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 Post subject: Re: A big eye opening defect in Bose 901's!
PostPosted: Oct Sun 21, 2018 6:16 pm 
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Location: Lake Stevens, WA 98258
dberman51 wrote:
"No highs, no lows,
you pay thru the nose,
it must be Bose!"

-David


Thats original.

901's are quite good if you drive them with plenty of power, and place them correctly.


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 Post subject: Re: A big eye opening defect in Bose 901's!
PostPosted: Oct Mon 22, 2018 5:31 am 
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Location: Lincoln City, OR
Greetings to the Forum:

I guess it must depend highly on what sort of music you listen to. I myself listen to classical music exclusively. (Well, everything from baroque to romantic and even a little more modern stuff, but most people lump that all together into "classical" so for the sake of brevity, I shall do so also.)

For that format, the Bose 901's sound wonderful.

My wife is principal second violin in a symphony orchestra. I recently had occasion to accompany her to a rehearsal. They were in their usual venue, but instead of the usual heavy black curtain behind the orchestra, it was drawn aside and the orchestra was backed by some large plywood sets folded flat against the back wall. I had occasion to discuss the acoustics with one of the other musicians and remarked to him that the orchestra sounded much louder than usual... a rather different sound. He remarked that it sounded different on stage to the musicians as well. We discussed the fact that the orchestra cannot afford an orchestra shell at this time, but almost everyone wishes for one. So much for localized, non-reflected sound.

That's just the way it is in the classical world. How it works for four or five rock musicians, I couldn't say.

Looking forward to getting my equalizer built or set up, if one of the ones I have has sufficient range.

Regards,

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Jim T.
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 Post subject: Re: A big eye opening defect in Bose 901's!
PostPosted: Oct Mon 22, 2018 6:34 am 
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Greetings and thanks to all who responded. Thanks to jkoebel and others, I now have the response curve for the equalizer. I also have the service manual, which includes the schematic.

Unfortunately, all I have for the transistors is a Bose part number: 102437-2

Anyone have a clue what these might be? I could always build it with the ubiquitous 2N2222 but perhaps it might work better if I used something close to the originals.

Thanks,

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Jim T.
KB6GM


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 Post subject: Re: A big eye opening defect in Bose 901's!
PostPosted: Oct Mon 22, 2018 8:13 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Boston, MA USA
I suggest the 2N3904. I too have used the 2N2222 for everything but IIRC it's really optimized for switching. The 2N3904 may be better for audio.

-David


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 Post subject: Re: A big eye opening defect in Bose 901's!
PostPosted: Oct Mon 22, 2018 11:53 pm 
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Joined: Aug Sat 01, 2009 2:23 pm
Posts: 1655
Jthorusen wrote:
Greetings to the Forum:

I guess I will have to wake this thread up again....

I just managed to purchase a pair of Bose 901 Series II speakers... but of course, there was no equalizer available.

ARF member "jkoebel" posted to this thread with some images which I believe are the necessary response curves for Bose speakers including a curve for the 901 Series II's. I was able to see the URL when I sent him a PM, but the link now just goes to "Create Microsoft Account" page.

Hopefully he will get back to me, but in the event that he no longer frequents this forum (his last post on this subject was in 2017) I thought that I'd ask here as well and see if anyone else has the correct response curve for the equalizer.

Thanks,


If all else fails, you can buy a programmed MiniDSP that will give you the exact curves you need. https://deercreekaudio.com/products/bos ... -equalizer

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John Stone
Antique Radio Club of Illinois


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 Post subject: Re: A big eye opening defect in Bose 901's!
PostPosted: Oct Tue 23, 2018 7:26 am 
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Greetings to David, John and the Forum:

David: I have taken your suggestion and annotated my copy of the schematic with 2N3904.

John: Thank you for the link. I would go there as a last resort, but their price is $69 more than I paid for the pair of speakers.

It turns out that I have an ADC equalizer in hand that will do the job. Not only does it have sufficient range, it also has its own microphone, pink noise generator and spectrum analyzer. The equalizer bands are configured as octaves so pink noise is just what is needed. With this box, I can use the curve that I have for the original Bose equalizer as a starting point and then flatten out the response for my particular installation.

It's a very nice unit.... given to me by a friend a long time ago.... but I never had a use for it until now.

I will keep the Forum posted on how things progress. I have several other irons in the fire right now.... I have to finish painting the rack shelves that I have to hold all my gear and the rainy season has closed in here on the Oregon coast. I really can't mount up the gear until I get the painting done. I will be getting the speakers mounted soon, I hope. The room is so cluttered that in order to get clear reflective space, I have to hang the speakers from the ceiling. This is the way they were hung by the previous owner; the Bose nameplate is on upside down.

Thanks again for all the help. This Forum is wonderful!

Regards,

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Jim T.
KB6GM


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 Post subject: Re: A big eye opening defect in Bose 901's!
PostPosted: Oct Wed 24, 2018 1:26 pm 
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Joined: Aug Sat 01, 2009 2:23 pm
Posts: 1655
Jthorusen wrote:
Greetings to David, John and the Forum:

David: I have taken your suggestion and annotated my copy of the schematic with 2N3904.

John: Thank you for the link. I would go there as a last resort, but their price is $69 more than I paid for the pair of speakers.

It turns out that I have an ADC equalizer in hand that will do the job. Not only does it have sufficient range, it also has its own microphone, pink noise generator and spectrum analyzer. The equalizer bands are configured as octaves so pink noise is just what is needed. With this box, I can use the curve that I have for the original Bose equalizer as a starting point and then flatten out the response for my particular installation.

It's a very nice unit.... given to me by a friend a long time ago.... but I never had a use for it until now.

I will keep the Forum posted on how things progress. I have several other irons in the fire right now.... I have to finish painting the rack shelves that I have to hold all my gear and the rainy season has closed in here on the Oregon coast. I really can't mount up the gear until I get the painting done. I will be getting the speakers mounted soon, I hope. The room is so cluttered that in order to get clear reflective space, I have to hang the speakers from the ceiling. This is the way they were hung by the previous owner; the Bose nameplate is on upside down.

Thanks again for all the help. This Forum is wonderful!

Regards,


Jim
One thing you don't want to do is to try to get flat response from these on your RTA measurements. The originals did not have a flat response curve, and I suspect that the configuration of the design with so much of the energy reflected off walls creates a situation where tweaks in the frequency response were required to get the balance to sound "right". If you read Julian Hirsch's original review (you can find it on Google), he goes into the frequency response that he measured quite thoroughly. It's pretty "wavy". I also don't understand why people always hung these speakers near the ceiling. That single forward firing driver is there to create all the stereo localization cues, and that requires that the ears be reasonably on axis with that driver so that the sound from it arrives directly, and substantially ahead of the reflected energy. Hanging them puts that driver way above you and it ends up contributing mostly to the far field response, just like the other 8. Then the speaker ends up sounding like a big blob of sound with no spatial cues at all. At best, the 901 isn't a very good speaker for localizing sounds (by design), but placement is kind of critical to get the best they are capable of.

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John Stone
Antique Radio Club of Illinois


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 Post subject: Re: A big eye opening defect in Bose 901's!
PostPosted: Oct Thu 25, 2018 1:06 am 
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Location: Lincoln City, OR
Greetings to John and the Forum:

Thanks for the input. Unfortunately, the room's layout and content dictate that they be hung from the ceiling.... there is simply no other place to put them. Also unfortunately, I will have to locate one of them at only a foot from the ceiling instead of Bose's recommended 18 inches. Again, no choice.... I would be banging my head on them otherwise. The right channel speaker should be closer to ideal, as the ceiling slopes up to the right. Also, I will have to go with the minimum recommended distance from the wall (12 inches) instead of the optimum 18 inches. The physical layout of the place requires this placement.... there is no alternative.

As I recall, the speakers are actually rather forgiving.... the ones that so impressed me back in the late '60's were located in front of a bay window with drapes hung in it... a very poor reflective situation.... and they still sounded great.

My ears are showing age and loud noise roll-off these days, especially my right ear.... so I may end up tailoring the curve for my hearing rather than flat anyway. Two or three dB is difficult for me to detect, even if I am looking for it, so a "wavy" response isn't too much of a concern.

My greatest concern is that time and memory distort past experiences. I have wanted a set of 901's for so long and was so impressed 50 years ago that the real speakers probably won't live up to my expectations. Hopefully, I won't be too disappointed.... but they can't sound any worse than a pair of book shelf speakers from GoodWill! :D

Regards,

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Jim T.
KB6GM


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 Post subject: Re: A big eye opening defect in Bose 901's!
PostPosted: Oct Thu 25, 2018 7:52 am 
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Location: Fernandina Beach, FL
Jthorusen wrote:
Greetings to John and the Forum:
Thanks for the input...
My greatest concern is that time and memory distort past experiences. I have wanted a set of 901's for so long and was so impressed 50 years ago that the real speakers probably won't live up to my expectations. Hopefully, I won't be too disappointed.... but they can't sound any worse than a pair of book shelf speakers from GoodWill! :D

Regards,

I can identify with that. Growing up and as a teenager, I got a pair of HH Scott S-10 speakers. I thought that they were wonderful. Then, I upgraded to a pair of Wharfedale W70D speakers. They were tops to me!

But a few years ago, a buddy rescued a pair of JBL L100 speakers that a friend was sending to a thrift shop, free to me!! Now, my previous memories of Scott and Wharfedale have no resemblance to reality!

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 Post subject: Re: A big eye opening defect in Bose 901's!
PostPosted: Oct Thu 25, 2018 12:59 pm 
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Joined: Aug Sat 01, 2009 2:23 pm
Posts: 1655
Jthorusen wrote:
Greetings to John and the Forum:

Thanks for the input. Unfortunately, the room's layout and content dictate that they be hung from the ceiling.... there is simply no other place to put them. Also unfortunately, I will have to locate one of them at only a foot from the ceiling instead of Bose's recommended 18 inches. Again, no choice.... I would be banging my head on them otherwise. The right channel speaker should be closer to ideal, as the ceiling slopes up to the right. Also, I will have to go with the minimum recommended distance from the wall (12 inches) instead of the optimum 18 inches. The physical layout of the place requires this placement.... there is no alternative.



Can you put some downward tilt at the front into them? At least that will get you more on axis to the front driver.

Jthorusen wrote:
My ears are showing age and loud noise roll-off these days, especially my right ear.... so I may end up tailoring the curve for my hearing rather than flat anyway. Two or three dB is difficult for me to detect, even if I am looking for it, so a "wavy" response isn't too much of a concern.


Just start off with the recommended eq curve, and tweak it from there to your liking. Just don't overdo it. Remember that Bose is already stretching those drivers with substantial eq., needed, just to get them to produce close to a linear output.

Jthorusen wrote:
My greatest concern is that time and memory distort past experiences. I have wanted a set of 901's for so long and was so impressed 50 years ago that the real speakers probably won't live up to my expectations. Hopefully, I won't be too disappointed.... but they can't sound any worse than a pair of book shelf speakers from GoodWill!


I know where you're coming from. Probably my most memorable audio experiences were hearing a pair of Stax headphones and a pair of original Quad electrostatic speakers for the first time in the early '70s. I was simply blown away by the clarity of these transducers. Nothing else I heard even came close. I still have the Stax phones and have recently heard the Quads at a friend's place. Both still sound "good". But the "blow me away" factor is long gone, probably due in part to diminished hearing and to the fact that I've heard so many different speakers and headphones in the intervening years that do sound considerably better. Time marches on and technology continues to advance...albeit rather slowly with loudspeakers.

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John Stone
Antique Radio Club of Illinois


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 Post subject: Re: A big eye opening defect in Bose 901's!
PostPosted: Oct Thu 25, 2018 11:38 pm 
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Posts: 484
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Don Cavey wrote:
Jthorusen wrote:
Greetings to John and the Forum:
Thanks for the input...
My greatest concern is that time and memory distort past experiences. I have wanted a set of 901's for so long and was so impressed 50 years ago that the real speakers probably won't live up to my expectations. Hopefully, I won't be too disappointed.... but they can't sound any worse than a pair of book shelf speakers from GoodWill! :D

Regards,

I can identify with that. Growing up and as a teenager, I got a pair of HH Scott S-10 speakers. I thought that they were wonderful. Then, I upgraded to a pair of Wharfedale W70D speakers. They were tops to me!

But a few years ago, a buddy rescued a pair of JBL L100 speakers that a friend was sending to a thrift shop, free to me!! Now, my previous memories of Scott and Wharfedale have no resemblance to reality!


L100s do a good job of the West Coast sound. They have many fans as well as purists who are not fans of them.

I like them for 70's and 80's hard rock vinyl.


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