If you have pdf format (or JPG) you can send me to follow address:
kirschner-hifi@tiefbasswiedergabe.de
if you must perform a scanning - the schematic of equalizer is enough.
Thank you for your efforts
Galerie and Description about BOSE 901 Resurrection from a French Guy
Bose 901 II Equalizer
Equalizer schematics that I have receive in the meantime (schematics of newer models still needed):
Bose 901 II Equalizer
Equalizer schematics that I have receive in the meantime (schematics of newer models still needed):
And few worlds from me.
I'm also 901 owner... and listener
The problem I met was at the first place, the EQ. It's s-IV. They are designed long time ago, before CD and DVD players. And as we know, their output signal is about 2V. EQ s-IV and earlier are designed for tape deck, tuner and turntable signals, which is about 0.5V. The higher signal levels overload the EQ and begin distortions. That's why, if you use players without regulated outputs, or if your receiver or preamp inputs are not attenuated, you'll have problems with the quality of the sound.
I'm also 901 owner... and listener
The problem I met was at the first place, the EQ. It's s-IV. They are designed long time ago, before CD and DVD players. And as we know, their output signal is about 2V. EQ s-IV and earlier are designed for tape deck, tuner and turntable signals, which is about 0.5V. The higher signal levels overload the EQ and begin distortions. That's why, if you use players without regulated outputs, or if your receiver or preamp inputs are not attenuated, you'll have problems with the quality of the sound.
The other big problem of 901's is their sensitivity to the position and space they play. But you know this very well
Lately I use mine with The Bose Spatial Receiver. And even with this old vintage, with dry old capacitors and mash of switches and wires inside, I think, they sound well.
And my advice is - don't try to use them without the right EQ. It's waste of time.
Lately I use mine with The Bose Spatial Receiver. And even with this old vintage, with dry old capacitors and mash of switches and wires inside, I think, they sound well.
And my advice is - don't try to use them without the right EQ. It's waste of time.
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I'm always surprised, after all the years the 901 series has existed, that many people still think the active EQ is optional. I think this may be why the 901s have a reputation for sounding bad, for example, the old saying "no highs, no lows, must be Bose".
I do not know the original design goals for the 901 but since Bose obviously knew about the existance of woofers and tweeters when the 901s were introduced, I assume the use of just full range drivers was something that was found to produce the desired 90% reflecting/10% direct sound these speakers were intended to create (if I remember the advertisements correctly). I am just guessing but maybe the high frequency "beaminess" of a 4" driver produced a more spacious effect when all drivers were operating & pointed at various walls vs. using 4 separate tweeters. Or, using smaller FR drivers ("mid-tweeters") with a conventional large woofer, e.g. a 10" model, would cause the enclosure to be too large, negatively affecting sales?
While definitely not an audiophile speaker IMO, I would describe the sound the 901s produce as "pleasant" and inoffensive, sort of the sonic equivalent of vanilla ice cream: there is adequate high frequency detail - cymbals are clearly heard for example - but those details are not overly analytical or "tinkly" like so many modern speakers especialyl when reproducing rock/pop music; the mids are fine; and bass while not thundering is good enough for most rock, pop and jazz.
Btw I think the 901's mid-century modern styling still looks cool, especially the black version and especially when the Bose pedestals are used with them (they were used this way in a cellphone commercial about four years ago, located in a swanky, light-colored modern apartment).
I do not know the original design goals for the 901 but since Bose obviously knew about the existance of woofers and tweeters when the 901s were introduced, I assume the use of just full range drivers was something that was found to produce the desired 90% reflecting/10% direct sound these speakers were intended to create (if I remember the advertisements correctly). I am just guessing but maybe the high frequency "beaminess" of a 4" driver produced a more spacious effect when all drivers were operating & pointed at various walls vs. using 4 separate tweeters. Or, using smaller FR drivers ("mid-tweeters") with a conventional large woofer, e.g. a 10" model, would cause the enclosure to be too large, negatively affecting sales?
While definitely not an audiophile speaker IMO, I would describe the sound the 901s produce as "pleasant" and inoffensive, sort of the sonic equivalent of vanilla ice cream
: there is adequate high frequency detail - cymbals are clearly heard for example - but those details are not overly analytical or "tinkly" like so many modern speakers especialyl when reproducing rock/pop music; the mids are fine; and bass while not thundering is good enough for most rock, pop and jazz.Btw I think the 901's mid-century modern styling still looks cool, especially the black version and especially when the Bose pedestals are used with them (they were used this way in a cellphone commercial about four years ago, located in a swanky, light-colored modern apartment).
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I agree, so far you does not carry out a direct comparison with other model (e. g. equipped with Fostex full range), which is better in all respects.While definitely not an audiophile speaker IMO, I would describe the sound the 901s produce as "pleasant" and inoffensive, sort of the sonic equivalent of vanilla ice cream
OTOH, currently an old vintage speaker as the early series of 901 is much harder to beat than in those days, because the tendency of the sonic quality from today's commercial speakers have become significantly worse, even in the upper price class. Keep this always in mind.
I am looking for a diy project with cheap but good quality full range transducers with the same design goals than by the 901, but higher quality. Where I can find such projects (maybe here on diyaudio?).
Some examples of Chassis are follow:
SP-200X (for very large "901")
MCT PROFI SHOP (SPH-60X, not available in u.k.)
Check out also this thread:
http://www.diyaudio.com/forums/full...tional-arrangement-polarity-rules-wanted.html
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For me is still secret, why Mr. Bose chose such curved loudspeaker for his 901 projects, it isn't even and clear midrange, and then to pump them with EQ and tons of Dbals. But for sure, it's not about the price, and for sure results are good
By the way, I listen and a pair of 601s s-1, but they are fare from 901s, by my own
By the way, I listen and a pair of 601s s-1, but they are fare from 901s, by my own
I purchased the set of 901's I have a few years ago cheaply with the intent to use them just for the mid-range and add Woofer and Tweeter support to "fix" their deficiencies. Thus my screen name. I wanted to experience the magical surround sound effect too!
Having experimented many years ago with various subwoofer designs and types it makes me think he chose the 9 drivers he did because of how Spl increases in multiples. Two 10" woofers have more surface area than a 12", close to that of a 15" etc. A mid can stretch up and down in frequency range where a woofer can only go so high and a tweeter just so low. Since a mid will roll off with less Spl in the highs and lows just cut the Spl in the mid range to make it match the ends so to speak. Add wattage to bring the resultant "flat" level up.
....or he lost a bet or wanted to be talked about for years to come, could be any of the above.
Having experimented many years ago with various subwoofer designs and types it makes me think he chose the 9 drivers he did because of how Spl increases in multiples. Two 10" woofers have more surface area than a 12", close to that of a 15" etc. A mid can stretch up and down in frequency range where a woofer can only go so high and a tweeter just so low. Since a mid will roll off with less Spl in the highs and lows just cut the Spl in the mid range to make it match the ends so to speak. Add wattage to bring the resultant "flat" level up.
....or he lost a bet or wanted to be talked about for years to come, could be any of the above.
Are those two vents (ports) on the left and right sides in the 3rd photo posted by the OP in his first message? If so, I was wondering if the shape is just cosmetic to look cool, or did Bose at the time engineer a special kind of vent? If the two tubular shaped parts aren't vents, then what are they?
^ yep they're vents, along with the smaller but identical version for the single front-mounted driver. The tapered rod located in the center of the vent is designed to decrease air turbulence at high volume levels. When I used to sell audio in the early 90s, I remember placing my hand near one of them while some bass-heavy music was turned up particularly loud and the air rushing out felt like a (heat-less) hair dryer.
I guess no subs at the time (commercial gimmick like now) in the 70's & 80's, from what I remember, or LFE for the same effect.^ yep they're vents, along with the smaller but identical version for the single front-mounted driver. The tapered rod located in the center of the vent is designed to decrease air turbulence at high volume levels. When I used to sell audio in the early 90s, I remember placing my hand near one of them while some bass-heavy music was turned up particularly loud and the air rushing out felt like a (heat-less) hair dryer.
If anyone's interested, in the near future an online audiophile magazine will be testing the current version of the 901. Read about it, and the audiophile indignation
Which one? that would be interesting, a magazine that will not be afraid of being sued by Bose, that is.
Joke aside, it took me long time to get to a speaker that was good enough to replace them.
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