I have one. I even posted a thread about it, see here.

Nowadays I have it at work with my BM4500 setup (BM4500+CD4500+Beovox 3000 flat panels on front, then the amb. unit and CX50s as rear speakers). It does work and sounds good, on certain sources. Depending on the recording there might be sound from the back or very little. As it's not a true surround system one could argue if it sounds realistic or not but it does spread the music nicely all over the room, no need to raise volume. And makes a certain feel of space.

The thing to avoid with amb. setup is a low-bitrate MP3s, the compression causes all sorts of noises on the rear (as it affects the phase).

The rear sound is mono, but you need to have two speakers connected. If you have an extra set of Beovoxs around, it's worth trying how it sounds. The adapter itself can be bought cheaply. I remember seeing at least one on Lifestyle-Av's website.

I have a BM4000 that I use (on ocaasion) with Uniphase fronts and CX100 as sides (rear speakers) so I am familiar with Ambio. I am curious to hear how it  will work accross a range of reciever 2400, 5000, 7700 just to name a few.

I like the wat it works with vinyl LP''s on my BC 7700.

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Is there actually a 'circuit' in this thing? I use to achieve a cool surround effect by connecting two speakers across the positive speaker outputs and having all balance control set to neutral as possible - this mean't only differences in the channels came through the rear (no dialogue or other mono sounds) and the effect could be remarkably good with some sources whether stereo or dolby!!! Of course there was no clever processing or steering etc.. but for what it cost who cares!!

Step1 wrote:

Is there actually a 'circuit' in this thing? I use to achieve a cool surround effect by connecting two speakers across the positive speaker outputs and having all balance control set to neutral as possible - this mean't only differences in the channels came through the rear (no dialogue or other mono sounds) and the effect could be remarkably good with some sources whether stereo or dolby!!! Of course there was no clever processing or steering etc.. but for what it cost who cares!!

I havent looked inside to see but it is my undersanding that it is a handful of resistors and some kind of transformer, although since the unit does not require its own power draw I couldnt see it being much of a transformer.

In the end its a bit of a "gadget". It works and I like it  but it not really all that necessary. The music sounds just as good without it. Works best with vinyl and is at it least with digital type MP3 files.

You should scan your manual and send it in to beoworld! 

They may already have it. If not I would be happy to do that for them.

Step1 wrote:

Is there actually a 'circuit' in this thing? I use to achieve a cool surround effect by connecting two speakers across the positive speaker outputs and having all balance control set to neutral as possible - this mean't only differences in the channels came through the rear (no dialogue or other mono sounds) and the effect could be remarkably good with some sources whether stereo or dolby!!! Of course there was no clever processing or steering etc.. but for what it cost who cares!!

I used to rig that kind of stuff up as a kid (including a series pot to adjust the volume of the "surround" speakers).

I remember very well that it sounded great when you turned the rear speakers on.... and even better some hours later when you turned them off!

I have a couple of these adaptors; I know why I bought the first (simple curiosity) but cannot quite explain why I 'need' two! I agree with the remarks that they work well with some recordings - not so good with 'close-miked' ones IMHO - and also very well with some FM broadcasts. I haven't tried one with DAB; so that's the next experiment!

I conclude that it's the old Haffler technique - the difference signal from the R & L taken from the +ve 'speaker terminals - with some attenuation, and the choice of full-range or limited. My thought is that they work better with vinyl than CD (apparently) because older recordings tended to have fewer channels mixed down (fewer tracks on the recorder!) thus had more 'distance microphones' and thus more room ambience, rather than reverberation added by the producer. I am ready to be corrected by anyone with greater knowledge or understanding!

Usefully, the 'ambio' box allows the effect to be switched on or off without any unplugging of leads. Unfortunately, the leads still have to be there, cluttering up the room - but folk who have embraced 'home cinema' don't seem to mind!

If one has a BeoMaster 4000, it has the 'ambio' built-in, I think using the same circuit.