Bose Acoustimass 6 Series II Rebuild/Repurpose

[Trailblazerb]

Help??

Anyone have a schematic for the BOSE Acoustimass 6 Series II? A picture of the guts, maybe one they are willing to blast apart with a sledge hammer so I can see the inside?

I have a BOSE Acoustimass 6 Series II sub (Acoustimass Module) I acquired. I would like to clip out the circuit control board and put a Dayton Audio MCA2250E (2x22W + 50W) 2.1 Channel Class D Plate Amplifier on the back of this thing. There is plenty of room on the back of the BOSE and all I need to do to fit the MCA2250E is to make the cut out a little taller (+3").

I need to know how many speakers are inside this and how they are wired so I can test the ohm rating properly. Are they in a series? Are they in Parallel, is it a mix of both? I don't want to get this hooked up and damage the amp, even though it is only $65 right now.

I can find info on the Acoustimass 5 and others - but there is next to nothing on the 6/II.

I like the form factor of the unit and it will fit nicely under my office desk. I plan on using this with output from my computer to he MCA2250E input. I will use the L/R powered output to run a pair of Dayton Audio 452's I have sitting on my desk.

AK has always been super helpful and I am hoping someone is hiding a service manual in the back of their underwear drawer where no one will find it in their possession and can help me.

AtDhVaAnNkCsE!

TrailblazerB

I hope I don't get totally jacked for posting this ;-)

 

[onwardjames]

Phew, this'll be tough. Bose guards their secrets like no other. Hoping someone can help you out with this. Best of luck.

 

[Trailblazerb]

Here is some photo support..

I took a photo just inside the back of my Bose AC6/II. This is just under the circuit board panel on the back side. To go further would mean disassembling the box and potentially destroying the whole thing (which really would not be a big loss - grin).

Interesting question comes from looking at this... Why does this speaker have two sets of binding poles?

Then doing a google search for the number on the label on the back of the magnet "189824-001" and I can find this image from Vietnam - very likely a pull from someone who DID tear their AC6/II apart to extract the speakers.

This means there might just be two 6" woofers in there.

If this works, it just might make something good from an Acoustimass unit and there are tons of cheap subs out there!

 

[Trailblazerb]

BOSE Acoustimass 6 Series II - More Data.
Testing Leads...
Applying a signal from an amp to the Yellow/Green leads produces decent sound through the visible woofer just inside the access in the back. Identical sound seems to come from doing the same to the Orange/Brown leads on that speaker. Similarly the White/Black and Red/Gray leads yield the same results on the unseen second speaker. Any combination across opposite pins does not yield any sound. ie. Amp + to yellow, amp - to Orange or Brown = no sound.

Polarity Note:
Used the camera on my iPhone to identify polarity stamped on the binding posts boards. Yellow = + and Green = -, Orange = + and Brown = -. So, assuming similar situation on the black connector means that Red and White should be Positive and Black and Gray should be Negative on the second speaker (which cannot be seen).

Is is possible that each sub is pulling a signal from L or R channels to the same coil somehow? ie. Yellow/Green = L channel and Orange/Brown = R channel to the same speaker?? Maybe these have Dual Coils?? Only BOSE may know!

Ohm Meter Reading:
Testing Yellow/Green yields 6 ohms and Orange/Brown yields 7 ohms?!? Seems odd to get two different resistance readings from what may be the same coil (?). I get exactly from the second (black) plug. The White/Black yields 6 ohms and the Red/Gray gives me 7 ohms. And yes, I know that to properly test I should be using a signal generator - but I aint got one - so I am using what I do have on hand. Just need enough information to not blow up a $65 amp

Thanks for looking at this with me.

TrailblazerB

 

[Trailblazerb]

Learning new things today!
What are Dual Voice Coil (DVC) Subwoofers:
Dual voice coil subwoofers are a popular choice among car audio enthusiasts who want more flexibility in wiring their sound systems. While typical subwoofers have a single voice coil, dual voice coil (DVC) subwoofers use two separate voice coils, each with its own connections, mounted on one cylinder, connected to a common cone.
The key difference between single and dual voice coil subwoofers is the multiple wiring options DVC subs offer:

• Parallel: A dual 4-ohm voice coil subwoofer with its coils wired in parallel presents a 2-ohm load to your amplifier. Since an amplifier produces more wattage at a lower impedance, the parallel connection ensures you'll get the most output from your amp. In the same fashion, if you have a stereo amplifier and two DVC subs, wire both subs for 2-ohm impedance (one per channel) for maximum output.

• Series: Series wiring lets you configure multiple woofers to one amplifier at an acceptable impedance. Wire both coils in series for an 8-ohm impedance, and then wire two 8-ohm subs together in parallel for 4-ohm total impedance (perfect for most 2-channel amps bridged to mono operation). Another example: if you have a high-powered 2-channel amplifier, wire four 8-ohm subs per channel (each channel sees a 2-ohm load).

• Independent: You can wire each voice coil to a separate channel of your amplifier, if you prefer not to bridge your amp. Independent wiring is a nice option if you're wiring two DVC subs to a 4-channel amplifier — one voice coil per channel. Just make sure the signal going to each coil is exactly the same, or the differences will cause distortion.

 

[Alan J]

I've been digging into one of these as well. As indicated by Trailblazerb, there are two dual voice coil drivers. There are multiple crossovers, possibly sending bass from LF, RF, LS, RS to the four coils and leaving the Center out of the equation (I didn't trace it or check continuity through the low pass network). The thing actually sounds serviceable in a smallish room home theater setup driven by two channels of an old JVC receiver.

This project video at Parts Express - http://projectgallery.parts-express.com/speaker-projects/diy-bose-acoustimass-6-rebuild-repurpose/ - provides the voice coil polarities. He substituted a small Class D 2.1 plate amp for the passive network, providing an OK subwoofer and amps for small speakers for a desktop/office setup. He characterizes it as a decent $100 subwoofer. He wired all four in parallel, which by my measurements as well as TralblazerB's would yield under 2 ohms, so I would tend to go with series-parallel (each driver's two voice coils in series, then the two drivers in parallel).

Question for anyone with an opinion... Would you...

1. Look for a cheap ~100W plate amp
   
2. Add a 2.1 channel plate amp as in the PE project and for a similar purpose (I could probably use such a thing in the office).
3. Throw it away and save the $75 this would end up costing for other things, despite the potential satisfaction of repurposing