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Digital Room Correction Thread  

post #1 of 570
Thread Starter 
I found a directX, parametric-eq plug-in, which allows, in real time, to program an unlimited (but depends on your cpu, I believe) number of filters (unlimited bands). The only problem is that I can only work with it "offline" currently, because I've only been able to activate it with a sound editing program like Cool Edit Pro. Working off line is not that bad, because I can save the corrected .wav file, and then play it with an ASIO player, and enjoy both worlds, but I really want to have an option to run it with an an audio player in real time. I think that the problem is a bit more complicated, because this is not a pure direct X plug in, but a VST plug in. I use Cakewalk VST v4.3 in order to make it compatible with DX, but not all programs can work with it.

post #2 of 570
Sounds cool. Where can I get it?
post #3 of 570
I think MC9.1 supports (or is trying to support) DirectX Host Plugins. I've never used it and don't know anything about it. So, please check MC9 forum for more information.
post #4 of 570
Winamp has a DirectX Plugin Adapter Module (dsp_adaptx35.dll). You should try downloading that.
post #5 of 570
Thread Starter 
Damn it!!!. I've just found that this plug-in is not what I've wanted!. I thought it uses Fir filters, but to my dismay, it uses IIR filters.

Here is a small explanation about the difference between the two:
taken from here:

This is a scary concept but here goes: All filters suck, some more than others. Whew, I’ve gotten that off my chest. Now, what’s the bottom line here? Well, filters or EQ can be built in two flavors, either Infinite Impulse Response (IIR) or Finite Impulse Response (FIR). Most filter that we interact with on a daily basis are of the IIR type. They trade off a frequency–dependent amplitude boost or cut in return for some amount of frequency–dependent phase shift, also known as group delay. Unfortunately, that’s a problem…although we expect them to operate in the frequency domain, they also muck up the time domain. To understand this group delay thing, think of your basic two way loudspeaker (see figure 8 below). The tweeter and woofer are both mounted on the front baffle. The tweeter’s tiny voice coil is very close to the baffle while the woofers large cone offsets it’s voice coil back quite a bit from the baffle. Now, the voice coil and cone comprise the motor that makes a speaker move air so broadband sound launched from the woofer is offset in time from the tweeter’s output by the physical displacement between the two devices. That’s why many loudspeakers have slanted back-leaning front baffles, which time aligns the drivers.


Figure 8 - An simplified version of group delay via frequency-dependent acoustic delay

This is classic group delay, where the high frequencies from the tweeter arrive at your ear before the woofer’s low frequency content. Think of what this “time smear†does to a broadband sound like a tasty kick drum, a signal with both the HF snap of the beater and the LF boom of the shell’s resonant cavity. Anyway, this same time smear or group delay occurs in all IIR filters to a greater or lesser degree. The only difference is, unlike a speaker, in electronics the high frequencies lag while the low frequencies lead.

As to FIR filter, they exhibit a constant group delay regardless of frequency, so no wonky phase shift problems but, they have a different problem: pre–echo. FIR filters have an annoying tendency to present a small amplitude version of their input at the output, before the input has been applied! I know, what have I been smoking? Nothing, old boy, I simply haven’t mentioned that FIR filters cannot be built in the analog world, only in the bits and bytes of a digital implementation. So, a rip in the time–space continuum that I’ve just mentioned is taken for granted in digital signal processing circles…It’s just one more thing a designer must contend with.

The upshot is that FIR filters, since they lack group delay, don’t “sound†like EQ as we know it. Because of their sonic neutrality, they’re usually used only for specialized correction like in mastering, forensics…or restoration! Though they don’t exhibit group delay, they do impose significant latency due to significant computational overhead.

Now, I asked the company who created "Eqium" (the parametric eq IIR plug in) the next question, in order to see if they have a solution for the IIR prblems:
I've learned that your Eqium plug-in uses IIR filters (and not Fir filters, like Firium).
IIR filters are notorious for their group delays (phase problems).
I can not accept group delays in my work, so I would like to know if you
know of a program which can solve the group delays that your Eqium software

This is their answer:

Thank you for writing to us. You are correct, Eqium, like most other EQs, utilizes IIR filters which do not provide a linear phase like FIR filters. I do not know of an application that will "correct" this. Though you regard the effect of Eqium's IIR filters as a problem, virtually all EQs (software and hardware) are modeled similarly and thus exhibit the same behavior. It has only been more recently that an alternative (FIR filters) to this traditional type of EQ/filtering has been made widely available.

I hope you will continue to use Firium and that you are able to find uses for Eqium for which its more traditional EQ characteristics are a good match. I hope I was able to answer your question to your satisfaction. If I was not, or if you have any other questions or comments, please let us know. We appreciate your continued interest in our products.

Kind Regards.

Customer Service
Elemental Audio Systems
I'm searching for a Fir filter based parametric eq plug-in, so hard, but can't find it. I've found Fir filter *equalizers*, but that's no good for room mode correction (we need adjustable bands. Constant bands are no good). I simply can't believe no one has creaed a Fir filter parametric eq software.

I'll keep looking...
post #6 of 570
Well, here's a program to wrap a vst plug to use in directx


It will wrap a max of 2 vst plugs cause its demo. Once wrapped, it'll be available in directshow--think zoom player. This way is free. With adaptx, you'll have 2 pay. (adaptx is also available for wmp9 and winamp3).

I had a long reply prepared, but i was automatically logged out. I c now u don't want this plug. There are many directx and vst mastering plugins u can use in directshow. Some of them are free, and others cost as much as $300 just for a 10band eq.

Check this site out for directx plugs:


Let me how things go.
post #7 of 570
What about Shibatch Super Equalizer?

Shibatch Super Equalizer is a graphic and parametric equalizer plugin for winamp. This plugin uses 16383th order FIR filter with FFT algorithm. It's equalization is very precise. Equalization setting can be done for each channel separately.

I used it alot when I had my previous speakers (Paradigm Monitor 7), and no subwoofer. With the equalizer I gave the low frequencies a huge boost, thus giving me way better and deeper bass.
I friend of me also used it with a pair of CV AL-1000 speakers to make their 15" woofer actually move. :)
post #8 of 570
Thread Starter 
Esben, this looks really good. Thanks!.
Do you know how does this filter deals with the pre-echo problem of Fir filters ? (if at all). Have you found this equalizer to be neutral ?. What are you using now ?.
Can this plug-in work with the ASIO or Kernel streaming plug ins ? (ie. no kmixer's SRC in the way).
post #9 of 570
Thread Starter 
Esben, I've checked it and the "Shibatch Super Equalizer" plug in has no cure for the pre-echo fir filter artifacts, which leads to ringing just before transients or sharp attacks (I have confirmations for this from several sources).

As it seems, the one and only software which has all the features that I need (and much, much more), is Denis Sbragion's Digital Room Correction (DRC) v2.2.0.
I'm currently studying it, and I hope that by tomorrow I'll have first impressions about it. If only the user interface wasn't from the 80's, I would have started using it months ago.

Anyone who wants to give DRC a try, here is a "step by step" guide which will make things easier.
post #10 of 570
As far as parametric eq--it allows u to adjust the level, frequency, and q(bandwidth)? Is that right?

Have u tried this site. It's only 5 bands, though. Don't know about the echo thing.


I also know of a 30 band (non-parametric) fir eq.
post #11 of 570
Thread Starter 
As far as parametric eq--it allows u to adjust the level, frequency, and q(bandwidth)? Is that right?

Have u tried this site. It's only 5 bands, though. Don't know about the echo thing.
The problem is that the bands are limited to regions, which render them useless for my needs.

I also know of a 30 band (non-parametric) fir eq.

Anyway, the problem is not with finding a parametric eq with fir filters (Esben gave me a link to the exact thing that I asked for, in the beginning). The problem is with finding a software which will also take into acount the pre-echo artifacts of the fir filters. The only thing which does everything I need is DRC V.2.2.0, but it turned out to be WAY more complicated than I've expected. The step by step guide is only good for old versions. I think that I'll try to live with SuperEQ's pre-echo artifacts for now, until something better hits the market.
post #12 of 570
Originally posted by Yoniza
This is a scary concept but here goes: All filters suck, some more than others. Whew, I’ve gotten that off my chest.
Maybe that's what's keeping ElvisIncognito from posting about using smiley faces - or he is AWOL... :)
post #13 of 570
Thread Starter 
Maybe that's what's keeping ElvisIncognito from posting about using smiley faces - or he is AWOL...
Why ?, does Elvis uses filters ?.

Btw, I think that this sentence ("all filters sux") is a bit misleading. True, both IIR and Fir filters have their limitations, but in some cases, NOT using them, and just living with what your room's acoustics have to offer, is simply unacceptable, by audiophile standards, at least (especially in the bass region - below 100hz). Anyway, Fir filters (and not IIR filters) are definitely the way to go.
post #14 of 570
Sounds like u need to relax a bit. Have a swig of black label bro.

If ur gonna use superequ and want a better player than winamp, there are a couple directshow filters that allow u to use winamp2.x plugs in ds. One is by the same guy who does ffdshow (heard stability is a bit iffy). The other is called dc-dsp. Alternatively, u can of course use winamp 2.x plugs in media jukebox/media center.
post #15 of 570
Thread Starter 
Thanks for your help, but Winamp is a fine player for me, what I asked is a better eq software than supereq.

Anyway, I'm starting to do some real progress with DRC. More on that later.
post #16 of 570
Yeah, I here ya yoniza. But, what u originally asked for was a player to accept directx plugs. You were willing to use supereq so i was just trying to give ya more player options.

Good luck with drc.
If I ever run across anything with a gui, will let u know.
post #17 of 570
Thread Starter 
Sorry, jlo, you are right, I do change my needs frequently. But don't blame me, since I'm still in the process of learning this subject.

Btw, (new need) does anyone know where can I find a decent MLS measurement software which is both accurate and inexpensive (preferably free) ?. All the softwares which I know, like ETF 5, cost at least $150 USD, which is a lot of money, considering I don't need to use any extra feature except basic MLS.
post #18 of 570
Well, this is a sound card with excellent DSP hardware and software For $399 at - http://www.musiciansfriend.com/srs7/.../base_id/57542

"Its high reliability and sensational price make Luna II possibly the most desirable audio card for computers running Cubase VST, Logic, Nuendo, GigaSampler and all other popular audio software. Luna II is also the only I/O card in a wide price range that provides you with all the important benefits of a solid DSP architecture! Luna’s unique latency-free routing capabilities and the on-board "live" digital mixer (with advanced surround capabilities and effects) make Luna a valuable enhancement for every audio computer. Luna II is even compatible to the huge Pulsar/SCOPE platform DSP plug-in library."

I made a price/features list for Creamware cards:

Creamware Luna 2496 I/O box $425.00
Creamware Luna II - latency-free routing and surround capabilities, on-board digital mixer $399.99
Creamware Luna II EX - + ADAT Expansion Board & Vocodizer plug-in. $595.00
Creamware PowerPulsar II - 15 SHARC DSP chips, digital mixer, effects $1,995.00
Creamware PowerSampler II - 4 channels I/O, MIDI I/O, SFP software, Vocodizer Plug-in $595.00
Creamware PowerSampler II EX - + expansion plate w/2x ADAT I/O and 1x Zlink connector $745.00
Creamware Pulsar II - 6 SHARC DSP chips, digital mixer, effects $995.00
Creamware Scope /SP - 15 sharc DSP chips, extreme DSP power, SCOPE software package $2,995.00
Creamware Scope SRB - 15 Sharc DSP Chips accelerator for Pulsar and scope systems $1,695.00
Edirol DA-2496 - 8x8 audio recording interface $519.00

Just a few months ago, MIDI latency in most inexpensive sound cards (or interfaces) was so dreadful that most synth-heads scoffed at the idea of playing or controlling a soft synth in real time using MIDI. To combat this problem, CreamWare has created Ultra Low Latency Interface (ULLI) and included it on the Luna II card. As I tinkered with MIDI instruments such as Native Instruments' Battery 1.0 in Logic Audio, Fruityloops' DirectX instrument DreamStation, and Reason's Subtractor synth and NN-19 sampler, I was delighted to find that MIDI latency had all but vanished. Nearly undetectable latency at this price is a serious accomplishment, and CreamWare deserves a pat on its virtual back." - http://remixmag.com/ar/remix_luna_landing_creamware/

"You can still use your favorite DirectX plug-ins inside your audio application (upstream of the Pulsar), and then let Pulsar’s digital mixer handle mixing and any other EQ, compression or other effects you wish the Pulsar to provide." - http://www.google.com/search?hl=en&i...amware+DirectX

Tong Chia here at AVS highly recommended them, no KMixer too. :)
post #19 of 570
Thread Starter 
Nice card RayL Jr, real nice.

Anyway, just wanted to let you know that I made the final step today with DRC. I'm now fully capable of operating the entire Room Correction process, starting from the MLS calibration, and ending at the final convolved real time playback, for stereo sources.

I even made some playback tests today, which were all horrible, but later at night I figured out all the mistakes that I did, and tomorrow I'm going to test it for real, for the first time (to bad I only have a Rat Shack to test it with...)

As of now, the good news are that the entire process is cheap, dirt cheap. Basically, all you need are CoolEdit Pro (or 2000) + a decent mic (preferably with a separate pre amp, not like my rat shack) + some other free sharewares , that's it.

The other good news is that the entire process is VERY easy to do and pretty fast, if you have someone who can tell you exactly what to do (I wish I had one), you really don't need to have any special knowledge about anything.

We'll see what happens tomorrow.
post #20 of 570
Thread Starter 
Well, I had to dig pretty dip to get to this thread again, so I'm not sure if anyone is still reading it.

Anyhow, I've promised an update, so here it is:
I've been doing tests all day, and the interim conclusion that I got to is that my rat shack simply wasn't made for room calibration. If the type of sound that I got was in any way representative of the quality of DRC, then I'm sure that its creator, Denis Sbragion, wouldn't have bothered with it beyond v0.001.
I've sent him my findings, and I'm waiting for his comments, but I'm afraid that if I'll want to really test DRC, as an audiophile tool (and not just a gimmick) I'll have to spend money on a better mike. We'll see about that tomorrow.

Part of me is kind of sorry that I started this DRC journey, since I didn't plan on spending more money now. The only problem is that I've spent so much time figuring out how everything works, that I simply can't allow myself to throw everything away and stop.
post #21 of 570
Please tell how your room correction works? You're not trying to correct over ~120 Hz, are you?
post #22 of 570
Thread Starter 
Esben, everyone, I have great news!!!.
Apparently, DRC outputs two files at the end of its calculations, one should be used as the "equalizing filter" (and the other is the impulse response of the system after correction, and it is useful to see the results achieved after correction), the thing is, I was convolving using the wrong file!. (It appears that my Rat Shack isn't THAT bad afterall).

Denis Sbragion was kind enough to go with me over all the possible problems that might have occurred. He told me that my Rat Shack mike really isn't up to the task of doing an accurate room measure for room correction, but it should sound much better than I've described. Also, according to some test signals that I've sent him, he told me that this mike is going to give me an overly bright image.

He was right, about everything. As soon as I started using the correct filter, the sound improved, dramatically. Also, it exhibits exactly what Denis said, an overly bright presentation, which really makes things sound compressed at the high frequency region. Anyway, I decided not to care for now about the high frequency region (since I can't do anything about it, yet), and test how my system (and especially, my room) sounds from the sweet spot.

My first reaction was, ASTONISHMENT, I kept saying to myself, "this can't be happening!", my room DISAPPEARED!. I first described it to Denis that it's like hearing my speakers in an unechoic room, it was an incredible experience. Later, Denis put it using better words, it's like the sound you get with headphones, only without the imaging being inside your brain (this is so true!!!). I have to warn you though, this stuff is addicting!, I've decided to bring all the songs which sounds less than decent in my room (especially those with heavy bass, like Marcus Miller), and was again, astounded. I actually prefered listening to the corrected signal, with those songs, even WITH the compressed high frquency response that I am getting. I still can't get over this experience. Some people often describe that after some changes they did in their system, it sounds like a veil had been removed from the speakers, well, in this case, it's like the room has been removed from the speakers!. I keep looking at the speakers, then at the room, then again at the speakers, then again at the walls, and just can't get over the experience that there is no apparent interaction between the two, the illusion is THAT good! (at least in my room, and your milage WILL vary, for better or worse, since no two rooms are the same).

I did notice a couple of things, like this process tax your amp to a certain degree (really depends on your room, I guess), but I have a 150WX2 amp, so this wasn't a big issue. Also, you really need to be in the listening spot, if you'll go too far, things start to sound funny.

Last but not least, Denis told me that sub calibration is not a problem, all I need is to let it work during both MLS recordings (for each speaker), and that DRC will do the rest. I can't wait to try it out tomorrow, using a 40hz cut off for the sub, and letting the mains go "large".

I'm going to buy a better mike next week, and if the higher frequencies problems are going to go away, I think we'll just have our first, truly "killer app" for the HTPC's audio domain. I can't thank Denis enough for all his hard work.

If you're going to try DRC for yourself, be patient, there are some bugs in the process that you might encounter (not with the DRC code itself, which doesn't have a graphical interface, yet, but more with the initial and final process).

I'm waiting until my mike is going to arrive next week, and once it will, if it will solve the problems I've mentioned (meaning, it get's my "audiophile approval", for what it's worth), I'm going to write a complete, step by step, updated guide (there is already one completely outdated guide), which is going to make things very easy for anyone who'll want to take advantage of this amazing tool. That's the least I could do for Denis.

Esben, the correction can only be done on the entire 20hz-20khz region. The correction will always be softer on the higher frequencies, and stronger on the lower frequencies, plus, you can set it manually to perform a much softer correction on the higher frequencies, but you won't be able to make it run only for the 20hz-200hz, for example. At least not with the current version. Believe me, if you mainly listen from your listening spot, and a good mic really solve the higher frequncies tonality, you'll have no problem going with a strong correction, all over the spectrum.

Reading my post again, I want to make sure one thing is clear:
The discussion in this forum raises a lot of possible ways to improve our listening quality. We try better cables, different sound cards, different output types (Kernel/Asio vs Kmixer's SRC), different software players etc. But, up to this point, even though I DO notice and appreciate some of the benefits gained from all the tweaks I've mentioed, the only time in my life I've experienced a real HUGE improvement in sound quality, was when I switched my several hunderds $ speakers, to a several thousands $ pair, this was the only time I experienced a trully dramatic change in sound quality, for the better. Until today.

Just wanted to clear that one. Again, it could be that my room has overly problematic acoustics (I didn't go and measure many other rooms, so I can't really compare), so you do understand that my results are highly dependant on that factor. But I'm sure some of you have worse rooms than mine, so I'm sure at least those guys are going to agree with every word I've written here today.

It's a good thing that DRC is a freeware, otherwise, some people would have surely made everything in their power to get me banned immediately, after this post, for marketing reasons.
post #23 of 570
Originally posted by Yoniza
Well, I had to dig pretty dip to get to this thread again, so I'm not sure if anyone is still reading it.
Well I have this thread saved in Excel and book marked. Stuff has been dug up a lot deeper than yours, so I wouldn't worry.

That is great and encouraging news! :D I do have a Fibonacchi ratio room speaker placement in a rectangular 13'x23' room - room cancellation is done very well through the "room nodes" and reflections naturally. Here's 1 link - http://www.audiolinks.nl/speakersetup.htm

I got a flame once from a Tact fan and their DRC (at audioreview), but it didn’t reach my ceramic encased underground bomb shelter (no flamesuit necessary) and they (or him) deleted his post anyway. But I am a big fan of Tact anyway. :)

PS - interesting comment about headphones, I'm a big headphone/2.1-channel fan... I do like 6-8 channels, maybe eventually....
post #24 of 570
post #25 of 570
Great post, I have been using Shibach's Super EQ and been looking for something superior also. I am using it for mobile audio correction were the "room" acoustics are far worse than the worst home room Some questions about Denis's DRC software. Does it work on more than two channels? I would like to use it with a 5.1 setup. I can live without this because good stereo is far better than bad surround. The other issue is horsepower. I am using a VIA M1000 computer for space reasons. Right now it can handle the Shibach's plugin, and SRS Circle sound II 5.1 simultaneously.
Do you think it could handle 2 channel DRC?
Looking forward to your guide
post #26 of 570
Thread Starter 
Does it work on more than two channels?
Not currently, but be assured that it's going to change in the near future.

I am using a VIA M1000 computer for space reasons. Right now it can handle the Shibach's plugin, and SRS Circle sound II 5.1 simultaneously.
Do you think it could handle 2 channel DRC?
Here, make a test, download the RealReverb plugin for Winamp from this webpage, then run it using this (direct download, press right mouse key, then "save as") convolution file. If things plays out smoothly (meaning, just without dropped samples, don't expect it to sound good, it will sound awful, since it is calibrated for someone else's room acoustics, plus, it uses an older version of DRC, which didn't have some important features, but this shouldn't affect the authenticity of the test) you are fine. Be sure to use directsound as your output in Winamp, since it won't work with KS/Asio (though those who'll want to take advantage of bit accurate output, will be able to make the convolve process off line with the .wav file of their choice, and in this case, it doesn't matter if you're on pentium 100, I guess).
post #27 of 570
RealReverb uses only uses about 30% CPU on my anemic M1000 processor.
Time to get a calibrated mic. Does RealReverb have a version that is not adware?
PS Your room must be really screwed up. That file sounds weird on just a pair of old soundworks
post #28 of 570
Thread Starter 
Time to get a calibrated mic.
The current bang for the buck, unless you want to go DIY, is the Behringer ECM8000 (about $40. It's lower than what I paid for my Rat Shack, but you'll also need to buy a separate phantom power supply, which is another $40). I think it will be best if you can get it from a place which you'll be able to bring it back for a refund, if things won't sound good to you from any reason. It just that I have not yet heard DRC like it should be heard with a good mike, and even though the potential is there, it still doesn't have my "audiophile seal of approval", again, for what its worth. This will have to wait for next week. After a positive test with a good mike, I'll be much more comfortable recommending DRC to other people, especially to those who actually need to spend money in order to get the mike+power supply hardware to enjoy it (and won't be able to get a refund).

Does RealReverb have a version that is not adware?
Not sure, anyway, why pay when you can get it for free ?.

PS Your room must be really screwed up. That file sounds weird on just a pair of old soundworks
It's not my room, but I'm sure you'll get screwy results with my room's convolution filter also. That's just the way it is when you're correcting for the full 20hz-20khz region, at relatively small rooms.
post #29 of 570

I'm eagerly awaiting your step by step guide....
post #30 of 570
Good advice on the mic. You really should get a mic preamp instead of the phantom supply. The mic inputs on most sound cards (including the revo) are not very good. Two good choices are the Beringer SHARK DSP110
(one channel) and the M-Audio Audio Buddy (two channel) These will run you around 69.95 and 79.95 respectively.
Why not use the Adware version? It takes up the entire screen at 800x480.
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