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crossover mods

mega lord

mega lord

Centre tapped
Hello everyone,

Today i have had the crossovers out of my B&WP4's to see what components to change. Each crossover consists of 2 inductors(air cored for tweeter and ferrite cored for bass/mid), 1 bennic 11W1R5J wirewound cement resistor and two bennic bipolar caps (10uf/70WV and 7uf/70WV)

I have had trouble trying to find upgraded resistors and capacitors in the values of the originals.

1)I assume the bennics resistor values are 11W, 5 ohms, tolerance 5%. If this is correct the nearest i can find for a replacement is 10W/5 ohms. Will this be ok - how will the different wattage effect the xover?

2)I have looked at various upgrades for the caps (wilmslow, soniqs and kimber) which all are polypropylene and physically larger than the bennics. Wilmslow and soniqs caps are both found in 10uf but not 7uf - the nearest is 6.8uf. Also the voltages are way higher than the bennics. The only 7uf cap i can find is a kimber but again the qouted wattage is higher than the bennics.

Can anyone advise me on what these differing values will mean for the working of the xover and which make of caps would be best?

I dont want to change the crossover specifications but do want the largest improvement i can get by upgrading components with some of higher quality but same values. By the way i run a full naim system.

Am i asking too much? Can anyone help me.

Thanks stu
 
hopefully Markt will have an answer , as he knows his stuff with regard to crossovers , he can certainly point you toward the suppliers and type of resistors/caps to go for. If he doesnt raise his head , send him a PM....Jon
 
mega lord said:
Hello everyone,

Today i have had the crossovers out of my B&WP4's to see what components to change. Each crossover consists of 2 inductors(air cored for tweeter and ferrite cored for bass/mid), 1 bennic 11W1R5J wirewound cement resistor and two bennic bipolar caps (10uf/70WV and 7uf/70WV)

I have had trouble trying to find upgraded resistors and capacitors in the values of the originals.

1)I assume the bennics resistor values are 11W, 5 ohms, tolerance 5%. If this is correct the nearest i can find for a replacement is 10W/5 ohms. Will this be ok - how will the different wattage effect the xover?

2)I have looked at various upgrades for the caps (wilmslow, soniqs and kimber) which all are polypropylene and physically larger than the bennics. Wilmslow and soniqs caps are both found in 10uf but not 7uf - the nearest is 6.8uf. Also the voltages are way higher than the bennics. The only 7uf cap i can find is a kimber but again the qouted wattage is higher than the bennics.

Can anyone advise me on what these differing values will mean for the working of the xover and which make of caps would be best?

I dont want to change the crossover specifications but do want the largest improvement i can get by upgrading components with some of higher quality but same values. By the way i run a full naim system.

Am i asking too much? Can anyone help me.

Thanks stu
Click to expand...


1) The 10W power rating will be just fine.

2) With caps, you want to match the capacitance value, but a higher voltage rating is OK, or even a good thing.

In practice, a 6.8uF is perfectly acceptable for 7uF - the difference is only 3%, which is less than the accuracy of the values. The original Bennics will only have been good to 20% (at best).

Any polypropelene, even the cheapest, beats any electrolytic into a cocked hat.

My own opinion is that once you get a decent dieletric (e.g. polypropelene) the differences between caps are more minor; I would go for the cheapest myself and spend the money saved on music.
 
Thanks zener and piglets dad.

I am very grateful for your advice. Before i make a decision on manufacturer i will PM markt . Physical size is important as i will have to squueze the polyprops in somehow. Does it matter if they touch an inductor? Otherwise i may think of putting xover in an external box on back of speaker cabinet.

One more thing, the bennic resistor 11W1R5J - i think i mistakenly said that the resistance was 5 ohms. After looking at my post i think it is actually 1.5 ohms - is this correct? If i can source a wirewound vitreous enamel resistor of the correct values, will it be better than a wirewound ceramic/cement?

Thanks stu . sorry for all the questions (I am learning)
 
1R5 sounds like 1.5 Ohms.

I don't expect a vitreous enamel resistor to be radically better or worse than a ceramic cement, but others may have an opinion based on experience here.

The Bennic resistor is actually on the list of suggested types at http://ldsg.snippets.org/appdx-er.php#RESISTORS, so I can't see much advantage in changing it.

Having the cap touch an inductor is not ideal, but I doubt anything too bad will happen in reality. Can you use slightly longer wires to remotely mount them off the board or teminal strip?
 
Pigletsdad,

Thanks for your response, yes i am sure now that reistor is 1.5 ohms. I will leave it alone and concentrate on the caps.

I will try and devise some method of mounting the large polprops off the cpb- should be interesting working out the best way to do this, but to me that may the most satisfying part of this project if i can do it right.

Many thanks stu
 
zener said:
hopefully Markt will have an answer , as he knows his stuff with regard to crossovers , he can certainly point you toward the suppliers and type of resistors/caps to go for. If he doesnt raise his head , send him a PM....Jon
Click to expand...


Very kind of you to say that Jon, :) I only have experience of one set I've built so far (for SBLs) though I suppose the component substitution thing is universal for the effects they give, I couldn't be sure, I haven't heard these speakers either.

That said, I like the effects air-core inductors bring (nothing to do with saturation?) watch out for correct DCR.

In my crossover I use non inductive planar films with heatsinks, they come in TO220 or TO247 packages at 30W and 100W respectively, the higher ratings really make a difference in my situation, inexpensive too from Farnell and the like, though if you are stuck for odd values then Mouser in the states will sort you out with something from Caddock.

Polypropylene caps are the way to go, the higher the voltage rating the better provided you have space for them.

These experiences were with SBLs so I can't say whether they make any difference to you.

Regards
 
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