Aha! You figured out the frequency thing. Here’s an example of another 1st order high pass. Flipping the bytes around and then dividing by 256 seems to line up perfectly. 004001

Highpass filter 320hz, 6db/oct butterworth:

6770983C000000002DF3A23E5924633F5A13E9BE91765A3F1D74053FEB7DA93E9520633C87EB

7FBF8F2EE3BB6DFE7F3FE107AA3E68385DBFD5D200BFD2F05DBF4F2CFF3E050100004001F304

353F00000000000000000000000000000000000000000000

I like puzzles like this

Ok then, here's another data dump.

Here’s a parametric band. With the HEX flipped around it’s 03F700. Converted to decimal and then divided by 256 = 1015

parametric 1.015Khz bandwidth 1.89 -4db:

ADF6003D0000803FF0474F3EEA88573F0FDB91BD993D743F2D65993E23A4C03E0A999A3E472

B72BF6B28803EBDD9773F0F99C73E3A324FBFE12A16BFA65751BF6159133F0000000000000000

00000102FC00F703F304353F000000000000000000000000

I was coming to similar conclusions. The two ideas I’ve had are either the software is plotting the response of the 3 filters together and then calculating FIR coefficients for that response or… the Analog Devices DSP “book” talks about combining IIR filters (either cascaded or parallel) into one set of coefficients using the Z-Transform. I haven’t yet found a calculator for doing that and I’m not quite to the point where doing it “by hand” would make sense.

I thought the FIR thing was kind of brilliant because it would probably allow the visual plot that is created in the software actually match what the box is really doing and it seemed like a good way to ensure that the latency through the filter was consistent no matter what filters were used. What didn't add up was A) If it was changing the number of taps used depending on the need for better low frequency accuracy, wouldn’t that be changing the latency? B) Can you actually fit enough FIR coefficients to do this into the 68 bytes that are available? C) If I understand correctly, the floating point DSP is probably more advantageous with double precision IIR filters. D) Offering only Butterworth and Bessel filter shapes doesn’t quite line up with FIR filters. Etc etc.

My next step instead was going to be to wrack my brain to find a way that the coefficients for a simple IIR could be sorted out of the string of HEX. Then I would know that it was indeed IIR and also where the coefficients were stored. I’m wondering if the first 8 bytes might somehow represent poles and zeros. I’ve noticed that if the filters are Low Pass or High Shelving then bytes 5-8 are always 0000803F. If the filters are High Pass or Low Shelving then bytes 5-8 are, I think, either 0529643F or 00000000. If the first 8 bytes are defining something like poles and zeros then what's left is 60 bytes for coefficients. Assume 5 coefficients then there are 12 bytes per coefficient.

Low Shelf 3Khz 6db/oct -1db:

9C94BE3D0529643F525A8B3EDA77463F07E216BF420E443F7E9D243FE07AA03E066734BDD1C

27EBF1AFA84BDB5757F3FA785A43E9F2E5FBFB67CFABE44FC5FBF74ECF73E0201FF00B80BF30

4353F00000000000000000000000000000000000000000000

bank 1 = Low shelf 12db/oct 5Khz +1db

bank 2 = Low shelf 12db/oct 500Hz +3db

bank 3 = Hi Pass 6db/oct butterworth 100Hz

CFEF9E3B00000000CA91093D0735AA3FA6E405BE8E867F3F233E793DFC017C3E6A85673F7432

1BBFCD565F3FC43EFA3E8528373F533CBFBEDE906DBF9C1BB5BE08736F3F020201008813F304

353F02020300F401F304353F050100006400F304353F0000

bank 1 = Low shelf 12db/oct 5Khz +1db

bank 2 = Low shelf 12db/oct 500Hz +3db

bank 3 = Low Pass 12db/oct butterworth 1Khz

44865D3CC8DDCA3FF84D033D1167AF3E026B8EBF322A7F3F884BA53DA1CC273E6F033CBE4F

2419BDE764733F89AF9E3EDF614A3FFA7295BADBFDB63B1C7F0E3E5C827D3F020201008813F3

04353F02020300F401F304353F04020000E803F304353F0000

Low Pass 300Hz 12db/oct Butterworth:

21BC543C0000803F465B483E321487BD3A3678BC081B7D3F4C8C193E509FC93E273D75B95322

2F3A68DE963E3BA2743F2C8DCB3E61EE073875C3C73797A54FBFA4BA153F040200002C01F304

353F00000000000000000000000000000000000000000000

Low Pass 300Hz 12db/oct bessel:

9357193C0000803F5C954F3E3D7E3BBDEA3C4ABC37107C3F7BE3323E6C60C83E534578B9C33

C2C3ADAE2933EAF16753F2A0ACB3EAD0507381659C737FFDD4FBF4C6C153F040200002C0100

00003F00000000000000000000000000000000000000000000

Lastly, I’ve found that byte 4 changes it’s frequency split points at different frequencies if the filter is 12db/oct as compared to 6db.