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Audio.TST October 2008: New website & polar plots on 2700

Created 30 Oct 2008

Notes from the Test Bench

By Bruce Hofer, Chairman & Co-Founder, Audio Precision

Hello

Well, AES was a tremendous success. We saw a record number of visitors to our booth, and at times it was an effort to even say hello to everyone. The introduction of the new APx521 and APx526 four channel analyzers was very well received, and we were happy to see quite a large contingent of automotive engineers in the audience nodding their heads at the auto-friendly features we've included.

Up next is Electronica, a German show focused on components and automotive starting November 11th. This will be the first time for AP at the show, but we have very high expectations. Look for AP in hall A1, stand 364. Our marketing department has guest passes if anyone needs them for the show.

We will introduce yet another product at Electronica (that's six this year!), this one related to new digital connectivity we're adding to APx. We'll send out a special announcement from Electronica on November 11th, so watch your inboxes.

Best Wishes,

Bruce

Output: Tech tips and new applications from AP

AP launches new solution-focused website at ap.com

AP is proud to announce the launch of a revamped website at http://ap.com.

The new website is divided into a Solutions Center, Product Catalog, Audio Resource Library, Knowledge Base, and Downloads Center. This approach makes AP’s audio test & measurement expertise much more accessible, with whitepapers, tutorials, Technotes and software resources available for users at every technical level.

The new Solutions Center looks at common test challenges and testing tips for a range of devices from consumer receivers with HDMI to multichannel mixing consoles. Popular downloads include the Introduction to the Six Basic Audio Measurements, Measurement Techniques for Digital Audio, and the Audio Measurement Handbook. New to the site is the AP Glossary of Audio Terms.

And it looks nicer too...

The new website

Sound Advice: Audio Test Q&A

Creating Polar Plots from AP2700 Data

AP's Technical writer Adam Liberman looks at techniques to create polar plots from data created with a 2700 Series audio analyzer.

When measuring microphones and speakers, it is often desirable to take level measurements at different angles and display the results as a polar plot. A polar plot displays the sensitivity (microphone) or loudness (speaker) of a device at the front, sides, back, and at points in-between. Such plots are very useful in visualizing the directionality of a device. Even omni-directional devices will show some directionality, due to their own physical presence blocking sound from the rear. When multiple data-sets at different frequencies are overlaid, say at 100 Hz, 1 kHz, and 10 kHz, the plot also shows how frequency response varies with angle.

Generating the data
Using AP Basic, you can automate the exporting and graph creation process. In addition, you can automate the data collection process, which will be necessary as the AP2700 Control Software can not natively rotate a turntable to collect the polar data. We have provided an AP2700 macro below that you can incorporate into your own macro to rotate an Origin ET1 or ET2 turntable. These turntables require a parallel port for control.

Graphing the results
Although the AP2700 Control Software does not include polar plotting, you can export measurement data to the plotting program of your choice. Here, we’ll demonstrate exporting to Excel.

First, we’ll collect data by running our test.
Then, we’ll choose Export > Excel from the File menu.This exports an Excel file, with the data in columns.
Then, we’ll open the file from inside Excel and add a Radar chart, specifying the appropriate columns for the data.

The result is very close to a polar plot, but Excel’s radar plot has discrete points connected by lines, instead of a continuous curve. The Related Download link below includes an example Excel file that demonstrates the process.

The other export option is ASCII text. This time, select Export > ASCII Data from the File menu. This creates a comma separated text file, suitable for importing into a wide variety of plotting programs, both free and commercial. You may need to change the .adx file extension to .txt or .csv for the file to be recognized.