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Feb. 2018
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Room Equalisation Wizard (REW) equalization experiences sought

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  • Room Equalisation Wizard (REW) equalization experiences sought

    My previous desktop system (computer, Behringer U control DAC, Tangent AMP50 amplifier, LS3/5a speakers) suffered from an exaggerated bass when I had the speakers on my desk. So I raised them a bit, using low Isoacoustic desktop stands, to bring the tweeter up to ear level. There was rather less bass boom, and with the help of the tone control on the amplifier I could reduce the last vestiges to quite acceptable levels.

    I have now replaced this system, with an ODAC DAC, an Emotiva Control Freak volume control, into a refurbished Quad 405-2, driving a pair of Harbeth P3ESRs. The sound is much better, of course, if only because the Harbeths lack the LS3/5a bass hump. Even so, when I used the Harbeth spoken word sample recording in the BBC anechoic room there was clearly still some bass colouration. As before, the cause must be the proximity of the large desk surface. And as before, I cannot raise the speakers any further because I also need to have the tweeters at ear level. This time, however, I no longer have an amplifier with tone control.

    So it occurred to me that I might use REW (Room Equalization Wizard) software to equalize the output, both to compensate for the proximity of the desk, and also for other in-room response issues (taking inspiration from the DSpeaker Antimode 8033 equalizing the subwoofer in my main system). Since streamed audio from the computer is the only source, I do not need to worry about equalizing other sources.

    I wondered if others have experimented with REW as well, in basic computer audio systems such as this one. I know Alan planned to delve into room eq for the Bristol show, but apparently he did not get round to investigating it. Or did he? Personally I have not progressed much as of now, since I cannot get REW to install on my Windows 10 desktop. I need to wait for my wife, who is the domestic computer wizard.

  • #2
    REW installation difficulties and Equalizer APO

    I am still struggling to install REW (I get an error message that the Java runtime environment is corrupted, even after re-insttalling Java), but in the meantime I discovered that REW measures, but does not have a proper equalizer built in (is that right?). So I looked for one, and found Equalizer APO: https://sourceforge.net/projects/equalizerapo/ It is a neat software equalizer with many options, one of them is that you can import equalization curves from REW.

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    • #3
      A better room eq system?

      I tried AS's recommended free room analyser and the result was ... disappointing. I could clearly hear a few dips and peaks in the frequency scan without looking at the plot. I would like to put some of down to the internal microphone of my laptop.

      The DSPeaker X4 would be nice. The one site in Finland that has pre-listed it just bumped up the price from 3,500 to 3,800.

      I don't have an issue with limiting myself to a 24/96 machine. I have half a dozen 24/192 downloads and I can downsample them, or indeed run them from a separate output bypassing a digital DSP unit.

      The options are a Dual Mode. I recall AS saying he had mixed results and I think it is preferred to work with a full range speaker system.

      Has anyone tried the Behringer DEQ2496? I can pick one up locally from StudioSpares for 230 + mic/stand and even if I hate it will get most back on eBay as they are very popular.

      Seems a sensible punt, even though it will require me to read a manual and press lots of buttons, something I am generally disinclined to do.

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      • #4
        REW with mini DSP 2x4

        Originally posted by ssfas View Post
        I tried AS's recommended free room analyser and the result was ... disappointing. I could clearly hear a few dips and peaks in the frequency scan without looking at the plot. I would like to put some of down to the internal microphone of my laptop.

        The DSPeaker X4 would be nice. The one site in Finland that has pre-listed it just bumped up the price from 3,500 to 3,800.

        I don't have an issue with limiting myself to a 24/96 machine. I have half a dozen 24/192 downloads and I can downsample them, or indeed run them from a separate output bypassing a digital DSP unit.

        The options are a Dual Mode. I recall AS saying he had mixed results and I think it is preferred to work with a full range speaker system.

        Has anyone tried the Behringer DEQ2496? I can pick one up locally from StudioSpares for 230 + mic/stand and even if I hate it will get most back on eBay as they are very popular.

        Seems a sensible punt, even though it will require me to read a manual and press lots of buttons, something I am generally disinclined to do.
        I have used REW and a purchased program called ARTA to both design loudspeakers and equalize rooms. Without spending a lot of time describing it I will just say that the speakers I design using these programs perform far better than they would have using traditional analog crosssovers and equalizers. I have been designing speakers since 1974 and have designed about 31 distinct systems.

        These programs and the mini DSP make the hard easy and make the impossible manageable. They do require a LOT of time and thought to learn both the process and make the necessary adjustments. The automated mode of REW generates correction filters and downloads them to the signal processor makes some improvements but can not achieve the degree of precision that a human can. I typically let it generate the correction filters and then tweak them interactively for the best results. I use the software and calibrated miss to measure and then listen to confirm. I generally EQ mostly the below 200-300 Hz but do general trend adjustments over the whole frequency range. About1/2 of my time is spent measuring and 1/2 listening.
        In my opinion each has it's place. The measurements can over a period of a couple of years calibrate you ear/ brain so you hear like you analyze.

        This process is definenly not for everyone, you have to like the technical aspects at least as much as the music for this to be workable.

        The Beringer units sound harsh to me. The mini DSP units, even though they are cheaper, sound better...
        I have a buddy that has the DSPeaker dual core? We replaced it with a minDSP2x4 which is cheaper and more versatile.

        BTW though it may sound like it, I have absolutely no link to mini DSP. I just like their units.

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        • #5
          I can concur that the MiniDSP is a neat little unit. At present I am using it as an active crossover feeding a pair of Quad 306 amps but it can do so much more.

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          • #6
            I can now report some of my own experiences, using it on my desktop system (computer as a source, ODAC usb dac, Emotiva Control Freak volume control, Quad 405-2 and Harbeth P3ESR speakers).

            My suspicion was that the proximity of the desk was responsible for a few bass peaks and a bit of boom. I used REW (with the microphone of my Antimode 8033 and its MicAmp II interface). With the help of a few YouTube videos I worked out how to do the measurement (you have to set preferences first, including downloading the microphone's calibration file, and turn off a few sound shaping settings like bass boost and high freq reduction).

            When you have the measurement you can see that there are indeed some peaks. Press equalization and you get an eq graph that you can export as text file if that is what your equalizer needs (mine does). I then used the combination of the Equalizer APO software and the Peace GUI interface for it to import the eq file.

            The Peace GUI has a button to turn eq on and off, so it is easy to compare. The slight equalization was enough to clean up the frequency range between 50-200 Hz (there is no point in equalizing above the Schroeder frequency of your room). The sound is really cleaner, allowing the little P3ESRs to shine even more. In a system with more sources than just a pc you will need a mini dsp to download the eq file to, of course.

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            • #7
              OK, so it seems that the miniDSP system here has great potential as a pass-through, in-line system which could take our source audio and adapt it to compensate for the reality of the listening room. Somewhere, buried in the stores, I have one of these systems I need to hunt for. The concept is this:
              Click image for larger version  Name:	minidsp.jpg Views:	3 Size:	55.0 KB ID:	75551


              The marked yellow gear is the miniDPS box.

              Now, the issue is how to get measurements of the listening room into miniDSP so that it knows what correction should be applied to the audio signal passing through it, to cancel the worst of the nature of the room. REW software, mentioned above, is quite a beast of a program. However, I've chanced upon an alternative: OmniMic, here.

              I know the author/designer of OmniMic and he is a first class audio enginner, and I've used his older measurements systems for a quarter centure, so I have total confidence in his work. Amazingly, OmniMic can measure the sonic characteristics of the listening room and can then output data that miniDSP can read directly to apply the necessary room-correction curves! Couldn't be easier.

              So, I'm going to explore the combo of Omnimic + miniDSP .....
              Alan A. Shaw
              Designer, owner
              Harbeth Audio UK

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              • #8
                In a show setting, would you conduct the equalization measurements with the seats totally empty, fully occupied or somewhere in between?
                Likewise, would you position the mic only at one ideal seat or take the average from multiple locations?

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                • #9
                  Originally posted by IMF+TDL View Post
                  In a show setting, would you conduct the equalization measurements with the seats totally empty, fully occupied or somewhere in between?
                  Likewise, would you position the mic only at one ideal seat or take the average from multiple locations?
                  Perfectly valid questions, and already covered by the manufacturer, here.

                  Alan A. Shaw
                  Designer, owner
                  Harbeth Audio UK

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                  • #10
                    As someone who has employed DSP for years now: a word of caution to all using DSP as means of 'room' correction.

                    First of all it's important to understand how we humans perceive sound in normal, reflective rooms with boundaries. While equalizing a loudspeaker to achieve a nice flat measured sound response in the listening position sounds appealing (no pun intended), it's important to understand that what we measure is not necessarily what we perceive. A measurement microphone + software does not equal a pair of ears and a brain.

                    Above the so called Schroeder frequency of the room (in many cases between 200 and 400hz) the direct sound of a loudspeaker is largely responsible for what we perceive as the overall timbre. Since loudspeakers generate sound in all directions, and we tend to listen in rooms (with boundaries) we also perceive the reflected sound (the sound that arrives later and has been bouncing off the walls, and furniture, some of it will have been absorbed by the time it reaches us). Well designed loudspeakers produce a sound that is nice and flat on-axis, with a well behaved off-axis behaviour (remember those reflected sounds?). I believe this is also in the BBC designer notes.


                    A measurement microphone and software will measure the sum of of both the direct and reflected sound, and while it seems tempting and logical even to smooth out the response - one must be aware that by doing so above that 200-300-400hz limit, we are also changing the direct sound of the loudspeaker. You know, that nice flat -anechoic- response designers go great lengths over to achieve. The result, more often than not, is an artificial sound that somehow measures right, but doesn't quite sound right. Further more, we're doing this for a fixed point in a 3 dimensional room (or perhaps an average of several adjacent spots). Meaning once you move from that little area, you'll have messed up the sound for the rest of the environment.


                    So in short - use measurements for loudspeaker placement purposes, bass management (where we're not that critical in terms of direct/indirect sound) for a nice balance in your preferred spot, and if nothing else works - look for some acoustic treatments.. Or move a bit closer towards the loudspeakers to get plenty of that direct sound. But please, don't mess up that balance, that a designer will have worked hard on to establish.


                    /rant

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                    • #11
                      I absolutely agree that room eq should be limited to the frequencies below the Schroeder frequency. In theory you could also equalize higher frequencies, but not on the basis of in-room measurements, but only from free field measurements. In that case you are equalizing the speaker's own response, and not the room. But it does mean you are sitting in the speaker designer's chair.

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