BGS 40 - 8 Ohm

The MB 115/H professional musician's speaker is a compact, excellent value for money vented cabinet. It is equipped with the BGS 40 - 8 Ohm woofer and the HTH 8.7 - 8 Ohm mid- to high-range horn. A 2-way combination has the invaluable advantage of simplicity. However, combining a 15" woofer with a tweeter is not completely without its problems, since the cone of the woofer must also produce resonance-free and distortion-free sound in the mid-range. The tweeter, for its part, has to be distortion-free at relatively low frequencies and, at the same time, have good power handling capabilities. We decided on a cut-off frequency of 3000 Hz - a level both speaker drivers can cope with effortlessly.

The rated power output of the speaker is 200 watts. This rating is determined in accordance with the DIN standards using a permanent noise signal. This value is, however, far removed from practice, since music consists of many different impulses and surges. The effective value, that also tells us something about the heating-up of the voice coil, is much lower with music. We have successfully tested the MB 115/H with a professional-quality amplifier up to the clipping limit, so we are safe in saying it has a music rating of 500 watts. At this level, peak outputs of 120 dB are achieved at a distance of one metre.

The MB 115/B building suggestion is a bass speaker for professional musicians. If fullrange musicians' speakers need boosting the bass department, you need bass speakers with a comparatively high level of efficiency. Bass reflex speakers have the advantage of a low limiting frequency, but this also means they need a large cone area with the large cabinet that this entails, in order to produce sufficient sound pressure. A completely uncompromising bass speaker should really be enormous. However, the MB 115/B makes use of a cleverly designed flare geometry, perfectly matched to the BGS 40 - 8 Ohm driver, to produce a relatively compact horn. A limiting frequency of 50 Hz is a perfectly respectable level for a musician coupled with an output level of 96 dB above 60 Hz under open-field conditions (no walls, no floor) at just 1 watt is an excellent starting point for extreme bass pressure. It must be taken into account that, positioned on the floor away from walls, this figure increases by 3 dB and near a corner by as much as 9 dB. We measured peak output levels of as much as 125 dB (above 60 Hz) under favourable conditions. And all that with the typical horn-like, bone-dry sound characteristics an experience for aficionados of solid-level, dynamic sound!

The horn sound develops in a vortex beginning in front of the diaphragm and moving outwards towards the opening. At the rear, the woofer acts on a small, enclosed compartment. This prevents the stroke in the low bass and subsonic ranges from becoming too extreme which prevents mechanical damage to the driver. The impedance curve retains a pleasingly high level throughout. This means that the booster is not overloaded and the voice coil does not overheat. Crucial points in the tough daily life of professional musicians.

Active separation is recommended. This allows the optimal position between separating frequency and slope rate to be found. As a cost-saving alternative, we have also developed a passive crossover. This system separates at 150 Hz and goes well with the top-of-the-range MB 208/H, if the recommended high-pass section is used ( refer to MB 208/H ).

The MB 156/3 extends the range of musicians' speakers available from Visaton by adding one new 3-way combination. The bass department is controlled in this arrangement by the BGS 40 - 8 Ohm, which is a carry-over from the successful MB 115/H. The mid-range is provided by the BG 17 - 8 Ohm which, thanks to its high sensitivity level, has no problem at all matching the output level of the woofer. The combination is neatly rounded off at the top range of frequencies by the HTH 8.7 - 8 Ohm horn which has also already made a good impression in other speakers.

To ensure that the high sensitivity of the BGS 40 - 8 Ohm, which on average is 95 dB (1 W/1 m), is also achieved at the low frequency range, there are two bass reflex vents in the baffle. Having the tuning frequency set at a high 55 Hz means that the thickness of the material used for the front panel is sufficient as the length of the bass reflex tubes. No tunnels or tubes are required.

A well-tuned crossover ensures that each of the three drivers only deals with the range of frequencies for which it was originally designed. In the case of the MB 156/3, this arrangement results in a highly linear frequency response, even at high output levels, which is close to hi-fi needs.

The NoBox BB unites a number of preferences in a single concept: it achieves the directness of a full-range loudspeaker, in particular in the voice range, and also manages to produce powerful, stable bass without having to fill the room with hardware.

The B 200 - 6 Ohm is used in the NoBox BB together with a 38 cm BGS 40 - 8 Ohm woofer in an open baffle as a dipole. The electric separation between the two drivers is low enough (250 Hz), which enables the full-range speaker to make full use of its capabilities and the BGS 40 - 8 Ohmis effectively the supporting woofer. The BGS 40 - 8 Ohm is a musician's driver with high sensitivity and can, as a result, easily be adapted to the B 200 - 6 Ohm without giving anything away in terms of mean sound pressure.

Despite the baffle being open, which theoretically causes an acoustic short circuit in the bass range, the system produces a dynamic low bass output down to 32 Hz (-10 dB). One reason for this is that the baffle is cut off from the floor and so no acoustic short circuit can take place in this direction. In addition, the side panels of the cabinet, which are mainly for stability, increase the acoustic distance travelled.