Bose 901 loudspeaker

The Bose 901 has created more of a stir in audio circles than any other loudspeaker we can think of, with the possible exception of the original Acoustic Research system. Much of the 901's popularity is attributable to Julian Hirsch's rave report in Stereo Review, and there is no doubt but that Amar Bose's compellingly convincing ads had their effect, too. But these things alone could hardly account for the 901's popularity.

Perhaps the most important single factor in the 901's sales is its awesomely spacious sound, which makes other systems in a showroom sound a bit trivial, as if the Bose is the Truth and the Light, and the others are just playing around. The 901 sounds fantastically open and spacious, with a big, fat low end and a socko you-are-there presence that seems to put the performers right in the room, surrounded by the original auditorium.

We were duly impressed by these qualities, too, and reported this in our preliminary report in the last issue. But we were less impressed by some other qualities of the 901, one of which was not altogether the fault of the system.

We have observed in the past that some loudspeakers seem to be more critical than others of placement in the room, and while we have never definitely established what it is about a speaker that affects its room sensitivity, we do have some ideas on the subject.

Standing waves, which determine to a major extent a small (in comparison with a concert hail) room's acoustical coloration, are most effectively set into resonance by soundwaves originating from the room corners. The fact that, in a living room of typical size, the strongest standing-wave resonances usually occur at low frequencies, is the main reason why putting a speaker in a corner will produce the most bass-heavy sound. Once we get out of the corner, though, the efficiency with which each standing wave is stimulated will depend on the speaker's precise location relative to the room corner. Two feet out from the corner, and it may only "tickle" the major resonance in the room. That peak then will be less severe than with the speaker cornered. Three feet out, and that particular resonant mode may not be excited at all—the response may be perfectly smooth there but another resonance, which may have been completely suppressed two feet from the corner, may now be fully excited, producing a peak at another frequency.

The larger the room, the less critical the speaker placement is likely to be, but in many typical listening rooms, a change in speaker placement of as little as a foot can make the difference between a sodden, suffocatingly heavy low end and a tight, well-defined one.

The crucial factor seems to be the location in the room from which the woofer(s) are feeding energy into it. Thus, it is often (usually, in fact) possible to obtain flatter overall response with a single relatively small woofer, which radiates from a small area, than from a multi-woofer system whose low end radiates from a general area that may be several feet wide.

By the same token, loudspeakers which radiate their lows in one direction (they are nondirectional after they leave the speaker) seem less prone to excite all the room resonances than ones which radiate from front and rear or front and sides. True omnidirectional (360-degree) bass radiators make it harder still to control standing waves, and that appears to be one of the problems with the Bose 901.

The 901 is neither an omnidirectional radiator nor a true doublet (front-and-rear) radiator. Most of its energy comes from a broad angle at the rear; a single driver in front delivers but a small fraction of the total radiated energy. The entire audio spectrum is radiated from both front and back, with back output predominating. The back wave is then supposed to be reflected from the wall behind the speakers, and these reflections "spray" the sound all over the listening room. The effect, as far as bass frequencies are concerned, is that the room is being stimulated, not by a pair of small surfaces, but by a pair of very broad areas. And the result is that, if there are any standing waves possible in that room, they will all be stimulated to the fullest. And although the 901 speakers are less critical of room placement insofar as stereo imaging is concerned than are most other systems, their approximate locations are nonetheless circumscribed by the requirements of a nearby rear wall and the usual dictates of symmetrical placement in the room, so their bass performance ends up being more dependent on the vagaries of the room than on the inherent capabilities of the speakers.

Thus, some 901 installations will have deep, tight, and quite well-defined bass, while others (in the majority) will exhibit uncontrolled bass resonances at frequencies which are entirely a function of the room dimensions. This no doubt explains the very widely conflicting reactions of different listeners who auditioned the Bose 901 in stores or purchased them for use at home.

The 901 equalizer (which connects between preamp and power amp) does have a switch position that attenuates the range below about 50Hz (for reducing "turntable rumble and other low-frequency disturbances") and this can help to alleviate the situation in many cases, if used. But since bass attenuation is a dirty word to most audiophiles, fewer people use it than don't, which is hardly the fault of the speaker. The filter cannot, however, cope with resonances above 50Hz.

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dalethorn's picture

So far I haven't been able to find the original Bose 901 review on the Internet - the review which contained the phrase "Bose is best, big or small, high or low."  I've always wanted the 901, just like I always wanted a set of Klipschorns.  But getting the best that either of those systems are capable of (and the only reason to have them) requires a listening room the likes of which I've never had.

GKearny's picture

I've had some BOSE 901s since 1999, and they ROCK when set up in my front yard. With the complete ABSENCE of room resonance, and connected to an ACURUS linear power amplifier, they SOUND LIKE WE ARE ATTENDING A LIVE CONCERT! I have rocked my entire neighborhood with Wagner's Ride of the Valkyrie, and the original BOSTON album! I think that the BOSE 901s are, with the addition of a LOT of horsepower ala a linear power amp, sound WONDERFUL. Our house is made of concrete blocks, and we have a solid rock veneer wall, and when we set up the BOSE 901s to reflect off of this heavy, rock-hard surface, the amount of sound that is projected is worth WHATEVER it costs! WE LOVE OUR BOSE 901s ! Gerry K in Arizona

drblank's picture

I know a lot of people want to get their audio system sound like they are at a concert. The problem is that concerts don't have really good room acoustics or sound systems.  Obviously, if the recording is a live recording, we hope that it sounds like we are at the concert, but having the speakers basically rely on bouncing audio from the back as the main source is actually bad.   Some people like omni directional speakers like MBL, or others that are simlar in design, but they don't rely mostly on bouncing the sound from the rear.   With the 901's, you are actually listening to what you want less of, reflected sound.

I had an acoustic engineer come to my home to take some measurements and give me his recommondations for room treatment as my room measurements were probably the worst you could have.  a square room with a pitched vaulted cieling with a drastic slope to it.  He explained to me that it's good to have reflected sound, but you don't want too much as it removes detail and coherancy from the music.

When companies like ASC and others work with a client to measure room acoustics, they work with Articulation measurements of the room and they measure the direct sound compared to the reflections and they want to create a natural room sound rather than having it too dead, too live where the reflected sound is as loud as the direct sound coming from the speakers.

The 901's just simply do it wrong.  If the front had a bunch of drivers and the rear sides had only one driver, that might be better.

One thing to note.  When you walk into a Bose dealership or Bose Store, don't let them use those CDs that are produced by BOSE.  I talked to a dealer that carried BOSE for a short period of time and they explained to me that BOSE produced demo CDs that were mastered to sound good on BOSE systems, but when you listened to the same CD on another, they sounded like crap so those demos they use to sell the speakers mislead the consumer because most of the recordings you listen to weren't mastered specifically for BOSE speakers.  The local dealership that told me this doesn't carry BOSE anymore and the only reason why they carried the line is they got a lot of people asking for BOSE because of BOSE marketing and they seccumbed under the pressure of customers, and in the process, they got ribbed by their higher end customers like myself, but in the end, they dropped the line as people would actually walk into a higher end store and once they started listening to companies like Paradigm and others, they became disinterested in BOSE and then sales started to wain.

Best advice I can give someone is use your own CDs, and go to a variety of audio stores (not the big box stores) and start REALLY listening to a variety of speakers, there are plenty of really good products on the market that walk all over BOSE.  Paradigm is just one of many, there are Martin Logan, and many other small companies that make nice affordable products these days.  If I wanted the omni directional sound, but couldn't afford MBLs or something in that price range, I would be looking at Martin Logan, Magnapan and a few others that sound so much better than 901's.

machelp's picture
smileday's picture

I do not understand the claim in the review that single small woofer system results in flatter response than multi-woofer system.

Contrary to that claim, we can achieve flatter in room response by increasing the bass radiating area. That is because we can make the dip (cancellation null) in bass in the frequency response curve less deep. Some designers utilize large bass radiation area. Real world product examples include PSB T3 that was reviewed in Stereophile. PSB T3 has multiple woofers for frequencies below 450Hz. Moreover, the woofers are placed apart, not as close to each other as possible.