Show 224 – Explain Impedance Like I’m Five, and more!

This week we talk with Peterson Goodwyn (DIYrecordingEquipment.com) to clear up the confusion about electrical impedance, and does it in a way that even a 5 yr old like Jon can understand.

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12 thoughts on “Show 224 – Explain Impedance Like I’m Five, and more!

  1. Wow… great show, but I’m afraid I really am going to have to listen to it a few more times before this impedance thing fully sinks in.

    Looking forward to the new format. I’ve often thought that the comments section and the “show” section felt like two different shows. Now they are!

    -Jet

  2. Hey HRS, Long time listener and first time commenter. Listened from start to finish with all the episodes so put me down for one of those diplomas as well please Ryan 🙂

    And now I have a complaint to make to you Ryan…… I am addicted to DIY all because of you!!!

    I started out by buying a Golden Age Pre73 a couple of months ago and absolutely loved it which made me want to get more. Then I started to build a new house so have been living rent free at a mates place while i’m waiting for it to be finished. All this has done is free up more cash to spend on the new studio which is being built into the house….

    So first month of living rent free meant I could order another 3 Pre73’s. Then I thought with all this free time and having no studio to record out of for a couple of months maybe I could try my hand at a DIY project….. So first came an MXL990 modded into a FET U47. But then I had to turn it into a stereo pair so along came another mod kit. And I was hooked….. 2x U87’s, 2x 414’s and 2x C12 builds later and I was well and truly along the DIY road that never ends.

    But now I think I was ready to progress from the easy drugs onto the harder stuff…. So along came the 51x rack space and an API VP26 preamp kits. But now I have another 10 rack spaces to fill up, so then came another VP26, 2x VP312’s and 6 VP28 preamp kits…. I am getting worried now because I can’t seem to stop!!!

    And now worst of all I have started looking into outboard eq’s and compressors…..
    Those bouncing needles, shiny knobs and flashing led’s just look so attractive and how can I say no to that!!!

    Needless to say I am finally going to have some REALLY NICE gear in my new studio as I think I had started to outgrow my cheap chinese LDC’s and my Behringer ADA8000’s…. Now all that is left is to upgrade my interface to an SSL AlphaLink and my studio will be complete for now 🙂

    Thanks guys for all your time and effort and advice helping out us project studio enthusiasts who want to turn this hobby into a full time job. And I am well on the way to turning this hobby into some regular income 🙂

    Cheers,
    Marc

  3. Here it is stolen from wikipedia= Electrical impedance is the measure of the opposition that a circuit presents to a current when a voltage is applied.(PERIOD)

    In quantitative terms, it is the complex ratio of the voltage to the current in an alternating current (AC) circuit. Impedance extends the concept of resistance to AC circuits, and possesses both magnitude and phase, unlike resistance, which has only magnitude. When a circuit is driven with direct current (DC), there is no distinction between impedance and resistance; the latter can be thought of as impedance with zero phase angle.

    Interpeted for the lay persom via Joe Marsh..AC is complex and also deals with the Phase angle, where as DC is steady… it only has a simple voltage, simple current, and simple RESISTANCE… Where AC is different, is that, AC is constantly changing (Sine wave like) its determined by what is in the circuit on the AC side..a circuit has wires,capacitors, resistors, inductors,- well they all start to ADD up in a AC circuit..wire length starts to at like inductors,wires next to each other start to act like capacitors, combo’s of various parts become filters…the whole circuit works together on the frequency level. Its very complex. Circuits become inductive or capacitive, the resistance of a circuit actually has a DC and AC value. The AC value, is called the Impeadance….

    I support your movement Peterson..your a great guy…keep up the good work!

    • Hi Joe,

      Thanks for the kind words!

      I know everything you laid so nicely out above, but I’m not sure which part of it is controverted or not reflected in the podcast.

      Keep in mind that, to keep the concepts simple, I used “audio signal” instead of alternating current. I also did not go into the complexities of how inductance and capacitance (both intended and parasitic, as you pointed out) contribute to a circuit’s net impedance, except to say that impedance is frequency dependent. (Which again shows to the electrical-minded folks following along that I was talking about AC, since DC has no frequency).

      So again, I’m all ears and I’m enjoying this friendly discussion but honestly would appreciate which points of the podcast caused you to shake your head.

  4. About impedance and headphones.

    Peterson, you said that if you put a potentiometer between the amp and the headphones, the resistance of that pot will change the impedance and therefore the frequency response of the headphones. Later on in the podcast you advised against putting any unbuffered passive elements between the power amp and drivers. I’m going to have to disagree with you here on one point.

    Putting a passive resistance, between the power amp and the drivers will only change the “real” part of the impedance, not the “imaginary” or frequency dependent part of the impedance. This is getting into some math and electrical engineering theory, but impedance is a complex number, and as such it has a real and an imaginary part. You can think of the real part as the frequency independent part, and you can think of the the imaginary part as the frequency dependent part. Putting a resistor in-line with a speaker driver, for example, will result in the impedances being added together. Since the resistor has zero imaginary part, the frequency dependent nature of the system does not change, only the real part.

    I bring this up because if what you say is true, devices like monitor controllers and speaker attenuators, which the guys have talked about on previous shows, would not work properly.

    So that’s my EE inspired nitpick, besides that I think your explanation of impedance was very accurate, and I really liked the snare drum baffle analogy. As a computer engineering student with an interest in audio (more live sound reinforcement than recording), I found your segment very helpful.

    • Hi Marcos,

      Point well taken, thanks for your input. In fact, I’m surprised and somewhat self-congratulatory that those are the only points I messed up from an EE’s point of view!

      That being said, there are two reasons I advised against putting a resistive element between a power/headphone amp and drivers/headphones. The first is simple driving capability: putting resistance in series with an amp output compromises the amp’s ability to put power into the speakers and creates a voltage divider with the input Z of the speakers through which signal is lost. The second is that series resistance on the output, while having no freq-dependent component on its own (as you pointed out), may exacerbate the parasitics inherent in the hookup wire and the drivers themselves which may indeed affect frequency response. Granted, both the series resistance and the parasitic capacitance/inductance of the system would have to rather high for a resulting filter to affect the audio spectrum, but to my mind adding resistance is opening the door for trouble.

      So, that’s my take on it. I’m curious what your thoughts are about those ideas?

  5. Great show. This is probably the best description of impedance that I’ve ever heard. I’ve always thought I’d had a decent grasp on impedance; this episode really expanded my mind in regards to the subject. It’s like it lowered my internal impedance to impedance knowledge!

  6. Hi guys!

    How about a segment talking about the use of reference tracks when mixing – along with some suggested listening (i.e., examples of great mixing, maybe a pointer or two as to what is so great about them)?

    BR,
    Michael

  7. The topic still eludes me. There seems to be some amount of impedance between Peterson and my brain. I’m gonna have to listen to this again… This might be too much to ask but is it possible to do a demo video complete with meters to show the effects of impedance along the signal flow? I think visuals will reinforce the learning process, especially for non electronic enthusiast/engineer types like me.

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