Tuesday, July 3, 2012

Two Audio Lessons from Formula One Race Cars

I have always admired Formula One race cars.  These sleek, ultra-light, monstrous acceleration, and sexy vehicles are in a word unique. Engines instead of growing larger have actually become smaller since the weight-to-horsepower ration is still climbing, and total power per pound is what makes one go fast, regardless of displacement. For example, the engines in this year's vehicles are 2.4 liters compared to the 3.0 liter engines of the previous vintage, and next year the size drops to 1.6 liters. It appears that going fast has a new face.

So what are the lessons one can apply to audio from what directions Formula one? There are many if you pull back and look at these issues from 10,000 feet.


First and probably the most important lesson is that to go fast you need a lot of power and in audio, to accurately reproduce an instrument, you do likewise (need a lot of power).

But the power you may be thinking of does not necessarily come from the amplifier alone. Rather, what is important is that the entire system (speakers plus amplifier) has the capability of generating the sound pressure desired. So the ability of your system to recreate accurate music is a function of how loud you listen to it and the louder you want it to go the more insane these power requirements become.

For a speaker-plus-amplifier system to create loud music in an undistorted way, it can be done in two ways:
  1. Use inefficient speakers (say 82dB/W/m sensitivity speakers) and a huge power amplifier (say 512 Watts of power), OR
  2. Use efficient speakers (say 99dB/W/m sensitivity) and small amplifiers (say 8 Watts of power)
The theoretical loudest sound you can achieve (at one meter) is exactly the same from both systems in the above example (108dB) before either amplifier is driven into clipping (the point where distortion rises exponentially). 

What determines the clipping point is the crescendos compared to the average acoustic power (that is, the peak demand power). Pianos are notorious instruments for sucking the blood out of an amplifier, especially in the upper harmonics regions.  So although you may be listening to middle C at an average level of say 80dB at one meter, peaks can occur that demand one hundred times that amount of power for a brief period of time. So if you were demanding 1/2 Watt at 80dB, you would demand 50 Watts momentarily.

What you hear when the demand rises and your amplifier cannot keep up with the demand is audible distortion. There will be a noticeable point to where this distortion becomes objectionable and so you back down the volume control to compensate. Sensitivity to distortion is more easily tolerated at lower frequencies and less tolerated at higher frequencies. But even at a lower average volume level, your amplifier may still be clipping, you just have trained your ears to tolerate it.

Another lesson is that weight in a Formula One racer slows down the car. So weight is also a bad thing in speakers.  Weight should also be kept as low as possible while maintaining structural integrity in the mass of the speaker cones themselves.  Making something too light makes it flimsy so there is a compromise that must be made, especially at low frequencies. But in general, a lighter cone will sound "faster" than a heavier cone.

What one perceives in lighter cones is its transient response, the ability to react quickly to change. It's the clear tinkles - the inner details - and the snappy bass that makes the difference to your ears. What your ears are telling you is that the system's overall distortion is lower and it sounds more like the real thing.

Transient response is two fold: to start moving when the amplifier tells it to go, and to stop moving when the amplifier tells it to quit.

To start fast is a function of two amplifier specifications (ignoring for the moment the speaker wires):
  1. The speed (slew rate) of the devices used in the amplifier (higher means faster)
  2. The ability to dump a lot of current (a big power supply and very low impedance circuits)
To stop fast is a function of two amplifier specifications:
  1. The damping factor (the "brakes" where higher is better)
  2. The impedance of the power supply (lower is better)
Weight determines how fast something can be started and stopped, so it takes more energy to do both.  the lighter the cone weight, the more accurately the cone will track the electrical signal.  But there is a trade off in weight where at some point the cone will undulate and break into sporadic resonances on its own.


When it comes to Formula One race cars, going fast means keeping the ratio of weight to horsepower low. For example, if you want your car to go 200mph, you must have a car that weighs under 3,000 pounds and has an engine that can develop over 500 horse power. This gives you a ratio of 3,000:500 or 6:1 or four pounds of mass per horse power. Formula One race cars weigh 1,367 pounds (including the driver) and the 2006 Toyota engines develop 740 HP for a ratio of less than 2:1. If you add more weight, the ratio goes up; if you reduce the power, the ratio goes up. In either case, the top speed goes down.

I think you get the idea now that it takes more power to push something heavy as fast as something that weighs less with a less powerful engine. This same lesson can be applied to audiophiles: to have your system be as accurate as it can be, these two factors must be considered.

So what is your personal weight-to-horsepower ratio preference for your playback system? Are you a fan of really loud music or clear, dynamic music? Can your audiophile ears tolerate sluggishness at the expense of transient response or do you prefer pristine clarity? Understanding these ratios as they apply to audio components can help you achieve what you desire.

If your system sounds fantastic at low volume levels, BUT you want it to go louder, adding more power may help (remember, too much power can toast your speakers). But with electronics, there are other ways to help with this as we will see soon.

Yours for higher fidelity,
Philip Rastocny

I do not use ads in this blog to help support my efforts. If you like what you are reading, please remember to reciprocate, My newest title is called Where, oh Where did the Star of Bethlehem Go? It’s an astronomer’s look at what this celestial object may have been, who the "Wise Men" were, and where they came from. Written in an investigative journalism style, it targets one star that has never been considered before and builds a solid case for its candidacy.


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