Hi all,
I have a set of speakers based on the Distribution Mode phenomena (see this post for a brief description and some pictures).
I would like to have more bass without blowing up the exciters. I have found a paper dealing with this topic by using the psychoacoustic effect of the “missing fundamental” (the paper can be found here). I understood that, with this effect, the brain is reconstructing the fundamental frequency from its harmonics thus giving the illusion to the listener of the presence of the fundamental. This means that, if a speaker cannot reproduce 50 Hz, one can create the illusion of the reproduction of the frequency by creating the harmonics (2nd to 6th) and injecting it in the speaker.
I would like to try it for my speakers.
A procedure is given in the paper and is the following:
- Apply a high-pass filter to the incoming signal so we don’t want to alter the bandwidth the speaker is designed reproduce (say 50 Hz to 20 kHz)
- Apply a low-pass filter to the incoming signal we want to create the illusion for (below 50 Hz in this example)
– Add distortion to this signal in order to generate the harmonics
– Apply a high-pass filter to the distorted signal in to remove the signals below 50 Hz
– Apply a gain to control the bass enhancement effect
- Sum signals from steps 1 and 2.
Do you know how to achieve this and implement it into Roon’s convolution filter?
Thanks in advance,
Ludovic
Hello Ludovic,
You can’t add distorsion with a convolution filter as it is a linear operation i.e. a combination of sums & multiplications by constants of the raw signal. Such linear combination do not generate new harmonics. A non linear operation (like squaring the input signal) is required. You can certainly find audio plugins for virtual bass but you’ll have to route the audio signal from Roon to a plugin host and then to your DAC…
Hi Home Audio Fidelity,
Thank you very much for your reply.
I finally used a DSP to regenerate the harmonics. It works pretty well except that It sometimes overloads the loudspeakers. I may try to shift the generated harmonics to even higher frequencies but I have to figure out how to do this.
I can post some details if you want.
Ludovic
Hi, I am looking sollution for virtual bass, can you post more details regarding such aproach? I am using DSP and FAUST programing language
Hi,
Sorry for the delay.
I used the DSP board from HiFiBerry and programmed it with SigmaStudio from Analog Device.
The equations I used can be found in the paper “Generalized harmonic analysis of Arc-Tangent Square Root (ATSR) nonlinear device for virtual bass system”.
I have to say, I don’t use the speakers using the Distribution Mode phenomena anymore, as i blew one up (not caused by the virtual bass system but by playing a very high dynamic range track and an amplifier with too much power for the speaker). I still use the DSP though on a Tivoli Model One to generate virtual bass and to tune the sound to my preference. The last DSP program can be downloaded here (please note that the file is available for 7 days only - I don’t know how to share a document for a longer period of time -).
To make very low frequencies audible on the small Tivoli One speaker, I chained the virtual bass algorithms. I admit that I am struggling to fine tune the rendered sound to my preference.
Last thing, the algorithm renders quite well transient low frequencies (drum kick for instance) but is not good for rendering sustained bass (bass guitar for instance). Another algorithm based on FFT is necessary.
Can you please describe how you use you DSP ?
Cheers,
Ludovic
1 Like
Thank you very much for your attention, I wil try to use more fundamental frequenciees rather than harmonics.