[MarkoRockvoice]

Hey everyone!

Not long ago, I learnt that KEF (like many other manufacturers) use low-tier parts for the crossovers of middle-class speaker series...
With solid constructed cabinets (MDF with bracings) and the drivers that can perform way better than with the stock crossovers, I started wondering...

I bought a couple of Mundorf caps and resistors, new binding posts and SOMMER cable for internal wiring.

This is the crossover HT/MT board out of the box


This is what it looks like now:


I am blown away by the difference... SO MUCH MORE detail... HUGE soundstage ...


But... I am pretty sure things can be improved further.

For instance, the area around 2.1/2.2 KHz... can sound aggressive (depending on the songs) ... electric guitars... and "EEEE"-vowels can be really annoying.

One thing I have noticed:

With the LS50 meta (which I also own and like) and the KEF references, the crossover from mid to tweeter is at 2.1 KHz (the KEF blade at 2.0 KHz), while the R-Series speakers cross over at 2.3 or 2.4 KHz.
I would love to come closer to the sound of the LS50 Meta (not the old LS50) and the KEF Reference speakers which offer more space and openness in the upper mids.

Measuring doesn't show a peak around the annoying area... but it's there and some albums are not fun to listen to any more...

45 cm distance, on-axis

ANY suggestions are welcome!

- Marko

[Hobbsmeerkat]

Hi and Welcome to AC!

Out of curiosity, what kind of Mundorf caps are those at C1 on the tweeter circuit?
They look like they may Silver-Gold-oil Evo MCaps.

Which could explain the brightness/harshness you're hearing that you weren't before, even if it doesn't show up in measurements. Silver is known to bring out some bright/harsh edges, Plus the tweeter dome is likely Aluminum, and the combination of silver/gold caps with a metal dome tweeter is more likely to cause what you're hearing than if the tweeter was a silk dome.

It may also depend on how long you've had them playing as oil damped caps can require a fair bit of burn-in time. (about 400 hours) when fresh they can definitely sound edgy/bright.

You may want to consider going to a more traditional, but good quality tin-foil caps for that position and possibly bypassing it with a 0.1 or 0.22uF quality copper-foil capacitor (Miflex, Jupiter or Duelund) which will help soften that brightness without the cost or size of a full copper foil capacitor.

As for the lower woofer circuit, I would replace the 100uF electrolytic with a good budget polycap, (Solen, Mundorf etc)
Then with the 330uF, the best option will be to bypass it with a 1uF polycap. As 330uF is a massive value to try to replace with all polycaps unless you bundle three110 caps in parallel hanging off the board.

[JCarney]

As for the lower woofer circuit, I would replace the 100uF electrolytic with a good budget polycap, (Solen, Mundorf etc)
Then with the 330uF, the best option will be to bypass it with a 1uF polycap. As 330uF is a massive value to try to replace with all polycaps unless you bundle three110 caps in parallel hanging off the board.

Solen does make a 330uf cap, and it is the size of a 12 ounce soda can. You could replace it with a Mundorf electrolytic or similar and make gains, as well as bypass it like Hobbs recommended. I rebuilt the xovers in a pair of electrostats that had a 330uf electrolytic like yours. I got the Solens from Parts Connexion with the rest of my bits and pieces, but you could find them elsewhere I'm sure. It looks like at least one of the sandcast resistors is still on the board, replace it as well, you will not be disappointed.

Good luck,
JCarney

[I.Greyhound Fan]

Agree with the burn in and trying some bypass caps.  Also, replace those sandcast resistors with Mills.  They do make a difference.

[MarkoRockvoice]

Out of curiosity, what kind of Mundorf caps are those at C1 on the tweeter circuit?
They look like they may Silver-Gold-oil Evo MCaps.

Yes - correct. These are MCap Evo Silver-Gold-Oil.
The annoying frequencies are still there when I disconnect the HF circuit. I am guessing around 2.1 - 2.2 KHz, which would be consistent with the formants of the vowel "EEE".

That's why I wondered about the crossover from MF to HF since the LS50 Meta and the KEF reference cross over at 2.1 KHz / 2.0 KHz.

It may also depend on how long you've had them playing as oil damped caps can require a fair bit of burn-in time. (about 400 hours) when fresh they can definitely sound edgy/bright.

I will give them a few more hours to burn in and see what it does to the sound.

As for the lower woofer circuit, I would replace the 100uF electrolytic with a good budget polycap, (Solen, Mundorf etc)
Then with the 330uF, the best option will be to bypass it with a 1uF polycap. As 330uF is a massive value to try to replace with all polycaps unless you bundle three110 caps in parallel hanging off the board.

With so much precision and detail in the highs and mids - the low frequencies could use a tighter and more precise character.
I'll talk to my local parts dealer what he has in stock of the suggested ones. Thanks!

Agree with the burn in and trying some bypass caps.  Also, replace those sandcast resistors with Mills.  They do make a difference.

I'll try that.
I never thought that a bypassed parts could make such a difference... Always eager to learn new stuff 

Solen does make a 330uf cap, and it is the size of a 12 ounce soda can. You could replace it with a Mundorf electrolytic or similar and make gains, as well as bypass it like Hobbs recommended. I rebuilt the xovers in a pair of electrostats that had a 330uf electrolytic like yours. I got the Solens from Parts Connexion with the rest of my bits and pieces, but you could find them elsewhere I'm sure. It looks like at least one of the sandcast resistors is still on the board, replace it as well, you will not be disappointed.

Good luck,
JCarney

Wow!
With that size of caps... I will definitely need an external crossover.

As a general approach - what do you suggest:
(a) try to improve the crossovers to the degree of satisfaction
or
(b) take a look at a similar, higher tier, KEF speaker with similar drivers and try to use the design of this crossovers?

[Hobbsmeerkat]

My only concern with a giant 330uF polycap, or a bundle of large caps is size constraints of the cabinet
The modern Kef speakers are very well brace, leaving very little room for such large polycaps.

[JCarney]

My only concern with a giant 330uF polycap, or a bundle of large caps is size constraints of the cabinet
The modern Kef speakers are very well brace, leaving very little room for such large polycaps.

I thought I would post the pic so Marko, and anyone else curious could see it does indeed take up some real estate. I had to go outboard due to the size of the poly caps I choose. Would a Mundorf, or other more audio related electrolytic be a good idea? I did suggest that, but do not want to mis-inform him. You are always very helpful and friendly Hobbs, I want to Thank You for that.

JCarney

[Hobbsmeerkat]

I don't think there will be much difference, if any, between brands as far as electrolytic caps are concerned, unless the are doing something different compared to the majority of electrolytic capacitors on the market. Most times with cheap components, it's just a generic OEM part with a name brand label/jacket slapped on it.
Best bang for buck/space would just be adding a good, budget 1uF poly-cap with the stock electrolytic cap(s).

[JCarney]

I don't think there will be much difference, if any, between brands as far as electrolytic caps are concerned, unless the are doing something different compared to the majority of electrolytic capacitors on the market. Most times with cheap components, it's just a generic OEM part with a name brand label/jacket slapped on it.
Best bang for buck/space would just be adding a good, budget 1uF poly-cap with the stock electrolytic cap(s).

Listen to Hobbs, Marko, not me.

JCarney

[MarkoRockvoice]

Today I was able to compare my modified R3 to the new R3 Meta and the Reference 1:





Although the new META version of the R3 does sound more balanced and open than the older R3... my modified R3 does reveal A LOT more detail and soundstage. Even more details than the Reference 1...
And - compared to R3 Meta my annoying high frequencies are actually even smoother... so I guess I can live with that after some more burn-in-time.

but...

the Reference 1 is an outstandig balanced speaker, easy to listen to... no fatigue... and yet lots of detail.

Plus - the bass with the Reference 1 is tighter, and way more precise.

I wonder if there is something I can do to my modified R3 for a tighter and more precise bass performance.

[Danny Richie]

Although the new META version of the R3 does sound more balanced and open than the older R3... my modified R3 does reveal A LOT more detail and soundstage. Even more details than the Reference 1...

That is pretty typical of crossover upgrades.

I wonder if there is something I can do to my modified R3 for a tighter and more precise bass performance.

Line the cabinets with No Rez.

[maty]

[Tyson]

Yep, NoRez will clean up some of that mess.

[maty]

KEF R300 - 12 Kg
KEF R3 - 13.5 Kg
KEF R3 Meta - 12.4 Kg

KEF Reference 1 - 18.2 Kg
KEF Reference 1 Meta - 18 Kg

[maty]

KEF Reference 1 Meta

[maty]

No Rez, viscoelastic material, bitumen, alubutyl...

and

X-SLS Amateur Build
https://www.audiocircle.com/index.php?topic=185519.msg1948009#msg1948009

[MarkoRockvoice]

Line the cabinets with No Rez.

Sure... but... what is No Rez? Sounds like an absorber material... (sorry if that's a stupid question)

[MarkoRockvoice]

KEF Reference 1 Meta

That looks REALLY good!

If I could get my hands on the crossover schematics, I would use that for the Hi/Mid board. I just LOVE how it never sounds harsh and annoying without losing detail.

if ANYONE has the chance to get hands on the Reference crossovers... Pleeeeeease

[MarkoRockvoice]

There is the muddy, undefined bass that I hear with the R3's (I've heard way worse... but... the KEF drivers can do better than they perform in the R3 I'm sure)

[maty]

I agree. My modified KEF Q100 sounds MUCH BETTER than original. 5.25" Q100 coaxial is very good (better than Q150) but cabinet, front bass-reflex bad design, cheap crossover...

https://www.erinsaudiocorner.com/driveunits/kef-q100-drive-unit/