Originally Posted by mark.hayes0338
Listening to a normal song made the bass seem a little lower than I'm used to
, but was much better than yesterday. A major thanks to you and to everyone else in here that helped! After a few days I will come back and report any new findings.
In fact, that is normal. But what you should notice is more detail and image is more focused.
There are some discussion of TR in this thread. Now Josh's databass has a test called compression. Therefore everyone thinks the only bad things that a sub can have in addition to distortion is compression, meaning lost in output. Can the opposite of compression take place in a sub with poor non-linearity? You bet. First think about the transistor in the amp. A lot of them them follow square curve. A square curve means the output increases more lineary than the input. So at 1 volt, the output is 1volt. But when the input increases to 2, the output increases to 4. That is what we call superlinear. The higher order it is, the more rapid it increases with input level. For 3 harmonic distortion, it follows x^3 polynomial. So at 1 volt, the output is 1 volt and at 2 volt inputs, the output increases to 8 volt . What I described here is just a general idea. In reality, the amount of x^2 and x^3 polynomials depends on the coefficients. For instance, in our case the coefficient can be 0.05 for the x^3 case, and at 2 volt inputs, the real output is 2volts + 0.05x8volts to 2.4volts. But the general trend is true, the higher the order of distortion, the more rapid increase the output exhibits from normal level to loud level.
Now that is just the amp. The driver can also exhibit similar behavior, but through a different mechanism. When we talk about driver, we cannot leave out the so-called BL curve. BL value is also called "Force factor". When drivers get into nonlinearity at excursion extremes, the BL force factor value drops significantly compared to BL value at the rest position. So our intuition is that when force factor value drops, we should expect a drop in output. That is mostly true except around the frequency range that driver's impedance is moderately higher than DCR. For sealed subs, that is between 15hz to 30hz (and much higher for PA subs). For ported subs, that is from 5 hz to 30hz excluding the port tuning frequency. When that happens, the low BL value actually makes the cone move faster, sort of like escape, or out-of-control. So the distortion mechanism in the driver is even more complex than that in the amplifiers because in the latter, the characterisitc seems to be frequency independent whereas in drivers, compression and expansion can happen at the same time, but at different frequencies. Lower BL value also contributes to high Q or more time domain ringing.
So in short, it may be a shock that how much less the bass is when you listen to our subs. But in fact, the bass is more coherent as you hear more and more of the CD you are familiar with. It can reproduce detail that you may not have noticed in other subs.