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TW Acustic three motor unit

Since two weeks I have on loan three motor pad from my friends Black Night turntable. Today I have to return it and just switched back to my stock single motor.

When I first runned three motor pad I felt advantages and disadvantages of this unit. The sound become better but not in each aspect.

With three motor pad the bas was deeper and better separated. The attack of large drums in final of Mahler first symphony was simply spectacular. Three motor unit rocks on complex passages. Overal the sound become more dense, better separated and defined but there is a big but...
With three motor pad the airness and openess of the sound decreased and some "music flow" has gone.
The sound become more audiophile correct but a bit less musical at the same time.

Can you share your experience with AC1 vs. AC3 vs. BN motor?
Does anybody preffered AC1 instead BN motor?

I am puzzled.
milimetr
milimetr OP
126 posts
 
I suppouse that belt tension with one motor is smaller than with three motors. The belt tension with three motors is greater, simply because geometry of three motors around the table. It can be changed to greater tension but not to smaller tension.
So when we compare AC1 vs. AC3 the change in belt tension is inherent with this experiment.
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tdaudio
201 posts
 
Milimetr, Two things here. One how much the belt is stretched and two how much horizontal force the belt puts on the platter. Too much horizontal force hurts the sound.

With a one motor AC these both change together as you move the motor farther from the platter. It is straight forward in finding the sweet spot of enough.

With three motors the belt has to stretch around the motors and the platter. With in reason I don't know if some extra belt stretching is an issue on its own or not but I would not want to go too far. But if the over all set up places too much horizontal force on the platter I think that would be a bad thing.
milimetr OP
126 posts
 
Thanks for clarification. However with AC-3 setup I have a motors as close to the plinch as possible to avoid touching motors to the plinth. So cannot reduce belt tension further using this given belt length.
downunder
1,328 posts
 
Milimetr

The belt is a different length for the ac1 and ac3. Sometimes I swap to 1 motor and change the belt.

You do have separate belts?
milimetr OP
126 posts
 
Downunder. I was always told taht for AC1 and AC3 the belt is the same, however with AC1 we are positioning the motor far apart from plinth and for AC3 as close the plinth as possible, but still can use the same belt.

I have such setup at the moment and the belt is already a bit slippery at running with 20kg BN platter.
Of course we can use the longest belt from BN with AC3, but it is not a default solution. In such setup motors needs to be spaced apart from plinth and the belt would be even more slippery due to less contact area with platter.

According to TW web site, they offers four different belts lengths: 860 mm, 925 mm, 1050 mm and 1360 mm.

1. The belt 860 mm is for Raven GT only where motor pulley is very close to the platter,

2. 925 mm was for old and discontinued Raven One. This belt can be used also with AC1 with motos almost touching the plinth,

3. 1050 mm is default belt for AC1 and AC3 (this is my understanding).

4. 1360 mm is default BN belt. Can be used with AC3 but you need much more space on rack to place motor further apart from plint. I am affraid that this belt would be to slippery witn BN platter I have.
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