A hard look at the effect of cables


Hey guys
A fellow EE audionut directed me to these articles and I thought some of you might be very interested to read them too. Two arguably qualified engineers went through the pains to take high quality measurements of the effect of cables and their interation with a complex electrical load, such as a full range loudspeaker, and with a complex signal, such as music. The link below is to the final installment but be sure to also read parts 4 and 5 very carefully. Part 5's Figures 6.8 and 6.9 are really amazing. I had never seen such measurements and they definitely seem to correlate with what we hear. The cables lengths are longer than normal but I think the point is well made. Hope you enjoy this read as much as I did.

http://www.planetanalog.com/showArticle.jhtml?articleID=202102592

Arthur
aball
Blame the cables.

It is the cables fault.

Everyone knows that the amplifier and cable and complex speaker load interact. However, blaming cables is a "cop out" to me. It is all too obvious that the distortion products (due to complex interaction) will be different at each end of the cable; after all one is shorted by an active amplifier - a virtual SHORT and highly dependent on the amp circuits whilst the other end is connected to the complex but higher impedance load of the speaker and its moving diaphragm(s).

The more complex the load and the less stable or capable the amplifier then the more chance of problems. In problematic combinations, slight differences in cables will certainly accentuate or attenuate certain forms of audible distortion (there is always distortion but not all forms are large enough to be audible when playing music). IMD distortion being a particular problem, as it is quite audible compared to other forms and IMD is often a product of complex interactions between amplifer and a complex load with mechanical moving parts.

This throws in to question the "standalone" or "isolated" design of many amplifiers and speakers....that they should be so badly designed in isolation. In the extreme, the speaker designer my ignore how they are to be driven and the amp designer may make the ridiculous assumption of optimization to drive an 8 Ohm resistor accurately: in this case, the two being so badly designed, as to be overly sensitive to a mere piece of wire between them. Add to this the consumer, who randomly selects to match certain items totally ignorant of how the poor amplifier is being mistreated or abused with a terrible load from a ported speaker with enormous LF bass extension!!

=> The design fault is with the speakers and amplifiers and the selected combination of the two, IMHO. The lack of a holistic view towards design and equipment selection.

Tweaking by changing cables to improve sound clearly implies that there are distortion products in the amplifier/speaker/cable complex interaction that are audible....and this is bad. Is the cable tweaking a solution? No it is a band aid, IMHO!

Yet most people incorrectly BLAME the CABLES as the cause of the problem when cables cause a significant change. And yet cables are a PASSIVE element and the LEAST complex element of the system by SEVERAL ORDERS OF MAGNITUDE.

The root PROBLEM is bad Amplifier and/or Speaker design or in rare cases a very odd choice of cable or combination of all three!

These differences can be made small through proper design and selection. And the far superior design of active speakers allow these kind of surprises to be designed out of the system - through thorough testing and design of amp and load to ensure stability, precise phase characteristics and much lower intermodulation distortion. An active speaker with a separate mid range amp only working from 380Hz to 3.5 Khz has to contend with a mere decade of frequencies and no nasty crossover)...so a much much easier job for this amp.....so no IMD distortion leaks between this frequency range and that from bass or treble (especially that nasty hard to drive bass frequencies where much amplifier instability issues occur)....so that this amp can be designed to be much more stable and low distortion over a greater SPL range and variety of music...it has such an EASY job compared to what most amps are asked to do!

Active Speakers have some serious advantages and this series of articles clearly demonstrate this by highlighting the deficiencies in conventional approaches to equipment design and selection. Actives have disadvantages too - less chance to tinker around and tailor the sound. However, active speakers do eliminate the speaker cable/amp/load matching problem mentioned here (the "effect of cables"); actives mean a lot less to worry about, which is good unless you like worrying about unknown untested complex interactions from your personal equipment choices...
Shadorne, I'm not used to seeing you respond with so many paragraphs littered with all-caps. I'm also surprised that this little cable item has led you to call for a moratorium on passive loudspeakers with an eye toward examining the possibility of an all active speaker world:]

Unfortunately, most if not all of the most highly regarded speakers in existence are passive.

Cables, themselves, do cause significant differences in sound regardless of how unsuccessful engineers are at properly understanding those differences.
I gather from the article several points. Correct me if I am wrong.

1. Amps, speakers and cables all interact and therefore the amps and speakers will change the characteristics of the cables. Cables will potentially sound different in different systems.
2. The longer the cable, the more it picks up interference, especially RFI.
3. The configuration of the cable, coax or parallel, will show measurable change in the level of interference measured.

If I am summarizing several of the many points correctly, then I propose that:

1. Reviews of cables are meaningless because they are not using the equipment that you will be using.
2. If you have long runs, you may need shielding to prevent the pickup of RFI, and maybe EMI.
3. Metal content, physical configuration, dialectric and length will all contribute to measurable differences in cables, and may give them different sounds. Therefore all cables can potentially act as tone controls, some more than others.

Did I understand the article? Did anyone else come to the same conclusions?
Dave,

Sorry for the caps - too much coffee this morning I guess,

As for moratorium on passive speakers....no I don't believe that. I agree that that the vast majority of the best speakers are passive.

I believe that for a well designed amp and for well designed speakers ( that are a suitable match) then the cables should have minimal effect (barely audible). I know many audiophiles vehemently disagree with this concept. I suspect the links in this thread to respected researchers who have discovered distortion when an amp and speaker complex load are coupled by a cable is intended to prove what many believe; speaker cables are a significant issue in home hi-fi and they dramatically affect the sound.

So my suggestion to those "cable worried people" would be to simply investigate Active Speakers - because this largely eliminates the problems with cable choice and matching amp to speaker load by leaving these critical choices to the designer with their skills and lab test equipment. I also gave justifications for why active designs will reduce this problem significantly . The most compelling argument, for those non technical minded, is to realize that the cable is almost eliminated altogether (it becomes at least 10 times shorter...an order of magnitude less important)
hi shadorne. there are two cable interfaces that you may be overlooking, namely the source to preamp and the preamp to amp. what about transport to dac. and what about line cords ?

ihave personally observed affects of line cords with respect to the above mentioned interfaces.

by the way, i am not aware of any panel that is fully active. some provide an amp to a woofer driver, but then the owner must furnish the amp for the panel.