A time coherent speaker is one whose acoustic output is a duplicate of its electrical input.
'Don't all speakers try to do that?' you might ask.
No, they do not!
Most speakers just try to reproduce all frequencies at the same relative amplitude (flat frequency response) and completely disregard proper timing. These speakers are called time incoherent.
SLANTED BAFFLE ALIGNS ACOUSTIC CENTERS
With the rare exception of single driver speakers, the only way to achieve time coherence is by physically offsetting the drivers, in our case by slanting the baffle, and by employing first order crossovers (that is the single most important sentence in this paper).
The idea of aligning the drivers in time by slanting the baffle is easy to grasp. The time consequences of crossover design are a bit tricky.
When two drivers are mounted on a vertical baffle - the place where the tweeter's sound originate,
its "acoustic center", is actually an inch or so out in front of the woofer's acoustic center. Because all frequencies travel at the same velocity, the sound from the tweeter will arrive at the listener's ears before the sound from the woofer. As you can see below, if the sound were (for the sake of graphic clarity) a square wave - the listener would not hear a square wave at all. Though the listener might hear all frequencies at the proper amplitude, the waveform is disturbed in the time domain. Hence the listener hears something quite different from what is actually on the recording.
CROSSOVERS, aka FILTERS, aka X/Os Crossover design is at least as critical as the design of drivers and cabinets, and, like it or not, grossly outweighs your choice of amps, preamps, players and wires. What's more, crossover design is a hotly debated subject so it certainly deserves your attention.
The primary purpose of the X/O is to divide the signal into frequency bands - to send bass to the woofer and treble to the tweeter. To do so it attenuates the signal in the frequencies that are not desired. The rate of this attenuation is referred to as a filter's 'order'. Filters attenuate in multiples of six decibels per octave 6dB/octave, 12dB/octave, 18dB/octave, etc. and are referred to as first, second, third, etc. 'order'. An octave is either a doubling, or halving of frequency, and six decibels means either a quartering or quadrupling of amplitude. So, a first order filter is down to 1/4 power at one octave, A second order is down to 1/16 power at one octave, 3rd order is at 1/64 power, and a 4th passes just 1/256th of the power at one octave!
Keep in mind that all that a speaker
can actually do is compress and rarefy the air around it; that is its ONLY job.
The step signal is a single, elegantly simple event - from a condition of rest, the speaker is asked to instantly compress the air, and that is all. In so doing the speaker readily reveals all that needs be known of its time domain behavior.
Meadowlark Audio comes at the problem of speaker design from a unique perspective: we insist on correct time domain performance FIRST - there we give up nothing !!
Our speakers are designed in the time domain FIRST and, as it turns out, when a speaker's timing is correct, the frequency domain just plain lays down and falls into place. Just like magic, the whole design begins to work together to create music !
Have you ever noticed that you rarely suffer from listening fatigue in the 'real world'? Even in noisy, complex environments like busy restaurants and factory floors one rarely experiences this weird form of fatigue. Live acoustic music almost never causes fatigue, even the really wild stuff like massed, blasting brass and marching steel drum bands! Understanding the mechanism that gives rise to listening fatigue requires a brief discussion of the human hearing system.
When you listen to a completely natural sound environment - the real world - each sound arrives at your ears in its natural state, and with an amplitude and phase relationship that agree because the sound was created by a real event. The mind can readily turn the signal coming from the ears into a picture of reality. We can readily perceive the location and distance of each sound around us. But, in stereo reproduction there is a huge opportunity to scramble things. If gross errors are made, try as it may, your mind cannot put together a picture of reality from the garbage that's coming up from your ears. Wire one speaker out of polarity and you'll see! As errors in sound reproduction get smaller, a stereo picture will form, though sometimes just bits and pieces. Perhaps you've heard a system that can get the singer to image, but spreads the string bass around the room. When a system works pretty well, you will perceive good imaging, soundstaging and ambiance. But unless the waveform reaching your ears looks "natural" to your mind, your mind will still have to work rather hard, though subconsciously, to put together that picture of reality.
While a stereo that destroys the original waveform may sound excellent for 20 or 40 minutes, ultimately your mind will notify you of its extra labor in the form of listening fatigue. You probably won't know why, but your mind begins to wander from the music, and finally you turn off your rig and go make a sandwich.
You've spent a bundle have a "great" sounding stereo that ends up giving you very little real enjoyment. The high end is absolutely FULL of these.
Of course, this problem is all but impossible to pick out in short listening comparisons, and does not readily lend itself to A/B testing since the last system played will almost always lose in a fatigue judging contest.
On the other hand, have you ever been swept away? Brought to tears? Washed over by waves of goosebumps? Choked up? Have you played recording after recording into the night? Has the overwhelming emotion of fine music soothed your soul? Do you forget you're listening to stereo? Does your spouse sit down and listen with you? Is listening to music the most exquisite luxury in your life?
Well for these feelings to visit you regularly, repeatably and convincingly, your stereo rig must be really, truly RIGHT. And to be really, truly right, it must faithfully reproduce the music, not just in terms of amplitude and frequency, but also in TIME !!!
When it comes down to it: You will make a choice between a time coherent speaker and a time incoherent speaker - a choice between right and not right. You'll either really love it or just learn to live with it.
For natural, quick and dynamic sounding trebles with genuine detail, not edge, Meadowlark uses a silk dome tweeter designed that is free of the notorious bite and ultrasonic ringing of the more common metal dome designs. Vocal sibilants sound like breath rushing past teeth, not bursts of noise. Fanatical attention is paid to cabinet resonance control. The result of all this is a speaker that disappears into a deep and wide soundstage.
Audax Aerogel midrange sports a cone material composed of acrylic microspheres - half the mass of paper but twice as stiff. It retains the natural sound of paper, but is remarkably fast, transparent and open. The unique symmetrical suspension behaves identically on the outstroke and instroke. This driver's transient performance is the best we've yet measured.
Dual 7" paper coned woofers from Vifa's Premium Series have about the same working area as a single 10" woofer, but since there are two huge motors instead of just one, twice the force is generated for excellent control and extension.
Transmission line bass loading completes the concept of an accurate, tight and brawny bass system that loads the drivers resistively rather than reactively like typical vented speakers - well damped and easy for your amplifier to control, dynamic bass extends down into the twenties.
The Heron is not mass produced. Each pair is carefully handmade and tested. The designer personally signs each speaker once it passes a rigorous, full power testing sequence. Standard finishes are Natural Cherry, Classic Mahogany, Straight Grained Ash, Rosewood and Ebony.
Nightingale is an easy load for your amplifier to drive and is 90dB sensitive. Excellent results can be had with a single 100 WPC amp. However, Nightingale is capable of handling up to 800W ... and using gobs of power is loads of fun!
Despite its formidable size, Nightingale completely disappears into a spectacular soundstage. The vocal range is lush and 'human' sounding, and the top end is sublime. This speaker is utterly coherent, natural and musical.
Nightingale's distinctive appearance flows directly from its function, and is the embodiment of high-end elegance and no nonsense brutality.
Our speakers are designed in the time domain FIRST and, as it turns out, when a speaker's timing is correct, the frequency domain just plain lays down and falls into place. Just like magic, the whole design begins to work together to create music !
The Kestrel delivers high end performance at a very affordable price. this easy to place, modestly sized, floor standing two-way disappears completely into a deep and well delineated soundstage. Bass extension, articulation and slam are extraordinary for a compact speaker.
specs
Quick, natural, robust, sublimely coherent, the Shearwater embodies the reasons why so many of us would rather have a top notch two way than any other kind of speaker. Naturally, the heart of the Shearwater is its woofer. This carbon fibre design from a small, but preeminent Danish maker is roundly regarded as perhaps the best 7" there is.
Heron-i's elegant architecture reveals that its form follows its function. While most other more expensive speaker lines are
blissfully indifferent to the need for correct timing, the Heron-i quietly employs deadly accurate timing and stunning swiftness to its advantage.
The very idea of reproducing the huge dynamic scale of live music - particularly in the bass - has been elusive in high end audio...until now.
The Nightingale's bass system is an outrage of over-engineering that is magnificently capable of both stunningly real dynamics and of deep extension with absolutely vicious control.
large photo