Re: Bose 901 drivers
Interesting. When did Bose switch to a more conventional motor? The only 901 drivers I have come across were 1 ohm, all wired in series.
EDIT: I am wondering if those drivers are from the 800 series, the ones used for small PA duty. IIRC those were 8 ohms and the boxes were very similar to the 901's
TICUL38 said:
Interesting. When did Bose switch to a more conventional motor? The only 901 drivers I have come across were 1 ohm, all wired in series.
EDIT: I am wondering if those drivers are from the 800 series, the ones used for small PA duty. IIRC those were 8 ohms and the boxes were very similar to the 901's
7 Ohms it is
The pair of 901-II that I took apart are S/N 166414 (M.O. 2287) & 166510 (M.O. 2288).
The 7 ohm drivers were wired three parralleled series strings of three. I recall someone suggesting 1 ohm drivers...possibly adavancing a rumour without first checking.
The parameters mentioned earlier are per driver. I never bothered measuring the speaker's frequency/impedance signatures because that would not have been productive for me after the "disapointing" listening tests.
P.S. I dont recall "bashing" Bose in my first post, so please dont read into any post what's not there.
The pair of 901-II that I took apart are S/N 166414 (M.O. 2287) & 166510 (M.O. 2288).
The 7 ohm drivers were wired three parralleled series strings of three. I recall someone suggesting 1 ohm drivers...possibly adavancing a rumour without first checking.
The parameters mentioned earlier are per driver. I never bothered measuring the speaker's frequency/impedance signatures because that would not have been productive for me after the "disapointing" listening tests.
P.S. I dont recall "bashing" Bose in my first post, so please dont read into any post what's not there.
Hi Louis,
If you have a series II then you have 4 bolt hole, cloth surround, blue cone drivers correct?
They were last made in 1976. From then on (series III and up) they used foam surrounds and at one point reduced it to 3 bolt holes. No where can I find any bose 901 driver that is other than 1 ohm. I wonder if your drivers have been renewed. If so they must have used the 800 series drivers.
Cheers.
EDIT:
I think I spoke too soon. I did a little research and found the series I & II drivers were in fact 8 ohms, wired as you have described. Sorry for the diversion. We now return to your regularly scheduled programming.
If you have a series II then you have 4 bolt hole, cloth surround, blue cone drivers correct?
They were last made in 1976. From then on (series III and up) they used foam surrounds and at one point reduced it to 3 bolt holes. No where can I find any bose 901 driver that is other than 1 ohm. I wonder if your drivers have been renewed. If so they must have used the 800 series drivers.
Cheers.
EDIT:
I think I spoke too soon. I did a little research and found the series I & II drivers were in fact 8 ohms, wired as you have described. Sorry for the diversion. We now return to your regularly scheduled programming.INDUCTOR ...you posted:
{{i'm interested in knowing the t/s parameters for one (of those) driver(s) only, and output/impedance in freq. (/graphs), for those people that want to find one to build a similar speaker. Thanks}}
I will go a distance with you on this, with a open baffle frequency/impedance graph for a "single" driver. I am curious though why you wish to duplicate a BOSE 901 design? Dont forget you would have to acquire a series of 18 duplicate drivers (+spares) for a stereo pair. I am all for the "ambiphonic" sound the 901 was designed for, and in fact I am concentrating design time with that approach of music/TV sound reproduction in mind, since IMO it provides the most natural rendition of music/sound in my space. Also, the focused in your face speaker boxes do not fit my listening/viewing room unless I forego peace of mind with my mate!
...and Cal, you posted:
{{If you have a series II then you have 4 bolt hole, cloth surround, blue cone drivers correct?}}
The drivers I have here are the 4-mounting hole vintage, with the Bose name printed on a blue paper cone. In passing, the frame vibrates like hell in vicinity of resonance, so will require damping with some mastic molded into the magnet-frame crease, and possibly onto the frame spiders. I still dont know if I will be passing these drivers onto the obsolete shelf....have to do a trial run somehow. Also, glad to read you cleared up the 1 Ohm dingy...could not imagine a driver manufacturer accepting to give birth to a 1 Ohm "runt"...
{{i'm interested in knowing the t/s parameters for one (of those) driver(s) only, and output/impedance in freq. (/graphs), for those people that want to find one to build a similar speaker. Thanks}}
I will go a distance with you on this, with a open baffle frequency/impedance graph for a "single" driver. I am curious though why you wish to duplicate a BOSE 901 design? Dont forget you would have to acquire a series of 18 duplicate drivers (+spares) for a stereo pair. I am all for the "ambiphonic" sound the 901 was designed for, and in fact I am concentrating design time with that approach of music/TV sound reproduction in mind, since IMO it provides the most natural rendition of music/sound in my space. Also, the focused in your face speaker boxes do not fit my listening/viewing room unless I forego peace of mind with my mate!
...and Cal, you posted:
{{If you have a series II then you have 4 bolt hole, cloth surround, blue cone drivers correct?}}
The drivers I have here are the 4-mounting hole vintage, with the Bose name printed on a blue paper cone. In passing, the frame vibrates like hell in vicinity of resonance, so will require damping with some mastic molded into the magnet-frame crease, and possibly onto the frame spiders. I still dont know if I will be passing these drivers onto the obsolete shelf....have to do a trial run somehow. Also, glad to read you cleared up the 1 Ohm dingy...could not imagine a driver manufacturer accepting to give birth to a 1 Ohm "runt"...
Ticul38
Hi,
Just to make sure you have and/or use the BOSE processor for the boosted limit frequencies with your BOSE speakers (?).
I am not interested in building a copy physically -- that would be interesting but costs (a lot of) money -- but in the process and philosophie behind it's construction and it's quality of sound, and calibration. It's a long process for that speaker to the point where it arrived to the maket and played in discos at a very high SPL.
Hi,
Just to make sure you have and/or use the BOSE processor for the boosted limit frequencies with your BOSE speakers (?).
I am not interested in building a copy physically -- that would be interesting but costs (a lot of) money -- but in the process and philosophie behind it's construction and it's quality of sound, and calibration. It's a long process for that speaker to the point where it arrived to the maket and played in discos at a very high SPL.
Hello Inductor,
Listening test was done without the BOSE Equalizer in play.
My first objective was to get around that "boxy sound" detected in the midrange, which from experience is mostly attributed to "paper cone transparency" to internal reflections escaping and muddying the resolution. I did not want to succumb to my usual enthusiastic way of proceeding with a vintage acquisition...and so decided to research/correct in steps, and then re-evaluate the midrange before checking how the equalizer impacts on sound quality. I kept in mind that driving the cones harder pulls them into a non-linear coil/field region...and that is what this equalizer will likely do. Loudness will bury distortion as the brain wants to shut off the ears. Soooo, I shall correct the cones/surrounds to make them as opake as possible, and then check out the midrange again.
Will report results later. I am currently overwhelmed in putting together a more accurate frequency counter ...need 0.1Hz resolution for more accurate Qe, Qm measurements.
Listening test was done without the BOSE Equalizer in play.
My first objective was to get around that "boxy sound" detected in the midrange, which from experience is mostly attributed to "paper cone transparency" to internal reflections escaping and muddying the resolution. I did not want to succumb to my usual enthusiastic way of proceeding with a vintage acquisition...and so decided to research/correct in steps, and then re-evaluate the midrange before checking how the equalizer impacts on sound quality. I kept in mind that driving the cones harder pulls them into a non-linear coil/field region...and that is what this equalizer will likely do. Loudness will bury distortion as the brain wants to shut off the ears. Soooo, I shall correct the cones/surrounds to make them as opake as possible, and then check out the midrange again.
Will report results later. I am currently overwhelmed in putting together a more accurate frequency counter ...need 0.1Hz resolution for more accurate Qe, Qm measurements.
From what I understand, it can not work without the equalizer. Unless you use another similar equalizer, with stepped bass and treble, or, with passive xovers at the same critical frequencies, or, active amps with stepped curves. Also there is a dip for the ressonance, maybe similar as the one in the open baffle speakers. note I don't know them and I never tested them, just from the papers on the speakers. Also don't get confused, they were the best speakers in "small discos" around, for me, at the time.
this is an old thread but I wanted to bump it to say thanks!
I personally don't care for the 901s... but my father has always loved them, he talked about getting a set all the time and eventually bought a new pair several years ago... he recently lost his job and had to sell almost everything he owns to stay afloat including his 901s.
a member of my car club was cleaning out his garage and had an old set of series IV 901s up for sale for $20. I though it would be a great fathers day gift if I bought them and fixed them up a bit.
Of course upon pulling off the tweed grills the speaker foam was all rotted way.
I was searching for whole replacement drivers when good 'ol diyaudio came up with this thread... I never knew they made repair kits for the foam surrounds
I'm sure the $$ could be better spent building a nicer pair of speakers, but the 901s have some kind of sentimental value for my father so I figured it was worth it.
After fixing the drivers I'll probably sand down and paint the enclosures black and then work out some better looking grill material to replace the 70s tweed.
The speakers did come with the equalizer and it is much needed. If my memory serves you can use the speakers without the equalizer, Bose even sells them separate from the equalizer but they "require" that the equalizer be used at all times with the speakers. They sound like tin-can speakers with out it... but they do have a very warm and inviting (albeit horribly inaccurate) sound when the equalizer is in use.
I personally don't care for the 901s... but my father has always loved them, he talked about getting a set all the time and eventually bought a new pair several years ago... he recently lost his job and had to sell almost everything he owns to stay afloat including his 901s.
a member of my car club was cleaning out his garage and had an old set of series IV 901s up for sale for $20. I though it would be a great fathers day gift if I bought them and fixed them up a bit.
Of course upon pulling off the tweed grills the speaker foam was all rotted way.
I was searching for whole replacement drivers when good 'ol diyaudio came up with this thread... I never knew they made repair kits for the foam surrounds
I'm sure the $$ could be better spent building a nicer pair of speakers, but the 901s have some kind of sentimental value for my father so I figured it was worth it.
After fixing the drivers I'll probably sand down and paint the enclosures black and then work out some better looking grill material to replace the 70s tweed.
The speakers did come with the equalizer and it is much needed. If my memory serves you can use the speakers without the equalizer, Bose even sells them separate from the equalizer but they "require" that the equalizer be used at all times with the speakers. They sound like tin-can speakers with out it... but they do have a very warm and inviting (albeit horribly inaccurate) sound when the equalizer is in use.
This project went the back shelf....but still very "mind" active.
Back in november took many test readings with different cone weighings using 1 to 5 size 3/0 split shots (fishing sinkers)..concluding that weight mods for the 901-2 drivers would not be that beneficial towards designing a compact TL speaker. Also the same weight mods towards recycling these into sealed boxes gave results like:
With 4 lead sinkers (0.72 grams/sinker):
Fs 55 hz (no mods = 78)
Qm 2.76 (2.46)
Qe 0.58 (0.44)
Qt 0.476 (0.372)
Re 7 ohms
Vas 7.9L
L 0.24mH
Best F3 is 89 hz in 4.1L box with heavy fill, no leaks and Qtc 0.7
Without mods best F3 was 166 hz with Vb at 1.8 L (heavy fill, no leaks)
The 901-2 as designed by BOSE simulates as follows using Unibox (freeware):
Vb 20L, heavy fill, no leaks, 9 drivers (3 paralleled series of 3)
F3 164 hz
Fb 154 hz
Qtc 0.661
Max power input 465 watts SPL at 1W/1M 101 dB / 118 dB at 50 Watts
Driver ratings worked out at:
each driver at 30 Watts...music rating =270 Watts / 125 dB at 1 kz/ 116 dB at 100 hz / 90 db at 20 hz.
each at 5.5 Watts for continuous sinewave = 50 watts
All simulations done without the electronic signal booster.
Here are the output graphs using Unibox (excellent software)
Back in november took many test readings with different cone weighings using 1 to 5 size 3/0 split shots (fishing sinkers)..concluding that weight mods for the 901-2 drivers would not be that beneficial towards designing a compact TL speaker. Also the same weight mods towards recycling these into sealed boxes gave results like:
With 4 lead sinkers (0.72 grams/sinker):
Fs 55 hz (no mods = 78)
Qm 2.76 (2.46)
Qe 0.58 (0.44)
Qt 0.476 (0.372)
Re 7 ohms
Vas 7.9L
L 0.24mH
Best F3 is 89 hz in 4.1L box with heavy fill, no leaks and Qtc 0.7
Without mods best F3 was 166 hz with Vb at 1.8 L (heavy fill, no leaks)
The 901-2 as designed by BOSE simulates as follows using Unibox (freeware):
Vb 20L, heavy fill, no leaks, 9 drivers (3 paralleled series of 3)
F3 164 hz
Fb 154 hz
Qtc 0.661
Max power input 465 watts SPL at 1W/1M 101 dB / 118 dB at 50 Watts
Driver ratings worked out at:
each driver at 30 Watts...music rating =270 Watts / 125 dB at 1 kz/ 116 dB at 100 hz / 90 db at 20 hz.
each at 5.5 Watts for continuous sinewave = 50 watts
All simulations done without the electronic signal booster.
Here are the output graphs using Unibox (excellent software)
Has anyone ever found a frequency response graph of any series 901? This has always been a heated discussion point as Bose would never provide one. I have searched some but only found one somebody did outside in a garden so not exactly optimal. I'm curious to know what range they do cover well and where they roll off.
901.Fixer
There is a summary of a frequency response test published in Stereo Review (70's). Testing was performed by the "Hirsch-Houck Laboratories.
I made a 576 kbts pdf copy of the article which I am mailing you...tried to place here but weighs more than the 102.4 Kbts limit imposed here.
Louis
There is a summary of a frequency response test published in Stereo Review (70's). Testing was performed by the "Hirsch-Houck Laboratories.
I made a 576 kbts pdf copy of the article which I am mailing you...tried to place here but weighs more than the 102.4 Kbts limit imposed here.
Louis
this is an old thread but I wanted to bump it to say thanks!
I personally don't care for the 901s... but my father has always loved them, he talked about getting a set all the time and eventually bought a new pair several years ago... he recently lost his job and had to sell almost everything he owns to stay afloat including his 901s.
a member of my car club was cleaning out his garage and had an old set of series IV 901s up for sale for $20. I though it would be a great fathers day gift if I bought them and fixed them up a bit.
Of course upon pulling off the tweed grills the speaker foam was all rotted way.
I was searching for whole replacement drivers when good 'ol diyaudio came up with this thread... I never knew they made repair kits for the foam surrounds
I'm sure the $$ could be better spent building a nicer pair of speakers, but the 901s have some kind of sentimental value for my father so I figured it was worth it.
After fixing the drivers I'll probably sand down and paint the enclosures black and then work out some better looking grill material to replace the 70s tweed.
The speakers did come with the equalizer and it is much needed. If my memory serves you can use the speakers without the equalizer, Bose even sells them separate from the equalizer but they "require" that the equalizer be used at all times with the speakers. They sound like tin-can speakers with out it... but they do have a very warm and inviting (albeit horribly inaccurate) sound when the equalizer is in use.
I still have them since I bought them in 1985 at an AAFES store overseas. Have not used them much over the years except nowadays after I did some mod on them. I removed the restrictive cloth on the back and then turned them backwards. It's still a direct reflecting speaker cause the sound still bounces to the sidewalls. I had to add some bass (low and mid) reinforcement to the system using an old Crate 2 x 15 bass guitar cabinet. The bass is driven by a portable Sony AM/FM/Casette/CD player combo which happens to have a bass boost feature. The bass is sure loud and can be felt. The Sony probably only has 25watts/ ch or less. I'm also using Gemini Active Crossover to filter out the high frequencies from going into the bass cab. Sounds incredible. Sounds BIG. Not just loud but BIG. 901 array is doing a good job filling up the room. Highly recommend mounting the 901's up high on the wall, closer to the ceiling with the front or V point pointing slightly down.
The only drawback with this set up is that the room looks like a club now with those big speakers. I'm also using heavy gauge speaker wires for all speakers. Hope your Dad enjoys them. My dad did not have a chance to hear mine. His time ran out.
Bose 901 Series II
I like what you've done with these. Do they have a sheer/metal grill? I can't tell from the photo/my monitor. I picked up a pair for 50 bucks a few months back. I wanted something that played loud and could hang from the ceiling in my work out room. I tried them in a listening room when I first got them home. They sounded quite a bit less than OK. The amp I had hooked them up too was likely too small. I'm sure part of the problem is age, although the EQ had just been refurbished by the factory a few years back. They were set up per the manual. In the workout room with a 60watt 20 year old integrated amp and the EQ, hanging high and playing loud rock while I work out they ARE PERFECT! I'd have to say they have motivated me to workout more often. They beat the heck out of using mini monitors or headphones. I bought a second pair as I'm planning on stacking them and hooking them up to a serious pro use power (500 - 100watt) amp for the occassional party. I may even hook them up to my alarm system.
I like what you've done with these. Do they have a sheer/metal grill? I can't tell from the photo/my monitor. I picked up a pair for 50 bucks a few months back. I wanted something that played loud and could hang from the ceiling in my work out room. I tried them in a listening room when I first got them home. They sounded quite a bit less than OK. The amp I had hooked them up too was likely too small. I'm sure part of the problem is age, although the EQ had just been refurbished by the factory a few years back. They were set up per the manual. In the workout room with a 60watt 20 year old integrated amp and the EQ, hanging high and playing loud rock while I work out they ARE PERFECT! I'd have to say they have motivated me to workout more often. They beat the heck out of using mini monitors or headphones. I bought a second pair as I'm planning on stacking them and hooking them up to a serious pro use power (500 - 100watt) amp for the occassional party. I may even hook them up to my alarm system.
ART64
I know this is an old thread, but I was just noticing the placement of Art64's 901s and was wondering if you were using the bose equalizer with them too?
Without proper placement and the EQ, you will not get the proper sound or bass from these speakers. They are also power hungry speakers so having an amplifier of 300-500wpc will really make them sing. By looking at your placement, I can see that they are too close to the corner / wall, and the ceiling, and facing the wrong direction. The angled side of the speaker should be facing the wall.
And I know that using them without the EQ you will have minimal to no bass.
I originally had mine set up similar to yours until someone told me about how crucial it is with these speakers to set them up properly. After setting them up the right way, it was a dramatic difference in the sound! It was so much better sounding I couldnt believe my ears!
I know this is an old thread, but I was just noticing the placement of Art64's 901s and was wondering if you were using the bose equalizer with them too?
Without proper placement and the EQ, you will not get the proper sound or bass from these speakers. They are also power hungry speakers so having an amplifier of 300-500wpc will really make them sing. By looking at your placement, I can see that they are too close to the corner / wall, and the ceiling, and facing the wrong direction. The angled side of the speaker should be facing the wall.
And I know that using them without the EQ you will have minimal to no bass.
I originally had mine set up similar to yours until someone told me about how crucial it is with these speakers to set them up properly. After setting them up the right way, it was a dramatic difference in the sound! It was so much better sounding I couldnt believe my ears!
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