Here is how I made the latest correction to my room, Measurement was done like in the guide except I used one measurement for both channels (mono), which I prefer in my symmetrical room.
Uncorrected, not very pretty in my small concrete room despite lots of acoustical treatment:
Here are the filters, I kept Q at or below 5 and only corrected lower frequencies:
The house curve I used is similar to the default one i Dirac:
20 6
100 2
550 0
5000 -1
10000 -2
17000 -3
18000 -5
19000 -10
20000 -20
As you can see, the corrected frequency isnāt completely flat. I left 2 dips untouched (the one at 150Hz is caused by reflection from back wall), and I also allow some small ups and downs. Basically I only correct in ābroad strokesā, and stay away from higher frequencies. It donāt look to good, but it sounds better than full auto-correction, at least in with my system in my room.
I then exported the measurement and filters from REW, and imported them into rePhase to get more control of how to generate the convolution file. Then I generated one minimum-phase and one linear-phase convolution file, and selects the one that sounds best. You are free to experiment with phase corrections here, for example make linear phase for higher frequencies, but for now I prefer minimum phase.
Well done Magnus! Phase corrections below 500Hz are not really needed in my experience, hard to hear and risk of audible preringing, unless you have a major alignment issue between speakers which is unlikely. They are appreciable nevertheless until 3kHz especially if they can compensate tweeter/mid alignement issues, mechanical or due to filters.
There is ONE case very often completely forgotten where phase correction is needed in the bass and actually the whole spectrum : extreme EQ which is different between left and right speakers, generating phase differences between channels. Make sure phase difference between left correction and right correction is below 15 degrees all over the spectrum. Very easy to check with REW: drag and drop correction files in REW, Overlay / Phase.
Of course in your case Magnus thereās no risk as you apply the same correction on both L and R.
I did an experiment, full range correction and then I gradually went from minimum-phase to linear-phase by leaving below 100Hz untouched, then gradually higher phase correction up to around 1khz and then linear phase from there. Sounds good, but as expected the differences are subtle. It does feels like a good way to do it so I will use it for now.
This guide was super helpful, thanks for this @Magnus, the sound quality difference is substantial, Iām quite surprised! Do you have any tips on how to do this with a subwoofer? Iād love to correct that as well, if only to satisfy my OCD that I did my best
Its possible to measure and construct a good crossover, for example in REW + rePhase, and fix/align phase and so on. But thatās more about integration of a sub-woofer with satellites and not digital room correction.
For digital room correction, at least when it comes to frequency corrections, measure with everything in place from listening position is the way to go. You want to measure and correct what reaches your ear after all.
I think Dirac has some special bass-handling in their new software, but havenāt tried it myself.
One last (potentially) silly question, I still want to use the Speaker Setup filter right? I currently only use that for distance, but do the REW filters take that into account and I can drop it?
For Mac users trying to run Dirac the Audio Hijack thing works but is kind of a pain. If basically makes a perpetual recording of your Dirac corrected audio. So itās another app that consumes resources, gets updates, hangs and crashes here and there. It isa very capable app, but it is not an elegant solution to Diracās lack of connection to Roon to say the least. But Dirac itself is still WAY easier to use than REW on the measurement and filter generation side.
I ran Dirac that way for at least a year. Dirac struggled to update the standalone product for years - keeping track of all the delays and betas was mind numbing. Anyone who has followed Dirac over the years knows what Iām talking about. I finally gave up on the virtual cable thing and the perpetual betas and switched over to the NAD M10 and C658 that can handle running the Dirac filters themselves. So much easier. Strongly recommended.
Apparently Dirac recently made some press releases leading some to believe that Dirac Live could now be somehow compatible with Roon. I havenāt seen any language to that effect myself - and as far as I know the Dirac processor still needs to be on the same machine that the audio is being output from.
Dirac has also said it plans to release a Bass Control module very soon that can reportedly do some very interesting things with multi subwoofer setups. But in fairness, DIrac has been talking about this software for about a year I think under different names - and I still have no idea of what hardware it will actually be compatible with when it becomes available. They initially claimed it would run on the M10 and C658 but there is talk on other forums now that this is NOT the case.
I hate to speak out of turn about the company - because Dirac Live truly is an amazing product - but they just seem to over promise and underdeliver time after time. Perhaps things are changing there for the better.
I did see this document. It says how to use a very promising product. My question is - with what equipment will this actually work, and when will it actually be available.
I see a reference to Storm Audio somewhere. No offense but I have been interested in AV for a long time, and am fairly certain I have never seen or even heard of Storm Audio until this point. Iām sure itās great stuff - but what about Arcam, and NAD and some of the other partners here. What is this intended to work with?
Thank you Magnus for the very good walkthrough about room correction with REW, without this I was not able to handle or understand this complex software!
I read all 694 posts to this topic the last days now - not an easy job for a non-native English speakerā¦
I performed some measurements and correction filters up to now and the result gave me a better bass control to my 2.1 system. Although the differences are very small, maybe my room or my config was close to the optimum already. Accidentally.
Iām still struggling with some huge dips in the low frequencies around 50-100hz. Strange thing here: these dips can only be measured with the left channel. Iāll give it a try with a new measurement this evening.
One question: according to the document about Dirac Bass Control, Iām thinking about the crossover frequency and the gain of my subwoofer, which both can be set at the subwoofer itself. Wouldnāt it make sense to put the crossover frequency to highest setting, only adjust the gain to the gain of the main speakers and let REW or Dirac do the rest?
I experimented with that when I had a sub, but as often it depends. For example, most subs are slower and less distinct than mains speaker, so if you give the sub extra work bass could become less distinct. On the other hand, its good to let the main speakers focus on higher levels.
At the end I settled on a little higher level on the sub with a slight crossover overlap, and let room correction handle the rest. But thatās not necessarily best for you, so experiment and select what sounds best.
About bass dips: you can try correct them, but it will likely not sound good to correct the steep and deep ones. The real fix is about improving room acoustics (bass traps etc), but donāt do the mistake I did and think that a couple of Auralex LENRD will be enough, you will probably need much more.
I solved my bass problems DIY: bought a couple of wardrobes without a door on IKEA, filled them with stone wool and then double layer of cloth in-front. Almost 2 cubic meters of stone wool in a 4x4 meter room
This is my actual SPL, you think the dip is a room mode?
Also Iām a little bit nervous about the falling curve behind 10kHz - this is a pair of B&W 805 D3, shouldnāt they be much better in the higher frequenzies?
