Used the T14/1 in a Siemens SM204 rebuild with self Bias. No Bass problems at all. The Haufe has maybe a Problem with higher Levels, because its a small Transformer and you have more distortion with high level Signals. Someone like this more (me to). Ck12 Capsules are strong in low frequenzy Response, with a ami or cinemag Transformer (they have extended Bass response) you have a more hifi sounding mic with heavy bass and highs but less mid response. Is my personal view.
The tube also have an deep impact to the sound, for me no other tube sound so great in a C12 or SM204 circuit than a good GE 6072 Five Star Tube. I’ve tested many other 12ay7 Tubes and only the GE works as expected. A good one is rare to find in these Days. The Capsule in my Build is a Haun CK12.
So the Haufe is a good Transformer. A to bassy microphone can make many problems.