box tuning frequency

Box tuning frequency I see a lot of people asking what frequency they should tune their box to. The answer is actually somewhat simpler than it would appear. Every sub has a small frequency range in which it will perform to its full potential (i.e. 30-35 Hz or 45-48 Hz). It doesn’t matter if you are trying to achieve sound quality or ultimate volume, your sub will produce both of these qualities with in a certain bandwidth. This narrow band is not effected by several outside factors such as the location of the enclosure or the transfer function of the vehicle. To find out what this golden tuning range is for a given sub you have to run the parameters of that sub through a box design program that has the ability to calculate the amount of cone movement and response time that your sub will achieve during use throughout the usable frequency range (20-70 Hz). By trial and error you can quickly find the golden tuning range for your sub. In the best enclosure the sub must have acceptable cone control throughout the entire usable frequency range, it must not have any drastic phase or group delay shifts with in its usable range (read the help files in your box program and learn how to do this), and it needs to be able to play down to a respectable frequency. Sealed or ported all good subs should be able to play down to or below 45 Hz. The lower that a sub can play the more authoritive it will sound as long as you do not ignore the realities of cone movement and group delay (how far the cone must move and how fast the sub will respond). If your sub is correctly located in the vehicle (all the way to the far back or far front) all variations in the frequency response (transfer function) will be of positive amplitude at all frequencies within the usable range. Actual position of the sub its self will have little effect when located at the far end of the vehicle. Using basic crossover and equalization techniques you can easily achieve a stellar frequency response in any vehicle. Attempting to achieve a flat frequency response by taking the vehicles transfer function into account is simply an exercise in futility. In short a person of average intelligence and attention span can use readily available software to find this answer. The key is to take into account the limitations of the sub and not to fixate only on the frequency response.       Here is a tip. Make sure that your sub will have an F3 (outside of the vehicle) between 35-45 Hz. This is the range that has the most recorded energy regardless of the genre of music that you listen to. Just remember that the kick drum is at 42 Hz and most rap is recorded to be the loudest in this range. Any questions are welcome.

Not understanding why placement at the far front or rear of the vehicle will optimize the sound. Some of the best sounding subs are located more to the middle of the car. Hamfist's for one or about 50% of JL stealth boxes. Care to 'splain?There is no such thing as free installation!

There is a short list of things that will drastically effect the frequency response (transfer function) of a sub in a vehicle. The short list is as follows in order from most prominent to least. 1.     Boundary effects caused by the sound waves reflecting off of the interior surfaces of your vehicle (back wall, wind shield, ceiling, floor). For more info checkout http://www.trueaudio.com/st_spcs1.htm . Due to the large size of sign waves in the bass range (100 Hz = 11.3 feet and 20 Hz = 56.5 feet long) the boundary effects exist everywhere in any vehicle. In other words at all points in side a vehicle the sound level potential is drastically increased due to the waves having to bend and consequently multiply themselves. 2.     Cancellations. Cancellations can virtually eliminate sound at a given frequency, (despite boundary effects, multiple speakers, or massive power) caused by an emitted wave encountering a reflected wave (coming from the front of the vehicle) that approximates 180 degrees of phase difference. As frequency lowers the probability of this occurring increases in the event that the sub is located anywhere other than the far front or the far rear of the vehicle. As you approach the center of the vehicle the range of effected frequencies expands. This is a mathematical fact. 3.     Multiple acoustic resonant chambers (trunk, passenger compartment, etc.) interacting with each other. 4.     Lossy boundaries such as flexible ceilings or door skins (defeating boundary effect gains) are frequency specific and non linear. Thus they must be measured and not predicted. These are the four most basic acoustic rules to follow when engineering a subwoofer for a car. There are many more complex effects and calculations that can be made but all are dwarfed by these four. There have been many great systems produced where the sub was not located in the far front or the far rear of the vehicle. These vehicles all perform in spite of this fact not due to it. There are many valid reasons why an educated installer would locate a sub in an area other than the far rear but all instances include a substantial compromise in subwoofer output and consequently quality. Since the sub must physically move more air to make up for this loss and consequently produce more distortion as the voice coil leaves the most dense part of the magnetic flux.