KEF R500 Review
With all due respect to KEF, the technique, sound, design, and the generally high culture it represents, the next planned tests do not cause much tension. I do not look forward to the nth meeting. KEF deserved such “treatment” and indifference by the high, constant level of its proposals, consistency, or even discipline with which it implements its “program.”
There is no room here for the constructor’s whim, for a side jump, and for generating a construction unlike any other, especially for sound experiments. The improved technique takes pre-determined positions; the principles do not change.
This is very similar to the Dynaudio situation – both the reviewer and the customer can feel safe. These are sounds fixed in the general framework because they are close to objective neutrality.
Is such a sense of security enough – it depends on the individual, audiophile temperament. For some, neutrality and predictability are all they need; for others – a minimum program, only a starting point, and for others – it does not matter because they are looking for something that will move them and move them in any way. But I do not exclude the possibility that the KEFs may also be moved.
- Amazing engineering
- Heavy and refined sound
- Pleasing detail and seamless integration
- Outstanding stereo imaging
- Lack dynamic subtlety of the best
In the tests of the R-series models so far, there has certainly been a lot of excitement due to the powerful bass emitted by the larger R700, especially the R900. No wonder the latter is armed with two 20-cm woofers; they are powerful loudspeakers.
The R700 are more typical – their woofers are 18, while the R500, just matching their price point to this review, have woofers with a diameter of only 15 cm.
This is the smallest floor-standing model of the R series. Still, on the occasion of this comparison, it is worth noting that KEF has developed this series very carefully since it has specially prepared three different-sized woofers for its use. This is not a typical situation today; manufacturers often save money, even by designing many constructions, differing not in the type but the number of woofers or even mid-woofers used in various ways.
On the other hand, in the case of KEF, all floor-standing designs of the R series are subject to the strict rigor of the superior circuit concept, which does not allow for any compromises and is also based on the high specialization of the drivers.
A common feature of all floor Rs is a three-way system, two woofers, Uni-Q module. But the “primal cause” of the configuration used is the symmetry used to create a point source of the sound.
Only then, although it is obvious with KEF, the Uni-Q module enters the system’s center. Because it is two-way and we are dealing with more efficient loudspeakers, it was necessary to expand the system to a three-way.
In this situation, the Uni-Q module is limited to the role of the mid-tweeter (such specialization will certainly not harm the quality of processing in this range). There must be two woofers to create a symmetrical layout – with one above and the other below the Uni-Q.
A design larger than the R500 could be proposed, still symmetrical, using four, instead of two, woofers still of the same diameter. However, KEF chose a more difficult but more effective path. Since all Rs have the same arrangement, they must differ in the size of the woofers.
We used the 18-cm mid-woofers as a standard solution in two-way and two-and-a-half-way systems. We also got used to the 18-cm woofers – they fit the two-and-a-half-way systems with 18-cm mid-woofers. Also, in three-way systems, they do not surprise anyone anymore; they enter because of the tame side of the housing. Examples of such designs in this test are Aria 926 and Chameleon T.
The already mentioned counterpart for them would be the R700. However, woofers with a diameter of only 15 cm are already exotic; there are fewer such constructions, even 15 cm mid-woofers are in the minority.
Therefore, KEF’s consistency, or even idealism, to design three three-way structures of different sizes according to the same recipe has led to a solution that will not enjoy immediate acceptance and the greatest popularity. People will notice that the speakers are smaller than usual, “substandard,” and will suspect that the bass is weaker and less powerful than others. However, these are deceptive appearances.
Volume and bass
Please note that the KEF R500 has the best-extended bass in this test (-6 dB decrease at 32 Hz!). Not even the company’s data promise it, but the results of our measurements leave no doubt. The R700 is even lower, but the R900 is not. It is instructive that it is not a strict rule for the larger woofers to “descend” lower.
Again, the volume (cabinet) of the speakers is very important, and larger speakers require much larger liters for optimal operation. So in some cases, it is easier to get a nicely stretched characteristic by using smaller drivers (in their appropriate and absolute terms, moderate volumes) than large speakers, even in large housings, but in volumes that are not yet optimal for them.
The KEF R500 woofers are small, but the whole structure is already quite “normal” – quite slim, but high and deep as standard, its volume corresponds to the volume of, for example, ProAc Studio 148, in which two 18s operate on the bass (in a two-and-a-half way does not matter here).
The Uni-Q module requires having its chamber, but it is certainly very small, and ultimately the two woofers 15’s work in very comfortable conditions to reach the low cut-off frequency.
Statistically, smaller woofers will have lower power and efficiency, which is the real “cost” of this “miniaturization.” However, the two 15’s can still defend themselves when looking for speakers for “normal” listening to music.
Although of moderate diameter, the woofers in the KEF R500 loudspeakers have a unique, special design analogous to the larger ones in the R700 and R900. These are not speakers developed based on any standard mid-woofers or “specialized” with a larger dust cap – it can be seen in the vast majority of designs.
They were developed from the ground up as low-frequency drivers only, which allows them to achieve such good results in this range. Also, the KEF does not need any mid-woofer in its arsenal because the mids are always processed by having a two-way Uni-Q module. So that is why the work on the converters at KEF goes in other directions.
The Uni-Q module is already the same on all R-series models – there is no reason to change it “at the rate” of the woofer changes; the crossover frequency can always be set conveniently enough for both sections.
Anyway, in all models, it is the same (500 Hz), not very low at all, but low enough not to have problems with the directional characteristics of the asymmetrical system. The small midrange driver is not heavily loaded, and even the 20-cm, and even more so, the 15-cm woofers can easily reach this frequency; there are no puzzles or risky moves here.
KEF R500 laboratory
We have different feelings for companies – some we love the sound that we like perfectly, others we admire for their unusual solutions, we respect others for their technical reliability. However, most often, it is a mixture of several threads.
In the case of KEF, innovation is certainly important, as well as engineering reliability and accuracy, part of which is also a longer than usual table with technical and tactical data (the recommended amplifier power is, after all, “tactical” information). We will also learn about nonlinear distortions (<0.4% in the band 120 Hz – 20 kHz; 90 dB / 1 m), the frequency response is distinguished, defined in the range of +/- 3 dB (46 Hz – 28 kHz) and the “range frequency, “determined with decreases of -6 dB from the average level (39 Hz – 35 kHz).
We will verify this information further, but it is connected with this information policy and the company’s reputation. I am particularly troubled that KEF, in this test together with Focal, belongs to the group of companies that decided not to bother with the old standards regarding determining the nominal impedance. I think you already know what it is about – the design is undoubtedly 4 ohms; KEF describes it as 8 ohms, although in parentheses, he adds that the minimum is 3.2 ohms.
It is still not a very difficult load; there is no need to panic, but the 4-ohm impedance and the moderate sensitivity of 86 dB do not fit tube amplifiers at all, and everyone should learn from simple but real data, not from audiophile data. Opinions drew like a rabbit out of a hat that the X amplifier will not pull the Y columns, although it is unknown exactly why.
The processing characteristics are usually KEF’s “tour de force,” the company’s designers can work out almost perfect linearity, stable dispersion in all directions is helped by Uni-Q, and deviations from linearity are usually planned. In the case of the R500, a characteristic, quite unusual for the general public, but close to the company’s custom, was prepared, with a slightly lowered level above 1 kHz.
While a reduction in the range of 1-4 kHz frequently occurs (in this test by Focal and Sonus Faber), it is usually accompanied by a return of high tones to at least a medium level, and often even their emphasis. Leaving them at a similarly low level is rare; admittedly, in the range of 5-7 kHz, there is a “momentary” reflection, but in the highest octave, the level is low, also on the main axis.
However, it is worth looking at the characteristics from the 30O axis (in the horizontal plane), although it is even lower (from 1 kHz up) – it maintains exceptional linearity up to 20 kHz. There are also no traces of the crossover frequency at any angle, which is an advantage of the Uni-Q module.
In addition, the grille, which is its merit (very thin and has holes profiled on the inside), brings only delicate changes, harmless to the sound.
In the range of low frequencies, we present three curves specific to the various available options for the operation of the resonance system (the “diverging” impedance characteristics are correlated with them). First, the strongest bass (and a decrease of -6 dB at 33 Hz) is obtained at the freely working openings, but not directly because the larger surface radiates more effectively. Still, with it, the system tunes to a higher resonant frequency in the range where the speaker itself, which is the circuit “drives,” plays with a higher level (impedance – red curve, with a minimum at 42 Hz).
The insertion of the rings leads to a reduction of the resonance frequency to 32 Hz (impedance – green curve). The conversion characteristics fall earlier, but more gently, it is possible to maintain a decrease of -6 dB at 33 Hz. This is where the curves intersect; adding “plugs” almost exactly closes the casing (a bit of pressure still comes out of there), there is only one peak left on the impedance characteristic (at 48 Hz, black curve). The conversion characteristic drops so early that the -6 dB drop shifts to 45 Hz – this is an emergency variant.