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Loudspeakers and Amplifiers How ‘good’ sound is created! The loudspeaker…. A magnet and a coil produce motion This is also called a ‘linear motor’ A paper or mylar cone is connected to the coil to push air. The mass of the cone must be light to push the air. The wire in the ‘electro-magnet’ has resistance. ( 4, 8, 16, 130 Ohms) This is ‘Energy Conversion’ Electrical energy is changed to magnetic energy. Opposing magnetic fields produce motion. The moving ‘cone’ pushes air and sound is created. Low frequencies use large ‘cones’ High frequencies use very small ‘cones’ A battery can test a loudspeaker.. A 1.5 volt battery will move the speaker cone. If it doesn’t move, it’s damaged! Alternating Current will move it back and forth. Speakers have resistance due to the wire used in the electro magnet. “Frequency Response” We expect the speaker to produce frequencies in equal amounts.. The ear can hear from 20 to 15,000 cycles per second. (Hertz) A speaker must be able to reproduce these frequencies. Not all can... $$$$$$ determines the quality~! An inexpensive speaker will produce sound from 100 to 5000 Hz. An expensive speaker will go down to 15 and up to 18,000. Often, a speaker ‘system’ uses three speakers. A BASS Woofer, a Mid Range speaker, and a Tweeter. The ‘Enclosure’ Speakers are put in large, non resonating boxes. They are ‘tuned’ to help create a ‘flat’ response. A local company, McIntosh Laboratories, has been building loud speakers for many years. Yes, in Binghamton~! The stereo system has ‘presence’ ‘Presense’ is like being ‘there’. The microphones, the recording equipment, the playback equipment, and the speakers all have to have a ‘flat’ response. Otherwise, you’re not ‘there’ ! Magnetic Tape isn’t ‘flat’ Magnetic Tape emphasizes the ‘highs’ The equipment must ‘de-emphasize’ the highs. This creates a ‘flat’ response. CD’s are flat!~ Not much to say here….. When the signal is digitized, there is no distortion of the signal! What is recorded, comes off the CD perfectly. Almost. The process is full of corrected errors! Signal Distortion - Ugh! Microphones, Amplifiers, Recording mediums, Speakers …. all introduce ‘signal distortion. Two types of Distortion 1) Harmonic 2) Intermodulation The Amplifier…. Takes a small signal (.001 Volts) and makes it much larger (100 Volts?) You need 100 Volts to put ‘power’ into a loud speaker. P=E²/R 100²/8 = ? Watts The Amplifer must be ‘Flat’ The frequency ‘response’ of the amplifier must be flat. It’s not easy or cheap! 15 Hz to 20,000 Hz. Much money is invested in doing this. At 1 Watt, the amplifier behaves differently than 100 Watts. How much is a Watt? A cheeeep AM radio, produces .1 Watts Rock Concerts can use 5000 Watts + Typical home systems are 100 Watts/Side Some people have a lot of power in their cars… P = ???? Tubes vs Transistors... Really uncultured people argue about the quality of amplifiers. We all know that transistors are better. Vacuum tubes are old and clunky and produce a lot of heat and waste a lot of energy and are obsolete. Most of the previous statement isn’t true. Obsolete in the Electronics Industry…. Simply means that new products are not being designed with these devices. Actually, there are more vacuum tubes produced today than ever per year. Every picture tube is a vacuum tube. There’s $$$$ in older tubes!