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Old 15th January 2013, 11:01 PM   #21
benb is offline benb  United States
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Quote:
Originally Posted by Soldermizer View Post
Inductor: I did look at the photo in post #4. I am guessing the man relaxing in his high rise loft is living in the advertising world. He has a pair of Bose 901 that don't require any cabling, nor is any type of electronic gear required to drive them. He has almost no furniture in a spotless room. This does not look like any real world living room I have ever seen. Who is the gullible one?
The man in the photo is described in this post:
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Old 16th January 2013, 12:22 AM   #22
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Quote:
Originally Posted by Soldermizer View Post

I just ordered a pair of the "Selenium ST200" tweeters...

Then to figure out how to hook an 8 ohm tweeter...
Where are you placing the tweeters? (in the middle of the baffle?, or just testing with them on top, may not be a bad idea)?
. A picture of the set (901 series) would help. series I & series II.
. We have to go to the originals xovers layouts for series I & II (links).
. Are you starting on the series I or II?
. How much you think is the (901) SPL (to match with the tweeter).
. You can use a variable L-Pad (for help/testing) with the high pass crossover.

Note (about design in general for soap opera and football lovers): pic.1 vs. pic.2 I like the idea of having clean rooms where we can concentrate on music. People hate the idea of not using loudspeaker cables when listening to the music because they can't understand (many musicians also don't have cables when playing the guitar on TV). Some people also prefer small rooms full of clutter where you don't have the space to move and besides it stinks. That's so wrong... shame on them!
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Old 16th January 2013, 12:43 AM   #23
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BOSE people think they are the new age messiahs.
That's why I love vintage BOSE's.
Quote:
“Bose Listening Room” designed by Bose Speakers. Here you can sit back and listen to the true quality of Bose products.
Bose Listening Room Bar Stools
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Old 16th January 2013, 01:06 AM   #24
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-3dB for crossover high pass (various with EQ box response) ~5kHz, 6kHz, 8kHz (atten. 5dB/one driver & back wall unequalized response), 12kHz.
Enclosures for Old bose drivers - diyAudio
Bose 901 series 1 & 2 equalizer - audiokarma
Bose 901 System - Equalizers By Roger Russell
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Last edited by Inductor; 16th January 2013 at 01:25 AM.
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Old 16th January 2013, 01:23 AM   #25
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I will probably use the pair of Bose 901 (series I or II -- no labels) that a prior owner ("victim"?) had re-drivered (is that a verb?). Plan was to pull out front driver only and replace it with the tweeter. How to wire it will require some thought. I know almost nothing about x-overs. I know I need at least one capacitor. Perhaps for testing, it would be easier to have it separate and feed it from the input (series R + capacitor). I know enough about audio electronics that putting the full range signal through the tweeter will not make it happy

Again, here is the tweeter that I will use:
http://www.parts-express.com/pe/show...number=264-348

My "design specifications" preliminary are more or less: I want the tweeter to be active from about 5K-20K. For initial testing, I agree that it will be easier to have the tweeter free mounted (there are, in fact, two pairs of 901s in my current system). Also, a 2nd amp (also a NU3000) is available, also a miniDSP if I need to tweak the x-over. Maybe that is the easiest thing to do: I can decide where I want the x-over to be and then, if I choose to make one, worry about a x-over design, something I know absolutely nothing about.

Last edited by Soldermizer; 16th January 2013 at 01:38 AM.
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Old 16th January 2013, 03:37 AM   #26
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Default Bose 901 EQ = Amplifier Killer

Quote:
Originally Posted by mlise View Post
Ed Long actually designed the original 901's. He begged Dr. Bose to use a tweeter, but Bose insisted on 9 identical drivers and an EQ box to bump the highs and lows
Anybody who is considering 901's should read Dr. Bose's White Paper on their design. The 901 EQ pumps up the Bass & Treble by 30db to counteract the 901's terrible low & high end. For those that don't understand db, 30db is 1000 times higher. So the pwr. amp is required to deliver 1000 times more power to the Bass & Treble, than to the Midrange. How many power amps can deliver That kind of pwr?

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Old 16th January 2013, 11:02 AM   #27
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It's not 30dB. Iirc, the bass boost has two positions, one is like 12dB, the other is either higher or lower than that. Regardless they require a high power amplifier.

As far as replacing the front driver with a tweeter - likely a not so good idea.
Better to run it on top. The other thing is that unless you need/want to maintain the original look entirely, I'd make a new hole in the front to mount the tweeter, and modify the grille cloth assembly by knocking a new hole in the grille assembly to give the new tweeter a hole.

IF the drivers have 3 ears, then they are not series 1, the original bose drivers had standard 4 ear stamped frames.

The wiring is series parallel, to give roughly a nominal impedance of between 4 and 8 ohms, the original reviews/specs will tell that.

Best not mess with that.
So your new tweeter(s) will go across the existing driver array. In other words, from the speaker connections, via a crossover, to the tweeter(s).
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Old 16th January 2013, 04:20 PM   #28
mlise is offline mlise  United States
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Hi,
I flush mounted a Vifa 1" silk dome tweeter in the front of mine and it worked great for use without the EQ box, and put an L-pad on the bottom, so I could use them with the EQ box. Definitely keep the 9 drivers and add the tweeter in parallel with them.

250 watts is plenty of juice. I accidentally had the grills flapping an inch and I'm surprised I didn't kill the drivers. I used a Harman Kardon Signature 1.5. More than that's definitely unnecessary.

M
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Old 16th January 2013, 04:36 PM   #29
Pallas is offline Pallas  Pakistan
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Beyond the midcentury modern appearance, I'm curious why interest persists in the 901. Bose themselves seem to have done an improved version of their direct/reflecting concept in their 601: more bass (larger cabinet, dual 8" woofers) and cleaner sound due to an actual crossover (be it electrical or mechanical, not quite sure) between the widebanders and the woofers.

A shisha lounge we frequent uses them as house speakers, and while they don't sound good, they're reasonably consistent-sounding across the space. I've thought about taking the basics of that design and experimenting with them as surround speakers, perhaps with four of the little 3" KEF eggs per side, or Aura NS3's.
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Old 16th January 2013, 06:47 PM   #30
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Pallas,

You use 901s or 601s?

Very different speakers.

The interest persists in 901s because they are classics, they put out a lot of sound in a small package, and as I said they sound pretty darn great playing Led Zep, assuming you have a mostly blank, flat, plaster & lathe wall, proper amplification and enjoy a big sound... I think one can do much better today by a variety of means, but that's coming from someone who has been there and done that 901 and variations thereof.
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