About multi band EQ

FMOD Engine
1

Sorry for spamming questions in a row.

I sometimes get even more confused and have more questions after learning something, haha…

Let’s say I’m expecting something like this :

expected_graph

and have code like this :

FMOD_DSP_SetParameterInt(m_DSP_EQ, FMOD_DSP_MULTIBAND_EQ_A_FILTER, FMOD_DSP_MULTIBAND_EQ_FILTER_PEAKING);
FMOD_DSP_SetParameterFloat(m_DSP_EQ, FMOD_DSP_MULTIBAND_EQ_A_FREQUENCY, SOME_LOW_FREQ);
FMOD_DSP_SetParameterFloat(m_DSP_EQ, FMOD_DSP_MULTIBAND_EQ_A_Q, 10);
FMOD_DSP_SetParameterFloat(m_DSP_EQ, FMOD_DSP_MULTIBAND_EQ_A_GAIN, 30);

FMOD_DSP_SetParameterInt(m_DSP_EQ, FMOD_DSP_MULTIBAND_EQ_B_FILTER, FMOD_DSP_MULTIBAND_EQ_FILTER_PEAKING);
FMOD_DSP_SetParameterFloat(m_DSP_EQ, FMOD_DSP_MULTIBAND_EQ_B_FREQUENCY, SOME_HIGH_FREQ);
FMOD_DSP_SetParameterFloat(m_DSP_EQ, FMOD_DSP_MULTIBAND_EQ_B_Q, 10);
FMOD_DSP_SetParameterFloat(m_DSP_EQ, FMOD_DSP_MULTIBAND_EQ_B_GAIN, 30);

Then I found this answer from your team, which says :
“We don’t have this type of effect, the closest we have is the FMOD_DSP_TYPE_THREE_EQ which allows for 3 bands in parallel whereas the FMOD_DSP_TYPE_MULTIBAND_EQ does not run in parallel.”

I’m not sure what PARALLEL means here.
Is it that I need to use FMOD_DSP_TYPE_THREE_EQ instead of FMOD_DSP_TYPE_MULTIBAND_EQ in my above example code as well?

One more question.

FMOD_DSP_MULTIBAND_EQ_B_Q’s possible maximum value is 10 (and that’s why I used 10 in my above example).

It’s kind of obscure what the value 10 means. I don’t think it’s ±10Hz.

Also, is there any way for me to apply a much wider bandwidth like this?

expected_graph2

2

To achieve the effect of the first image you posted the closest you can get is with the 3-EQ effect, not the multiband EQ effect. As you mentioned, 3-EQ has 3 bands that operate in parallel, multiband EQ can have up to 5 bands in series. When an effect like this operates in parallel, it’s as if the incoming signal is split into multiple copies, each band affects one copy of the signal, then the result is merged together. When run in series it’s as if the signal is processed by the first band, then the output of the first band is fed into the input of the second band (and so on).

You can use FMOD Studio to visualize what the settings of the multiband EQ do to the frequency response then simply copy the values into your code. Q has different meanings depending on the filter chosen, the best way to understand is to see the frequency response in Studio.

The first image is tricky because you essentially need a 5-EQ, a band for the left of the first peak, the first peak, in-between the peaks, the second peak and the right of the second peak, each one alternating low / high. If you are willing to compromise by extending the first peak left to the start of the frequency range, and extend the second peak to the right until the end of the frequency range the 3-EQ would satisfy.

If you aren’t willing to compromise you’ll need a more complex setup involving sends, two tracks each with their own 3-EQ, then merge them together.

The second image is easy with 3-EQ, simply set the X-Low and X-High at either side of your peak, then apply the gain for the mid as desired.

1 Like
3

Your kind answer was very very helpful!
Thank you very much :slight_smile: