P Tucci: I took a stab at Bink’s question on the forum and said that the Contour seems to have user defined phase response/group delay. Did I understand the white paper?
Bruce: Yes, at the lowest level, you have control over the magnitude and the ability to have a non-minimum phase response within the limits of the very short 2-millisecond delay from input to output. Dave, anything to add?
David McGrath: That white-paper relates to an EQ module Lake developed for its Huron workstation many years ago. We’ve refined the methods since then, but found that plain-old minimum phase sounds the best.
Bruce: I should point out that there are FIR filters available also, which give a perfect linear phase response.
P Tucci: You’re trading group delay for a more linear phase response?
Bruce: Are you referring to the EQ? Or the crossover?
P Tucci: Well, I read about the EQ, let’s talk about that one.
Bruce: The EQ is minimum phase. In our original design, we wanted to have the ability to stack up an unlimited number of arbitrary EQ curves yet still maintain a constant delay/ This required a new way of slicing up the audio and hence, our proprietary solution. Dave, you want to add anything that doesn’t give it away?
David McGrath: Ultimately, you are using the various shapes (bandpass, shelf, Mesa) to create an arbitrary frequency response curve. The Contour then automatically creates the minimum phase response. Designers who want to get in and add non-minimum-phase EQ to their speakers can do that, but they need to work with Lake to ‘bypass’ the standard GUI.
Jon: So it essentialy ‘reads’ your combined filtering and creates a response with minimum phase shift?
Bruce: Yes, that is correct. In the crossover, in addition to all the traditional crossovers, you have the brick-wall linear phase crossovers that require you to give up some additional delay. The software optimizes the brick-wall filter for however much delay you are willing to deal with.
For example, 25 milliseconds is a disaster for monitors but perfectly usable for the house PA. Additionally, there are more parametric sections available in the crossover that allow you to add traditionally shaped parametric EQ to individual crossover bands.
Bink: In practice then, I can throw a sharp parametric or cosine filter at one speaker bandpass, placing it right near the crossover point, and this won’t require me to re-time the neighboring bandpass.
Bruce: Correct!
P Tucci: Where do the FIR filters fit in?
Bruce: There are limited to creating the crossover section.
Bink: The Contour has a Windows-based GUI. Do you have any plans to port it to other operating systems?
Bruce: The GUI is based around Direct X. We have talked about ports, but poor Marcus Altman, our sole programmer, would string me up, if I even brought up the subject, so the answer is, “no.”
Jon: There are the traditional filters such as L-R (Linkwitz-Riley), Butterworth, Bessel – or do you create the filters?
Bruce: Yes… every one that we could imagine.
Abdul EQ: What exactly does your marketing department want Abdul to think about Contour’s “abilty to control sound in EVERY seat in the house?”
Bruce: I asked myself the same question. The basic idea is that you’re freed to wander to every seat in the house to create the optimum response everywhere, but I don’t think the ad really gives you that message.
David McGrath: Remember, modern line arrays mean that different areas in the venue will get coverage from different speakers, so walking the floor is more necessary than ever.
Bink: What tours might we have heard that would be a good demonstration of the Contour in action?
Bruce: That’s a hard question. It’s been out on easily 70 Clair and Showco tours. In fact, I understand that it won’t be long before it’ll be on all Clair and Showco tours.
Douglas Carmichael: Does the contour have security lock features for permanent installs?
Bruce: Yes, there is password protected designer mode that gives you access to all functionality. You can decide what you want the user to see and set up limits as to how much they can adjust any parameters you choose that they can mess with.
For example, you might only want adjustment of the crossover bands within a 3dB window. As well as user mode there is an additional mode called show mode which is even more restrictive so that you can’t make great big boo-boos.
Douglas Carmichael: Is there any offline editor program ala XTA AudioCore that i could download to ‘play’ with its features?
Bruce: We will have the software available for download at anytime. You can place a dummy module in the work area and treat it as if you are actually connected via ethernet to a real module.
Moderator: OK… last question… and it’s a tough one… :>) And thanks, Abdul, for the compliment!
Dave D: what’s better, Spacely Sprockets or Cogswell Cogs?
Bruce: That is a tough one. I always liked Mr. Spacely better.
Moderator: Well, it’s a wrap. thanks so much to Bruce, Terri and David for spending time with us tonight.
Bruce: Thanks very much for having us… and thank you to my wife, Terri for typing three times faster than I could ever hope to. Good night all.
Moderator: Thanks to chat.boy for getting this room up and working and feel free to continue the chat in the Live Sound Chat room. Great questions, audience. Good night!
Also view related materials:
Bruce Jackson: A Life In Sound
Inside The Design Of The Lake Contour Processor
Bruce Jackson Interview At Integrate 2010