Trying to bring some science into my DIY embossing mess (Calibration Tool WIP)

[fanelx]

Hey trolls,

So instead of randomly tweaking angle / pressure / springs / vibes / magic and hoping for the best, I started writing a small Python tool to actually measure what my embossing head is doing.

Current setup:
DIY embossing head, cutting polycarbonate (CDs). Yes, I know. Don’t judge me.

What I’m building:

• Generates a structured test suite (log sweeps, multitone, tones, silence)
  
  I emboss that to disc
  
  Playback gets recorded
  
  Software analyzes:
  
  Frequency response via deconvolution
  
  Resonances
  
  Level-dependent non-linearity
  
  Basic wow estimation
  
  Noise floor
  
  Then it builds a pre-compensation curve based on what the system actually does

Important:
This is not “let’s EQ our way out of bad mechanics.”

The whole point is:

• Measure the real mechanical behavior
  
  Fix what can be fixed physically (angle, mass, damping, downforce)
  
  Only then apply pre-emphasis where it makes sense

Everything is offline measurement (emboss → playback → analyze). I’m not trying to read while cutting because that just turns into structural vibration soup.

I’m refining the measurement side now:

• Sweep deconvolution
  
  Multi-level comparison to detect non-linearity
  
  Automatic resonance detection
  
  Repeatable calibration presets

I’ll upload the tool here soon so other trolls can try it on their own questionable contraptions and tell me where it breaks.

The long-term goal is to make something genuinely useful — not just for me, but potentially a semi-professional calibration workflow for DIY heads.

If anyone here has:

• Experience measuring cutterhead response
  
  Data on typical resonance zones in lightweight builds
  
  Opinions on damping strategies
  
  Or just wants to tell me I’m overengineering this…

I’m all ears.

More soon.

[leemichael]

Cool project!

One important thing to flag though:

Right now your measurement chain includes the playback system, which means you’re not just measuring the head — you’re measuring:

cutterhead × disc × cartridge × stylus × phono stage

Cartridges and styli can easily introduce large FR deviations, resonances, tracing distortion, and crosstalk differences, and phono stages often aren’t perfectly RIAA-accurate. Without characterizing that chain first, your compensation curves risk correcting playback errors instead of cutterhead behavior.

There’s actually already a dedicated cartridge-measurement script floating around (ASR forum) that uses calibrated test records to generate response profiles. Running your playback setup through something like that first would give you a reference correction curve.

https://www.audiosciencereview.com/forum/index.php?threads/phono-cartridge-response-measurement-script.41148/

If you ever expand this tool, an essential feature would be:

User playback calibration profiles → automatic flattening of measurements within your software.

That would make results comparable between users and turn your software from a clever analyzer into a genuinely reliable measurement platform.

[markrob]

Hi,

I'm in the process of finishing up the design and debug of an eddy current sensor system to allow bench testing of cutter head response without the need to do the cut -> capture -> analyze workflow. It's not an end all as it does not take into account the changes to the head response when interacting with the cutting medium, but it can allow you to spot issues and correct them on the bench. If there is interest, I can post more construction details. Below are a couple of shots of the setup with a rocker style head I'm working on in the test fixture. If you zoom in, you can see the two sensing coils. So far the results are quite good. I based my circuit design on an excellent article that goes into great detail on the sensing technology and the provides circuit design info (see the attached pdf). I'm running the sensing coils at about 2Mhz which keeps any drive coil fields out of the measurement. This is a very similar feedback system that was used by Fairchild back in the day for their Model 641 head (see attached pdf).

Mark

PXL_20260215_024053331.MP.jpg

PXL_20260215_023937697.MP.jpg

Designing and Building an Eddy Current Position Sensor _ Sensors Magazine.pdf

A New Stereo Feedback Cutterhead System.pdf

[Semar]

Hey trolls,

So instead of randomly tweaking angle / pressure / springs / vibes / magic and hoping for the best, I started writing a small Python tool to actually measure what my embossing head is doing.

Current setup:
DIY embossing head, cutting polycarbonate (CDs). Yes, I know. Don’t judge me.

What I’m building:

• Generates a structured test suite (log sweeps, multitone, tones, silence)
  
  I emboss that to disc
  
  Playback gets recorded
  
  Software analyzes:
  
  Frequency response via deconvolution
  
  Resonances
  
  Level-dependent non-linearity
  
  Basic wow estimation
  
  Noise floor
  
  Then it builds a pre-compensation curve based on what the system actually does

Important:
This is not “let’s EQ our way out of bad mechanics.”

The whole point is:

• Measure the real mechanical behavior
  
  Fix what can be fixed physically (angle, mass, damping, downforce)
  
  Only then apply pre-emphasis where it makes sense

Everything is offline measurement (emboss → playback → analyze). I’m not trying to read while cutting because that just turns into structural vibration soup.

I’m refining the measurement side now:

• Sweep deconvolution
  
  Multi-level comparison to detect non-linearity
  
  Automatic resonance detection
  
  Repeatable calibration presets

I’ll upload the tool here soon so other trolls can try it on their own questionable contraptions and tell me where it breaks.

The long-term goal is to make something genuinely useful — not just for me, but potentially a semi-professional calibration workflow for DIY heads.

If anyone here has:

• Experience measuring cutterhead response
  
  Data on typical resonance zones in lightweight builds
  
  Opinions on damping strategies
  
  Or just wants to tell me I’m overengineering this…

I’m all ears.

More soon.

Very interesting project. I ll folow you !!!!