Floor Loudspeaker Reviews

Because every LS1 midrange driver and tweeter is measured during manufacturing, then precision-matched to the amplifier that powers them, the Grimm crew says that users should make sure that the serial number on the speaker is the same as the serial number on the speaker leg containing the electronics. Easy enough—though I will say that connection-wise and web-interface-wise, inaugurating this system was quite a bit more complicated than hooking up other powered speakers I'm familiar with, including the KEF LS50W, SVS Prime Pro Wireless, and Vanatoo Transparent One Encore. The Grimm system is also more sophisticated in just about every aspect, partly because so many parameters can be altered via either the MU1 web browser control page, or the LS1 Control software when using the LS1i USB interface. (Side note: You'll be highly dependent on that software interface because no wireless remote control comes with the system currently (footnote 4). Grimm will include one in the future. I believe that's wise.) My advice is to just work through the company's extraordinarily informative PDF documentation slowly and methodically. You'll figure it out. I did, with only a small amount of trans-Atlantic handholding by the Dutch mothership.

New tech meets old
One thing that piqued my interest in the Grimm speakers is that they're a rare amalgam of cutting-edge technologies and two almost forgotten ones.

Let's start with the cabinet dimensions. Speaker enclosures in the 1930s and '40s were often flat but wide. That's also true of the LS1c. The wide baffle pushes the baffle-step frequency under 250Hz. What does that mean? Below the baffle step transition frequency, sound radiates equally in all directions. Above, the sound is forward directed. So a larger portion of the energy is directed toward the user at the higher frequencies than at lower frequencies—something the crossover (analog or digital) must address. It also means fewer reflections from the front and sidewalls, which result in phase errors. According to Eelco, "Psychoacoustics says that the ear is sensitive to phase errors down to approximately 250Hz. The LS1s' wide baffle helps attenuate interfering reflections throughout that whole range." The approach comes with a bonus, he says: A wider baffle makes it possible to use a shallower cabinet. "The shallow cabinet moves the resonance along the depth axis inside the box significantly above the crossover frequency of the low-frequency driver. This serves to avoid boxiness."

The other almost-forgotten technology used in the LS1c system is motional feedback on the (optional but recommended) upfiring SB1 subwoofers. Motional feedback was pioneered in the 1970s by Philips in Eindhoven, Grimm's home base. An acceleration sensor is mounted on the cone to record its excursions and vibrations, which can then be corrected as needed. Grimm says that by adding such advanced digital processing and current drive, the already low distortion of its aluminum woofer is reduced by as much as 30dB. One of the company's luminaries, Rob Munnig Schmidt (footnote 5), has published a series of white papers on motional-feedback subs, available on the Grimm website (footnote 6).

Grimm Audio sells the LS1c as a two-way system without the subs ($25,250–$31,400/pair, depending on material and finish), or as a three-way with a pair of SB1s ($12,750 extra). Adding the subs extends the response down to a claimed 20Hz and increases the attainable loudness. Grimm Audio says that adding the subs lowers the intrinsic resonance of the system to 15Hz—below the range of human hearing.

Cool, calm, and connected
Now, how do you get music into the LS1c? You could just connect a CD player, phono front-end, or streamer-DAC to the analog input at the bottom of the left speaker leg. There's an AES3 input for digital connections in the same location, so you could also hook up a CD transport. Users in the pro market are more likely to connect their workstation using Grimm's LS1i USB interface (or the pro-oriented UC1 USB interface) with the LS1r wired remote controller (footnote 7); home users can use the USB connection of the LS1i to connect a streamer, server, or computer music source.

Perhaps the best and easiest way for a home user is to employ Grimm's MU1 streamer, which is intended as an LS1 companion. Just connect the supplied RJ45 cable from the MU1 to the LS1. This was the option I chose, since Grimm had supplied an MU1, and I had familiarized myself with it and its sound in the months before the speakers arrived.

Switching between sources can be done with LS1 control software (assuming a USB connection from a computer) or the wired controller. The Grimm folks say that this (plus the volume control) eliminates the need for a preamp in the system. Eelco Grimm observed that "sometimes classical hi-fi components don't match perfectly. Impedance matching can be wrong. People try all sorts of cables and combine preamps, amplifiers, and speakers of different brands searching for the magic combination." With the LS1, he says, it's the opposite. "The signal path is as short and pure as possible, and all elements of the system are selected for an optimal joint performance. It's our way of minimizing all coloration."

Before we get to how the LS1c system sounds, here are some key technical features of the rest of the system. Digital input signals are reclocked via ASRC (Asynchronous Sample Rate Conversion). Analog inputs are first switched to digital with a high-performance A/D converter; then the signal enters the DSP, which Grimm Audio says has "a data path 48 bits wide with a 76-bit accumulator." The DSP handles volume control and much more. Each driver gets its own D/A converter. The output of those converters is fed directly to 120W Hypex NCORE power amplifiers, known for low harmonic distortion, high linearity, and top-notch transient response. Meanwhile, the SB1 subs are powered by their own 500W Hypex amplifiers.

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Footnote 4: Grimm does supply a wired remote for setup and basic operation; see below for more details.

Footnote 5: See rmsacoustics.nl/activecontrol.html.

Footnote 6: See shorturl.at/1VyCk.

Footnote 7: As previously mentioned, the LS1c doesn't come with a traditional wireless remote control, but because the LS1r is programmable, you can use a remote control you already own to ... control the LS1c's remote control. Got that—Jim Austin