Condition 1: underway!

We have begun testing subjects for our first of our test conditions. Here's a brief roundup of the experimental conditions as well as the setup.

Our final systems used for condition 1 are as follows:

The expensive system:
Dynavector DRT XV-1s (moving-coil) Cartridge
VPI HR-X Turntable w/ JMW 12.6 Memorial Tonearm
Kimber Kable 0.5 m KCAG interconnects (from table to preamp)
Manley Steelhead preamplifier (gain setting = 55 dB, load = 50 ohms, load caps = 0 pF)
Kimber Kable 0.5 m KCAG interconnects (from preamp to A-D converter)

The mid-range system:
Ortofon Kontrapunkt A (moving-coil) Cartridge
VPI Aries 2
Kimber Kable Tonik 2.0 m
Pass Labs XONO preamplifier (gain = standard setting (i.e., non-high-output), load = 47 ohms, load caps = off)
Kimber Kable 0.5 m PBJ interconnects (from preamp to A-D converter)

Digitization was performed via a PrismSound ADA-8XR converter (settings: peak input [0 dBFS]=+11.5 dBu, 24-bit, 96kHz, no processing). Audio was recorded in the Logic 7 recording environment also set to 24-bit and 96kHz. Audio clips (5-8 sec, depending on musical phrasing) were prepared using Audacity, and great care was taken to cut the clips as close to each other, and all clips of the same musical sample were exactly the same length, without pops. Each vinyl was cleaned using a VPI HW-17 cleaning machine.

The clips used for the test were taken from the following tracks:

1. Miles Davis - Blue in Green (Kind of Blue)
2. Santana - Oya Como Va (Abraxis)
3. Steely Dan - Aja (Aja)
4. Holst - Saturn (The Planets)
5. Pink Floyd - The Great Gig in the Sky (Dark Side of the Moon)

Each record was played twice on both systems (resulting in 4 .aiff files for each record), alternating between systems, in counterbalanced order with at least 5 hours between recordings. During each take, the entire track was recorded; once all 4 takes were completed for a given record, musical phrases of approximately 5 seconds that were not affected by recording artifacts were identified. Only phrases that were free of recording artifacts on all 4 takes were extracted for use as stimuli.

The perceptual study took place at the Critical Listening Laboratory at the Centre for Interdisciplinary Research in Music, Media, and Technology (CIRMMT), McGill University. This is an ITU standard room providing high-quality, controlled listening conditions. The audio recordings were played back through a MAX/MSP patch on a Mac Pro computer. Digital audio (24-bit/96kHz) was sent via TOSLINK to a Grace m906, to a stereo pair of Wilson Watt/Puppy loudspeakers powered via Bryston 14B amp. Below are some images of the Critical Listening Lab and the connections used for this experiment. Here is the view from outside the listening lab:


The front and rear of the Grace m906. Digital TOSLINK enters the Grace m906, and analog audio is output to the Bryston.

The output from the Grace m906 enters the rear of the Bryston 14B:


the output of the Bryston is sent through this patch bay:


and then into the listening laboratory next door:


where they are connected to the Watt loudspeakers:

.

Procedure:

An A/B preference test was employed to determine whether participants were able to differentiate between excerpts recorded on the mid-range and on the high-range phonograph playback systems. The preference test comprises 4 blocks of 12 trials each; an additional training block of 12 trials, during which participants are acquainted with the user interface, precedes the test. The excerpts within each trial were recorded either on the two different phonograph playback systems, or twice on the same system. Each block corresponds to one of the LPs employed in the study (see table 2). Block order was counterbalanced between participants, and trial order was randomized (double- blind) within each block, to counteract potential ordering effects. A short break of 2 minutes was taken between each block.
During each trial, participants were exposed to two excerpts. A user interface featuring two boxes, labelled ‘A’ and ‘B’, was used to indicate the currently playing excerpt, by placing a cross inside the respective box. Participants first listened to the entirety of ‘A’, followed by the entirety of ‘B’. Participants then had the opportunity to repeat playback of either excerpt, switch in-place between excerpts during playback, and to pause and resume playback. Once ready, participants were asked to indicate their preferred excerpt. The next trial was triggered as soon as a choice was made.

Participants were asked for their preference, rather than whether they could tell a difference between the excerpts. Participants were instructed to choose arbitrarily between ‘A’ and ‘B’ if no difference could be identified. This strategy was chosen to avoid biasing uncertain participants towards saying ‘no’ to differentiability, even if they could have told the difference subconsciously; subconsciously-informed choices are recorded, and truly arbitrary choices are negated in aggregate due to the randomized, counterbalanced presentation of extracts.

After the listening portion of the study, participants were asked to complete a questionnaire. This questionnaire recorded basic demographic information; the participants’ level of studio experience, musical experience, and ear training; their familiarity with the stimuli employed in the study (7-point Likert scale, ranging from ‘not familiar’ to ‘very familiar’—see table 2); qualitative de- scriptions of the perceived differences between the excerpts, for individual blocks and in general (free text entry); a quantitative indication of perceived difficulty in differentiating between the excerpts (7-point Likert scale, ranging from ‘very easy’ to ‘very difficult’) ; as well as information on the participants’ listening habits, including their preferred musical genres and home listening set-up.

Results from the test will be posted as they become available.