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How peculiar is the audio industry? It’s seemingly segmented by demar-cation lines that, strictly speaking,

should be a fading shade of grey. But some-how, tradition has dictated the boundaries between Pro audio (studio and live sound reinforcement) and home audio be much more unnecessarily defi ned and stubbornly rigid than they need be. Some companies have made a successful transition (in both directions)—Bowers & Wilkins and Bryston come immediately to mind. In general how-ever, the status quo of the compartmental-ised model has held fast, even to the point where several manufacturers offer separate ‘Pro Audio’ and ‘Home Audio’ lines.

Grover Notting, a relatively new Australian professional speaker manufacturing com-pany, may just be another of the very few to break the bonding shackles of tradition.

STUDIO ROOTSFor around four years Grover Notting (GN), under the helm of proprietor and designer Frank Hinton, has been manufacturing high quality professional monitors that have been coveted, and subsequently acquired, by major recording studios around the country. The Grover Notting philosophy is one of of-fering speakers featuring top-notch drivers in designs that can deliver maximum ac-curacy, dependable reliability, and high SPLs

in a no-nonsense discreet physical package. These self-imposed directives are in paral-lel, of course, with long-held audiophile priorities (with the exception of the discreet looks—some designs can be, umm, overt… to put it mildly). These common goals have recently led to Grover Notting making sub-stantial in-roads into the consumer audio enthusiast market, or as Hinton refers to it, the ‘recreational listening market’.

The subject of this review is the Code 4, part of the Universal Series, a mid-sized two-way speaker system with a customised Scanspeak Revelator tweeter and 165-mm diameter Illuminator mid/woofer. The out-standing tweeter (which is used throughout

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the Grover Notting speaker product range) features a number of design modifi cations aimed at reducing distortion, increasing cooling, and improving power output and dynamic range. Similar requirements were met by the mid/woofer, with its massive underhung motor system which has been designed to aid, or ‘guide’, the fl ow of air around the voice-coil and spider.

The proprietary—and copyrighted—fourth order crossover/passive fi lter has been designed by the late Neville Thiele. Yes, that Thiele. Mr Thiele’s contributions to loudspeaker and appropriate enclosure design have been invaluable and Grover Notting’s access to such a wealth of experi-ence has been a real coup for the company. A further element of the crossover is the ‘Bandwidth Extension Module’—an exclu-sive technology licensed by Graham Huon’s Huon Labs (from an original circuit by Ernie Benson of AWA back in 1969) which aims to extend, enhance and control (steep roll-off) low frequencies from a given design.

Frank Hinton backgrounded me on the Code 4 and its design philosophies: ‘I wanted to create a smallish monitor as a reference point. The quintessential near fi eld two-way monitor but different to the usual 50Hz to 18kHz— rolling off at 18kHz is a contentious issue for me—powered with an active crossover—again a conten-tious issue for me—ported enclosure. So after a lot of R&D and about two years of design work we ended up with a sealed box with utmost linearity, crossing over as high as possible into the high frequency device—2.5kHz—and with a narrow 15 degree dispersion for monitoring purposes.’

‘Then when we listened to Neville Thiele’s passive fi lter it was quite superior to any active device we tried. We couldn’t better it. So we ended up with a passive range, which in my opinion is a better option from an engineering point of view. The Code 4 is our closest product to being a totally linear transducer. The Code 4 is the fi rst child of birth… it’s very dear to me as a design.’

The Code 4 bears some striking specifi cations for a two-way of its size. Most impressive is the Code 4’s ability to play at 105dB SPLs at one metre while managing a quoted mid-band distortion (THD) of 0.2 percent. Frequency response has been spec-ifi ed as 38Hz to 32kHz ±3dB with effi ciency being quoted as 86dBSPL while impedance

is stated as 8Ω. The enclosure measures 350mm by 240mm by 340mm (HWD), is made of 25mm Customwood (premium MDF), feels substantial and well-braced, and weighs in at 11.2kg.

As a reminder of its professional studio origins, the speakers feature a chunky Pro Airtight lockable 4-pin speaker connec-tion. With all the speakers, Grover Notting provides its own branded speaker cable (approximately 4–5m) terminated with the Pro connector at one end and bare wires at the other. Although perfectly functional—and the Grover Notting cable looks to be of good Pro-level quality—it’s my personal opinion that this arrangement won’t always be suitable for the audiophile/enthusiast market. I am told Grover Notting is address-ing this issue by way of high quality binding posts in order to allow universal connectiv-ity with pre-existing, often expensive and much-treasured domestic cable systems.

A few words on the aesthetics. The Code 4 was originally designed as a monitoring tool for high-end studios where, of course, looks are not important—its design is plain and simple. Having said that, there’s an elegance about its proportions, its rounded bevelled edges, and its plain black painted enclosure visually off-set by the gold metal badges. Further down the line, Hinton, um, hinted at the possibility of offering veneers as options. But for now, any colour is avail-able as long as it’s matt black.

GROVER GROOVEGN’s NSW representative Robert Hindley de-livered the Code 4 speakers chez Kramers. I used a sturdy sand-fi lled pair of support stands and the Grover Notting cables were hooked-up to my long-term reference valve and solid state amplifi cation. As a side note (not part of the review) Grover Notting also supplied an advanced prototype solid-state amplifi er, the Universal Series Power Plant, which will be offered as part of a growing stable of supporting products for each of the speaker series. The amp bears prom-ise—it has been designed in conjunction

with the renowned Hugh Dean of AKSA Amplifi ers.

I started off with some solid-state am-plifi cation and, right off the bat, the Code 4s displayed a forthright and extraordinarily detailed sound. Living up to their blood line, the Code 4s are an incisive and extremely resolute transducer that can lay bare complex musical strands with surgical preci-sion. No detail is too veiled or unreachably buried within a mix. Take Curandero’s Aras. Although superbly recorded, Miguel Espi-noza’s rapid-blast guitar style, Ty Burhoe’s equally frenzied percussion, Bela Fleck’s banjo and Kai Echhardt’s bass hyper fi nger-ings, and the Ars Nova back-up singers on ‘Segue’ all add up to a potential musical mishmash. The Code 4 separates each strand while unearthing a myriad of low level minutiae that lesser speakers either overlook or confuse. Espinoza’s strings, in particular, are given centre-stage presence

with the underlying fret-buzzing and fi nger-noise becoming a part of the whole per-formance. Ditto for small fi nger and hand incidental scrapes and brushes on Burhoe’s tablas. No doubt by virtue of the driver and crossover quality, the dynamic expression on offer is quite arresting for a speaker of this size. This is an element of the Code 4s that I found prevalent throughout its frequency range; top-to-bottom. For small stand-mounts these speakers are forceful in a way associated with larger fl oor-standers. Bryan Bromberg’s Wood draws out the Code 4s’ low-frequency speed and vibrancy in a way that can make lesser designs seem pedes-trian or downright slow. True, such bass nimbleness can be characteristic of sealed-box designs in general but the Code 4s take bass detail, speed and transient attack to a higher level still. Having said that, in my large room, while excelling at bass swift-ness, the relatively small Code 4s lacked the depth and outright punch I’m used to but, in all fairness, I am accustomed to much larger and more costly reference speakers! Harder large-room punch is available up the Grover Notting line, I’m sure.

The Code 4s are an incisive and extremely resolute transducer that can lay bare complex musical strands with surgical precision.

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GROVER NOTTINGCODE 4 LOUDSPEAKERS

Brand: Grover NottingModel: Code 4Category: Standmount LoudspeakersRRP: $5,990Warranty: Two YearsDistributor: Classic Audio Designs (ATT Audio Controls)Address: 452 Gaffney Street Pascoe Vale VIC 3044T: (03) 9379 1511F: (00) 9379 9081E: julie@classicaudiodesigns.com.auW: www.classicaudiodesigns.com.au

Excellent engineeringSuperb driver qualityExtraordinarily detailed sound

Will sound a tad bright in some systemsMatte black standard fi nishLack of fi nish options

LAB REPORT: Turn to page 84Test results apply to review sample only.

In the last few years there’s been a re-emergence of extreme quality high-end stand-mount speakers—think Magico Mini and its Q1 evolution, the Wilson Audio Duette, the fi rst gen Focal Mini Utopia, and going back a little further, the Sonus Faber Extrema as well as many others. Thrown among those stunning illustrious designs, it may be the ugly duckling in terms of ap-pearance, but in terms of performance—in the appropriate system and room context—the Code 4 can co-exist in the same playing fi eld. But these are profoundly revealing transducers that require a more concerted effort in terms of system assembling and overall synergy. Get that right and the rewards can be substantial.

Professional and ‘recreational listening’ borders? What borders? Speakers sans frontiers… Edgar Kramer

In ‘A Furiosa’, the second track in the Los Angeles Guitar Quartet’s (LAGQ) self-titled release, the lateral soundstage spread and the performers’ positioning were remark-able. The speakers can throw a massive sound fi eld (more so across than aft) with the guitarists placed within the acoustic space with impressive individual separation. In terms of imaging, in particular, the Code 4s are up there with the very best.

As with anything audio, the Code 4 speakers won’t be for everyone. Those look-ing for a lush, over-warm sound that you can passively relax into will need to look elsewhere. The Code 4s demand attention and prompt edge-of-your-seat par-ticipation. They are very dynamic and extremely detailed so system building/matching needs to be conducted intelligently. These are ‘ruthlessly revealing’ speakers—as studio monitors should be—and in a live-sounding room, or a system context that is not complimentary, they can manifest some brightness (but not harshness which in my book is a different thing altogeth-er). Worth noting also is the fact that my reference valve amplifi ca-tion, the superlative Cymer Audio SE-35 fl agship, proved to be a very good match with the Code 4s.

Further amplifi er trials were conducted when, dur-ing the review process, I introduced the Grover Notting amplifi er into the system. The syner-gies between the amp and speakers in terms of imaging and sound staging were obvi-ous. All performance parameters were as ex-pected and the ampli-fi er seemed to handle the speakers without raising a sweat.

CONCLUSIONThe Grover Notting Code 4 speakers are superbly-engineered transducers. They bear the fruits of a talented team of designers; the

overall vision of Frank Hinton, the magic wand of loudspeaker design legend Neville Thiele in the conception of the crossover and, in the exclusive use of the BEM, the in-genuity of Ernie Benson and Graham Huon.

These are profoundly revealing transducers that require a more concerted effort in terms of system assembling and synergy...

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LAB REPORT GROVER NOTTING CODE 4 LOUDSPEAKERS

LABORATORY TEST RESULTSMeasured using standard single-tone

swept measurements in essentially anechoic environments, the Grover Notting Code 4 returned the frequency response shown in Graph 1, which extends from 38Hz to 25kHz ±4dB (ignoring the slight glitch at 16kHz, as will be explained later). The plot is extraordinary for the performance of the bass/midrange driver below 200Hz, which I could only assume was a direct result of the Bandwidth Extension Module’ technol-ogy developed by Huon Labs. This low-frequency performance is shown in greater detail in Graph 3, where you can see that the response of the bass/midrange driver is almost completely linear from 50Hz right up to 1.5kHz, where it’s rolled off by the crossover network (the nominal crossover point being at 2.5kHz). As noted in the caption for this graph, you should ignore the suck-out centred at 900Hz, because this is a measurement artefact caused by using a near-fi eld measurement technique to acquire the low-frequency response. Again, note that the measurement technique used for both graphs (Graph 1 and 3) involves the bass/midrange driver reproducing just one frequency at any given time, whose

level is then recorded and transcribed to the graph, because I will be discussing this later with reference to other tests conducted by Newport Test Labs.

Going back to Graph 2, this shows the high-frequency performance of the tweeter in greater detail, using a completely different measurement technique which, unfortunately, introduces a limit on the lowest frequency that can be captured by the measurement equipment. For the Grover Notting Code 4, the lowest reliable frequency that could be measured was 500Hz, so this is the frequency used for the left-hand end of the graph. You can see that the tweeter’s frequency response extends from 500Hz up to 13kHz within ±2.5dB, which is excellent performance. The tweeter’s response starts rolling off at around 8kHz, so that relative to its output at 8kHz, it’s 8.5dB down at 30kHz (which is the upper measurement limit of the measur-ing microphone, not the tweeter’s output). There’s a dip in the response at 16kHz, but according to the International Electrotech-nical Commission (IEC), the bandwidth of this dip is so narrow that it should be ignored for the purposes of stating the overall frequency response, hence the 38Hz

to 25kHz ±4dB result printed earlier. This is very slightly outside the bounds stated by Grover Notting for both level and frequency, but the differences are so slight they could easily result from differences in measure-ment techniques.

Newport Test Labs measured the imped-ance of both the ‘left’ and ‘right’ Grover Notting Code 4 loudspeakers, and the results are shown in Graph 4. You can see the two traces almost overlay each other, which means the company has good qual-ity control procedures in place. The only substantive difference in the traces occurs at the crossover point, which would lead me to think that perhaps the tolerances of the components in the crossover network could be tightened somewhat, but this is only an academic observation, since the agree-ment between the traces is almost perfect, and the differences would be completely inaudible. The impedance traces do exhibit a glitch at 16kHz which I’d guess is directly related to the glitch noted earlier. Although the impedance remains above 8Ω over most of the frequency range measured, the dips in impedance to around 4.5Ω at 475Hz and again at 5kHz mean that according to IEC guidelines, the nominal impedance

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Graph 2. High-frequency response, expanded view. Test stimulus gated sinew. Test stimulus gated sinew. T . Microphone placed three metres on-axis with dome tweeter. Lower measurement limit 500Hz. [GNC4]

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Graph 1. Frequency response (composite). Trace below 550Hz is the near-field response of the bass/midrange driver. Trace above 550Hz is the gated high-frequency response, an expanded view of which is shown in Graph 2. [Grover Notting Code 4 Loudspeaker]

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Graph 4. Impedance modulus of left (red trace) and right (yellow trace) speakers plus phase (blue trace). [ Grover Notting Code 4 Loudspeaker]

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Graph 3. Low frequency response of mid/woofer. Nearfield acquisition. Note that suck-out at 900Hz is measurement artefact. [ Grover Notting Code 4 Loudspeaker]

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LAB REPORTGROVER NOTTING CODE 4 LOUDSPEAKERS

of the Code 4 should be stated as being 6Ω, rather than the 8Ω claimed by Grover Notting. Nonetheless because the imped-ance remains above 4.5Ω right across the frequency band, and there are no extreme phase angles to contend with, the Grover Notting will be an easy loudspeaker for any powerful amplifi er to drive to its rated maximum SPLs. I say ‘powerful’ because Newport Test Labs measured the sensitivity of the Code 4 design at just 84dBSPL at one metre, using its standard test procedure. This is lower than the 86dBSPL specifi ca-tion stated by Grover Notting, which is a fi gure that’s itself lower than the average (87dBSPL) for most hi-fi loudspeakers. However, as regular readers well know, very few loudspeakers ever reach their manu-facturer’s specifi cation during NTL’s tests, because rather than use a single frequency to measure a speaker’s output, or choose a specifi c octave of frequencies to measure, Newport Test Labs measures ALL frequen-

cies from 20Hz to 20Hz and then takes the average. However, whichever of the sen-sitivity fi gures you use, the Grover Notting Code 4’s effi ciency is lower than average, so you’ll need to compensate by using an amplifi er with a higher-than-average power output.

Graph 5 shows the in-room frequency response of the Grover Notting Code 4, measured using a pink noise stimulus. Un-like single-frequency tests, pink noise test-ing requires the speaker to simultaneously reproduce every frequency in the audio spectrum between 20Hz and 20kHz—something that you’ll never experience in reality (unless you like listening to pink or white noise!), however despite the unreal-ity, the pink noise signal nonetheless more similar to ‘music’ signals than single-fre-quency test signals. So it was interesting to fi nd that using this particular test stimulus, the low-frequency response of the Code 4 was completely unlike the one measured in

Graph 1, rolling off initially at 150Hz where it ‘stepped down’ 5dB to 100Hz, after which it remained at this lower level down to around 50Hz, after which it rolled off again to be a further 5dB down at 26Hz.

I say ‘interesting’ because if you look at the spectral balance of Graph 5, which shows the high frequencies dominating the low-frequencies, this is essentially what was reported as his subjective experience by Ed-gar Kramer in his listening sessions. It’s also interesting because it’s the fi rst time I can recall an instance where the low frequency response measurements have been so dif-ferent depending on the technique used to measure them. In order to show how dif-ferent, look at Graph 6, which shows three different measurements: the near-fi eld low-frequency response (red trace), the gated high-frequency response (green trace), and the averaged in-room response measured using pink noise. You can see that there’s a 7.5dB difference in the two measurements at 50Hz, and that this difference gradually becomes smaller as the measurement fre-quency increases until the two traces start ‘tracking’ each other at around 400Hz.

I confess I have no idea for the reason for the measurement differences, but my working theory would be that it’s some-thing to do with either the Illuminator bass/midrange driver or the Huon Labs Band-width Extension Module, or both. On the face of the measurements alone, I’d guess you’ll hear different frequency balances de-pending on the spectral distribution of the music you’re listening to at any given time, but this is just a guess… so this is one loud-speaker you will be compelled to audition, using exactly the type of music you listen to most often! Steve Holding

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Graph 5. Averaged frequency response using pink noise test stimulus with capture unsmoothed (red trace) and smoothed to one-third octave (blue trace). Both traces are the averaged results of nine individual frequency sweeps measured at three metres, with the central grid point on-axis with the tweeter. [ Grover Notting Code 4 Loudspeaker]

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Graph 6. Composite response plot. Red trace is anechoic response of bass driver (from Graph 3). Green trace is gated (simulated anechoic) response (from Graph 2). Blac Green trace is gated (simulated anechoic) response (from Graph 2). Blac Green trace is gated (simulated anechoic) response (from Graph 2). k trace is averaged in-room pink noise response (from Graph 5). [ Grover Notting Code 4 Spkr]

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