Bose 901 IV serie

[bigben22]

Hi everyone,

I have a question concerning Bose 901 speakers...


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







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

So I found a wiring diagram...





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!!!

[Cal Weldon]

Check the DCR to ensure they are the 1 ohm drivers and wire them as they were. Different series' were wired differently and you can't change that. Also make sure the EQ is designed for either a series 3 or 4. Others will not compensate correctly.

What are you doing with them?

[bigben22]

I checked the drivers... and they are .9ohm in resistance...

the equilizer I got is like that one:
http://cgi.ebay.ca/Vintage-BOSE-901-...1%7C240%3A1318



And I want to restore them so I can listen to them in my basement...

[Cal Weldon]

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.

[901Fixer]

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.

[bigben22]

thanks for your help guys!!

And I checked the foam surrounds and they seems pretty good! I think they where changed...


question for 901Fixer.... How can you tell that my drivers are from the 901 V1 serie???
I tought that they were IV serie...

thanks!

[Cal Weldon]

I am interested too. Those look like lV's to me. Tell us the secret.

[bigben22]

anyone?

[art64]

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.

[901Fixer]

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.