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Parameters and Efficiency - Whats the deal with that?

Updated: Mar 31



This is a very telling video that clearly explains the limitations of physics that T/S parameters are up against.

"If you want low frequencies you need a lot of movement in the voice coil". - A.N Thiele, a direct quote from this video by Mr Thiele who invented T/S parameters. Recorded in the 90's, this video candidly verifies the legitimacy of designing to a minimum stroke standard, that is usable, within defined fidelity boundaries, and exhibits the least reduction in the various aspects of efficiency that the driver uses to produce said stroke.

Now the question becomes, how do we keep these parameters stable through all of the changes in electrical behavior, magnetic behavior, and suspension behavior through that movement? By chasing efficiency.

As we have progressed in audio as a company that specializes in speakers that do exactly what Thiele said needs to happen to produce low frequencies, we define the term efficiency as; "maintaining stability in all encompassing areas where an inefficiency can exist." This reduces negative effects in all areas of inefficiency, not just dB per Watt applied power.

The key point stated in this video was that these parameters were devised at a time when 15 watts was a tremendous amount of power, and this is a far leap from today with 500 watt per channel systems and especially in bass where thousands of watts per subwoofer is the norm. Thinking of the conservation of energy, it makes sense to us that the efficiency curve should be more important today than it has ever been with HT systems hitting thousands of watts as an entry point. What effect do these thousands of watts have on a speaker driver? Is the efficiency curve linear? Does it scale to an expectation of travel with nothing affecting the rate of change? The law of the conservation of energy says this is impossible.

What efficiency means is that if the parameters Thiele and Small postulated shift in the right direction due to the law of conservation of energy and are perfectly stable, then you will have linear efficiency over the bandwidth and over the amplitude. In this case efficiency is the opposite of compression, however, compression is inefficiency.

Now if these parameters shift more than what any one aspect can accommodate for with either the inability to overcome suspension compliance or excessive heat being the result, then you will have non-linear efficiency in the form of Intermodulation effects, Compression effects, and Harmonic distortion, and this is why you absolutely need stroke to produce bass and maintain bandwidth with your desired design amplitude.

Now that I have lost you, what this means is that there is such a thing as Parameter Limits, where the parameters of the driver will deviate from their design to such a severe extent that they are no longer effectual, reliable, or even worth designing around. The questions become; Where is this limit? And what is the definition of this efficiency limit? LDLC answers this perfectly with full utility and reliable design parameters.




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