Design limitations – Just a few important ones to note
If you have ever discussed with me anything about design work and what I can do, you may have heard me talk about limitations; The defining feature of design. Nothing in design can be finished without knowing its limitations. Otherwise everything would be much larger than they are, in which we could not use them in vehicles as easily. Even in HT environments, some LF acoustical models cannot effectively be optimized due to physical constraints. Because of this, we have to alter everything. This is what makes design so complex.
So what limitations do we normally deal with? It is important to know this, because understanding them will help you understand what you can efficiently get out of what you are trying to do.
One of the first limitations is the mentioned physical design size. Good examples are for car audio use. Most of us do not have the room to use what we want for subwoofer boxes because we cannot fit them in the vehicle. We compensate by altering a design to best match the frequency range of interest without losing much efficiency. And efficiency is the key to performance. In fact, sensitivity is the focus of design in theory. The fundamental concepts and formulas behind it all, lie within a specific value for each calculated design part (port, box, tuning, etc); all figured by a certain sensitivity. The problem is, the normal sizes are too large due to coupling the design to low frequency waveforms.
Low frequencies are too large for vehicles. They are too large for some homes as well. They travel further in a single cycle than higher frequencies. This helps with output, but only due to reflections, not the box. We take advantage of reflections to help us increase efficiency as close as possible to the original design characteristics. At least… thats what I do for you. So physically we are never designing as efficiently as we can unless we have the room.
Because of the needed room for low frequencies to become coupled, we have the need to make a box as large as it can be. The smaller the design, the lower the efficiency in conventional theory. But again, we can only go so large. Depth is an issue, height is an issue, and width is an issue. Changing the design to match these limitations from manufacturer specs is essential in increasing efficiency. If we all used manufacturer specs… we would all have the same boxes… with maybe 1-2% efficiency at most.
The next limitation is with the electrical circuits (before combined with mechanical and acoustical in the actual circuit of a loudspeaker). I am talking about the circuit that supplies the design; your vehicle, your tube amp, those. In some cases, the electrical cannot supply the design circuit efficiently, so we tend to change resistance to the lowest ohm rating possible. This is not as good for SQ if you want better transience, but still… it is popular among most. So, the wiring can change the design as well with how many volts go into it, and what kind of acoustical output comes out. Making sure you have enough power is essential in the design doing what it is supposed to do. Distortion lowers, and everything works better. Cost can be an internal limitation of power because sometimes we ask for more than we can afford. If I want a design for 8 15s, and I cannot buy enough amps (or upgrades) to cover the power required by the design circuit, I may create clipping or distortion and damage the setup by trying to push it too hard. Making sure you have an amplified input of at least 2X the peak of the design requirements will help you from damaging the setup.
I have had a few times where some will say, “That’s all this will do?” when the design is designed within their limitations. They then up the power or upgrade their electrical and BOOM… there goes their subs. The design is completed around no more than RMS and lowest possible resistance of the amplifier(s) regardless of what you “want” to throw at them. Understanding this, will help you understand what is required to get the most out of it on your end. By designing for the highest possible output and lowest possible resistance, lower output will be expected by not matching the power and resistance as it was designed… if that makes sense.