My music teacher's Bose 901's

[Guest Americain]

I'm pasting this from the News Forum to repeat it here as it pertains to a high fidelity experience I had as a sixteen year old in 1971. I'm an AR man but I've always admired Bose and what they accomplished in the 1970's. The 901's were fascinating despite their peccadillos. I had a pianist/music teacher in high school and he got himself a pair of 901's in 1971. He swore by those speakers and nobody I know would question his perception of what a live piano sounded like. To him it was the closest thing to a live performance he'd ever experienced. He still owns those original 901's to this day and wouldn't give them up for anything. That to me is interesting.

[soundminded]

I'm pasting this from the News Forum to repeat it here as it pertains to a high fidelity experience I had as a sixteen year old in 1971. I'm an AR man but I've always admired Bose and what they accomplished in the 1970's. The 901's were fascinating despite their peccadillos. I had a pianist/music teacher in high school and he got himself a pair of 901's in 1971. He swore by those speakers and nobody I know would question his perception of what a live piano sounded like. To him it was the closest thing to a live performance he'd ever experienced. He still owns those original 901's to this day and wouldn't give them up for anything. That to me is interesting.

I have both original Bose 901 and Teledyne AR9. I've re-engineered both and have tried to make them sound as much alike as possible (running back and the 30 steps between rooms at times.) Because I'm working on a project with some possibilities, I can't tell you everything but I can give you some insight into what your piano teacher heard and why he probably felt the way he did.

Take a look at a grand piano. Do you see the strings? Do you see the hammers? What about the harp? How about the sounding board? Unless you are standing right over it you will not see any of these elements which make the sound, just the side of the case and the closed lid. How much sound that the piano produces reaches your ears directly? In most cases......NONE OF IT. It is all reflected off the surfaces in your room which is why it fills the entire end of the room it's in with sound enveloping you if the room is in a house like a living room. You can prop open the lid and it will act as a reflector directing some of the sound radiated upward at you but scattering much of it too. It will also be louder. Now look at a spinet and an upright piano. How much of the sound that they produce is directed at you? If you said none of it again, you are right it all comes out of the back which is usually a few inches from a wall. Now look at a clarinet or an oboe. See where the sound comes out? That's called the bell. Watch someone play one and note where it is pointed. Down towards the floor. Virtually all of its sound scatters before it reaches you. Same for a trumpet, trombone, tuba, bassoon, in fact most instruments blown into. Sometimes a saxophone will be pointed at you. If someone points a trumpet or a clarinet in your direction and blows into it, you will probably want to cover your ears. String instruments are interesting. How much sound actually comes from the string itself? Go to a music store and pick up an electronic violin that is turned off and draw a bow across it or pluck it. Very soft isn't it? That's the sound of the violin string itself, the instrument has no body. Now look at a real violin. See the f holes? Thats where some of the sound comes out and it scatters in all directions when it does. Unless you are standing next to the violinist, they will not be pointed at you. And of course the body of the violin vibrates mostly on its top and bottom launching sound waves in many directions. In fact, with few exceptions, the human voice being one of them, the guitar another, most instruments project little or no sound in the direction of the listener. Now what about your AR speakers (or anyone elses conventional speakers for that matter?) They project all of their sound in your direction. But they do not do it uniformly (frequency wise) the way a human voice or guitar does. In general, the higher the frequency applied to each driver, the more directional it becomes. In fact for most tweeters, the top two thirds of the highest octave is projected almost entirely directly at the listener, the relfected sounds off nearby surfaces have NO high frequencies at all. How can it possibly sound like music? It sounds like what it is, an imitation of music coming out of a box.

Bose took an entirely different approach and we could spend a lot of time discussing the pros and cons (and we undoubtedly will) but one thing he got right, he did not project most of his sound at the listener. Instead he driects it at the walls to the side and behind the speaker. Optimally, this will make the sound appear to come from a much larger source. One criticism of Bose 901 that I think Consumer Report or someone had was that it made a piano sound like it was 8 feet wide. My Steinway M is only 5'-6" but a Steinway D concert grand is 8'-9" and a Baldwin S-10 Concert grand is 9'-10" just about in line with what was delivered as a criticism by someone who probably never even saw a piano, let alone played one or listened to someone who did. Insofar as my re-engineered 901s are concerned, how large a piano sounds played on them depends largely on how they were miked. When they are miked from a distance, they are reduced almost to a point source, just what you'd hear if you were at some distance from a real piano.

[Guest Jethro]

I imagine a piano also fits within the 901s frequency response range...

I've alway found the 901 sound stage very interesting too...a live piano is a great example. Imagine if one could send have hundreds of drivers on a plane and very the phase signal to each...hmmmm

[Guest Americain]

Soundminded, your post about the negative comments about the sound stage of the 901 remind me of a joke I heard thirty years ago. An audiophile goes to a symphony concert for the first time and complains that the cellos are making too much distortion. *drum roll please!* I never owned 901's but lusted after them in the early 1970's. I settled for a new pair of Bose 501's which were a more conventional two-way design but still utilized reflected surfaces to widen the sound stage. I sold those to my college room mate two years later and eventually got into my current AR-3a's two years after that. But I still think about those 501's and how much I liked them at the time.

[soundminded]

I imagine a piano also fits within the 901s frequency response range...

I've alway found the 901 sound stage very interesting too...a live piano is a great example. Imagine if one could send have hundreds of drivers on a plane and very the phase signal to each...hmmmm

As I've reported elsewhere, IMO the Bose 901's fatal flaw is its frequency response. 40 years ago there wasn't much you could do about it but today, the problem is realtively easy to solve, almost a no brainer if you are patient and persistant. It took me about 2 1/2 years once I decided to tackle it. (This is the original version, only Series II is comparable. Solutions for other versions would have entirely different details.)

There are 2 problems in the bass region as I see it. ee magazine reported a peak of 7db at around 500 hz which they said was inaudible. In my room it was around 6 db at 250 hz referenced to 1 khz and it is very audible. This was the likely result of the deliberate effort to raise the system resonance above 180 hz where Dr. Bose said in his white paper that the phase shift associated with bass resonance is no longer audible. This is in direct contrast to what other designers do which is to push the resonance frequency as low as they can. This undamped resonance peak is easily equalized out. The output falls linearly at 12 db per octave below resonance and crosses the 1 khz reference point output at around 125 hz. To obtain the low bass the 901 is capable of in proportion to the rest of the output, the system therefore needs an additional 10 to 12 db or so boost at 30 hz. This would extend power requirements beyond what was available at the time and also limits the system's maximum loudness if the program material has lots of deep bass. It also shakes up everything in the room including a turntable. It will eat up the 128 wpc I have available to it right now on some material at low levels but can play most recording fairly loudly in my 14 x 14 room which is on the live side. More power and more 901 systems can of course get the maximum usable output to whatever level is desired. At current prices for used systems and low cost high powered amplifiers in the many hundreds of watts, this is not a real problem.

The the other real problem which is not merely a matter of equalization is in the treble. A 4" midwoofer makes a really lousy tweeter. Most reviews said the system was good to about 12 to 14 khz but I think this was pie in the sky. Even if it were true, dispersion of the front driver at those frequencies would be awful and unless you sat on axis, you'd never hear it. In fact on most program material, the quantity of high frequency sound needed to correct the problem is remarkably small, the real challenge being its quality. This is not a matter of using expensive tweeters, the 4 per channel 3/8 " mylar tweeters I used only cost about $6 each. It's a matter of the right dispersion pattern, the optimal ratio of reflected to direct sound (12:1 in my case) for the room, the right crossover frequency (9khz first order worked well for me) the right difference between the hf contour of the indirect compared to the direct tweeters (a couple of db at 20 khz in my case) for the room and the optimal overall loudness compared to the main speakers. Also whether the tweeters are in phase or out of phase with the main drivers matters. (BTW, my setup is bi amplified.) All of this for my case was determined by trial and error and I expect, in another room, some of the parameters would change. As with any sound reproducing system further equalization is required to compensate for differences in tonal balance from one recording to another for the most accurate reproduction.

I'm not one given to hyperbole and this is certainly an industry where a great deal of ad money is spent to sell very little innovation it is tempting. All I can say is that I am very satisfied that frankly.....I have the best Bose 901s in the world. Within their maximum loudness capabilities, I'd put them up against anything I've ever heard....including my AR9s (the 9s will outperform it in loudness of the deepest bass though.) I'm tempted to buy more used units and convert them too but my ultimate speaker as I see it now combines the ideas of Bose 901, AR9, AR LST, and a few of my own in a very ambitious project. Perhaps one day I'll see if I can give these 901s a real run for their money.

[Guest Jethro]

All I can say is that I am very satisfied that frankly.....I have the best Bose 901s in the world. Within their maximum loudness capabilities, I'd put them up against anything I've ever heard....including my AR9s (the 9s will outperform it in loudness of the deepest bass though.) I'm tempted to buy more used units and convert them too but my ultimate speaker as I see it now combines the ideas of Bose 901, AR9, AR LST, and a few of my own in a very ambitious project. Perhaps one day I'll see if I can give these 901s a real run for their money.

Do you have any pics you can post of your 901s? Love to see that tweeter arrangement.

Any phase issues with the multiple driver arrangement?