Mission 770 loudspeaker

Some audio experiences stick in your memory. For me, one such was in 1978, which I reminisced about in a 1987 review for Stereophile of the Mission PCM 7000 CD player, Mission 780 Argonaut loudspeaker, and Cyrus Two integrated amplifier. Mission founder Farad Azima (footnote 1) was a driving force in the UK audio scene in the late 1970s, when I was deputy editor of the English magazine Hi-Fi News & Record Review.

"I used to regularly visit [Farad] at his London apartment and witness stages in the design of a loudspeaker that, in retrospect, would put Mission Electronics on the high-end map," I wrote in that review. "As well as drinking large amounts of his liquor, night after night I would witness Farad putting record after record on his Linn, listening to what seemed to be innumerable prototypes of what became the Mission 770, trying to match the midrange accuracy of the classic 'BBC-sound' Spendor BC1 but marrying it to a less loose bass region, more suited to the special requirements of modern LP replay.

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"And to a large extent he succeeded. I can remember an almost painfully exquisite reproduction of Jackson Browne's live Running on Empty album, Emmylou Harris just taking my breath away with Quarter Moon in a Ten-Cent Town, and Dire Straits' "Sultans of Swing" causing us to boogie until we were disturbed by the early-morning sounds of London's pigeons taking their first cough."

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My formative experience of the original Mission 770 in Farad's listening room was echoed by that of Peter Comeau, who was then reviewing for Hi-Fi Answers. In an apparent twist of fate, Comeau is now Mission's director of acoustic design and has designed a new Mission 770 for the brand's parent company, International Audio Group. (IAG, which is based in both Hong Kong and UK, also owns Wharfedale, Quad, Castle, Audiolab, Leak, and Luxman.) The new 770, which costs $5000/pair including rectangular, open-frame, steel stands, made its debut at the 2022 Munich High End show. Given my decades-long love affair with the original 770, I volunteered to review the new speaker for Stereophile (footnote 2).

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What is old is new again
The 21st century 770 is manufactured in a new facility in Huntingdonshire, England. Superficially, it looks identical to the original: an elegantly proportioned, large, two-way standmount with an enclosure finished in real-wood veneer, except for the front baffle, which is made from white laminate and adorned with a black Mission logo. But, as Peter Comeau explained to me in a Facetime interview, it is otherwise an entirely new design: "We put something brand new in old clothes."

The new enclosure is very different from the original 770, which adhered to the BBC/Spendor "thin-wall" concept. "That was 12mm chipboard with 5mm of bitumen on the inside, [and] there was no bracing at all," Comeau said. "That forced the main cabinet panel resonance down to 175Hz—I know because I've measured the pair I've got—which was okay for vinyl but wouldn't pass muster for the amount of power we're pushing into it these days with bass synthesizers, ... so you've got to do something about that."

You have used a sandwich construction for the walls?

"That's right. This is something I've been working on for some time, and I've used it in other Mission speakers. It's a thicker wall of chipboard on the inside and a thin wall of MDF on the outside, but for the 770, we put an intervening layer of a latex glue [that is] specifically formulated for use in areas where you need to provide acoustic damping. We use judicious methods of bracing the front baffle to the rear baffle to break up the modes as best we could. I am not claiming the cabinet's inert, but what is there is buried pretty low down."

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The original 770 (above) was one of the first speakers to use a polypropylene-cone woofer. While the new speaker's bass/midrange unit still uses a polypropylene cone, the material is different. "Polypropylene went through a period when people didn't like it because it was too soft and floppy—we can now use silica and calcium carbonate fillers and all sorts of things, like mica, to stiffen it up just a little without losing its self-damping property. It's now a much better cone material than it was originally. But, having said that, polypropylene sounds absolutely gorgeous in the midrange. We wanted to keep that."

The woofer's cone is terminated with a nitrile rubber surround, and the motor has a copper cap over the pole piece to reduce distortion and inductance. This is said to extend the driver's bandwidth well beyond the 2.9kHz frequency of the crossover to the 28mm tweeter. The tweeter uses a damped microfiber dome with a damped rear chamber to push the fundamental resonance well below the crossover frequency. "Slightly below the 1kHz region," Comeau confirmed.

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My measurements (see the sidebar) indicate that the reflex port is tuned to a low 30Hz. Comeau told me that this was to avoid the "one-note bass" that is typical of a lot of ported systems. "The inside end of the port is not only profiled exactly the same as the external, but it also meets an internal baffle that mimics the external baffle. In order to get minimum distortion, you've got to balance what the port sees on the inside and on the outside. I think you will find that we've got incredibly low distortion, and you can still get useful output in most rooms down to 30Hz, and more importantly, you don't hear anything nasty coming out of the port."

The original crossover used a single inductor to balance and equalize the woofer's bass-midrange response as well as crossing over to the tweeter, which was driven by a resistor, capacitor, and inductor combination. Farad Azima optimized that 1978 crossover by ear. "It's very simple in terms of its electrical configuration," said Comeau, "but, of course, when married to the acoustic performance of the drive units, the actual rolloff becomes more complex. It was a 'flat-delay, third-order' acoustic crossover. Farad didn't know this, but it just so happened that the things he was searching for worked out to be a good acoustic third-order crossover. I was looking to match those crossover slopes, because I think that's where part of the magic, the musicality of the performance, lies."

Comeau said that he particularly wanted to design a new 770. "I've always had this speaker in my head. It was a revelation at the time; it made music fun, alive. You wanted to tap your feet, bang your knees to the drums, and bop around the room. That's what I wanted to do all over again. "He went through many, many iterations of the new speaker's crossover. "Yeah, this was largely thanks to COVID. Commercial loudspeaker designers usually are only given six months to work on a project at the most. Then COVID hit, and suddenly I had all this time at home that I could spend working on speakers. I must have spent about 2½ years working on [this project] altogether."


Footnote 1: Farad and his brother, nicknamed Henry, who designed the early Cyrus components, had emigrated to the UK from Iran. It took me an embarrassingly long time to realize that their names were related to electronic engineering: Farad is the unit of capacitance, Henry the unit for inductance.

Footnote 2: The Hi-Fi News review was done by the magazine's regular speaker reviewer at that time, Trevor Attewell. See hifinews.com/content/mission-770-loudspeaker-original-770.

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COMMENTS
remlab's picture

I hate asking questions like this, but why do PM's FR measurements always look so much worse than your own? The upcoming Paradigm Founder measurements will probably be no different

Kal Rubinson's picture

There may be other differences but the difference in scale is significant.
Amplitude (vertical scale) spans 30dB in HFN and 50dB in Stereophile. Frequency (horizontal scale) spans 20Hz-60kHz in HFN and 10Hz-30kHz in Stereophile.

As a result, the HFN display would visually emphasize the level deviations even if the data were the same. Also, HFN seems to apply more smoothing.

remlab's picture

but it's the "Other differences" I'm referring to. Big deviations that aren't very difficult to glean from the measurements, even taking into account the differences in scale

John Atkinson's picture
remlab wrote:
but it's the "Other differences" I'm referring to. Big deviations that aren't very difficult to glean from the measurements, even taking into account the differences in scale

As well as the different graph scaling mentioned by Kal Rubinson, while there's no smoothing in my speaker response graphs, while Paul Miller at HFN takes his response measurement at a single point in space, I average mine across a 30 degree horizontal angle on the chosen axis.

I wrote about why I do this in the paper on loudspeaker measurements that I presented to the AES in 1997 - www.stereophile.com/content/measuring-loudspeakers-part-three-page-2:

"There is a problem with taking the response at just one point in that there is almost too much information. Some of the fine detail will be specific to just that one point in space. With a loudspeaker whose drive-units are mounted in some kind of vertical array, it seemed sensible to implement some kind of spatial averaging. This would smooth out any position-dependent wrinkles in the measured response, while leaving the significant information intact. Accordingly, my published responses are the average of seven measured responses, taken at 5 degree intervals across a 30 degrees horizontal window on the reference axis."

John Atkinson
Technical Editor Stereophile

Glotz's picture

I'm still a little fuzzy on the 'too' much information bit that a single point axis responses yield, in the first line of that paragraph from your paper in 1997. I've read that line several times over the years and perhaps I still have confusion here.

The multiple-point measurements minus position-dependent wrinkles seem easy to understand, but it's really the remainder of products (50-degree window) in comparison with the on-axis measurement that gives us a greater definition of the frequency response?

The concept of a wider window in space seems easy enough, but I'm not sure that's it. Does it rather define the direct-on-axis response?

Anton's picture

When I saw the post, I thought it was one of JA1's post of vintage reviews.

Then I got to that review in my new Sterophile and realized.

It's almost a dead ringer!

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