Around 2003, Bose made a bass module that had 3 downward firing 6 inch woofers that sit about 3/4 inch above the floor. The back of the woofers travel through what some claim to be a 7th order bandpass cavity.
You can see a picture of it here:
bose acoustimass 10 inside - Google Search
This "bass module" is similar in nature to Nelson's slot loaded open baffle woofer - the slot being the floor that the woofers fire against and the back side of the woofers controlled by the length of the port. Helps solve some of those pesky phase cancelations a completely open baffle might create.
If you are handy with wood or mdf - might try something like this. We have tried a few different sub woofers along the way since I bought this 2003 but always come back to it. In a do it yourself solution you would need to have an amplifier that can do 100 watts or so. The drivers are nothing fancy.
If not: You can find them on ebay. They were part of a 5 cube system. Those are great paper weights. You can bridge them to your high level speaker outputs with no ill effect to the amplifier at all. I don't know what magic Bose used with their amplifier but it tracks really well when you use the high level input with even the lowest volume levels: which at my house is good as most of our listening is done at low volume.
Nelson has on one of his sites this article he authored:
http://www.firstwatt.com/pdf/art_slob.pdf
Tim
You can see a picture of it here:
bose acoustimass 10 inside - Google Search
This "bass module" is similar in nature to Nelson's slot loaded open baffle woofer - the slot being the floor that the woofers fire against and the back side of the woofers controlled by the length of the port. Helps solve some of those pesky phase cancelations a completely open baffle might create.
If you are handy with wood or mdf - might try something like this. We have tried a few different sub woofers along the way since I bought this 2003 but always come back to it. In a do it yourself solution you would need to have an amplifier that can do 100 watts or so. The drivers are nothing fancy.
If not: You can find them on ebay. They were part of a 5 cube system. Those are great paper weights. You can bridge them to your high level speaker outputs with no ill effect to the amplifier at all. I don't know what magic Bose used with their amplifier but it tracks really well when you use the high level input with even the lowest volume levels: which at my house is good as most of our listening is done at low volume.
Nelson has on one of his sites this article he authored:
http://www.firstwatt.com/pdf/art_slob.pdf
Tim
My understanding of the condition for any cancellation of any harmonic to occur, the differential signal needs to be fed to a differential transistor pair input, that will cancel the common mode distortion at its common output point; this common output point will feed this signal to the output stage.
With ACA used in "differential mode", there is no such thing as the common output point of an input differential transistor pair. The differential signal is fed to two identical amplifier halves, there is no cancellation of any distortion/harmonics....
Maybe I am missing something here.... in which case I do apologize.
Nick
If the amplifier is fed with a balanced source. The two wires from that balanced source are phase inverted. Not identical.
If fed with an unbalanced source and using the resistor from the other channel. That input signal is phase inverted with respect to the opposite channel.
In that configuration you use the two positive posts to drive the load.
There is a really significant drop in 2nd harmonic when used in that configuration.
If you take the diagram and draw the signal path out - it will make sense. Kind of like the cap snaffler from the '70s. it really really works!
----
If fed with an unbalanced source and using the resistor from the other channel. That input signal is phase inverted with respect to the opposite channel.
In that configuration you use the two positive posts to drive the load.
There is a really significant drop in 2nd harmonic when used in that configuration.
If you take the diagram and draw the signal path out - it will make sense. Kind of like the cap snaffler from the '70s. it really really works!
----
No need, When I read that it made me draw myself a picture, just to make
sure that Oldtimer's disease hadn't caught up with me.
If the 2nd peaks positively on a positive fundamental peak, then it will
do the same on the negative peak, and this is also true of the inverted
signal on the other side.
If you draw a picture of a sine wave and then it's opposite polarity sine
wave, and then you draw the 2nd harmonic for each, you see that the
harmonics are the same phase, and so they cancel.
Today we hit a great milestone - all ACA V1.6 "batch 1" parts kits have completed assembly and late next week will be slowly making their way to our logistics partner but won't start shipping for several weeks as there is a lot of organisation to be done on the shipping side. Remaining power supplies should be arriving next week and everything is on target to meet our shipping target for batch 1 of July 31st. Please don't expect anything to ship before this date, and if it does consider that a bonus 
As a result, we are today announcing batch 2 to try and meet the demand of those who missed out on batch 1, with a shipping target of September 15th. Batch 2 will be conducted in the same way as batch 1. In order to meet this target we are keeping, and get in before Hifi2000's summer holidays in August, this pre-order period "short and sweet". It's open for 48 hours starting 7th July 6PM PST, and ending 9th July 6PM PST (or sooner if sold out). Good luck
As a result, we are today announcing batch 2 to try and meet the demand of those who missed out on batch 1, with a shipping target of September 15th. Batch 2 will be conducted in the same way as batch 1. In order to meet this target we are keeping, and get in before Hifi2000's summer holidays in August, this pre-order period "short and sweet". It's open for 48 hours starting 7th July 6PM PST, and ending 9th July 6PM PST (or sooner if sold out). Good luck
Heck yeah. I was likewise impressed with mine when it arrived last week. The finish is superb; I'm certain the fit will be, too. This is my first adventure outside of the vacuum state realm, so I'm understandably excited. If this goes well my plan is to scratch build two more as monoblocks using the "1.1" boards and parts kits from BA 2017.
Glad to see the "Batch 2" kits have become available - grab 'em while you can!
Hmm... Is this what Zen Mod means by referring to us as "Greedy boyz"?
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