"Thiele/Small" commonly refers to a set of electromechanical parameters that define the specified low frequency performance of a loudspeaker driver. These parameters are published in specification sheets by driver manufacturers so that designers have a guide in selecting off-the-shelf drivers for loudspeaker designs. Many of the parameters are strictly defined only at the resonant frequency, but the approach is generally applicable in the frequency range where the diaphragm motion is largely pistonic, i.e. when the entire cone moves in and out as a unit without cone breakup.
Using these parameters, a loudspeaker designer may simulate the position, velocity and acceleration of the diaphragm, the input impedance and the sound output of a system comprising a loudspeaker and enclosure. Rather than purchase off-the-shelf components, loudspeaker design engineers often define desired performance and work backwards to a set of parameters and manufacture a driver with said characteristics or order it from a driver manufacturer. This process of generating parameters from a target response is known as synthesis. Thiele/Small parameters are named after A. Neville Thiele of the Australian Broadcasting Commission, and Richard H. Small of the University of Sydney, who pioneered this line of analysis for loudspeakers. These measurements are also used for designing enclosures for Subwoofers.
A 2-way speaker, also known as a coaxial speaker, has a separate tweeter mounted on a pole assembly in the center of the speaker. The tweeter has a built-in crossover which separates the high frequencies and gives more clarity and definition to your music.
A 3-way speaker, or triaxial speaker, has an additional midrange speaker mounted alongside the tweeter on the pole assembly. A crossover filters the correct frequencies to the appropriate speaker, providing increased clarity and a wider frequency response.
An example of a 2-way speaker 3-way speaker
A dual cone speaker is classed as a full range speaker, but instead of using a separate tweeter, it has a small cone in the center directly connected to the voice coil that reproduces the high range frequencies due to its specific design. While inexpensive compared to a separate tweeter, it is not as efficient.
This refers to a speaker that generally ranges in size from 3—1/2” to 6—3/4” that reproduces the midrange frequencies. They would be generally be used in a system that has separate speakers for low,mid and high range that are driven individually.
The high range frequencies are reproduced by the tweeter. In two and three way speakers the tweeter is mounted in the center of the mid cone on a pole piece, and in component speakers it is a separate unit.
Components or Separates
Component systems produce better definition and detail, as well as giving you the ability to optimize imaging and soundstage reproduction. This is partly due to the vastly superior cross-over system used in most component systems and the ability to place tweeters in the best position to enhance imaging.
This refers to the individual vocal and instrumental “images” that are reproduced to create your stereo system's soundstage. The better the soundstage reproduction, the greater the perception of width and depth.
Imaging is the ability your stereo system has to reproduce the location of individual instruments and vocalists accurately as they were positioned during the original recording. Tweeter placement is important, ideally with equal and unobstructed path lengths between your tweeters and your ears, to create a soundstage that is lifelike.
A voice coil is a length of insulated copper or aluminium wire wound onto a circular former that provides the motive force to the cone by reacting with the magnet when the current is passed through it.
Surrounds can be manufactured from a variety of materials. The most common in car audio is butyl rubber as it tends to last longer. Some manufacturers use foam or cloth. The surround allows the cone to travel in and out without restricting the length of travel.
Maximum / Peak Power
The Max/Peak power rating of a speaker is the amount of power that the speaker can handle in short bursts or peaks without causing permanent damage to the voice coil. If this rating is exceeded constantly you will risk burning the voice coil.
What is a Crossover?
Crossovers are essentially filters that separate or block frequencies and route them to the correct speaker. There are two common types of crossover, ”passive” and “active”.
Passive crossovers are non-powered and are most commonly used with component systems in line with the speaker wires located between the amplifier or head unit/source and speakers. They are also used in full range speakers. Both two and three way speakers have passive crossovers to separate or block the frequencies for the mid and/or tweeters to ensure the appropriate frequencies are delivered to the respective driver.
Active crossovers are electronically powered units that are placed in line with the RCA signal lead between the head unit/source and the amplifier.
They will provide better signal separation and unlike passive crossover there is no power loss.
There are three main types of crossover filters: high-pass filter, low-pass filter, and a subsonic-filter.
A high pass crossover allows high frequency signals in the 5kHz-20kHz range (generally) to be passed to the speaker/tweeter while the lower frequency signal is blocked.
A low-pass crossover allows the low frequency signal in the 50Hz-250Hz range (generally) to be passed to the speaker/sub with the higher frequencies blocked.
A subsonic filter is essentially a high-pass crossover which blocks the frequency signal, generally, from 10Hz-40Hz. This signal often contains no music and its removal will improve woofer control and sound quality.
My speakers are 300 Watts “Max” and 90 Watts “Rated Power”. What size amplifier do I need to drive them to achieve the best performance?
When you are choosing an amplifier to drive speakers or a Subwoofer, you should use the “RMS” per channel ratings (amplifier) and the “Rated Power” (speaker/subwoofer) as the reference for your choice. Always define which ratings you are comparing and try and get them as close as you can.
“Max/Peak” Power Rating
The “MAX/PEAK” power rating of a speaker is the amount of power that the speaker can handle in short bursts or peaks without causing permanent damage to the voice coil. If this rating is exceeded constantly, you will risk burning the voice coil.
“Rated Power” Power Rating
The “Rated Power” rating of the speaker is generally considered to be the nominal constant power that the speaker will handle continuously without causing damage.
Therefore if your speakers are rated at 90 Watts (rated power) you should drive them with an amplifier that is capable of supplying 90 Watts RMS per channel or as close to that as possible. That is not to say that an amplifier capable of a higher output cannot be used if the amplifier settings are managed responsibly, remembering the potential to overdrive your speakers exists. This rule also applies to using an amplifier that is under driving your speakers. Constantly driving a distorted signal from an overdriven source to your speakers can cause damage to the voice coils.
I have installed a new set of speakers and there is no bass. Have I done something wrong?
One of the most common causes of lack of bass from speakers is out of phase wiring. This occurs when the positive and negative wires are connected incorrectly. The positive and negative wire connection at the source must be the same at the speaker connection.
Check the connections for consistency first.
Another clue to this fault is that the bass will sound louder outside the vehicle than inside.
Most speakers will have a positive (+) sign and/or a negative (—) sign on the terminal, with some featuring a red mark for positive and/or a black mark for negative. If in doubt, there is a relatively simple way to check the phase of the wiring. Using a 1.5V or AA battery, hold the positive and negative wires connected to your speaker on the relative terminals of the battery. If in phase, both speaker cones will move outward, but if one is out of phase the cone will move inward. Both speakers must move in the same direction when tested.
I have installed a new set of speakers and they sound distorted and crackly, what could cause this?
A common installation error we see that results in these symptoms occurs when the speakers are mounted in the vehicle and the mounting holes are drilled with the speakers in place. When the drill bit is withdrawn from the hole, the material that has been removed (metal or wood etc) can drop into the speaker and/or voice coil, resulting in speaker failure. This is not covered under the product warranty. Always use the provided template to pre-drill the mounting holes.
Another cause of distortion or crackling is a burnt voice coil, which is a symptom of overdriving the speakers or delivering a clipped or distorted signal to the speakers from the source unit or amplifier. You may be able to smell that the coil is burnt, or check by applying gentle, even pressure to depress the cone of the speaker to feel if the coil is rubbing or binding.
Mounting speakers on an uneven surface can also twist the frame out of shape and cause the voice coil to rub and cause permanent damage.
Insecure wiring or poor connections are common causes of crackly or distorted sound from speakers, making it important to double check all wiring.
I have no sound coming from the new speakers I have just installed. What could be the problem?
First you need to check the wiring from your source/amplifier to your speakers to ensure that no wires are going to ground/earth by touching any part of the vehicle or vessel, as this could put the source/amplifier into protection and/or terminate signal output to your speakers. Check the fuses etc as well, as grounding the system may blow fuses.
In some cases you may cause permanent damage to the source unit by grounding the speakers (output IC failure) so paying careful attention to securing and insulating wiring is very important.