Waves – API 550A + API 550B

Hey Labfans! Today I will be analysing the 550 A/B from Waves.

Lets get to it!

Settings for the meassurment of 550A (Image Left)

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fr Edit Content

Right away we can observe there is some minimal fr content, too minimal in my opinion.

Noise was very low I had to use a micro-scale to identify it, but its there.

Here is the plot

noise Edit Content


phs Edit Content

Phase is nominal

Lets look how the FR looks with the FLTR .


fr%20fltr Edit Content

Well we can clearly see a low/high pass response.

FLTR  Phase

phaser%20fltr Edit Content

From the phase plot we can safely conclude that the highpass is between 6 and 12 dB/octave and the lowpass is less than 6 dB/octave.


THD Edit Content

We can see that indeed there is THD content. It is not much but its not below either.

One thing that is very interesting is the fundamental.There are no artifacts around it! Which is a rare occurrence in the digital ‘analogue model’ domain! Also along with that is the order formation! We can see that the THD content is limited up to the 5th order, quite unusual (in a good way) as well.

API 550B

Settings used for 550 B.

phase%20 %20Copy Edit Content



fr Edit Content

We can see some FR content!

Again I had to use a micro – scale to identify noise

noise Edit Content

Its really not that much, but its there.


phase Edit Content

Phase is almost linear


Here is where it gets intresting…

The first time I saw the 550 B THD, It kinda felt familiar and I overlayed it with the 550 A.

They perfectly matched. I also conducted a more advanced measurement to confirm this.

So I can confirm they both share the same THD.

Below is the both 550 A/B THD overlayed to each other. Only the noise floor looks like its not overlapping but that is normal since the units have been overlayed periodically.

OVERLAYED%20A%20B%20THD Edit Content

(1.666% m/)

Analogue switch: When the units analogue is turned off, THD is subtracted along with noise, Only FR remains as is.




So the modeling is there, its less than I expected but more interesting that I anticipated. The only downside is the THD which is identical in both units.


Q: Is this really modeled after API 550 and if so to what degree ?

A:The only way to know,  is to cross reference data from the real API Module.

 PS1: In ‘analogue’ modeled EQ units bands behavior and characteristics are also modeled, but in order to evaluate this in this emulation, we would need the real source data.


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