How We Measure & Compare
We start with a brief look at the hardware used, and then proceed to a description of our measurements and measurement rooms:
|Test System & Hardware|
|Microphones||NTI Audio M2211 (with calibration file, low cut at 50 Hz)|
Shure Beta 181/C (artificial head, with calibration file)
|Hardware||Steinberg UR12 (with phantom power for microphones)|
Creative X7 (analog output for active systems or as an amplifier for passive loudspeakers)
Passive PC and monitor
|Software||Arta, Smaart v.7|
|Environmental||Custom-made proprietary measurement chamber, 3.5 x 1.8 x 2.2m (L x D x H)|
|Measurements||Near-field (0-12cm, primarily Bluetooth speakers)|
Approximated free-field measurement (1m)
15°/25° rotated, side measurement
Measurement using artificial head for headphones and headsets
Our custom-made chamber allows us to measure everything from graphics cards, loudspeakers, and headphones, to computer cases and fans. Its implementation is quite unusual: we built a room inside of a room. If you're imagining a large freight elevator, then you're on the right track. The cabin weighs just under four tons, is quite spacious, and torsionally rigid. It has a double-walled design and is filled with polyurethane foam. The only direct contact to the outside world is where it rests on dampeners. Since the doors are not quite as good as the other walls, despite their thick inner cladding, we built an additional frame on rollers filled with special foam that completely and hermetically seals the opening, shielding it from the outside world.
In addition, we lavishly clad this room in several layers. The bottom layer consists of a dense foam applied to the ceilings, walls, doors, and flooring. On top of that, we used a special pyramid-shaped foam on every surface except the floor. Down there, you'll find one layer of very soft grid plates, topped by a thick layer of felt.
Another room right next to our measuring chamber allows us to control all of our tests externally. Thanks to a special cable duct in the measuring room, we have a wide range of connection options at our disposal. This includes a microphone cable, an additional stereo NF cable, speaker cable, HDMI and USB, as well as an optional 230V connection for active speaker systems.
Headphone And Headset Tests: What Is An Artificial Head?
Evaluating headphones and headsets requires a slightly more complex environment than loudspeakers. The positioning of the earpiece on the auricle, how well the pieces close around the ear, and the distance between sound source and microphone (and their directional characteristics) play a major role.
To get a reasonably reliable measurement is quite complicated. That's why, for stereo recordings, we use a homemade artificial head that imitates the properties of a human. Our microphones are placed inside the auricles.
More specifically, we're using two Shure Beta 181/C mics in a wax-like plastic cast head. Their linear frequency response is very convincing when recording indoor sound, even though these small microphones were originally intended for pure instrument recordings.
A particularly beneficial property is their distortion-free recording of high levels, which is just what we need for headsets. The necessary corrections are provided by a calibration profile that we prepared especially for this purpose.
We would like to point out that our measurements of loudspeakers, headphones, and headsets are, as a result of our technical capabilities, merely semi-professional.
While the results are fully sufficient for an objective assessment of our test objects, they cannot match data generated by highly professional (and much more expensive) equipment that manufacturers and test laboratories use. However, as a general guideline, they should certainly be quite useful.
Music For Evaluating Frequency Ranges, Precision, And Spatial Representation
Instead of hi-fi jargon like thundering bass, delicate strings, and huge sound stage, we're focusing on a theoretical introduction to genre-relevant frequency ranges and the basics of spatial hearing.
|Analysis||Title / Source|
|Lowest/Low Bass (Range)||J.S. Bach - Toccata and Fugue in D Minor (FLAC, vinyl rip)|
Tchaikovsky - Festival Overture in E♭ Major (FLAC, vinyl rip)
Avatar (Blu-ray, effect track)
|Bass Quality||Till Brönner - It Never Entered My Mind (CD)|
Blue Man Group - The Complex (CD)
Kid Cudi - Day and Night (The Widdler's Dubstep Remix, CD)
|Spatial Resolution||Clapton Unplugged (CD)|
Dire Straits - Brothers in Arms (CD)
Gershwin - Concerto in F (FLAC, vinyl rip)
|Precision Of Instruments And Voices||Brahms -String Quartet No.1, Op.51 No.1 (FLAC, vinyl rip)|
Bach - Christmas Oratorio Cantata VI (Thomaner-Chor, vinyl rip)
Gershwin - Concerto in F (FLAC, vinyl rip)
|Dynamics and level stability:||Carl Orff - Carmina Burana (CD)|
Mike Oldfield - Tubular Bells III (FLAC, vinyl rip)
Maurice Ravel - Boléro (FLAC, vinyl rip)
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