What were your own blind cable test results?

Springowl,

A lot depends on the speaker impedance and the amp output impedance. Amps with low output impedance will modify the transfer function as the speaker load varies with frequency. This can become audible when the speaker load vary significantly, as more voltage drop occurs across the amp output stage when the speaker impedance is very low.

For example, imagine the amp ouput impedance is 4 Ohms. The Speaker impedance varies between 16 ohms at 60 Hz (driver/box resonance) and 3 ohms at 2 KHZ. The speaker frequency response is perfectly flat.

The drop across the output impedance of the amp means that the music at 60 Hz is roughly two and four tenths times GREATER than it should be compared to music at 2 KHz (in order to sound flat). This is enough to be clearly audible. It will sound like bass bloom at the woofer resonance frequency.

Now throw in a cable with a high resistance and you will alter the transfer function again.

A 1 ohm cable will mean that the amplifier sees 17 ohms at 60 hz and 4 ohms at 2 Khz.

The music at 60 Hz will now be one and nine tenths greater then at 2 Khz....a small but not insignificant change.

In contrast, a speaker with a perfectly flat impedance response and flat frequency response will sound the same at both frequenies when driven by the amp with 4 ohm output impedance.

In contrast, an amplifier with low output impedance (less than 0.1 ohm) will sound the same at both frequenies even with the speaker that has a highly variable impedance response with frequency (3 Ohms at 2 Khz and 16 Ohms at 60 Hz).

So what does this mean? It means the audible effect is determined by the cable AND the equipment it is connecting.

In some cases a different cable will not make any difference and in other cases it will indeed make a subtle difference. Therefore it is incorrect to attribute the change (or lack of change) in sound (bass bloom in this case) to the cable alone! The same speaker cable may do nothing for one person and yet make a subtle difference for another....all dependent on the gear it connects.

Dbx: There's also another, more objective method for comparing interconnect cables, although most audiophiles don't practice it. It's called a bypass test, and unlike the conventional, subjective substitution test you employed (that mainly told you which interconnect sounded best to you, in your system, playing a particular audition disk -- the results could well have been different with other disks), it can tell you which interconnect is actually the most intrinsically accurate, and in what ways the different ones deviate from accuracy. Unlike the subjective test however, a bypass test doesn't primarily focus on which cable you *prefer* the sound of, so both kinds of tests are valuable in their ways. Still, in my opinion it's always better to get as much of an objective sense of what we're doing as possible -- one can never have too much much true information available when making a decision.

To me the easiest and most informative way of conducting an interconnect bypass test is to use a preamp having two tape-monitor loops, selectable by remote control. (The test can still be done using a preamp having only one tape monitor loop and/or lacking selection capability by remote, with a bit more hassle, and a bit less reliability due to increased time-lag.)

The basic idea is that instead of comparing an interconnect's presence in the signal chain against another's and picking which one sounds "better", you compare each interconnect's presence in the signal chain against *its absence* from the signal chain to discover which one degrades the signal the least, while identifying exactly in what ways each one degrades the signal (all wires only degrade the signal). This makes a bypass test much more of an objective test for determining the actual sounds of the cables themselves than the usual way, largely independent from complicating factors such as the sound of the rest of the system and of any particular audition disk, which to a given listener's tastes may or may not happen to compliment the sound of a cable under test.

The bypass method is just a little more involved than a typical serial-substitution or "A/B" test, where cable A is simply swapped for cable B, subjectively comparing the two directly against one another. To compare a cable's presence in the system against its absence, the cable must be inserted in such a way as to make it a removable "extra", or superfluous, run -- not one that's necessary for hearing any sound at all. This is where the tape monitor loops come in.

The only thing placed within the monitor paths are the test cables themselves, looped from the outputs straight back into their corresponding inputs. So when Tape Monitor 1 or 2 is selected for listening, the test cables in that loop get inserted into the signal path (along with the extra jacks, switches and internal wiring that the monitor paths entail, but those additions will be the same for each of the interconnects under test and therefore represent a controlled variable that doesn't handicap the test validity), and when Source is selected the test cables are omitted from the signal path.

The other difference from the way a standard A/B test is conducted is that you don't compare Tape Monitor 1 (cable A) directly against Tape Monitor 2 (cable B) -- for that a normal substitution test would do just as well. Instead, what you want to do is switch between Tape Monitor 1 and Source -- in other words, compare one of the test cables against the reference represented by the direct feed -- then compare Tape Monitor 2 against Source to assess the other cable in the same way while minimizing time lag between the two (dual loops and remote control helps here), and through repeated trials, triangulate the results for those two varieties of cable under test.

For every two kinds of interconnect compared in this indirect (parallel rather than serial) fashion against their absence from the chain, there will presumably be one that alters the signal less when compared to the absolute reference of the direct Source feed. This is what makes the test objective: you aren't just listening for which cable you prefer -- you are listening for which one does the least damage (or least objectionable type of damage) to the signal it is fed *as compared to that signal*. You can do this test round-robin elimination style with multiple contenders; the winning cable will be the one of the group whose output hews closest to the signal it is fed -- largely irrespective of what disks are played, the balance of the rest of the system, or indeed your own preferences or biases. (The last point means a bypass test can be performed sighted -- i.e., solo -- without fear of your interpretation of the results being unduly influenced by a cable's appearance, brand image or price.)

Don't get me wrong, subjective auditioning is still important, probably more important than bypass testing. If your speakers have a response peak that using an interconnect with a complementary response dip ameliorates, whuddaya gonna do, choose accurate interconnects and replace your speakers? Well, in my case probably so, but I like having relatively certain points of reference where I can get them -- both because most catagories of gear unavoidably boil down to subjective preference choices and system matching, so why not avoid that uncertainty where you can (I mean, what other way exists for choosing, let's say, a power cord?), and also because colored interconnects mean you can't trust your impressions of the accuracy of anything else you're trying to evaluate either. So, I did make a decision to choose my interconnects based mostly on bypass testing and let the chips fall where they may (there's always those power cords to play with if need be). Anyway, if you've ever experienced the dilemma of preferring this interconnect with this recording but that interconnect with that recording, a bypass test will tell you what's really up. And it's interesting in its own right -- you'd be surprised, perhaps, to hear the colorations imparted by your wires revealed stripped bare, instead of only pitted against those of other wires. (Most wires in one way or another sound -- get ready and believe it or not -- wirey!)

It always dismays me, though it hardly surprises me, that published reviews of interconnects, without exception, wax on and on about the reviewers' subjective impressions within their system contexts, but never conduct bypass tests that could shed some more universally applicable light on the exact sound quality, independent of price and preference. I've even read major audio-magazine reviews of interconnects written by prominent reviewers who profess (and bemoan the "fact") that there exists no test they know of which can mitigate the uncertainty about accuracy inherent in the subjective serial-substitution auditioning method! That's true for many component catagories, like speakers and power amps and most sources, but definitely not for interconnects, and also, with different test setups and to somewhat reduced degrees of validity and with more difficulty, speaker cables, preamps, and even DACs. With interconnects especially though (at least given typical I/O impedance conditions), there's simply no need to wonder which is more faithful and which is merely flattering (no matter which you ultimately choose).

What I don't know is if these "experts" are really ignorant about bypass testing, or whether there's a conspiracy in the reviewing industry not to practice bypass testing where applicable and pretend to readership as if it doesn't exist. Either way's an audiophile sham, intellectually at least, if not in the grand scheme of things. Then again, here on Audiogon I once innocently (ha) asked, amidst an in-depth and well-attended lengthy thread focusing on high-$ interconnects, whether anybody present had ever done any bypass tests to confirm their subjective impressions, and was met by silence as resounding as it was expected. So those who get as much enjoyment from the debate and the merry-go-round as from the listening may want to forget this post :-)

Excellent, well-reasoned position, Zaikesman. That most of us don't use this method says ... well, I'm not sure. Perhaps that we are not interested in objectivity. Or maybe we don't have preamps with tape loops.

But as useful as your prescribed test is, it does not consider the performance of an interconnect between two specific components. Perhaps it shouldn't because that raises the whole question of system matching, which is a variable that introduces so much complexity as to make reviews almost useless. But still.

Drubin: as your prescribed test is, it does not consider the performance of an interconnect between two specific components

I think that's exactly Zaikesman's point; when you're testing an intereconnect's performance between two specific components, you're introducing more variables into your test. The only way to objectively measure the performance of the *cable* is to isolate the cable as the only added variable in the equation of your system. He's not addressing the cable in relation to other components, because then your test ceases to address the cable by itself.

My point is that one *could* argue that a cable's performance is only meaningful in the context of the components it is used with.