Archive for November, 2012

Ken Rockwell knows nothing about audio

I don’t know as much about camera gear as he does, but when it comes to audio, he has as much clue as I do about cosmetics. He represents some of the greatest over-simplification of everything, and the biggest problem we have with the I-read-it-on-the-internet-and-now-I-know-everything attitude that’s so common these days.

Take this post for example.

“iPod and iTunes sound completely transparent (identical to the source CD) at the right bit rate.”

He goes on to suggest that 128k VBR is sufficient.

I’ve been in this industry long enough, and listened to enough systems to tell you that even through total blind tests, you can pick the difference between a 160k VBR and a CD (going through the same DAC) without having to so much as listen.

A number of years ago, my 74 year old mother came into our testing room one night. She had no idea the difference between a speaker and an amp let alone mp3 and CD. Her response when we switched mp3 over to CD was along the lines of “oh, that sounds much clearer”. Take into account that, this was a woman who casually walked into the room after a dinner, without knowing what we were testing or the fact that we were testing, without having being asked for her opinion, had poor hearing due to her age, had no interest in hifi or sound quality and had barely noticed that we had switched something over. She walked in to see what we were doing, listened to 30 seconds of music in passing, and mentioned this, in passing.

We certainly were using some of the highest quality gear around. The CD was ripped using EAC and lame.

I hate it when the ignorant over-simplify and assume things because they’ve read about it and deduced it from their 2 minutes of experience. There’s a reason why a great many still use vinyl over CD, and CD over mp3. The difference is not only measurable, it’s noticeable (if you’re not a crass fool, that is).

Ken Rockwell, in the spirit of this way of thinking, splashes words like “the greatest…in the world” and “the best…”. “The best” implies that you’ve sampled everything else. He hasn’t. Not by far.

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Real life HDMI cables

After my previous post on whether HDMI cables make a difference, I’ve been receiving endless emails on the subject.

Here’s what most websites will say on the matter (example).

- Cheap cables work 100% as well as expensive cables (note, 100%).

- HDMI cables are akin to printer/ethernet/other computer cables.

- Short HDMI cables will have zero (note, ZERO) errors.

- Long HDMI cables will need to be better quality than shorter ones.

I giggle to myself everytime I read some of these pages. Their own statements are contradictory. If, short HDMI cables have zero difference then why suddenly does a longer cable make a difference? What constitutes “long” anyway? Does a 5m cable need to be good quality? What about a 6m one?

It’s amazing how people are STILL comparing HDMI cables to computer cables. HDMI is a one-directional protocol, compared with a completely different system of communications used by computers. Someone who makes this statement, in my books, is instantly discredited as being an “expert”. It’s a stupid thing to say.

Most will still go on to say something about buying from ebay being a bad idea. I wonder why? If they’re all the same and have zero loss, then what’s the issue?

The internet is full of people in forums complaining that their $2 ebay cable doesn’t work or gets pixelated. Google it. Again, I’m not for the “high end” HDMI cable, but it’s so naive and stupid to just plainly dismiss all HDMI cables as “error free” and “the same”.

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Speaker Cable Thickness Does Not Matter

Go to any store, ask any bunch of posters in a forum, read any hifi article off the web and they’ll tell you that the thicker the speaker cable, the better, because it has “lower resistance”.

In the 60s and 70s, when hifi cables were commonly made of wire too thin to be considered speaker cable, there was certainly some truth to this.

These days, even the bare minimum cable is thicker than 20 AWG, and believe it or not, speaker cable thickness makes almost NO difference to sound quantity, and absolutely ZERO difference to sound quality.

Why?

1. Wattage does not matter

Let’s take a 20AWG cable, a microbe in speaker cable terms these days. A typical copper 20AWG cable has a resistance of approx 1 ohm per 100 foot length (a fairly long standard use length in domestic hifi).

Resistance per 1000 feet

Typical resistance per 1000 feet

A 1 ohm resistance in an 8 ohm system drops power by 11%. A 1 ohm resistance in a 4 ohm system drops power by 20%.

Sounds like heaps? Well, considering that this is possibly the worst case senario, no. A 100 foot long run through 20AWG cable, using 4 ohm speakers, will give you just 20% power loss.  What’s 20% power loss in real terms? Well, of course, you already know that wattage does not matter, right? And how little a % change in power affects sound levels? Even halving the power reduces the sound level by a mere 3dB, or 3% on typical 1 to 100 log-scaled volumn controllers.

And we’re really talking worst case scenario. If you’re using 17 AWG cable into a 15 foot run driving 8 ohm speakers (more typical application), you’ll end up with so little loss that it’s not even worth the decimal places.

2. Resistance causes zero loss in sound quality

This is far more important than the first point. Power and power delivery is easy to control. You can always turn up the volumn, buy a more powerful amplifier, buy more sensitive speakers. But what’s the important factor that “beginner” enthusiasts miss?

The fact that sound quality is not affected by resistance.

This is the reason a 100W amplifier could cost $200 and another $200,000. Why are high end amplifiers not all 1000W? They’re made for accuracy, not power.

Similarly, a good speaker cable has qualities which colour the sound much less than a poor one.

Everyone who’s taken high school science knows a little about resistance. V=IR, P=IV, etc. What you don’t realise is that in the real world, there is a whole other dimension of force that affects sound quality more dramatically than anything else. It’s called “reactance”.

Reactance and the behavior of reactance is the real dark force in what determines a quality speaker cable. A cable with low resistance can have high reactance, and as a result, not only be detrimental to sound, but add to the impedance of the wire. What’s impedance? We’ll get to that later. Only reactance colours the sound, and reactance only happens in high frequency (higher than the zero hz used to measure resistance). Resistance only has an effect on power. It simply makes everything a smaller version of itself. Reactance, on the other hand, can convert certain frequencies into others. Reactance introduces more frequencies, ones that were never in the original signal. Reactance behaviour is also relatively unpredictable when taking into account the internal behaviors of connected equipment.

3. Impedance is much more important than resistance

If you notice carefully, point 1 had calculations that never even considered reactance (much like the rest of the world).  But reactance has an equal affect as resistance does on power delivery. A speaker cable with near zero resistance could, in theory, be substantially detrimental to power output due to reactance.

Impedance is the combined reactance and resistance of the cable. Impedance is the “real” resistance when an AC signal is passed through the cable, and because measurements for speaker cables are only ever done in DC, you never know what the impedance might be.

A speaker cable with tiny resistance can, if designed improperly or used incorrectly, be more detrimental to both power AND sound quality than one of much higher resistance. And don’t think that any cables are immune to this. I’ve seen even “high end” cables being passed as quality cables when they’ve clearly not been made with impedance reduction in mind.

Conclusion

I admit, the industry is full of people selling ghosts as gold and chalk for cheese. But don’t think that there’s no truth to “quality speaker cable”. A speaker cable isn’t better simply because it’s fatter. There are thousands of reasons why certain designs can, and do, make a better cable. And this is just the tip of the iceberg in the weird and real world of analogue electronics.

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