Highest fidelity, highest detail EMG45 sized pickups. Suggestions please...

[fast slapper]

Dingstrand Nordwall 6
Always curious about these. Multi-coil design.

MTD Barts sound like they have a higher than usual resonant frequency.

No specs on these either but they use very little wire and claim wide frequency response.
Aluma Bass Bar 4.5 - for 5 or 6 String Basses

 

[winegamd]

This page talks about some ways to measure pickup response. BuildYourGuitar.com :: The Secrets of Electric Guitar Pickups

 

[A9X]

Dingstrand Nordwall 6
Always curious about these. Multi-coil design.

I wasn't aware of that, thanks.

No specs on these either but they use very little wire and claim wide frequency response.
Aluma Bass Bar 4.5 - for 5 or 6 String Basses

But they use a transformer as part of the design as well to get the signal levels up and compensate for the small number of primary turns.

 

[mikezimmerman]

Dingstrand Nordwall 6
Always curious about these. Multi-coil design.

To clarify, they are split-coil, not "multi-coil" in the sense that, say, Wal pickups are.

MTD Barts sound like they have a higher than usual resonant frequency.

The original MTD Barts were lower-impedence active pickups with a built-in preamp for a very wide frequency response. I believe the newer ones are still low-impedence (and lower output) but use an external buffer preamp to boost the output.