Digital Room Correction - Friend or Foe?
Room interaction plays a huge part in how sound is perceived at the listening position. Even the best speakers are hampered by in-room resonance and reflections that bloat or obscure the sound at certain frequencies. In an ideal world, our rooms would be capable of a reasonably flat line audio response between 20Hz-15KHz (the audible range for most of us); the reality however is often far from this proposed optimum. Digital correction software works by playing a full-range frequency sweep, recording the response with a measurement microphone, and then inverting the measured response, thus smoothing room response artifacts.
Initial experiments were performed on the free open source DRC program called ACXO that unfortunately does not appear to support Vista 64 properly. The measuring aspect works fine on the Vista 64-bit OS; however, attempting to apply correction causes the program to hang without ever making a change. If you're using Vista 32 or XP 32-bit, we'd recommend you check it out.
As attempts to use ACXO with Vista 64 failed, I decided to go with the full version of Audiolense 3.0 for two-channel setups. The cost for the basic single user license is around $190, which is not exactly cheap for most of us, but we must recognize the level of work that goes into creating and supporting such products. There are a few alternatives to Audiolense varying in complexity, ease of use, and of course cost. For example, Acourate is a standalone package which seems to have more complexity to its GUIs than Audiolense, although there are video tutorials available on the Acourate website to help users get started.
The beauty of both Audiolense and Acourate is that both companies are new budding enterprises, which leads to support being handled directly by the authors of the software. We hope this continues as emails are currently handled within hours of being sent. Another software option is Art Teknika's Console that can be used with the Voxengo Curve Eq plug-in and used for DRC. The expansion possibilities with Console are huge, with plug-ins supporting digital crossovers and rerouting of input and output signals as long as the hardware used is capable.
Note that all of the software mentioned here features 30 day trial versions with limited functionality to give you a taste of what DRC is all about, so if you're interested but don't want to plunk down hundreds of dollars on something you might not like that's a nice option. You'll also need a measurement microphone and preamplifier. We're using the affordable Behringer ECM8000 and UB802 (now discontinued) to take room response measurements. In all, expect to fork out an additional $150 for these two components. The microphone preamp needs to support "Phantom 48V power" if you're using the ECM8000, so make sure you buy one that's compatible with this requirement.
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mindless1 - Monday, December 1, 2008 - link
The fact is, even audio streams that measure the same can and do still sound different. The problem is the resolution of measurement and the misconceived notion that the brain interprets sound at a fixed interval as measured.There's a lot of snake oil in the audiophile world, but there's also a lot of what you'd like to call "magic" only be cause you don't accept it as non-magic.
Any decent DAC would in idealized theory be as good, but in practice a different IC topology may lend itself better to certain inherant localized noise frequencies and cutoffs, be better mated to the circuit it's dropped into, have drifts from thermal changes, etc. If they were all the same why would there be so many? I will agree that which modern DAC is used in a reasonably good design matters less than what follows after it in the chain but the best way to minimize any potential for degradation is to start out with what is most likely to minimize it in every way possible then following this concept the entire time, waiting and seeing if the end result is audibly different rather than downplaying them all without knowing the additive result yet.
CSMR - Monday, December 1, 2008 - link
Yes if you are maximizing quality you will choose the best of all components. But it's more sensible to care about cost and time too, so you have to prioritize. The value of the research about the unimportance of DACs (at at beyond a certain level) is that you can stop worrying about this part of the chain and spend you time/money where it is important.JonnyDough - Tuesday, December 2, 2008 - link
Exactly my point. Why spend more on one component if it's going to be "bottlenecked" by another one. Spending $2000 on a nice amp is crazy if your other components are crap. I think in the end it's like all other techs. You want decent stuff for a reasonable price unless you have more money than brains. While I scoff at people willing to spend more than few thousand on a sound system, without them we wouldn't have gotten to where we are today - with good possibilities on the market. As long as you like what you hear, who cares if it's perfect? At one point is something "good enough?" I mean honestly, there are people starving in the world, friends dying of cancer, etc...and we want to worry about whether or not something is inaudibly "perfect." Blow your money on something that MATTERS, you can't listen to music every hour of everyday unless your job is singing.CSMR - Tuesday, December 2, 2008 - link
I meant you can spend time/money on speakers/room acoustics/dsp but food for starving people is admittedly a better use of time and money.JonnyDough - Wednesday, December 3, 2008 - link
That's actually a matter of perspective. For example, you can donate food to a starving kid in some third world country and next thing you know that child has three kids and no way to feed them - and you've just marginally made the problem worse, not better.I think money is better spent on education, which leads to fewer babies. Many countries do not have quality farmland that can support the population on their own (the U.S. supports a large percentage of the world's population). Then there's natural habitat destruction, pollution from oil for having to ship food to them, etc. You get the picture.
JonnyDough - Monday, December 1, 2008 - link
While I was generally agreeing with CMSR above, I guess what everyone ends up saying is that hearing is subjective, which is something audiophiles are always agreeing upon yet they still love to argue over things.Does a vinyl record produce better sound than a CD?
It depends on what an individual values most.
A CD may produce less static noise, but have a "duller" sound, seemingly less highs and lows. It all depends on what one appreciates with their own ears.
While there are measurements that can be taken in a closed chamber, one sound system might actually sound better in a specific home or room than another for whatever reason. Even so, the average person can rarely tell a difference these days between the moderately priced components.
The really silly thing is that people will spend $200 on a sound card and then use cheap plastic speakers.
Rajinder Gill - Monday, December 1, 2008 - link
Lol, it's ok, everyone in entitled to have their say.It's the first piece so bear with us while we try to cater to a wider set of ideals.
With regards to the obj/subj stuff, it's an argument that'll never be solved.
later
CSMR - Monday, December 1, 2008 - link
Sorry if I came on too strongly; I was just expecting that Anandtech would have not necessarily an expert take but at least a more technical take than you get in audiophile communities.I would do some more fundamental thinking about what are the key factors in computer audio playback.
As a start you could rank in terms of what is most critical:
computer performance, computer quietness, software (drivers, dsp), analog line out, volume control, amplification, cables, speakers, room acoustics.
I won't give you my list but you should think about it and it is possible to compare many of these things in a very quantitative way, and some are more important than others by several orders of magnitude.
AnnihilatorX - Monday, December 1, 2008 - link
A dumb question about correction.The theory behind it is simple enough, but why do we need dedicated hardware to do the correction? Why can't we use simple graphical equalizers? I understand graphical equalizers are quite discrete in the range of selectable frequencies. How much difference does it make?
Rajinder Gill - Monday, December 1, 2008 - link
DRC - ease of use and range of control, plus taking care of things in the digital realm rather than in the analogue.You could fudge some control with a multi band digital equaliser and the means to measure the response, but it'd be damn tedious and utimately limited.