Using WT3 to Evaluate a Closed Box Loudspeaker

A closed box type of loudspeaker system is characterized by a resonance frequency F(sc), an electrical Q value Q(ec), a mechanical Q value Q(mc) and a total Q value Q(tc). Just as you can use WT3 to measure a driver's parameters you can also use WT3 to measure the corresponding parameters of a closed box loudspeaker system. The frequency response of a closed box speaker is the same as that of a purely electrical second order high-pass filter with the same electrical resonance frequency and Q as the loudspeaker's electro-acoustic resonance and Q. While the resonance frequency determines the low frequency bandwidth of the system, the Q(tc) determines the shape of the high-pass response in the corner region with Q = .707 corresponding to a maximally flat Butterworth response.

The impedance response of a closed box loudspeaker has a single well defined peak at the system's primary resonance frequency. Compared to the same driver in free air, the resonance frequency will always be seen to increase when a driver is mounted on a closed box enclosure. The larger the enclosure the less the resonance frequency is increased. The same is also true for the driver's Q(ts) parameter versus the closed box system's Q(tc). The Q(tc) for the driver in an infinitely large enclosure would equal the Q(ts) of the driver. As the enclosure size is reduced the Q(tc) of the closed box system increases. So a given closed box speaker will always have F(sc) and Q(tc) values somewhat higher than the driver's corresponding free air parameters F(s) and Q(ts).

Before starting, make sure the WT3 unit has been calibrated and has stabilized for at least 90 seconds.

Measure the system impedance as follows:

•Launch the WT3 software and make sure the volume is at maximum.

•Make sure that the speaker system is not connected to any other equipment and then connect the test leads of the WT3 unit to the speaker under test.

•Click the "Measure Free Air Parameters" button at the left side of the WT3 screen.

•You should hear the sweep from the speaker, the impedance is plotted and the parameters are displayed.

•The system's closed box resonance frequency, (F(sc) is displayed in the F(s) data field.

•The system's closed box total Q, Q(tc) is displayed in the Q(ts) field.

•The system's closed box mechanical Q, Q(mc) is displayed in the Q(ms) field.

•The system's closed box electrical Q, Q(ec) is displayed in the Q(es) field.

•The DC resistance of the system is displayed in the R(e) field. Ignore all other parameters.

•Repeat the measurement to confirm the result. Repeated measurements should be in good agreement.

WT3 specifications

The Dayton WT3 is a sophisticated and highly regarded tool in the field of audio measurement and analysis, particularly known for its precision in loudspeaker testing. This comprehensive device integrates several advanced features and technologies, making it an essential choice for audio professionals, engineers, and hobbyists alike.

One of the standout characteristics of the Dayton WT3 is its dual-channel capability, allowing users to conduct simultaneous measurements of two different loudspeakers. This feature is particularly useful in stereo systems where matching drivers is essential. The WT3 utilizes a high-resolution analog-to-digital converter (ADC) that ensures accurate and detailed frequency response measurements, providing users with the data they need to refine and optimize their audio setups.

The WT3 is equipped with a user-friendly interface that simplifies the measurement process. Its software is intuitive and runs on Windows, which means that users can easily navigate through various options to configure tests and analyze results. The inclusion of a built-in microphone makes it possible to perform room acoustics measurements, further enhancing its versatility.

Another key technology integrated into the Dayton WT3 is its frequency sweep capability. By generating continuous sine wave sweeps across a wide frequency range, the WT3 can analyze the response of loudspeakers in real-time. This allows for identifying resonances, distortion, and other critical parameters that affect sound quality.

The WT3 also features a range of measurement modes, including impedance measurements, which can be invaluable for understanding how a loudspeaker behaves across different frequencies. This data is displayed in easy-to-read graphs and charts, facilitating a straightforward interpretation of results.

Moreover, the Dayton WT3 utilizes advanced signal processing algorithms that help in reducing noise and other unwanted artifacts that can skew measurements. The device's accurate phase response measurement capability further distinguishes it from competitors, providing essential data for crossover design and speaker alignment.

In summary, the Dayton WT3 combines advanced measurement technology with an intuitive user experience, making it an essential tool for those seeking precise loudspeaker performance insights. Its features and capabilities position it as a valuable asset for both professional audio engineers and enthusiasts dedicated to achieving the best possible sound quality. Whether for designing new speakers or optimizing existing setups, the WT3 delivers reliable performance and accuracy.