vifa logic x-0ver

[ton def]

I have the vifa logic BC14SG49-4 and AC25SG05-4. I was going to attempt to replicate the Madisound swifty speaker kit. But the kit used the 8 ohm version of the midwoofer. The differences seem to be too much to try and re configure the kits x-over. I found an x-over for these drivers. But it seems odd to me. It appears to have no damping for the tweeter. There is a 7db difference in spl between the woofer and tweeter.
http://www.chyna.wz.cz/audio/index.htmlWill this work ?

 

[ton def]

anybody ?

 

[blue934]

Not too sure about that xo in link. The phase seems way off and you're right, there's no tweeter attenuation although a 5-10ohm resister in line before the HP filter would be a simple starting point.

As far as the swifty goes, Just cut the inductor in half and double the cap on the woofer circuit to accept the 4ohm model and it should be very close.

David

 

[Sonce]

C2051 attenuate the tweeter. Crossover seems to be OK.

EDIT: hmm... on the second look, "position" and "relative distance" are 0 mm both for the midbass and the tweeter. Maybe simulation is not the correct one, regarding the actual position of the drivers.

 

[Sonce]

there's no tweeter attenuation although a 5-10ohm resister in line before the HP filter would be a simple starting point.
David

Are we looking at the same crossover schematic?
This is the one:
www.chyna.wz.cz/audio/efekty/vyhybka.png

 

[ton def]

Are we looking at the same crossover schematic?
This is the one:
www.chyna.wz.cz/audio/efekty/vyhybka.png

Yes that is it. But I can't figure out what he is doing. Though he does appear to know what he is doing ?

 

[blue934]

Yes, that's the one I was looking at. I've not seen a parallel cap used for attenuation before but if it works, I stand corrected.


David

 

[PeteMcK]

great way to fry an amp, use a proper L pad: L pad calculator - attenuation dB damping impedance decibel loudspeaker speaker voltage divider - sengpielaudio Sengpiel Berlin

 

[ton def]

http://www.madisound.com/pdf/swifty.pdf Yes, I can not understand why he would do the attenuation that way. It just seems unnecessarily complex and costly.But this x-over looks to be less complex than the swifty x-over.

 

[blue934]

A bit but a few resisters are cheap, and the LP circuit is simpler so a bit of a wash.

 

[amt]

Just do as blue934 suggests: double the cap and halve the inductor. This is a LR2 @ 1600. As to the tweeter attenuation, this post explains it.

http://www.diyaudio.com/forums/multi-way/114916-replace-crossover-existing-box-3.html#post1394839

amt

 

[ton def]

Thanks for all the help Gentlemen. I am going to go with the modified swifty x-over. I trust the Leap done at Madisound to be good.The 8ohm woof had an spl of 87 db, the 4 ohm 89db. So am I correct in thinking that I can lower R3 to about 2ohm for proper attenuation ?

 

[Sonce]

great way to fry an amp, use a proper L pad

L-pad is a bullet-proof solution, but capacitor parallel to the tweeter is not necessarily a way to fry the amplifier (although I personally would put a 2R2 ohm resistor serially to that capacitor). Simulation on the link show more than 5 ohm at 20kHz, so it has plenty of reserve at higher frequencies.