In our earlier article, we covered the concept of our Legacy 1 speaker and how we used artificial intelligence (AI) to develop a unique loudspeaker.
After completing our concepts, it was time to focus on what we wanted to achieve from an audio perspective.
Our priority is Accuracy.
The flattest possible frequency response curve, fast transients, with all reproducible frequencies being time aligned.
We’re focusing on accuracy to ensure that what the rest of your audio system provides as a signal is what the Legacy 1 creates as an audio pressure wave that travels to your ears.
Usually, the human hearing range is assumed to be 20 Hertz (Hz or cycles-per-second) to 20,000 Hz. FFor perspective, low bass sounds like kick drum and organ range from 20 Hz to 100 Hz. The sizzle of a cymbal crash is near 20,000 Hz. And the human voice, when talking, is in the 70 Hz to 6,000 Hz range.
We’ve been testing Drivers, the technical term for what is commonly known as “the speaker.” For example, one or more Drivers in an enclosure make up a speaker system.
All our measurements to date have been made in “Free Air” at controlled temperature and humidity. Free Air means that the Drivers were not mounted in an enclosure (cabinet).
Legacy 1 Speaker System | Constraints
To achieve our priority of accuracy, physics and engineering dictate several constraints:
- Flat response curve:
- Currently, no single Driver can produce the full range of human hearing. That’s why most speaker system manufacturers divide human hearing into sub-bass (20 Hz to 60 Hz), bass (60 Hz to 250 Hz), mid-range (250 Hz to 6,000 Hz), and high frequencies (6,000 Hz to 20,000 Hz). Often, a high-quality system will have a separate Driver for each range: sub-woofer, bass, mid-bass or mid-range, and tweeter.
- But, the division into four or more frequency arenas brings complexity, cost, and time alignment issues.
- Also, it usually requires a large structure or enclosure to hold the various Drivers, whether single-point sources (cone Drivers) or omnidirectional sources (electrostatic panels).
- What eventually ends up happening is manufacturers develop a physically large and expensive speaker system, or they give up on some combination of accuracy, frequency range, or time alignment.
- We’ve limited the low-frequency response to 70 Hz to retain accuracy in a reasonably sized sealed enlcosure.
- Fast transients:
- When you see the term “fast woofer,” it’s simply marketing jargon. From a physics perspective, the woofer Driver’s mass is substantially larger than the one used to produce higher frequencies. It’s impossible to accelerate something with more mass as fast as a smaller mass. This means that the woofer Driver is the limiting factor in achieving fast transients, as measured in milliseconds (ms) after an input signal has been applied.
- Comparisons can be made between competing woofer Drivers by measuring their Q value. Q is a unitless measurement developed by Neville Thiele and later refined by Richard Small. It became part of the Thiele/Small parameters for loudspeakers.
- In short, Q (either measured or calculated) represents the dampening of a driver. The smaller the value, the less initial overshoot and ringing occurs. “Ringing” is another term for dampening.
- Example: When struck with another object, a bell is designed to ring for a long time as opposed to a pile of dirt that will hardly ring.
- We’re retaining accuracy by using a smaller woofer Driver with excellent dampening.
- System efficiency:
- Many speaker systems use ports, slot-loading, or band-bass enclosures to increase the bass frequency output for each increment of input power (Watt).
- To achieve our priority, we’re using a sealed speaker system to mimic the ideal enclosure, an infinite baffle. The only sound you’ll hear is when the Driver moves toward you. The sound pressure wave is contained within the enclosure when the Driver moves backward, which means that we’re discarding half of the sound produced by the Driver to increase accuracy in sound reproduction.
- Our tradeoff is that the Legacy 1 speaker will be accurate but less efficient than a system open to the atmosphere. But with the advancement of high quality, high power amplification, having high efficiency isn’t as important as it once was.
- Time alignment:
- The other issue with using multiple Drivers is time alignment. Point source speakers that use multiple Drivers (usually cones) are physically unaligned.
- Think about your voice: all the sound you produce when talking or singing is from a single enclosure: your mouth. Our hearing system, consisting of our ears and brain, is designed to hear tiny differences in sounds arriving from different sources. This helps us locate an object that’s creating a sound.
- Because of how our hearing system works, listening to a speaker system that isn’t time-aligned can be fatiguing.
- Our initial evaluations of speaker Driver configurations indicated that using a two-way co-axial Driver would inherently provide a good starting point for accurate time alignment.
Our solution | Two-way, co-axial Driver
Our carefully engineered enclosure will have fast transients and good time alignment. But to keep the cabinet a reasonable size and cost, the frequency range will be approximately 70 Hz to 20,000 Hz. You’ll need to purchase a subwoofer system to reproduce the 20 Hz to 70 Hz frequency range.
Fortunately, sounds below 70 Hz aren’t perceived by humans as being directional. That’s why humans find it challenging to tell the direction of an object or critter that creates a low-frequency sound like a thump, or even when whales talk to each other in the ocean.
The next step was to purchase a bunch of two-way, co-axial Drivers and test their characteristics, including frequency response and efficiency.
After we concluded all of our testing, the best Driver was the Focal EC 165 K, which is hand-made in France.
For example, the measured Q for the woofer Driver in a Focal EC 165 K is 0.593 compared with a competing woofer Driver of the same equivalent piston diameter, which was 0.821.
Q coupled with the measured Free Air Resonance (62.85 Hz for the Focal EC 165 K compared with 71.73 Hz for one of the competing woofer Drivers) means that the enclosure volume can be smaller while producing the same bass response.
When comparing the Focal woofer Driver to a competing one, reproducing a flat response down to 70 Hz requires an enclosure volume of 10 cubic feet (283 liters) compared to 220 cubic feet (6,230 liters)—a vast difference.
The difference is primarily due to the materials used for the cone and voicecoil. As an aside, the difference in cost between the Focal driver system and most competing ones is a factor of two.
We’re now designing, engineering, and analyzing several sealed test enclosures of various volumes to determine if the driver measurements made in our testing facility correlate with the driver mounted in an actual enclosure.
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Legacy 1 Speaker | Journey
Join us as we take you on the journey from the written concept in this article through our speaker’s design, engineering, and crafting. It’s intended for everything from conventional stereo systems playing vinyl recordings to the latest Dolby Atmos surround sound systems.
Our mission is to create functional art you can enjoy today that qualifies as part of your legacy to be given to a trusted family member or friend.
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