pmr@drufl.UUCP (12/05/83)
In reaction to the speaker wire article in "Stereo Review," the
Denver AT&T ISL Audio Club is organizing an evaluation of its own
to find out if people can hear differences in wires. Details of
this proposed speaker wire evaluation are outlined below. If
anyone has any valid criticism about this demo to improve its
effectiveness, please respond before Friday, December 9.
As they say, thanks in advance...
Phil Rastocny, AT&T Information Systems Laboratories, Denver, CO,
drufl!pmr
ps. I am also open to any recommendations for programme material.
The evaluation will be given at a regularly scheduled Club meeting
where 30 or 40 people are planning to attend. The room is an average
arranged classroom with 10' ceiling and 30'x45' floor dimensions.
The audience will be arranged in chairs in the center of the room
and the rear of the equipment will not be visible from any angle in
the audience. Loudspeakers will be pre-positioned for optimum
soundstaging at most of the room positions.
TALKING BETWEEN PEOPLE DURING THE EVALUATION IS DISCOURAGED. We
are interrested in your PERSONAL reaction and not a GROUP consensus.
Equipment used will be:
Integrated Amp: NAD 3140, modified power supply wiring and
speaker-selector switch removed from circuit (output
transistors hard-wired to terminals).
Turntable: Denon DP-30L
Cartridge: Boston Acoustics MC-1E
Cassette Deck: Nakamichi BK-2
Interconnect Cables: Monster Inter-link
Loudspeakers: Boston Acoustics A70s, AR5s, and Jensen 200As.
There will be six wires tested. They are:
#18 zip cord [$.10/ft], Rdc= 250 E-3 ohms, L= 3.5 E-6 Henries,
C= 350 E-12 Farads,
the Audio Club's home-made stranded 4-wire [$.85/ft], Rdc= 44
E-3 ohms, L= 1.5 E-6 Henries, C= 1200 E-12 Farads,
Kimber Cable woven braid [$1/ft], Rdc= 92 E-3 ohms, L= 1.5 E-6
Henries, C= 970 E-12 Farads,
Saxton #10 multi-strand 2-wire [$2/ft], Rdc= 17.6 E-3 ohms, L=
7.5 E-6 Henries, C= 15-20 E-12 Farads - depending on wire
placement,
Monster Cable "Power Line" multi-strand 4-wire [$2.50/ft],
Rdc= 24 E-3 ohms, L= 1.5 E-6 Henries, C= 1020 E-12 Farads, and
a home-made 4-wire Litz [$3.25/ft]. Rdc= 40 E-3 ohms,
L= 1.5 E-3 Henries, C= 1400 E-12 Farads.
Rdc was found by doubling the value for one conductor (+) as measured
with an HP Milliohmeter. All measurements were taken at 1KHz. All
wires are 15' long except for the Litz which are 25' long. All wires
are phased with red and black pin-type terminators.
Contact resistance of the push-button connectors is 3.0 E-3 ohms each
(12.0 E-3 ohms per + and - pair). The best switches available have
typical contact resistances of 20 E-3 ohms per contact (80 E-3 ohms per
speaker circuit) and cannot be switches "hot". Switches will not be
used since Rdc in some cases is far less than the total contact
resistance of the speaker circuit.
-----------------------------------------------
1. The test will be double blind. There will be three
volunteers changing the speaker wires and these volunteers
will not participate in the evaluation. An audience
representative (moderator) will interface the audience to
the volunteers.
2. The wires will all be bundled together behind the amp and
speakers out of sight of the audience. Blank tags will be
attached to each wire at both ends.
3. The selection of wire numbering will commence as follows.
The moderator will pull folded pieces of paper out of a hat
and hand them to a volunteer. These pieces of paper will
have the brand name of a wire written on them. The first
piece drawn will be wire #A, the second will be #B, etc. The
numbers will then be transferred to the paper and the blank
tags on the wires by the volunteers. The papers will then be
placed back into the hat after all wires are numbered.
4. A comparison will then commence in order, from the first to
the last wire. Using the same song for each wire. About
every 30 seconds, or at the audience's request, the
volunteers will change to the next wire and continue doing so
until the song ends.
5. Each wire will then be evaluated for a longer period of time.
Participants will be asked to rate the wires from a set of
questions regarding any observed differences on a scale of 1
(best) to 6 (worst). You are encouraged to elaborate on any
point that you could or could not hear. One last column will
rate overall wire preference. Please listen to all wires
before recording any reactions.
6. Preliminary results will then be tabulated and the results
(by number, not by brand of wire) will be disclosed. The top
three wires will be re-evaluated in a similar manner.
Another evaluation form will be filed out. Records will be
played at this time.
7. The results will again be tallied and all wire types will
then be revealed to the participants. The most preferred
wire will then be played to the least preferred wire for a
good laugh.
8. The other two sets of loudspeakers will be plugged in to see if
differences between the best and worst wires can still be
heard. (There seems to be some question of efficiency and
cost vs. return on the purchase of esoteric wires.) No
forms will be filled out for this portion of the evaluation.
9. Results of the evaluation will be mailed to "Stereo Review",
"The Absolute Sound", "High Fidelity", and "Audio" magazines.
-----------------------------------------------------leichter@yale-com.UUCP (Jerry Leichter) (12/06/83)
On a quick look, this looks like a good setup. You might, however, want to add a few "artificially bad" wires - say, a wire with a small resistor in series. It would be very interesting if people detected differences amoung the "real" wires but not between them and the artificially-crippled ones. -- Jerry