Can speaker cables be too thick?

Chris,

Honestly is doesn't really matter but yes thicker is in general is ever so slightly better to avoid power loss and enhance damping. However if you want to delve into complexities see this link Cable diameter and spacing

Before you panic, remember that the scales on these charts are so exagerated and effects are so very small that it really doesn't matter.

Some people will try to convince that group delay is a big issue in speaker cables (from self inductance) and some will talk about skin effect....and on and on the hype will run....litz wires you name it - all kinds of solutions. These people are correct about some of the physics and it does matter in RF applications....but they are wrong about the order of magnitude of these effects by up to 1000 at audio frequencies.

For power loss we are talking about tenths of a decibel (for 8 ohm load) and for group delay we are talking two or three hundred BILLIONTHS of a second. And those of you that worry about the group delay differences from low frequency to high frequencies....these are typically 50 billionths of a second. This is equivalent to moving your tweeter ONE THOUSANDTH of an INCH. (Do you imagine that the baffle and tweeter plate holding the tweeter are manufactured to these kind of tolerances? - Forget it)

The fact of the matter is that pretty much any cable should be ok provided you avoid the obvious pitfalls...4 ohm speakers with 50 foot speaker cables of 20 AWG.

This is an independent engineers view. I have no axe to grind as I don't sell cables.

You do have an axe to grind in that you seem interested in convincing yourself and others that cables all sound virtually the same- and that's perfectly ok- but you're wrong:)

No problem Dave, I respect that you and many others disagree on the magnitude of the audible effects of different cables. I know some believe the effects to be extraordinary (this is where I strongly disagree). We won't settle it in a thread anyway and everyone has to decide for themselves.

As for an agenda, axe to grind, or a vested interest in promoting untruths - I honestly don't have any motive other than sharing what I believe/understand to be true. Engineers work under a strict code of ethics and it would be unethical for me to promote or sell extremely expensive audio cables if engineering principles have taught me to believe that the benefits are almost negligible. I do respect everyone's right to disagree and to buy, manufacture and sell the very best high performance cables they can. I respect that other engineers may disagree - we all work and follow our training, experience and conscience. For the record I make no claims at being an expert on audio cables design but I simply understand the basic scientific principles.

I should perhaps add that it is possible to construct audio equipment in such a way that small cable differences can be magnified.

The principle of audio reproduction is that the voltage coming out of the amplifier represents the amplified original voltage signal (from a recording) as faithfully as possible.

Audio equipment therefore should (in theory) have low output impedance compared to the load being driven (high input impedance) - and it is this "rule of thumb" which preserves the accuracy of the voltage signal between components. In this case, variations in the load become insignificant to the output device and there is negligible signal voltage loss across the output impedance of the driving amplifier: the load sees what it should.

Now ignoring cables for a moment, imagine a load with large varations in impedance with frequency, say from 20 ohms to 1 ohm. Now connect this to a 10 Ohm (high) output impedance amp. The voltage drop across the output of the amp at the lowest impedance point of the speaker will be 10/11 or roughly 91%....this means a mere 9% of the intended voltage actualy reaches the speaker. At 2 ohm load the calculation becomes 10/12 and 83 % of the voltage drop is across the amplifier and the speaker sees 17% of the intended voltage signal. In this case a 1 ohm variation in load causes a near doubling in voltage seen by the speaker. At the frequencies where the speaker load impedance is highest (20 ohms), the drop across the amplifier will be only 10/30 or 30% and 70% of the intended drive voltage will reach the speaker... this is nine times more voltage then at the lowest impedance point.

If you do the same calculation for a 0.01 output impedance amp you will conclude that 99% of the drive voltage reaches the speaker in all cases.

The above is mere "back of the envelope stuff" or gross approximations but it establishes that a high output impedance device will change significantly its driving voltage in reponse to small variations in a low impedance load. And that, unfortunately, includes slight inductance, impedance and capacitance from speaker cables too...in this situation it can become a not entirely negligible factor.

I would suggest that there are ways to design audio equipment so that cables have only very minor effects: speakers that do not have nasty low impedance dips and power amplifiers with low output impedance under all frequency conditions; it is these two conditions are mainly required to minimize the effect of cables. This is also a well known rule of thumb.

Slv,

Yes inductance appears to be one of the factors that can begin to affect roll-off in highs. Skin effect can do this to (ever so slightly). However, the effects of inductance are still pretty small unless you go to large wire spacings (ribbon cables) and long lengths.

A difficult load (much lower than 8 Ohms) will lower the point at which inductance begins to affect high frequencies.