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THE PQS 402

THE PQS 402

The Challenge

The design brief for PQS 402 was to reproduce the sound of our Loreley model in a smaller loudspeaker using similar technology and so make our reference performance level products available to a wider audience. The PQS 402 succeeds in this.  It can play prodigiously loud – up to 118dB and it can play very deep – down to 25Hz, whilst all the time retaining the delicacy and transparency that German Physiks loudspeakers are famous for.


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 8 inch passive radiators. The 10 inch driver integrates flawlessly with the speed of the DDD 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 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.

The DDD Driver

The DDD driver is used on all German Physiks loudspeakers and the same quality of driver is used on all models from our entry level product to the top of the range Gaudi. This revolutionary driver gives the same very important advantages to all German Physiks designs and is what sets them apart from our competitors.


The DDD driver’s very low moving mass enables it to operate linearly over an extremely wide frequency range. On the PQS 402 it covers the entire range from 215Hz upwards  In a conventional design, this range would be covered by two or even three different types of driver and most importantly there would be a cross over point in the mid range, the area where our hearing is most sensitive. The DDD driver’s wide operating range allows this vital region to be kept free from the level and phase anomalies that multiple drivers and a necessarily more complex crossover would create. This enables the PQS 402, like all German Physiks loudspeakers, to produce very accurate and realistic stereo images.


Another key advantage of the DDD driver is that it is omni directional, so these excellent stereo images can be enjoyed from a wide range of listening positions, unlike conventional designs which have much smaller “sweet spots” due to the tendency of their drivers to beam the sound.


The DDD driver’s very low moving mass provides the further benefit of exceptional impulse and phase response characteristics and allows it to reproduce both the attack of the music and resolve low level detail very accurately. This is essential in order to faithfully reproduce the delicate nuances and timbral characteristics of a performance and make it sound like music, rather than just good hi-fi. The driver’s excellent impulse response also ensures that the stereo image remains focussed and stable, even when the loudspeaker is reproducing complex passages at high levels.