Hohm HR01

We try out the debut mic from a new boutique Australian manufacturer.

Hohm HR01There’s no shortage of boutique ribbon mics on the market, but a new hat in the ring is always welcome. The latest attempt to part studio owners from their hard‑earned comes from Melbourne, Australia, where designer Nelson Walkom builds his mics by hand. Two models are available at launch: the HR01 is a mono mic, while the HR02 is a stereo mic with two ribbon motors at a fixed 90‑degree angle.

However, the HR02 is not quite two HR01s stuck together. Blumlein recording requires mics with a symmetrical figure‑8 polar pattern, but the HR01 is deliberately designed to be non‑symmetrical, with slightly different frequency responses front and back. Pioneered by Royer with their R121, this is an increasingly popular approach that can help offer more versatility in typical studio contexts such as miking guitar amps. In fact, the last ribbon mic I reviewed in these pages, the Alder Audio H44, was also an asymmetrical design.

The Long & Short Of It

Ribbon mics generate signal from a corrugated strip of metal foil, suspended so that it is free to vibrate between the poles of a magnet. In ‘short’ ribbon mics such as the Coles 4038 or Beyerdynamic models, this strip is typically about an inch or less in length, while ‘long’ ribbon mics such as the classic RCA 44 have a ribbon about two inches long. Unusually, Hohm describe their ribbon motor as having a ‘medium’ ribbon; at 43mm or 1.7 inches, it’s perhaps closer to the RCA pattern. The motor uses “giant” rare earth magnets rated N45, paired with an output transformer custom‑made in the UK.

The HR01 is visually distinctive, thanks to its tubular aluminium shell which is coated with some sort of gloss finish. The front and back cutouts that allow sound to enter are about 5cm high, and the grille that protects the motor is backed with a layer of purplish gauze that has an attractive iridescent look in some light. The base of the mic houses the obligatory XLR socket along with the discreetly engraved letters F and R. The logo at the top and the position of three bolts also give clues as to its orientation, but in the heat of a busy session, these might still be too subtle! Hohm say that the design incorporates built‑in shock absorption, which is just as well, as the supplied shockmout is a generic type that perhaps shouldn’t be relied on too heavily.

The HR01 is a passive microphone with a nominal output impedance of 300Ω. The specifications give the sensitivity as ‑55dB re 1V/Pa, or 1.8mV/Pa, which should on paper make it somewhat hotter than the Alder Audio H44. In a direct comparison, they often generated very similar levels from the same sources, but any half‑decent preamp ought to cope fine unless you’re recording butterflies landing on snowdrifts.

This graph shows the differing frequency responses for the front (purple) and rear of the microphone.

The spec sheet gives both polar pattern and frequency response diagrams, though these are a bit light on key information. There is, for example, no vertical scale on the latter, but the general trend is clear. Even though the mic was measured at 1m — beyond the distance where proximity effect kicks in — both front and rear responses show a substantial boost below 400Hz or so, which peaks at around 90Hz and drops away steeply below 50Hz (Hohm say that the ribbon is tuned so as to have its primary resonance at 43Hz). Above 1kHz, the different character of the two sides is quite apparent. To the front, there’s a broad peak between 6 and 12 kHz, but turn the mic around, and that response is inverted, with a noticeable dip at 8kHz and a peak at 14kHz.

Hohm Sweet Hohm?

I tested the HR01 on most of the sources where ribbon mics are usually favoured, including electric guitar amps, acoustic guitar, vocals and as a drum overhead mic. The contrast in tone between front and back is obvious, and in both cases, the HR01 has a distinctive character, which was noticeably different from most of the other ribbon mics I compared it with. A lot of modern ribbons, including the R121 and H44, and the excellent Extinct Audio BM9, tend to throw the focus on the midrange. In contrast, the HR01 is more inclined to highlight the extremes of the spectrum, especially when used close up. That low‑frequency boost is especially prominent: even at a distance, it will add weight to any kick drum, and put hairs on the chest of any male vocalist.

The contours of the HR01’s high‑frequency response are also readily apparent to the ear. On drums, for example, cymbals have a noticeably different timbre depending on which side of the mic is used to record them. You don’t get the forward upper midrange that a mic like the R121 will give you to help your overheads cut through: it’s more of a sizzly quality further up the frequency spectrum, and although Hohm say that the rear response should be flatter and “tamer” in the high end, I found this sizzly quality more apparent on the rear side. If anything, in fact, the rear side was a bit too crisp on drums, whereas the front side sounded great.

The contrast in tone between front and back is obvious, and in both cases, the HR01 has a distinctive character, which was noticeably different from most of the other ribbon mics I compared it with.

Of all the mics I dug out to use for comparison, the one that was closest in character was the Rode NT‑R. This has an equally hefty low‑frequency response, and in the midrange and top end, displays a somewhat similar quality to the HR01’s front‑side capture. (Maybe it’s an Australian thing.) The NT‑R is an excellent mic that has an unusually extended frequency response at both ends of the spectrum, but the flip side of this is that if you jam it right up against the source, the low end can be overwhelming. The same goes for the HR01, which likewise benefits from a bit of distance. Back it off from the amp or instrument a few inches, and you’ll be rewarded with exactly the sort of full‑range, smooth tone you’d hope for — and if it still doesn’t quite sound like you wanted, you can just turn it round!

Hohm Run

Building a ribbon mic that has useful frequency response from 50Hz all the way up to 20kHz is no mean feat, and other models that do so tend to be quite expensive. The HR01 is thus very competitively priced, especially considering that it is entirely handmade. The difference in tone between the front and rear sides is enough to significantly increase its versatility, and I was also impressed by its obliviousness to electromagnetic interference. There was no hum or buzz pickup that I could detect at any real‑world gain setting, which can be an important consideration when using ribbon mics on quiet acoustic instruments. All in all, an impressive start for a new mic manufacturer, and I look forward to seeing what else Hohm come up with in the future.