I measured the frequency response of the mic available in the HD500 and attached a PDF of the results here. I also have all the data in an excel file here. I used the Class A-15 adjusted for flat frequency response and the 1x12 Blackface 'Lux cab. You can clearly see the extended low frequency response of the ribbon mics and the hi-mid enhancement of the 57. I'll be using these results to measure what the can DEP parameters are doing but thought I'd share my data here in case anyone wants it.
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Sorry, the PDF file didn't show up so I attached it again.
Mic Frequency Response.pdf