Inleiding

Until the appearance of EBS loudspeaker cabinet were base on two basic principles: the first one is the “open” and the second the “sealed” cabinet. Examples of the first one are the reflex loaded, passive radiator and some transmission line loudspeakers. Last year a revolutionary new system was developed by TAF: it is called EBS – Extra Bass Support.

The figures below show the difference between a Synergy used with or without EBS.
Figure 1: shows the impedance magnitude of a reflex loaded / passive radiator Synergy
Figure 2: shows the impedance magnitude of a Synergy in which the passive radiator hole has been effectively closed
Figure 3: shows the EBS Synergy


Figure 1: Impedance Synergy reflex loaded / passive radiator


Figure 2: Impedance Synergy with closed cabinet – the 21 cm radiotor effectively sealed


Figure 3: Impedance Synergy with EBS

Figures 1 – 3 show the impedance of the Synergy in relation to the aformentioned cabinets. Impedance is nothing else than the Ohm resistance at a certain frequency.

In figure 1, 2 and 3 the 14 Ohm impedance peak A is caused by the bass unit’s own resonance frequency. Its own resonance frequency will move to the right – a higher frequency – when the cone (and everything connected to it) becomes lighter. On the other hand, a large bass unit produces a very low resonance frequency itself not because of its size but because of its weight. In figure 1 point B shows the so-called tuning point between respectively the reflex duct / passive radiator and the bass unit. This is the frequency where the two reinforce each other the most and by doing so cause the largest difference in sound pressure compared to a sealed system. However, as the frequencies go down, a fault in the phase angle appears between respectively the reflex loaded / passive radiator and the bass unit. This causes them to work against (instead of reinforcing) each other. The result: in the end the lowest frequency of a sealed box outperforms the lowest frequency of an open box. See figure 4: 1 vs 2.

What actually is Extra Bass Support (EBS)?

EBS is a carefully selected bass unit which is “reconed” by TAF combined with its own electronic EBS network. “Reconed” means that a special, mass increasing substance is applied to the cone. The result of this TAF bass unit modification: an extremely stiff cone combined with an unheard of low resonance frequency of its own! By connecting the EBS unit and its EBS crossover electronics in a parallel way to a bass unit in a sealed box, the two will become a voltage diviser.

As opposed to the bass unit which turns into a high-Ohm unit because of its own resonance frequency, the EBS unit retains its low-Ohm value because of its own inertia. The EBS unit will therefore spare the bass unit and prevent it from reaching its own resonance frequency. All of this causes a substantial decrease in second and third harmonic distortion.

In the case of the Synergy EBS it is 10dB compared to an open and sealed Synergy (see figure 7 vs figure 5 and 6). Because the EBS unit and crossover are connected ‘hard’ to the main amplifier there won’t be any phase shifting like there is in a reflex loaded or passive radiator system (figure 4). Like a closed system this will happen in a more even way, without the phase turning typical for the reflex loaded or passive radiator cabinet. Figure 4 speakes for itself!! By the way, the Synergy has only a capacity of 20 litres!

Measurements weren’t done in an anechoic chamber but on the TAF construction site, so all spatial “bumps and dips” are included in an honest way. The microphone was placed on a height between the mid-high and mid-low units at a distance of 1 metre; amplifier power was 1 Watt. The Synergy was free-standing for at least 1 metre in every direction.

The EBS unit’s own heavy mass in combination with the EBS crossover electronics see to it that only the lowest frequencies are reproduced by the EBS unit.


Figure 4: Frequency response characteristics Synergy EBS (red 3); reflex loaded / passive radiator (blue 1) and closed (green 2) Synergy


Figure 5: Distortion measurements reflex loaded / passive radiator Synergy


Figure 6: Distortion measurements closed cabinet Synergy


Figure 7: Distortion measurements Synergy EBS

EBS delivers a better, tighter, cleaner and more detailled bass response without the usual distortions. EBS doesn’t only combine the advantages of reflex loaded/passive radiator and sealed system loudspeakers but it even surpasses it!!!

So: EBS makes the difference!!!!!