User:ShinOBIWAN

From DRC

This page is under construction

Contents 1 A Guide to a PC based multichannel crossover with DRC and loudspeaker management. 2 The Software 3 The Evolution of my DRC Setup 4 Contact and Links

A Guide to a PC based multichannel crossover with DRC and loudspeaker management.

Introduction

Around 8 months ago I was introduced to DRC by a couple of people over on the DIYAudio.com forums. At that time I was playing around with analogue active crossovers and the usual passive varieties. I've got a fairly technical background and I'm a bit of geek at heart so anything like DRC sets my 'intrigue' alarm bell ringing. The fact it promised increased sound quality was a bonus but the real lure was just trying out something different. I suppose you could say my hopes weren't set high at the start and I was just looking foward to yet another avenue to explore.

Because of all the reservations I had about DRC and the fact that it was an unknown quantity with just a few folks recommending it. I decided to play it safe and try not to spend anything on new hardware. This of course immediately limited me greatly or so I thought back then, however it turned out that my chosen method for 'cheap' DRC - the PC, was actually the gateway to the very highest potential with the right equipment, software and of course, budget.

I'd dismissed the excellent DEQX and TacT setups because of cost but the fact is, those designs are the easiest and most user friendly way of getting into DRC. Its ironic that my setup in current guise actually cost more than the TacT TCS mkII, so its rather easy to get sucked into all this despite any intentions of cost saving. But nonetheless most folks will likely choose the PC to test the waters and this usually means, as I found out, that an equivalent setup using a PC is full of pitfalls, operating inconsistancies, incompatibilities and even reliability issues. However, its possible to work around this with carefully selected PC components, sensible expectations of what is possible and a correctly setup and streamlined PC system. It did take me quite sometime to perfect all that though. Sorry I'm getting ahead of myself but thought it worth pointing out that it isn't easy to overcome some of the initial hurdles and many folks give up at that point and miss a quite extraordinary listening experience because of it. Hopefully you'll read the rest of this and take idea's and setup suggestions that are known to work well and make your own PCXO system that actually works, I suppose my real aim with this document is to introduce others to DRC and help them avoid all the mistakes I made early on.

This guide focus's squarely on one approach that is undoubtedly the most powerful, flexible and most expandable solution to doing DRC on a PC. There are others that are cheaper or more efficient but I'll just be concentrating on what I know works for me and sounds spectacular.

What is DRC?

For a quick explanation of what DRC is and how it can benefit you and your system, read this guide Also check out the links at the bottom of that page for more thorough and technical analysis of DRC.

What do you want from DRC?

Its vitally important that you establish your requirements early on. This effects everything from your choice of soundcard to the power of PC required and through to the software you'll use. A whole host of questions need to be answered right at the start otherwise you'll just end up with a half hearted approach that doesn't actually do what you need.

For example:

I thought it would be nice to show you a list of what I wanted when I started down this route. Maybe all of these items are adequate or maybe you require something with even more flexibility. Eitherway, DRC is a great way to make an already good sounding system into something that's incredible, so don't be put off if what you want isn't in the list below because its likely that it can be done with the right software and/or hardware. Anyway here's what I wanted:

The Soundcard

I wasn't sure where to put this section of the guide but since its pretty much *the* fundamental foundation for a stable, reliable and well performing DRC setup I decided that it should be one of the first things covered in this guide. Its difficult to suggest a 'perfect' soundcard for DRC because there's many factors involved that will likely affect the choices in components.

For the method I'm about to outline later on one thing is for certain however and thats is you absolutely must use a card that supports the following:

It will become clear as to why these features are needed later but suffice to say, that without them, my method won't work and you'll have wasted good money.

So just what soundcards have these essential features? Well not many but here's the ones to own(there's very likely others but I don't have direct experience with them so I'll not post the details, if you do try this out with a card I haven't mentioned, please let me know via my email address at the bottom of this page and I'll add it in):

You'll notice I've listed the number of channels that the cards can handle as standard and also the potential possibilities with either external DAC/ADC's as is the case with the Lynx and RME or with manufacturer expansion boards ala. RME HDSP9632. Depending on the requirements you made in the 'What do you want from DRC' section above, you did read that right? This will determine which soundcard you require, it could be that you decided on 2 channel audio with DRC and that means just 2 outputs are required OR maybe you went the otherway with 5.1 DRC and a 3-way stereo XO for the fronts meaning you need 10 outputs (6 for the left and rights, 1 for the center channel, 1 for the subwoofer/LFE and 2 for surrounds).

My point here is make sure you either A) Select a card with enough inputs/outputs for your needs or B) get one that will allow you to expand in the future should you require.

I'd highly recommend the AudioTrak Prodigy 7.1LT as a starter card if your requirements are a basic DRC only setup with no crossover requirements, this card would be suitable for both stereo and multichannel setups thanks to its 8 outputs. The Lynx and RME cards/interfaces are great for the user who expects more and would like to future proof their DRC systems thank to the huge upgrade options available, another impressive feat is that you can use upto 3 of these cards in one machine to create a massively flexible system. Personally, I've used the RME HDSP9632 previously and then the Lynx and now an RME FireFace 800 in my current setup.

The PC Components

And now we move on to the rest of the PC that doesn't concern itself with sound but rather the processing and filtering aspects.

There's a couple of ways to tackle the whole filtering setup and the best is probably to split the PC DRC/XO system between two PC's - one is an audio server and the other a dedicated audio processing and filtering machine. Why do this? Well its the safest bet for a completely stable DRC and XO solution, there's no extraneous tasks being performed, the operating system remains consistant and streamlined and finally you've got 100% of the CPU's attention devoted to that one task of filtering audio. As you can imagine this is the best solution but is rather costly because you need to build and maintain two PC.

You can of course build a very nice 'all-in-one' single PC solution and my current machine actually handles all my audio filtering needs in one box. To highlight how well it performs; it plays HighDefinition video with 5.1 multichannel filtered audio seamlessly as well as simple 2 channel filtered audio. So it is entirely possible to build a great single PC setup but there is a catch - you've really got to be looking at the very best components to do the job right. So again 2 lesser PC's may actually work out cheaper!

I think the best bet is for me to pose a requirement situation and then suggest a machine spec that will handle My first suggestion will be for a single PC 'all-in-one' machine. Bear in mind that this was written in Jan 06 so if your reading this some time later it will probably seem all rather cheap or maybe even obsolete in light of the technology currently available. What it does give you is a good baseline to aim for and if your reading this a year or two down the line then you'll be able to build a similar PC for very little money!

This section is unfinished please check back later

The Software

And now we come to undoubtedly the most interesting and confusing section of setting up a DRC/XO PC. There's many suggestions for the software and even more suggestions for how it should be setup. Rather than try to create an ultimate guide to the software setup, what I'll do is rather just suggest what will work and how I use it, there's nothing like experimenting yourself for actually learning what a piece of software can and can't do, so ultimately you really need to get out there and just mess around with the stuff.

Console

This is the very heart of the software system, its a plugin client that allows you to pass audio signals routed from your soundcard through to the various plugins which process the signal and then after this the processed signal can be routed to the outputs on the soundcard ready to be sent onto your amplifiers and finally the speakers themselves.

To better explain what I mean by this take a look at the following screen grabs I've taken:

My routing scheme for Console.

Console in action showing XO, DRC and Delay functions

Its beyond the scope of this guide to suggest settings that will work with every PC or exactly how you use Console itself but what I can do is point you in the right direction and remember - experiment! If you want to know more about how to setup Console please visit these resources for help and advice:

Voxengo Pristine Space (Convolution Plugin)

Waves Linear Phase EQ (FIR Filter Plugin)

Voxengo Audio Delay (Digital Delay Plugin)

The Evolution of my DRC Setup

This section is unfinished please check back later

Its always interesting to see just how or what someone else did with their system, so I've put together the milestone points in my ever evolving PCXO setup.

The First Iteration:

It was confusing to say the least when it came to opinions on just what is the best way to do DRC and my first attempt reflected this. It wasn't a fully fledged DRC at all and was based around a VST plugin called Voxengo CurveEQ. It only corrected amplitude based errors or in otherwords, it flattened the frequency response. Worst of all though was the fact that CurveEQ is based around linear phase FIR filters which actually meant that phase errors were not corrected at all - not what you want for 'proper' DRC.

Like I said, I had very little understanding of the subject and was simply copying other peoples work and suggestions.

Contact and Links

For discussions on DRC see the following threads:

Anthony Thompson :: Email ZeroEX_15@hotmail.com