Quite a complex topic. Have you ever built a transformer, or perhaps designed an amp that includes a transformer in the audio path?
Sorry can't help you with that request, but if you are looking for a source to purchase, Crites has a model made by Universal Transformers to his specifications, the model 3636 with -1 to -12 dB in 1 dB steps. ~ $38.00 USD each + $ 15.00 shipping for a pair.
Autotransformers | Critesspeakers.com
https://critesspeakers.com/3636atz.pdf
output-trans-speaker-matching
You can check Turner's windings with spreadsheet below.
Practical Transformer Winding
You can check Turner's windings with spreadsheet below.
Practical Transformer Winding