Q AcoUSTIcS concEpT 20 LoUdSpEAkERS

Loudspeakers

‘I have not heard a pair of speakers at the same price that sound anywhere near as good as Q Acoustics’ Concept 20s,’ says reviewer Greg Borrowman

QAcoustics was established less than a decade ago in the UK, but the company that established it, Armour, is the company behind such famous hi-fi brands as QED, Alphason, Systemline, Myryad, Milty, and Goldring. The Concept 20 from Q Acoustics uses the same drivers found in its well-known (and highlyawarded) 2020i design but in this new model, we find them installed in a new ‘Gelcore’ dual-wall cabinet that Q Acoustics claims reduces resonances by an average of more than 6dB over the midrange and more than 10dB at high and low frequencies. The result is a cabinet that Alex Munro, of Armour, says: ‘ allows loudspeaker drive units to simply play the music, unconstrained by cabinet interference.’

The Equipment

The Concept 20’s cabinet is mostly comprised of what the company calls ‘Gelcore’, a threelayer material. The two outer layers are 10mm medium density fibreboard (MDF). According to Q Acoustics, between these layers is a thin layer of adhesive material that bonds the two layers together but never hardens… a kind of ‘non-setting glue.’ The idea is that vibrations in one layer of MDF are not transmitted to the next layer, because the adhesive material absorbs them or—as Q Acoustics’ product brochure puts it—‘ allows the kinetic energy generated by the drive units within the cabinet to be dispersed as heat, preventing them colouring and degrading the speaker’s musical output.’

But in the Concept 20 design, Q Acoustics has taken a further step to reduce vibration, which is to isolate the tweeter from the cabinet by means of a flexible mounting ring. I am a great fan of isolating tweeters

in this fashion, because the performance of a tweeter can be dramatically altered by cabinet vibrations. By way of example, consider this extreme example: To deliver an audio signal at 10kHz, a tweeter dome has to move back and forward ten thousand times every second, and this forward/ backward movement amounts to only a few microns of travel. So if a loudspeaker cabinet is also vibrating at 10kHz (sympathetic vibration caused by the tweeter itself), and it goes ‘backwards’ at the same moment the tweeter’s dome goes ‘forwards’, the dome’s net movement would be zero, so you wouldn’t hear anything at all. It’s for this reason that Q Acoustics is far from being the first to isolate a tweeter from a front baffle… but it must be said that the practise of isolating tweeters from baffles is not yet common, (though is increasingly so in recent months) because of the increased costs involved and the additional difficulties in manufacturing. (When I say that the cabinet is ‘mostly’ comprised of Gelcore, according to Q Acoustics, the entire cabinet is made of Gelcore except for the rear panel, which is a single layer of ordinary MDF.)

The tweeter itself is rated as being a 25-mm soft-dome design, but it has a very wide fabric suspension. When I measured it, I measured the overall diameter, including the suspension, as being 38mm, and the diameter of the dome alone at 28mm. The tweeter operates from a shallow plastic horn and is powered by a neodymium magnet. As noted previously, this tweeter is not fixed to the cabinet, but ‘floats’ in it courtesy of a very flexible soft rubberised surround, which in turn is press-fitted into the enclosure and constrained by the thin metal fascia you can see that surrounds the tweeter and the bass/ midrange driver.

The bass/midrange driver itself is rated with a diameter of 125mm, but the total moving diameter of the driver is 118mm, and the Thiele/Small diameter is 110mm. This puts the effective cone area (Sd) at 95cm². The cone is made from paper pulp that’s been coated with a material Q Acoustics says is made from carbon-fibre and ceramic. This coating is applied only to the front part of the cone: the rear is uncoated. The cone is driven by a fairly large ferrite magnet that has a second, flux-cancelling magnet attached to its rear to enable the Concept 20 to be operated near an old-fashioned CRT TV monitor if necessary. The speaker basket is made from pressed steel. The rear of the bass driver is vented via a rear-firing bass reflex port that is 115mm long, 38mm in diameter and flared at both ends.

The crossover network is a 4th-order Linkwitz-Riley type nominally set for a cross at 2.9kHz. This means it’s quite complex, so it’s much too large to affix to the rear of the rear terminal plate, as is common with many bookshelf designs. Instead, Q Acoustics has mounted all the crossover components on a standard printed circuit board (PCB), which it has in turn mounted to a 10mm section of PCB, which in turn has been glued to the inside floor of the cabinet. The electrical network comprises three inductors (two ferrite-cored, one air-cored), all of which have been properly mounted to avoid magnetic interaction between them, three ‘Spirit’-branded MKP capacitors, two bipolar electrolytic capacitors and three 5-watt cermet resistors.

Q Acoustics recommends you use its Concept 20 stands to support its Concept 20 speakers. These stands use the same Gelcore construction as the speakers, and have a clever cable tidy that tracks up the rear of the stands so you can’t see any cables (at least you can’t until the very top of the stand, where you have to break them out to lead them into the speaker terminals). An administrative error meant that we weren’t supplied the stands in time for this review, but going solely from a photograph I’ve seen of the stands, they look extremely attractive, and would certainly enhance the visual appearance of the Concept 20 speakers themselves, as well as the sound quality… though the choice of using glass at the base of the stand might be contentious in some Australian households.

However, based solely on my eye-balling a photograph of the stands, I would suggest that if you have small children or boisterous animals in your home you should check the stands’ stability by pushing them from front to back while the speakers are perched on top, because they didn’t look too stable in this plane. Mind you, if you place the stands close to a rear wall, that wall will prevent them from tipping too far. I was impressed by the appearance of the Concept 20 stands, but so I should have been, because a pair will set you back $489… almost the price of a buying a second pair of Concept 20s.

If you choose to use your own stands instead, be advised to have a good look underneath the Concept 2, because you won’t find the usual four threaded holes. First, there aren’t four holes, but three. Second, these holes don’t have the standard threaded holes: they’re much smaller than is usual for threaded speaker holes. Because of this, Q Acoustics provides the speakers with flat metal feet, as well as with bulbous rubber feet, should you want to place the speakers

on a delicate surface. Either way, make sure the speakers can be fixed firmly to the stands, either via a hardware solution, or by using a fixative such as BluTac.

The speakers measure 260×240×386mm (HWD) and weigh 12kg. The review speakers loaned to us by Westan were finished in gloss-white lacquer and looked absolutely superb. I figure they’d look equally good (or perhaps even better!) in the other standard finish: gloss black lacquer.

In Use and Listening Sessions

When it comes to connecting the Q Acoustics Concept 20s, you’ll find you have the option of bi-wiring (or bi-amping) them, thanks to the bi-wirable terminals on the rear, which are bridged by two steel rods (technically known as ‘buss-bars’). Although the terminals are multi-way, I found most of the banana plugs I used were rather loose even when fully inserted, and when I tried using wire or pins instead of banana plugs, I could not get the terminals to grip on these while the steel buss-bar rods were in place. After quite a few frustrating attempts I gave up and made four short lengths of wire in place of the rods to bridge the sets of ‘low’ and ‘high’ terminals together, after which I ran ordinary unterminated wire from the amplifier to the Concept 20s.

Without any shadow of a doubt, the high-frequency performance of the Concept 20s was these speakers’ finest attribute. The micro-detailing in the treble I heard was clearly several steps above any other small speaker I’ve heard at anywhere near the Q Acoustics’ price range. You can hear it most particularly when a drummer hits a cymbal then lets it shimmer… not just the sound of the cymbal shimmering, but the way the Q Acoustics delivers the other high-frequency sounds at the same time. It’s as if each speaker had two tweeters per cabinet, one being used for the cymbals and the other for the remainder of the highest frequencies. The effect was uncanny. You can hear this beautifully on the track Lover’s Mask, from Michael Ruff’s album ‘Speaking in Melodies’. This track isn’t only great for demonstrating the cymbal sound: the dynamics are impressive and the precisely picked guitar riffs are delivered wonderfully well by the Concept 20s.

Although the high frequencies were definitely the star of the show, the midrange sound came an exceptionally close second. Articulation of vocals is incredibly precise, and the tonal cohesion is exception, so that there was never any change in the ‘recognisability’ of any singer’s voice, irrespective of changes in pitch. The same was true of instrumental tones, with the timbres of all instruments reproduced perfectly… particularly that most difficult of instruments, the acoustic piano. Here I used a particularly revealing track recorded

Without any shadow of a doubt, the highfrequency performance of the Concept 20s was these speakers’ finest attribute...

by Sheffield, of Margie Gibson singing The Song Has Ended, on which Lincoln Mayorga plays his preferred Mason & Hamlin concert grand. Gibson’s voice has been captured perfectly, with help from Sheffield’s handbuilt valve electronics, and the Concept 20s delivered it perfectly as well. The purity and clarity are extraordinary. The piano sound is also exceptionally good, and you can hear immediately that you’re not hearing the usual Yamaha, Kawai or Steinway, because the sound is completely different. Mayorga reportedly says he likes the ‘ more solid and woody’ sound of the Mason & Hamlin instrument. I don’t agree that it sounds ‘better’ than any of the ‘big three’ pianos, but it certainly sounds different, and it’s all credit to the Q Acoustics Concept 20s that they’re able to reveal the differences so clearly.

Vying for equal second in the performance stakes, however, was the ability of the Concept 20s to frame the sound stage perfectly, both in terms of the location of images across the stage, and also regarding the height and depth of the images created. Depth delivery improved as I moved the speakers further away from both rear and side walls, but I am aware that a ‘well out into the room’ position won’t be used by many, so be reassured that excellent depth cues are present even if the Concept 20s are used close to rear walls. (That said, the Concept 20s are so small and lightweight that it would be completely practical to leave them positioned close to a wall when listening to music casually, as background, and then move them out to a prime delivery position when you’re going to do some serious critical listening.)

I was also impressed by the way the Concept 20s were able to separate the sounds of different instruments, even when many were playing simultaneously. This was absolutely marvellous when listening to the album ‘The Hurting Scene’ by Melody Pool. Pool’s lyrics veer towards ‘stream of consciousness’ rather than any form of rhyme or meter (though many of her songs are ‘standard’ in this respect), but the inventiveness of the lyrics, the cohesiveness of the deconstructed melody lines and the way the music weaves in and around her lyrics are simply amazing.

I personally have not heard a pair of speakers at the same price that sound anywhere near as good as Q Acoustics’ Concept 20s…

This is a fantastic album, albeit occasionally a tad over-produced in the sound department (it was recorded in Nashville), with rather too much layering in the multi-instrumental tracks, but other tracks (notably Substitute) are perfect captures. Whatever, The Hurting Scene is an album that should be in your music library… and if you’d like a second opinion, The Australian’s music reviewer, Iain Sheeden, wrote in that newspaper: ‘ The Hurting Scene is one of the most accomplished debuts by an Australian singer-songwriter for many years,’ in the process of giving her a 4.5 star review.

As you’d expect of such a small loudspeaker system, the Concept 20s were not exactly hard-hitting in the deep bass department, particularly if you elect to fit the port bungs for a ‘smoother’ bass sound—which will certainly be the direct result, but at the expense of the deepest bass. Careful room positioning will certainly aid in delivering bass, but in the end, this is a small two-way design with a fairly small bass/midrange driver and you should not expect miracles. The same is true if you’re one for cranking up the volume. The Concept 20s can certainly be played very loudly, but if you do so for extended periods you might hear the treble ‘soften’ in character. However, whenever you return the volume levels back to ‘normal’, the correct tonal balance will reappear.

conclusion

In its review of the Q Acoustics Concept 20s, the UK Magazine What Hi-Fi said: ‘ For the price, we are very confident that these are the best speakers on the market today.’ I can’t make that same bald claim because unlike What Hi-Fi, I have not listened to every single speaker available on the market today… which is what I’d have to have done in order to make a similar claim (and, no, I don’t think the good people at What Hi-Fi listened to every pair either, but it certainly made for a good quote). However, I can say with confidence that I personally have not heard a pair of speakers at the same price that sound anywhere near as good as Q Acoustics’ Concept 20s… and I am also pretty confident that I’ve never seen a pair that look half so good for even twice the price. Well done Q Acoustics!

Laboratory test Results

Newport Test Labs first measured the in-room frequency response of the Q Acoustics Concept 20 by using a pink noise test signal and measuring at nine differently-spaced points in a grid whose central point was directly on-axis with the Concept 20’s tweeter. The nine traces were then combined to give the single trace shown in Graph 1, and the result is impressively flat and linear from around 130Hz up to the graphing limit of 10kHz. (The response above 10kHz is shown in Graph 2 and Graphs 5 & 6). Over this bandwidth, the fre- quency response fell within a 2.5dB envelope (or ±1.25dB), which is an outstanding result. To look at the finer points, the Concept 20’s response is around 2.5dB down over a broad range of frequencies centred at 400Hz and there’s another 2.5dB dip from 1.5kHz down to 2.5kHz, after which it rises back to being ‘level’ at 5kHz. These dips are just sufficient to give the Concept 20 a sonic ‘signature’.

The high-frequency response of the Concept 20 was measured using a gating technique that simulates the response that would be obtained if the speaker were to be measured in an anechoic chamber, essentially eliminating room effects and reflections. You can see the dip between 1.5kHz and 5kHz that was evident in Graph 1. Also, above 10kHz, the tweeter’s response rolls off very gradually to be 3.7dB down at 20kHz, then 5dB down at 25kHz, after which it rises very slightly to 32kHz, after which it rolls off very steeply to the upper graphing limit of 40kHz.

The low-frequency performance of the Q Acoustics Concept 20 is shown in Graph 4. There are four traces in all: two of the nearfield response of the bass/midrange

driver: one without the port bung fitted (the red trace) and the other with it fitted (the black trace). The other two traces show the output of the bass reflex port when the bung isn’t fitted (light blue trace) and with it fitted (pink trace). You can see that irrespective of the status of the port, the low-frequency response of the Concept 20 rolls off below 130Hz, at 12dB per octave when the cabinet is effectively infinite baffle, and at 24dB per octave when it’s effectively a bass reflex cabinet. When operating as a bass reflex, the increased roll-off is compensated for by the output of the port, which peaks at around 58Hz, slightly lower than the minima for the driver (at 65Hz). In both cases, there’s significant output from the port just above 1kHz… even more-so when it’s unblocked.

Graph 4 shows the impedance of the Q Acoustics Concept 20 for both cabinet configurations. First, I should note that the channel matching is nigh-on perfect, which is indicative of excellent quality control procedures by Q Acoustics, and should be reflected by improved stereo imaging. In the bass reflex mode, the impedance modulus shows the classic ‘double hump’ with the two impedance peaks at 36Hz (20Ω) and 120Hz (24Ω). The ‘saddle’ between the two peaks is centred at 65Hz. The impedance across the operating bandwidth is controlled, falling slightly below 4Ω only at 250Hz, but the bandwidth over which the impedance is lower than 5Ω means that I’d agree with Q Acoustics’ specification of 6Ω. The impedance graph shows the electrical crossover point is at 1.8kHz, but a separate graph (not shown) puts the acoustic crossover at 2.9kHz, as specified by Q Acoustics. The separate test on the low-pass section of the crossover appears to show that Q Acoustics is relying on the natural acoustic roll-off of the bass/midrange driver, rather than using elements in the crossover network. In Graph 5, Newport Test Labs has used post-processing to ‘join’ the in-room pink noise response with the gated response, which it’s done at 800Hz. This measurement shows the Concept 20’s overall frequency response (as measured) as extending from 90Hz to 32kHz ±3dB. In the bass, this appears to be around half-an-octave shy of Q Acoustics’ claim for the Concept 20 of extension down to 65Hz, but because Q Acoustics doesn’t state dB limits, that 65Hz claim could be a –6dB or –10dB point rather than the more usual –3dB point.

Newport Test Labs measured the sensitivity of the Concept 20 as being 86dBSPL at one metre, for a 2.83Veq input, which exactly matches Q Acoustics’ own specification, but is also a little lower than average, meaning you should look at using a fairly powerful amplifier (50–100 watts per channel) to ensure best results.

Overall, I thought the performance measured by Newport Test Labs of the Q Acoustics Concept 20 was excellent.

Newport Test Labs measured the sensitivity of the Concept 20 as being 86dBSPL at one metre... which exactly matches Q Acoustics’ own specification