Mission Freedom Loudspeaker

The Mission 770 Freedom was an award winning British loudspeaker produced by Mission Electronics, an audio company based in Huntingdon, United Kingdom. The Freedom model variants date from the late 70s through to the late 80s. There are five versions of this large stand or pedestal mounted loudspeaker, all of which are two-way designs combining a woofer and tweeter in a reflex tuned cabinet.

The Mission Freedom had an innovative design, natural sound quality and extremely high power handling . Mission was the first company to negotiate the patent rights for the commercial exploitation of polypropylene as a loudspeaker cone material and this was the chief innovation .

Mission Freedom 770I & II (circa 1978)

The 770 I and II variants were the original Mission Freedom's designed by Farad Azima. Only comparatively minor revisions separate the two versions, incliding a revised ferro-fluid ferro fluid cooled tweeter in the Mark II variant. The Freedom's key technical innovation was its 200mm polypropylene polyprylene mid/bass driver [[woofer]. The loudspeaker as a whole was 'Recommended' by HiFi Choice magazine who described it as "a lively stand-mounted system [that] demonstrated a wide dynamic range with outstanding power handling capacity.

Mission Freedom 770III (circa 1980)

The updated 'Mark III' Freedom featured an updated polypropylene mid/bass driver but which a larger 33mm voice coil voice coil. Thermal performance and power handling increased. In a HiFi Choice Magazine review the tester noted that "the bass guitar handling was extraordinary, sustaining 500W peak or 200W average with only moderate aural distortion" (many contemporaneous models could only withstand 20W).

As before, reviews noted the excellent low-distortion performance, easy amplifier load and high sensitivity. The natural character of the sound was due in large part to the even frequency response, which remained within narrow tolerances (±2 decibels from 65 hertz to 16 hertz).

HiFi Choice described the sound quality of the Mark III model as follows:

The sound was considered open and explicit but with a degree of 'hardness' and 'sharpness' in the lower treble. On the stereo sessions the imaging was only a little short of the top category, exhibiting good depth and excellent lateral image precision. On rock programme the 770 gave sharp definition to percussion and transients [...] Overall the ratings were impressive and generally justified the price

(which was £370 in 1980 including stands).

Mission Freedom 770 IV (circa 1985)

The Mark IV version of the Mission Freedom utilised a new 200mm homopolymer homopolymer mid/bass driver. This material belongs to the polypropylene family but is mineral loaded so that in appearance it is black in colour rather than transparent. The cabinet was also radically re-designed. The Mark IV Freedom uses a transverse folded construction (the top, bottom and sides had 45-degree mitred faces, with the back and the baffle being separate). Despite a substantial internal volume the loudspeaker was still stand mounted. Purpose-designed stands made of vinyl covered particle board fitted into slots in the speaker's base.

The period of this loudspeaker's manufacture coincided with a trend throughout the product range for unusually substantial front baffles. In the case of the Mark IV Freedom this took the form of thick MDF, which was a comparatively novel material for loudspeaker enclosures at the time. The Mark IV also used Mission's new cellular reflex port, a tunnel port divided up into a matrix of smaller holed in order to reduce port turbulance.

Mission Freedom 770 V (circa 1987)

Introducing the last iteration of the Freedom loudspeaker Mission stated, "Following the extraordinary success of the original Mission 770, inferior copies flooded the market to such a degree that at Mission we decided to move on". The Mark IV 770 was fitted with the Mark III bass/mid driver to become the Mission 737 renaissance. The 770 Freedom became an entirely new loudspeaker designed to meet four specific goals:

Firstly, we [i.e. Mission] wanted to ensure that the frequency range offered greater extension. Secondly, our design team felt that the bass response could be tighter, more articulate, with more transient attack. Thirdly, we wanted to increase the dynamic headroom so that all non-linearities, compression, and saturation problems were eliminated. Finally, we wanted to enhance sensitivity and efficiency for the era of digital masters

Cabinet

The brand new cabinet was based around the transverse folded technique The cabinet was increased further in size but was still designed as a stand mount speaker (albeit a very large one). Purpose designed stands made of vinyl covered particle board fitted into slots in the speaker's base.

An unusual baffle design was used which mirrored other innovative approaches used elsewhere in the range, e.g. the Mission 700 Leading Edge and the Mission 707). The baffle was unusually thick and constructed of MDF. It is constructed out of two MDF panels sandwiched together with the outward facing panel wasted away to create a time aligned/corrected baffle with a proud mounting for the woofer. A strengthening brace was included internally between the bottom of the timealigned section of the baffle and the reflex port below. The cabinet was part filled with acoustic wadding and the interior faces had a vico-elastic damping material applied.

Drivers

An unusual feature of the new 770 Freedom was the tweeter which, like the time aligned baffle, eschewed normal practice in domestic loudspeaker design in favour of a feature more common in the professional audio sector: Horn loading horn speaker. This affects dispersion (and thus stereo imaging) and sensitivity (with the potential to reduce distortion). The Freedom's elliptical horn was designed with home use in mind, the ellipse profile providing the desired dispersion characteristics in a typical domestive setting.

This brand new double-chamber, impedance transformed super-elliptical tweeter is designed to offer extraordinary smoothness and realism - eliminating the remnants of typical dome tweeter sibilance and offering uncanny dispersion characteristics. The mathematics of impedance transformation uniquely ensures structural form integrity to the polymer dome under severe transient conditions. The unit is then oil cooled to avoid temperature related performance aberrations and increase saturation thresholds.

The horn was paired with a more normal 'direct radiator' dome tweeter, rather than a compression driver. The horn itself was injection moulded polypropylene reinforced with natural mineral fibres (this being the same material used to make the injection moulded frame for the grill covers as well as the baffles of the 707 and 700 Leading Edge models). The face of the horn also featured moulded 'whiskers' to reduce diffraction effects. The added sensitivity and efficiency offered by horn loading enabled the mid/bass driver to cross over to this innovative drive unit at an unusually low 1.9 kilohertz. This avoids the more typical range of 3 to 3.5 kilohertz at which the ear is most sensitive to the phase anomalies that normally result.

The mid/bass driver used a homopolymer mineral-loaded plastics material and was a derivative of the Mark IV Freedom variant. It featured a large voice coil to aid power handling, distortion, thermal efficiency etc., and a narrow natural rubber surround unlike the wide inverted surround of the Mark I, II & III driver. The surround represents a radiating surface and the source of considerable distortion at low frequencies, thus minimising its width minimises the area of this unwanted radiation, thus helping to reduce distortion further. The front face of the unit was finished with an inverted dust cap (of the same homopolymer material) with the mission logo printed in white text. The drive unit has a cast magnesium basket structure and is built to very high quality standards. The drive units are marked on the back with 'Argonaut' and two of these units appear in the flagship 'Argonaut' speaker which is based on the Freedom design.

Mission themselves described the unit thus: "The cone material is carefully optimised for mass, rigidity, compliance, and 'Q' to offer hitherto unattained low frequency extension for a system of this size. The brass-plated pole piece with special geometry, together with high temperature voice coil materials and ventilation, increase motor output and power handling".

Sound Quality

Mission described the performance of their latest model as follows: "When measured, the Freedoms are capable of extraordinary behaviour. The on-axis response is smooth, off-axis measurements exhibit minimal aberrations, and driven at 90 dB the midband distortion is close to 0.1% - approaching amplifier specifications!"

These speakers were described as 'state of the art reference monitors' and they are what reviewers term 'transparent', enabling the quality of recorded material to show through. Overall, these speakers have a very clean and smooth sound and accurate stereo imaging due to the horn loaded tweeter. There is also an emphasis on speed, attack, dynamics and a wide frequency range. Indeed, the bass is unusually extended for a system of this size, with meaningful in-room response measurable to as low as 28 hertz. .

Mission's tagline for the design was, "Of the 770 we have always said, '...and when you switch over to the 770's you will smile and say - that's Magic!'".

Later Models

The last generation of Mission Freedoms occupied a place high up in a product range that included the Mission 70, the Cyrus 1 amplifier, the DAD7000 CD player, the 774LC tonearm, a line up that is today widely regarded as 'classic' . With the dawn of the 1990s the Freedom's became the 764's and reflected a move away from large stand mount loudspeakers to floorstanding designs. The Freedom name was resurrected in more recent models but bears little relation to this 'classic' version.

Buying

Given their popularity at the time they were offered for sale, good examples of all models of the 770 Freedom can still be found. The Mark I and II are a large speaker system for the amount of bass output available. They are also wider than they are deep, and thus unfashionably seventies in their appearance. For the enthusiast, though, they will always offer a characteristically natural, airy sound.

The last generation Freedoms are well suited to current day applications, although they represent a very large speaker system by modern standards. Stand mounting is highly recommended because the horn loaded tweeter is very directional in the vertical plane and they sound rather dull if not at ear-level. Stylistically, the choice of grey woodgrain finish and a pair of narrow black stripes, combined with bold red 'Freedom' graphics on the front, ensures that these speakers make a visual statement.

Their sonic performance is very good even by today's standards. The last generation Freedom's were over-engineered for many of the sources and amplification then extant in the 1980s. This means that high power amplifiers and high bit-rate digital sources can now fully exploit their capabilities with excellent results.

There are some issues that the potential second hand buyer needs to be aware of. Some of the crossover components are prone to over-heating, to the extent that they begin to melt the plastic of the terminal plate to which they are affixed (this is visible by looking for melting next to the negative terminal). Likewise, the polymer dome tweeter degrades markedly with age with the diaphragm shrinking over the pole piece and becoming dented and distorted. These are difficult to replace as the mineral loaded plastic horn is glued to the face plate of the tweeter. In addition, the tweeter's motor assembly is encased in a sealed 'impedance transformed' case (as is correct with horn loading) that is also glued in place. Replacement of the drive unit for a modern equivalent is difficult. The mid/bass driver, however, is extremely durable and none of the materials used in its manufacture are prone to marked deterioration with age.

See also

• Mission 737 Renaissance