Bose 901 IV serie

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bigben22

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Joined 2009
Hi everyone,

I have a question concerning Bose 901 speakers...


I was given a pair by my oncle with the Bose equilizer....

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The problem is that I need to rewire each box...

So I found a wiring diagram...

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but when I opened the box...the driver's looked to be wired all in SERIE???
So What to I do?? follow the diagram (seems pretty complicated)?? or connect them all in a serie??

thanks for your help!!!


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Cal Weldon

Cal Weldon

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Joined 2004
calweldonconsulting.ca
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OK, looks like you have the right EQ and yes those drivers are to be wired in series.

By restoring, you are talking about the cabinets?

Make sure the driver surrounds are still good, I believe those have foam surrounds. Check them by running your fingers around them and pushing in on the foam. If they are weak, you will know it right away, they will fail. You can get surround kits from various places if need be. Quite a job doing 18 of them though.
 
9

901Fixer

Member
Joined 2008
The 901 enclosures you have are the series IV but the drivers are from the V or VI and have to be wired in series for a net of just under 8ohms.

Placement of these speakers is crucial to them sounding tolerable. They have to be at least 48" apart from each other, at least 18" away from side walls, floor and ceiling, at least 8" away from wall behind them and not equal distance from floor to ceiling. If they are out in the open you lose the reflected sound. Also the reflective surfaces, behind and to the side, must be hard surfaces that will reflect sound, no drapes or capet. Check out the Bose website for a diagram.
 
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art64

Member
Joined 2009
They're in series-parallel combo to keep the impedance close to 8 ohms. Looking at the schematic, it has a total of 9 speakers. 3 of them needs to be wired in series. So each row of 3 speakers will have 24 ohms. We have 3 rows of speakers connected in series and each row will have 24 ohms. Now each row needs to be connected in parallel to get the final 8 ohms impedance. Speakers connected in series will add up the resistance of the speakers. Connect them in parallel and it will divide the resistance.
So we have 3 24-ohm rows of speakers connected in parallel will result in 8ohms. 24 divided by 3.

I have 901's too. I modded them. Took the back cover off, turned them around and made them direct firing speakers. Sounded great. Great mid and highs. I have them mounted on the wall with the 16 drivers facing forward.
I also added a Klipsch 10 inch powered sub. Using a Denon AVR-2600 in Matrix Mode, plus I also added BBE 362 Sonic Maximizer. Awesome big surrounding sound. Recommend using good quality heavy gauge speaker wires. I'll probably buy another set (used) for a total of 4 speakers. It sounds big and engulfing.
 
9

901Fixer

Member
Joined 2008
Sorry I didn't follow up with this post. I was incorrect in thinking your drivers were series V or VI as the 1ohm with 3 screw mounting were in earlier versions too. The first 901 series used drivers that were 8ohm/4 screw mounting with cloth surrounds. They were all wood enclosures, yours have the plastic main body which is supposed to be designed better.

There is a mod online that uses the older style drivers in the new style enclosure. It then tells you to put the discarded new style drivers in the old style enclosure, if you have it, and sell it on eBay to recoup some of your mod cost. I thought maybe you had gotten one of those.

The 3 hole drivers are wired in in series, all 9 of them.
The 4 hole drivers are wired as described above series/parallel.

I'm in the process of building stands with woofers in them for my 901/VI to relive them of that duty with much needed bass support. I haven't tried turning them around yet but have heard in mentioned once or twice. Kinda defeats the reflection function but you never know, sometimes things work alot better in ways they were never designed to.
 
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art64

Member
Joined 2009
Even when turned around it still reflects the sound due to the arrangement of the drivers and the enclosure. I mounted my Series V on CRT TV wall mounts. They can be adjusted horizontally and can be tilted up or down. I can adjust the position to where the sound can bounce against the wall or position them away from the wall to minimize the reflected sound. Each of these positions produces different sound qualities. If the pedestal is gonna be used it will sound different specially if you have carpeted floors. I need to upgrade my subwoofer to 15 inch. The Bose has a lot of mid and high range. Need more mid bass. I got plenty of low bass 100hz and below.
 
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art64

Member
Joined 2009
Finished my project. I was able to buy a used bass guitar cabinet with 2 15 inch woofers for $49.99. These woofers have no crossovers. Rewired them for stereo. Using bi-amp one to drive the 901's for high freq and one amp to drive the woofers. The sound is freakin awesome. The bass is tight and natural and the highs blend well. Now, I have to sell my Klipsch subwoofer. No need for it. My amps: Denon AVR-2600 driving the 901's; Yamaha C-80 and M-80 driving the 2 15 inch woofers. Don't have to play it loud to get good tones. Also using heavy gauge Monster speaker wires. Forgot to mention BBE Sound Maximizer for clearer sound and tight bass. The 901's array set up is really paying off. I have a small room 15x15 and the sound is well dispersed. 901's also add mid highs. The woofers's preamp's treble control is set at minimum. No passive crossover on the 15 inchers.
 
9

901Fixer

Member
Joined 2008
So no crossovers at all? The 901's are playing full range and so are the 15" woofers?
I've tried to find a frequency response/impedence curve for my 901's so I might have a better idea where they start to fail and where to crossover to a woofer or tweeter. Right now I have mine running full range and I'm experimenting with where to actively cross the Selenium 15PW3. It sounds good up to 250hz depending on music but I think the 901's extend down into that frequency well so there is some beaming. NickelBack has the nastiest muddy bass I've ever heard.
 
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art64

Member
Joined 2009
No passive crossover on the 15 inchers. Connected directly to the Yamaha power amp. I just turned the treble control to minimum to filter out the high frequencies from coming out of the woofers. The 901 produces these frequencies a lot better and efficiently.

The 901's have an active equalizer which cuts down some of the mid frequencies and boosts bass and treble. When using the active eq with a regular speaker system, you'll notice an over boost of high frequency, attenuation of the mid and bass just about the same. I have the bass of the amp driving the 901's at 1/4 setting from min. Much cleaner overall system sound.
The 15 inchers are already producing the mid bass and some of the mid frequencies.

Are your 901s' not using the active equalizer? It'll sound terrible without the active eq. The 901 by itself is all mid range!!
 
9

901Fixer

Member
Joined 2008
I have, but am not using, the active EQ. I am powering them with a Sony reciever at the moment so using the EQ is not the easiest thing to do unless I use the Tape in/out/monitor set up. Do the 901's need the EQ if they are used with a woofer and tweeter? I've always considered the 901's to be just a mid or rather a full ranger as they are weak on the bass and treble but nice in the midrange.
 
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art64

Member
Joined 2009
I see what you mean. It's a pain sometimes to connect the active eq to a receiver. I have a Denon AVR powering the 901's. But temporarily, I disconnected my dvd/cd player from the reciever and connected the 901's active eq between the dvd player and the reciever. The sound is much different with the eq. The mid frequencies are attenuated and the highs are boosted.

The 901 enclosures have too much mid range. Unless you have a parametric tone control on your reciever, it's almost impossible to control it. So you'll gonna end up boosting your highs and bass to catch up with the 901's mid.

When you connect the active eq, make sure you disconnect your tweeters or they may fry. The active eq is required to make the 901 sound good or normal. Otherwise it's purely mid. It will make music sound muddy. Try connecting it and hear the difference.
 
boywonder

boywonder

Member
Joined 2008
I presently have a pair of 901 series VI that I've had for about 8 years and I used to have a pair of series IV's. Either series, without the EQ connected, sounds worse than am radio. You can connect the eq in a tape loop or if you have separates, between the pre and power amp, or, as mentioned, between your source and the amp.

My present setup is in a large, vaulted-ceiling room with hardwood floors, a very "live" room, and interestingly enough, they produce huge (and amazingly low for 18 little drivers) bass in the bathroom at the top of the stairs leading from this room. The bathroom is quite far removed from the speakers and the effect is quite bizarre.
 
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art64

Member
Joined 2009
boywonder said:
I presently have a pair of 901 series VI that I've had for about 8 years and I used to have a pair of series IV's. Either series, without the EQ connected, sounds worse than am radio. You can connect the eq in a tape loop or if you have separates, between the pre and power amp, or, as mentioned, between your source and the amp.

My present setup is in a large, vaulted-ceiling room with hardwood floors, a very "live" room, and interestingly enough, they produce huge (and amazingly low for 18 little drivers) bass in the bathroom at the top of the stairs leading from this room. The bathroom is quite far removed from the speakers and the effect is quite bizarre.
Click to expand...

This is probably one of the pitfalls of 901 is the environment where the speakers will be used. A lively room will most likely produce better sound cause the room will reflect more sound and this is what the 901 is designed for. Even when the speakers are turned around, they still reflect a lot of sound off the side walls due to its wide array design, filling up the room with music quite nicely. I've seen 901's placed next to entertainment centers like regular speakers. They sounded awful this way.
 
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