Q: Why another loudspeaker company?
A: In brief, to bring to market loudspeakers with BBC heritage roots that use new design patterns.
We are acutely aware that commonly available consumer loudspeakers are a mature technology, with many well-executed choices. A majority of consumer loudspeakers fall into a few common design patterns: they use one or more “dynamic drivers” that cause the air to vibrate, the drivers are placed in a sealed or vented cabinet, often a wood-fiber composite such as medium-density fiberboard (MDF), and passive electrical components equalize and balance the sound among the drivers. Many modern drivers are of high quality, and the acoustical, mechanical, and electrical engineering principles for the overall design are well understood. Yet each year loudspeaker companies offer some purported improvement - perhaps an exotic new material in the speaker diaphragm, a refinement to the electro-mechanical design of the drivers, a new aspect to the construction of the cabinet, etc. - all while remaining within the constraints of the same basic design pattern. Foxears Audio was started to offer design patterns rarely available to the home consumer, and to perhaps nudge the industry towards use of these new designs.
Q: What do you mean by a design pattern?
A: The term design pattern originates with architect and professor Christopher Alexander, a principal author of the highly influential book “A Pattern Language.” Michael was familiar with the term as adopted for computer programs, and the analogy with loudspeaker designs was clear.
We use the term design pattern to mean the approximate overall dimensions of the speaker, the number, kind, and sizes of the drivers, the spatial arrangement of the drivers, and importantly, the approach to signal filtering. Many of the virtues and limitations of a loudspeaker are determined by the basic design pattern. The most common and arguably cost-effective design pattern today is a 2-driver vertically oriented “passive” loudspeaker meant to be placed (ideally) on a stand and with about a 7” cone bass driver and a 1” dome tweeter. There are many many examples of speakers fitting the 2-way/passive/stand-mount design pattern. All design choices involve compromises and trade-offs: size, cost, complexity, and so on, and the basic design pattern determines much of what can be achieved. A small single driver loudspeaker is best suited for modest volumes, the lower bass will be somewhat limited, and the higher treble frequencies may be less refined, but it may have special virtues in the mid-band frequencies and for close-up listening. A larger speaker may not “disappear” the way a small stand-mount can, but it can produce deeper bass and fill a big acoustic space with ease.
Q: So what’s new in the design patterns of Foxears Audio loudspeakers?
A: In brief: the physical arrangement of drivers, the choice of driver dimensions and how they “scale” as the loudspeaker model increases in size, and hybrid active implementations with external active filtering and external amplifiers. In our debut offerings (Wynton and, soon, Ellis), the Wynton mini-monitor offers an unusual driver arrangement and it sounds nearly the same in either a horizontal or vertical orientation; the larger but still compact Ellis is a 3-way stand-mount with hybrid active bass.
Q: BBC heritage, whatʼs that about?
A: The British Broadcasting Corporation (BBC) had a tremendous research program in the 1970s and early 1980s to improve the consistency and tonal accuracy of loudspeakers used to monitor broadcast recordings. The BBC research team regularly compared the sound produced by their loudspeakers in a broadcast control room against live studio performances, resulting in loudspeakers with an honest, natural sound rarely equaled - even today - by other designs.
Q: What gives your speakers a BBC heritage?
A: The BBC heritage of our loudspeakers lies in the designer (Derek Hughes), in the design/development methodology, and in the approach to the cabinet construction. While we make extensive measurements and use modern software to help design the speakers, a keen ear is the ultimate arbiter of the result. After initial measurements, we judge the tonal accuracy of our speakers by listening to known recordings of the human voice, especially speech. Derek Hughes has a long involvement with BBC-heritage loudspeakers, and applies the same rigorous procedures for developing and evaluating our loudspeakers as he has previously done for BBC-licensed designs, utilizing recordings he made while at the BBC. The cabinet construction is also a BBC-inspired approach that applies materials and constructions to ensure a “quiet” cabinet that minimizes the coloration of the sound.
Q: What’s a crossover and why does it matter?
A: A major contributor to the sound of a multi-driver loudspeaker, often hidden in the loudspeaker, is the “crossover” or filter network. In a 2-way (2-driver) loudspeaker, the filter network removes the high frequencies from the signal to the woofer, and removes the low frequencies from the signal to the tweeter. The filter network also serves as a kind of frequency equalizer, but more about that later.
Q: Active versus Passive - What’s the difference and dichotomy?
A: In a passive loudspeaker, (usually) a single external power amplifier sends the electrical signal to all the drivers, and passive electrical components (capacitors, inductors, resistors) filter the signal after the amplifier but before each driver. In an active loudspeaker, each driver may have its own power amplifier, and the signal is filtered by powered or “active” electrical components before the signal goes to the corresponding amplifier. Said one more time:
passive speaker, filter after the amplifier (with passive components)
active speaker, filter before the amplifier (with active electronics)
The present and common market dichotomy is:
passive loudspeaker => separately purchased amplifier, generally one amplifier channel per loudspeaker
active loudspeaker => amplifiers (often class D) inside the loudspeaker, generally one amplifier channel per loudspeaker driver group (e.g., one amplifier channel for the tweeter, one for the midrange, and one for the bass)
The passive/active dichotomy often seen in today’s consumer market is not a necessity. Engineers can (and do) argue for the technical advantages of active systems, but hi-fi enthusiasts may prefer passive loudspeakers because they want to choose the electronics stack, including the power amplifier. Said another way, for hi-fi enthusiasts, choosing the electronic components (dac, pre-amp, power-amp) that best complement their loudspeaker is part of the enjoyed process of creating the best system for their taste and budget, and allows the system to change (“upgrade”) in the future by selecting different electronics. At Foxears we believe there is an opportunity to find a middle ground in the active/passive dichotomy, and achieve a different, and we believe better, set of trade-offs with hybrid active systems.
Q: What are examples of a hybrid active loudspeaker system?
A: Two examples: one example is to apply active signal equalization before the power amplifier as well as to use passive filters after the power amplifier. Such an approach can increase the overall sensitivity of the loudspeaker, and improve the bass response. Another example would be to have a bi-amplified 3-way loudspeaker with passive filtering between the midrange and tweeter, and active filtering between the bass and midrange.
Q: What are the advantages offered by active bass?
A: In a passive loudspeaker system, the bass and lower midrange frequencies are naturally weaker than the mid and higher frequencies for a few reasons, including the natural uncorrected response of the driver and the effects of the sound interacting with the cabinet baffle (at low frequencies the cabinet is narrower than the sound waves so less of the sound goes forward). The loudspeaker designer must use circuit elements to passively reduce the mid and higher frequencies to make the bass frequencies relatively stronger. Balancing out the bass increases the number of passive crossover circuit components, makes the electrical load for the amplifier more complex and “reactive,” and increases the needed amplifier power. There are audio enthusiasts who oppose active “equalization” of the audio signal before the amplifier yet happily apply active RIAA equalization (via a phono preamp) to boost/correct a vinyl turntable’s analog signal before the amplifier. Similarly, it may not be recognized that a passive loudspeaker’s “crossover” very much serves as a frequency equalizer, and one which may add more distortion than an equivalent active equalizer used before the amplifier.
When active equalization of the bass (before the power amplifier) is part of the loudspeaker’s design, and not just a means to exaggerate the bass, the passive crossover can be simplified, and the bass response can be improved and extended. If one goes further to actively low-pass filter the bass signal, and use a separate amplifier for the bass, then the dedicated bass amplifier couples directly to the bass driver for better (“tighter”) control of the bass frequencies. Actively filtering the bass signal can reduce the distortion from a passive electric circuit in the lower frequencies. One’s listening room can have a big effect on the sound, especially the bass response. With a digital (DSP) implementation of the signal equalization and filters, room compensation for bass frequencies can be readily incorporated.
Q: When a 3-way has active bass, isn’t it just a 2-way loudspeaker with a built-in subwoofer?
A: It depends on the implementation. Subwoofers are specialized to cover the sub-bass frequencies - below 40 Hz - and perhaps to assist the main speakers up to around 100 Hz. Some loudspeakers do have a built-in subwoofer (and amp) and the “crossover” or transition to the midrange occurs around 100 Hz, and that’s a different design pattern. A midrange driver that goes down to 100 Hz is more of a mid-woofer and is less optimized for the upper midrange. Our design choice allows the midrange to be more of a pure midrange with a smaller diameter cone, unburdened by a need to produce mid-bass, and also with benefits for the blend with the tweeter.
Q: Tell me more about the cabinets - aren’t BBC loudspeaker cabinets thin, poorly braced, and designed to resonate for a warm sound?
A: The traditional BBC loudspeaker cabinets are a different approach from thick wall and heavily braced cabinets, which can resonate in the crucial upper midrange. In brief, BBC loudspeaker cabinets use thin but stiff birch plywood walls damped by heavy materials like bitumen, as the vibrations of a thinner panel can be more effectively damped than those of a thicker one. Done well, the “BBC construction” is highly effective at damping panel resonances in the critical midrange, but an unbraced cabinet might add coloration, perhaps euphonic, in the mid-bass.
Foxears Audio cabinets are an innovative variation on BBC cabinets, the cabinets are substantial and use modern vibration damping techniques. Considerable attention is given to constructing cabinets with the goal of minimizing vibrations, especially of the sidewall panels with their large surface area. If the large cabinet panels vibrate, they act like secondary speaker drivers and produce undesirable sound, and that detracts from the clarity and accuracy of the loudspeaker.
While externally the Foxears cabinets look like simple boxes, internally things are more complex. The cabinets are constructed from high quality dense fiber board with inherently good damping characteristics, with double layer panels for the front baffle and the back. The critical cabinet side panels are then damped in two ways. First, and for larger cabinets, a centre brace stiffens the cabinet longitudinally, yet it is spaced from the side walls by a high loss mastic, giving good initial control over the main panel resonances. The remaining wall area is additionally treated with a constrained layer damping panel, resulting in a suitably inert end result. In addition to damping the vibrations of the cabinet walls, two layers of standing wave damping are used for the internal volume . The first damping layer is of ‘A grade’ acoustic compressed fibre applied on the inside of the walls, and then a second layer of softer material fills the cabinet cavities.