ToolMod Pro Audio
M/S Stereo EQ TM134

Special M/S Equalizer with 4 fully parametric Bands and Matrix Stages at Input and Output

The TM134 provides an easy way to accomplish frequency dependent manipulation of the stereo image. The integrated L/R to M/S matrix at the input and the M/S to L/R matrix to reconvert the processed signal into the common left-right stereo format make it possible to use the M/S EQ with standard stereo signal as well as part of an M/S stereo processing chain. Each of the 4 fully parametric bands can be used either in the S channel, the M channel, or in both channels with reversed direction of the boost/cut controls.
  • 4-Band M/S EQ
  • Boost/Cut Range
    8 dB
  • Input L/R to M/S &
    Output M/S to L/R
    Matrix integrated
  • can be used with
    L/R or M/S Input
    and Output Format
  • 4 fully parametric Equalizer Bands<
  • 3 Modes per Band:
    M-Chain only, S-Chain only
    or M&S compensating
  • Q Range from
    3 oct. to a third
  • Low 20 Hz - 1 kHz
  • Mid1 50 Hz - 5 kHz
  • Mid2 0.2 - 15 kHz
  • Hi 0.4 - 25 kHz
  • Headroom + 30 dBu
  • Dynamic Range
    123 dBA/120 dBRMS
M/S Stereo EQM/S Stereo EQ TM134 with +/- 8 dB Range
At a glance, the TM134 looks like a fully parametric 4-Band EQ; however, this module has an entirely different purpose. Using equalization not in the standard left-right stereo format but in the M/S format, offers a sophisticated way to modify the stereo image. While a unit like the M/S direction mixer TM130 can reduce or enhance the stereo base width over the entire audio frequency band, the M/S EQ makes it possible to apply stereo base enhancement or reduction in the frequency bands that are defined by the center frequency and q-factor controls. Here is some basic information on equalizers in the M/S format.

M/S Matrix
The most annoying obstacle of just using M/S equalisation is the need to convert and reconvert the left-right stereo signal to and from M/S. Unless the input and output format is already M/S (which is rarely the case) , an additional L/R to M/S matrix is necessary before the equalizer and another matrix is needed to convert the processed M/S format signal back to L/R stereo. The TM134 overcomes this problem since the matrix stages at the input and output are integrated in the module. The M/S EQ can therefore be used with standard left-right stereo signals without that anything else is necessary. The input and output matrix stages are independently controlled by the switches, which allows integrating the M/S-EQ into a M/S signal chain and use either the input or the output matrix for L/R to M/S or M/S to L/R conversion independent of the equalizer. The bypass switch, which defaults to enabling the EQ and the matrix stages at a time, can be alternatively configured to remain in the signal path while the bypass switch affects only the equalizer.

Frequency dependent Stereo Base Width Control
Using M/S equalization always affects the stereo base width and the frequency response. Unless a stereo signal has an extreme wide stereo image, the level of the M channel is almost always 10 to 20 dB higher than the level of the S channel. Using the TM134 in the S channel alone results in a strong influence on the stereo image with only a small influence on the frequency response. If the M/S EQ is used in the M channel only, the effect on the stereo image is lower but the eq setting is a lot more audible, although the eq itself affects only the center of the stereo system. Each of the 4 fully parametric bands of the TM134 comes with a 3-position lever switch that determines the operation mode. In the S position, the particular band affects only the S channel for effective control of the base width with minor eq effect. In the M position, only the M channel is affected with minor effect on the stereo base width and a much higher eq effect. The center position 'M/S' affects both, M and S channels at a time, but in the way that a boost in S results in a cut in M and vice versa. This mode can partly compensate the audible equalizer effect; however, using the TM133 M/S Stereo Mastering Equalizer for this purpose is the better solution. The orientation of these pots applies to the base width; turning the pot to the right enhances the base width in the particular band while turning to the left reduces the base width.

EQ Bands
All fully parametric equalizer bands are implemented using adt-audio's fully parametric active 'Vienna Bridge' circuit that combines the flexibility of an active eq with the sound performance of a passive LC equalizer. The Boost/Cut ranges of +/- 8 dB are adapted to the use as M/S EQ; however, custom versions with any range up to +/- 16 dB are possible on order at short notice as well.

Sweep Ranges & Q-Factor
The four bands cover the entire audio range from 20 Hz to 25 kHz. The LOW-Band starts at 20 Hz and ends at 1 kHz. MID 1 covers the range from 50 Hz to 5 kHz and MID 2 starts at 200 Hz and ends at 15 kHz. The HIGH band covers the range from 400 Hz to 25 kHz. Due to the large overlaps, different bands can be used in the same frequency range. The range from 400 Hz to 1 kHz is covered by all four bands; 200 Hz to 5 kHz is covered with both mid bands and - from 400 Hz - with the high band as well. The q-factor control range is the same for all four bands and covers a range from about 3 octaves for global corrections down to a third for subtle filter settings.

The headroom is + 30 dBu throughout the entire M/S EQ. At linear settings, the output noise is less than -94 dBA/-90 dBuRMS with M/S input and output, which results in a total dynamic range of at least 124 dBA / 120 dBRMS.

The TM134 is a 4U ToolMod that fits into two slots of the horizontal 1U high ToolMod Frames. The vertical version fits into a slot of a 4U high ToolMod Frame.

Inquiry / Order
Price: € 1100.00
excl. of VAT and Shipping
Currency Converter
Price List
ToolMod Frames
Test Reports
TM134h - horizontal
TM134v - horizontal
M/S EQ Basics
technical Specifications
Control Elements
Picture - h-Version
Picture - v-Version
ToolMod Manual
M/S EQ vertical VersionTM134 vertical
vertical Version


Where to buy
Tell A Friend

M/S EQ vs M/S Direction Mixer

Although the TM134 M/S-EQ can be used stand-alone with excellent results, the TM130 M/S Direction Mixer with elliptical EQ is the ideal addition to the equalizer. The elliptical equalizer in the matrix maintains a stable, centered bass range while the base enhancement takes place with the M/S EQ. In most cases the frequency independent base width setting of the direction mixer can be used to reduce the overall width afert applying the enhancement in certain frequency bands with the TM134. This method can reduce mono compatibility issues that are always side effects of base enhancement effectively.