EQ Hi-Quality = Bad. (for somethings)

rhythminmind · Post by **rhythminmind** » Thu Mar 13, 2008 4:00 am

I tried searching for this but didn't pull up anything.

rhythminmind · Post by **rhythminmind** » Sat Mar 22, 2008 1:54 am

I thought some of you would be interested in my findings.

While creating my Transparent 4 Band Frequency Divider I found out that EQ8's Hi-Quality mode is not so High Quality.(So it seems)

When i was setting up the HP/LP filters for the audio rack I 1st used EQ8's in Hi-Quality mode. I was getting some bizarre audible artifacts. & also the mixed full-range output would not cleanly phase cancel.
This was most noticeable when using EQ8 as HP&LP filters.

So it seems yes you do get higher EQ frequency response but at the price of distortion.

My theory
Hi-Quality mode is a up-sampling process & my guess would be Lives/EQ8's resampling process isn't the best .
Checkout my Test session. Just enable Hi-Quality mode and see what happens. This is without a single active EQ band.
Test Project Download

sweetjesus · Post by **sweetjesus** » Sat Mar 22, 2008 2:36 am

yeah when using EQ8 on kickdrums i tend to turn off high quality mode, something about it isnt right but for most things its got a cool smoothness to it..

hard to tell whats really going on, but i havent always had the best results with Hi-Quality mode, now that's not to say that the low quality phasing may be doing something I like.. ?

SimonPHC · Post by **SimonPHC** » Sat Mar 22, 2008 2:38 am

but doesn't every EQ algorhythm, juts like filters, add some phasing to the signal? or is that the difference between linear and the other kinds? what sort of EQ is live's? And isn't this behaviour normal for the kind it is? Somebody more clued up, please answer.

(EDIT) Robert Henke should drop in, in about four more posts.

Tone Deft · Post by **Tone Deft** » Sat Mar 22, 2008 2:47 am

there can be linear phase EQs, they're harder to implement. this absolutely sounds like a phasing issue (low freqs are audibly more affected.)

http://en.wikipedia.org/wiki/Filter_design

Finite impulse response, or FIR, filters express each output sample as a weighted sum of the last N inputs, where N is the order of the filter. Since they do not use feedback, they are inherently stable. If the coefficients are symmetrical (the usual case), then such a filter is linear phase, so it delays signals of all frequencies equally. This is important in many applications. It is also straightforward to avoid overflow in an FIR filter. The main disadvantage is that they may require significantly more processing and memory resources than cleverly designed IIR variants. FIR filters are generally easier to design than IIR filters - the Remez exchange algorithm is one suitable method for designing quite good filters semi-automatically. (See Methodology.)

rhythminmind · Post by **rhythminmind** » Sat Mar 22, 2008 3:06 am

Phase is not the problem here. This is Distortion. My 4 band divider compensates for any phase issues.

Angstrom · Post by **Angstrom** » Sat Mar 22, 2008 3:16 am

third post,

which would make Robert next ...

Nogi · Post by **Nogi** » Sat Mar 22, 2008 3:17 am

rhythminmind wrote: When i was setting up the HP/LP filters for the audio rack I 1st used EQ8's in Hi-Quality mode. I was getting some bizarre audible artifacts. & also the mixed full-range output would not cleanly phase cancel.
This was most noticeable when using EQ8 as HP&LP filters.

In the infamous and now classic Robert Henke video provided by Tom COSM a couple weeks ago there was information about HQ mode for EQ8. This will provide some insight as to expectations when using this mode: http://www.ableton.com/forum/viewtopic.php?t=86647

As far as I can see, HQ mode phase cancels just fine.

Tone Deft · Post by **Tone Deft** » Sat Mar 22, 2008 3:20 am

Nogi wrote:
rhythminmind wrote: When i was setting up the HP/LP filters for the audio rack I 1st used EQ8's in Hi-Quality mode. I was getting some bizarre audible artifacts. & also the mixed full-range output would not cleanly phase cancel.
This was most noticeable when using EQ8 as HP&LP filters.
In the infamous and now classic Robert Henke video provided by Tom COSM a couple weeks ago there was information about HQ mode for EQ8. This will provide some insight as to expectations when using this mode: http://www.ableton.com/forum/viewtopic.php?t=86647

As far as I can see, HQ mode phase cancels just fine.

maaaaaad props if you can put up a time in that 90 minute video with the goods. seems like stuff from the first 15 minutes of that video.

downloading your example rhythminmind

Angstrom · Post by **Angstrom** » Sat Mar 22, 2008 3:20 am

hmm,
Ok, now does that count as a Robert summoning or not?

Tone Deft · Post by **Tone Deft** » Sat Mar 22, 2008 3:23 am

it's 4:20 AM in Berlin, hopefully Henke's asleep, or about to post some really stoned advice.

Nogi · Post by **Nogi** » Sat Mar 22, 2008 3:33 am

Angstrom wrote:hmm,
Ok, now does that count as a Robert summoning or not?

Basically...

Tone Deft · Post by **Tone Deft** » Sat Mar 22, 2008 3:34 am

Nogi · Post by **Nogi** » Sat Mar 22, 2008 3:43 am

Reference 8:40 - 14:20 for EQ8 HQ mode specific stuff in the Henke/COSM video.

Tone Deft · Post by **Tone Deft** » Sat Mar 22, 2008 3:47 am

the project is just white noise and an EQ8 with all the filters off. kinda lame man... it should be "download this file, hit play and you'll hear the artifacts."

so I'm supposed to dick around with EQ8 until I can stumble onto your findings? waste of time.

anyone else try this?

nice find Nogi!!