Need Help - Radford Speaker Crossover

Sansui77

Sansui77

Khosaku Kikuchi's Grandson
Hi All,

Need your advise on what type & brand of capacitors should I use in this crossover as I'm wanting to build for my Bailey's transmission line speakers which use the Kef B139, B110 & T27. Would polypropylene everywhere except the 50uF use 100V NP electrolytic? Also, use all air-core inductors?

Radford-FN10-XO.png

Cheers Mk
 
My Radford Studio 90's have the F11 crossovers that have adjustable resistivities in the treble and mid-range. Otherwise the F11 crossover is very similar to the F10. I built these speakers from kits in 1975 and in all these years I've not changed anything in the crossovers, but I'm thinking maybe I ought to. If you're thinking good quality films for all but the two large electrolytic caps (30 & 50uF), that is what I'm thinking about doing to refresh my crossovers. I agree that bipolar electrolytics would be right. I think air-cored inductors would be the right way to go if you have room for them.

In the F11, the large cap is 60uF rather than 50, and the resistors are different values. I don't know what values the F11 inductors are.

I provided some of the vintage Radford info that is available on T-linespeakers.org.
 
I think you're on the right track. I'd be scratching my head a bit on the 30 uf - would normally use an NPE for size/cost but it's in series with the driver so I might consider a film. Depends on your wallet.

The 5.5 mH inductor is going to be yuuuge if you use an air core. That would be a good place to trim costs if you can stand an iron core.
 
Yuuuge is right! But if there's room, air-core performs better. Good idea to look for a 30uF film cap. Then you'd have just one NPE, and it's not in series with a driver.
 
I had a pair of these with the KEF Concerto crossovers, they sounded great but a little recessed in the mid range, the B110 in the Concerto had it's own enclosure, where in the Bailey TML it's open, I see this crossover is designed to correct this, should be a winner.
 
Speaking of huge inductors, I noticed my recently purchased driver tester gadget and software from Parts Express will do inductance measurements, which is great since my multimeter does not. I'm thinking about winding the next big inductor I need that I can't find in the parts bin. Gotta be cheaper than buying...although you have to find the core, and coated wire...
 
I must admit I do have some handy piece's of gear at my work that I can borrow for the weekend.
We have a few Hioki LCR meters that I could use to wind my own chokes. Wonder if it would be cheaper to buy the coated wire and cores and do it myself??

download.jpg
 
You'd have to price it out. I know I have a link somewhere for plastic bobbins. Not sure where you'd get the wire - wouldn't it be cool if you could DIY the coated wire? I have not looked into that.

Nice piece of gear there!
 
I would recommend Audyn (the red ones) caps, (the 50uFd can be an electrolytic, at least 100V rated), Mills or Eagle for resistors, and air core inductors everywhere else except the 5.5mH in the woofer circuit. You could also consider steel laminate for the 1.8mH inductor in the mid range circuit. If you use an air core for the woofer it will be large, expensive (around $18), and the DCR will be about 1.5 power robbing ohms. If you go to steel laminate the size will be more manageable, cost will be about $8 for a 18ga. wire, .55 ohm DCR. The caps, resistors, and inductors are available from Parts Express. From Erse, you can get the16 ga. steel laminate inductor, in the exact 5.5mH value, .261 ohms DCR, $20 cost. Be sure and use only steel laminate. Avoid iron core as they will saturate much sooner than steel.
 
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Since copper is sold by the pound, I doubt you'll find winding your own inductors is worth the trouble. Been that road myself. Much easier to buy them and adjust the values if necessary by unwinding surplus wire.
 
homebrew said:
I would recommend Audyn (the red ones) caps, (the 50uFd can be an electrolytic, at least 100V rated), Mills or Eagle for resistors, and air core inductors everywhere else except the 5.5mH in the woofer circuit. You could also consider steel laminate for the 1.8mH inductor in the mid range circuit. If you use an air core for the woofer it will be large, expensive (around $18), and the DCR will be about 1.5 power robbing ohms. If you go to steel laminate the size will be more manageable, cost will be about $8 for a 18ga. wire, .55 ohm DCR. The caps, resistors, and inductors are available from Parts Express. From Erse, you can get the16 ga. steel laminate inductor, in the exact 5.5mH value, .261 ohms DCR, $20 cost. Be sure and use only steel laminate. Avoid iron core as they will saturate much sooner than steel.
Click to expand...

Your thoughts, thinking of using these inductors for the midrange & woofer?
http://www.erseaudio.com/Products/IQAll/ELC54-18-1800
http://www.erseaudio.com/ELC54-18-5600

And the rest air-core
http://www.erseaudio.com/EAC15-20-120
http://www.erseaudio.com/EAC15-20-330
 
I haven't used the Erse caps so I can't comment on them. Unfortunately your crossover diagram doesn't indicate the resistance of the 5.5mH and 1.8mH so I'd probably go with the inductors with the lowest resistance. Those would be the ones with the largest gauge wire like 16 gauge. Erse has a 5.6mH value (which is close enough not to require unwinding the coil). This would be the Super Q inductors.
 
homebrew said:
I haven't used the Erse caps so I can't comment on them. Unfortunately your crossover diagram doesn't indicate the resistance of the 5.5mH and 1.8mH so I'd probably go with the inductors with the lowest resistance. Those would be the ones with the largest gauge wire like 16 gauge. Erse has a 5.6mH value (which is close enough not to require unwinding the coil). This would be the Super Q inductors.
Click to expand...

Would the 18ga IQ's be ok as I have to keep cost down?
 
The difference in resistance between the 16 and 18 ga. is about 1/2 and ohm, so that shouldn't be significant.
 
Will update pictures on the build of the crossovers and how they sound once I have install them.
 
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Well finally one xo done. Tested with a Kef B200, Elac mid & IMF TW tweeter to make sure there's no issues. Will be fitting this xo tomorrow and re-lining the internal cavity on the left transmission line speaker and the right will be running a full recapped KEF DN12. I'm looking forward in hearing the difference against the standard Kef xo.

View attachment 1047331
View attachment 1047332
 
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