Thursday, December 6, 2012

Speaker cable - critical listening tests

In the Critical Listening class, we did some intensive listening to different loudspeaker cables. I love following the audiophile discussions about cabling and I especially love that people will pay thousands of dollars for several feet of copper wire. However, there are audible differences. 

The four cables that were auditioned:
  1. Apature Accusound L-SP518
  2. Monster Cable - original speaker cable
  3. Monster Cable - Navajo SuperFlat
  4. #24 solid conductor zip cord

Josh listening at the sweet-spot.

The amplifier was a Crown D75, which was chosen because of it's very high damping factor, neutral sound, and convection cooling (no fan). 

The loudspeakers were Tannoy PBM 6.5's - recently re-coned. It's sad/great/funny that these are the only passive studio monitors that we have!  Personally, I love these Tannoy's despite their rather prominent LF bump at 125 Hz. 

The sound source was a Oppo SACD player connected to a passive attenuator to control volume. 

The switch box was designed and built by Tim Brown (MFA class of 2011) based on an original design by myself. It contains 4 DPDT sealed relays in each box, connected to a controller via MIDI cables. One box is connected to the amp and the other to the speakers. The cables under test connect the two boxes together.  Admittedly, the wiring used to fanout from the switch boxes is also part of the circuit, but whatever it adds remains consistent regardless of cable under test (that wiring is #10 stranded power harness cabling visible as red/black in the picture below).

There were several music selections based on material the class was already familiar with.  

 One of the two relay switch boxes.

The controller remote.

The entire setup in action.

The results:

  1. Apature Accusound - general consensus was that this cable had a colored sound but with a slight efficiency advantage (due to its thick gauge) which was more apparent at low frequencies - thus the result appeared to boost lows compared the the other three (which would be impossible - as wires can't add gain!). Some adjectives that came up were thick, full and veiled.
  2. Monster Original - This was the winning cable.  Some adjectives that came up were neutral and clean.
  3. Monster Superflat - There was an eerie family resemblance in sound quality to the other Monster product.  However, this cable seemed to enhance brightness a tiny bit - probably by choking off LF.
  4. #24 zip - this was admittedly a throw-away entry.  I chose this to be the worst-case without melting or catching fire. Most apparent was a significant drop in level. Clearly the bottom octaves sounded loose and tubby - most likely to damping factor being severely restricted. However, the big surprise was that the stereo sound field seemed to narrow significantly.  This may be due to frequency-dependent skin-effect in the single, solid conductor.
It is important to note that the results are based on qualitative listening and not scientific measurement. This is in-line with what the class is about.  It is equally important to note that the cables themselves add no inherent sound quality changes, but what is happening here is they change the way the two pieces of equipment in the chain interact (the amplifier and the loudspeaker).   And... it's important to note that these were NOT double-blind tests. This is a class where we try and overcome personal bias without the double-blind or A/B/X methods.

Perhaps someday we will add a scientific critical measurement class. Admittedly, I could use some newer cable to better represent what's out there now - but none of these show up in professional use. Next year I will be adding in #2 or #4 jumper cables and standard-issue Belden speaker wire. Time for an 8 position switch box!

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