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[duckhunter]

This is why I can't talk to my two daughters who are engineers about their studies and work.  I tried to review my daughter's thesis and had to put it down after three pages because I couldn't understand a thing.

[Andrew Hamilton]

I'm glad that we're getting to talk about IIR and FIR.  I thought I read long ago a post that Daniel Weiss wrote in which he explained that his linear phase eq was the only one out at the time which was FIR.  I believe that he stated that FIR is best (most transparent?) for linear phase eq.  There was an early Arboretum plugin called Ionizer which was linear phase (128 bands), but I believe that it uses IIR filtering.  Bruno, or DC, can you please clarify this recollection, and, if true, are there any _minimum phase_  eq'z that use FIR?



Andrew  

[bruno putzeys]

Andrew Hamilton wrote on Thu, 19 June 2008 08:55

are there any _minimum phase_  eq'z that use FIR?

I wouldn't see the point. Although minimum phase does not imply IIR, all normal audio EQ functions are IIR in nature so a FIR filter could only approximate those. That would further go at the expense of lots more processing power. The only advantage I could think of is that no rounding errors are fed back. With double or extended precision processing that shouldn't be an issue anyway.

[cerberus]

thanks bruno for that eye and ear opening explanation.  the math may confound
us, but imo the priniciples you've outlined are basic and should be
understandable, even to a math idiot like myself.

but myths persist because people like them. so i hope you will repeat
the information again here whenever you notice someone
assuming a wrong idea about filter design. as we all
know, certain brands of eq are revered among
the top m.e.s. but we rarely talk about why.

it helps me that i spent time carefully selecting cutoff and q  numbers for
[izotope's adjustable] src. the parameter entry allows variations up to
four decimal places, but most eq faceplates don't get
that specific.  i heard significant differences in
character from changing these numbers
very slightly. so a q of 1.000 and
1.002 could sound different...

but if one were designing an eq,
it would seem logical to  
label that setting
simply as: "1.0".

jeff dinces

[Matt_G]

Getting back on topic, I've been using the Sonoris LP EQ v2.1a as an FX Pansion wrapped RTAS plugin in Pro Tools HD & unfortunately it's very buggy If you type in the parameters it often crashes Pro Tools to the finder. If you close the GUI window while it's playing back it goes into a playback loop & than crashes Pro Tools.  The latency is insane over 66000 samples! The only way I can use it stably is to manually dial in the parameters I want while Pro Tools is stopped, close the GUI (pray) & then hit play. It works fine in this way. It does sound good though, just a pity it is almost unusable in a practical way.

Now in Sonoris' defense this is a VST plug-in & wasn't tested for stability as a wrapped plug-in in the Pro Tools environment. But usually I don't have any problems with wrapped plug-ins.

I'll post this to Sonoris tech support as well.

Sigh...

Matt

[Matt_G]

Wow how's that for service, I emailed Pieter & he has already given me a download link to 2.1b which has fixed one of the problems (GUI closing crash). He is looking into the other issue & maybe considering RTAS support in a future release. Impressive...

Matt

[cass anawaty]

Yes--the update improved things here also.

What's with the gain in bypass?  Can someone explain why this happens--i.e. is it a function of the design?

I'm happy to have it--thanks for the rec, Steve.

[TotalSonic]

Cass Anawaty wrote on Fri, 27 June 2008 11:13

Yes--the update improved things here also. What's with the gain in bypass?

There's no gain when the plugin is in bypass in the SAWStudio version - don't know about the VST though - what host are you using?

Best regards,
Steve Berson

[cass anawaty]

TotalSonic wrote on Fri, 27 June 2008 17:13

Cass Anawaty wrote on Fri, 27 June 2008 11:13 Yes--the update improved things here also. What's with the gain in bypass? There's no gain when the plugin is in bypass in the SAWStudio version - don't know about the VST though - what host are you using? Best regards, Steve Berson

Sequoia.  I wasn't sure if the upsampling was causing the "overs".  It's not anything like a couple of db--less than that, but noticeable.

[PieterS]

Cass Anawaty wrote on Fri, 27 June 2008 20:42

What's with the gain in bypass?

The bypass is a soft bypass, meaning that upsampling is still functioning. This is to prevent shifts due to the latency.

The upsampling can cause overs, that's probably what is going on.

[cass anawaty]

PieterS wrote on Fri, 27 June 2008 20:21

Cass Anawaty wrote on Fri, 27 June 2008 20:42 What's with the gain in bypass? The bypass is a soft bypass, meaning that upsampling is still functioning. This is to prevent shifts due to the latency. The upsampling can cause overs, that's probably what is going on.

That explains it--thanks Pieter.  I'm really enjoying have this.

[Matt_G]

PieterS wrote on Sat, 28 June 2008 05:21

Cass Anawaty wrote on Fri, 27 June 2008 20:42 What's with the gain in bypass? The bypass is a soft bypass, meaning that upsampling is still functioning. This is to prevent shifts due to the latency. The upsampling can cause overs, that's probably what is going on.

If you're operating at 96kHz as the native sample rate does the EQ do any resampling?

Matt

[PieterS]

Matt_G wrote on Sat, 28 June 2008 02:40

If you're operating at 96kHz as the native sample rate does the EQ do any resampling? Matt

No, upsampling is only enabled for samplerates below 50KHz

[PieterS]

Matt_G wrote on Fri, 27 June 2008 16:15

I emailed Pieter & he has already given me a download link to 2.1b which has fixed one of the problems (GUI closing crash).

The update is now available for the demo and full versions of the Sonoris (LP) Equalizer at http://www.sonoris.nl/catalog

[Andrew Hamilton]

Andrew Hamilton wrote on Thu, 19 June 2008 02:55

...I thought I read long ago a post that Daniel Weiss wrote in which he explained that his linear phase eq was the only one out at the time which was FIR. Andrew

Well, after reading the .pdf for the Weiss lin ph eq, I gather that not only does he use IIR, just like Sonoris, but also does the same time-travel front-back thing for lin ph.   (So much for _my_ memory.)


Andrew