A Better Explanation of Impedance for Audio Signals

This video is conceptual summary intended to help those trying to understand the output impedance of sources like microphones or instrument pickups and how they interact with the input impedance of preamps, interfaces, buffers, and amplifiers.

#microphones #impedance

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[alderaudio]

I have one update/correction I'd like to add to this video that has come up since I put it out. I mention in the video that impedance tends to go up as frequency goes down. This is true for ribbon and dynamic microphones as well as piezo based pickups, however it is not true for traditional electromagnetic guitar pickups. Wound pickups have an impedance that peaks usually somewhere from 2kHz - 8kHz or so. The same general principles from the video apply, however impedance mismatch will lead to loss of voltage more at the resonant peak of the pickup rather than in the low end.

I have continued to learn more about impedance while designing products for audio, and may post an updated video in the future. If that would be of interest to you, please let me know here in the comments section if you would like.

[robshift]

I have been working in sound for about 30 years and this is the clearest and most useful explanation in a practical sense that I have seen. 👍

[bassface]

It took me a few repeats but I got there in the end. It explains why plugging upright pickups into non-specific audio inputs can be hit or miss...
Thanks for the explanation.

[andybrice]

Another good analogy is acoustic impedance. Sound travels well through air (which has low acoustic impedance) and sound also travels well through concrete (which has high acoustic impedance). But it doesn't easily transition between the two mediums, because there's an impedance mismatch.

When a sound-wave in air hits a concrete wall, most of it will bounce back rather than continue through.
And the reverse is also true. A sound-wave in a solid-body guitar doesn't propagate out into the surrounding air much.

[thejacobean]

I'm a guitarist researching DI and line isolator boxes for the first time and you're right, useful/informative explanations are hard to come by. Strong work here. Great vid.

[GingerDrums]

I make a living from audio and just follow the rules of thumb on impedance. NOW I finally understand the logic to some degree. THANK YOU for this excellent content and delivery.

[owenchaim]

Fantastic explanation. Leaving out the wild math and just using relative values really helped illustrate the basic principle. Suddenly, the “high-z” jack makes sense lol. Thank you!

[TheTripboxer]

To quote Einstein "If you can't explain it simply, you don't understand it well enough." Well, you obviously understand what you´re talking about! :-) Thank you for this video!

[dpfeiffer_berklee]

Thank you so much for this video! Sharing with my Berklee Critical Listening class since this is the best "impedance matching" description I have ever heard.

[owlmuso]

Thank you. I am going to have to watch this video a few times to let the concept of impedence really sink in, and also how it applies to headphones. It looks like I was lucky to find this video early on in my search to understand impedence, so you saved me a lot of time. Thank you for generously sharing

[johneagle]

I agree, this is a better explanation.
It can also be used when impedance is not related to audio signals.
Thank you.

[JohnnyGuitar]

About 7:40m you mention impedance goes up in a microphone circuit;
I am only an electronic student since the 80s, but it sounds to me that it is exactly backwards: if the frequency induced in a dynamic microphone decreases, the impedance also decreases. Why? Because in the microphone you have a diaphragm attached to a moving coil. This coil is an inductor, and inductive reactance decreases as frequency decreases. As a matter of fact, if your frequency approaches zero HZ (DC) the coil becomes a short. The opposite would occur if instead of a coil, you had a capacitor. As the frequency lowers, capacitance reactance increases. If you approach Zero Hz the Impedance would approach maximum (an open circuit) because the capacitor has time to fully charge, and no longer passes any current. So you should specify what type of microphones you are referring to.

[iags]

Thank you! A lot of audio videos on this don't explain the physics, and a lot of physics videos on this don't explain how it applies to audio.

[manchagnu]

I wish I could give this video an infinite number of thumbs up.
Really really helpful! thank you kindly.

[TheZOLAIVE]

Thanks so much for those explanations. I knew about impedances matching but I didn't know why and how it could affect the sound. Congratulations for the time and energy you spent sharing those precious infos for musicians.

[edsonmarquezani]

Thank you so much for this video. I was going through a lot of videos with so much math, but I just wanted to understand how this applied to audio signals, but I've been building tube amps and everyone is always talking about impedance, but no one is gonna tell what it really is. The fact phase shifting doesn't actually apply to audio was veeery enlightening. Thank you again.

[beauhanson]

This is hugely helpful for a basic understanding of impedance. THANK YOU!

[ReshAleph]

After your intro and explanation I can't help but like you brother. Subbed.

[TheOdizeo]

Thanks for this. I'm a guitarist and I've gotten into the rabbit hole... Best explanation I've had

[stivep]

Voltage is just a potential. No Voltage nor current can be reflected. Your home electrical outlet has 110V AC and Zero current in Amps (Open Circuit) Xl and Xc are reactive components of impedance: Condenser Microphone=~variable capacitor. At lower frequencies, C reactance is larger, impeding current flow. Dynamic Microphone=~ coil changing its inductive reactance . When reactances XL = XC impedance Z=0 and you are in resonance . * It is a signal that is reflected if mismatch of impedance accrue .* Phase is very important in music from classical physics stand point too.