The following easy to follow steps should help guide you from the initial driver measurement through the final box alignment.
STEP 1: Measure the Driver's Thiele-Small Parameters
Fully measure the Thiele-Small driver parameters using the Q/Fs test followed by either the delta mass or delta compliance test.
The delta compliance method is arguably 'better' when it comes to measuring the remaining Vas parameters but it also requires a
test box of known volume. If you don't have a suitable test box, don't worry; you will have one when you build your vented box!
All of these tests are performed from the main WT Control Window. Follow these links to learn more:
The Q and Fs Test
The Vas Test
STEP 2: Design a Vented Box
Using the Woofer Tester simulator, import the TS parameters and define a suitable box. Many people who read the literature
will wonder if they should follow classical alignments. Strictly speaking, this is a matter of taste where drivers that fall into certain
categories will have certain characteristics. These rules are not strict. Flat response, low group delay, automotive boom bass,
passive and electronic assist, the list goes on forever. Needless to say, you will end up experimenting with a multitude of 'what-if'
box sizes and alignments.
When you have the driver test data loaded (or manually entered) into the WT Simulator, use the up and down arrows to adjust
the values. If you are not familiar with designing a box, simply start with a box volume equal to Vas and a tuning equal to Fms.
Then adjust box size and tuning until you see something you like. Keep in mind that if you manually enter or adjust the TS
parameters, adjusting driver mass will not affect Cms, Rms or BL, but it will affect Fms and Q values and so on.
STEP 3: Build your Box
Build the box. Be sure to take into account the volume taken up by the backside of the driver, vent/port, internal bracing and
anything else that occupies internal volume. It is important that the box walls be stiff and air-tight. It is also far easier to
make a box smaller than it is to make it larger. Simulated and actual box size and tuning are rarely the same. If the box is too
large, use something acoustically inert like additional wood bracing or a block of non-compressible Styrofoam.
STEP 4: Retest Vas using the Delta Compliance Method (Optional)
Retest the driver using the delta compliance method by plugging the vent. Be sure to remove any acoustic damping materials as
this tends to a) add inertial mass making a box appear larger than its physical size and b) lower the overall Q(loss). Keep in mind
that if you plug the port at the front the port volume will add to the box volume.
STEP 5: Collect vented box information
Measure the in-box impedance curve using the 'Vented Box' test. The next step will use this data in an overlay comparison with the
simulator, so it might be helpful to fill in some extra data points to get a smoother curve. This is done by a left mouse click at
a point of interest followed by a right mouse click after the data has settled down to fill in the extra point. The data points you
enter this way do not affect the test results. They simply help to fill in the data curve. You can also set the step ratio to a
small value at the expense of the time it takes to complete the test.
The vented box test only works for vented boxes. If you are designing a closed box system, collect an impedance sweep of the
system using one of the ARBx sweep buttons.
STEP 6: Set up the overlay
Open the 'TS Entry' and 'Data Overlay' windows. In the overlay window, enable the box test data and simulated impedance and
phase using the 'Box' and SimZP buttons. Now, copy the TS test parameters to the simulator using the 'Copy Test-> Sim' button.
The 'Convert Vented Box' data button only works for vented boxes. If you are designing a closed box system, the overlay will be
using an ARBx sweep and you will need to manually adjust box volume.  To simulate a sealed system using a vented box
simulator, set the port tuning to a low value like 0.1Hz.
STEP 7: Align the Test and Simulated Impedance Curves
Finding a simulated box size and tuning that best matches the 'Vented Box' test data can be done manually, or by letting the
software find a 'fit' for the effective box size, tuning and Qloss.  The automatic method is usually pretty close, but with
practice you will begin to see how adjusting the box size, tuning, Qbox, Qport and Qleak affect the positioning and height of
the impedance peaks. This is best done by first adjusting the box size and tuning to get the frequency of the impedance peaks
to line up, followed by adjustments to Qport, Qbox and Qleak for the peak height.
The simulated effective box size and tuning will likely be significantly off. This is because the actual box size and tuning is somewhat
'interactive'. Errors can also be caused by TS parameter errors with the usual error being driver compliance variation from the delta
mass test compressing the suspension. Interestingly, this kind of error mostly cancels as the effective box size is derived from the
overall springiness of the driver and air suspension. If this is still a concern, go back and re-measure the driver using the box you
now have and the Vas delta compliance method.
Be sure to use the Rem/Xem simulation mode. This option will provide the best possible simulation. The 'Le' and 'Simple' mode options are for
comparison against previous WT models and non-WT simulation programs.
STEP 8: Examine the System, Driver or Port Response
When the simulated and box test data impedances are a close match, turn off the impedance and phase plots and enable the
STEP 9: Make Physical Adjustments to the Box
If necessary, you may need to make physical adjustments to your box. Hopefully, the box was built slightly larger than the
original simulation predicted. In this case, add some internal bracing or another acoustically inert material. Anything that
is non-compressible will work. Retest and repeat from Step 5 as needed.
When you make these adjustments keep in mind that you are making relative adjustments. For example, if you wantto decrease
the box tuning
by 10%, dont simply change the new length to what is shown in the simulation. Rather, you need to increase the
original physical length by 10%.
Congratulations! You have just built a speaker. Let's look at the measurement results next.
The first image below shows what the impedance comparison should look like. The second image shows the simulated driver
response overlayed with the actual close microphone driver response (ECM8000 with Woofer Tester Pro microphone input).
The port for this box is physically on the backside allowing the driver response to be measured without too much interference
from the port. An overlay of the measured port response (also in the WOO file) is of similar quality. This WooFile contains
the driver's TS parameters (the Easy Nickel delta mass Vas method was used) as well as microphone measurements of the
driver and port (ARB1 and ARB2).
- If you modify the simulated driver TS data, the original TS test data will be in the test buffers. Test data is imported into the
simulator using the 'Copy Test->Sim' button.
- Automatic extraction of the effective box size and tuning from the vented box data is accomplished by clicking the
'Cvrt Vbox->Sim' button.
- Disable or enble the various impedane and response views. Simulation quality is best when Rem/Xem modeling is enabled
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