Linearteam WinISD Pro
This graph shows gain in dB related to driver's limit efficiency n0. Which it theoretically reaches at infinite frequency. This is the basic graph, which is needed most.
SPL graph shows Sound Pressure Level at specified distance at specified powerlevel, radiated to half(2pi) space. To get the full-space value, subtract 6 dB from the reading. Because driver's efficiency is related to ambient conditions, changing for example the project's temperature, will change the calculated SPL level.
Maximum SPL graph is a combination of SPL and maximum power graphs. It tells how loud particular design is able to play, considering Xmax and Pe restrictions. If calculated power to reach Xmax is greater than Pe, then Pe is taken as input power to the driver. With this, you can easily visualize potential of particular design. Please note that it doesn't apply to room or in-car environment, what could change things quite a bit. It is useful as an comparison tool, e.g. comparing same driver in closed or vented box. See also Maximum Power.
Phase shows the phase difference between the electrical input signal and acoustic output signal. See following illustration:
Here, the blue plot is the zero-phase signal, the reference. You always need a reference to
define the phase shift. Now, if we add phase shift of +45 degrees, we get the graph plotted
with green color. So it is kind of "ahead" of the input signal. EE people say that it has
"phase lead of 45 degrees". On the other hand, if we make phase shift negative, we get
that red plot. There, the phase shift is -90 degrees. So it is said that there is a "phase
lag of 90 degrees".
Now, you'll probably wondering how this relates to phase plot WinISD is showing to you. You
can take the input signal which your amplifier will feed into your speaker to be that blue
reference. Phase graph tells you how much phase shift in degrees there will be between
outputted acoustic signal and input signal.
Group delay describes how long spectrally infitesimally narrow sine burst signal takes to travel through speaker's acoustic "filter". The flatter the group delay, the better. The value itself is not a concern, other that if delay becomes too large, then it might be difficult to match the design to other speaker's which might have less group delay. Large groupdelay variations usually means large ringing when transient signals are applied to the system. Mathematically it is the derivative of negative phase versus frequency in radians/sec. So when phase changes linearly versus frequency, then the group delay has a constant value. If that seems to hard to think, think it as follows: Take a number of people, where each individual represents a particular frequency. Now, send them simultaneously running to specific target. If they all reach the target at same time, then group delay is flat. They all take same time to reach the goal. Now, if some of those are in worse shape than others, they'll arrive later than others. Now, the group delay is not constant, and different frequencies will arrive at different times. That's group delay.If you are wondering why the group delay of vented box is very different from WinISD version 0.43 and below, the reason is that it calculated it wrong. Current versions produce correct results.
Cone excursion shows how much driver cone moves with sinusoidal excitation at chosen powerlevel. The powerlevel is controlled in "plot"-tab. The power applied can be related to excitation voltage with following relation: Eg=sqrt(P·Re), or P=Eg²/Re where Eg is the RMS voltage applied to driver's terminals, P is the input power in watts and Re is the DC resistance of the voice coil. Please note that there is few different ways to express this value. WinISD can be configured to show RMS, Peak, Peak-to-peak (p-p) values of the cone excursion. RMS value is defined just as RMS value of any sine waveform. Peak value is the difference between zero and the maximum value of sinusoidal waveform. Peak-to-peak is twice the peak value, i.e. difference between minimum and maximum point of waveform. The peak value is perhaps a most practical expression, because driver parameter Xmax indicates how much cone can be deflected from it's rest position linearly, in either direction.
If you want to maximize power handling of any box, then adjust the box parameters so that cone excursion is kept at minimum value possible. Of course the transfer function magnitude graph should be taken into consideration also. In closed box, the minimum excursion is obtained, when enclosure is as small as possible. Same basically applies to vented box, but there is a local minimum at port tuning frequency.
When comparing graphs between programs, please note that many programs give the RMS excursion which is "wrong", in my opinion. I have seen some programs, where the calculated excursion is RMS value, and limit is shown as peak. That gives over-optimistic power handling impression. Please also note that this graph doesn't take nonlinearities into consideration. But it let's you see when the nonlinearities are becoming too great.
Air velocity graph shows how fast air mass travels in port. In order to keep chuffing noise low, you should limit the peak velocity at 5% of velocity of sound, or about 17 m/s. Like the cone excursion graph, the desired powerlevel is set also by same watts setting. Note that if air velocity peaks exceeds previously mentioned level. This graph can also be configured to show RMS, peak or peak-to-peak value. See the cone excursion graph explanation for RMS, peak and peak-to-peak values.
This graph shows n0 (the driver reference efficiency) relative magnitude output of the front or rear port. In conventional vented box, this graph shows relative sound pressure contribution of the vent.
Maximum power indicates, what is the maximum powerhandling of the speaker at each frequency. It shows either the Pe, which is maximum electrical input power based on thermal power handling. Or if it is less, then it shows, how much power is needed to drive the cone to maximum excursion Xmax. Again, you can obtain the required drive voltage by equation Eg=sqrt(P·Re), where the Eg is RMS terminal input voltage of the driver, P is the input power and Re is DC resistance of the driver voice coil. See also MaxSPL.
Impedance graph shows, what kind of impedance load the amplifier will see. The impedance shown is the impedance of each driver, if there is many of them or there is an isobarik configuration. In LspCAD terms, drivers have "Separate Sources". The lower the reading, then higher the load on the amplifier. Impedance graphs shows actually the modulus of the complex impedance and phase angle (impedance phase) graph shows whether the load is resistive (phase about 0 degrees), inductive (phase positive) or capacitive (phase negative). Reactive load doesn't actually dissipate any power, but instead of dissipating it, it returns it to driving amplifier. In classic linear amplifier, this power is wasted. D-class amplifiers utilize this and return this energy to the power supply. High capacitive load is difficult for any feedbacked amplifier, because it eats the phase margin of the amplifier and may cause it to begin oscillating. This impedance gives only steady-state impedance for sinusoidal signal. For more complex input signal, the current drawn from the amplifier may be greater than calculated with this graph, because of energy storage of the impedance, although this may be very rare with normal audio signals. There is an AES paper about this written by Matti Otala and Pertti Huttunen.