pre-amplifer filters, and post-amplifier filters.

a pre-amplifier filter can be passive, active, or digital. passive would be things like fmods. active would be feedback based with opamps. digital is based upon adding current and previous input and output samples together.

digital offers the highest matching possible and is very flexible -- just change the filter coefficients in a file and you have a new filter. further, the filter is exactly what it was programmed to be. active and passive filters may be off slightly, which can prevent steep slopes from being used effectively.

post amplifier is all passive and is based upon energy storage mechanism.

----

interesting notes:

* digital FIR filters are delay based. this has an advantage of being linear phase.

* digital IIR filters simulate active/passive filters.

* passive filters are energy based.

* active filters are feedback based.

* useful 12dB/oct passive filters require two oposing of energy storage (mass/springs, inductance/capacitance, ect...)

* with only one form of energy storage and energy removal (R-C-R-C networks for example), the system will be overdamped.

* adding feedback can simulate this second enegy storage device, and active filters can be made without inductors for this reason.

* all non-FIR filters can be made as cascades of 2nd or 1st order systems: 24db/oct is two 2nd order systems in a row. 18db is a 1st followed by a 2nd.

and there is much more if you want to get into details.

edit -- added info.