OK. So I mono mixed (-3dB) the PCM kindly supplied by THX. I used an Apogee DAC to sample into both the MPC and SP. The 138 bpm version is the OG. 87 bpm is the lowest the SP goes so I used that as a marker and then did the same for the MPC. I recorded both using an Apogee ADC at 24-Bit 44.1kHz. I normalised all files to -3dBFS and ran analysis tools which I then captured as images for the purposes of this comparison.
I will comment when others have made their observations.
Any questions, feel free to ask. Hopefully this will help dispel some myths about these splendid samplers.
Amen Break MPC3000 138 bpmAmen Break MPC3000 138 bpm Spectrum

Amen Break MPC 3000 138 3D Freq Analysis
Amen Break MPC3000 87 bpmAmen Break MPC3000 87 bpm Spectrum

Amen Break MPC3000 87 bpm 3D Freq Analysis
Amen Break SP1200 138 bpmAmen Break SP1200 138 bpm Spectrum

Amen Break SP1200 138 bpm 3D Freq Analysis
Amen Break SP1200 87 bpmAmen Break SP1200 87 bpm Spectrum

Amen Break SP1200 87 bpm 3D Freq Analysis

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