EQ filter gain compensation

[MatiasR]

Hi, first post here.
Is there an option (if not consider this a feature suggestion) for REW, when calculating the EQ filters, to also include an overall gain compensation to avoid clipping?
Something similar like when I import my EQ settings to Equalizer APO and it shows below in red if there is a peak and how many dBs, and I add an overall gain control to compensate for it.
Thanks.

 

[John Mulcahy]

REW doesn't have any way to control the gain of an equaliser, but it does show the headroom required on the filter controls panel.

 

[MatiasR]

REW doesn't have any way to control the gain of an equaliser, but it does show the headroom required on the filter controls panel.

I am sorry, but where exactly is this shown? I did not find it.
Attached is an example of the EQ window and the Equalizer APO estimating peak gain of 12.1 dB.

 

[John Mulcahy]

It was added to the EQ Filters panel in V5.20 beta 14.

 

[Wayne A. Pflughaupt]

Seems like an impossible request as there are unlimited variables.

Starting with, where should REW prevent clipping? The processor itself? The downstream amplifier?

In addition, when it comes to hardware, no two pieces are alike in this regard. Some are clipping as soon as the meters hit red. Others have a “pad” built-in and intentionally calibrate meters on the low side.

Another factor is how hard the system is pushed. You could get away with 30dB of EQ gain if you’re only running at background-music levels.

That said, a good rule of thumb is to simple reduce the signal input level by the amount of EQ boost. IOW, with +12 dB on the equalizer, reduce the input signal by that amount. Not exactly precision, but it’ll get you in the ballpark. Keep in mind, that will only prevent the EQ from clipping, not any downstream amplifiers.

Regards,
Wayne

 

[MatiasR]

Then how come both APO Equalizer and the V5.20 beta 14 already calculate the exact headroom needed? On the example above, both calculated -12.1.

I thought that by adding another line in the EQ filters text file like "GN (gain) -12.1", then wherever it is imported would understand that a headroom of 12.1 dB is needed and adds a preamp gain of -12.1 before all filters.

 

[Wayne A. Pflughaupt]

How do you know APO calculates “exact” headroom needed? How does it know the headroom capabilities of any downstream equipment?

If it “calculated” a 12 dB reduction in preamp gain based on a +12 dB filter, there’s magic in that.

Am I missing something?

Regards,
Wayne

 

[MatiasR]

Both REW and APO Equalizer arrived at -12.1 dB, so there must be a way to calculate this in a standard way.

 

[John Mulcahy]

Filtering is often applied in the digital domain, so any overall gain in a filter set can cause clipping of full scale values. The headroom figure shows the attenuation required to avoid that.