There are 12 springs in the MicMix MasterRoom XL-305 and my clone.
These are the target values for the spring delay timings:

Shown below are the actual measured delay and approximate length of the spring at rest.
For springs which are coupled in the middle (>18ms) there are two measurements and a total. The portion of the spring in the middle which is not coiled is not included in measurement. The coupler on these springs is randomly offset from the middle based solely on superstition. The total length of the coiled section is what matters.
T1 13.52 ms 3.54" (counted 254 turns)
T2 14.72 ms 3.86"
T3 16.16 ms 4.23"
T4 17.76 ms 4.64"
T5 19.48 ms 5.16" (2.52+2.64)
T6 21.36 ms 5.60" (2.75+2.85)
T7 23.40 ms 6.06" (2.97+3.09)
T8 25.60 ms 6.77" (3.22+3.55)
T9 28.10 ms 7.21" (3.38+3.83)
T10 30.80 ms 8.27" (4.10+4.17)
T11 33.70 ms 8.96" (4.31+4.65)
T12 37.00 ms 9.84" (4.87+4.97)
The odd numbered lines are assigned to the Left channel.
The longest line, T12, was also cut, IIRC the delay for an Accutronics" "Long" spring is 37.40 ms.
To avoid an early onset of insanity I only turn-counted the first line after measurement.
For the remaining lines I estimated the length and rough cut them a few turns long one at a time.
I then measured each line using my home-brew TDR and cut the final length using 53 µs per turn as an estimate.
I took the average of each line's final ms/inch and it averages out to 3.8 ms per inch.
254 turns is 3.54" long which works out to be 71.75 turns: The tooling is undoubtedly 72 turns per inch.
3.8 ms/72 turns is 52.78 µs per turn.
If you do this at home remember the following:
When cutting springs remember that they're stainless steel and very hard.
Wear eye protection and use the same pair of diagonal pliers that you'd use to cut guitar strings.
They will destroy good cutters.
Be very careful when forming the hook that you don't stick the sharp end of the uncut spring into your finger.
MasterRoom XL-305 Clone Sound Files: https://proaudiodesignforum.com/content ... Stereo.mp3
(Dry test tracks courtesy of THAT Corporation.)
Link to Accutronics/Accu-Bell Sound Inc. website: http://www.accutronicsreverb.com/
I think four of the 9AB3C1B could be used: https://shop.ehx.com/item/9ab3c1b/parts ... anks-long/
The only question I have is that if one buys 4 are there enough long springs...