The NBS Reference Monitor
LoudSpeaker Systems are an original design by Walter Fields, the designer
of NBS Audio Cables.
Our currently available LoudSpeaker Systems are:
MONITOR III
PYRAMID JUNIOR PYRAMID
SIREN AND THE ONE
SIREN AND THE SARCOPHAGUS
WHITE PAPER: THE NBS PYRAMID PYRAMID JUNIOR & MONITOR III LOUDSPEAKER SYSTEMS
BACKGROUND
NBS Cables has been in the serious high-end audio business for over 16 years.
In that time Walter Fields, its owner and principal designer has led the way in high-performance cables even before the general recognition that they were an essential part of any really high performance system. Early on NBS produced a novel loudspeaker system based on the premise of indirect radiation of the sound into the room. That has remained the hallmark of all NBS speaker systems.
NBS has also presented a very high-end power amplifier (at CES2000) which was widely praised but could not be moved into production because of supply problems from the Russian manufacturer who was the sole source for the output tubes. NBS also currently produces a series of high performance AC power conditioners for audio and instrumentation systems.
The loudspeakers to be discussed are an evolution of design concepts originally explored in the NBS Siren and NBS Sarcophagus systems.
PURPOSE
We make loudspeakers to enjoy music. The technical means to accomplish this are beside the point if they fail to connect the listener to the essential heart of the music. All the NBS loudspeakers are somewhat unorthodox in configuration because the simple truth is that "blow-it-out-the front" rectangular box speakers generally don't deliver the goods. To serve the PURPOSE of connecting to the MUSIC, the NBS loudspeakers are necessarily different from the average speaker.
DESIGN APPROACH
The design begins by identifying the critical aspects of loudspeaker performance.
These are:
Wide frequency response Low distortion High "speed" (transient response) Big dynamic range
Convincing spatial presentation (imaging)
In addition, the system should look good, be very reliable and be built to last.
- Wide frequency response and low distortion are fairly straightforward to achieve in a 3-way speaker system. The issues of apparent "speed", dynamic range and imaging are equally serious and much more difficult to conquer. The attribute of a speaker commonly called "speed" is revealed when reproducing percussion, piano and other "quick" sounds. It can only be accomplished by driver systems capable of high acceleration of the diaphragm(s). This, in turn, requires that the speakers' motors are capable of very high force in comparison to the mass they are required to move. Remember from high-school physics that acceleration = force/mass. The accurate reproduction of dynamic range, i.e. the contrast between loud and soft, is absolutely crucial to the impression of realism. Unlike errors in frequency response or small amounts of distortion, which can occur naturally, compression of dynamic contrasts is purely a technical artifact and has no counterpart in nature. Hence, dynamic compression seriously compromises the sense of reality. Dynamic compression is very difficult to overcome, ordinarily requiring heroic driver design and/or the application of acoustic techniques such as horn-loading.
- Spatial presentation, or imaging, is the ability of the stereo loudspeakers to convince us that the apparent origin of the sounds we are hearing is not in the speakers. Rather, we should perceive a "space" within which the music occurs in both width and depth which is not tied to the visual location of the speakers.
Having identified and described these critical items, we must conceptualize a design which will address them.
- Frequency range, distortion, "speed" and freedom from compression are addressed mainly by the overall system arrangement and by the choice of the individual drivers. All NBS loudspeakers are 3-way designs. This insures that each driver is operated only in an appropriate frequency range. By doing this the full rating of the individual drivers can be exploited. The individual drivers are not designed by NBS but are procured in the OEM market. The selection of these drivers is critical to the success of the design and will be discussed later.
- Spatial presentation is affected by the drivers, but it is their arrangement which determines the properties of the completed design. Indirect radiation has always been a hallmark of NBS loudspeakers and of many great designs over the decades. Other designers who have advocated this approach are G.A. Briggs (Wharfedale in its golden years), Stuart Hegeman (Eico and Harman Kardon in the 50s and 60s), Victor Brociner (Brociner Labs), Col. Ranger (JBL Ranger Paragon, Metregon and Minigon) and of course, Amar Bose.
SOLUTION
The configuration of the Pyramid and the Pyramid Junior is unusual in that when viewed from the front, no openings or speakers are apparent. The woofer faces the floor, the midrange apertures are on the sides and the tweeter is in back. All the sound reaches the listener by indirect paths. Because of this, the room reflections are properly excited by the speakers and are, in fact, required to produce the proper imaging.
The important aspect of this philosophy is that no reasonable room needs to be tampered with in order to achieve good results. Many speakers have such colored off-axis response that it is necessary to "kill" the room reflections through acoustic treatment. This treats the symptom, not the disease. The problem is with the speaker, not the room. If the room has been "killed" it will be necessary to "un-kill" it for an indirect radiating speaker such as the Pyramid. When this is done, the result will be superior imaging over a very wide area. So now you can live in the room and have music too.
TECHNICAL MEANS
As mentioned above, the driver selection is critical. In all the NBS loudspeaker models, all the drivers are manufactured by the Professional Products Division of JBL. In the Pyramid, the three transducers are possibly the best of their respective kinds in the world. It follows that they are not inexpensive. The driver cost alone in the Pyramids exceeds the entire cost of goods for many $20,000+ speaker systems.
The woofer is a JBL 2235H, 15" unit in a sealed enclosure. Sealed systems invariably have better bass articulation than vented, or bass-reflex systems. By placing the driver close to the floor, the reflection dip which impairs the mid-bass performance of many systems is completely avoided. In our experience this is the most musically satisfying woofer we have ever heard. Because it is used near the reflecting plane of the floor, it has a practical sensitivity of 96 dB/Watt, which sets the sensitivity for the whole system.
The midrange is a JBL 2490H compression driver loaded in a 25" horn structure with conic expansion in a ratio of 2:1. This stupendous driver applied in this way has a raw sensitivity of over 105 dB SPL/Watt.
The tweeter is a JBL 2402H ring radiator. This is the modern version of one of the most classic horn tweeter designs. The horn is circular and there is no explicit diaphragm. The throat of the horn is driven by the edge of the voice coil. The response is very extended and the sensitivity is 110 dB SPL/W.
All these drivers have extraordinarily powerful motors. In the midrange and tweeter, exotic materials and designs give the lowest possible moving mass, hence very high acceleration (as discussed earlier).
The crossover uses the simplest topology that will do the job. The components are of the highest quality and comprise litz-wound air-core inductors and film-dielectric capacitors.
The cabinet shape of the pyramid ensures that diffractions around the cabinet are smoothly distributed in frequency. This is especially important at high frequencies, so the pyramid geometry is retained near the tweeter and midrange apertures of the Pyramid Junior.
In all models the construction is of 1" thick material throughout and extensively braced (these are powerful systems).
The Pyramid Junior uses exactly the same midrange and tweeter drivers as the Pyramid. The woofer is the 12" counterpart of the 2235H, the 2206H, to allow a smaller, simpler cabinet. The Monitor III uses the 2012H 8" midrange and the 2206H 12"woofer.
SPECIFICATIONS & PRICING
PYRAMID: $75,000.00 PYRAMID JUNIOR: $45,000.00 MONITOR III: $25,000.00
| Pure Music. |
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| Sensitivity: |
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96 dB SPL/1 Watt @ 1m |
| Nominal impedance: |
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8 Ohms |
| Pyramid: |
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H 66" Base 28" X 28" W 300 lbs. |
| Pyramid Junior: |
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H 48" Base 22" X 22" W 220lbs. |
| Monitor III: |
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H 35" Base 16" X 30" W 160lbs. |
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| Monitor III |
Pyramid Junior |
Pyramid |
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That's all you need to know. Your ears will tell you the rest. Happy listening! |
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