Passive Crossovers

[Techno Commander]

Anyone know of anyone that builds passive crossovers?

Or any suppliers of "decent" 2 way boards?

I need a pair of 50Hz, 24db, 200W crossovers. Although, I may get away with 150W ones.;)

[Ali Tait]

How about going active with a Behringer? You could get a CX3400 for about 70 quid.

[Reid Malenfant]

I need a pair of 50Hz, 24db, 200W crossovers. Although, I may get away with 150W ones.;)
Andy, forget it m8 :lol:

Do you have any idea how big the inductors would be? Bloody huge m8 :eek: Each crossover would be enormous, the capacitors would need to be huge as well :mental:

Go active like Ali says, it'd probably work out about a tenth the price :eyebrows:

[Techno Commander]

Hmmmmm.................

12db slope might work. Its hard to go active with an integrated. :)

[Welder]

It could be done ;)
Your biggest inductor would be around 72mH which is big, but not impossible.
I’ve wound a 60mH before :eyebrows:
The main problem comes with the caps (480uF something) looking like your largest value. A 5 cap build with say
http://www.parts-express.com/pe/pshowdetl.cfm?PartNumber=027-447

So, no it isn’t quite as ridiculous as it would first seem but it will cost and it will be a very big build :rolleyes:

[Reid Malenfant]

It could be done ;)
Your biggest inductor would be around 72mH which is big, but not impossible.

Not impossible no ;) But to get the resistance as low as possible to actually make the thing worthwhile ferrites are out of the window & you'll need to be looking at E & I laminations on something like a 200VA transformer core with the EI gapped to avoid saturation. So that 4 lots of 200VA transformer cores & bobbins (assuming a stereo crossover) as well as the capacitors :eek: :mental:

:lolsign:

[Ali Tait]

Prolly cheaper to buy another amp and go active.

[Welder]

Go on Mark, you know you wanna give it a try :lol:
Wind the inductors for him and he’s in business.;)

[colinB]

Why is it hard to use active sub with an integrated? Or did i miss read something :scratch:

[Reid Malenfant]

Why is it hard to use active sub with an integrated? Or did i miss read something :scratch:
It's not, you just use the speaker output of the integrated to feed to the active crossover through a resistor divider network to lower the voltage, done it loads of times :cool:

[colinB]

If the integrated has a pre out cant you just use that?

[Reid Malenfant]

Yes, but if it doesn't then what i suggested will work ;) All you need to do is take a look at a lot of active subs & you'll often find they have speaker level inputs. These are fed to a resistor divider network, just a couple of resistors in reality & the voltage lowered to line level & fed to the active circuit..

[Welder]

Just out of curiosity I’ve done some rough calculations (bored) and using these (its low frequency so electrolytic are probably okay)
http://www.audiocap.co.uk/ft-100uf--100v-bipolar-electrolytic-264-p.asp

I reckon this could be built for under £400.

I’m not for a moment saying this is the sensible option and a D class at the back of an active crossover is a better solution :)

[Reid Malenfant]

John, you & i know it wouldn't be :lol: For starters to actually make it work all the drivers would need to have a totally flat impedance for the xover to work as calculated....

Now where abouts are we talking in the frequency spectrum here :scratch: Yep, right in the middle of where speaker impedance is literally all over the place :lolsign:

[Welder]

Hmm, maybe Mark ;)
I’ve assumed this is for a sub (?) What are we talking about, 20Hz to 50Hz perhaps, not a large range to keep flat :scratch:
Anyway, its not going to happen because just getting the choke wound if you didn’t do it yourself would cost a fortune :eek:
Easy to see why subs are in general active looking at this isn’t it :lolsign:

[Reid Malenfant]

Hmm, maybe Mark ;)
I’ve assumed this is for a sub (?) What are we talking about, 20Hz to 50Hz perhaps, not a large range to keep flat :scratch:
On the contrary, quite difficult ;) Lets assume the sub is ported & we actually want to reproduce 20Hz, the port resonance will need to be around the 20Hz mark (all depends on driver Qts & enclosure size) which means that the peak impedance will be about 40Hz (or just below) & this could be 50 ohms or more. So that'd need another dirty great big capacitor & choke & big power resistor in some kind of network to compensate for that impedance peak or the xover would be as good as useless :doh:

Anyway, its not going to happen because just getting the choke wound if you didn’t do it yourself would cost a fortune :eek:
Easy to see why subs are in general active looking at this isn’t it :lolsign:
Precisely :)

[Techno Commander]

Why is it hard to use active sub with an integrated? Or did i miss read something :scratch:

The subs are passive. :)

I did have some passive crossovers for them many years ago. They were basically an inductor (which looked like a 60mm square frame transformer) and a capacitor epoxied on top. Basic, but worked well. Unfortunately, I sold them off some years ago.:doh:

The integrated doesnt have pre outs and I dont (wont) have a spare power amp to use. As has been guessed, this is to go into the JBL subs and then feed the full range cabs.

I already have an active crossover to use if I have spare power amps. The online calculator I used reckons I need 36mH inductor and a 280uF capacitor. Might need a couple of caps in series to do that easily though.

[Ali Tait]

A tripath amp would be cheap.

[technobear]

This is what you need:

http://www.audiosanctum.co.uk/Subwoofer-Amplifiers/XTZ-Sub-Amp-1-DSP-Subwoofer-Amplifier-Gloss-Black.html

:)