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Cap on tweeter for DSP and speaker measurements.

I see a lot of people recommend having a capacitor on the tweeter before taking measurements and also when using s DSP. Anyone have a quick application guide? I will be working on a dome tweeter as well as a few ribbons. Thanks.


  • True ribbons should never be connected to an amp without a capacitor. They will short the amp out with their 0.2 ohm DCR. Jeff likes to use a 10uF, 25uF, or 100uF depending on what driver he's testing.

  • I have a four way multi amped system.  I am thinking about putting caps into the top two channels which I have never done before  (I did put a smallish fuse in series most of the time) in case one of my elderly amplifiers blows an output device and tries to DC kill one of my not easily replaceable Beryllium drivers.  I would hate to have to replace any of those.  What kind of caps to people here like for that purpose?
    I was not aware that ribbons have such low DCR thank you for mentioning it.  I have a pair of Pioneer ribbons that were once in a pair of hi tech Phase Linear speakers from the late seventies.  I will measure it before I hook it up to anything.  It was a three way system.
  • Ah, was looking for this thread to ask questions in right place...
    So revisting my first 2 way attempt of own xover development after learning some things, measurement skills still work in progress. But did get to point where at least can take measurements over to vituix to get good idea before the clip, measure, adjust, repeat process. That first project was some leftover (from dsp trial days) sbcac5's and fountek neo3.5 ribbons. Question is if put 20uf on the ribbon for raw measurement, take over to simulator and most likely 3rd order anyway, do I just model like 2nd order knowing really a 3rd order with 'not shown' 20uf cap? Also, would I also do same for impedance measurement (dats)? Aware I would refine via proto connections, just easier to get better idea of phase alignment in simulator where otherwise it's can be a painful trial n error to get summing response that is near in phase.

    Have read about and understand why phase alignment important, but question i have is how detrimental for nice deep reverse null?

    Last question, off topic, any go to references for creating nearfield merged with gated measurement process? Scott H's videos great but didnt reach conclusion. In those other efforts for 3 way would be better to do more than go by ear which suspect many diy'ers resort to in the end. Of course, imagine bettering measurement game would pay dividends.

    Sometimes wonder if some magical crossover cookbook thread, well maybe a book and experience on how to manipulate 'knees' - whenever i start to mess with at a per driver level throws off all the phase expectations and hard to know when a notch filter right thing (feels like dsp hacking at times that way)

  • No need to design your crossover with bad data. There’s plenty of easy methods to compensate for the series capacitor. Using 2channel measurement following VituixCAD measurement guide? Then place reference probe after the cap and it’s compensated for. Using USB mic? Compensate for your cap using calculator tool, you’ll see the option there, hover your cursor over it for instructions.

    Reverse null is just a basic phase check, same information can be obtained by simply reading the phase graph.

    Measurement guide includes instructions for merge process. Some examples of good merge process can be found in my ViruixCAD tidbits file here:

    I'm not deaf, I'm just not listening.
  • edited December 2023


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