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post #211 of 216 Old 05-15-2015, 05:24 AM
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Originally Posted by dsrussell View Post
They have 4-inch drivers, if memory serves me, and had shocking bass response, which is based upon their "active equalizer" module.
They will go decently low, though certainly not to 30Hz, as the driver Fs is 80Hz. EQ'd or not they simply cannot go low with any authority, no matter how much power they're given. The displacement (Vd) of the 4.5 inch Bose driver is 20cc. That makes the displacement of all nine drivers 180cc. A ten inch sub driver with a modest 10mm xmax has a Vd of 350cc.

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post #212 of 216 Old 05-15-2015, 11:17 AM
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Originally Posted by Bill Fitzmaurice View Post
They will go decently low, though certainly not to 30Hz, as the driver Fs is 80Hz. EQ'd or not they simply cannot go low with any authority, no matter how much power they're given. The displacement (Vd) of the 4.5 inch Bose driver is 20cc. That makes the displacement of all nine drivers 180cc. A ten inch sub driver with a modest 10mm xmax has a Vd of 350cc.
Not surprisingly, I no longer have the printed frequency graphs, but I do remember them hitting somewhere in the mid 30 Hz range or a bit lower, before dropping steeply. I actually do have the purchase receipt from 1976 … go figure. But these little puppies were impressive with their bass response for such a small speaker. And I did buy these back in the day when Bose actually published specifications … to an extent (not that I would trust the veracity of those published specs). BTW, you're right again (are you ever wrong?). I just looked at my old manual (yep, still have that too), and they are 4-1/2 inch drivers.

The key to the 901s was proper setup (which was a tremendous headache) and driving them with a very powerful amplifier. When Bose offered me a 60 percent discount on their current 901s (since they couldn’t/wouldn't fix -- re-cone/re-edge -- that old of a speaker), I decided to go in a different direction. Smart move on my part .

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post #213 of 216 Old 05-15-2015, 12:10 PM
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Originally Posted by dsrussell View Post
Not surprisingly, I no longer have the printed frequency graphs, … .
This is a Series IV, with EQ.
http://www.billfitzmaurice.info/images/Templates/charts/Bose901.jpg

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post #214 of 216 Old 05-15-2015, 12:27 PM
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Pick up a pair of used Adcom GFA 555II's and run them bridged as monoblocks. They last forever and you can have them bench checked and replaced the 4 main capacitors for about $30 each if necessary. A lot of people modify them to perform as well as a Bryston and other way more expensive amps.

The ADCOM GFA-555 II is among the world's greatest audio power amplifiers of all time. It was designed by the legendary Nelson Pass, whose Pass Labs amplifiers today sell new for five figure price tags. Considering that you can get a used GFA-555 II on craigslist for about $250 - $350, it would be hard to find a better bargain for high-end amplification.


RATED POWER:

200w x 2 @ 8 ohms .04% THD
325w x 2 @ 4 ohms .04% THD
600w x 1 @ 8 ohms .09% THD (bridged)
850w x 1 @ 4 ohms .09% THD (bridged)

Stable to 2 ohm loads
No fan


TESTED POWER

While only rated for 200 watts per channel into 8 Ω, it easily put out 260 watts from each channel simultaneously at only 0.007% THD into 8 Ω. Measured with tone bursts, it easily put out an undistorted 370 watts per channel into 8 Ω.


That's about $700+ total for two mono block legendary amplifiers putting out 600w to 850w per channel


http://www.stereophile.com/content/a...-atkinson-1990

http://www.kenrockwell.com/audio/adcom/gfa-555-ii.htm

http://www.audioreview.com/cat/ampli...6_1583crx.aspx


-------------------------------------


BTW, I ised to have Bose 901's with a Phase Linear Amp and PreAmp back in the day. People on AVS like to bash the Bose 901's but I liked the big wide sound field they created. Plus frankly, I was young and hadn't heard anything better. That being said, I have to agree that they really do sound distorted and you can have the same effect AND accurate sound.

I sold my 901's once I discovered Magnaplanars and electrostats and other dipolar speakers. They easily create the same wide sound stage but without all the distortion inherent to the Bose 901 design. When you bounce sound off a wall you roll off and muddle the sound because you're basically listening to 1st and 2nd order room reflections without the direct waveform from the speakers. Yes, the Bose EQ unit tries to put back what was lost and get rid of the aberrations that were created, but it's not the same as just reproducing the original signal.

Used Magnapan speakers can be picked up on audiogon for very reasonable prices. There's a pair of MG III's listed right now for $900. Give them a listen and you's never go back to Bose ever again.

http://app.audiogon.com/listings/pla...35-milpitas-ca
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post #215 of 216 Old 05-15-2015, 12:36 PM
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Quote:
Originally Posted by Bill Fitzmaurice View Post
This is a Series IV, with EQ.
http://www.billfitzmaurice.info/images/Templates/charts/Bose901.jpg
As usual, thanks a lot, Bill.

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post #216 of 216 Old 05-15-2015, 12:48 PM
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Originally Posted by Peterc613 View Post
BTW, I ised to have Bose 901's with a Phase Linear Amp and PreAmp back in the day. People on AVS like to bash the Bose 901's but I liked the big wide sound field they created. Plus frankly, I was young and hadn't heard anything better. That being said, I have to agree that they really do sound distorted and you can have the same effect AND accurate sound.

I sold my 901's once I discovered Magnaplanars and electrostats and other dipolar speakers. They easily create the same wide sound stage but without all the distortion inherent to the Bose 901 design. When you bounce sound off a wall you roll off and muddle the sound because you're basically listening to 1st and 2nd order room reflections without the direct waveform from the speakers. Yes, the Bose EQ unit tries to put back what was lost and get rid of the aberrations that were created, but it's not the same as just reproducing the original signal.

Used Magnapan speakers can be picked up on audiogon for very reasonable prices. There's a pair of MG III's listed right now for $900. Give them a listen and you's never go back to Bose ever again.

http://app.audiogon.com/listings/pla...35-milpitas-ca
Ahhh, yes. Youth! Peter, you and I have a very similar story concerning speakers after the 901s . The 901s, not nearly as accurate and pristine as ESLs and Planar-magnetics (nor with the incredible high end and depth of soundstage), gave one a soundstage that spanned the entire wall, which was difficult to forget. After hearing full panel ESLs (Martin Logan) several decades ago, I knew that was the new direction I would be heading sooner or later. I guess I can thank the 901s for that .

Music area: Magnepan 3.6, McIntosh MC2205 & C48, SVS SB13-Ultra, Oppo BDP 95 and assorted equipment.
Movie area: EMP Tek R5Bi, PSA XS30, Denon X2000, Oppo BDP 83.
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