Using the ACI Subwoofer Test CD:
Instructions for
Using the Test CD
Download
Subwoofer Excel Worksheet
Download
Subwoofer PDF Worksheet for those without Excel
* If asked for password just click cancel.*
- By
Ear: Use
the test tones, (most people prefer the sinewaves), to try
to achieve the smoothest system response. Note, you will
find very different results by just moving your head. This
is because of the very strong effects that room modes have
on low frequencies.
- Using
the Radio Shack SPL meter and Excel spreadsheet: This
method is relatively easy, inexpensive, and quite
accurate. You must have Excel on your computer to be able
to load and use the spreadsheet. It can be rather time
consuming compared to methods four or five.
- Using
the Radio Shack SPL meter and hand plotted graphs: Very
similar to #2 but you'll have to do a little math when
hand plotting.
- Using
a test system such as ETF, CLIO or MLSSA: If
you have this type of equipment you can run the
measurements quickly and accurately. Usually the most
expensive option. Most of these instruments are extremely
powerful and can have a relatively steep learning curve.
Separate measurement microphone and possibly microphone
pre-amp will also be required.
- Using
a RTA (Real Time Analyzer): This
is probably the fastest method as you can see the results
of your adjustments on-screen, in real time. RTAs used to
be quite expensive. Computers with soundcards have
drastically changed that!
An excellent RTA can be found at: www.trueaudio.com.
Separate measurement microphone and possibly a
microphone pre-amp will also be required.
The Steps
- We
provide both sine waves and warble tones. Many people
prefer sine waves for listening tests and warble tones
for using the SPL meter.
- Insert
the test disc in your CD player. Position the SPL meter
at head height in the primary listening position. The
meter should be aimed toward the speakers. A camera
tripod can be used as the SPL meter has ¼ -20"
threaded insert on the bottom.
- Set
the SPL meter to "C" weighting, and response
to slow.
- Start
with the system volume turned down. Play a 60Hz warble
tone and adjust the subwoofer volume to read 70dB on the
SPL meter.
- Download
the "Subwoofer
One" MS Excel worksheet.
- Play
the warble to tracks, read the measurements, and record
in the spreadsheet. The spreadsheet will make the
calculations and show you a graph.
- Using
the graph, you can now use the controls on your sub or
experiment with placement to get the smoothest possible
response.
*
If you don't have Excel, you can print the other PDF Subwoofer
Worksheet out and do manual calculations. Your steps
will be the same as above. However, for steps five and six you
will need to manually plot your graph. Be sure to add or
subtract the required correction for the meter.
Using Alternate Measurement Systems
Some of you may own or have access to a
RTA such as the 1/3 octave unit manufactured by Audio Control.
This type of unit will allow you to quickly see the changes as
you make adjustments. The disadvantage is that 1/3 octave
resolution is rather marginal. We have found 1/6 octave to be
ideal for optimizing systems. These types of analyzers are
available as software based systems using your computer sound
card. Another excellent option is the ETF system, which takes
quick, high-resolution measurements of not only frequency, but
time as well.
Software based analyzers are inexpensive,
(in some cases free), and very powerful. That power comes with
a price. The learning curve to setup and use some of these
programs can be rather steep. Other factors to keep in mind;
1) Most of the software programs have certain requirements for
the computer hardware and the soundcard used. 2) Separate
measurement microphone and possibly microphone pre-amp will be
required for any software based RTA or Analyzer.
Additional Resources:
ETF: http://www.etfacoustic.com/
Trueaudio: http://www.trueaudio.com
Go to Main ACI
Subwoofer Setup
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