Alder Audio H44

Alder Audio’s debut mic is at once innovative, classy and highly affordable.

In many ways, the ribbon microphone is the quintessential ‘boutique’ product. It’s a fundamentally simple design that is nevertherless amenable to endless modifications and improvements, and the all‑important process of fitting and tensioning the ribbon can’t easily be done other than using skilled human hands. With the popularity of ribbon mics showing no sign of declining, it’s no surprise that manufacturers continue to innovate.

The newest faces in this particular sphere are Alder Audio, an American manufacturer led by Tyler Campbell, and their launch product is a passive ribbon microphone called the H44. This uses a ribbon motor design that has several interesting features. Like most ribbon mics, its pickup pattern is natively figure‑8, but it’s designed in such a way that the front and rear of the mic have intentionally different frequency responses. (If that’s not what you want, Alder also make the symmetrical H44S.) The most interesting development, however, and the one for which Alder Audio have been granted a patent, concerns the ribbon itself.

Hard Of Herring

The functional principle of a ribbon mic is simple: a very thin, lightweight strip of metal foil is suspended between the poles of a magnet. When sound incident from outside causes this strip to vibrate, electromagnetic induction generates a tiny alternating current, which is then passed to a step‑up transformer to generate a more workable output voltage.

The ribbon itself is usually made of aluminium or an aluminium alloy, and for a number of reasons, it needs to be corrugated. This makes it easier to tension the ribbon correctly, increases its effective length and hence increases the sensitivity, and most of all, helps to make it more elastic and thus more durable. A strip of foil 2 microns or so thick is inherently fragile, and if it were simply stretched flat within the frame, the slightest air movement would be enough to break it.

Alder Audio’s key innovation is a new pattern which they refer to as ‘herringbone’ corrugation.

In the large majority of ribbon mics, the ribbon is corrugated in a simple zigzag pattern, which is reasonably easy to do using a toothed gear wheel or similar implement. However, some makers employ a different form of corrugation in which there are a couple of zigzags at either end, but the main part of the ribbon is creased along its length rather than in a zigzag. This allows the entire ribbon to move ‘pistonically’ in response to incident sound, and its advocates claim better sensitivity and other benefits. In both cases, though, rogue air blasts and sudden impacts can easily deform or break the fragile ribbon.

The major design innovation in the H44 is a unique, patented ‘herringbone’ corrugation which is said to make the ribbon much more robust.Alder Audio’s key innovation is a new pattern which they refer to as ‘herringbone’ corrugation. This could be thought of as a hybrid between conventional and pistonic patterns: a single crease runs lengthways down the centre, and either side of it, the ribbon is pleated at a 45‑degree angle, forming V‑shaped peaks and troughs down its entire length. Tyler says that this gives the ribbon an unprecedented degree of strength, and a slightly hair‑raising video on the Alder Audio website shows him blithely applying phantom power, blowing into the mic and dropping it onto a hard surface without apparent ill effect. Yet, he says, there is no measureable or audible sonic difference between his herringbone ribbon and a standard zigzag one.

Ribbon mic geeks also spend a lot of their time debating the merits of different transformers, and it’s worth noting that the H44 uses a toroidal design which is wound by Alder themselves. Toroidal audio transformers are more difficult to make than their conventional cousins, but they do have measureable benefits, making it possible to achieve a given turns ratio with less wire. This in turn means less DC resistance and thus less self‑noise.

In Action

The H44 ships in a small ABS case that looks to offer excellent protection. The only supplied accessory is a simple clip, which unfortunately doesn’t fit in the case. As this doesn’t offer any shock protection in any event, I think I’d always want to use the H44 with something like a Rycote InVision mount. The mic body is machined from a polished piece of steel tube, with cutouts for the grilles and the striking brass logo, while the base houses a standard XLR connector. Overall, the impression is very positive: it looks smart and feels very solid and weighty.

Mention of ribbon mics that sound different front to back naturally calls to mind the Royer R121. As luck would have it I was able to make direct comparisons between the H44 and an R121 in a local studio, as well as with my own Extinct Audio BM9 ribbon mics, and it was immediately clear that the H44 can hold its head up in this company. I was able to compare them on vocals, electric guitars and drums among other things, and although the three mics were usually distinguishable from one another, I rarely found I had a strong preference. The front‑side sound of the Royer always seems to me positively airy for a ribbon mic, with plenty going on in the 5kHz region and above, while the BM9 has a slightly more vintage, midrangey tone to it. If anything, the front‑side sound of the Alder mic was somewhere between the two: it’s bright, as ribbon mics go, but doesn’t have quite the same liveliness as the R121. Alder describe the rear‑side sound as ‘darker’ but it might be more apt to say that it shifts the focus slightly more onto the midrange. This is reflected in the published frequency response, which is broadly flat from 60Hz to 10kHz, with a gentle lift between 500Hz and 1kHz. Even at the rear (no plot for the front side is available), the HF response is down only 6dB or so at 20kHz.

At a specified 1.3mV/Pa, the H44 was noticeably less sensitive than my BM9s, and it presents an unusually high nominal impedance of 700Ω. Tyler says that in his experience this should not be a problem for any decent mic preamp, and I didn’t notice any issues. It was, however, more susceptible to hum pickup than my BM9s, though not so much so as to be a problem in real‑world use. I didn’t feel I could deliberately treat a review mic badly, so I can’t tell you whether the ribbon is really as durable as is claimed!

It’s always great to see a new company making an impact with an original, innovative design, and Alder Audio are doing exactly that with the H44. At the start of this review, I described it as a boutique product, and it is exactly that in all ways bar one. This is a mic entirely handbuilt in the USA, and having tested it, I was fully expecting to visit the website and encounter a four‑figure price tag. Not so: you could buy three of these for the price of a single R121. That, to me, makes the Alder Audio H44 a real bargain.