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The New MDT-4000 Turntable

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There’s a new turntable in town!

We’re excited to launch the Portland Tool and Die MDT-4000 Turntable, exclusively available from Listen. Designed specifically for audio measurements, it packs a host of usability and safety features, along with high precision and low maintenance in a compact and lightweight package. Features include:

High Precision: The MDT-4000 offers a resolution of 0.1°, one of the most accurate on the market.

Low maintenance: A maintenance-free worm drive requires no lubrication, making this turntable maintenance-free, an advantage when it is remotely located, for example in an anechoic chamber

Easy Set-Up and Operation: The turntable has a built in level, along with 4 adjustable feet, making it quick to perfectly level and align equipment. Clearly visible degree markings provide quick visual confirmation of position and make it easy to align accessories with the turntable. Mounting holes at 3”, 9” and 15” diameter provide a variety of mounting options, and a center cable pass-through prevents tangling. The turntable retains position memory across power cycles, so the display remains synchronized with the actual position, even when the turntable is turned off.

Flexible control options: 4 control options offer ultimate flexibility:

  • USB – easy control for short distances
  • RS232 for longer distances  and backwards compatibility with LT360
  • RestAPI provides long distance communication via LAN, enabling control via a webpage using a laptop or smartphone and enabling custom control applications to be written
  • Full control from within SoundCheck (naturally!)

Packed with safety features: With emergency stop buttons on the front panel and in the software, plus an optional remote button for when the turntable is not within reach, your valuable products and instrumentation are protected. An automatic stall detection mechanism identifies if an obstruction is preventing the turntable from reaching its target position and both warns the user and stops the drive to prevent damage to equipment.

Quiet operation: Silent at rest, and low-noise when rotating, it is ideal for audio applications. Variable torque enables slower rotation speeds to be used for quieter operation when measuring during rotation.

Right-sized: Supports weights of up to 100kg in either compression or inverted orientation, making it suitable for the majority of audio applications. Weighing in at just 12kg, it is easy for one person to move around the laboratory.

Competitively priced: The MDT-4000 is competitively priced with other turntables, and considerably less expensive than others offering the same advanced functionality.

Full specifications coming soon!

Contact Sales@listeninc.com for a quotation or more information.

Polar Plot (Linear X Turntable) Loudspeaker Sequence

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This sequence measures the polar response of a loudspeaker in both the vertical and horizontal dimensions. It is designed to work with the Linear X turntable, and has all the necessary commands to automatically rotate it via RS-232. The sequence uses a log sweep stimulus with the Time Selective Response algorithm so that the measurements can be run in a non-anechoic environment. Note that the time window needs to be adapted to the user’s measurement space. The sequence plays the stimulus and measures at 10 degree increments from 0 to 180 degrees. This process is repeated with the speaker positioned horizontally. The two results are mirrored to display full 360 degree polar plots for each axis. A directivity index curve is also calculated for each axis and is displayed at the end of the test.

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Microphone Polar Plot Substitution Method Using Outline ET250-3D

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This sequence measures the directional response of a microphone and graphs the result as a polar plot. A log sweep stimulus is played from 100 Hz to 10 kHz at each angular increment, and the acquired waveform is analyzed using the Time Selective Response algorithm. This method allows the test to be performed in a non-anechoic environment by placing a window around the direct signal, eliminating the influence of reflections. Commands are sent automatically to the Outline ET250-3D turntable via an ethernet connection, instructing it to move in 10 degree increments after each measurement. The sequence measures the response every 10 degrees from 0 to 180 and mirrors the polar image, which simulates a full 360 degree polar and saves test time. The response at each angular increment is compared against the on-axis response to create a normalized curve. This removes the influence of the device’s frequency response and sensitivity, such that the polar plot only shows the directional response. The final display also contains a graph of the directivity index in decibels versus frequency.

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