I am unable to get the required base sound from my Acoustimass 16

The setup is possible, but with several compromises. First off, to use the active equalizer, you'll need to insert this into one of the 2 channel AV channels limiting your listening with the equalizer to stereo only. The acoustimass subwoofer acts a driver/power regulator for the little cube speakers. It probably will not be able to drive the 901s at the correct level when attached to the Acoustimass unit as front left/right speakers. You could try running a dedicated set of speaker leads to the 901s which may work and still allow surround sound, but you'll lose the equalization capability on the 901s.

On my yamaha 375 receiver if I connect digital or hdmi it disables the balance/bass treble etc but they work with anolog don't know if yours might be the same just abit strang if anolog doing it aswell

Very common problem with today's receivers. Receivers made today don't have a true preamp section in the amplifier and do not amplify the sound to the extent of an older receiver. I have large 15" front speakers on my system, and have stuck with my 15 year old receiver just because I know that a new receiver will not have the power to drive them well. Many of the newer receivers need to be turned up to 50-60% before you can even hear anything from the speakers.

I would get a receiver that puts out a little less power than the speakers can handle. This will prevent you from blowing them by sending too much power to them, but will still send enough power to make them sound good.
An example would be, if you're speakers have a combined power of 500 watts get a receiver around 495 watts or a little less.

If you have it literally conencted the way you say not much good will happen.

The speaker OUTPUTs for the Yamaha feed the INPUTS on the Acoustimass Module then the satellites branch out of the Acoustimass Module's OUTPUTs.

Acoustimass module
Bose® recommends putting your Acoustimass module at the same end of the room as the
television monitor. To prevent interference, keep the module at least 2 feet (.6 m) from the
television.
• You may hide the Acoustimass module behind or under furniture, but do not block the
opening. Be sure there is at least 2 inches (5 cm) between the opening and any surface.
• If the opening faces the wall it increases the bass; if it faces away it decreases the bass.
For the most bass response, place the opening 2 to 3 inches (5 to 8 cm) from a wall or
corner.
• Stand the Acoustimass module vertically or horizontally (Figure 6). To stand it on the
cable connection end, remove the cover by gently pulling it away

Move the sub closer to a wall or corner to increase the bass.

This is a SYSTEM and as such is not designed to be pieced out or separated. I don't recommend that you try it that way. I doubt it will improve the sound.

Clarify, did it ever work for you? Were both receivers used properly configured for the subwoofer? Did you also test the other speaker moduels running off the subwooferto see if they work?

Speaker Receiver setting
• Left and right LARGE
• Center LARGE
• Left and right surround LARGE
• Center surround* LARGE
• LFE/Subwoofer ON
With an Acoustimass 16 Series II system or upgraded Acoustimass 15 Series IlI system only.

Under the input menu, there is a volume trim function which allow you to increase or decrease the volume level of each input. It is designed so that the volume of different components can be matched to prevent a blast of sound when changing to a lounder output. You can increase the alevel of the dtv input, and decrease the level of the tuner. Tuner volumes are usually high.

Has it ever worked?

Try this - connect one pair of its speaker wires at a time and test it. Watch the polarity.

• Make sure all cube speaker arrays are connected to the proper terminals according to their
position in your room.
• Check to be sure all wires are connected to your surround receiver with the proper polarity
(+ to + and – to – wires). Incorrect wiring can result in a total loss of module output.
• Correct any wiring problems before you plug in your receiver and turn it on.

How do you know the receiver's Left channel isn't the fault? Sounds like a source issue.

You should try to increase with remote of your yamaha the sound level for sub.In my Pioneer receiver I can increase level from minus 10 to plus 10 DB

There are two reasons for this. Firstly, the commercial channels are deliberately boosting the volume during commercial breaks to grab your attention. Secondly, the commercials use compressed audio (narrow dynamic range). This often comes across much louder than program material, which is using a wider dynamic range on which you would have based your volume setting. It is noticeable that the BBC are also sending out wide variations in volume at present - Yes it is VERY annoying. Some sort of ALC (automatic level control) is required but this would need to be switchable. Hope this helps.