Audio and resistance (Ohms) ??? The big question

DeadPoet

DeadPoet

carpe diem
Hi y'all,

I have these question regarding resistance in audio for a long time... maybe there's someone out there that could explain a few things to me ??

1) mic's, mic-level, line-level, Hi-Z, Lo-Z....
Mic and line inputs expect a low resistance, right ? And instruments (bass, guitar) provide a Hi-Z output, right ? So what a D.I. does is lowering those Ohms. But why ? What happens electronically when eg. a line input gets a Hi-Z signal ? How does this affect the sound it'll pass through ?
And related to that question, there's a few preamps out there that have switchable input resistances... again, why ? What is the difference in mic color it will produce ?? Is this explainable in an electronic way ???

2) speakers:
could someone explain the thing with speaker ohms again, please ? I don't get it: when combining two 4 Ohm speakers you get a 2 Ohm speakers ??? I don't get it, you're ADDING resistance, you why does the ohmage drop ???



TIA,

Herwig
(electronic analphabete talking here as you notice)
 
DeadPoet said:
Hi y'all,

I have these question regarding resistance in audio for a long time... maybe there's someone out there that could explain a few things to me ??

1) mic's, mic-level, line-level, Hi-Z, Lo-Z....
Mic and line inputs expect a low resistance, right ? And instruments (bass, guitar) provide a Hi-Z output, right ? So what a D.I. does is lowering those Ohms. But why ? What happens electronically when eg. a line input gets a Hi-Z signal ? How does this affect the sound it'll pass through ?

Actually, we're talking about impedance, not resistance. Resistance is kind of a static thing - impedance is sorta like resistance in motion; there's a little more happening.

Most microphones are low impedance (50 to 600 ohms) and like to see a relatively low impedance input (usually around 1,000 to 2,000 ohms). Line level inputs are typically around 10,000 ohms and the levels range from about .25 Volts to a little over 1 Volt. Bass and guitar pickups are a very different story; they usually feel most comfortable seeing a load of 1 Megohm (1,000,000 Ohms) or more. Running them into a lower impedance input will result in a pretty thin wimpy sound.

And related to that question, there's a few preamps out there that have switchable input resistances... again, why ? What is the difference in mic color it will produce ?? Is this explainable in an electronic way ???

Because mics come in a variety of output impedances, having the ability to vary the input impedance on the preamp can often result in a better match to the microphone.

2) speakers:
could someone explain the thing with speaker ohms again, please ? I don't get it: when combining two 4 Ohm speakers you get a 2 Ohm speakers ??? I don't get it, you're ADDING resistance, you why does the ohmage drop ???

But you're NOT adding resistance; you're shunting the load when you add a second load in parallel. You're providing two paths for the signal to travel, so each speaker sees only 1/2 the normal load. If you wire two identical speakers in series, you double the resistance (and the impedance). If you wire two identical speakers in parallel, you halve the resistance (and the impedance).

Two 4 Ohm speakers in series = 8 Ohms; two 4 Ohm speakers in parallel = 2 Ohms.

TIA,

Herwig
(electronic analphabete talking here as you notice)
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