When it comes to cable length, the shortest length possible is almost always better. I say “almost,” because there are some exceptions, as will see.
Cables are critically important system components responsible for protecting the fragile voltages as they are transferred from point to point among the links of the audio/video chain. No cable can do better than simply minimizing the amount of loss during that transmission, as there will indeed be signal loss as the electrons make their way through the conductors and struggle to jump the boundaries imposed by the connections at each end. So, in my opinion, better cables simply “do less harm,” or put another way, lessening the amount of signal that is lost.
Virtually every audio or video system is a set compromises. Many times a compromise can be equipment location. Whether it be furniture restrictions, room layout, traffic path or objections from the non-audiophile co-habitants, we work around those limitations as best we can, and often than means longer cable runs. Maybe your front end gear is on one wall and your speakers on another. So the option becomes placing the amplifier(s) near the speakers, requiring long interconnects, or keep all the electronics together and employing long speaker cable runs. Generally speaking, my preference is for longer interconnects and shorter speaker cables. But, like everything else in life, there are always tradeoffs. As an example, longer unbalanced cables may be more apt to pick up noise (all cables are essentially antennae and subject to RF interference). Some preamps (especially those with a high output impedance or passive designs) may be sensitive to the additional load imposed by the cable, so a long run of interconnects may be contraindicated (or at least closely evaluated) in those instances.
Long speaker cables can also be of concern. First in terms of the added impedance that substantial runs may add, the increased resistance can, in more extreme cases, lead to power loss. And, in my experience, there simply tends to be more loss of signal though speaker cables than through interconnects of equivalent lengths. I know some cable manufacturers may disagree (mostly from makers of cables using in line networks), but the vast majority of time long interconnects with shorter speaker cables sounds better to me. Furthermore, on a Dollar-per-foot basis, equivalent quality speaker cables are usually far more expensive than their line-level counterparts, making longer interconnects/shorter speaker cables a less expensive alternative.
So, how long should cables be? Is there a "rule of thumb"? The answer is as short as possible! With speaker cables I like to stay under ten feet, and find eight feet to be the most popular and practical length. In a system where components are grouped closely together, one meter cables are the norm, but if the amplifiers are sited further away three to five meters isn't uncommon. Can you hear the degradation at those lengths? Yes, you can, but it may be an acceptable trade off to accommodate other considerations. Indeed, I’ve heard great sound in systems employing five to ten meters of cable between the amp and preamp. Usually balanced cables (when interfacing true differentially-balanced components) provide better results over very long runs than can be expected with single ended cabling.
When long runs (of either interconnects or speaker cables) are used, cable quality becomes extra important. Due to the additional signal losses longer runs impose, the better the cable is at “protecting” the signal, the better will be the sound. If you are forced with longer cable runs, try to push the cable budget a bit to minimize the negative impact of signal loss.
At the beginning we said shorter is “almost” always better. Well, here are some situations where that is not the case. A digital cable, for one, is an example of where a shorter length may not be ideal. A number of manufacturers of digital gear (and cables) that I’ve spoken with suggest 1.5M as being preferable to shorter lengths, such a 1M or less. This theory applies to all digital cables including USB, SPDIF and AES/EBU.
I’ve heard more than one explanation for why the length is important, but a common one has to do with reflections that occur between the two connected components and with longer digital cables those reflections are less detrimental. Of the few times I've been able to compare a 1.5M vs. a shorter length of the same cable, in most cases, the 1.5M cable sounded a bit better the shorter cable. Let me add that there are several cable manufacturers who do not espouse to this concept and feel that there is no ideal length and simply use whatever length is appropriate for the application. Maybe this has to do with the particular design concepts the various manufacturers employ? For whatever reason, there is division in the industry regarding this philosophy.
Another exception to “shorter is better rule” is when a cable manufacturer has designed the cable with a minimum length in mind. This can be true for some cables that utilize in-line networks or certain power cords that are optimized for certain lengths.
So there you have it, an oversimplification of a somewhat more complex topic. Do call us if you have any questions about your specific application. - Galen Carol