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-   -   KEF Q500 new crossover (https://www.diyaudio.com/forums/multi-way/336219-kef-q500-crossover.html)

wtnsmk 5th April 2019 01:18 AM

KEF Q500 new crossover
 
I've recently upgraded my Cambridge Audio CP1 phono with new caps and op-amps, and I'm so happy with the results, so nothing can stop me now haha...

:Piano:

So I own a pair of KEF Q500 with Cambridge CXA60. Really killer combo IMO.

As I was planning to change the caps to better ones, so I checked online, and everyone is saying that crossover is terrible design.

I tried to find all the content on the internet, but I only find two specifically with Q500.

What I'm planning to do:
  • Change the resistors to Mils
  • Upgrade the film cap to Mundorf MKP or Silver/Oil (this one is crazy expensive, so I'm not sure I will pick this one)
  • Upgrade the big 1000uF cap to Mundorf Ecap or Mlytic? Which one should I chose? Same price
  • Changing the inductors. And this is the part where I'm stuck. What gauge should I use? And what wire? I was checking the Jentzen air cores.

Also Bruce W. mentioned in a comment under a the absolute sound Q500 test the Zobel network. I have no idea how to implement this hahaha :(

Here is a picture with the two sides of the crossover:
q500 crossover - Album on Imgur

Could anyone help me with this? Is there anyone who already did something similar?

Sonce 5th April 2019 02:26 AM

Quote:

Originally Posted by wtnsmk (https://www.diyaudio.com/forums/multi-way/336219-kef-q500-crossover-post5751062.html#post5751062)
everyone is saying that crossover is terrible design.

What I'm planning to do:
  • Change the resistors to Mils
  • Upgrade the film cap to Mundorf MKP or Silver/Oil (this one is crazy expensive, so I'm not sure I will pick this one)
  • Upgrade the big 1000uF cap to Mundorf Ecap or Mlytic? Which one should I chose? Same price
  • Changing the inductors.

If the crossover is terrible design, than do not "upgrade" it with crazy expensive components (with the same values). You will end up with crazy expensive terrible crossover.

Are you sure the crossover is terrible in design? Any measurements?

eriksquires 5th April 2019 02:51 AM

When replacing inductors you should take care to match the DCR of the originals. Don't go willy-nilly lowering them.



For shunt caps, some crossovers can be extra sensitive. Measure ESR and compensate by altering any series resistors.



But yes, the best approach is to analyze the crossover itself first. Make sure you want to replace those parts to begin with, or whether you find opportunities for improvement.

DickHertz 5th April 2019 04:23 AM

Don't change inductors. Caps and resistors are OK, although you might not hear any difference at all. And if you do hear a difference, is it better than the stock crossover?

maty tinman 5th April 2019 08:34 AM

Your picture:

https://i.imgur.com/o49E5ek.jpg


But KEF Q500 Crossover upgrade

https://i.imgur.com/qgDocqh.jpg?1

maty tinman 5th April 2019 08:35 AM

KEF Q900 crossover

http://maty.galeon.com/WP-imagenes/h...-crossover.jpg

wtnsmk 5th April 2019 10:31 AM

I made a diagram of the stock crossover: https://i.imgur.com/GX4WKvb.png

wtnsmk 5th April 2019 10:33 AM

Quote:

Originally Posted by Sonce (https://www.diyaudio.com/forums/multi-way/336219-kef-q500-crossover-post5751091.html#post5751091)
If the crossover is terrible design, than do not "upgrade" it with crazy expensive components (with the same values). You will end up with crazy expensive terrible crossover.

Are you sure the crossover is terrible in design? Any measurements?

I'm not sure in the design, this is the first time when I'm actually trying to understand any crossover. As I said, this is what people say. but I got your point.

Zvu 5th April 2019 10:54 AM

It's better to leave it as is if you don't know what you are doing. Two way crossover is hard enough to get right, let alone three way - that i'd recommend here. 2.5 way is kinda compromised more than it should since the cone of midwoofer is a waveguide for the tweeter. When used as midwoofer, cone moves +/-2mm at normal listening levels so effectively the waveguide jumps around the tweeter and that's not ideal by any standards.

I'd recommend making it a three way with crossover points arround 150Hz and 2kHz. I have measurements of that concentric driver used in Q500 and a crossover at 2kHz yields very good frequency response and directivity caracteristics. Woofer should be measured for ts. It seems to me that it has rather large Qts so they've used large capacitor in series to controll the bass bump.

I wouldn't do any mods prior to:

1.Measuring raw driver responses in factory cabinets at least 2.2m high in air outdoors 0-90 degrees.
2.Measuring woofer TS parameters.
3.Deriving parameters of passive radiators used so i can model the response.

Then and only then, simulated response will match measured one.

chris661 5th April 2019 11:30 AM

It doesn't look like the stock crossover is up to much. 1000uF in series with a PR alignment is crazy to me.

If you're near Sheffield, gimme a shout and we can do this properly, starting with some good measurements.

Chris


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