Speaker Characterization

Speaker Characterization:

power-handling rating (speaker wattage)
how loud you can play music
sensitivity
how much volume the speaker will produce with a given amount of signal, measured in decibels.
variable with frequency
The higher the sensitivity, the better.
Impedance
measure, in ohms, of how much of an electrical load the speaker presents to the amplifier
A higher measurement = greater resistance = less current that the speaker requires.
(An 8-ohm speaker draws roughly half as much current from an amplifier as a 4-ohm speaker)
phase angle
looks at whether the impedance of the loudspeaker is resistive, inductive, or capacitive at any given frequency.
the more severe the phase angle, the more difficult the speaker is to drive
frequency response
speaker's tonal quality (bass-heavy, overly bright, etc.)
Test response:
Drive speaker with constant amplitude test tones at different frequencies (low bass to the high treble)
measure relative volume (aka amplitude, sound pressure level, or SPL)
ideal performance = flat response

Peaks at "A" (particularly at 2 kilohertz) are high enough to make certain instruments, voices, and notes stand out
dips at "B" may cause other sounds to seem distant or too quiet
intersection at "C" between the sub and the main speaker may cause the bass to sound disjointed and unattached from the rest of the music or soundtrack

Don’t Fry Op Amp !!!

Do Not Switch power supply input to OP AMP or else you’ll FRY IT !!!

Be very careful before inserting leads into holes of Protoboard.

Don’t use screwdriver to lift OP AMP off protoboard -- you can short it out if you touch one of the +/- 12 V legs.

Do Not Switch Test Leads on DVM when testing Op Amp or else you’ll FRY IT !!!

Having Trouble?

Plug function generator directly into amplifier instead of microphone

Once you have the amp working with the function generator, add microphone and speaker

Test your amp and microphone at the front of the class

Circuit Block Diagram

Example Graph: (Thanks Janine!)