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Hafler TRM

Active Monitors & Subwoofers By Hugh Robjohns
Published August 1999

Hafler TRM

The Hafler brand name has been around since the '70s but isn't yet well known in the UK project studio market. All that could be about to change, courtesy of the TRM range of nearfield active monitors and subwoofers. Hugh Robjohns mixes and matches.

I first came across Hafler hi‑fi amps over 20 years ago, and as I recall they were of unusually high specification at surprisingly low prices. It seems that this company policy remains in force today: their range of nearfield loudspeakers includes a two different 2‑way active monitors and a pair of subwoofers, all of which offer impressive levels of performance at a very affordable price point.

For this review I was presented with almost the complete set: a pair of TRM8 active nearfield monitors, a pair of the slightly smaller TRM6 active nearfields, and a TRM10S self‑powered subwoofer. Apparently these loudspeakers have taken over three years to perfect, but the end results suggest that the wait was worthwhile.

The TRM8

The TRM10S subwoofer.The TRM10S subwoofer.

Introduced in 1997, the TRM8 is a fairly conventional 2‑way active speaker much like the vast majority of its competitors. There is nothing really revolutionary or particularly innovative in its design — it simply uses quality components in a well‑conceived package. The cabinet has an internal volume of 13 litres and is ported through a slot vent to the rear, which means that a placement of at least five inches away from a rear wall is essential. The box dimensions are a reasonable 392mm high, 260mm wide and 330mm deep, and each speaker weighs almost 16kg. A separate cavity at the rear of the enclosure houses the compact electronics module, and the front of the cabinet is stepped so that the vertical axis of the voice coil in the woofer lines up below that of the tweeter, to assist in accurate time alignment. The cabinet is lined with a thick felt material and stuffed with acoustic wadding to damp resonances.

Although the delicate tweeter is protected behind a wire mesh, the two drive units are exposed at the front of the speaker for that 'professional' look. The magnetically compensated mid/bass unit is a 10‑inch polypropylene design with a soft santoprene rubber surround, while the tweeter is a 1‑inch (25 mm) soft dome. What appears to be a blob of goo on the inside of the tweeter grille is actually a part of a waveguide system which, in conjunction with the flared area surrounding the tweeter, aids smooth‑high frequency dispersion and improves the imaging of the speaker.

Mounted into the left‑hand side of the tweeter faceplate are a pair of bi‑colour LEDs (one for each amplifier channel) which illuminate green when the monitor is powered, flash red at the onset of clipping, and remain a steady red during thermal overload. The mains power switch is mounted on the right‑hand side of the faceplate — a far more convenient location than somewhere around the back!

The rear panel is dominated by the metal chassis of the amplifier pack, complete with large vertical heatsink fins on either side. Balanced signal inputs are accommodated by a Neutrik combi‑jack connector accepting either XLR or TRS leads, while an adjacent phono connector provides for unbalanced connections. Balanced or unbalanced inputs are selected by a DIP switch accessed through a cut‑out in the rear panel.

The input sensitivity of the amplifier can be varied over a wide range, between 275mV and 3V, depending on the selected input. DIP switches provide for nominal operating levels of +4, +1, ‑2, ‑5, ‑8 and ‑11dBu (these figures being the input level required to generate sound‑pressure levels of 100dB at 1 metre). The monitor can thus be matched to pretty much anything operating at between professional +4dBu and semi‑professional ‑10dBV levels (‑8dBu), or even to low‑level domestic hi‑fi outputs. Two further DIP switches offer the unusual but useful facility to mute either or both of the amplifier channels, for testing woofer or tweeter drivers and their amplifier chains.

The crossover section provides 24dB/octave (fourth order) filter slopes to integrate the bass/mid and tweeter drivers. The crossover frequency is set to 2.5kHz, and a 43‑microsecond delay is inserted into the tweeter path to improve the accuracy of the time alignment between the two drivers. A further 12dB/octave high‑pass filter removes the amplifier‑draining subsonic frequencies below 30Hz, and a collection of DIP switches allows the bass and treble responses to be tailored for a specific installation. Bass shelving contours affect the output below 200Hz in 2dB steps from +4 to ‑4dB, and identical facilities exist for the treble output above 3kHz.

The amplifier pack is based on Hafler's TransNova technology, a proprietary design which the company believes provides certain benefits — namely, a simple signal path, improved distortion, and better linearity than conventional amplifiers of equivalent general specifications. In the TRM8 the technology has been arranged to provide 150W of power into the 4Ω bass/mid driver and 75W into the 6Ω tweeter — a combination which allows a pair of monitors to produce up to 123dBA of sound at 1 metre! Distortion of the complete amplifier/speaker package is given as better than 0.5 percent (with no output level specified) between 100Hz and 21kHz, and the overall frequency response is flat within 2dB from 45Hz to 21kHz. Both are commendable results for such a small unit.

The TRM6

The TRM8.The TRM8.

This diminutive sibling retains most of the technical characteristics of the larger monitor but in a smaller format. Weighing 11kg and measuring 336mm high, 225mm wide and 292mm deep, the TRM6 is roughly 50mm smaller in all dimensions than the TRM8. The rear panel features the same balanced and unbalanced inputs, drive sensitivity and frequency‑response tailoring, all configurable through DIP switches. Unlike the bigger monitor, however, it has no vertical heatsink fins, as the amplifier chassis alone is sufficient to dissipate the unwanted heat of the considerably less powerful amplifier packs.

Using the same tweeter as the TRM8, but coupled with a 6‑inch bass/mid driver, the TRM6 manages a response which extends down to 55Hz within 2dB from an upper limit of 21kHz. Distortion figures remain the same as for the bigger monitor, as do most of the other amplifier and crossover specifications. However, the crossover point has been raised to 3.2kHz and the equalisation curves modified accordingly.

Amplifier power is also much reduced compared to the TRM8, with just 55W available for the bass/mid and 33W for the tweeter. Despite this, the maximum acoustic output of the TRM6 remains impressive at 118dB SPL per pair at 1 metre. The amplifier module employs a variation of the TransNova design called TransAna, which is just a lower‑powered version of the original patented topology.

Listening Test

I started my listening with the TRM8 monitors on their own, and my initial impression was of a tendency towards brightness. This is not an uncommon trait in modern two‑way designs, as one of the deficiencies of polypropylene bass/mid drivers is a tendency to sound dull in the upper‑mid range. An easy fix is to increase the drive to the tweeter, in an attempt to gain more 'air', which may sound superficially better but rarely survives extended listening.

Trimming the high‑end response by ‑2dB was just a tad too much, but as I became used to the Haflers I found the brightness less of a problem for short periods. Extended listening is fatiguing for me, but then I grew up on a diet of dull old BBC monitors. On the plus side, they are able to extract an awful lot of information from even the most complex tracks — far more, indeed, than they should have been able to do given their price. Stereo imaging is very precise and stable, with big, broad images and better‑than‑average depth. The frequency response is pretty smooth, with perhaps a touch of recession in the lower mid and a mild peak around 10kHz, but overall it's very commendable. As with all ported designs, the bottom end has that characteristic hump just before it plummets away, which tends to bolster up kick drums nicely. It's not entirely accurate, but it is impressive and effective for all styles of pop music.

The TRM8s aren't quite as confident with orchestral and choral works at the bottom end, as the artificiality of the bass region is made a little more obvious, but mid‑range reproduction is very good and they certainly allow the listener to 'see' into a complicated balance very well.

Turning to the smaller TRM6s, I found them extraordinary! Giving away very little to the larger speakers in the high and mid range, the lack of bass extension is their only significant weakness. Stereo imaging and mid‑range detail are to high standards, and they are certainly capable of extracting a lot of detail from the mix. Again, sharing the slight TRM8 tendency towards hardness at the top end, and with a bolstered ported‑bass response, these monitors really do suit pop and rock music very well.

Plumbing the subwoofer (see the 'Sub Stance' box below) into the system was entertaining, and it was several days before I felt that I had matched the components fully, but in my experience few subwoofers integrate in a totally seamless way. However, the Hafler system (like Genelec subwoofers) provides plenty of flexibility for fine‑tuning the conjunction between the satellites and sub, and the end result of all my tweaking was a very useable setup, with the desired extension to the bottom end — both in terms of frequency response and power handling. The sub works particularly well with the TRM6s, which really do benefit from the extra octave and a half at the lower end, although having the crossover point so high doesn't help in making the sub 'disappear', and I found that the bass cabinet had to be positioned on the central axis of the room to maintain accurate stereo imaging.


I'm very impressed with this range. Indeed, I found myself comparing the TRM8s with long‑term favourite actives such as the Genelec 1030A, the HHB Circle 5A, and even the Mackie HR824. The Haflers came off well in the comparison anyway, but when you consider that the TRM8s are around £400 cheaper than the Mackies and almost half the price of the Genelecs, this comparison becomes very persuasive indeed! They may not be materially better than these recognised leaders — that's always a very subjective judgement — but they're certainly worthy of consideration on a value‑for‑money basis. As for the smaller TRM6s, considering the greatly reduced power capability I'm amazed at how well these tiny boxes work, though, as mentioned above, they're even better with the subwoofer.

Overall, these Hafler speakers provide an impressive level of performance at the price, and will no doubt cause some consternation amongst other manufacturers of active two‑way monitors.

Manual Without Labour

The manual for the TRM8 loudspeaker is one of the most comprehensive I've seen, and I wish other manufacturers would follow Hafler's lead. Not only does it explain how to get the best results from the speaker with room placement and switch settings, but it also contains complete circuit diagrams, disassembly instructions, parts lists, calibration procedures, and circuit descriptions. This might seem a little over the top, but having such all‑inclusive information would make all the difference to the poor unsuspecting maintenance engineer who has to fix a defective amplifier in five years' time, long after the 12‑month warranty has expired!

Sub Stance: The TRM10S Subwoofer

There are two self‑powered subwoofers, the TRM10S and 12S, in this Hafler range, and if you haven't already guessed, the number refers to the size of the bass driver — 10 inches in the TRM10S and 12... well, you get the idea. I had the smaller 10S, measuring 375 x 407 x 407mm and weighing 24kg, to play with during the review period. The TRM12S is, naturally, a bigger beast and weighs a considerable 42kg! Like the satellite monitors, the cabinets feature a slotted port and the speakers can be arranged to fire either downwards through the base of the cabinet (which is supported above the floor on four stubby legs), or directly forwards into the room. The drivers are described as having a "cellulose fibre cone" which I think we can take to mean a conventional paper cone!

The technology involved in both subwoofer systems is similar to that employed in the nearfield monitors, with another variation of the TransAna amplifier design delivering a healthy 200W to the speaker in both versions. The larger TRM12S unit has a frequency response extending down to 25Hz within 2dB from 110Hz, and a maximum acoustic output of 121dB SPL at 2 metres. The smaller 10S still manages a very respectable lower frequency limit of 27Hz and 112dB SPL.

The rear panel of the subwoofer carries all the operational controls and connections. An IEC mains inlet is found on the right‑hand side of the chassis, but there is no mains on‑off switch, as a built‑in automatic turn‑on and sleep system detects an incoming audio signal and powers the unit accordingly. A green LED illuminates when it's active. Balanced inputs are catered for with a pair of XLR connectors, while two phono sockets accept unbalanced signals. Selection of the appropriate input format is via a DIP switch, just as with the satellite monitors. Two inputs are provided to allow summation of the bass contribution from stereo channels if required, but there is no provision for daisy‑chaining the main stereo signals through the subwoofer and on to the satellites — discrete feeds must be provided.

Input gain is adjustable over an enormous range from 80mV to 5V (depending on the connector used), and there's a slotted rotary level‑control positioned between the XLR and phono connectors and calibrated in 3dB steps from 0 to ‑30dB. A second rotary control determines the low‑pass corner frequency and is calibrated between 140 and 40Hz in 10Hz increments. An adjustable fourth‑order 24dB/octave Linkwitz‑Riley filter performs this task, in combination with a separate high‑pass filter which removes subsonic signals below 18Hz at 12dB/octave.

Three of the four DIP switches on the panel (the fourth being the balanced/unbalanced input selector) determine the relative phase of the subwoofer output. Options are for 0, 90, 180, or 270 degrees of phase shift at 80Hz. Correct setting of this parameter is essential in making the subwoofer work with, rather than against, the satellite speakers.

The combination of adjustable sensitivity, turnover frequency and relative phase enable the subwoofer to be matched very effectively in almost any situation, although optimising the setup can take considerable time and effort.


  • Detailed mid‑range.
  • Good room‑matching facilities.
  • Interfacing flexibility.
  • Adaptable subwoofer alignment.
  • Value for money.


  • Suits rock music much more than classical.
  • Tendency towards hardness and fatigue.


A family of active 2‑way professional monitors and subwoofers which achieves an impressive balance between quality and affordability.