[Vintagelover]

Hello everybody,

I’m a young audiophile who works professionaly in the electronics/hifi-world for about 5 years now.
The magic of listening to music hit me at a very young age.
I also discovered very young my interest in technical stuff.

Recently I came across the GR Research channel on YouTube.
I really enjoy the easy but honest way Danny explains things.
Ofcourse I couldn’t resist opening my KEF R700 loudspeakers to learn it has indeed some “cheesy” parts, like the way he likes to put it. For this reason I would like to ask your help.

I own these loudspeakers for several years now and I’m very familiar with the way they sound.
As the years went by I did several upgrades to my system, amp and source wise.
So I’ve come to the point where the speakers are the lesser quality part of my setup.

What do I like about the sound?
They have a deep soundstage and a decent level of detail.
They also go fairly low for their size.

What do I not like about the sound?
- Sometimes they can sound harsh, especially within the female voice region.
Sounds like ‘ssshhh’ and ‘tsss’ can come through very bright.
This also is noticable with certain classical music, when instruments like violins kick in.
- The bass in the midlower regions (100-300 Hz) is not quite there. I miss the ‘oemph’.
- Even though they have detail, I would like to identify more the different instruments as well there physical placement.

My room is acoustically treated on the first reflection points and I have spent alot of time with my speaker placement.
The findings that I give you are the ones that keep coming back, no matter where I position them.
 
Is it reasonable to upgrade this crossover?
I know it’s easier for you if I have a schematic, but these are glued in and when I remove them I can’t go back. So I’ll add some pictures and a schematic from the larger version (R900), whoes schematic is very very similar, only some values differ.
The only difference between the R900 and the R700 are the bass drivers (8 inch instead of 6,5)
I will also include some pictures of the binding posts, which will look horrible to you.

My question is: Is an upgrade within reasonable limits worth my while?
Which improvements have the best price/result?

If I upgrade them, what’s the best way to fix the boards back, without damaging my speaker?

I really respect the knowledge here on the forum and would be very grateful if I can borrow a little of it.

Thank you in advance!

Vintagelover

[Vintagelover]

PS Suggestions for high quality parts are very welcome, but I prefer parts that are available in Europe.
In these COVID times availability is really a problem, so some parts may not be easy to get here in Belgium

[richidoo]

Welcome to AudioCircle

There are opportunities to improve the parts quality to increase resolution.

Certainly the electrolytic caps and cement resistors can be upgraded to modern film capacitors and non-inductive wirewound resistors without any drawbacks other than it won't be the original KEF voicing anymore. The Bennic film caps could be improved but modern bennic films aren't as terrible as some other low cost film caps, and I don't know how good the older bennics were. So the improvement there may be be less, but you can probably hear an improvement with modern films, especially if you're willing to spend some money. But while you're in there fiddling with the electrolytics and resistors might as well do all the film caps if you're going for max resolution. I like Jantzen red caps for sound and value but there are many good caps available now at all price points.

The air core coils are probably adequate just as they are. The magnetic core coil on the woofer is a large 22uF, so that will need to remain magnetic core, and the one you have looks fine.

Keep the old parts so you can revert back if it doesn't sound as good with modern parts as you hoped. Good luck!

[corndog71]

At the very least you could try replacing the cap and resistor in series with the tweeter.  You may be able to get matched Sonicaps from Danny or another brand I like is Clarity Cap CMR series. 

The caps in series with the midrange are an interesting choice in values.  One is 1/10 the size of the other which makes me wonder if it’s a bypass.  It might be better to parallel same value caps to reach 75uf and then add a 0.1 bypass.  Here I would suggest Clarity CSA caps as they’re a little cheaper than the CMR but have the same character in the midrange.  The difference is the CSA are not as good in the treble which makes them better suited for mids.

Yet another option is to send one to Danny to see if it needs any optimization.

[rotarius]

I have the R700 and love them.  I also listen to a lot of classical but unlike you, I get a clean string tone.  The issue of slightly metallic sounding vocals happens on a few tracks, you don't have a silk dome to mask that, I attribute that to the recording quality.  I do have the  4db 125hz dip in my room but that's about it.  In room response is great otherwise. 
I really doubt messing with this crossover will improve the things you mentioned.  The smaller R500 were tested by soundstage network and the THD was impressive.   Really great for massed strings.
Look at room acoustics and placement before these mods imo.

[Norman Tracy]

Hello Vintagelover and welcome to AudioCircle. I enjoy that on AudioCircle our community is international and the different experiences and viewpoints that brings.

Regarding modifying your (very tasty) KEF R700 loudspeakers I will vote on the yes go for it especially given you report to be “a young audiophile who works professionally in the electronics/hifi-world for about 5 years now.” In my experience in technology in general and HiFi specifically nothing teaches us faster or expands our knowledge better than going hands on.

Starting with the areas that will yield best improvements per Euro if I had R700s I would go at them in this order:

• Replace all electrolytic caps in crossover with audio quality plastic film. If HiFi specific caps are out of the budget look into Wima MKP range these are available in larger (for plastic film types) values 10-47 uF and of course paralleling will add up the values needed to match the electrolytic being exorcised. If budget does not allow replacing large value electrolytic immediately at least parallel them with 0.1 uF polypropylene film caps
• Use Danny R’s magnet trick to identify ferrous parts in the signal path (#1 suspect binding post nuts and washers) and replace with non-ferrous (likely brass) substitutes. This can vary from getting brass nuts and washers all the way up to audio grade connectors like WBTs.
• Add damping to the cabinet walls. Not acoustic stuffing, mechanical damping that is adhered to the MDF walls of the box. If importing NoRez from GR is too expensive look into the Bitumen panels from jantzen-audio.com. To work the damping pads must be adhered to the box inner walls.
• Replace existing plastic film caps and power resistors with better audio grade components. About time to look at the internal wire and get rid of any that uses PVC.
• Final least cost effective change is replace inductors with identical L values in heaver gauge wire or foil conductors.

As justification and inspiration I am posting a couple of KEF Blade photos. This is from the audio show circuit before Blade went into production circa 2010. Yes it’s the carbon fiber Blade concept speaker. Notice in the second photo when given this generous a budget the KEF designers use an outboard crossover. Thanks to the clear top cover it can be seen when allowed they opt for quite a bit better crossover parts quality than the production budget allows. My train spotting skills are sufficient to identify the caps are ClarityCap (http://www.claritycap.co.uk/) and resistors are Mundorf Mresist Classic (https://www.mundorf.com/audio/en/shop/Resistors/).

[Vintagelover]

I’m really grateful for the very detailed feedback. This gives me food for thought.

I’m aware of the importance of speaker placement/cables/acoustic treatment.
Since I’m very eager to learn I already experimented alot on these subjects.
To finalize this there is an importer whoes products we sell at our Audioshop who will come within a few weeks and help me with the factors mentioned. The guy has decades of experience and sells audio equipement that costs half your house.
I’m really looking forward to his guidelines and insight on my speaker placement and so forth.

After he has come, my next step is probably going to be to change some parts, maybe first in the tweeter crossover.
If I’m satisfied with the results, I might dig a little deeper and change more parts on the MF filter, as well the binding posts, who look really terrible to me.

Everybody has another taste in speakers, but since I work at an Audioshop I’m priveleged to have the oppertunity to listen to a broad range of speakers. The description of the sound impressions I give are with various recordings and in various circumstances.

Is it safe to say the you can take any decent speaker and improve it by replacing some crossover parts with the same value but higher quality? Or is this not correct?
If this is the case, then I can improve my knowledge and offer these upgrades to customers.
What do you think?

@ Norman Tracy, thank you for the insight on the KEF Blades, this sets things in perspective. There’s a lot to improve upon.

[Tyson]

Is it safe to say the you can take any decent speaker and improve it by replacing some crossover parts with the same value but higher quality? Or is this not correct?
If this is the case, then I can improve my knowledge and offer these upgrades to customers.
What do you think?

This is correct, I do it all the time.  Not just speakers either, amps, preamps and DACs all benefit from parts upgrades.

[Vintagelover]

So there is no risk at doing this?

By this I mean risk of changing the sound in such a way it’s not pleasing.
You can bypass all the capacitors by a 0.01 high quality capacitor, without making something harsh or out of balance?
Maybe getting to much high energy or something similar?
This is all new to me, so I rely on your experience.

[Tyson]

I've never had it change the tonal balance for the worse, in fact most of the time it's smoother and more resolving with the use of better parts, as the original cheap parts were causing harshness and cloudiness in the signal. 

The nice thing is that if you make a change and don't like it, it's fully reversible.

[Vintagelover]

Very good.

What’s the common way to mount these filters back into the speaker, fixed without damaging the speaker enclosure?

[Tyson]

Unscrew the woofer and pop it out - that will give you access to the inside of the speaker and the crossover boards.

[Hobbsmeerkat]

There are occasions where parts swaps can cause issues, but it's not super common unless say you need a 10 Ohm resistor & instead get a 10K Ohm resistor.
And some caps can be bright or harsh, but they often just need to burn-in before they settle down, it just depends on the part in question.

Another thing to avoid is anything silver-coated, especially wire. It needs to be either solid copper or solid silver. Mixing them together tends to make the top-end really forward and bright as it offers less resistance to higher frequencies when a cable is silver coated.

In most cases, you're not going to run into these issues, but you're always welcome to ask around the forum if you are not sure how/where to swap out parts.

[Vintagelover]

Unscrew the woofer and pop it out - that will give you access to the inside of the speaker and the crossover boards.

I already dismantled my speakers. But the xo are glued in. How do you guys refix them after the upgrade?

Thanks for the info

[Hobbsmeerkat]

You will either need to screw them into place or use lots of heavy duty 3M adhesive strips. I would at least consider using adhesive and at least one or two screws.to secure it.
No more than 3/4" long to prevent damaging the exterior of the cabinets as the PCB and adhesive will take up some length.

[RAART]

I am just wondering what happened in the end. I do have same speakers and toying with the same idea to upgrade x-over...