Impulse Filter

[weskola]

After recording an album I will manually remove the largest impulses using interpolate. From there I will filter using a threshold of 1, size 18, tracking 65, mode HQ. I will then run it with a size of 15 and then I will run it about 3 times with a size of 12. How many times is acceptable? Is the ultimate goal to reduce impulse to zero or is that even possible?

[HopHead]

Re: Impulse Filter

My problem exactly. For really bad LP's I have set up a multifilter with an LP first then three Impulse filters with progressively decreasing values and a DNF. Then I almost always have to manually declick the file, which is where the real work comes in.

However I have found that I can almost completely clean up the music using this method. For embedded "crackles" and other stubborn artifacts I have to use bigger guns!

[Craig Maier]

Re: Impulse Filter

It is never a good idea to run a low pass filter before running the impulse filter. The impulse filter needs all of the wideband information contained in the upper end of the frequency spectrum to perform its function properly. Using a low pass filter makes it much more difficult for this filter to discriminate between music and noise. If anything, some people use one of the pre-emphasis curves found in the paragraphic eq before running the impulse filter. After they are done de-clicking the wavefile, then they reverse the particular pre-emphasis curve with the de-emphasis curve of the same value or name in the paragraphic presets menu. If you desire to run a low pass filter, do it after all of the de-clicking has been completed.

[weskola]

Re: Impulse Filter

A couple of questions still need to be answered. 1) How many times is it acceptable to run the impulse filter? and 2) Is the goal to achieve zero impulses or is that even possible?

[Craig Maier]

Re: Impulse Filter

There is no limit to the number that you can run the Impulse filter. As for eliminating all of the clicks with this filter - - - the answer is that it depends on the material. I have some recordings wherein one pass of the filter gets rid of all clicks and other cases where there is no getting around the use of the manual interpolate function. There is no hard and fast rule - there are just too many variables in the equation. I tend to use the multifilter with different settings of each successive impulse filter for discriminating between the big pulses and the small stuff. That seems to be pretty effective for me. I hope that this is of some help.

[HopHead]

Re: Impulse Filter

Craig, thanks for your insightful comments regarding the use of the LPF. Could you please have a look at page 204 of the Millenium User's Manual and tell me what you think?

Tony

[Craig Maier]

Re: Impulse Filter

I checked page 204 in the manual (which I wrote) and it does say to use the LPF in extremely hissy situations as with very olde 78 RPM records. That statement in the manual is correct, but only applies in the most severe of situations and only with very early 78's (usually acoustic era.) For any other material (ie, normal electrically recorded 78's, LP's, 45's) the use of the LPF will hinder Impulse filter discrimination capability. Sorry for the confusion created by the manual.

[HopHead]

Re: Impulse Filter

Gotcha!!

I have removed it from my multi filter string

[Craig Maier]

The best filter to use to de-click a record in the later versions is the EZ Impulse. It has adaptive elements to it and is much more effective than the expert filter, which is primarily used in Forensics (radio static) work these days.