Tesi 661

The Indiana Line Tesi 661 loudspeakers are a 3-way design with a bass reflex cabinet, which allows for high dynamics of the reproduced audio signal. The interior of the massive cabinet hides solid reinforcements. The applied solutions allow to reduce the influence of undesirable resonances on the sound. This three-way model of the Tesi series is intended primarily for larger interiors of up to approx. 25 m2. It will play best, approx. 1 m from the wall.


SRP per item

sale only in pairs

Indiana Line Tesi 661

Established in 1977, Indiana Line is now one of the most important Italian brands offering loudspeakers and installation loudspeakers. The designers and engineers developing new models with the Indiana Line logo strive to achieve high-quality workmanship, with the rational use of particular components. The goal of this approach is to achieve sonic qualities that go far beyond the parameters that can be achieved in this price range.

Timeless color versions

The classic, yet stylishly rounded cabinet of the Indiana Line Tesi 661 perfectly reflects the principles of Italian design thought. The speaker has been finished with durable and at the same time extremely aesthetic vinyl in the color of light walnut, black oak or white. Regardless of which color version you choose, the Tesi 661 model will look great in any interior. This speaker not only looks good but is also distinguished by full and mature sound.

The impressive scale of sound

The Tesi 661 by Indiana Line is a majestic 3-way floor-standing loudspeaker. Its construction uses as many as four electro-acoustic drivers: a 26 mm dome tweeter, a 160 mm mid-woofer, and a pair of woofers with a diameter of 160 mm and a large linear excursion. The massive cabinet with two internal reinforcements rests on four solid cast aluminum feet with anti-vibration rubber pads. Bass reflex port is in the base. Tesi 661 will be perfect for larger interiors (of 16 to 25 m2), where it will ensure an impressive scale of sound, preferably standing about 1 meter from the wall. The speaker has an amplifier loading impedance between 4 – 8 ohms, and the power of the amplifier used to power it should be in the range of 30 to 150 W.

Perfectly matched design

The mid-woofer driver used in the Tesi 661 model has been appropriately profiled and made of a mixture of polypropylene and mica, which gives the membrane the rigidity necessary for extremely precise reproduction of even the smallest sonic details. In the center of the woofer membrane, there is a phase plug, which ensures a wide dispersion of mid-frequencies, filling the listening room with them. The bass electro-acoustic drivers below have cellulose-pulp membranes that are known for warm and powerful reproduction of the lower frequencies. Above the mentioned drivers there is a silk dome tweeter with a neodymium magnet and a radial rear chamber. It is mounted in an undercut and specially profiled front, as close as possible to the mid-woofer. The tweeter produces open and clear treble, while perfectly blending with the mid-woofer used in the Tesi 661 model. What’s more, the tweeter filter uses only air coils and foil capacitors. Deep and dynamic bass is not only the result of the drivers used but also the low and smooth tuning of the bass reflex system.

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The most important features of the Tesi 661 model:

  • 3-way acoustical design
  • Crossover frequencies: 400 Hz and 3 kHz
  • 2 x 160 mm woofer
  • 160 mm mid-woofer
  • 26 mm silk dome tweeter
  • Bass reflex cabinet with a port in the base
  • Frequency response: 35 Hz to 22 kHz
  • Bi-amping / bi-wiring capability
  • Finish: white, black oak or light walnut
  • Suggested amplifier power: 30 – 160 W
  • Sensitivity: 92 dB (2,8 V / 1 m)
  • Dimensions (H x W x D): 925 x 180 x 300 mm
  • Weight: 14,1 kg

Technical data

Speaker alignment / type

3-way / floorstanding

Box aligment / port placement

bass-reflex / bottom

Driver diameter

midwoofer: 1 x 160 mm, mica-polypropylene cone, tweeter: 26 mm, silk dome, woofer: 2 x 160 mm, natural cellulose pulp cone

Frequency response

35 – 22000 Hz

Sensitivity (2,8 V/1 m)

92 dB


400 / 3000 Hz

Bi-wiring / bi-amping


Amplifier loading impedance

4 – 8 ohm

Suggested amplifier power

30 – 160 W

Suggested room size

16 – 25 m²

Suggested placement

1 m from the wall

Dimensions (H x W x D)

925 x 180 x 300


black oak, light walnut, white


14,1 kg

100% polyester damping

All Indiana Line cabinets are filled with polyester – a synthetic non-woven fabric of high purity, known for its excellent damping of the internal resonances of the speaker cabinets. What's more, polyester is also extremely resistant to stretching, drying and moisture.

100% polyester damping

Air coils and film capacitors

In order to emphasize the exceptionally clear and natural sound of our loudspeakers, we decided to get rid of the troublesome components from the crossover where it was necessary – in the tweeter filter. In all loudspeaker models in which this filter is used, we use only air coils and foil capacitors. These elements do not introduce harmful distortions to the filtered signal, as is the case with ferrite core coils and electrolytic capacitors.

Air coils and film capacitors


The short-circuit ring is made of pure, perfectly electrically conductive aluminum (1010). It has been placed inside the magnetic system of the mid-woofer. By linearizing the impedance of the loudspeaker, it positively influences the sound of the low and medium frequencies of the acoustic band, significantly reducing non-linear distortions. The ring also absorbs the heat emitted from the speaker coil, increasing its thermal load capacity.


MDF housing with transverse reinforcements

Indiana Line loudspeakers cabinets are made of MDF panels. They are made using the latest production techniques, which ensures high precision of workmanship, great repeatability and excellent performance parameters for many years. MDF is a moisture-resistant material, it is massive and it suppresses all resonances very well. To completely remove unwanted vibrations, we used transverse reinforcements of the cabinet. They take the form of horizontal rings that are located at key points along the entire height of the loudspeaker cabinet.

MDF housing with transverse reinforcements

Mica-poly cone

Universal and extremely popular polypropylene is a valued material, often used for speaker membranes. However, in order to ensure the most faithful transmission of micro-details, we decided to further increase the stiffness of the cone. We achieved this by doping polypropylene with a mineral called mica. This shiny, hard material significantly improves the parameters of the membrane, guaranteeing the transducer a long and reliable operation, and at the same time giving it an attractive appearance.

Mica-poly cone


A radial damping chamber that prevents harmful reflections under the tweeter dome while allowing it to achieve a low resonance frequency. The small, but at the same time strong, neodymium magnet of the tweeter is surrounded by a space in which – due to its shape – standing waves cannot be generated, which is the case with classic radial chambers located in the axis of the dome.


Indiana Line Catalogue EN


Indiana Line Tesi – owner's manual


Indiana Line Tesi 661 – product card_EN


Pricelist 2023


Test - Tesi 561 - 661 - Stereoplay - DE


Test – Tesi 661 – Audio Review – IT


Test – Tesi 661 – Stereo - Video – CZ


Test – Tesi 661 – Suono – IT


Test – Tesi 661 – Technic 3D – DE