I am often asked if there’s a minimum volume level for speakers. It’s a valid question prompted by observation. If the level of the system is too low the sound seems weak and lackluster.
Of course, there are a few explanations for this starting with the Fletcher-Munson curve.
The Fletcher-Munson Curve illustrates an interesting phenomenon of human hearing. When listening to music, the perceived loudness our brains hear will change at a different rate, depending on the frequency. At low listening volumes, midrange frequencies sound more prominent, while the low and high-frequency ranges seem to fall into the background.
At high listening volumes, the lows and highs sound more prominent, while the midrange seems comparatively softer. Yet in reality, the overall tonal balance of the sound remains the same, no matter what the listening volume.
The answer to the original question has to be qualified with circumstances. What are you hoping to achieve? If background music is what you’re after, then the answer is “no”, there’s no minimum level for speakers. The Fletcher-Munson problem can be solved with EQ if you have that available.
Perhaps more important is the notion that for serious listening there is a definite minimum listening level. That setting depends on the room and type of music being played. How do you tell if it’s the right level? Image size.
That’s a subject we’ll cover tomorrow.
Kevin in Wappinger Falls New York (wherever that is) asked me an interesting question recently.
“Arnie Nudell popularized the line source loudspeaker design and many of his most revered Infinity speakers such as the Quantum Line Source, the IRS 1B, the IRS V, and the Genesis 1 (and apparently at least the two larger members of your forthcoming AN series loudspeakers) are all line source designs. Why don’t we see more line source loudspeaker designs? Is it strictly due to the cost because of the many more drivers, the larger cabinet, the increased manufacturing labor cost – or are there other attributes that have made them less popular?”
This is a really good question and one we don’t talk about much. Perhaps it’s a good idea to first get on the same page. The classic two-way or three-way loudspeaker has two or three drivers in a box. The multiplicity of drivers—tweeter, midrange, woofer—is needed to break apart the frequencies so each driver only has to handle a specific range: tweeters handle the higher frequencies about 2kHz and the woofer handles everything from that point down.
A line source handles the frequency divisions in exactly the same way—tweeters, midrange, and woofers—but instead of relying upon a single driver for each range multiple drivers are instead employed, typically with a line of many tweeters and sometimes many midranges. The advantages of multiple drivers in a line are manifold: each driver has fewer demands and the waveform comes out in a long, vertical, cylinder rather than a single driver’s ever-expanding circular wave.
The advantages of a line source vs. a point source can be summed up fairly easily. A point source sound radiates in all directions from the driver and quickly loses energy as it floods the room in a 180˚ plane. Worse, this expanded radiation pattern hits the ceiling, walls, and floor and reflects back into the room out of synch (time) with the initial launch. Only those listeners in a narrow sweet spot get to enjoy the best sound. A line source radiates a more focused pattern in the shape of a tall vertical cylinder that, above about 500Hz, has nearly no floor, ceiling, or sidewall reflections to dissipate energy and add to sonic confusion.
All that said, tomorrow we’ll look at some older Infinity designs.