Alpha-core advise?

1) The nominal impedance of most any product known to man will vary as frequency is altered. This includes speakers, the output impedance of the amp, speaker cables, etc... As such, the key here is to use components that are "reasonably well matched" in terms of impedance and are capable of delivering the required amount of sustained voltage and current into those impedances without strain. It would be impossible to match impedances in a precise manner as far as the amplifier / speaker cable / speaker is concerned.

2) MI3's present a VERY low nominal impedance to an amplifier. While this can allow greater power transfer to occur, it can also "load down" the amplifier during very demanding passages with difficult speaker loads. On top of that, very short runs of MI3 connected to a reactive speaker can introduce increased non-linearities into the system. This is due to the higher than average amount of reflected EMF that the amp would see from such a low loss / low impedance speaker cable "modulating" the output of the amplifier. In effect, a slightly higher impedance ( like that of the MI2's ) can provide a bit of a "buffer" and add stability to the circuit.

3) Running multiple cables in parallel to the same set of binding posts would actually introduce erratic impedances into the amplifier / speaker equation. This is due to the variance in both spacing and geometry of the paralleled conductors, which are otherwise controlled through design considerations at the time of manufacturing of a single cable run. As such, some of the benefits of matching the nominal impedance of the cables to that of the speaker may be negated. In this respect, more is not always better, especially when one selects an optimal combination to begin with.

4) I would only recommend running MI3's for use on longer runs with VERY sturdy amps ( which are few and far between ). The MI3's lower nominal impedance, very heavy gauge conductors ( 7 gauge ) and minimal high frequency losses will tend to reduce the otherwise greater losses associated with these longer runs. Due to the higher levels of capacitance of these cables, which would be compounded by using longer than normal lengths, may require greater attention to detail in terms of the zobel's used and where they are placed in the circuit.

5) Goertz flat speaker cables require minimal break-in as compared to the mass majority of other speaker cables. This is due to both their geometry and materials used.

6) I would stick with a single run of MI2's so long as length is kept reasonable. The length that you are working with ( appr 10' ) should be fine for this application.

7) As previously mentioned, these cables provide a very neutral signal path joining the amp with the speakers. Whether or not you like what these cables bring to your system will be more a matter of how good of a job you did in selecting a suitable amp to drive your speakers instead of how much of a personal preference you have for other cabling and the colourations that they bring with them due to inferior design and materials. As such, be forewarned that better / more neutral cabling may not result in "better sound" or "sound that is more to my personal preference". If it sounds like crap with this cabling, don't blame the cabling, as the cabling is simply allowing you to hear what your system really sounds like.

Hope this helps and answers some of your questions. Sean
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Thanks Sean. I was hoping you might respond. The MI 2's were an improvement with the 2 different amps and 2 different speakers I tried them with. Interestingly the greatest improvement was with the smaller less expensive amp and to the smaller less expensive speakers. I miss having them here already. I think that the Thiels and the 3.5's in particular must be amongst the least "reactive" speakers offered. Wouldn't the use of the Zoebles compensate for the greater potential for reflected EMF in the MI3's? It seems pretty clear that your suggesting the MI 2's over the MI 3's for my application. Am I correct in assuming that you don't believe the Threshold S/500 II qualifies as a "VERY sturdy amp"? The idea of using integral spades has some appeal. Obviously the MI 3 lends itself to this application better than the MI 2. In the past you have recommended the use of Alpha-core silver spades, any thoughts on using the Alpha-cores "au-natural"? If so, what would you suggest vis-a-vis the MI 2 vs. the MI3? You mention that the "Goertz flat speaker cables require minimal break-in as compared to the mass majority of speaker cables. This is due to both their geometry and materials used." You have also endorsed the use of a cable cooker in past posts. Are you suggesting that these cables may be exempt from the advantages of using a cooker? BTW, Alpha-core seems to be shying away from making claims about the use of teflon in their latest MI 2 & 3 offerings. Any thoughts on the Alpha-core pricing structure? Seems a bit strange to me. Out side vendors seem to be able to provide more competitive pricing than buying direct as well. FWIW, I did manage to snap off the leads of one of the supplied Zoebels when tightening down on the speaker's binding posts. In the past you have suggested that one could improve upon the supplied design. How would I go about determining how to produce these for my application?

I'm running MI1 biwires from the 4 Ohm tap on a Music Reference RM-200 to VMPS RM-30s.

Here's my understanding of Alpha-Core's MI offerings:

MI3s offer twice the material (i.e., raw copper by weight) and half the resistance of MI2's, which in turn offer twice material and half the resistance of MI1's. Specifically, the equivalent gauge of MI3s, MI2s, and MI1 is approximately 7 AWG, 10 AWG, and 13 AWG respectively. This corresponds to a resistance of 0.0011, 0.0022, and 0.0044 Ohms/ft respectively (http://www.alphacore.com/mispeaker.html).

I thought I recalled a time when the cost of bare, unterminated wire scaled exactly with material (i.e., cost of unterminated MI3's = 2 * MI2's = 4* MI1s), but according to http://www.alphacore.com/shop/Speaker_CablesznCopper.html this is not true today, and indeed you do get a bit of a "bulk" discount as you move up the scale.

The resistance measures are relatively unimportant. Any system will overcome the difference between 0.0011 Ohms/ft and 0.0044 Ohms/ft with only the slightest adjustment to the volume. But impedance is another story.

Resistance is strictly an inhibition to electron flow for DC: i.e., a zero frequency, infinite wavelength signal. Once we introduce alternating current--which is what amps use to drive speakers--then capacitive and inductive reactance interact to also impede current flow. The (complex) sum of resistance, inductance, and capacitance is called impedance. It is the net inhibition to AC flow. Inductance can be thought of as an inhibition to a *change* in current (not simply an amount, or amplitude of current) caused by the generation of a magnetic field. Because music as encoded in oscillating electrical signals is highly dynamic (lots of change), excessive inductance per se--without some other reason for its presence--cannot be considered a good thing. Inductance acts as a low-pass filter, so the closer you get to DC, the better the current flow at the frequency, while the higher the frequency, the greater the inhibition.

Alpha-core's claim to fame is that by sandwiching the (+) and (-) wires so tightly together, they greatly reduce inductance (at the cost of increasing capacitance), to the net effect of low, final impedance numbers. Specifically, they claim a characteristic impedance of ~1.7 Ohms for MI3, 2.5 Ohms MI2, and 4 Ohms for MI1 (http://www.alphacore.com/mispeaker.html). Additionally, they do this in a very smart way: by sandwiching the strands so closely together, the mutual inductance that is generated in one wire as a direct result of oscillating current within it, is canceled almost exactly by the opposite effect in the other wire. So they get low impedance numbers by lowering net inductance--a smart quantity to lower for audio applications. Some folks claim that wires that tend to maximize inductance (the opposite of Alpha-Core's offerings) roll the highs (which may be good or not so good, depending on what's coming out of your amp).

Lower inductance comes at the cost of increasing capacitance. Because the (+) and (-) strands are so closely sandwiched together, it is easier for current to cross the insulation between the strands. Capacitance acts as a high-pass filter, so it is high frequencies that are "shorting" across the wire. But the capacitance numbers are in the pico-Farads/ft, so only spurious frequencies way off the audio scale (and beyond the capacity of most amps to generate) would be affected. So you are kinda' getting something (low inductance) for nothing (high capacitance): a good trade. Some amps may pathologically oscillate when presented with a high capacitance load, so the simple solution is to short the wires with a capacitor and a resistor (called a Zobel network), so the HF energy is simply dissipated as heat in the resistor, leaving the amp unaffected.

What does all this mean? Imagine, if you will, a complicated Rube-Goldberg contraption of pipes of differing sizes, all connected in funny ways and filled with water. This contraption is our analogy to your system as it runs from the wall to your source, pre-amp, amp, and finally speakers. Now start an oscillation at one end by tapping (e.g., at 60 Hz), and the goal is that via this convolution of pressures and relays and valves and so forth, a complicated oscillation of waves--an amplified mimic of the musical source--will come out the other end. With this analogy you can see that when you join a wide pipe to a narrow pipe, or vice versa, as the wave hits the junction it will create reflective waves back down the stream, which in turn will interact and (slightly, or not so slightly) corrupt the signal. This is an example of an impedance mis-match, and with electricity there is the same, analogous phenomenon. When you change impedance, waves are generated on the line. This is one reason why digital cables from a transport to a DAC can make a difference. Even though virtually all transports and all cables will send S/PDIF signals bit-perfect, minor anomalies caused by impedance mismatches generate jitter on the line, and affect the signal (specifically, it's timing). So, impedance matching has some relevancy to audio, and Alpha-Core's claim is that they do a better job than most in minimizing impedance mismatches between the amp the speakers, while at the same time lowering inductance.

How is this standardized? If you take a piece of speaker wire (w/ (+) and (-) strands), and don't hook it up to either the amp or the speaker, but simply measure the impedance between the strands it will measure essentially infinite. That is, the insulation between the strands creates a very high inhibition--which is good, because anything measurable would be a short. But in reality the inhibition is not infinite. There is some material separating the (+) and (-) strands, even if it is only air or an almost perfect vacuum. And indeed, there is a slight crossing of electrons between strands--that is, there is both a voltage and a current. An indication of the insulation material's propensity to carry--or inhibit--current is called the dielectric. The longer the cable, the more insulation, or opportunity, there is for electrons to cross. If we took an infinite length of cable, and then asked "Given this infinite length, what is the net inhibition to election flow across the insulation?" the answer would be the characteristic impedance. For RCA interconnects, this is historically 75 Ohms. For speaker cable there is no standard, so Alpha-Core says, "Well, let's make it close to the speaker's average band-wide impedance in a effort to minimize impedance mismatch." (Quotes are mine, not theirs).

At the end of the day, I think most systems would be challenged to uncover a difference between 1.7 Ohms characteristic impedance, 2.5 Ohms, and 4 Ohms--but, no doubt, some will show a difference with different wires. But do this part on listening—I don’t think we can rationalize/intuit that 2, or 4, or 5 Ohms will be better just because one number is closer to a speaker’s average impedance rating: it is better to compare Alpha-Core's offerings as a whole to cables that are in the 100+ Ohms category. I’m sure MI1’s would sound great on some 8 Ohm speakers. Alpha-Core gives a bit of a guide to choosing cables based on characteristic impedance here: http://www.alphacore.com/mifaq.html#select.

Hope this helps

I recall Nelson Pass commenting that the capacitance of the ribbon cables could cause some amplifiers to oscillate. I believe he was refering to his older T-hold models of which yours is one.

A quick note to Nelson or Wayne at Pass Labs should give you a quick answer. It's worth asking to prevent damage to the amp.

Better safe than sorry,

Loon

Rabelais, thank you very much. You have confirmed what I suspected about "characterisic impedance". Knowing is so much better! With regard to "bulk discount" it actually appears to be inverted; as you go up the line you pay a HIGHER rate! Very odd. Since I've already accepted the Alpha-core's as being superior (at least to my ears, in my system, at this time) to other manufacturers offerings, its come down to deciding between alpha-core's products. The scale that Alpha-core offers on their web site re: application in systems seems to be a rather general guide line rather than a strict requirement. Sean's opinion (for which I have great respect) seems to at the very least bear this out. The fact that the difference in price more than doubles is worthy of consideration too. IMHO, the MI 2's appear to be quite a bargain in comparison to just about anything else I've heard. The MI 3's, well thats a different ball of wax. I can't help but wonder if the market segment being pursued here may be more responsible for the elevated price more than the cost of materials.
Loontoon, thank you for the heads up. I believe the use of the afore mentioned Zoebles resolves the amplifier oscillation issue.