# Useless Newbie

Joined Mar 20, 2005
1
Hi guys and girls, I'm a Music Production student from the UK, and although the majority of my degree focuses on the end user for hardware etc, it does involve some (according to my lecturer) 'basic electronics'.....

But unfortunately I'm the least electronically minded person around, I just can't get to grips with it, so I have a few questions to see if you can help me out please!

1) Given that a typical loudspeaker will have a nominal resistance of 8 ohms, why do you think a 220 ohm resistor was used to represent the loud speaker load in the experiment?

The following question is related to equalisers and opamps....

2) What effect will a series connected capacitor have on an audio signal at;

a)Low audio frequencies

B) high audio frequencies

Hope you can offer me some help guys!

#### beenthere

Joined Apr 20, 2004
15,819
Hi,

I would be willing to bet that the 220 ohm resistor was used because a 220 ohm 2 watt resistor is lots cheaper than an 8 ohm 100 watt resistor. It won't do a good job of simulating the speaker load, at any rate.

Your capacitor will appear as an increasing series resistance as the applied frequency drops. Therefore, speaker output will drop too.

#### Brandon

Joined Dec 14, 2004
306
Originally posted by beenthere@Mar 20 2005, 03:07 PM
Hi,

I would be willing to bet that the 220 ohm resistor was used because a 220 ohm 2 watt resistor is lots cheaper than an 8 ohm 100 watt resistor. It won't do a good job of simulating the speaker load, at any rate.

Your capacitor will appear as an increasing series resistance as the applied frequency drops. Therefore, speaker output will drop too.
[post=6251]Quoted post[/post]​
What he said, also.

The cap also blocks any DC bias which can burn out speaker coils. To high frequencies, caps look like short circuits. They travel right through them. In effect the cap at the output adds a high pass filter with some nominal low frequency as the main cut. Many times they amps to have their cut off frrequency about 30-60Hz. Some times a little higher if the system is not built for low frequency.