Coplanar-Coaxial Technology

Our Coplanar-Coaxial technology makes sure that bass frequencies, mid range frequencies and high frequencies all originate from the same point in space. This is not possible with traditional 2-way speakers, where the woofer and tweeter are located some distance away from each other. The main difference between the CEntrance driver and the traditional speaker design is extra clarity, precision and soundstage, resulting from co-location of the two speaker drivers within the same enclosure. CEntrance's unique Coplanar-Coaxial technology is described in detail under the "Design Approach" tab. Click to learn more.

Dual-Coil Driver

The innovative dual-coil driver behind the CEntrance MasterClass™ 2504 speakers confines the woofer and the tweeter within the same, shielded driver assembly. Mounting both drivers on a solid frame allows precise alignment of the drivers' emanating planes and ensures that all audio frequencies arriving at your ears come from the same spot in space, not from several different places. The picture on the left shows the driver assembly. You can see the tweeter connections at the top and the woofer connections towards the bottom. Both moving coils use the same magnet, a patented design. The CEntrance approach is the best possible way of making the two drivers sound like one. The solid metal enclosure further guarantees shielding from RF frequencies and results in clean sound reproduction, free from unwanted interference.

Custom Crossover Network

The crossover circuit is at the heart of any dual-driver loudspeaker. It splits the audio signal into dual frequency bands that can be separately routed to the woofer and tweeter drivers. CEntrance developed a custom passive design to minimize phase shift, frequency non-linearity and resulting distortion. The audio-grade caps, oxygen-free copper in the custom-designed, core-less coil and custom low-leakage PCB make our crossover the reason MasterClass™ 2504 speakers sound so good.

Bass Reflex Port

The bass reflex port is an acoustic amplifier that uses the sound from the rear side of the diaphragm to increase the efficiency of the speaker at low frequencies. The CEntrance MasterClass™ 2504 speakers feature a carefully-tuned bass port that ads a boost to the lower end of the frequency response allowing to make the overall enclosure smaller without compromising bass performance. Proper adjustment of the cabinet and port size and matching with driver characteristics results in a smaller book-shelf speaker with audiophile performance.

Solid Footing

CEntrance approached every little detail with highest degree of attention. The feet on the bottom of the speakers are bolted down, not glued, underscoring professional build quality. The feet contain the right amount of firm, resilient foam and offer the perfect balance of form and function. While allowing a necessary amount of cushioning, they feature a solid grip. These speakers are gentle enough to not scratch your book shelf or desktop surface yet they will not slide around during operation.

Low-Impedance Binding Posts

The CEntrance MasterClass™ 2504 speakers feature gold-plated binding posts located on the back panel for easy access. Gold plating ensures freedom from corrosion and lowers the electrical impedance of the connection. This guarantees freedom from signal loss and stable operation for years to come.

Our binding posts accommodate standard banana plugs as well as cable lugs. The connectors are clearly labeled in accordance with industry-standard practices. The positive terminal is red and is located on the right. The negative terminal is black, located on the left.

CEntrance uses the same binding posts on the DACmini PX DAC/Amplifier, which is voiced and tuned to work together with MasterClass 2504 Speakers. Click here to learn about the attractive bundle, which combines DACmini PX and MasterClass 2504 speakers.

CEntrance utilizes a unique approach in the design and construction of its MasterClass™ 2504 speakers. Their sonic difference is manifested in the precise localization of sound sources, great soundstage and tremendous presence, despite the smaller formfactor. This is all due to the innovative design of the speaker mechanism. Since the differences in acoustic technology may not be obvious at first glance, we felt that it was appropriate to spend a little time explaining the physical principles behind our design approach and compare it to the more traditional speaker manufacturing techniques. If this short tutorial doesn't make you a speaker designer, at least it will make you an informed consumer of speaker technology. That alone would make us very happy.

Why We Did What We Did

CEntrance is first and foremost an engineering firm. We love a good design challenge. Back in 2000 we started out as a technology provider to other manufacturers because we were driven by passion for innovation and design. Nothing has changed, really. From that day forward, for over 12 years we continue to be mostly about what's "under the hood". When we develop a new product, we are not satisfied until we arrive at a robust, technologically superior solution that offers a sonic benefit like no other product.

Naturally, when we decided to offer high-quality loudspeakers to go along with our DAC and amplifier products we were not satisfied with bringing to market a "me too" solution that was fundamentally the same as many other readily available products. We wanted to introduce true innovation. We knew we were ready to release the MasterClass™ 2504 coplanar coaxial speakers when we truly had something special on our hands.

Standard Loudspeaker Design

For the remainder of the article, we will refer to the word "driver" as it is used in the context of acoustics and loudspeaker technology. Here it refers to an assembly consisting of a magnet, a moving coil ("voice coil") and a diaphragm, the "engine" that makes sound by moving the air back-and-forth in front of it. This design is also known as a "dynamic driver", as opposed to the planar design.

Loudspeakers basically come in two varieties—they either have standard or coaxial location of drivers. The standard loudspeaker features a woofer on the bottom and a tweeter at the top. This is the most common arrangement in home stereo and bookshelf systems. We've all seen them. These speakers are the cheapest to make because they rely on simple drivers—separate woofer and tweeter assemblies, each designed to work with its own frequency range.

Fig. 1. Standard loudspeaker design features delayed arrival

The problem with this approach is that the low frequencies coming from the woofer and the high frequencies coming from the tweeter originate from two different points in space. The sound waves have to travel different distances to your ear and end up reaching you at different times. This means that the resulting auditory "picture" is skewed—it is distorted, since you are not hearing things together. Some sounds are delayed against the others. The larger the speaker, the worse it gets, because the distance between the woofer and the tweeter increases and with it increases the distortion due to arrival time differences between the "highs" and the "lows".

The end result? Mushy sound with disappearing sound stage, vague instrumental locations, and lack of that special feeling of "being there". This is why traditional stereo speakers will always have a hard time achieving truthful reproduction of complex music sources.

Coaxial Driver Design

A coaxial loudspeaker is an attempt to solve the problem of delayed arrival. The coaxial design locates the tweeter on the same axis as the woofer, hence the name "co-axial". Typically the tweeter is mounted on a bracket in front of the woofer, partially obscuring it. This design is frequently found in car audio systems, where space is at a premium. The coaxial speaker is shown on the diagram below. Click images for larger versions.

Fig. 2. Cut-away 3D model of the Coaxial driver

While the coaxial driver solves one problem it introduces another. The woofer and tweeter are located on the same axis, but on two different points on that axis. They are located on different planes, as referenced by the front panel of the loudspeaker. The tweeter is mounted closer to the listener and therefore the high frequencies reach the listener faster—they have about 1 inch less distance to travel. Now, 1 inch of distance may not sound like much, but it translates to the wavelength of 13.5kHz, which is not only a perfectly audible range, but also a large source of spatial cues due to echoes and reflections, which we rely on in this area to determine instrument locations.

The end result? Poor source localization and uncertain soundstage. What works for car stereos, does not work for audiophile systems. Compact - yes, good sounding - no.

Coplanar Driver Design

Enter the concept of the Coplanar driver, the best representation of a "single point source". The figure below shows that a coplanar driver not only places the woofer and tweeter on the same axis, but also locates their working surfaces on the same plane (hence the name "co-planar"). This means that high, low and mid frequencies are all reaching the listener at the same time. With a coplanar design, the arrival times are the same.

Fig. 3. Cut-away 3D model of the coplanar driver

The two figures below illustrate the concept of delayed arrival for the low frequencies compared to the high frequencies in the coaxial speaker driver. Delta t represents the delay in arrival time. The higher the delay, the more distortion at the listening position.

Fig. 4. Coaxial driver delivers high frequencies earlier

Fig. 5. Coplanar driver delivers all frequencies at once

Implementation

So why hasn't coplanar technology, which is clearly superior from the sonic standpoint, found greater popularity in speaker designs? The answer lies in the complexity of such driver. It's actually quite difficult to design a woofer/tweeter in one package. The CEntrance MasterClass™ 2504 speakers achieve just that goal. The combined driver in our speakers features two voice coils, which are driven by the same magnet and located practically on the same plane. It took many years of research to develop a driver that accommodates both voice coils on the same frame and drives them off the same magnet. The end result? The CEntrance MasterClass™ 2504 speakers redefine audio fidelity in a small package.

Fig. 6. CEntrance located the tweeter inside the
woofer for maximum linearity and lowest distortion

Fig. 7. CEntrance driver combines woofer and
tweeter in the same package

Conclusion

Congratulations for reading this far! Now you are an expert and the last thing that remains is explaining the name choice. We named these speakers MasterClass™ for a reason. In the 70s and 80's Recording and Mastering engineers started using coaxial speakers in studios and mastering facilities to achieve the purest reproduction of recorded sound. Their sound systems needed to be a notch above the best playback system money could buy. Back then, things were different and audio quality was very expensive. Today it's possible to build a mastering-quality system in a home studio.

The CEntrance MasterClass™ speakers offer a breakthrough in acoustic design. We are very proud of this technology and know that you will be amazed with the clarity, localization, soundstage and overall fidelity of these speakers.

Encore

One important note about using the MasterClass™ 2504 speakers in real homes: They truly open up if they are positioned in such a way that there is no horizontal surface right in front of them. One way to avoid the surface of the desk from interfering with the sound is to place the speakers at the edge of the desk, the one closest you, so that there is some open air right in front of the grills. If that's not practical, the other option is to raise the speakers above the surface of the desk on stands.

There is a lot to be said about speaker stands that "remove" a nearby surface. This gets rid of unwanted reflections and allows the soundstage to truly shine. With co-planar drivers such as these, that's very important as the difference is huge. Because of the ported enclosure, also try to maintain at least a foot of open air between the speakers and the wall. Same reason here—reflections kill clarity.

Happy Listening!

Michael Goodman, Chief Product Architect