Hardware Reviews

Grimm Audio LS1/LS1s


The moment four talented minds decide to get together to develop an active loudspeaker system, based on all the knowledge they have accrued, you expect something special. Grimm Audio is a Dutch company established by Eelco Grimm who is experienced in building studios, Guido Tent of Tentlabs is well known for his D/A converters, Bruno Putzeys of Hypex and Mola Mola for PWM amplifiers and last but not least Peter van Willenswaard, for whom analogue circuits and power supplies hold no secrets. They share overlapping knowledge and many years of experience in both professional and home audio. Together they designed the LS1 2-way loudspeaker, or when a pair of LS1s subwoofers are added, a real 3-way system. The LS1 is an active loudspeaker mainly designed for use with digital sources and built without any compromise to be one of the most neutral and distortion free loudspeakers in today’s market, but it still takes care to reproduce music and not gets lost in technical perfection. Another design goal was to make sure that the influence on the listening environment is as small as possible to increase applicability. It sole purpose is stated as: “to create a credible illusion that the original sound source is with you in an average room”. Using smart digital solutions and modern analogue techniques the LS1 is a typical example of form follows function without going to extremes.

The speakers arrive as building blocks, to be assembled on location, the construction starts with the almost square and shallow box that holds the drive units. Large baffles were common in the days when sound quality was more important than appearance and manufacturers seem to have forgotten that a large baffle surface gives a direct sound pattern at much lower frequencies, with fewer reflections on the edges of the baffle. The box is mounted between hemispherical tubes to prevent diffraction. To optimize the radiation pattern of the tweeter the same section is used below the tweeter too. Inside the box real wool is used for damping. For normal use at home the tweeter is positioned at ear height, higher stands are available for studio applications. If the sound pressure of the standard LS1 is not enough for you (volume levels are limited due to the maximum woofer cone movement) put a pair of LS1s subwoofers in place between the ‘legs’. The bass driver faces upwards which isn’t a problem from a sonic point of view but does make a good dust trap.


ls1 dark


Inside the subwoofer a 400 Watt Hypex amplifier drives the stiff bass unit. A pair of 120 Watt Ncore amplifiers from Hypex, positioned in one of the legs, is sufficient to drive the tweeter and the woofer. Any incoming signal first passes through a digital signal processor that deals with all aspects that cannot be physically or mechanically adjusted. Like phase errors, irregularities in frequency response (now straight within +/- 0.5 dB from 30Hz to 20kHz, -3dB point at 20Hz) and radiation pattern. After the DSP and still in the digital domain 4th order crossovers separate the high and low frequencies for each amplifier. When the subwoofer is added, just select 3-way instead of 2-way in the software set-up. PWM amplifiers require an analogue signal, therefor three digital to analogue converters are built in. To keep the D/A converters synchronised a special version of the Grimm Audio CC1 studio word clock is applied. If you want to feed the LS1 with an analogue signal, this has to be converted (by the system) to digital before it passes the DSP and filters, and converted back into analogue afterwards. Do not worry, this detour is compensated fully by the advantages of the system over classical none active loudspeakers. Recommended loudspeaker positioning is rather unusual, 2.5 meters apart with a 45 degrees toe in. That way the listener sits 15 degrees off axis and the speakers’ axis cross in front of the listener, an arrangement calculated to give the flattest response. This position has a double advantage: first, the reflections from the side walls are less important and second there is no real hot spot. This second aspect is important in studios where the engineer has no fixed position behind the mixing console, at home on the couch the sound impression and stereo image is the same wherever you sit. Every pair of LS1 speakers comes with a control box for additional digital inputs and volume control, the volume control works also for analogue signals. A USB box is part of the system, you can connect a computer directly to the LS1 for music playback and to make alterations in the software set-up. In the software choices are amongst others made for 30 or 45 degrees toe in, left/right position, maximum volume level, 2-way or 3-way, behaviour of the system like a small bass reflex (studio purpose), firmware updates and a new loudness setting for those who want to stay on good terms with the neighbours. Last but not least, every LS1 comes with an informative illustrated book on how to set up the system, use it.

To use the Grimm Audio LS1 (plus LS1s in my case) just a single analogue or digital source is sufficient. I use my NAD M50 digital network player with the M52 music vault, positioned next to an outdated Rotel CD player, heavily modified with Tentlabs mods to bring it up to today’s high end level. My analogue source is a Transrotor/SME/Transfiguration combination with a tube phono preamplifier. Because of the fact that my phono amp has no balanced output and I do not want to use adapters or have a RCA to XLR interlink on hand, I run the signal through my balanced Audia preamp switched to pass through. All cables are included in the package except for some Grimm Audio TPM interlinks for analogue use and extra AudioQuest power cables. No separate power amplifiers, crossovers, converters or word clocks are needed.


ls1r remote black


No matter what music you play one property always springs into mind, which is neutrality. Above that the Grimm is ultimately precise, free of distortion over the whole frequency range and very transparent. Only a handful of extreme high end systems will produce the performance of Stacey Kent in such a pure and intense form without turning her CD Raconte-moi into a solely technical and analytical experience. At the same time I realise that other systems hit me deeper emotionally. The lovely voice of Stacey charms me nevertheless, possibly due to the quality of the band and the recording. One thing became quite clear with the LS1, a lot of recordings are lousy or bad these days. The Grimm will ruthlessly point out problems with stereo image, purity and highlight distortion, overblown bass and any other shortcomings. This makes the LS1 a great tool for a recording engineer. From the CD Converting Vegetarians by the duo Infected Mushroom I chose Avratz. This is electronic music with deep bass lines, tantalizing high notes and twinkling midrange. The low end reaches very deep with the LS1s subwoofers in place and has considerable slam. At the same time bass definition is excellent and always fits into the complete picture. Drums are well positioned over the bass, but less widely spread over the soundstage than other, more conventionally positioned speakers. It is a wall of sound, wide, deep and high, but always between the speakers. This must also be due to the lesser reflection of the side walls. However, every detail is projected into the room with amazing ease.

From the imposing Avratz to the tender Noctures of Chopin, played by François Chaplin and digitized into a high resolution FLAC file, what I really appreciate and what I see as a signature of the A/D converters, is the fact that the higher notes stay exactly in place, while the lower registers do the opposite and flow around as you would expect. It sounds easy to do but a lot of digital converters blow up a grand piano to abnormal dimensions on high notes. On the other hand I would again like to experience more romance and emotion in this part. Maybe, I admit, maybe I miss some of the harmonic distortion that’s normal with more conventional amplifiers or even tube amps. Precisely what a pair of golden ears said on hearing the LS1 at my place. We are so used to distortion that the absence is a strange experience. Please allow me to make the following comparison: we find clean, fresh and pure bottled water to be tasteless after drinking sodas. But if we were used to only drinking bottled water we would find a soda too sweet and too sticky. I would love to hear what the LS1 would do with the PWM amps changed to class A solid state or tubes. Grimm, Devialet, NAD M2, Hypex, Pink Faun etc are all based on PCM/PWM technology, I would rather have Audia, Pass, PrimaLuna or Manley for that matter; traditional amplification with today’s technology inside the box.

Different from Chopin but in the same vein is the lovely song Be Careful It’s My Heart by Holly Cole. I played the ripped FLAC file as well as the original CD and LP version. Three versions with the same sort of impression: rich in detail, well positioned, full of nuances in her voice, unmistakable Holly Cole. Still it never brought a tear to my eyes. Even though she seems to be in my living room in front of me, and I feel I can almost touch her, she keeps her distance and does not sing especially for me. Could I live with this omission, probably not. It’s a matter of taste and preference that has more to do with me and what I want than with the LS1 or any other part of the system.


press grimm ls1 connectors leg vert1 grimm

Back to music. Janine Jansen plays a composition of Debussy on her CD Beau Soir. To reproduce her passionate playing with so many nuances is reserved for only a handful of the best loudspeakers. Amongst these is the Grimm, pure and transparent in the extreme, every single note surrounded by glory. The softest note equals the loudest passages in intensity, at the same time dynamics on the Decca recording are never limited, on the contrary these dynamics could only be bettered by inviting Janine into your home for a private concert. Searching through my music collection is made easy with the app from NAD and I come across an old demo CD from a Dutch band called Velvet. The recording was made in a simple studio and shows another strength of the Grimm. Where most loudspeakers try to recreate the space, the Grimm puts you right into it. With an open playing bass, piano and a female vocals. Pure, artless, sober and fresh. In one word magnificent and a pleasure for my ears. Excuse me opponents of ripped CD and FLAC files, I have to disappoint you all if you think the original CD would still be better. The modified CD player is not better with this music, neither with a CD made by Jacintha, it is different, not better, not worse. That shows that the lack of emotion has nothing to do with streaming.

However, the room effect does seem to be critical. During Grimm’s 10th birthday celebrations at the High End Show in Munich 2014, we listened to the LS1 plus LS1s for some time. In this room toe in was only 30 degrees. The transfer of emotion towards the listeners was no problem at all. In the much larger demo room a lot of people sat down looking very satisfied. The LS1 showed that more required volume was no problem at all for the system. Music was played direct form a computer into the USB interface of the LS1 and if time would have permitted we would have stayed a lot longer. In classical, pop music and easy listening jazz we recognised the transparency heard at home.

Next to the digital input there is an analogue one for those who play vinyl or tape. The opportunity for me to play my own records through my phono amplifier and preamp via pass through from RCA to XLR, volume control is on the LS1 only. The Academy of St. Martin-in-the-Fields makes me happy with some parts of the Brandenburger Concerts. Just like it was with digital, the amount of detail along with the ultimate transparency add to the experience. While the subs rumble from the groove noise between tracks. Rich dynamics show no trace of hardness, and if there is hardness it comes from the violins themselves. Since the music is in front of the listener but kept at a distance, the illusion of the concert hall stays intact. The stereo image is not as wide as I am used to, it stays between the loudspeakers, the same as it was with digital reproduction. From these old recordings to new ones, from baroque to the soft jazz of Diana Krall. Her Wonderful floats tenderly into the room, with I have to admit more feeling and emotion than digital could deliver. It shows that vinyl cannot be beaten, although a nasty scratch also shows that records have their issues too. Since the Grimm leaves nothing out, nastiness is projected into the room as well. Before Krall and long after Bach, recordings were made of Dire Straits. On The Best of Dire Straits from 2005 we have a reissued version of Brothers In Arms. Music considered by a lot of audiophiles to be among the best to review audio systems. No wonder, when played on the LS1 the guitar of Mark Knopfler weeps and percussion ticks with the accuracy of Swiss clockwork.


ls1 in living room 8


IF, THEN, ELSE, statements from the programming language Basic spring into mind. IF you decide to buy a pair of Grimm Audio LS1, be assured that you are getting an outstanding product, good enough to serve as a mastering tool in many studios, but recently embraced by music lovers at home too. THEN you get yourself a 3-way system with: A/D conversion, DSP, DSP crossover, three D/A converters, three power amplifiers, an outstanding digital clock for each channel, and a control unit. Together they form one of the best systems available today, with an outstanding price to quality ratio. A system so free of distortion and so neutral that you might have to get used to it. ELSE you buy yourself a stack of boxes, each adding some influence to the sound and sound quality, with more overall distortion and far more variables to alter the original recording. Grimm Audio is almost alone when it comes to bringing you a system where the manufacturer is able to coordinate every aspect of the system. I bow to the four guys who together not only came up with the idea but also the know how to realise a project this complete and intriguing.


Frequency response: 55Hz-30kHz +/-0.5dB.
45Hz-40kHz -3dB. (Low corner is user-settable between 35Hz and 100Hz, Q=0.7 or 0.5)
Deviation from minimum phase +/-2º
Amplifier power: 2x120W
Max SPL: 109dB/1m
SNR: 114dB (unweighted)
Crossover function: 1.55kHz LR4, sum corrected to minimum phase.
Latency: 2ms
Internal volume: 14 litres
Height: 1450mm, 1150mm available on demand.
Width, depth: 520mm x 160mm

Linear response down to 20 Hz
Turns the LS1 into a powerful 3-way system
DSP controlled frequency curve
Phase corrected crossover at 70 Hz
Peerless woofer and 400W class D amplifier

Price when tested:
Grimm Audio LS1 2-way €18,000
Grimm Audio LS1/LS1s 3-way €25,000
Grimm Audio TPM interlinks, 2x3m balanced €735
Manufacturer Details:

Grimm Audio
T +31 (0)40 213 1562


DAC, active loudspeaker and subwoofer


René van Es

Distributor Details:

Purité Audio
T +44 (0)20 8815 5878

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