PQS-402

The Design Brief
The design brief for the PQS-402 was to produce a listening experience comparable to that of our Loreley model from a loudspeaker with a smaller cabinet, thereby making our reference level products available to a wider audience.  As well as the usual impressive German Physiks attributes, the PQS-402 also boasts a very wide dynamic range that comes close to its larger stable mate. The PQS-402 uses two 10-inch woofers and four 8-inch passive drivers to produce prodigious amounts of deep and well-controlled bass, that at the same time has the speed and finesse to perfectly match with the dual DDD drivers. The combined effect is a loudspeaker that can do equal justice to full-scale orchestral works, or a solo voice.

The Problem
Because we wanted to cross over the DDD driver to the woofer between 220Hz and 140Hz, we had to find a way to build a very fast bass system that could match the speed of the DDD driver in the crossover region and also work down to 25Hz. To reproduce low bass at high levels a lot of air has be moved. This requires either a driver with a large surface area, which will be heavy and therefore not easy to move at the speed necessary to match the DDD driver, or a driver with a long excursion, which again will be heavy due to the rigidity required to withstand the necessary acceleration. Most loudspeaker designers solve this problem by producing a 3-way system. However, in a loudspeaker the size of the PQS-402, a 3-way solution would have been worse than a 2-way solution, due to the difficulty of making 3 drivers appear to be a single source. This is especially difficult with the mid and treble drivers, where the ear’s ability to locate position is very acute. It can be done, by why bother when you have a better solution?

The Solution
Our solution was to build a bass cabinet using a fast and powerful 10-inch driver and two 8inch passive radiators. The 10-inch driver integrates flawlessly with the speed of the DDD drivers and the passive radiators extend the bass response smoothly down to 25Hz as required. The final system comprises 2 bass cabinets that are mounted one on top of the other and stand between a top and a bottom plate. None of these components is attached to the other using screws or any other form of hard connection. Instead they are held together by a system of interlocking collars. This, combined with the fact that the two cabinets have different weights, as do the top and bottom plates, means that resonances are reduced to negligible levels compared to a solid structure. This arrangement is also very difficult to topple, which is a useful safety feature for customers who live in earthquake regions.

German Physiks’ Revolutionary DDD Driver
Like all German Physiks loudspeakers, the key to the exceptional performance delivered by the PQS-402 is our carbon fibre DDD driver.  Here, this wide-bandwidth omnidirectional driver covers the range from 215Hz up to 24kHz. This extremely wide range is achieved by the use of pistonic, bending wave and modal radiation: Most loudspeakers use drivers that are purely pistonic. The same DDD driver is used on all German Physiks loudspeakers, from our entry level Unlimited MK II, to our top of the range, $300,000 Gaudi MK II. The DDD driver gives the same very important advantages to all German Physiks designs and is what sets them apart from the competition. These are:

1. Exceptionally coherent and natural sound: The extremely wide operating range of the DDD driver provides an exceptionally coherent and natural sound. This is very difficult to achieve when this frequency range is split over two or more different types of driver, which are in physically different positions on the cabinet.

This wide operating range also eliminates the crossover point in the mid-range that loudspeakers using conventional pistonic drivers must have. Our hearing is most sensitive in the mid-range and avoiding the level and phase errors that crossovers can create from this region further improves transparency.

2. Realistic stereo images more like you experience in the concert hall: When you listen to music in a concert hall, you are in an enveloping sound field where much of the sound is reflected off a surface before it reaches your ears. These reflections play an important part in the creation of the stereo image that you perceive. Because the DDD driver is omnidirectional, it radiates all frequencies evenly around it and so creates a similar enveloping sound field in the listener’s room. This way the PQS-402 is able to recreate a more natural rendition of the original stereo image. This has excellent depth and focus, but without the overly sharp image definition that some hi-fi loudspeakers produce and which you will rarely if ever hear at a live performance.

3. Stereo imaging enjoyable in almost all positions in the room: Conventional loudspeakers tend to produce stereo images that can only be best enjoyed from one position in the room, the “sweet-spot,” and then usually by only one person. Move away from the “sweet-spot” and both the stereo image and tonal balance become progressively degraded. This is because conventional pistonic drivers tend to concentrate their radiation into a beam that narrows with increasing frequency.

By contrast, the DDD driver’s omnidirectional radiation pattern enables PQS-402 to produce excellent stereo images that can be enjoyed from a wide range of listening positions in the room, while also maintaining a more even tonal balance — much like you would experience at a live performance. This gives more flexibility in where you sit and allows several people to enjoy a good sound simultaneously, so you can share your music with others.

Because you are not restricted to a small “sweet-spot” in order to hear the best sound, the PQS-402 provides a more relaxed listening experience. This is especially noticeable when you listen for long periods.

4. Exceptional dynamics: The DDD driver’s very low moving mass provides an excellent impulse response, allowing it to recreate both the attack of the music and resolve low level detail very accurately. The resultant transparency is maintained even on complex high-level passages.  For example, cymbals have an authentic initial smash and the ebb and flow of the subtle overtones that follow are clear and unmasked. This ability is essential in order to faithfully reproduce the delicate nuances of a performance and make it sound like music, rather than just good hi-fi. Once you have become accustomed to the more natural presentation provided by our DDD driver, it can be difficult to go back to listening to a conventional design. This is something we often hear from our customers and it has also been commented on in reviews.

5. Accurate portrayal of musical instruments’ tonal characteristics: The DDD driver is phase linear across its operating range, ensuring that the tonal character of each musical instrument is reproduced with great accuracy. This together with the excellent dynamic response enables the Borderland MK IV to reproduce percussion with startling reality. Voices have a clarity and purity that can be breath taking, with all the elements that comprise the vocal sound correctly located in space and with no undue emphasis. The hardness you often hear with conventional tweeters is eliminated and you get a greater sense of hearing a live musician rather than a recorded one.

More information on the DDD driver, its development and advantages may be found on the Technology page of the German Physiks web site at http://bit.ly/1jLZekr

Low Resonance Cabinet
Because of the very high sound level capability of the PQS-402 (118dB), we went to great pains to design a cabinet where resonances were minimized, as these would otherwise degrade the loudspeaker’s ability to resolve the fine detail that is essential in order to produce a sense of realism and hence convey the emotion that is the essence of a musical performance.

The PQS-402’s DDD drivers use very small enclosures, minimizing the area of any potential vibrating surface. By being cylindrical, they eliminate the resonances that can arise with a conventional rectangular or square section cabinet. Because they are made from aluminum, a comparatively soft metal, residual vibration of the enclosure is minimized. The DDD driver enclosure end-caps are made from non-resonant MDF and the enclosure is packed with damping material to dissipate any standing waves. The result is that the PQS-402 has the clarity that we normally associate with electrostatic loudspeakers and for the same reason: they essentially have no enclosure to color the sound

The bass system, which covers the range from 215Hz downwards, is divided into two independent cabinets, so the panels are smaller and therefore stiffer and more vibration-resistant than if a single large enclosure had been used. All the cabinet vertical surfaces are non-parallel to prevent the formation of standing waves between them. Internal bracing increases rigidity to suppress resonances. Residual vibration is minimized by applying a special damping material called Hawaphon®, to the inside surface of each panel.

Hawaphon® consists of a polymer sheet containing a matrix of small cells filled with fine steel shot. It adds mass to the panels to reduce the resonant frequency and the ability of the balls in each cell to move against each other provides a very effective way of converting vibration energy into heat. Originally developed as an anti-surveillance measure for use in military and government buildings, Hawaphon® achieves broadband attenuation of structure-borne sound of more than 50dB, which is an exceptionally high figure.

To damp resonances of the air within the cabinet, the whole of the interior is lined with a 1cm thick layer of high-density felt. This is achieved by fitting pieces of felt that are precisely cut to fit each panel, rather than just inserting a roll of felt into the cabinet. This is a time consuming process, but we believe produces a superior result and is typical of the attention to detail that we lavish on all of our products.

Patented Crossover Design
The crossover provides a wide range of adjustment to allow the PQS-402 to be better set up to suit the user’s listening room. The high frequency level may be adjusted over the range -2dB to +4dB in 4 steps and the low frequency level may be adjusted over the range +10dB to 0dB in 3 steps. The low frequency control has no effect above 100Hz and we have applied for two patents to cover the novel approach that we developed to achieve this. Both controls are facilitated by high quality jumpers located on the loudspeaker’s rear panel and may be quickly and easily adjusted.

Biamp Upgrade
The standard configuration for the PQS-402 is a single power amplifier, but a significant improvement in performance may be achieved if the loudspeaker is bi-amped. This is cheaper and a lot less trouble than upgrading to a new loudspeaker system.

Hand Finished Cabinets for Ultimate Quality
Because the look of our products is as important as the sound, all our cabinets are built and finished by skilled cabinetmakers for the best possible furniture grade finish.

The PQS-402 is available in black or white high-polish polyester; a wide range of high quality veneers in both satin and high gloss lacquer and satin and high gloss automotive paint finishes.

A high gloss carbon fiber finish is also available to special order. Here the cabinet’s heavy MDF panels are reinforced with multiple layers of bi-directional, resin impregnated carbon fibre, applied using techniques originally developed for the aircraft industry. This is then coated with a multi-layer lacquer and hand finished to a luxuriously high lustre. As well as looking extremely attractive, the carbon fibre adds an additional degree of stiffness to the cabinet.

More details of the finishes available may be found on the main German Physiks web site at http://bit.ly/1lj7U5x.

For product images and the latest version of the user manual, please follow this link to the German Physiks Download Page.

PQS-402 Specifications