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Product: Bose 901 loudspeakers (1st series)
Manufacturer: Bose - USA
Approx. price: from €500 to €1500 depending on status/conditions
Reviewer: Lucio Cadeddu - TNT-Audio Italy
Published: September, 2024

In Part I of this series of articles, devoted to the legendary Bose 901 loudspeaker, you will find the history of the design and its designers, the cornerstones of the Direct/Reflecting® idea, a summary of how to distinguish the different 901 series over the years and a list of urban myths, often incorrect, that crowd the web and audio fans' - often fallacious - memories. In Part II the focus is set exclusively on advice related to room placement and active equalizer settings, leaving the listening notes to this Part III.

“No highs, no lows, must be a Bose” Man, are you serious???

Before we start. In my listening room I positioned, after several attempts, the tip of the V at 50 cm from the rear wall. Obviously, each environment is different. Let's say that - as it is common practice - you can use the distance from the rear wall as a sort of tone control for the bass/mid-bass range: the closer to the wall, the higher the level of bass frequencies. However, Bose prohibits going below 15 cm. As regards the frequency response adjustments, I kept the controls in flat (the black reference dot on the front of the equalizer) and the bass in the "normal" position. With some bass excessive records, those with a boost in the first two octaves, I found the attenuation of the bass frequencies below 40 Hz to be beneficial. Obviously, every system, every ear and every environment is a different situation, so feel free to experiment.

From the second series onwards, Bose recommends using amplifiers with a damping factor of at least 40. Evidently, they realized that keeping the 9 midwoofers per cabinet under control was not an easy task for the amplifiers of the time, most of which were still tube based and with low damping factor. A good, modern, solid-state amp will put your reins on any driver excess.

I'll start the listening notes by debunking some urban legends. The Bose (901) have neither bass nor highs. This legend was generated, realistically, by those who listened to them without the Bose equalizer, a crucial component of the 901 design. Furthermore, they probably listened to them positioned like a traditional speaker, i.e. with the drivers radiating towards the listening point. In the Bose 901, the 8 drivers must face the rear wall, and only one, the front one, must radiate towards the listening point. If you have listened to them in one of these two wrong configurations, you have not really heard the 901, but something completely different, and you'd better keep your mouth shut ;-)

Why? Well, because these strange speakers really generate a lot of bass and treble, and it's hard to believe that there are no real woofers or even a single tweeter, but only 12cm full-range drivers, without any crossover network. The bass range is not only well extended, but it's also very powerful, so much that, when the musical program and listening level allow it, the punch of the bass on your ribcage and solar plexus is extremely powerful. The bass range, though powerful, is not as fast as in good modern speakers, but it is still capable of giving the right pace and rhythm to all musical genres. And it goes down deep, so much that sometimes I felt the need to activate the cut below 40Hz, which was originally intended to limit the rumble of the turntables of that era. The bass articulation is good, as well, and it's difficult to explore the physical limits of the bass range, even with the most modern killer tracks, like the usual Angel by Massive Attack. Electric bass, kick drum and double bass are always clearly distinguishable, and with certain very bass heavy recordings - which did not exist at the time - perhaps the bass range might appear a bit too...heavy.

The mid-bass range, i.e. the preferred hunting territory for these 11.5 cm drivers, is rich, with some excessive bloom from time to time. This always makes the sound quite full and big. However, male voices are not affected, and always remain quite balanced. The drivers cope well in the mid-range area as well, so that female voices are clean, crystal-clear, and never annoying or fatiguing. Of course, the sometimes excessive introspection of modern high-end speakers, which make you perceive if the singer has a slightly crooked tooth, is missing but the whole content of the lyrics is there, even with big choirs. Indeed, it seems that the absence of a crossover network is highly beneficial, given that the Bose 901s juggle with extreme ease to unravel the most complex vocal plots. As an example, I cite the final crescendo of Cantate Domino, the eponymous track of the famous Proprius recording, where modern and highly rated speakers occasionally show traces of confusion and tend to scream more they should. Not so the 901s.

Percussion instruments benefit from the weight the bass range and the responsiveness of the mid range. Again, no modern hyper-realism here, of course, but let's not forget that there is no tweeter to speak of. However, the high range is mostly correct (and, in any case, it is adjustable) and well defined, perhaps not sparkling and bright as today, but the pizzicatos of the guitar, the cymbals of the drums and the environmental effects are reproduced with good realism. After a while you get used to this non-x-ray presentation and focus on the music only.

The dynamics that these old speakers are able to express, thanks to their unbelievable power handling, is very impressive for its era and still very good by modern standards. It's not a razor-sharp sound, as attacks and especially decays are less rapid, but the various differences in level, both micro and macro, are reproduced in a convincing way and never, I say never, does the sound becomes boring, mushy and sluggish, as it happens with many, many vintage loudspeakers. For sure, the punch isn't missing!

It is also worth highlighting the maximum sound pressure the 901 can generate. They reach their limits, sounding compressed, when the sound level meter, positioned a good 3 meters away from them, shows peaks of 105 dB (!!!). This is a performance unknown to the vast majority of speakers of the time (Klipschorn and similar designs aside) and difficult to match even for modern and expensive speakers. Clearly, this is a datum of little interest for the 99% of audiophiles who, under the best conditions (nobody's home etc.), can attain peaks of 90dB at the listening point (N.B. over 100dB it is hard to share a conversation with someone close to you). Anyway, so high listening levels, for such an old design, prove the quality of the drivers was/still is very high, even by today's standards.

Finally, let me stress the most feared and misunderstood point about the sound of the 901s, namely their sound-staging ability and their spatial image. Given that the sound that reaches the listener come from the reflections of the rear wall, one might expect a blurred image that wanders around the four walls of the room, a kind of indistinct surround sound. Surprise, surprise...the 3D soundstage the 901 can create is very similar to that of a good traditional loudspeaker. The 3D is very large, and occupies the space behind the speakers and between them, exactly like any other loudspeaker. The height of the scene is not very high, but this mainly depends on the height of the speaker stands. I admit mine are at the lower limit suggested by the Bose manual.

Instruments and singers, though not exactly sculpted in the virtual stage, occupy distinct positions, behind the line of the speakers or in front of them, with no trace of confusion whatsoever. So, if you were expecting a modern surround type sound...get ready for a shock! I challenge anyone to understand, listening with eyes closed or with the speakers hidden by a curtain, that the sound comes from a speaker that fires towards the rear wall. This, to be honest, has been a surprise for me as well. The speakers, despite being quite large, tend to disappear, and leave this excellently sized stage to recreate itself in front of the listener. Mr. Amar Bose was evidently not naive and knew what result to achieve and how to achieve it. It certainly isn't the gigantic, hyper-detailed, 3D image, which remains suspended in the air that a good modern high-end speaker can create, but it is better than that of many commercial speakers of even high cost.

Criticism

Personally, I don't feel like making any particular criticism on a 1968 design that can still be listened to today with great amazement. Room interaction is slightly more critical than with traditional speakers, so you need to experiment a little more to get a good balance. And, of course, the sound does not have all the definition and transparency of a good modern speaker but, believe me, these first series 901s can seriously embarrass more than one competitor, also expensive ones. In my opinion, much of the criticism that came when the 901 was introduced to the market was due to the inability of most tube amps of the time to properly drive and control these 18 drivers. Let's not forget that the first silicon transistors made their appearance at the end of the 1960s, and those amplifiers were nowhere near the performance of modern solid state amplifiers.

Conclusions

When I review a speaker or HiFi component I always ask myself two final questions: “Did I have fun?” and “Could I happily live with it”? The answer to the first question is a loud YES. Actually, I would say that listening to these 901s has been one of the most fun experiences of recent years, both for the amazement generated by the quality of the modern sound of a speaker designed in 1968, and for its intrinsic capacity to involve the listener. Maybe it's not a perfectly linear sound, but damn, it is viscerally engaging and musical! The answer to the second question is: well, it depends! If I didn't have to be a reviewer I could probably live with these 901s, but they are not introspective enough to allow me to adequately determine the differences between other components, an essential characteristic for a “work tool”.

When all's been said and done, I have no doubt in assigning these Bose 901s a well-deserved place in the Olympus of loudspeakers which, for different reasons, have left their indelible mark in the history of high fidelity. Well deserved, posthumous congratulations go to Amar Bose and Sherwin Greenblatt, who had the ability and the courage to think and design in a revolutionary way. How many of today's high end designs will be remembered in 60 years?

• [Back to Part I: history of the design and designers, urban myths, differences between the different series]
• [Back to Part II: installation, optimization, equalizer use]

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Copyright © 2024 Lucio Cadeddu - editor@tnt-audio.com - www.tnt-audio.com

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