4-band compressor for 1701

4band compressor.dspproj

Hello Kuba-s,

Thanks for the work. This is a great way to make a limiter work much better. If you need a crossover then how you did it is fine. but, if you only need a full-range output then we do have this block in the library for the ADAU1452/1467 series of SigmaDSPs.

Dave T

Hi,
Yes, yes, I know you have this compressor. Unfortunately, most amateur amplifiers only have a simple ADAU1701 processor, which can't run this block. My circuit does essentially the same thing.

Can you please make the project available? I'd like to play with it. I have a sub-band compander that I like the sound of; it drives a 3" speaker, companding sub frequencies for a 3" speaker for better sound and for protection.

Of course, I started this thread to share the project with others. However, I forgot to add an attachment to the first post, so I posted another one right below.
The parameters for all the compressors are tuned. All you need to do is add the block to your project and drive it to a maximum of 0 dB RMS. The lower the signal level, the less correction the circuit has. I recommend working between -10 and 0 dB.
It would be helpful to apply a noise gate, which I plan to do today.

Regarding your project, PBouvier251. I'm not sure, as I've never used it, but I think the Dynamic Bass plugin should achieve a similar effect to what you're looking for.

Have fun.

Hello Kuba-s,

A few years ago I wrote up a document to explain to a customer why they were getting high distortion using our compressor/limiters. As it turned out they were just setting the attack and release times too fast!! So I wrote up this document explaining it. You have to read it carefully and take it a step at a time. I walk through why it is a problem and then how to fix it.

So this document somewhat applies to this post you started. You are so right that filtering the sidechain of a compressor is a good thing to do especially if you want to do some heavy compression or limiting to broadband audio.

Here is a PDF version of the original PowerPoint file:

PDF

Dave T

Hi Dave-T
Thanks for the upload, informative document. To do something well, you need to know the basics.
Now I'm wondering what else processors do to the sound to ensure the final effect is good. A multiband compressor alone isn't enough.
Example: www.telosalliance.com/.../omnia-volt
I wonder what techniques and algorithms manufacturers use to achieve even better perceived loudness, sound clarity, etc. Unfortunately, I don't know where to find such information.

Hi,

I modified the previous program a bit and now it sounds better. The bass is processed differently, I reduced the sensitivity for that section, and thanks to that, I created a pseudo-five-band compressor ;-)
A noise gate has been added.
I encourage you to test it.
Regards

4b-compressor v2.dspproj.

Here's another version, which I've called auto EQ.
This time, there's no peak limiter. This version is more musical and dynamic.

At the input, there's a 3-band compressor, split between 250 and 5000 Hz, with the lower compressor less responsive to bass. A soft clipper is used instead. Then, a dynamic EQ is applied, which only operates at the peak of the amplitude. At the very end, a very smooth shelving filter is used. This is useful because the entire compressor block evens out the frequency response to a flat band, similar to pink noise, but sounds more pleasant when slightly attenuated. The recommended signal level is +/- 0.35 in 5.23 format.

By the way, if I understand correctly the operation of a stereo peak limiter: it works differently from an RMS compressor. In RMS, we had the sum of the left and right signals, whereas in a peak limiter, this makes no sense. Instead, the channel with the higher sample level is selected, then the threshold is compared, and the same gain is applied to both channels. (?)

Best regards, Kuba.

3-band compressor with dynamic eq.dspproj