Hi-Pass Filter

[rorygirl]

I'm in the process of cleaning up my mixes and
putting a hi-pass filter on everything from the
guitars to tambourines and I'm noticing that
some of my tracks are now clipping. Why would
that be happening if I'm cutting frequencies?

[irishharry]

Can you put screen shots up? Was it close to clipping before?

[rorygirl]

For some reason, I don't have permission to post attachments.
Anyway, it's not clipping on every track but I noticed as I put
a hi-pass filter cutting 250 Hz on the vocal track it started to clip.
Same for tambourine. They weren't close to clipping before.

[daeron80]

That's just the way it works. There are two reasons I know of. One is that filters shift phase, and new phase relationships in complex material are likely to cause some peaks to be higher, some lower. The other is that low frequency waves carry high frequency ones. If a sharp transient happened to be sitting in a trough, it might not clip; remove the low freq trough, and tink!

The solution for future tracks is to leave headroom. A good 12 dB. Your mixes will sound better, not just because it eliminates clipping, but for a host of other reasons. One biggie is that you won't be worrying about not clipping, so the mixes will go quicker and more intuitively. Another is that A/D converters start to run out of headroom when pushed hard. They just sound better if your peaks stay down a dozen dB.

[Stiff]

Maybe some kind of compressor/limiter/other dynamic-thingie that behaves differently now that you're cutting lows?

[albee1952]

Or, try a different EQ plugin to see if that helps. You could also try moving the hi-pass plugin to the last slot so other plugins do their thing first(although putting the Hi-pass first would be my usual spot).

[daeron80]

In general, linear phase EQs are less prone to cause increases in peaks (although they still can). Unfortunately, they also don't usually sound as good. I know of no hi pass that causes greater peak increases than the ones modeled on old Neve consoles. But, dang, things sound so much better! Maybe it's because it's peakier? More dynamic?

[rorygirl]

Thanks for the suggestions. I always leave plenty of headroom, but will try another plug-in and also try placing it first in the chain and not last.

[nedorama]

Most EQs have level controls so that after applying EQ, you can trim up/down the output level - if this isn't the culprit, you have have phase issues and I'd try another EQ.

What EQ's were you using, and what else was in the signal chain and in what order?

[rorygirl]

I was using the Digirack 1-band EQ with the input level set to 0 db and I was putting the EQ last in the chain.

Also - while I have your attention:
http://duc.digidesign.com/showthread.php?t=277140