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TopLine Bob M

The Top Line “Bob” M Hornloudspeaker demonstrates the symbiosis of high-end sound and slim design.

Based on the concept of the Top Line “Bob” L Hornloudspeaker, with a smaller footprint. Here works a combination of horn speakers, four passive 8″ carbon coated Paper low-mid tone chassis and 8 DSP-controlled active 10″ subwoofers with an amplifier power of 1500 watts.

This universal talent also follows the open-baffle principle. This design completely dispenses with the inherent sounds of enclosures and does not require any damping. Only in this way can you actually hear your electronic chain “breathe”. With the Top Line “Bob” M you can enjoy and experience music in its most vivid form and feel the soul of music in every single octave.


SPL: 90dB 1W/1m

Impedance: 10 Ohm

Crossover Frequencies: 950 Hz / 320 Hz/ 50 Hz ( Active)

Frequency range: 20 Hz – 25 000 Hz (-3dB)


Material: Wood

Colors: The colors of the housing and horn can be chosen individually

Weight: 50 kg (per piece)

Dimensions: height 1260mm, width front 233mm, width back 400mm, depth 305mm, depth including horn 410mm, diameter horn 320mm


Audiotest Magazine 07/2018

“Yet (The Bob M) does not sound Technocratic at all, but incomparably Alive. With the Top Line, Holger Stein has succeeded in creating a Real Acoustic Milestone.”

Johannes Strom – Like Hifi Magazin

“A new discovery for us as well, because for a moment you actually think you left the window open and dare to look outside and gaze at the sky, only to realize that the realism of the reproduction is so excellent that we were deceived into an acoustic hologram.”

The basic idea was to build a smooth sounding Hornloudspeaker with excellent impulse response. A horn gives a perfect adaption of the diaphragm movement to the air that then transports the sound. We have been choosing this concept for the mid and high frequencies as it significantly helps getting accurate low level information. The idea was not to increase the efficiency, as doing this often tends to result in a clear but somewhat thin and harsh sound. Also we did not use compression drivers for exactly the same reason, but spend a lot of effort into a perfect matching between horns and drivers.

For the lower frequencies we decide to use an open baffle, as this concept perfectly loads the speakers at both sides in a balanced way. We also choose to go for speakers with a big surface: Smaller cone area surface needs to be compensated by excursion, which is much less linear.
Having a large cone area means a significantly reduced cone displacement, so that the cones always move in their linear region, creating extremely low distortions. In the lower midrange four 8” Kevlar cones treated with a special carbon composite are doing their job. The bass is reproduced by 8 pieces of carbon composite treated10” speakers, which provide an effective surface of more than 500 square inches.

Four of the bass speakers are mounted on each side of the speakers, which gives an excellent
impulse compensation and very low resonances in the housing.

Each speaker is powered by 1500 Watts in the bass section, and controlled by a DSP to perfectly adapt the bass response to the room. The rest of the speakers works passive, so that you may use your favorite electronics from 55Hz upwards.

Only the best components are used in the crossover, and we did not only care for an excellent frequency response, but also a linear phase and a perfect transient response. Perfect technique for us is an absolutely essential aspect.

But we believe creating devices which finally sound good need more.
For us this is an art, like building a master violin, where good skills are essential but not sufficient.

General characteristics of the Stein Music Top Line Speaker series

• Open baffle for the non horn loaded speakers achieves a perfect impulse response as the speakers are not caged in a box.

• Big diaphragm surface (> 4m² for the XL subwoofers) so that the displacement of the diaphragms is always small and in the linear region.

• Horns for the higher frequencies excellently adopt the small displacement of the diaphragms to the air.

• The radiating characteristics of the bass are chosen that way that they will not stimulate the room resonances.

• Line array for the deep mid frequencies which has the same dispersion characteristics as the horns.

• All speaker diaphragms are treated with carbon composite for a coherent sonic character form the deepest bass till the highest audible frequencies.

• Carefully selected drivers so that a very simple crossover with finest quality components may be used.

• Active integrated subwoofers, which makes the speakers easy to drive with amps > 30 watts.

• No typical horn sound, just lots of music.