HEDD Audio Type 05 A-Core

HEDD’s new A‑Core range sees the company return to making all‑analogue monitors — and the results are impressive.

Back in 2017 I reviewed HEDD Audio’s debut offering, the Type 07 studio monitors (SOS March 2017). Although they could be fitted with a range of digital interface cards that allowed for direct AES3 and various audio‑over‑IP connections, they were otherwise pure analogue monitors.

By the end of 2020, the Type series had evolved into their current Mk2 guises, with pretty comprehensive onboard DSP (including a zero‑phase Lineariser filter), analogue and digital inputs, and the choice of sealed‑box or reflex‑port operating modes. My colleague Phil Ward wrote a magisterial review of the Type 07 Mk2 in SOS October 2021, and summarised it as “a seriously high‑performance nearfield monitor”.

Now, in 2025, HEDD Audio have gone back to their roots by releasing entirely analogue reworkings of those Mk2 speakers. These new monitors are called the Type 05 A‑Core and the Type 07 A‑Core, and pair the Mk2’s cabinets, AMT (Air Motion Transformer) tweeters, custom honeycomb woofers and twin 100W analogue ICEpower Class‑D amplifiers with newly designed analogue filter boards.

For this review, HEDD Audio sent over not only a pair of the brand‑new Type 05 A‑Core monitors, but also a pair of the current Type 05 Mk2s, which remain in production. Since the only differences between the A‑Core and the Mk2 versions are the former’s analogue filter boards and the latter’s DSP boards, this made for an interesting comparison that we’ll come to later on.

Meet The Maker

Berlin‑based Heinz ElectroDynamic Design (HEDD) have a 50‑plus‑year back story that is pretty unique in our industry. Physicist Klaus Heinz, the son of Physics Nobel Prize laureate Ernst Ruska, first became interested in loudspeakers while at university. After graduating, he opened a high‑end hi‑fi shop in Berlin, which in turn led to an encounter with a loudspeaker by US company Electrostatic Sound (ESS). That loudspeaker, the AMT1, was the first to utilise the original, rather bulky, dipole AMT (Air Motion Transformer) tweeter, which had been invented in the 1960s by the late German‑born American physicist and inventor Oskar Heil (1908‑1994). The sound quality of that original AMT (which is still available from ESS as the I‑Large) made such an impression on Heinz that, in 1985, he travelled to the US to study under Heil. There, he refined Heil’s AMT design to reduce its overall dimensions to those of a conventional high‑performance tweeter and improve its reliability. In 1999, Heinz founded ADAM Audio, a company whose reputation and success were built on the back of his ART (Accelerating Ribbon Technology) and X‑ART tweeter refinements of Heil’s AMT. At the time, that style of ribbon tweeter was unique in the studio monitor market.

Heinz stepped down from ADAM in 2014 and, together with his son, musicologist Dr Frederik Knop, founded HEDD Audio in 2015 in order to continue his development of the AMT concept. HEDD Audio now produce three HEDDphones (yes, they went there), six studio monitors, two subwoofers and the giant, and reassuringly expensive, Tower Mains monitors.

AMT Overview

All HEDD products — including the HEDDphones — feature Heinz’s latest refinements of the AMT design. In simple terms, an AMT tweeter is an electromagnetic transducer that uses a pleated diaphragm to push and pull air in and out of the folds. The resulting airflow moves approximately four times faster than the surface of the tweeter itself. This speed delivers an accurate performance accompanied by low distortion, which results in a smooth and detailed high‑frequency performance across a bandwidth that can extend from under 2kHz up to 40kHz.

The HEDD AMT’s diaphragm is made of Kapton polyimide film (think space blanket without the silvering), with an aluminium circuit pattern etched on it. In a fully assembled AMT, the diaphragm (hand‑folded at HEDD’s Berlin factory) sits inside the strong magnetic field generated by a neodymium magnet. When an alternating current is passed through the printed aluminium circuit, that current generates a varying magnetic field which interacts with the static field from the permanent magnet to generate a force (the Lorentz force, which is the same force that moves a loudspeaker’s voice coil), causing the space between the folds to compress and expand in response to the positive and negative swings of the alternating current.

Incidentally, whilst the folds in the AMT tweeters designed for HEDD’s loudspeakers are uniform in shape and depth, those in the HEDDphones vary in both these dimensions. This variant — the Variable Velocity Transform, the second generation of which debuted in the HEDDphone TWO — enables the HEDDphones to reproduce frequencies from 10Hz‑40kHz.

A Time To Look

From the front, top, bottom and sides, the Type 05 A‑Core appears to be virtually identical to its Mk2 ancestor: same construction, AMT tweeter, 5‑inch custom honeycomb woofer, and port openings. The only visible difference is that the company logo has been reduced in size and now fronts a momentary push‑button that switches the monitor in and out of standby. As on the Mk2, the three‑LED indicator panel shows green for active, white for standby and red for overload. And, again as in the Mk2, the cabinet is, for all practical purposes, entirely devoid of resonance.

At the rear of the cabinet, the Mk2’s DSP control panel, balanced XLR analogue input and AES3 input and output XLRs have all disappeared. In their place sits a largely empty space containing a ±12dB volume knob flanked by smaller ±6dB shelving bass and treble controls, an unbalanced ‑10dBV RCA phono input and a balanced XLR/jack combi socket, plus an input selector switch.

With no DSP on board, the Type 05 A‑Core lacks the Mk2’s control panel, but adds analogue high‑ and low‑frequency shelving filters.

Internally, the twin ICEpower 100W analogue Class‑D amplifiers are fed by what HEDD describe as their “most sophisticated and reliable analogue filter board to date, allowing us to tune every speaker to the most natural response and create a flawless, low‑latency analogue signal path”. This I took to mean that it has been designed to allow HEDD to tune the A‑Core in the analogue domain to deliver an audio performance as close as possible to that of the SHARC DSP‑tuned Mk2 — which is no mean feat.

When I checked with Dmitry Gregoriev (Head of R&D at HEDD), he confirmed that that was indeed the case. To paraphrase Dmitry’s lengthy and detailed response to my question, careful design and component choice were key to ensuring that no additional distortion artefacts are added to the filtered signal, which translates to cleaner reproduction of fast transients and a higher detail retrieval. This careful approach also allows the Type 05 A‑Core to achieve very similar signal‑to‑noise ratio and total harmonic distortion performance to that of the analogue pathway in the Mk2’s DSP board. As a result, the listener’s perception of detail, transient response and resolution should be very similar across the two models.

A quick specification check would appear to confirm my thought and Dmitry’s reply. The monitors’ specifications state that, for both the A‑Core and Mk2 variants, the Type 05 delivers 112dB SPL per pair at 1m. In terms of frequency response, the A‑Core ventures 2Hz lower in the bass than its digitally driven counterpart at 43Hz‑50kHz (though no qualifications are given). Crossover points are specified at 2.5kHz for both. Since the Mk2s’ sealed‑box mode requires special filtering from the onboard DSP as well as physical plugs for the ports, this is not available on the A‑Core.

A Time To Listen

Having set the A‑Cores and Mk2s up next to each other in a 1.25m equilateral triangle with my listening position, I listened to them both daily for a couple of weeks — not so much to run the monitors in, but more to get my ears accustomed to them.

Once I felt happy, I experimented with the A‑Core’s shelving room adjustments which, although effective, turned out to be unnecessary in my room. As I usually do, I began with deadmau5’s classic EDM album 4x4=12. The opening track has serious amounts of detailed bass and sub‑bass content that will test the low‑end response of any loudspeaker to its limits. I wasn’t expecting the A‑Core to produce anything in the sub‑bass region (spoiler alert: it didn’t), but what it did do was to produce a superbly controlled, punchy and detailed performance in the bass, low‑mid and midrange areas, which was accompanied by a clear, open and smoothly precise reproduction of the track’s upper‑mid and high frequencies. At my normal 85‑90 dB SPL monitoring level, there was no discernible port noise, even though there was a relatively large volume of air moving within the ports due to the high level of low‑frequency information in the track.

A new addition to my list of test CDs is Ian Stephenson’s recently‑released Return From Helsinki. Superbly recorded through the vintage Cadac J‑type in Simpson Street Studios in Northumberland, this highly detailed and often extremely delicate recording features instruments ranging from a restored 19th Century church pipe organ, drums, double bass, guitars, fiddles, melodeons, whistles and Northumbrian pipes all the way to a Swedish nyckelharpa. This album examines a monitor’s ability to distinguish between different acoustic instruments sounding in the same octaves and place them precisely in their allotted positions in the stereo soundfield — an examination that the Type 05 A‑Core passed with flying colours.

A favourite CD of mine is the SACD Spes by the Finnish women’s choir Cantus with Frode Fjellheim (vocals and keyboards). Recorded in a large church in DXD/352.8kHz, this extremely detailed recording features soaring ensemble singing that stands in magnificent contrast to Frode Fjellheim’s gruffer tones. Reproducing the detail of the choir’s and soloists’s vocals and the resulting natural reverb tails as these fade away in the high‑ceilinged nave of that church is no easy task, but one that the Type 05 A‑Core accomplished with impressive ease.

These weren’t the only albums that I auditioned during this review by a long chalk: L’Arpeggiata’s Via Crucis; the Alan Parsons Project’s early albums; John Petrucci’s Terminal Velocity; Rhiannon Giddens’ Tomorrow Is My Turn and They’re Calling Me Home; and Larry Campbell and Teresa Williams’ All This Time all formed a major part of the rotation.

Overall, I’d characterise the Type 05 A‑Core as delivering a very detailed, dynamic, open and smooth performance whose sense of relaxed power across the audio spectrum not only makes it very easy to listen to for long periods, but also helps create a solid and spacious stereo sound field. I also felt that the A‑Core’s dynamic performance had an immediacy that I really liked, which could well be due to the speed of its AMT tweeter.

Time To Compare

Comparing the Type 05 A‑Core directly with its Mk2 ancestor really isn’t fair on either. With its array of DSP tuning options, the Mk2 is equipped to deal with a wide variety of nearfield monitoring scenarios. The A‑Core is an all‑analogue monitor designed to deliver the same nearfield performance as a Mk2 in ported mode, set flat.

However, compare we must. Price‑wise, the new Type 05 A‑Core comes in around 30 percent lower than the Mk2, thereby offering excellent value for money. In terms of audio performance, to my ears both performed identically across a wide range of musical genres, from EDM through heavy rock, prog rock, pop, country, to jazz, folk and orchestral music. However, I did feel that I detected a slight difference in the sound once I’d placed a passive A/B switch after my DAC that allowed me to toggle between the two monitor pairs, rather than reaching round the back to plug and unplug signal leads. When A/B’ing instantly in the middle of a track, with both pairs of monitors set flat and delivering the same SPL, the Type 05 A‑Core felt very slightly more open in the mids and upper mids than the Mk2. This was a subtle difference that I did not hear after physically swapping signal leads over. Therefore, to me, it is interesting but, in practice, meaningless.

This is a high‑performance monitor that is not only transparent, revealing and analytical, but is also easy to listen to...

Time To Conclude

The HEDD Type 05 A‑Core is characterised by a combination of control, power and detail, from the bass through to the midrange, alongside clarity and precision in the upper mids and treble. It is not only transparent, revealing and analytical, but is also easy to listen to — partially due to its smooth high‑frequency response, but also because it has an unstressed air of quiet power that never disappears. What I liked the most of all was the sense of immediacy in its dynamic response. This superb overall performance must reflect the pairing of the design and quality of HEDD’s new analogue filter board with the impressive performance of the Type 05 Mk2’s honeycomb woofer, AMT tweeter and ICEpower amplification.This is a very impressive loudspeaker that will not disappoint those searching for a high‑performance, small‑footprint, accurate and articulate analogue nearfield monitor that performs well above its price level.