Design Philosophy


If you are looking for maximum control over the in-room response of your audio system it does not get any better than integrating digital signal processing into the audio signal chain and drive your loudspeakers active. Today there are quite a few DSP solutions available, in hardware or software format, to help you achieve this.

However, almost every loudspeaker is equiped with an internal crossover network. Removing, or bypassing, the crossover board of such a loudspeaker comes with a lot of issues because they are simply not designed for this application. And if you are able to do so, you would still need accurate measurements in order to design a good DSP crossover.

If you have the skills, knowledge, equipment and time that are required for a succesful project you could choose the DIY route. If that is not an option you might even consider a custom design. Both can become an expensive adventure, especially if you want to achieve maximum performance. For that you will need complex and accurate measurements, and a diffraction optimized, resonance free cabinet design.

So we developed a modular loudspeaker range, left out the internal crossover, measured the response at IFAA and designed an optimized set of crossover parameters with FINE DSP™ for each variant. The measurement data set is included in the delivery.

Copy the crossover parameters to your DSP, arrange the routing and connect your amplifiers. It is a bit more complex than usual but once set-up you will be rewarded with sublime sound quality.

Such outputs do have a purpose.

minidsp HT Flex DSP processor for active crossover

Durable & Versatile

Keeping the electronics and software (e.g. power supply, amplifiers, DSP, DRC, DAC/ADC, streamer) external has several advantages compared to an all-in-one 'box' solution.

The main advantage is that you can use the hard- and software you prefer and that it is easier to keep those up-to-date, it is more future proof and therefore durable.

Another advantage is that the more ventilated and less resonant environment of the dedicated external enclosures reduces the mechanical wear of the electronics. The chance of failure will be smaller, and if it happens, it will be easier and faster to get your system playing again.

Charles Hansen | 2016 | audioXpress

Why Things Fail
You are much more likely to experience obsolescence from format changes than from the failure of electronic parts. The hardware for erstwhile formats such as Betamax VCRs, reel-to-reel tape recorders, and digital compact cassettes may still perform well, but readily available support for these machines is sometimes difficult to find. Failures in equipment with moving parts (CD players, VCRs, hard drives) are much more common than in those that are purely electronic (amplifiers, computer sound cards, modern tuners).

Mechanical wear is inevitable and is accelerated by dust, vibration, humidity, and other factors against which few consumers bother to take preventative measures. The primary enemies of electronic circuitry are heat, the less-than-perfect structure of all materials used in electronics, and the electrochemical reactions that occur to degrade materials as their temperatures increase. Higher temperatures accelerate the failure mechanisms in all electronic components in an exponential fashion. All components have a basic reliability,
which has its baseline at 25°C.

Above this temperature, the components follow the “10°C” rule, which states that the life of the component decreases by half for every 10°C rise in temperature. If a transistor has a reliability of 1 million hours at 25°C, its expected life will be only 250,000 hours at 45°C. This will decrease to 125,000 hours at 55°C. Few components exist that can withstand more than 125°C.

Smooth diffraction

The spherical shape of the top unit and generously rounded edges on all other parts smooths the way for a uniform diffraction pattern, which in turn improves the perceived sound quality. Besides that, it allows for less - and more effective - equalization and digital room correction.

An excerpt from an old - but stil valid - research by H.F. Olson:

Fig. 6. It will be seen that the response is uniform and free of peaks and dips. This is due to the fact that there are no sharp edges or discontinuities to set up diffracted waves of a definite phase pattern relation with respect to the primary sound emitted by the loudspeaker. The diffracted waves are uniformly distributed as to phase and amplitude. Therefore, the transition from radiation by the loudspeaker mechanism into 4π solid angles to radiation into 2π solid angles takes place uniformly with respect to the frequency. It will be noted that the sound pressure increases uniformly in this transition frequency. The ultimate pressure is 6 db higher than the sound pressure where the dimension of the sphere is a small fraction of the wavelength.

The smooth diffraction properties of a spherical loudspeaker shape

Aluminium enclosures

The enclosures are manufactured from aluminium, they are strong and rigid to minimize resonances.

Purifi PTT4.0X04-NAC-04 impedance

State of the art drivers

To offer you maximum potential sound quality we do select state of the art drivers for all our models. Our current range compromises drivers from BlieSMa & PURIFI.

 Image 1

PURIFI Neutral Surround

Image 2

PURIFI Neutral Surround

purifi PTT1.3T04 aluminum-dome tweeter

Tri-pod speaker stand

A timeless design tri-pod speaker stand manufactured from steel. Rubber hemispheres are placed on both ends of the pods to prevent surface scratches on the top unit and your floor. The tri-pod is demountable for a convenient and space saving transport if needed.

Purified 4 on tri-pod standPurified 4 on tri-pod side view

Precise measurements & optimized crossover

A comprehensive measurement data set and a - variant specific - reference crossover design is included is in the delivery. You can transfer the crossover parameters to your DSP for a quick start. You may use the measurement data to fine tune different crossover configurations with the help of simulation software (e.g. VituixCAD).

Measurements are performed in the class 1 semi-anechoic chamber from IFAA. The optimized crossover designs are made by Peter Larsen from Loudsoft.

Sample raw measurement, Purifi PTT4.0X04-NAC-04 in enclosure, without crossover and EQ.

Purifi PTT4.0X04-NAC-04 raw measurements

Purifi PTT4.0X04-NAC-04 + BlieSMa T25A-6 optimized with Loudsoft

Purifi PTT4.0X04-NAC-04 + BlieSMa T25A-6 optimized with Loudsoft

Although it is clear that our inspiration is driven by the power of DSP, you can of course opt to use another outboard crossover solution.

2.X system

For a full range performance you will need at least one or two (sub)woofer(s) depending on your driver selection for the standmounts You can use any quality (sub)woofer with a smooth response up to at least 200Hz to achieve a seamless integration.