The Science of Speakers
magine, for a moment, that you are a musical note. A note to be played by the flute in Smetana’s “The Moldau.” As a note played long before that has been recorded on CD, it is almost your turn to play. In a mere instant, you are read of the disc. As it’s read, you are transformed into electrical oscillations on the way to the stereo amplifier. Considering how small you are, you have covered a lot of distance. Your journey had shaped you—your personality, a little different than when you first started. The superb sound system you are passing through adds essentially no coloration of its own. Ultimately, you reach the speakers, and you are converted from electrical signals to sound. In contrast to the stereo amplifier, the speakers are designed poorly, and as you speed through space, you realize your character has changed drastically. You no longer sound like a crisp note from a flute, but a tinny buzz like listening through a pringles can. All of that, for nothing. The speakers are the final mark in a Hi-Fi system. Audiophiles quickly spend hundreds and thousands of dollars on high-quality equipment. Purchases are carefully reviewed, going over technical specs and capability.
However, when people commonly buy speakers, specifications are largely ignored, and there is little thought as to how the speakers will perform in a new environment. A quick reason that little consideration is done with speakers is that the outstanding ones are expensive. A pair of quality loudspeakers in a handsome oak or walnut enclosure can easily cost $5000-$6000, and even more. Another reason is that speaker specs are technical and not easily understood. This guide seeks to address both of these issues. You will learn how to save money by building your speaker systems while getting speakers that perform well beyond their price tier. Even if you have little woodworking experience, there are kits so you can create your own affordable, quality speakers in a short amount of time.
While you are having fun putting together your speakers, you’ll learn several things;
• The different types of speaker drivers — woofer, midrange, and tweeter — and the purpose of each.
• How to understand speaker specs.
• How cabinet design affects sound quality and color.
• Woodworking techniques to build a solid cabinet — from small bookshelf speakers to tall floor-standing towers.
• About the role of and putting together the crossover network
• How to connect speakers to your stereo system beyond just wiring
Moreover, if you don’t plan on building your own speaker system, this guide will assist you adequately appreciate the position speakers play in modern, high-end Hi-Fi systems. With the information presented in this guide that’s easy to understand, you’ll discover how to decipher speaker specs, how to assess the qualities of the diverse speaker configurations, and how to recognize a reliable pair of speakers. There is a lot to cover in the articles that will follow. The rest of this article presents to you the science of sound and how speakers replicate that sound. Understanding the principles of sound generation will help a lot in improving your grasp of how speakers work.
The Science of Sound
In general, the sounds you hear, both ones that come from a stereo system or the environment around you, are waves or compressions that move through the air. Sound sources make the air vibrate, jumping up and down until it reaches the listener. These waves propagate out from the source in oscillations, similar to the ripples which travel outward from a rock dropped in water. The listener picks up the air vibration with their eardrums, and the inner ears change it into signals that go to the brain. Without a medium like water or air, sound can’t travel. The means to regulate the air decide what occurs to the music.
The intensity, or volume, as it’s commonly known, of sound, is determined by the amplitude or height of the air particle vibrations. Waves that shift in the air a little quantity will produce a quiet sound, perceivable to solely those close to the source. The eardrum isn’t vibrated much by low-amplitude fluctuations, so the audio is considered low-level. Huge oscillations that roll about the room produce a massive sound. Your eardrums respond to it a great deal, and the audio is deemed to be loud. If the sound waves are too large and the volume is too loud, your eardrums might become damaged. The oscillation of the air particles in a sound wave creates small changes in local air pressure—the higher the pressure change, the louder the volume. Sound pressure level (SPL) measured in decibels (dB). 0 dB does not mean absolutely any sound; it means a sound level where the sound pressure is equal to that of the reference level. see (Sound Power and Pressure Measurements. https://www3.nd.edu/~atassi/Teaching/ame553/Notes/Sound_power.pdf) It is a little pressure, but not none. Zero dB represents the SPL of a 1000 Hz tone that is just barely hearable by a person of normal hearing in a tranquil environment. The level of other sounds is measured or expressed relative to this lowest audible sound level. Again, for a person of normal hearing, a change in SPL of 10 dB is heard twice as loud as the original audio. Studies show the human ear cannot tell a difference of sound level smaller than 1 dB.
The Three Sound Ranges
The audio spectrum of 20 Hz to 20 kHz can be grouped into three main classifications: low, medium and high frequencies
• Low sounds, referred to as bass, are made by bass singing voices and bass instruments, such as the string bass and specific types of drums.
• Middle sounds, called midrange, is where most singers are at, guitars, and many other musical instruments.
• High sounds, also called treble, are made by high sounding instruments like violins and flutes.
Speakers are designed to generate sound well within one of these three ranges efficiently.
• Large drivers, known as woofers, reproduce the low end of the frequency spectrum and gets weaker as it approaches the mid-range
• Medium-size speakers, known as midranges, reproduce middle and some frequencies in the higher range
• Small speakers, known as tweeters, target reproducing all high frequencies
Direct Sound and Reflected Sound
Noise can either be direct or reflected. Reflected sound is what’s known as an echo. Although the term reverberation may be used in audio, reverberation is the summation of all echoes. In an empty house, as you make footsteps or small noises, you can audibly hear the echo. It’s quite evident when there are no other objects to catch the sound waves. When listening to music through an audio setup, your ear catches a part of the sound straight from the speaker. Other parts reflect off of any other objects in the room. These are echoes. The collection of all that you hear at a singular point is the reverberation. Contrary to intuition, echoes can be used to your advantage if designed carefully. For example, echo raises the intensity of low frequencies and helps speakers propagate such sounds more effectively. Echo gets a small speaker to sound fuller.
How Speakers Function
It can be more apparent to understand how speakers work by beginning at how our eardrums do, then reversing the method. To hear sound, waves enter the ear canal and then vibrates the eardrum. High-frequency sounds vibrate the eardrum faster, which we hear as high pitched noise. In opposite to that, lower frequencies vibrate the eardrum slower. The sensitivity in the inner ear converts the physical sound into electrical signals that go to the brain.
For speakers, the signal inversely starts as electrical signals from the amplifier. A lens CD player sends electrical signals to the amplifier. The amplified electrical signals travel to the speaker. Finally, the speaker responds to the signals by moving a physical cone back and forth. This makes the air around the speaker driver to pressurize and depressurize, creating sound waves in the air. These sounds travel through the air and are heard by you. High-frequency signals are created when the speaker cone vibrates rapidly. Low-frequency signals are created when the cone vibrates slowly.
Types of Drivers
Almost all speakers are electrodynamic. Using a coil of fine wire and a magnet to create the fluctuation in the cone, which in turn produces sound. There are special types which include piezoelectric speakers. The frame, usually made of metal, of the speaker keeps everything stable and is used to attach the speaker to a cabinet or panel. It also has gaping holes in the back so air can circulate around the speaker cone. The diameter of the frame can range widely from one inch to over 15 inches. Usually, the larger the size of the speaker, the more volume the speaker will produce. Remember, larger drivers are used to reproduce bass sounds; smaller speakers are typically used to reproduce midrange and treble sounds.
The magnet and voice coil makes up the driver of the speaker. The voice coil consists of the winding of a fine wire wound on the bobbin. Electrical signals are transferred to the voice coil. When varying electromagnetic fields are produced around the voice coil, it is as if you are bringing two magnets together, but alternating one of them so that sometimes the magnets pull together and then push apart. Since the speaker’s magnet is fixed in the frame and the voice coil is free, the voice coil oscillates as the magnetic fields interact. As audio signals continue to pass through the speaker, the changing electromagnetic field induces the voice coil to propel back and forth over the iron core of the magnet. The bobbin is attached to the cone, so when the bobbin moves the cone and causes it to vibrate. The dust cap covers the bobbin and the inside center of the cone. This keeps unwanted dust from getting into the rift between the voice coil and the magnet core.
We have just the place for you to start
Part-Express.com is where I got started in my speaker building hobby along with the help of a fellow audiophile neighbor. Together we completed one of the kits for a pair of studio monitors. They sound spectacular! If you are like me at the beginning and feeling pretty clueless on how to build cabinets and select the right parts to build a pair of stellar speakers I reccomend you try this kit to get your feet wet. Presenting the Hitmaker MT!
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From Part-Express: The Hitmaker 2-way studio monitor kit will deliver the full, balanced, and effortless sound of high-end nearfield monitors for a fraction of the price. Designed by Paul Carmody, this kit includes almost everything you need to build a single high end studio monitor, including: a knock-down cabinet, drivers, crossover components, and damping material.
These speakers are my daily listener. At the time of writing, the coronavirus epidemic is still having me work from home. These are in my office and constantly playing music. I just love how they sound and you will too. The kit is a single speaker so make sure you get two to build a stereo setup. You won’t be disappointed with how they sound. Click the button below to see more about this speaker.