Thomastik Peter Infield 3/4 Si - Medium

A Low String Designed to Support Orchestral Playing

The Peter Infeld PI65 is a low B or B♭ string designed for 3/4 double basses used in orchestral tuning. It is intended for double bassists looking for a low string that retains weight, presence and a controlled response without losing definition. Its design prioritises a stable playing feel and a rich tonal response, particularly useful when the low string needs to anchor the instrument as a whole.

Thanks to its spiral core combined with a chrome-plated tungsten-steel winding, this string combines tonal density with articulation. It is a suitable choice for replacing a worn low string or completing a set designed for a broad, reliable and expressive sound.

For Demanding Double Bassists, in the Orchestra or on Stage

This string is particularly well suited to advanced intermediate, accomplished and professional musicians seeking an immediate response under the bow. Its behaviour supports dynamic nuances, clear attacks and sustained low lines, whether in classical, symphonic, contemporary or jazz repertoire played primarily with the bow.

The focused character of its midrange helps define the sound in a dense ensemble, while its generous low end provides welcome foundation for both pizzicatos and sustained notes. The PI65 meets the expectations of players who want to retain substance in their sound while benefiting from good clarity in the lower registers.

The Sound

The Peter Infeld PI65 produces a powerful, richly coloured sound built around a pronounced midrange. On an acoustic double bass, the final result naturally depends on the top, back, ribs and the instrument’s overall setup. A responsive top will emphasise attack and projection, while a back and ribs that promote resonance can enhance depth and note length.

The chrome-plated tungsten-steel winding contributes to the density of the low register and the stability of the string. The spiral core, in turn, supports a reliable response under the bow, with a clear onset and good continuity between the attack and the sustain. This combination helps produce a present low end without sacrificing the focused, expressive character of the midrange.

With a tension of 30.7 kg, the string provides a resistance suited to committed playing. It promotes precise bow control and a sound that retains body, particularly in passages requiring power, support and evenness. The specified tension is measured for a vibrating length of 104 cm.

Technical specifications

Format	3/4	Category	double bass
Tension	Medium	Nbr of strings	1

Instrument	acoustic double bass	Winding	tungsten-chrome steel
Compatible size	3/4 double bass	Design	proven spiral core
Compatible vibrating length	1030 to 1100 mm	Tension in pounds	67.7 lbs
Reference vibrating length for tension	1040 mm	Sound	powerful, elegant and rich in colour
Tuning	orchestral	Midrange	focused and assertive
Position	low B or B♭ string	Low end	present and solid
String reference	PI65	Bow response	excellent
Core	spiral	Sustain	beautifully stable on sustained notes
Core design	renewed combination of materials	Reliability	high