How to determine if a cable is neutral.

Ok folks. I’ve heard this enough. And mentioned a lot. People often refer to
Cables and equipment as neutral. How exactly is this determined? I’m 110% a cable believer. But, who exactly determines when a cable or piece of equipment is neutral. And how do these tests come about? Besides ones ears?
2 channel:
Bryston 4B3, Bryston BDA3, Cary SLP05, Shanling CDT1000SE with parts conneXion level 2 mods, Nottingham analogue ace space 294, soundsmith Carmen MKii, Zu DL103 MKii, Ortofon MC 20 MKii, Dynavector XX2 MKii, Rogue Audio Ares, Core power technologies balanced power conditioner, Akiko Corelli power conditioner with Akiko Audio HQ power cable, Nordost heimdall 2, Frey 2, interconnects, speaker and power cables, Focal Electra 1028 BE 2, Auralic Aries Femto, Black diamond racing cones, ingress audio level 1 roller blocks, JL Audio E110 with Auralic subdude, Primacoustics room treatments.
Theater:
Focal Aria 926,905,CC900, SVS PB ultra x2. Pioneer Elite SC85, Oppo BDP93, Panamax M5400PM, Minix neox6, Nordost Blue heaven LS power cables.

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Comments

  • F1nut
    F1nut Posts: 50,548
    When my ears aren't ready to bleed from a hot top end or it doesn't sound lifeless and muddy, then it's neutral. My sound preference is slighty to the warm side of neutral.
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."


    President of Club Polk

  • SIHAB
    SIHAB Posts: 4,902
    Though I think it unlikely, a neutral cable in one system may not be in another!
    Then there is your ability to hear...
    Speakers: Polk Lsim, ATC SCM19 v2, NHT SuperzeroSpeaker Cables: DH Labs, Transparent, Wireworld, Canare, Monster: Beer budget, Bose ears
  • tonyb
    tonyb Posts: 32,962
    True ^^^

    In my book, neutral means not adding or subtracting anything from the signal, not warm, not cold as ice.

    I would argue though, even a neutral cable would add or subtract something from the sound....maybe more/less weight/tone, soundstage, air , etc.

    If we were to define neutral simply by the balance between warm and cold, I think AQ cables would fit that mold. Balanced cables also do well for neutral sounding cables. Just my opinion there.
    HT SYSTEM-
    Sony 850c 4k
    Pioneer elite vhx 21
    Sony 4k BRP
    SVS SB-2000
    Polk Sig. 20's
    Polk FX500 surrounds

    Cables-
    Acoustic zen Satori speaker cables
    Acoustic zen Matrix 2 IC's
    Wireworld eclipse 7 ic's
    Audio metallurgy ga-o digital cable

    Kitchen

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  • VR3
    VR3 Posts: 28,641
    Every component alters the signal a little bit, all about finding components that work well together, ie... Synergy
    - Not Tom ::::::: Any system can play Diana Krall. Only the best can play Limp Bizkit.
  • EndersShadow
    EndersShadow Posts: 17,590
    You ask the cable if it’s votes Democrat or Republican. If it says “varied based on the issue” then it’s neutral :smile:
    "....not everything that can be counted counts, and not everything that counts can be counted." William Bruce Cameron, Informal Sociology: A Casual Introduction to Sociological Thinking (1963)
  • tonyb
    tonyb Posts: 32,962
    True again Trey, but as we argued in the other thread, one has to consider cables a component in one's system, When you don't, your missing a key ingredient that could bring everything together.
    HT SYSTEM-
    Sony 850c 4k
    Pioneer elite vhx 21
    Sony 4k BRP
    SVS SB-2000
    Polk Sig. 20's
    Polk FX500 surrounds

    Cables-
    Acoustic zen Satori speaker cables
    Acoustic zen Matrix 2 IC's
    Wireworld eclipse 7 ic's
    Audio metallurgy ga-o digital cable

    Kitchen

    Sonos zp90
    Grant Fidelity tube dac
    B&k 1420
    lsi 9's
  • K_M
    K_M Posts: 1,629
    [quote="DSkip;c-2467144" As you move up the line, you get other aspects to the sound - cleaner, more detailed, better separation, extended soundstage in all directions, wider frequency range...

    [/quote]

    Neutral passes the signal with no degradation.
    A cable can not add anything nor better the signal being sent through it.

    Sorry, but that sounds like Ad-speak from a cable company...not reality.
  • F1nut
    F1nut Posts: 50,548
    Gawd, you still don't get it. Every piece in a rig including cables adds or subtracts and makes it better or worse.
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."


    President of Club Polk

  • pitdogg2
    pitdogg2 Posts: 25,441
    Seriously Kelly ?
    Shakes head walks away......
  • mdaudioguy
    mdaudioguy Posts: 5,165
    edited December 2018
    K_M wrote: »
    [quote="DSkip;c-2467144" As you move up the line, you get other aspects to the sound - cleaner, more detailed, better separation, extended soundstage in all directions, wider frequency range...



    Neutral passes the signal with no degradation.
    A cable can not add anything nor better the signal being sent through it.

    Sorry, but that sounds like Ad-speak from a cable company...not reality.

    I'm concerned about your quoting ability. :#
  • Hermitism
    Hermitism Posts: 4,261
    mdaudioguy wrote: »
    K_M wrote: »
    [quote="DSkip;c-2467144" As you move up the line, you get other aspects to the sound - cleaner, more detailed, better separation, extended soundstage in all directions, wider frequency range...



    Neutral passes the signal with no degradation.
    A cable can not add anything nor better the signal being sent through it.

    Sorry, but that sounds like Ad-speak from a cable company...not reality.

    I'm concerned about your quoting ability. :#
    At least it's above her reply.
  • BlueFox
    BlueFox Posts: 15,251
    It amazes me that people post, and then don't check to make sure it is correct. She is missing the right bracket in her quote.
    Lumin X1 file player, Westminster Labs interconnect cable
    Sony XA-5400ES SACD; Pass XP-22 pre; X600.5 amps
    Magico S5 MKII Mcast Rose speakers; SPOD spikes

    Shunyata Triton v3/Typhon QR on source, Denali 2000 (2) on amps
    Shunyata Sigma XLR analog ICs, Sigma speaker cables
    Shunyata Sigma HC (2), Sigma Analog, Sigma Digital, Z Anaconda (3) power cables

    Mapleshade Samson V.3 four shelf solid maple rack, Micropoint brass footers
    Three 20 amp circuits.
  • GlennDog
    GlennDog Posts: 3,120
    To answer the OPs question. I've no clue

    I'm no interior decorator, but I know what I like when I see it

    I've never claimed to be an audiophile, but I know what I like when I hear it

    About 4 weeks ago, I rolled 4 lightly used WW PCs into my system. At first, meh. This weekend wowza!

    I prefer the warmer side of neutral and Schitte is sounding wonderful!
    AC Regenerator PS Audio PerfectWave Power Plant 10
    Source Lumin U1 Mini into Lampizator Baltic 4 DAC
    Pre Cary SLP-05
    Power Rogue M180 Dark monos
    Mains Salk HT2-TL
    Rythmik F12
  • mikeyb128
    mikeyb128 Posts: 2,885
    GlennDog wrote: »
    To answer the OPs question. I've no clue

    I'm no interior decorator, but I know what I like when I see it

    I've never claimed to be an audiophile, but I know what I like when I hear it

    About 4 weeks ago, I rolled 4 lightly used WW PCs into my system. At first, meh. This weekend wowza!

    I prefer the warmer side of neutral and Schitte is sounding wonderful!

    I faced a smiliar experience a few weeks ago. Purchased 2 WW silver Electra 7 PC’s for a good deal. Put them in and was very, very disappointed. A few weeks go by and holy $&&@!
    2 channel:
    Bryston 4B3, Bryston BDA3, Cary SLP05, Shanling CDT1000SE with parts conneXion level 2 mods, Nottingham analogue ace space 294, soundsmith Carmen MKii, Zu DL103 MKii, Ortofon MC 20 MKii, Dynavector XX2 MKii, Rogue Audio Ares, Core power technologies balanced power conditioner, Akiko Corelli power conditioner with Akiko Audio HQ power cable, Nordost heimdall 2, Frey 2, interconnects, speaker and power cables, Focal Electra 1028 BE 2, Auralic Aries Femto, Black diamond racing cones, ingress audio level 1 roller blocks, JL Audio E110 with Auralic subdude, Primacoustics room treatments.
    Theater:
    Focal Aria 926,905,CC900, SVS PB ultra x2. Pioneer Elite SC85, Oppo BDP93, Panamax M5400PM, Minix neox6, Nordost Blue heaven LS power cables.

  • mikeyb128
    mikeyb128 Posts: 2,885
    Thanks for the comments guys. My question seems a little silly. Wanted to see what others definitions of neutral were.

    I’ve listened to a lot of amps considered to be neutral, that came off as cold and a little edgy.
    2 channel:
    Bryston 4B3, Bryston BDA3, Cary SLP05, Shanling CDT1000SE with parts conneXion level 2 mods, Nottingham analogue ace space 294, soundsmith Carmen MKii, Zu DL103 MKii, Ortofon MC 20 MKii, Dynavector XX2 MKii, Rogue Audio Ares, Core power technologies balanced power conditioner, Akiko Corelli power conditioner with Akiko Audio HQ power cable, Nordost heimdall 2, Frey 2, interconnects, speaker and power cables, Focal Electra 1028 BE 2, Auralic Aries Femto, Black diamond racing cones, ingress audio level 1 roller blocks, JL Audio E110 with Auralic subdude, Primacoustics room treatments.
    Theater:
    Focal Aria 926,905,CC900, SVS PB ultra x2. Pioneer Elite SC85, Oppo BDP93, Panamax M5400PM, Minix neox6, Nordost Blue heaven LS power cables.

  • tonyb
    tonyb Posts: 32,962
    mikeyb128 wrote: »
    Thanks for the comments guys. My question seems a little silly. Wanted to see what others definitions of neutral were.

    I’ve listened to a lot of amps considered to be neutral, that came off as cold and a little edgy.

    Not uncommon, most things I hear billed as "neutral come off as cold and sterile sounding. I also prefer a bit on the warmer side of neutral.
    HT SYSTEM-
    Sony 850c 4k
    Pioneer elite vhx 21
    Sony 4k BRP
    SVS SB-2000
    Polk Sig. 20's
    Polk FX500 surrounds

    Cables-
    Acoustic zen Satori speaker cables
    Acoustic zen Matrix 2 IC's
    Wireworld eclipse 7 ic's
    Audio metallurgy ga-o digital cable

    Kitchen

    Sonos zp90
    Grant Fidelity tube dac
    B&k 1420
    lsi 9's
  • cortico
    cortico Posts: 587
    Neutrality is when nothing is missing, displaced or highlighted. When the attention is pulled towards isolated aspect of the listening material, it's not neutral.
  • mhardy6647
    mhardy6647 Posts: 33,801
    edited January 2019
    cortico wrote: »
    Neutrality is when nothing is missing, displaced or highlighted. When the attention is pulled towards isolated aspect of the listening material, it's not neutral.

    FWIW, I would agree -- and, to amplify B) this notion a little bit, I think that when a hifi is doin' its job, hifi-wise, it is possible for the listener to pick a focal point and listen into the reproduced recording (music!) as she or he sees fit. For example, one can choose to pick apart, say, a three- or four-part vocal harmony and focus one's attention on one part.

    One of the local vacuum tube gurus up my way refers to listening in to the music. Not the mix, but the music.

    When the focus is pulled to anything but the music (program material) itself -- I would opine* that there's something less than optimal going on :)

    ________________
    * Heck, I'd argue the point -- but then again, I can be one argumentative S O B when it comes to some of this stuff (stupid & pointless though that be)! :p
  • tonyb
    tonyb Posts: 32,962
    cortico wrote: »
    Neutrality is when nothing is missing, displaced or highlighted. When the attention is pulled towards isolated aspect of the listening material, it's not neutral.

    I can go along with that, mostly. How does one know if it's the cable or the gear being neutral....or not ?
    HT SYSTEM-
    Sony 850c 4k
    Pioneer elite vhx 21
    Sony 4k BRP
    SVS SB-2000
    Polk Sig. 20's
    Polk FX500 surrounds

    Cables-
    Acoustic zen Satori speaker cables
    Acoustic zen Matrix 2 IC's
    Wireworld eclipse 7 ic's
    Audio metallurgy ga-o digital cable

    Kitchen

    Sonos zp90
    Grant Fidelity tube dac
    B&k 1420
    lsi 9's
  • mantis
    mantis Posts: 17,194
    tonyb wrote: »
    True ^^^

    In my book, neutral means not adding or subtracting anything from the signal, not warm, not cold as ice.

    I would argue though, even a neutral cable would add or subtract something from the sound....maybe more/less weight/tone, soundstage, air , etc.

    If we were to define neutral simply by the balance between warm and cold, I think AQ cables would fit that mold. Balanced cables also do well for neutral sounding cables. Just my opinion there.
    Agreed. Audioquest builds all their cables with neutral in mind. They want their cables to pass along the signal with nothing lost as much as possible.
    Dan
    My personal quest is to save to world of bad audio, one thread at a time.
  • mantis
    mantis Posts: 17,194
    DSkip wrote: »
    Neutral cables are Transparent in the system. They allow each component to add its own flavor and showcase what said component can do for a system. Neutral cables also transfer from system to system without much issue.

    I know for a fact Wireworld measures their cables and uses this as a major determinant for any products they release. The overall tone doesn't change much because they strive for an unflavored tonal balance. As you move up the line, you get other aspects to the sound - cleaner, more detailed, better separation, extended soundstage in all directions, wider frequency range...

    You don't have to have neutral cables to get stellar sound. That is why many use them as tuning devices. I have found it much easier to evaluate gear with neutral cables for the reason above.
    This also can be said about Audioquest. It's why stuck with them all these years because they work in all systems. I noticed this many years ago when I was comparing different cables in different systems in different rooms.

    Dan
    My personal quest is to save to world of bad audio, one thread at a time.
  • heiney9
    heiney9 Posts: 25,165
    edited January 2019
    K_M wrote: »
    Neutral passes the signal with no degradation.
    A cable can not add anything nor better the signal being sent through it.

    Sorry, but that sounds like Ad-speak from a cable company...not reality.

    Wow...........just Wow! Listen to silver cable and copper cable and tell me they sound the same.

    Those that don't know, don't know that they don't know. And some will never take the time or have an open mind to know.

    H9

    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass Pass Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Pangea AC14SE MKII | Legend L600 | BlueSound Node 3 - Tubes add soul!
  • BlueFox
    BlueFox Posts: 15,251
    heiney9 wrote: »
    K_M wrote: »
    Neutral passes the signal with no degradation.
    A cable can not add anything nor better the signal being sent through it.

    Sorry, but that sounds like Ad-speak from a cable company...not reality.

    Wow...........just Wow! Listen to silver cable and copper cable and tell me they sound the same.

    Those that don't know, don't know that they don't know. And some will never take the time or have an open mind to know.

    H9

    If they don’t sound the same then one, or both, aren’t neutral. Of course, the hard part is creating a neutral cable.

    Lumin X1 file player, Westminster Labs interconnect cable
    Sony XA-5400ES SACD; Pass XP-22 pre; X600.5 amps
    Magico S5 MKII Mcast Rose speakers; SPOD spikes

    Shunyata Triton v3/Typhon QR on source, Denali 2000 (2) on amps
    Shunyata Sigma XLR analog ICs, Sigma speaker cables
    Shunyata Sigma HC (2), Sigma Analog, Sigma Digital, Z Anaconda (3) power cables

    Mapleshade Samson V.3 four shelf solid maple rack, Micropoint brass footers
    Three 20 amp circuits.
  • steveinaz
    steveinaz Posts: 19,538
    Be it cables or any other equipment, I think the human voice is the best reference for both neutrality, and driver integration. Just MY 2 cents.
    Source: Bluesound Node 2i - Preamp/DAC: Benchmark DAC2 DX - Amp: Parasound Halo A21 - Speakers: MartinLogan Motion 60XTi - Shop Rig: Yamaha A-S501 Integrated - Shop Spkrs: Elac Debut 2.0 B5.2
  • heiney9
    heiney9 Posts: 25,165
    edited January 2019
    ...and piano too. Ultra hard to reproduce piano notes accurately.

    As with human vocals, piano and everything else, we are still at the mercy of the recording process.

    But if one can single out a few recordings they are absolutely audibly familiar with, use those (and only those) to compare components, cables, etc. You start to form a base of knowledge.

    Also, everything adds or subtracts something. We all have our preferences and certain designers work extremely hard at reducing the adds and subtracts, but you will never eliminate them all, it's the nature of the beast and fundamentally impossible when you have so many variables in play (caps, wire, diodes, resistors, cable type, cable composition, listening position, room effects, mental acuity of listening.....and on and on and on.....

    I would also bet most if not all people would not like listening to recordings and gear that are as close to neutral as possible. It can be rather stale, lifeless and flat.

    One also has to clearly define what neutral means to them, specifically and technically. Simply saying "a clean unadulterated signal", means nothing because that's not possible in the real world. Also, what's clean? No 2nd harmonic, no 3rd harmonic, what level and what type of distortion.? Some types of distortion are preferred and/or occur naturally. Take those away or minimize them, is it still the same realistic signal or is it altered from its natural state?

    H9
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass Pass Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Pangea AC14SE MKII | Legend L600 | BlueSound Node 3 - Tubes add soul!
  • K_M
    K_M Posts: 1,629
    edited January 2019
    heiney9 wrote: »
    K_M wrote: »
    Neutral passes the signal with no degradation.
    A cable can not add anything nor better the signal being sent through it.

    Sorry, but that sounds like Ad-speak from a cable company...not reality.

    Wow...........just Wow! Listen to silver cable and copper cable and tell me they sound the same.

    Those that don't know, don't know that they don't know. And some will never take the time or have an open mind to know.

    H9

    I never insinuated silver and copper cables sound the same.

    I said the definition of neutral is to pass a signal unaltered.
    If the signal is changed, it is not neutral.

    It is very easy to know what is neutral or not....Quite easy.
    FYI an unaltered signal absolutely is possible.

    And it is quite easy to determine what is altered or not altered.
    I can go more into detail, of you would like, but only if you have an open mind and want to understand.

  • F1nut
    F1nut Posts: 50,548
    There is no such thing as an unaltered signal. That's Audio 101.
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."


    President of Club Polk

  • nooshinjohn
    nooshinjohn Posts: 25,415
    edited January 2019
    K_M wrote: »
    I never insinuated silver and copper cables sound the same.

    I said the definition of neutral is to pass a signal unaltered.
    If the signal is changed, it is not neutral.

    It is very easy to know what is neutral or not....Quite easy.
    FYI an unaltered signal absolutely is possible.

    And it is quite easy to determine what is altered or not altered.
    I can go more into detail, of you would like, but only if you have an open mind and want to understand.

    You mean well K_M, but you seem to have little understanding about this particular subject. The only was a signal can be transmitted unaltered, is if you are watching an acoustic performance live and in person, no speakers, microphones, electric guitars... nothing but an unfettered completely acoustic performance.

    EVERYTHING and I do mean EVERYTHING that is electrified, recorded, and played back by any form of audio equipment is altering the signal as it was originally intended. The goal of a high fidelity stereo system is to do as little additional damage to that recorded signal as possible. Therefore, everything in the signal path is critically important to faithfully reproducing the sound.

    EVERYTHING matters, and some gear just don't work well together for that purpose, while others do. Some cables work exceptionally well and others don't. The critical factor in how well a system works as a whole is determined by the listener. I have heard setups, that to my ears, sounded like Yoko Ono strangling a cat, while the owner of that system says it is his greatest achievement in sound reproduction.

    Excellent sound is in the ears of the individual listening.

    Again K_M, I am not in any way trying to diminish your prodigious experience or the insightful gifts you bring to the forum. Instead I would suggest that you perhaps consider the concept that others may have a considerable amount of experience in these areas, and sometimes deferring to those with more experience could be a great benefit to your learning and understanding as well.

    The Gear... Carver "Statement" Mono-blocks, Mcintosh C2300 Arcam AVR20, Oppo UDP-203 4K Blu-ray player, Sony XBR70x850B 4k, Polk Audio Legend L800 with height modules, L400 Center Channel Polk audio AB800 "in-wall" surrounds. Marantz MM7025 stereo amp. Simaudio Moon 680d DSD

    “When once a Republic is corrupted, there is no possibility of remedying any of the growing evils but by removing the corruption and restoring its lost principles; every other correction is either useless or a new evil.”— Thomas Jefferson
  • tonyb
    tonyb Posts: 32,962
    edited January 2019
    K_M wrote: »
    heiney9 wrote: »
    K_M wrote: »
    Neutral passes the signal with no degradation.
    A cable can not add anything nor better the signal being sent through it.

    Sorry, but that sounds like Ad-speak from a cable company...not reality.

    Wow...........just Wow! Listen to silver cable and copper cable and tell me they sound the same.

    Those that don't know, don't know that they don't know. And some will never take the time or have an open mind to know.

    H9

    I never insinuated silver and copper cables sound the same.

    I said the definition of neutral is to pass a signal unaltered.
    If the signal is changed, it is not neutral.

    It is very easy to know what is neutral or not....Quite easy.
    FYI an unaltered signal absolutely is possible.

    And it is quite easy to determine what is altered or not altered.
    I can go more into detail, of you would like, but only if you have an open mind and want to understand.
    K_M wrote: »
    heiney9 wrote: »
    K_M wrote: »
    Neutral passes the signal with no degradation.
    A cable can not add anything nor better the signal being sent through it.

    Sorry, but that sounds like Ad-speak from a cable company...not reality.

    Wow...........just Wow! Listen to silver cable and copper cable and tell me they sound the same.

    Those that don't know, don't know that they don't know. And some will never take the time or have an open mind to know.

    H9

    I never insinuated silver and copper cables sound the same.

    I said the definition of neutral is to pass a signal unaltered.
    If the signal is changed, it is not neutral.

    It is very easy to know what is neutral or not....Quite easy.
    FYI an unaltered signal absolutely is possible.

    And it is quite easy to determine what is altered or not altered.
    I can go more into detail, of you would like, but only if you have an open mind and want to understand.

    If that were the case, how do you know if a cable is passing the signal "unaltered", if you don't know what it's suppose to sound like in the first place ? You have to have a frame of reference to determine that.
    HT SYSTEM-
    Sony 850c 4k
    Pioneer elite vhx 21
    Sony 4k BRP
    SVS SB-2000
    Polk Sig. 20's
    Polk FX500 surrounds

    Cables-
    Acoustic zen Satori speaker cables
    Acoustic zen Matrix 2 IC's
    Wireworld eclipse 7 ic's
    Audio metallurgy ga-o digital cable

    Kitchen

    Sonos zp90
    Grant Fidelity tube dac
    B&k 1420
    lsi 9's
  • K_M
    K_M Posts: 1,629
    edited January 2019
    tonyb wrote: »


    If that were the case, how do you know if a cable is passing the signal "unaltered", if you don't know what it's suppose to sound like in the first place ? You have to have a frame of reference to determine that.

    First off, cables do not have sound.
    They pass an alternating current signal.
    You can not "listen" to a cable, it simply passes an electrical signal.

    An ideal or perfect cable would be "no cable", as that would impart no change to the signal.
    Nothing would be removed or altered if there was no cable at all.
    With that being your theoretical ideal or goal, it then is quite easy to compare a signal to that standard.

    Since a cable is totally passive, and can only either pass the signal fully intact, OR, slightly degrade the signal,(usually high frequencies) one can compare the amount of degradation, to the theoretical ideal of no cable.

    In other words, what is put into one end, should ideally be exactly what is present at the other end.
    I am willing to bet if you took 2 measurements one at the end of a speaker cable, and one at the beginning (in theory the no cable at all end) and inverted one signal, if they are exactly the same, (but opposite) the differences would cancel each other out and result in a "flat line".

    If there was degradation (even minimal) then the inverted signals would not cancel each other out, and the result would be the difference signal, between the ideal of no cable at all, and the effect the actual cable imparts on the signal.