Earlier versions of the Grimm sub used a Peerless then Seas woofer. When Bruno Putzeys was still involved, the original iteration also ran a 400-watt Hypex power amp. Today that's still the LS1 sub without motional feedback. What's inside the SB1? "We are still close with Hypex to use 700-watt nCore." By how much has Rob Munning Schmidt's clever feedback scheme lowered his woofer's resonance frequency? Serious sub fans want at least basic bandwidth/SPL specs to predict how low and loud a sub will go in their room. Grimm's design brief was physically circumscribed by the available space beneath their monitor. That means a 10" woofer so two for stereo. Two create a compound 14" cone surface. In 3rd-party mode, one can obviously opt for a single SB1. These are far from modestly priced after all. How much extension vs. SPL can one deliver?

"We rather not divulge the full details of our design choices since it is very hard for non-experts to understand them. This is definitely not a design whose assets can be derived from its part selection. But I obviously can share the resulting specs."

"Frequency response is 20-250Hz ±2dB in half space (floorstanding), the driver's resonance occurs at a low 15Hz with a Q of 0.5. Maximum power bandwidth from 30-250Hz/1m is >96dBSPL for one subwoofer, >102dBSPL for two (the intended use). At 20Hz, max output is 89dBSPL for one subwoofer, 95dBSPL for two."

LS1 without subwoofer.

Grimm's website promises "bass control like you've never experienced before". On paper, superior control sounded awesome. How would it manifest in the seat? After all, what is the sound of stricter control? Before we find out, let's handle the elephant in the porcelain shoppe: price. At €5'600 each and with a pair the default €11'200 recommendation, the SB1 is in-yer-face costly. Grover Neville already swallowed hard in his MU1 review. Let's excerpt from his closing paragraphs: "I'm left then with a difficult proposition… Soundwise the result of Grimm's obsessive FPGA is clear. There was no doubt that the AES output was superior to the USB. But one can have a serious pair of speakers and a competent amplifier for the price of just this one music server. I'm not yet the intended audience… while it was a wonderful sound, it still did not reach anywhere near the level of difference one might hear between speakers, amplifiers or some good room treatment… [this is] a product that demands an experienced audiophile and an experienced ear. It also demands a large pocketbook and fanatical devotion to perfection at any cost… For the true digital perfectionist this could very well be the perfect piece of summit-fi you didn't know you needed. For the rest of us there's many great flavors of beer."

Aside from obvious need to write a profit—dealers and distributors demand their own—the SB1 seems loaded down by a likely licensing fee Grimm must pay RMS Acoustics for their motional feedback tech. Whether a per-unit percentage or upfront lump sum isn't our business. That IP can't be free is simply obvious. Ultra-performance rubber is disproportionately costlier than a set of budget Wanli tyres even though both do the same thing: keep us on the road. But one is public tarmac, the other a race track. Different purpose and experience. Now our elephant had its mandatory acknowledgment. We can let him out of the shoppe back into the Wild West of high-end audio pricing. Next let's restate that the SB1's birthplace is between the legs of Grimm's monitor. Used elsewhere, it has no adjustable low-pass filter or attenuator. This sub relies on an already filtered gain-adjusted signal. Most users with purist 2-channel preamps won't have the needed functionality¹. Meanwhile the HTers whose pre/pros do shall predictably smirk at the SB1's cost/size ratio. For such coin they'll want a Tyrrex or similar Godzilla. So Grimm's SB1 is idiosyncratic; which also was the already seventh word in Grover's review. To remind us of the breadth of the word's many shades, here are some: distinctive, peculiar, abnormal, odd, queer, quirky, freakish, outlandish, extraordinary, uncommon, unique, singular. Pick what best fits your head space for today's challenger. Now we're set to talk performance. That after all is what the SB1 is all about.

¹ If you run Bel Canto's E1X integrated or equivalent E1X DAC/pre, you're in luck however. Their bass management system offers 40-120Hz hi/lo-pass settings in 10Hz increments.