Kef Concerto Crossover Rebuild

[ftpols]

TechnoDweeb
I updated the crossovers on Kef 104'4, Concerto's and on the 101/2 some time ago.
I discussed with Kef ( they were still around then ) the possibility of replacing the electrolytic capacitors in the mid and treble sections with plastic capacitors. Kef replied that the Kef crossover calculations took account of the electrolytic capacitors series resistence and good electrolytics were recomended by Kef as the replacements. If I changed from electrolytic to plastic capacitor then I was advised to add a resistor in series with each changed capacitor. The value being 1 ohm per 10uf of capacitor. I did that and it worked well.
If you do not include the extra resistors I imagine you will change the crossover frequency/profile.
Don

Many thanks, Don.
Say I change C1 thru C4 in attached schematic for MKPs.

I just need to change R2 (1 ohm->2 ohms) and R4 (6 ohms ->8 ohms)?

Cheers!

 

[Max Martin]

Bump... need an answer on that one too.

 

[adason]

No idea, but i like sreten's post (rip)

 

[system7]

It's very questionable to me whether these capacitor "Upgrades" are even worth bothering with. The 1R per 10uF adjustment looks reasonable for MKP replacing NPE. But it's a lot of cash, and hard to fit the replacements, since MKP is so much bigger. More of a case for buying new 50V NPE types, if you must.

I have been looking at my new/old Wharfdale Shelton XP2.

Usual Elcap NPE types there. I just simmed what would happen if I just replaced with MKP without taking care of NPE ESR resistance changes. The dotted response is with NPE. It all goes horribly wrong!

What does seem to have smoothed things out is turning the bass units 90 degrees and rolling the wadding up and letting it press against the back of the chassis to damp any chassis ringing. It's a good old trick with old bass units, which can sag with age, and rub voicecoil. The sound is very good.

 

[tortello77]

Crossover mods for kef concerto

Hi, I was looking for feedback from alan-1-b, are these the correct modifications for the concerto crossover?
Thank you

 

[TechnoDweeb]

It has been a while since I was here on DIY Audio. Eight years or thereabout. Since then, I have to admit, I chickened out in refreshing my crossover for the Kef Concerto. I liked the sound so much, I put back the Concerto, and just listened to them. I replaced the Kenwood Supreme 500 with a McIntosh MC2205, and then a pair of Klipsch Cornwalls landed in my lap. So the Concerto went to my son where they still reside.

I did get more Kef though. I had been looking for a pair of Kef 105s for my basement system, and I ended up with a pair of 104/2s. Then 2 weeks later, I got a pair of 105s! So suddenly, I had 3 large pairs of speakers in my basement! Too much for that small space, so I did some ABC testing betweem the Kef 104/2, the 105s, and the ESS AMT 1aM. First I let the ESS go. Then, after more ABing, I let the 104/2 go. I still have the 105s and right beside them, I have a pair of Sony SS-G7s. I also have a pair of Kef 103.2s.

I am starting a new project though. I have already started the thread. This time, I don't have any existing speakers to be concerned about. I recently acquired some Electro Voice speakers, and I've decided to build a set of speakers based on the EV Interface D speakers. I was really impressed with another thread here on DIY on redesigning cabinets for the Interface D, and am heading in that direction. With a twist. Instead of using bottom facing and bottom porting 12 inch woofers, I am seriously considering bottom facing and TL porting with the SP15A! It means a bigger cabinet, but hey, I like big speakers! Where else do you get that feeling in the chest when you play music? Stay tuned....