2 way crossovers?

[metal_flowboard]

ok i dont know much bout corssovers and i'm not finding anything useful
searching the web

so lemmy just check if iv got this right, crossovers just take a
certain frequency out to certain speakers, so you have your low to your
woofers and your high to your tweeters, i think iv got that bit

and a 2-way crossover is one input with a high and a low output from
one crossover, i think
so if thats the case, what really gets me is what happens to the ohm's
of the speakers when they are wired into it?

if i had a 2way crossover with a 4ohm woofer and a 4ohm tweeter wired
to it, would the 2 be eqivilant to parrallel or series wiring? how many
ohms would it be?
would it be like parallel and make 2ohms or series making it 8?

hope im making some sense coz this has been bugging me for a while now

[GregS]

In article om>, "metal_flowboard" > wrote:
>ok i dont know much bout corssovers and i'm not finding anything useful
>searching the web
>
>so lemmy just check if iv got this right, crossovers just take a
>certain frequency out to certain speakers, so you have your low to your
>woofers and your high to your tweeters, i think iv got that bit
>
>and a 2-way crossover is one input with a high and a low output from
>one crossover, i think
>so if thats the case, what really gets me is what happens to the ohm's
>of the speakers when they are wired into it?
>
>if i had a 2way crossover with a 4ohm woofer and a 4ohm tweeter wired
>to it, would the 2 be eqivilant to parrallel or series wiring? how many
>ohms would it be?
>would it be like parallel and make 2ohms or series making it 8?
>
>hope im making some sense coz this has been bugging me for a while now

Passive crossovers are not an absolute thing. They present an impedance
to the driver in series with it, in the region you don't want much sound comming
out. So a tweeter will get less and less lows the lower the frequency.
I'm trying to simplify it but things can be complex. They also change the phase
at the crossover frequency. You have to know the impedance at the set
crossover frequency so you can predict whats going to happen.
The crossover usually keeps the same driver impedance into the system
impedance. A 4 ohm woofer and a 4 ohm tweeter will still have a 4 ohm
system impedance for the most part. There is also phase changes in drivers
as they dwindle in output out of their passband. Position or phasing of the drivers
also have large effects at the crossover frequency.

Complications exist, such as bass blockers. The blocker may be 4 ohms, but
a 4 ohm mid driver may have a 10 ohm peak at the point you want to eliminate.
To reduce that 10 ohm back to 4 ohm requires another circuit called
a Zoebel.

greg

[KU40]

basically, they don't play the same frequencies so their impedences
don't compound. if you had a 4 ohm woofer and a 8 ohm tweet and a
crossover set at 3000 hz, the amp would see 4 ohms under 3000 and 8
ohms over 3000 (this is a bit simplified, there is overlap, but you
don't need to worry about that much).


--
KU40

[Matt Ion]

KU40 wrote:
> basically, they don't play the same frequencies so their impedences
> don't compound. if you had a 4 ohm woofer and a 8 ohm tweet and a
> crossover set at 3000 hz, the amp would see 4 ohms under 3000 and 8
> ohms over 3000 (this is a bit simplified, there is overlap, but you
> don't need to worry about that much).

Good simplification... remember that the crossovers themselves present
some impedence as well; that's how they work, with the impendence of
each portion increasing above the crossover point.

The listed impedences of the drivers are only "nominal" anyway, and
actual impedence varies greatly across the frequency spectrum, so in
general, it's all an averaged figure anyway.


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[GregS]

In article <3yaZf.2514$_u1.1588@pd7tw2no>, Matt Ion > wrote:
>KU40 wrote:
>> basically, they don't play the same frequencies so their impedences
>> don't compound. if you had a 4 ohm woofer and a 8 ohm tweet and a
>> crossover set at 3000 hz, the amp would see 4 ohms under 3000 and 8
>> ohms over 3000 (this is a bit simplified, there is overlap, but you
>> don't need to worry about that much).
>
>Good simplification... remember that the crossovers themselves present
>some impedence as well; that's how they work, with the impendence of
>each portion increasing above the crossover point.
>
>The listed impedences of the drivers are only "nominal" anyway, and
>actual impedence varies greatly across the frequency spectrum, so in
>general, it's all an averaged figure anyway.

Thats why a off the shelf crossovers are almost useless without
proper adjustments.

greg