Falcon Acoustics

IMF 200 Complete@Home

Loudspeaker Kit

£2,795

I’ve been a fan of transmission line loudspeakers since the mid-nineteen seventies when I heard my friend’s newly acquired pair of IMF TLS80s. Not only was this my first experience of transmission lines. It was also my first experience of the now legendary KEF B139 bass driver. I was completely bowled over by the well-controlled and extended bass coming from a domestic design.

Alas, my budget at the time didn’t stretch to the mighty IMFs, but I bought a pair of LNB Paralab 8 TLs and was very pleased with them. However, although the bass was taut, it didn’t have the low extension of the TLS80s and I wanted something that used the B139. This inspired me to build a pair of Chris Rogers’ PRO9-TL quarter-wave tapered transmission lines, using the design published by Rogers in Practical Hi-Fi and Audio in 1976.

These 3-way speakers, which use an Audax HD12 tweeter, a Peerless K040-MRF midrange, and the KEF B139 bass driver, have been with me longer than my wife of thirty-seven years. However, unlike my wife, they have undergone a number of major upgrades over the years. I thought that the days of seeing speakers that used the B139 had sadly passed, so I was very excited to hear that a brand new quarter-wave transmission line loudspeaker kit was being launched that uses this woofer in its design!

Falcon Acoustics was founded in 1972 by Malcolm Jones, who was a Senior Development Engineer at KEF. Jones designed the B139 woofer, as well as many other loudspeaker drivers and systems, including the iconic B110 midrange and T27 tweeter units. In 1974, he left KEF to work full time at Falcon Acoustics, where he remained until his retirement in 2009. At this time, Jones transferred Falcon to Jerry Bloomfield, who himself has decades of knowledge in loudspeaker designs, including the IMF range of speakers.

IMF Electronics was formed in the US in 1961 by Irving M Fried who, following the suggestion of his friend Saul Marantz (the founder of the audio brand Marantz in 1948), called the new company ‘IMF’, using his initials. Seven years later, a British branch of IMF was opened, and this combined Anglo-American company produced the TLS80. This was a 4-way, quarter-wave tapered transmission line loudspeaker that originally employed a KEF B139 bass unit, a KEF B110A midrange, with a Celestion HF1300 and HF 2000 as the tweeter and supertweeter. It was a ‘to die for’ super speaker of the late nineteen seventies, a real exotic.

Rolling forward to 2021, Falcon is now making brand new B139s, as well as B110s and T27s, all adhering to Malcolm Jones’ original specifications. The KEF B139 bass driver differs from traditional drivers in that instead of a conventional paper cone, it has an expanded polystyrene piston laminated with a thin aluminium sheet. This piston is connected to the voice coil and a rolled neoprene surround in the usual manner. As the piston is a solid object, it doesn’t suffer from break-up as paper cones tend to when operating at low frequencies and being driven hard. Consequently, it can move large volumes of air when required to do so.

DOING IT YOURSELF

I previously reviewed the IMF100 eighth-wave bookshelf speaker from Falcon for StereoNET and was very impressed with the build and sound quality. I was therefore expecting great things from the new IMF200 quarter-wave transmission line loudspeaker kit, which has recently been released and is competitively priced at £2,795 for the light oak or walnut veneer versions. Add £400 for rosewood veneer finish, and another £400 if you want to buy the speaker built-up.

The speaker is a 3-way design, featuring a Falcon T27 ¾ inch Mylar dome tweeter, B110 5 inch Bextrene cone midrange, and a B139 bass driver. As with the IMF100, the IMF200 employs a detachable Tygan cloth speaker grille that is held in place magnetically. The cabinets themselves have smooth curved front edges, giving the speakers a modern appearance that looks great with or without the grille in place.

The cabs are supplied pre-built, made of Italian high-quality Baltic birch plywood which results in a void-free core with excellent acoustic properties. They can be finished in either walnut, rosewood, or light oak real wood veneer finishes and will complement most styles of decor. To ensure that the correct range of frequencies gets routed to the appropriate driver, there’s a factory-assembled crossover that uses Falcon UK-made polypropylene capacitors in the midrange and high-frequency sections.

As with the IMF100s, the pre-assembled cabinets, wood veneer, and crossovers are all of superb quality. Even the grain of the wood flows seamlessly up the sides and across the top of the speakers. Push-on spade connectors are used for the internal connections so that no soldering is required. All necessary hardware and drive unit gaskets are included, including a pair of Allen keys for tightening the bolts that secure the drive units and rear terminal panel. Some smart silver and black ‘Falcon’ logos with a self-adhesive backing are also provided to adorn the speaker grilles. An online instruction manual and video are available to guide you through the construction process. The instructions are very easy to follow with a photograph and accompanying description showing each stage of the build.

The first job is to connect the T27 tweeters and B110 midrange drive units to the internal cabling using the spade connectors. Now, the drive units can be fitted onto their respective gaskets, inserted into the accurate cut-outs in the front baffle, and secured with the supplied bolts. Next, the crossovers are fitted onto the pre-installed nylon pillars situated behind the B139 bass driver. The input cables on the crossover are then pulled through the back of the cabinet using the provided draw-wire and connected to the terminal panel at the rear. Finally, the B139 is fitted into position on the front.

Once the final position of the speakers has been decided, the spikes can be screwed into the threaded inserts that have been fitted on the underside of each speaker. These provide a firm coupling to the floor and will improve the bass response. They cause no damage to carpets as they nudge their way discretely between the strands of the pile. For hard floors, a set of spike shoes will be required for protection. All in all, it took me less than a couple of hours to build both loudspeakers, and the result was very professional looking.

Each finished speaker is a sizeable 270x1189x408mm (WxHxD) and weighs in at 34kg. Quoted frequency response is 23Hz to 20kHz +/- 3dB, with a sensitivity of 86dB/2.83V/m – not bad for a TL design, and much better than IMFs of yore. The IMF200 can handle amplifiers of up to 200W, and has a nominal impedance of 8 ohms. My 300B PSE (parallel single-ended) valve monoblock power amplifiers were used for the audition process and delivered highly satisfactory results. Before I commenced listening, the speakers were run in at normal listening levels for a day – as recommended by Falcon.

THE LISTENING

This is a great loudspeaker, and superb for the money. Its bass is really tight, punchy and well-controlled, and goes down seriously deep. Its midband is clear with excellent stereo imaging, and to top it off is an impressively refined treble. For example, the famous 1979 Telarc recording of Tchaikovsky’s 1812 Overture, performed by The Cincinnati Symphony Orchestra showed me how low the bass can go. This recording makes use of live cannons in the courtyard of the Baldwin-Wallace College in Ohio and, according to the album liner notes, “managed to remove the glass in the lower windows of the college’s Department of English building some several hundred feet away”! The resulting LP is a challenge not only for cartridges to track but for speakers to reproduce. The IMF200 met this head-on, making me feel a couple of the cannon cracks in my stomach.

With a Chasing The Dragon direct-cut vinyl recording of Rimsky Korsakov’s Capriccio Espagnol performed by the National Symphony Orchestra under the baton of Debbie Wiseman, large kettle drums are played near the beginning of the piece. These are every bit as powerful as I remember them at the actual recording session that I attended at AIR Studios in London back in 2017. The reproduction of the drums, which were situated at the back of the orchestra behind a screen in order to get the acoustic balance correct, was punchy and tight – a testament to the B139 and transmission line design. The result was a real sense of ‘being there’ in front of the orchestra. The imaging of solo players was sharp and clearly distinct from that of adjacent musicians. The powerful finale had great impact, the performance being absolutely spectacular.

The IMF200 proved equally at home with solo instrument recordings, which are reproduced with excellent detail and clarity. This is exemplified by a recording of Bach’s Cello Suite No. 3 in C Major from Chasing The Dragon’s boxed album of the complete set of the J S Bach Cello Suites. It is played by renowned cellist Justin Pearson and features Schumann’s piano accompaniment played by Katherine Rockhill. Things really grabbed my attention from the outset; the presence of the cello and piano in my listening room was incredible, and all the detail of the instruments, together with the acoustics of the church where the recording was made, was brilliantly conveyed.

Both the imaging and the timing of this speaker are excellent, as demonstrated by a great piece of jazz from Pierre Gossez on his second Come Bach LP. The final movement from Sonata is a Jacques Loussier composition played on the saxophone with piano, harpsichord, and drums accompaniment. Each instrument had its own clearly defined position in my listening room, and the tinkling of the harpsichord was handled superbly. The music was propelled along with gusto. There was a real sense of openness and clarity, and the whole piece had incredible energy. Tonal balance was really good, meaning that I wasn’t distracted from enjoying the music.

With an LP of Scarlatti Sonatas played on the harpsichord by George Malcolm, the IMF200’s sophisticated handling of the instrument resulted in superb clarity and detail. With the Sonata in G major, I was drawn into the performance by the intimate musical complexities of the piece and was impressed by the tonal variations produced by the instruments. The top end in particular was pin-sharp, but without being at all edgy.

I understand that female vocals are used as part of the voicing of the Falcon loudspeakers, so I turned to another Chasing The Dragon direct-cut vinyl recording – A Tribute to Ella Fitzgerald sung by Clare Teal with the Syd Lawrence Orchestra. Cole Porter’s Too Darn Hot started off with some opening blasts from the saxophones, which progressed into the main vocal section. Pace and timing proved spot-on, and the excitement of Teal’s vocals was brilliantly conveyed. The whole performance really sparkled with energy.

Another important aspect of any top-quality loudspeaker is its ability to convey the atmosphere of the recording venue. To demonstrate this, I spun an audiophile LP recorded at 45RPM from Yarlung Records called Young Beethoven featuring the Janaki String Trio. The excellent playing of Beethoven’s String Trio in C Minor Op. 9 No. 3 on the violin, viola, and cello was reproduced with consummate clarity. The warm atmosphere of the Zipper Hall in Los Angeles, where the recording was made, was beautifully conveyed. The slightly menacing opening chords of the allegro swiftly flowed into an exuberant and yet intimate section. The surprisingly complex structure of the music is clear and detailed, and posed no problems for this loudspeaker.

THE VERDICT

The IMF200 is more modern in appearance than traditional transmission line speakers of old, and will certainly be at home in many modern decors. The internal design of the folded and tapered quarter-wave line has been cleverly incorporated into a slim profile cabinet. The detachable and magnetically-secured grille cloths permit the speakers to be used either with or without the grilles, depending on whether you are wanting a traditional or more contemporary look.

The kit is a doddle to construct for anyone who can turn an Allen key, and the finished result appears very professional indeed. The quality of the components and the finish of the wooden cabinets is extremely high, especially considering the price. The sound quality has all the authority and bass extension that you would expect from a quarter-wave transmission line loudspeaker. The IMF200 takes simple solo instruments and complex full orchestras in its stride and handles them with great panache.

I must confess that I never expected to hear a modern loudspeaker at this price point that would eclipse the qualities of my trusty PRO9, but the IMF200 has done just that.

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