October 8th - Speaker design, Amplifier architecture Considerations of passive speaker construction -review of transducer principles -speakers are microphones too! -passive crossovers are made of speaker level LPF, HPF & BP filters -active crossover are just line-level LPF, HPF & BP filters -audio is AC; what happens when DC hits a speaker? -materials and physics of a speaker -cabinet construction -form factor, aesthetics and resonance are all concerns -dampening -porting vs. sealed enclosures -isolation -how do we control vibrations -active or “powered” speakers have amplifiers, filters and some DSP built-in Power amplification -observe the scale between microphone preamps and power amplifiers -bridging vs. stereo Specifications relevant to amplifiers and speakers -impedance and ohms law review -power (watts) -current (amps) -slew rate -THD -amplifiers/speakers and dBSPL -measured as 1 watt 1 meter away from the source Matching amplifiers & speakers -why we use amplifiers with higher power ratings than the speakers -so we don’t have to push the amplifier too hard -common variables on power amplifiers -’sensitivity’ controls -why we turn them all the way up -so we don’t clip coming out of the mixer -when we don’t -when they’re amplifying excessive noise -filters -to remove frequencies that aren’t going to be reproduced by the speaker -IE: HPF at 50 Hz on a small box Practical Speaker Setups Near-field monitors o equilateral triangle! o sounds great for one person, ok for the rest Small sound reinforcement o needs to sound great for a small room full of people, without being too loud Large sound reinforcement o needs to sound great for a large group of people Line arrays vs. Point source o Line arrays do a good job of distributing great sound across a large area and distance, but you need A LOT of them. o Point source do a good job of distributing great sound across a small area and you only need a few to do the job right Next Steps: So you want to work at Bose, EAW, Genelec? Designing, measuring and marketing the next revolution in headphones could be cool!