World's finest sounding Bose 901s????

[skeptic]

I've always said that the main failing of Bose 901 series one and two was their lack of a high end. Subsequent versions three through six also lack the lowest octave as the manufacturer went from an acoustic suspension design to a ported design. The main reason for this shortcoming in series 1 and 2 as I see it is the inability of a 4 inch driver, especially one designed to handle low frequencies to overcome its inertia to the degree necessary to fully reproduce high frequencies. And even if it could, the front firing driver would not have very good dispersion due strictly to its diameter. This may have been less than critical in the sixties and seventies when most loudspeakers did not have a very bright or extended high end response but in the eighties and nineties as brighter speakers became the vogue, this speaker was left in the dust and has been highly discredited by most audiophiles to the point where it's routinely derided and bashed mercilessly. For those wanting what is considered accurate by today's standard, Bose 901 our of the box would be a very poor choice indeed and so maybe the criticism is to a large extent justified except for those who would forgo its severe tonal imbalance shortcomings for the special attributes of the direct reflecting principle.

I'm the kind of person who wants to have his cake and eat it too and I don't give up easily. I've made half hearted attempts in the past to fix this problem but now I've made a real effort and the results have paid off beyond my best expectations. I've added four tweeters to each chanel mounted right on the speaker itself secured to the top molding except for the front tweeter which is secured with double sided tape. The front tweeter is similar to an Audax 3/8 poly without a shielded magnet and so is the one at the apex of the rear. This was done for mounting reasons due to their reduced depth. Two Dayton 1/2" polys are mounted on each of the angled rear panels and are similar to the Audax units. Each tweeter is crossed over with its own 2.7 mfd NPC which gives them a 6db per octave rolloff hinged (3db down) at about 9khz. They are connected in parallel and have a combined nominal impedence of 2 ohms. The system now consists of an Optimus 5 disc 1bit carousel cd player, a Marantz SR930 receiver and a separate AR amplifier to drive the tweeters. The Marantz receiver has the advantage of a 10 band equalizer and removable jumpers between the preamp and power amp. This allows the Bose equalizer to be placed in this circuit with the AR amp connected to its tape outputs. This means that the Marantz volume control controls the signal to the AR amp as well as its own power amp and the signal to the AR amp is unaffected by the Bose equalizer. The volume control on the AR amp serves as a "brilliance" control affecting the relative level of the tweeters to the main speakers. The AR amp has its bass control at full cut and its treble set flat. The bose equalizer is set to its indicated flat position. The Marantz equalizer actually is adjusted for additional bass boost, a cut to eliminate the known peak around 500 hz and a very gradual and slight rolloff above the midrange. The room is a 14 x 14 sunroom with a cathedral ceiling and the walls are over 50% glass so it is on the live side.

The results so far are outstanding which mean to me, wide flat response across the entire audio band, very clear highs which characteristically for a direct/indirect array are never shrill but exactly balanced, excellent stereo imaging everywhere in the room, and of course preservation of the direct reflecting basic character of the sound.

I may fiddle with the direct reflecting ratio of the array by inserting an 8 ohm resistor in series with the front firing tweeter ahead of the capacitor to alter the direct reflecting balance from 3 to 1 to 6 to 1 which is more in keeping with the rest of the system which is 8 to 1. I am also contemplating replacing the power amp section of the Marantz receiver with a Crown DC 300 or 300A as the Marantz does not have quite enough power for deep organ pedal notes at moderate to high levels. Other than that the sound is all I could ask for. Ultimately, I might even consider adding a second pair.

If you try something similar with a series 3 to 6, I'd opt for a pair of first class subwoofers as that version does not have much response below 40 hz.

[Lord_Magnepan]

Quote
World's finest sounding Bose 901s????
Quote

NONE !!!

I heard a lot of audio equipment, from the low budget series to the high end gear. I dont agree with many. But if there is one speaker that i would give the absolut worst grade ever then it would be a BOSE 901 (inklc. all others).

The 500$ a pair Magnepan MMG, or the Paradim mini Monitors or any other speaker sounds worlds better.

Greetings from Germany (unfortunalty BOSE came from here)

-Florian

[skeptic]

Perhaps you didn't read my posting or understand it. This has to do with a project which uses the original Bose 901 as an element in a more complex system. While that speaker of 3+ decades ago has limitations which make it unacceptable to audiophiles, it has many ingenious innovations which solve problems most other manufacturers haven't even addressed. By combining the best attributes it has to offer with other elements which overcome its limitations, it can yield results which are both very different from its original design intent and very superior. Don't dismiss what you don't understand out of hand. There is far more in this unique idea than meets the casual eye.

[skeptic]

It's easy to dismiss 9 four inch speakers in a small sealed box with a fancy tone control circuit for you amplifier as a crude stupid idea that doesn't work. And if that's all it was, it would very much deserve this criticism. But there is far more to it than that. After more than 35 years, what went into the original Bose 901 has mostly been forgotten in the obscure fog of audio ancient history and what has emerged in the more recent reincarnations of this idea is a less complete picture if you can find it at all. So at the risk of boring the few people who are familiar with this loudspeaker system, I will for the benefit of those such as Lord Mangepan who know nothing about its design review some of the basic concepts which went into it. This may help explain why it is a very attractive element, starting point, major component of my DIY project.

First of all, the idea of 9 acoustic suspension drivers in a small pentagonal enclosure addresses and solves several difficult problems simultaneously. Putting them in a small enclosure of about one cubic foot drives their resonant frequency UP, not Down which is the usualy goal of enclosure designers. Why do this? Dr. Bose determined experimentally that the phase shift which inevitably occurs at a speaker's resonance frequency becomes inaudible at 180 hz and above so by making the enclosure smaller, he gets resonance into the inaudible range. Below resonance, the speaker response falls off linearly with frequency making a simple hinged compensating filter a practical idea. The price is that you need very robust speakers and enormous electrical power to take advantage of it. The drivers were not a problem as CTS supplied them and each can handle 30 watts for a total of 270 watts per channel. Amplifier power at the time was a problem since only a few very expensive amplifiers had sufficient power to exploit their capability. When they were used to their full potential, tests by CBS Loboratories, Hirsch Houk Laboratories, and by the respected auidio eningeer Bert Whyte of Audio Magazine all confirmed what their ears told them and that was that the bass response possible from Bose 901 outperformed nearly EVERYTHING on the market. Most of the largest and most expensive horn systems from such respected manufacturers as Altec Lansing, Klipsch, Tannoy, and Electrovoice were no match for 901. Neither were the largest infinite baffle systems from Bozak nor the best acoustic suspension speaker of the time AR3a. Only JBL Paragon and possibly one or two other very large expensive systems were their equal. Even by todays standards, their bass outperforms many fine subwoofers and many expensive full range systems (remember I'm talking about series one and two, not later versions.)

By mounting the drivers on angled panels so that no baffleboard containing a driver is parallel to another surface, internal standing waves were ELIMINATED.

By using nine full range drivers, the secondary resonances, those minor peaks and dips occuring at random along the frequency response cruve are ELIMINATED because each driver contributes a small percentage of the sound and peaks in one driver are compensated for by dips in another. Therefore only the average response has to be considered in equalizing for very flat overall response.

By using the reflective surfaces of the room, the apparant source of sound is much larger than that box itself and as would be the case for a direct firing speaker. The hole in the middle effect is ELIMINATED. It also affords enjoyment of the stereophonic effect in most parts of a room where forward firing systems restrict enjoyment of the effect to a much smaller area. The drawback of this idea of course is that you have to have a suitable room and you have to carefully position the speakers to exploit the room acoustics. Many dissatisfied users either didn't or couldn't do this.

As I have said, the idea by itself was fatally flawed because of its inability to reproduce the critical octave between 10 khz and 20 khz. This rightly made it unacceptable to audiophiles then and even moreso now. The speaker has another relatively minor flaw and that is that its response within the range it can produce is still not flat, its major error being a broad peak in the 200hz to 500hz range. This was also confirmed in the independent laboratory tests in the late 1960s and early 1970s. That is now easly correctable with additional equalization.

By the early 1970s, the original idea had been fully exploited and it was time for Dr. Bose to move on. He had at least three options. He could abandon 901 altogether, he could modify 901 by doing what I did which was to make it a two way system overcoming its high frequency limitations, or he could modify 901 by radically redesigning it as a non audiophile loudspeaker making it a much more efficient ported design in an injection molded plastic enclosure (the wood you see now is just decorative window dressing), manufacturing his own drivers and taking complete control over the entire manufacturing process. This last option is exactly what he did. And history has proven that he made the correct choice. While audiophiles many not have liked it, his bankers and accountants loved it. Skyrocketing sales made it possible for him to build one of the most financially successful companies in the business. And there is nothing wrong with that, at least from his point of view and from that of those people in the market who DO NOT demand or require high accuracy in a sound system.

As a largely forgotten and derided product, original Bose 901 and nearly identical series II are available on the market in good to excellent condition for a mere $200 to $300. Pedistals run about $100 more. This make them an attractive starting point for a DIY project of the kind I have built. And I am so pleased with it, I will surely build many more of them. BTW, the Crown CE-1000 looks to be an excellent choice for powering these speakers. Providing 275 wpc into 8 ohms and 450 into 4 ohms (two pairs of 901s in parallel) they offer more than adequate power and are an outstanding value at $450 including shipping from Parts Express.

[E-Stat]

It's easy to dismiss 9 four inch speakers in a small sealed box with a fancy tone control circuit for you amplifier as a crude stupid idea that doesn't work.

As a fan of full range bipolar speakers, I believe that there are definitely desirable aspects to his design. I would think that the theoretically perfect speaker would be a full range design with seemingly infinite size and zero mass. What I never took a hankering to was his devotion to a primarily indirect radiation pattern. While I don't necessarily disagree that "89% of what you hear is indirect", his model would seem to work only in acoustically dead environments where the room itself is not contributing to the indirect sound. Image size with 901s always seemed bloated to me.

rw

[skeptic]

Supposedly, the theoretically ideal loudspeaker would be a point source presumably radiating equally in all directions. That's what people always said although I don't see any rationale for it. The indriect radiating pattern of Bose 901 is intended to create a secondary "virtual" re-radiating source which is very large, one of the characteristics of many flat panel loudspeakers. Unlike flat panel loudspeakers however which radiate up to 50% of their sound indirectly themselves, Bose accomplishes this large diffuse radiating surface or tries to with a small enclsure and using the reflective surfaces of the room. This makes successful installation and speaker placement even trickier than for flat panels. Not surprisingly, that alone will lead to many unsatisfactory installations. There is no doubt that the arrival of very early reflections of the same musical instrument from different directions will cause the "image" to not always be pinpointed, this is the same case as it is for real musical instruments. If you sit in a concert hall and close your eyes, unless you are fairly close to the front row, you would be surprised how poor the "image" is. Also when you are in a living room and someone is playing a grand piano, the reverberation is coming from all over the place. It sounds huge, and magnificent.

If you read Dr. Bose's research paper, you will see that the 89% reflected sound occurs in Boston Symphony hall (America's best acoustical space for music according to Leo Beranek) at 19 feet from the performing stage. Further back, the reverberant component is even greater. That having been said, one thing to keep in mind is that the relationship between the direct and reflected sound fields in Boston Symphony Hall and the relationships between the direct and reflected sound fields produced by Bose 901 in your home have virtually nothing in common. That line of reasoning to justify his direct reflecting design is without merit. The true justification for it lies elsewhere.

[skeptic]

The addition of an 8 ohm 5 watt resistor in parallel with the front firing tweeter and a 4 ohm 5 watt resistor in series with it has dropped the level of the front tweeter 3db relative to the rear firing tweeters. (The overall tweeter array output has dropped less than 1 db however.) This has changed the direct to reflected ratio of the tweeter arrays from 1:3 to 1:6 which is closer to the 1:8 ratio of the main array. The result has been ironically a much smoother frequency response in the upper midrang/lower treble and a reduction of the forwardness of the imaging. The entire imaging has been pushed back considerably making it resemble the original Bose 901 much more closely. Happily, the strange phasing effect which occurs without a forward tweeter to compliment the rear firing units hasn't returned. Further tweaking of the frequency response will be required but it looks like the ultimate goal of approximately matching the enhanced Teledyne AR9's overall response is within reach. However, as excellent at the Bose 901 bass is , it isn't clear that it will ever match AR9 without a second pair of units and a much more powerful amplifier if it can be done at all. The Marants SR930/Bose 901 series 1 can be pushed beyond the combination's limits, most likely the limiting factor being available power from the receiver.

[Sir Terrence the Terrible]

The indriect radiating pattern of Bose 901 is intended to create a secondary "virtual" re-radiating source which is very large, one of the characteristics of many flat panel loudspeakers.

Unfortunately these reflections are not in the recording itself, which contaminates the reproduction of the source. If accuracy is the result you are trying to acheive, then these speakers fail miserably.

Unlike flat panel loudspeakers however which radiate up to 50% of their sound indirectly themselves, Bose accomplishes this large diffuse radiating surface or tries to with a small enclsure and using the reflective surfaces of the room.

Once again, the room the speakers are in are not within the recording chain. Spraying the walls with sound does not lend itself to a even frequency response(comb filtering), nor does it accurately convey what the microphones picked up within the venue. In other words there is no way this speaker could accurately respresent the ambience of the recorded venue.

This makes successful installation and speaker placement even trickier than for flat panels. Not surprisingly, that alone will lead to many unsatisfactory installations.

Which makes this speaker unsuitable for 90% of the rooms out there. Which is another reason why they didn't sell well.

There is no doubt that the arrival of very early reflections of the same musical instrument from different directions will cause the "image" to not always be pinpointed, this is the same case as it is for real musical instruments.

Unfortunately microphones pickup the sources in a pinpointed way. The object of a speaker is to reproduce what is recorded accurately, not introduce spurious reflections in the name of realism. These multiple reflections hide detail, confuse imaging, introduces an uneven frequency response. All of these are undesireable if accuracy is the main point.

If you sit in a concert hall and close your eyes, unless you are fairly close to the front row, you would be surprised how poor the "image" is. Also when you are in a living room and someone is playing a grand piano, the reverberation is coming from all over the place. It sounds huge, and magnificent.

This logic doesn't hold up well under careful scrutiny. Even if you were in the first row in a concert hall, you are considerable farther from the source than you are in a listening room. Therefore you are hearing(especially speaking from the mids up) more reverberation than source even from that distance in a concert hall. In small rooms we are much closer to our speakers than the first row would be from the musicians. You therefore are hearing(especially in the mids and up) more speaker than reverberation. It takes a big space to create reverberation that is most noticeable to the ears(mid bass through midrange). Small rooms do not support that kind of reverberation. It has to be synthesized electronically using either delay, or phase manipulation techniques such as deccorolation.
A piano will not have any noticeable reverberation in the typical living room. It is just not large enough to support it. The rooms greatest influence will in the bass frequencies where it takes a huge place to develop audible reverberation tails

If you read Dr. Bose's research paper, you will see that the 89% reflected sound occurs in Boston Symphony hall (America's best acoustical space for music according to Leo Beranek) at 19 feet from the performing stage.

I have recorded a couple of orchestra's in Boston's Symphony hall(movie scores) we situate our microphones much closer to the instruments than 19ft, unless they were specifically tasked to pick up ambience(spaced omni's). We sit considerably close to our speakers than 19ft. So to use this as a reference for speaker design is foolish at best. Our rooms will never exhibit the frequency response, reverberation characteristics, or large scale ambience of Symphony Hall.

Further back, the reverberant component is even greater. That having been said, one thing to keep in mind is that the relationship between the direct and reflected sound fields in Boston Symphony Hall and the relationships between the direct and reflected sound fields produced by Bose 901 in your home have virtually nothing in common. That line of reasoning to justify his direct reflecting design is without merit. The true justification for it lies elsewhere.

Totally agree with you here. That is exactly Dr. Bose's reasoning for designing the entire direct/reflecting series however. So the whole principle behind the design of the 901 was flawed at its inception.

Skeptic, I cannot see how your modification help the sound of this speaker at all. By adding tweeters firing in seperate directions, you have moved a problem(comb filtering) from the midrange into the highs also. Also it really doesn't help the fact that these speakers still have no deep bass, and acerbate room modes and nodes. I think by adding these tweeters, it makes the deep bass seem even more non-existant.

[registrar84]

So you are a dealer for Magneplanar, no?


QUOTE=Lord_Magnepan]Quote
World's finest sounding Bose 901s????
Quote

NONE !!!

I heard a lot of audio equipment, from the low budget series to the high end gear. I dont agree with many. But if there is one speaker that i would give the absolut worst grade ever then it would be a BOSE 901 (inklc. all others).

The 500$ a pair Magnepan MMG, or the Paradim mini Monitors or any other speaker sounds worlds better.

Greetings from Germany (unfortunalty BOSE came from here)

-Florian[/QUOTE]

[registrar84]

Well stated. As someone who once owned a pair (wish I still had them), they were one hell of a speaker in 1971 (or maybe it was the drugs). I think he is a Magneplanar dealer!

It's easy to dismiss 9 four inch speakers in a small sealed box with a fancy tone control circuit for you amplifier as a crude stupid idea that doesn't work. And if that's all it was, it would very much deserve this criticism. But there is far more to it than that. After more than 35 years, what went into the original Bose 901 has mostly been forgotten in the obscure fog of audio ancient history and what has emerged in the more recent reincarnations of this idea is a less complete picture if you can find it at all. So at the risk of boring the few people who are familiar with this loudspeaker system, I will for the benefit of those such as Lord Mangepan who know nothing about its design review some of the basic concepts which went into it. This may help explain why it is a very attractive element, starting point, major component of my DIY project.

First of all, the idea of 9 acoustic suspension drivers in a small pentagonal enclosure addresses and solves several difficult problems simultaneously. Putting them in a small enclosure of about one cubic foot drives their resonant frequency UP, not Down which is the usualy goal of enclosure designers. Why do this? Dr. Bose determined experimentally that the phase shift which inevitably occurs at a speaker's resonance frequency becomes inaudible at 180 hz and above so by making the enclosure smaller, he gets resonance into the inaudible range. Below resonance, the speaker response falls off linearly with frequency making a simple hinged compensating filter a practical idea. The price is that you need very robust speakers and enormous electrical power to take advantage of it. The drivers were not a problem as CTS supplied them and each can handle 30 watts for a total of 270 watts per channel. Amplifier power at the time was a problem since only a few very expensive amplifiers had sufficient power to exploit their capability. When they were used to their full potential, tests by CBS Loboratories, Hirsch Houk Laboratories, and by the respected auidio eningeer Bert Whyte of Audio Magazine all confirmed what their ears told them and that was that the bass response possible from Bose 901 outperformed nearly EVERYTHING on the market. Most of the largest and most expensive horn systems from such respected manufacturers as Altec Lansing, Klipsch, Tannoy, and Electrovoice were no match for 901. Neither were the largest infinite baffle systems from Bozak nor the best acoustic suspension speaker of the time AR3a. Only JBL Paragon and possibly one or two other very large expensive systems were their equal. Even by todays standards, their bass outperforms many fine subwoofers and many expensive full range systems (remember I'm talking about series one and two, not later versions.)

By mounting the drivers on angled panels so that no baffleboard containing a driver is parallel to another surface, internal standing waves were ELIMINATED.

By using nine full range drivers, the secondary resonances, those minor peaks and dips occuring at random along the frequency response cruve are ELIMINATED because each driver contributes a small percentage of the sound and peaks in one driver are compensated for by dips in another. Therefore only the average response has to be considered in equalizing for very flat overall response.

By using the reflective surfaces of the room, the apparant source of sound is much larger than that box itself and as would be the case for a direct firing speaker. The hole in the middle effect is ELIMINATED. It also affords enjoyment of the stereophonic effect in most parts of a room where forward firing systems restrict enjoyment of the effect to a much smaller area. The drawback of this idea of course is that you have to have a suitable room and you have to carefully position the speakers to exploit the room acoustics. Many dissatisfied users either didn't or couldn't do this.

As I have said, the idea by itself was fatally flawed because of its inability to reproduce the critical octave between 10 khz and 20 khz. This rightly made it unacceptable to audiophiles then and even moreso now. The speaker has another relatively minor flaw and that is that its response within the range it can produce is still not flat, its major error being a broad peak in the 200hz to 500hz range. This was also confirmed in the independent laboratory tests in the late 1960s and early 1970s. That is now easly correctable with additional equalization.

By the early 1970s, the original idea had been fully exploited and it was time for Dr. Bose to move on. He had at least three options. He could abandon 901 altogether, he could modify 901 by doing what I did which was to make it a two way system overcoming its high frequency limitations, or he could modify 901 by radically redesigning it as a non audiophile loudspeaker making it a much more efficient ported design in an injection molded plastic enclosure (the wood you see now is just decorative window dressing), manufacturing his own drivers and taking complete control over the entire manufacturing process. This last option is exactly what he did. And history has proven that he made the correct choice. While audiophiles many not have liked it, his bankers and accountants loved it. Skyrocketing sales made it possible for him to build one of the most financially successful companies in the business. And there is nothing wrong with that, at least from his point of view and from that of those people in the market who DO NOT demand or require high accuracy in a sound system.

As a largely forgotten and derided product, original Bose 901 and nearly identical series II are available on the market in good to excellent condition for a mere $200 to $300. Pedistals run about $100 more. This make them an attractive starting point for a DIY project of the kind I have built. And I am so pleased with it, I will surely build many more of them. BTW, the Crown CE-1000 looks to be an excellent choice for powering these speakers. Providing 275 wpc into 8 ohms and 450 into 4 ohms (two pairs of 901s in parallel) they offer more than adequate power and are an outstanding value at $450 including shipping from Parts Express.

[muziekfreak]

For the many noobs out there...the bose "direct reflecting" idea is stil being used. Take a look at the newest B&w topmodel [YESS there is a new kid on the block!] 4x15inch seperate bass tower. And strange but true the high/mid towers consist of mids placed @ the side of the speakers

Take a look at almost all infinity classics like the kappa series,rs, and the topmodel IRS [V] were are talking about speaker from a few 1000dollars until 90000dollars. Alle have a few emits [Electromagentic Induction tweeters] @ the rear af the speakers.

Bose is to expensive for what the give in quality..i agree,. And yes the direct reflecting concept is outdated.

But please don't tell me that the system @self sucks...pure based on nonses. And for the great guy up here "A record is not recorded this way" Than you can kiss your maggies goodbye to the give as much from the front as from the back...besides a bose can play easy at 110db...you maggies will never make ik that far

No offence but just understand..What do want for sound?..it's al so subjective.

One other thing...bose dit sell very good at that time! Because the brand itself made a impression..."Bose.lets buy it the say its the best you can have!"

[Sir Terrence the Terrible]

For the many noobs out there...the bose "direct reflecting" idea is stil being used. Take a look at the newest B&w topmodel [YESS there is a new kid on the block!] 4x15inch seperate bass tower. And strange but true the high/mid towers consist of mids placed @ the side of the speakers

Just because a speaker has a certain design consideration that invokes a certain sonic character(and cost a lot) doesn't mean it is a great speaker. The job of a speaker is to faithfully reproduce the source, not impart it's own sonic charcater, or attempt to create a hall effect using spurious room dependant reflections. That is just creating a flavor instead of neutrality.

Take a look at almost all infinity classics like the kappa series,rs, and the topmodel IRS [V] were are talking about speaker from a few 1000dollars until 90000dollars. Alle have a few emits [Electromagentic Induction tweeters] @ the rear af the speakers.

Yes, because two channel ruled, they were attempting to create a speaker that sounded more spacious to cover up the limitation of two channel stereo. More speakers and channels is probably a better approach rather than purposefully making a speaker inaacurate for the effect.

Bose is to expensive for what the give in quality..i agree,. And yes the direct reflecting concept is outdated.

It was outdated from its inception. How can two speakers create the sonic flavor of a concert hall with its complex reflection pattern. It is impossible, our rooms are just too small.

But please don't tell me that the system @self sucks...pure based on nonses. And for the great guy up here "A record is not recorded this way" Than you can kiss your maggies goodbye to the give as much from the front as from the back...besides a bose can play easy at 110db...you maggies will never make ik that far

Sorry, but the speaker does suck. I was the one who made the statement about how records are recorded, and I do not, and would not own maggies. I do not own speakers that reproduce fake ambience(because that is exactly what it is. The 901 could probably do 110db. But not below 50hz, or above 6khz.

No offence but just understand..What do want for sound?..it's al so subjective.

One other thing...bose dit sell very good at that time! Because the brand itself made a impression..."Bose.lets buy it the say its the best you can have!"

Sound is subjective when you are looking for a certain flavor. I don't want a speaker that colours the sound to taste, I want one that will reproduce the electrical signal exactly as it comes into the speaker. No extra ambience, no extraneous reflections, and no extra colorations. It is pretty debateable whether they sold well or not, but they did leave an impression. Good and very bad!!