KEF R11 (Non-Meta) with Benchmark AHB2 and Buckeye NC252MP

[youpassbutter]

I have a pair of non-meta KEF R11s. Before buying them, I noticed that professional reviewers generally gave them very positive reviews, while owners posting on audiophile forums tended to be underwhelmed. I first paired the speakers with the Benchmark AHB2 amp and had the same reaction as the owners - they seemed a bit flat and disappointing. When I swapped in JBL Studio 590s which I had recently bought used, I (and others listening with me) preferred the more dynamic JBLs. When I swapped the Benchmark amp for the Buckeye NC252MP, I thought that it significantly improved the R11's sound. So my non-double blind non-volume matched "experiment" has left me wondering - why do so many owners seem underwhelmed by the R11s and why did the Buckeye amp seem to improve the sound over the Benchmark (assuming it's not all in by head)? Is it an impedance matching issue? Does it need a huge number of watts to come alive? Do they need to be bi-amped to sound their best (I haven't tried this yet)? Do they need a sub and a high pass filter to sound their best? Anyway, interested in your thoughts, thanks.

 

[seanhyatt]

I had a similar situation with the R11 and Q900. You need to have an amp that can change impedance well in my experience with these speakers and more power than they recommend.

 

[adhdbluesman]

I can’t comment on your combinations specifically, but I can offer my experience with the non-meta R3. To me, their sound quality at low volumes has always been subjectively pleasing; however, they always seemed to lack until I hooked them to my Sonos Amp (judge away, I love it though). I tried them hooked directly to an X3700H, then hooked to an emotiva BasX A3, then an NAD C275BEE (both amps were connected to the X3700H L/R preouts). I then moved them to my music room and hooked them directly to an NAD D3045, which also gave good SQ but SPL was lacking. Tried them again with the C275BEE hooked to the preouts of the D3045; the results were much better but they were still lacking in dynamics. I just assumed that they were intended to be used nearfield or close-range and was satisfied to use them as such. After all, they did exhibit significant distortion above ~90 decibels when Erin tested them.

On a lark I decided to take the PSB XBs off of my Sonos Amp and try the R3s that way. To my middle-aged ears, this combo sounded the most dynamic and lively. Source is Apple Music through AirPlay 2. The only thing I can think of that made this difference is the Amp’s ability to double output going from 8 ohms to 4. I concur with what seanhyatt says: copious power and good dynamic load handling seem to be important to the KEF R series design.

Apologies if I seem unobjective or inexperienced - it’s because I am! First post here and I saw this thread while searching another topic.

 

[ahofer]

You do need some power. But also, KEF's tend towards narrower directivity which you may or may not prefer. Very neutral, accurate image placement.

Be careful about the "amp's ability to double output", that kind of power presentation is marketing (they lower the 8ohm rating). Just make sure it can deliver the goods at the worst impedance/phase combination in the speaker's measurements. In the R11's case that seems to be only 3.5ohms, and apparently not at the phase trough, so not so bad. Since audible differences in well-designed amps (like the Benchmark and Buckeye/Purifi) are unlikely, I'd chalk this up to the additional power reserves of the Buckeye.

(edited for clarity and responsiveness)

 

[tifune]

I have a pair of non-meta KEF R11s. Before buying them, I noticed that professional reviewers generally gave them very positive reviews, while owners posting on audiophile forums tended to be underwhelmed. I first paired the speakers with the Benchmark AHB2 amp and had the same reaction as the owners - they seemed a bit flat and disappointing. When I swapped in JBL Studio 590s which I had recently bought used, I (and others listening with me) preferred the more dynamic JBLs. When I swapped the Benchmark amp for the Buckeye NC252MP, I thought that it significantly improved the R11's sound. So my non-double blind non-volume matched "experiment" has left me wondering - why do so many owners seem underwhelmed by the R11s and why did the Buckeye amp seem to improve the sound over the Benchmark (assuming it's not all in by head)? Is it an impedance matching issue? Does it need a huge number of watts to come alive? Do they need to be bi-amped to sound their best (I haven't tried this yet)? Do they need a sub and a high pass filter to sound their best? Anyway, interested in your thoughts, thanks.

Surprised there's no more detailed replies here - usually "the internet" can't resist the urge to prove something/someone wrong.

The Buckeye has a little more power overall which could possibly account for your experience. Without a sub, a few extra watts on tap may make the R11's sound "more alive." Very small volume increases, as would be the case with 100w vs 150w amps, can make audio sound "better" even if they're not consciously discernible as volume increases.

Re: JBL vs Kef, your experience mirrors mine and is the reason I would choose JBL/Revel over Kef pretty much every time (I have not heard R Metas but owned all R non-meta at one point). As to what makes for a better dynamic range, in this case we can hypothesize it's the higher sensitivity brought by 8" woofers. But, it's not always that simple - to my ears the F226Be handily wins over the R11 in dynamic range. You have a good amount of data to decide if I'm imagining it. Erin tests for this, but there is some debate around the utility of those tests which is why Amir does not publish those results (if he even runs that test, I don't know).

Re: an amp that can "change impedance well", that issue is long solved with competent modern designs. Neither the Benchmark or Buckeye would struggle in that regard.

 

[voodooless]

assuming it's not all in by head

Don’t assume, do a better more controlled test.

 

[ahofer]

F226Be handily wins over the R11 in dynamic range.

I think the biggest difference is width of dispersion in high frequencies (see early reflections above 2k)

KEF Ref 5

R11 measurements don't have full CEA 2034

 

[ahofer]

Don’t assume, do a better more controlled test.

Yes, it's worth asking whether different amp sensitivity is fooling you - ie you are retaining pre-amp/input volume but one amp is producing greater output.

Benchmark
Input sensitivity (selectable): 9.8V RMS/22dBu, 4V RMS/14.2dBu, 2V RMS/8.2dBu. Input impedance: 50k ohms. THD+noise (1kHz, 80kHz LPF): <–118dB (<–0.00013%).

Buckeye
Input Sensitivity 1.6Vrms. 26db voltage gain.

Which gain setting did you have on the Benchmark?

 

[tifune]

I think the biggest difference is width of dispersion in high frequencies (see early reflections above 2k)

KEF Ref 5

R11 measurements don't have full CEA 2034

That's interesting, I've never heard dispersion mentioned with regard to dynamic range. Can you elaborate, or point me towards some reading?

 

[ahofer]

I've never heard dispersion mentioned with regard to dynamic range.

I wasn't necessarily saying it would correspond to a dynamic range perception. However, the additional treble energy in early reflections might give you more of a sense of dynamics.

If you listen really loud, *distortion* can give you a greater sense of dynamic range as well.

 

[Ron Texas]

I am skeptical of major performance changes when switching out amplifiers unless one was broken.

 

[youpassbutter]

I am skeptical of major performance changes when switching out amplifiers unless one was broken.

You're right - "significant" is probably overstating the difference.

 

[youpassbutter]

Yes, it's worth asking whether different amp sensitivity is fooling you - ie you are retaining pre-amp/input volume but one amp is producing greater output.

Benchmark
Input sensitivity (selectable): 9.8V RMS/22dBu, 4V RMS/14.2dBu, 2V RMS/8.2dBu. Input impedance: 50k ohms. THD+noise (1kHz, 80kHz LPF): <–118dB (<–0.00013%).

Buckeye
Input Sensitivity 1.6Vrms. 26db voltage gain.

Which gain setting did you have on the Benchmark?

Possibly! FWIW, I started with the middle gain setting and then after a while I changed it to the highest gain setting.

 

[uwotm8]

This is how proper amp in correct place makes sound great again
Jokes off, why does KEF doing that in all speakers except Reference line?
I've even made a post in R3 Meta thread. What's the pont, compensation of LF enhancement caused by room? People doesn't seem to like it then

 

[TurtlePaul]

I think that the original Kef R-series had two sticking points which makes people dislike their sound:

1. They have a 1-2 dB shelf up in the estimated in-room response in the tweeter range. This has been corrected in the meta series. A lot of people think brighter speakers have a hifi sound. Maybe this was Kef's compromise to create a hifi sound (smile responses sell, unfortunately).

2. They have bass tuned as an extended bass shelf at -6 dB. This continues to be the case in the new metas. I think that this shelf is meant to lessen the impact of room modes and make the speakers more room friendly. However, in good room the bass is no longer visceral which takes a lot away from the music. This also allows the smaller members of the family, the R3 and R5, to play louder without bottoming out. This should also get Kef a lot of extra sensitivity - normall a speaker with a 6-inch driver tuned to 40 hz flat will have ~82 dB sensitivity.

I think that both of these can be corrected with parametric equalization: a -1.5 dB high shelf at 2.2 khz will correct the former. A +6 dB peaking filter at 45 hz with Q 1.5 will fix the later. That being said, if you are going to fix the bass with a parametric EQ then you should fix the actual measured in-room response, not the predicted response.

 

[youpassbutter]

I think that the original Kef R-series had two sticking points which makes people dislike their sound:

1. They have a 1-2 dB shelf up in the estimated in-room response in the tweeter range. This has been corrected in the meta series. A lot of people think brighter speakers have a hifi sound. Maybe this was Kef's compromise to create a hifi sound (smile responses sell, unfortunately).

2. They have bass tuned as an extended bass shelf at -6 dB. This continues to be the case in the new metas. I think that this shelf is meant to lessen the impact of room modes and make the speakers more room friendly. However, in good room the bass is no longer visceral which takes a lot away from the music. This also allows the smaller members of the family, the R3 and R5, to play louder without bottoming out. This should also get Kef a lot of extra sensitivity - normall a speaker with a 6-inch driver tuned to 40 hz flat will have ~82 dB sensitivity.

I think that both of these can be corrected with parametric equalization: a -1.5 dB high shelf at 2.2 khz will correct the former. A +6 dB peaking filter at 45 hz with Q 1.5 will fix the later. That being said, if you are going to fix the bass with a parametric EQ then you should fix the actual measured in-room response, not the predicted response.

Interesting thanks - I haven't run Dirac on the R11s yet. I'll be interested to see how that turns out.

 

[youpassbutter]

So, another development: previously, I had been streaming music via Volumio (which is integrated into the MiniDSP SHD). Last weekend, I added a WiiM Pro (using SPDIF out to the MiniDSP) to handle streaming duties. The addition of the WiiM made the KEF R11s sound more lively/dynamic. Presumably this would be attributed to the 2 Vrms output voltage level of the WiiM? Similar to people who find passive preamplifiers to result in somewhat boring, flat sound? Or it's all in my head. But, to me, it's another puzzling improvement.

 

[voodooless]

Presumably this would be attributed to the 2 Vrms output voltage level of the WiiM?

No, that’s the analog output, since you’re using spdif, that is irrelevant.

Or it's all in my head.

I’d say that’s the most likely conclusion

 

[youpassbutter]

No, that’s the analog output, since you’re using spdif, that is irrelevant.

I’d say that’s the most likely conclusion

LOL - well, thanks for clarifying that.

 

[Digital_Thor]

I am skeptical of major performance changes when switching out amplifiers unless one was broken.

I agree.... that is how it should be. But I did experience a pretty clear difference in cone and bass control, when dealing with Dynaudio, Focal, B&W and others ( haven't tried KEF), since the passive filter rips the life out of quite a few amplifiers, with its often low impedance dip.

First time I noticed, was with a Vincent SAV P200 amplifiers. My subs (LAT500 - 8 ohm) were literally not playing that deep and the membrane acted like I was connecting a bad turntable or something like that. I then changed it to something like this:
https://www.groundsound.com/H_Amp_XXXV_dual.php
Now the membrane was purely moving according to sound, and I could play much louder and deeper, and never again experienced the drivers getting out of control.
I did not have measuring equipment back then, but the difference was so big, that I lost respect for Vincent, and re-won my respect for how much that little LAT500 could be pushed. And there was not even a passive filter in between, since I ran a little DSP to filter it.

Then it was the B&W 800 Nautilus, the one with 2 x 10" woofers. The owner could not make them play nicely with either Lyngdorf or big Marantz mono blocks. Then I brought the H-amp with me. And those speakers changed character all together. Of course, they still play like B&W with their "signature sound" and bad midrange/tweeter integration. But the bass firmed up a ton, and they suddenly had a bit of "snap" to them. He loved it instantly and bought the same amplifiers for himself, and totally stopped looking for something else since then.

Same story with Dynaudio and Focal.

I can only logically contribute these phenomena to a good driver stage, strong power supply and overall an amplifier that can deliver a high current into low impedance. Because of course there is some good explanation to this.

For fun - and off-topic:
One of my friends ran the Crown K2 warm, so it shut off, while punishing it in his DIY subwoofer setup with 2 x RS390HO drivers at 20Hz. With the H-amp, it just kept going, until he got a little worried, since the cone of the Dayton drivers started to feel warm.