Audio Recording

I received an inquiry from a reader about “filters”. It goes as follows:

Hi,

I am presently reading your webpage and took the opportunity to ask of you a favour; I need to have a few channels of low and high pass filters.I looked at the Butterworth filters you mentioned but they are very expensive.Could you recommend a good but cheaper one?

Regards

Brian

Brian,

You have not mentioned whether you need digital or analog based filters, so I will answer your inquiry based on what is provided. First, the post that you have read might be referring to my tutorial on Low pass filter and High Pass Filter: Application in Home Recording Studio.

The filters discussed in that tutorial are software based filters in Adobe Audition. They are not hardware based filters although you can buy non-software based filters and they are very expensive.

My suggestion is that if you need a buy a filter, consider its application. If your application is for home recording and mixing studio, then the most practical and economical way would be to buy a DAW( Digital audio workstation) such as Adobe Audition because it already includes built in filtering actions such as low pass and high pass filter.

The filtering is done digitally using Fast Fourier transform and you could obtain accurate filtering actions like what is discussed previously with Butterworth filter on the article you have read.

Other than mixing and recording applications, then it’s out of the scope of this article and what you are looking might be the hardware based filters which can be useful in other signal processing applications not only in recording and studio applications.

If you still do not know, it might be worth reading to know the differences between analog and digital based filters here: http://www.dspguide.com/ch21/1.htm

Each has its own advantages and disadvantages, hardware filtering equipment works best for real time filtering of signals; however if you need to employ one at a time filtering, you might need a software based filters such as the one used in digital audio.

You can even employ digital filters in real time using computers but it will need a lot of CPU and memory usage in order to convert analog to digital signals which in some instances makes it impossible to convert in real time, so in this case analog filters works best. If you need a cheaper based filters, some would say analog are cheaper than digital filters in low volume applications:

Source: http://www.electronicdesignnet.com/cms/component/option,com_smf/Itemid,135/topic,17.0/

Choosing an appropriate type of filter needs some technical knowledge, so if you are very interested and technically incline you can take a look at this document here:

Source: http://www.etc.tuiasi.ro/cin/Downloads/Filters/Filters.htm

And you can properly select whether what type of filter is appropriate for your own application. Good luck.