- Technical support from FUSION Electronics
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.
The main cause of subwoofer failure is overdriving or driving a clipped or distorted signal continuously to your sub. This can result in a mechanical or electrical
failure. With electrical failure the result is normally a burnt voice coil causing the sub to go open circuit or in some cases short circuit to ground.
It is important to match the “RMS” ratings of your sub to your amplifier to avoid overdriving. Clipping or distortion is the audible sign of an unclean signal and this can originate from any piece of equipment in the signal chain. What this means is you may be only driving your amplifier at say half power yet your head unit/source may be driving at close to it’s maximum output which could be supplying a clipped or distorted signal to the amp thus creating the audible distortion you hear.
Mechanical failure is when the spider or butyl surround rips or tears or sometimes the voice coil jumps the gap. What we mean by jumps the gap is that when the sub is being mechanically overdriven it can result in over excursion or over travel. This result is the voice coil leaves the gap that it travels in and results in failure.
Mechanical failures in general are all symptoms of over excursion which can be caused by having the wrong size enclosure and or overdriving. It is very important to follow the recommended enclosure volumes to ensure the optimum performance of your sub and to protect it from these types of failures. Another important fact is the port length and diameter in relation to the tuning of the enclosure as this also could adversely affect performance and reliability.
My speakers are 300 watts “MAX” and 90 watts “Rated Power” what size amp
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 amp
capable of a higher output cannot be used if the amplifier settings are
managed responsibly realising 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
The first thing to do is check that your amplifier is not in protection. If it is, this could be a sign that you have a problem with your sub or amp. The easiest way to check if your sub is causing your amp to go into Protection is to disconnect the sub and power up the amp. If it does not go into protection with it disconnected your sub is the problem. Check for a burnt smell, or try and move the cone gently by pressing down In the centre to see if it has seized or Is rubbing. It should move freely if the coil is not damaged. If when you disconnect the sub the amp still goes into protection there is every reason to suspect your amp may have an internal fault. Unfortunately this does not mean your sub is guaranteed to be fault free as the amp May have suffered as a result of the sub failing or visa versa so at this point we would Recommend that you return either one or both of the units to your place of purchase for inspection by the authorised dealer under the warranty Provision of the product (if applicable)
Install tips and guides
All Fusion Subwoofers have an optimum Enclosure Volume which is based on a specific tuning point. To calculate volume you need a calculator and a tape measure and the following formula.
Length (in inches) x Width (in inches) x Depth (in inches) divided by 1728 = volume in Cubic feet.
Length (in Centimeters x Width (in Centimeters) x Depth (in Centimeters) divided by 1000 = volume in cubic litres .
Always allow for the volume of the subwoofer that will be inside the enclosure and the port if applicable. Ensure you measure the inside dimension allowing for the enclosure material thickness.