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For what it's worth, some SynRTA plots

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  • derek_rumble
    Robert, you ve asked for more in-room measurements in the past. here s mine using SynRTA and a Behringer ECM8000 microphone. Yes, I know there are better
    Message 1 of 22 , May 12, 2014
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      Robert, you've asked for more in-room measurements in the past.  here's mine using SynRTA and a Behringer ECM8000 microphone.  Yes, I know there are better mics out there but I'm not paying for one so no-one advise me to get a properly calibrated professional model OK?  ;-).

      I have a stubborn and strong 40Hz room resonance..  but this really does not sound as bad as it looks.  I did forget to load the microphone calibration file but this would not have altered things much at all; would have addressed the top end droop mostly.

      Thanks,

      Derek


    • Tom Mallin
      The Behringer microphone did not come with a calibration file when I bought one a couple of years ago. Is this a generic calibration, or individualized to the
      Message 2 of 22 , May 12, 2014
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        The Behringer microphone did not come with a calibration file when I bought one a couple of years ago.  Is this a generic calibration, or individualized to the particular serial number of the mike?  

        As I recall, adjusting the DEQ2496 for flat response with the uncalibrated Behringer resulted in very bright sounding highs when I adjusted the unit for flat response per the Behringer's measuring screen.  I switched to my calibrated LinearX and got much better subjective results even without using the calibration file and using just the Behringer's screen, not SynRTA.

        Derek's use of SynRTA gets around the fact that the Behringer DEQ2496 will not accept a microphone calibration file directly--at least not as far as I could figure out.  It also gives you much better resolution as to what you are doing, EQ-wise.

        On May 12, 2014, at 7:42 AM, "derekrumble@... [regsaudioforum]" <regsaudioforum@yahoogroups.com> wrote:

         

        Robert, you've asked for more in-room measurements in the past.  here's mine using SynRTA and a Behringer ECM8000 microphone.  Yes, I know there are better mics out there but I'm not paying for one so no-one advise me to get a properly calibrated professional model OK?  ;-).

        I have a stubborn and strong 40Hz room resonance..  but this really does not sound as bad as it looks.  I did forget to load the microphone calibration file but this would not have altered things much at all; would have addressed the top end droop mostly.

        Thanks,

        Derek


      • derek_rumble
        Hi Tom, I used the generic Behringer-supplied file from:
        Message 3 of 22 , May 12, 2014
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          Hi Tom,

          I used the generic Behringer-supplied file from:

          http://music-group.force.com/PKB/articles/en_US/FAQ/ECM8000-Calibration-List/?q=ecm+calibration&l=en_US&fs=Search&pn=1

          Seems to provide good results sound-wise.

          Derek
        • regtas43
          I am indeed interested in in room measurements. Thank you. But is the scale on the left real? That is, is one division really 10 dB ? If so, can the scale be
          Message 4 of 22 , May 12, 2014
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            I am indeed interested in in room measurements. Thank you.

            But is the scale on the left real? That is, is one division really 10 dB ?

            If so, can the scale be changed? Unless I am mis-reading, this

            is so squahed vertically that one finds it hard to tell much.

            For instance, if 10 dB is really one small space between dotted lines,

            then there is a considerable imbalance between the 100-300 Hz region and

            the mids/upper mids. Something like 5-7 dB.

            Can you show the measurements on a scale where 5 dB looks like a lot?

            On a 10 dB = one small vertical space, almost everything looks quite flat!

            Thanks

            REG

            PS If the screen won't do this, I can fix it myself with a photo program.

            But I have  a busy day today so I cannot get to this until tomorrow.

          • Tom Mallin
            The SynRTA vertical scale setting is just a matter of selecting a resolution. Looking at the dots in the Vertical Range circles near the top of the graphs, on
            Message 5 of 22 , May 12, 2014
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              The SynRTA vertical scale setting is just a matter of selecting a resolution.  Looking at the dots in the Vertical Range circles near the top of the graphs, on the posted graphs the 100 or 200 dB Vertical Ranges are used, which do give quite a quite compressed view of the response; each small division is 5 dB on the 100 dB window and 10 dB on the 200 dB window.  

              I usually use the 50 dB choice in my posted graphs, which makes each small division 2 dB.  Only if I really want to set a level, such as getting the 1 kHz level exactly at the 0 dB marker, do I expand the scale to the 20 dB level where each small vertical division is 0.5 dB.  The choice of Vertical Range makes all the difference in how flat the response appears.  You can hide huge sins with the 200 dB Vertical Range.

              Derek DID acknowledge and explain the reason for the currently compressed scale in other posts over on The Crooked Path.


              On Mon, May 12, 2014 at 11:03 AM, regtas43@... [regsaudioforum] <regsaudioforum@yahoogroups.com> wrote:
               

              I am indeed interested in in room measurements. Thank you.

              But is the scale on the left real? That is, is one division really 10 dB ?

              If so, can the scale be changed? Unless I am mis-reading, this

              is so squahed vertically that one finds it hard to tell much.

              For instance, if 10 dB is really one small space between dotted lines,

              then there is a considerable imbalance between the 100-300 Hz region and

              the mids/upper mids. Something like 5-7 dB.

              Can you show the measurements on a scale where 5 dB looks like a lot?

              On a 10 dB = one small vertical space, almost everything looks quite flat!

              Thanks

              REG

              PS If the screen won't do this, I can fix it myself with a photo program.

              But I have  a busy day today so I cannot get to this until tomorrow.


            • regtas43
              OK so I took a few minutes and fixed it--by photogrphing my computer screen and stretching the photo vertically. With sensible vertical scale, one can see
              Message 6 of 22 , May 12, 2014
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                OK so I took a few minutes and fixed it--by photogrphing my computer screen and stretching the photo vertically. With  sensible vertical scale, one can see that for example there is way too much energy between 1 and 2 kHz, a rather nasty dip between 100 and 200 Hz and a need to pull down 7-8 k and thereabouts. Time to get in there with that Behringer and fix things.

                The improvement that could be instituted here by suitable EQ will be amazing in sonic terms.

                REG

              • derek_rumble
                Yes i can post again with an expanded scale, tomorrow.
                Message 7 of 22 , May 12, 2014
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                  Yes i can post again with an expanded scale, tomorrow.
                • derek_rumble
                  Thanks for your comments Robert. I ll pay attention to these regions next time I set up the kit. SynRTA doesn t settle enough to make an arbitrary screenshot
                  Message 8 of 22 , May 12, 2014
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                    Thanks for your comments Robert. I'll pay attention to these regions next time I set up the kit. SynRTA doesn't 'settle' enough to make an arbitrary screenshot representative of a measurement session. The peaks and troughs move all over the place. 

                    Derek
                  • regtas43
                    They are bound to do this! (jump around) if there is no averaging over time. Pink noise is statistically uniform energy (per octave,or over any frequncy
                    Message 9 of 22 , May 12, 2014
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                      They are bound to do this! (jump around) if there is no averaging over time.  Pink noise is statistically uniform energy (per octave,or over any frequncy ration interval,  as opposed to white where the energy is uniform per Hz interval--not interval in the ratio sense --2 to 1 for an octave--but interval in energy between x Hz and x+a Hz, where a is fixed)  But these are averages over time! in both cases.
                      To get a stable RTA measurement  you need an averaging function, averaging over time. . I would be  surprised if this were not available on the computer program you are using.  Look around where it offers the option(as it really ought to do) of averaging a certain number of sampled measurements. (I do not use this particular program but most programs offer this option)/
                      This is a lot easier to interpret!  if the graph  is averaged over time. Otherwise the fluctuating signal itself makes the  graph jump around. Hard to make sense of it!

                      REG
                    • Tom Mallin
                      Derek, if the SynRTA is not settling, something is wrong with the way you have the program set up. Above the bass area there should be no visible shifting of
                      Message 10 of 22 , May 12, 2014
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                        Derek, if the SynRTA is not settling, something is wrong with the way you have the program set up.  Above the bass area there should be no visible shifting of curves at all.  Even in the lowest bass the reading should not be shifting around by more than plus or minus 0.5 dB.  The solid read-out and definite settling is one of the strong points of SynRTA.

                        Here are some things that could be wrong:

                        1.  You are using the Behringer's pink noise as a test signal rather than SynRTA's own noise.  There is a difference.  The SynRTA noise is not really pink noise.  You should not use ANY test signal other than the one generated by SynRTA with the SynRTA program.   

                        2.  You are using the wrong bandwidth of SynRTA's test signal for 1/6-octave measurements.  SynRTA provides different test signals for 1/6, 1/12, 1/24, and 1/48 octave measurements.  The noise must match the bandwidth for the graph to properly settle.

                        3.  You may have the anti-stuttering of the SynRTA program disabled.  That will cause the graph to jump around more.

                        4.  Also check that you are choosing the proper sound card for the measurements.  There will usually be a choice of the computer's own sound card (could be poor) or some external sound card added for audio measurements (I use an M-Audio Transit, one of those recommended by Liberty for use with SynRTA and Praxis).  It's best to record a CD with the SynRTA test signal with a duration of at least 15 minutes using the record functionality of SynRTA.  Otherwise, if you let the computer generate the SynRTA signal (which the SynRTA program also allows), you risk inaccurate measurement since the output of the signal may (unless you are careful) be output to your audio system via the computer's own sound card, which usually is not as good as a purpose-added audio measurement sound card.

                        5.  Make sure your SynRTA test signal level is high enough.  Adjust the SPL through the speakers so that it is just low enough to avoid seeing  the occasional clipping indication.

                        6.  Make sure you are only playing the test signal through one channel at a time.  Playing sound through both channels at once could cause jumping of the graph and will also falsify the readings for any frequency above the midrange.   


                        On Mon, May 12, 2014 at 4:00 PM, derekrumble@... [regsaudioforum] <regsaudioforum@yahoogroups.com> wrote:
                         

                        Thanks for your comments Robert. I'll pay attention to these regions next time I set up the kit. SynRTA doesn't 'settle' enough to make an arbitrary screenshot representative of a measurement session. The peaks and troughs move all over the place. 


                        Derek


                      • Edward Mast
                        Did I ask on this forum if anyone knows a comparable program to SynRTA that will operate on Mac computers? Ned
                        Message 11 of 22 , May 12, 2014
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                          Did I ask on this forum if anyone knows a comparable program to SynRTA that will operate on Mac computers?
                          Ned
                        • Ted Rook
                          Ned this is one program for macs, FuzzMeasure (silly name for a precision tool, don t be put off!) they have a free trial download, I am in winworld and have
                          Message 12 of 22 , May 12, 2014
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                            Ned this is one program for macs, FuzzMeasure (silly name for a precision tool, don't be put
                            off!) they have a free trial download, I am in winworld and have no experience with
                            Fuzzmeasure but it has stood the test of time at least having been around a lot of years.

                            http://supermegaultragroovy.com/products/FuzzMeasure/


                            Ted

                            On 12 May 2014 at 17:57, Edward Mast nedmast2@... [regsaudioforRe:
                            [regsaudioforum] For what it's worth, some Sy wrote:

                            > Did I ask on this forum if anyone knows a comparable program to
                            > SynRTA that will operate on Mac computers?
                            > Ned
                            >
                            >
                            >
                            > ------------------------------------
                            >
                            > Yahoo Groups Links
                            >
                            >
                            >
                          • Edward Mast
                            Thank you, Ted. I ll try it. Ned
                            Message 13 of 22 , May 12, 2014
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                              Thank you, Ted.  I'll try it.
                              Ned

                            • derek_rumble
                              Tom, Check. Yes to all your points. I am using the SynRTA special noise, correct choice of 6dB per octave and so on. I understand how to operate it. To REG,
                              Message 14 of 22 , May 13, 2014
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                                Tom,

                                Check. Yes to all your points. I am using the SynRTA special noise, correct choice of 6dB per octave and so on. I understand how to operate it.

                                To REG, SynRTA uses its own pseudo pink noise signal. It's pulsed in some way and I guess the program synchronises with the pulse.

                                Not bad for a free program, I just need to be more careful and patient next time.

                                Derek


                              • derek_rumble
                                P.S. Tom, I store 10 mins or so of the 6dB per octave signal in my hard-disc-based library, replayed through a Squeezebox Touch. I have files ready for L
                                Message 15 of 22 , May 13, 2014
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                                  P.S. Tom,

                                  I store 10 mins or so of the 6dB per octave signal in my hard-disc-based library, replayed through a Squeezebox Touch. I have files ready for L chanel only, R chanel only as well L + R.  Convenient this is.

                                  DR.
                                • derek_rumble
                                  I meant 1/6 octave in those previous posts of course, not 6dB per octoave; it s too early. Just about to upload a plot with 1dB divisons for the vertical
                                  Message 16 of 22 , May 13, 2014
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                                    I meant 1/6 octave in those previous posts of course, not 6dB per octoave; it's too early.

                                    Just about to upload a plot with 1dB divisons for the vertical scale.

                                    DR
                                  • derek_rumble
                                    Hi Robert, I think you have been looking at the wrong plot. The before and not the after ? And the before EQ ain t that bad if I may say so. The plot of
                                    Message 17 of 22 , May 13, 2014
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                                      Hi Robert,

                                      I think you have been looking at the wrong plot.  The 'before' and not the 'after'?  And the 'before' EQ ain't that bad if I may say so.

                                      The plot of post-EQ is named 'main + sub low res with and without 10dB rolldown' and this shows a flatter achieved response (albeit with a compressed vertical scale) as well as how it's looks with a down-tilt applied.  I have now uploaded a new plot showing the same post-EQ result, without the down-tilt and with 1 dB vertical increments.

                                      Should have labelled them more sensibly, sorry.  And apologies too for fragmenting this thread.

                                      Derek
                                    • pjdami
                                      Fascinating information here guys. Very useful and hands on . Would someone volunteer to post a how to paper with a summary of tips on how to properly
                                      Message 18 of 22 , May 13, 2014
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                                        Fascinating information here guys.  Very useful and 'hands on'.  Would someone volunteer to post a 'how to' paper with a summary of tips on how to properly obtain speaker FR measurements under the Files section of this group?  I think that would come in handy to prevent repeat questions here on the group and to set some generally accepted standards for consistency.  The search feature on the Yahoo group can be very tedious to track down conversations it seems and not the most user friendly.  I hope to do some FR sweeps with my LS3/6 and BC1s in the near future after I move into a new house.  Paul
                                      • Tom Mallin
                                        Here is a link to a discussion of SynRTA by me on another forum whose prior posts are somewhat easier to access:
                                        Message 19 of 22 , May 13, 2014
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                                          Here is a link to a discussion of SynRTA by me on another forum whose prior posts are somewhat easier to access:


                                          Besides that, the Help files for SynRTA are very helpful and tell you most everything you need to know.  Here is a link I just tested for getting a download of SynRTA from the Internet Archive Way-Back Machine.  The current link does not work (at least for me) since it is marked as malware by my computer's security.  The old link works and the program downloaded fine today:


                                          Once you install SynRTA, you can click on the Help button and access the how-to-use information.  For those who don't want to download the program, I've pasted in the key instructions below.  Hopefully the pictures will come through.  If not, I'll try putting this information in the Files section of the forum:

                                          About SynRTA

                                           

                                          Synchronous Real Time Analyzer


                                          SynRTA is a freeware soundcard-based audio frequency response analyzer designed for easy optimization of loudspeaker and listening room responses.  SynRTA makes response plots from 12Hz to 20,000Hz and at frequency resolutions of 1/6th, 1/12th, 1/24th, or 1/48th octave.  

                                           

                                          Like common "RTA" analyzers, SynRTA uses "Pink Noise"-like signals. To use it, play a signal through your system, pick up the sound with a microphone connected to your soundcard, and watch the response curve on your computer.  A nice thing about using noise is that you can just play it on a CD without having to wire a computer to your sound system.  A not-so-nice thing is that noise is ...noisy.  With an RTA, you usually have to wait enough time to average the response to see what it settles down to.

                                           

                                          SynRTA's operation is keyed and synchronized to specific test signals that sound like pink noise (but aren't really noise at all).  This lets SynRTA response graphs appear stable and very repeatable at each graph update . SynRTA response graphs don't need to "settle".  It makes finding the best position for speakers and adjusting equalizers simple and efficient.

                                           

                                          Notice that not just any pink noise will do!

                                           

                                          SynRTA should be used with the test signals that are keyed to the software.

                                           

                                          SynRTA can be used at a relatively coarse resolution (1/6th) for rapid screen updates.  Or at higher resolution (up to 1/48th octave) for when you want to see a lot of detail.

                                           

                                          Each measuring resolution SynRTA uses is keyed to a different special psuedo-noise .

                                           

                                          That's because the test signal must be "synchronous" with SynRTA's analysis at each resolution.

                                           

                                          Getting one of these special signals to play out of speakers is no problem--

                                            

                                          • You can just play a CD of the appropriate noise signal.
                                          • Or if you want, SynRTA can continually play the needed pseudo-noise signal.

                                           

                                          No, no one's going to try to sell you CDs of the special noise!  SynRTA can automatically generate WAV files, ready for burning to audio CDs using your computer and a CD burner.

                                           

                                          For most tests, playing a custom burned CD is an easy and convenient way to have your audio system play SynRTA's keyed pseudo-Noises.


                                          Why you need SynRTA

                                           

                                          If you've ever used an RTA and pink noise to try to measure your system, you know what a pain it can be.  Seeing the curve at the higher frequencies is pretty easy and reasonably fast, but the lows seem to take forever to settle down to a comprehensible shape. You probably ended up not wanting to try too many things with your system, life is just too short.

                                           

                                          Or if you've worked with a measuring setup using chirps, MLS, impulses, or tonebursts, each measurement is fast.  But in that case, timing is everything.  The microphone end needs to know exactly when and what the sound-playing end is doing.  The test signal isn't the same all the time, so you need to catch it just right.  And that usually means tying in the computer to the sound system, usually with long cables stretched across the room.  Then, you usually have to go through separate recording and processing operations, messing with the computer when you want to be trying things in your room or with your sound system.

                                           

                                          SynRTA is designed to be easy like an RTA and quick like a synchronous system.  And it's free.  What more do you want?

                                           

                                          A lot of audiophiles and home theater owners spend large amounts of cash on gear, in an attempt to improve sound quality.  Usually, though,  the placement of speakers, subwoofers, and listening chairs and the presence or absence of absorbtive materials will have far more effect on sound quality than will equipment purchases.  Often the room effects at low frequencies are so bad that just working with positions isn't enough.  If you use a parametric equalizer to help further tame low frequency room effects, SynRTA will allow you to watch and compensate for room effects and standing waves in near real time.


                                          Using SynRTA: requirements

                                           

                                          What you'll need:

                                           

                                          • SynRTA software (free via download from Liberty Instruments, Inc.).
                                          • A Windows (2000, XP, or VISTA)  computer equipped with a reasonably good soundcard and line-level inputs. The microphone input connector on most soundcards (including those built into laptop computers) isn't usually any good for measuring low bass response.  If you have to, buy or borrow an inexpensive USB soundcard.
                                          • A cable to play the computer soundcard through the audio system -- or -- a test CD burned from files generated by SynRTA.
                                          • A microphone with acceptable or known frequency response.  Microphones made from Panasonic WM-60 capsules or Radio Shack sound level meters can be used for most purposes. If the microphone's response is known, a calibration file can be used by SynRTA to correct for microphone variations
                                          • For many soundcards and microphones, an external microphone preamplifier may be needed.  

                                          Using SynRTA: equipment setup

                                           

                                           

                                          If you will be using a CD, connect like this.  See Making Pink Noise CDs to see how the CD files are made and burned to audio CD.  The CD, of course, is for playing through your sound system as usual.



                                          ​ 

                                          If  you'd rather (and it's convenient) instead connect from your computer soundcard to your sound system, then connect it like this:



                                          You need a cable and/or adaptors to connect from the stereo line output of the soundcard (usually a stereo 3.5mm jack) to the sound system's input (usually RCA type connectors).  

                                           

                                          For either setup, you need a way to connect a microphone to the soundcard's input section.  You will need to get appropriate adaptors and cables to connect the mic, preamp (or mixer) and soundcard.  The microphone should feed either just the Left channel of the input or Both channels.

                                           

                                          The computer could also be a laptop type, although in that case you will probably want to use an external USB-connected soundcard so that you'll have line inputs.  If you are not concerned with overall response flatness or very low frequencies, you can use a normal computer microphone connected directly to the mic input of the soundcard, but remember that usually soundcard microphone jacks have very limited bandwidth.

                                           

                                          Start with the sound system volume control set low.  When you start SynRTA or play the CD, you should hear a muted hissng that sounds like a huge electric fan. That's the pseudo-Pink Noise.  Turn it up, but not so much that it hurts or makes you want to run out or the room.

                                           

                                          If you are not using a CD, you may need to select the right Play soundcard in SynRTA or adjust the "Play" (output) mixer for the card.  Set the mixer so that the "WAV" line is NOT muted.


                                          Using SynRTA: operating the software

                                           

                                          When the SynRTA program starts, it comes up in 1/12th octave resolution mode, with pink noise coming out the soundcard's jacks.  If you're using a CD, just turn down the pink noise or uncheck the box labeled "enable" (F) near the top right of SynRTA's screen.  

                                           

                                          If the name of the soundcard you're using isn't shown below the "Input Mixer" (C) button, use the menu at the top of the screen to select "SoundCard" and a small form will pop up.  Use that to select your recording and/or playing soundcard names.  

                                           

                                          Click the "Input Mixer"(C) button and a mixer control may appear.    Some pro level soudcards don't have input Windows mixers, but most have a custom mixer or control panel , so you may need to use that to set input levels or to select the microphone input.  Set the mixers (C and D) so that the correct recording input source is selected, and that the record level is turned up adequately  Only the signal from your microphone should go into the sound card "record" function, and only "WAV" audio (or nothing, if using a CD) should come out of the soundcard "play" function.

                                           

                                          After the graph stops telling you to wait, click the "Center" button (P) and in a second or two, you should see a ripply line on the graph.  You can click this button any time the blue trace in the graph goes too high or too low to see on the graph

                                           

                                          If you have a calibration file for your microphone, you can load it from the "Microphones"(L) menu at the top of the screen.  See (L), below.

                                           

                                          There are some other features in the SynRTA program, if you want to go further or have other uses for the analyzer.  You can find out about these from the information below, which shows SynRTA's controls and what they do:



                                           

                                          • A: Sets the lowest frequency on the graph
                                          • B: Sets the highest frequency on the graph
                                          • C: Brings up the input (record function) Windows mixer of the selected input soundcard.
                                          • D: Brings up the output (play function) Windows mixer of the selected output soundcard.
                                          • E: Level meter for input.  Shows when a signal is being sensed.  Ideally you should adjust input preamp or mixer contols so that the green area is as large as possible without making a red "flash".
                                          • F: When checked, enables pink noise output from the output soundcard.  Button D and control G are only enabled when this is checked.  Uncheck this when using a CD to play the Pink Noise.
                                          • G: The output level control for the soundcard.  
                                          • H: The frequency response graph.  This can have one "active" curve and up to 20 "Hold" traces.  See explanation for N.  The graph will show gray with a message "wait" for a few seconds after changing soundcards or resolution.
                                          • I: Save menu.  You can save the present data as a comma-separated (csv) text file or as a bitmap (bmp) picture. Csv files can be loaded into spreadsheet programs such as Excel
                                          • J: Prints the graph to the system default printer.
                                          • K: Soundcard menu.  Use this to select the input and output soundcard devices that SynRTA is to use.  They don't need to be the same card.
                                          • L: Microphones menu.  Use to load a microphone reponse curve (for microphones with known response).  A microphone file is a list with frequency and relative response (in dB, decibels) listed on each line.  If you use this menu and then select "cancel" then no file will be used.  Files for typical Radio Shack SPL meter microphones are available (only the lower frequencies are calibrated) and others can be made.
                                          • M: Resolution Menu.  You can use this to select the resolution that SynRTA is to measure at. Use this also to generate special pink noise files for testing.  1/6th octave is the fastest in operation, 1/48th is the slowest (but most detailed).  For most room optimization work, 1/6th or 1/12th octave are recommended.  When using a CD to play the noise, make sure you play a noise file that was generated for the resolution you want to use.
                                          • N: Curve Hold menu item.  Every time you click this, the currently shown "active" curve is copied to a new "hold" curve shown on the same graph.  Each new curve will be drawn in a new color and listed in the legends box at the bottom.  (see R)
                                          • O: Clear Curves.  When you click this, all hold curves (and the legends) will be deleted.
                                          • P: Center Button.  This button will move the active curve up or down so that the point at the frequency selected will lie on the "0dB" line.
                                          • Q: When this is checked, the active curve will be modified to account for the curve thst was active when the Set button was last clicked.  For instance, after you click "Set" and check this box, the next update of the graph will show the difference (in dBs) of the actual active trace and the Reference curve -- if they are the same (i.e., nothing has changed), a straight line at 0dB will be shown, like the blue line in the graph above.  Use Reference to find only the difference between two curves, to see what has changed when you change things in your sound system.  Note: whenever Resolution is changed, the Reference curve will be cleared.
                                          • R: The Legends for the curves.  This will appear only when there is at least one Hold curve present.  To edit the text on each curve, or to delete an individual curve, click on the related colored line in this box.
                                          • S: The currently used Resolution and any Microphone calibration file in use are listed in this bar.
                                          • T: Use this control to select the "vertical scale" -- the number of dBs that are between the top and bottom of the graph.  Stretches or compacts the display of the curves.  When working with rooms, the 10dB to 50dB positions will usually be used.

                                           

                                          Special note!  The curves shown on the graph above are from measuring the soundcard itself, not with a microphone!



                                          Some suggestions for Room Optimization

                                           

                                          • Response variations of 20 to 30dB aren't unusual in unoptimized rooms.  It doesn't mean the sound system is broken, only badly arranged.
                                          • Optimize looking at one full-range speaker at a time. But for working with subs, have all the subs playing together (if you have more than one).  
                                          • Check the response at any listening seats that will get used.  Aim for optimizing speaker placement and room treatment for as broad a range of seats as possible, not just for the sweet seat.
                                          • Don't try to take out narrow response notches with an equalizer -- equalizing these will likely make things sound worse for most seating positions.  But taking out response peaks is ok.
                                          • Wide and deep notches at low frequency usually indicate bad placement of the listener or the subwoofer/main woofers.  You might want to also check for proper relative phase polarity between subwoofers and main speakers.  The correct polarity is the one that doesn't leave a big hole in the response near the crossover frequency!
                                          • Don't try to use too high a resolution (1/48th, for example) when optimizing.  Too much detail in the response graph can make things confusing and trends harder to see.
                                          • Multiple subwoofers (optimized together and in different places in the room) will probably get a more full bass response than using a single subwoofer.  Multiple subs are a lot better at getting a wide range of good sounding listening position.  If you are about to buy a sub, consider getting several less expensive ones rather than one fancy one.
                                          • The best places for subwoofers aren't usually up next to the main speakers -- try near the middle of the side walls.
                                          • Don't reject the idea of using equalizers just because you might want to be a purist.  A parametric equalizer on the subwoofer channel can make or break a system, and there is nothing pure about what rooms do to bass response!  (And sometimes purists listen to the lousyest sounding setups!).

                                           



                                          1/24th octave room plot: Red curve = a few feet off;  Blue (live) curve: better placement and mild EQ 


                                          Making Pink Noise CDs

                                           

                                          First, decide what resolution(s) you plan to use.  1/6th or 1/12th octave are usually the most helpful for rooms, so get those at least.  It is usually easiest to make separate CDs for each resolution that you will use.

                                           

                                          Use the Resolution menu of the main SynRTA form and the following form will appear:



                                          Select the desired resolution and the time length of each Pink Noise track (wav file) that you want to make.  Ten minutes (600 seconds) or so is a good length.  You can add multiple copies of the same file on each CD, if desired.  

                                           

                                          Then click on the "Make a Pink Noise File" button. You will be asked where to save the files.  Make sure it will be saved to a folder you are allowed to write to -- Vista can be very fussy about this -- your "My Documents" folder is probably the best choice.

                                           

                                           Although SynRTA measures operating at 48kHz, the wave files it can make are at 44.1kHz, which is what a CD wants.

                                           

                                           BE PATIENT -- GENERATING A NOISE FILE TAKES TIME.

                                           

                                          After the file is complete (the Resolution form will vanish and the analyzer will begin running again), you are ready to burn a CD.  Put a blank CD in your burner and start the burner program (such as Nero).

                                           

                                          Different burner programs are operated differently, but in general, the burning process goes something like this:

                                           

                                          • Select burning to a CD (rather than to a DVD).
                                          • Tell the program you will make an Audio CD (not a data CD)
                                          • Get to the part of the program where you tell it what files (songs) you want to burn.
                                          • Open the folder where you saved the WAV file you generated and drag it to the burning list area.  Drag it a number of times to fill the disk, if you want.
                                          • Burn the CD. 



                                          On Tue, May 13, 2014 at 7:06 AM, pjdami92@... [regsaudioforum] <regsaudioforum@yahoogroups.com> wrote:
                                           

                                          Fascinating information here guys.  Very useful and 'hands on'.  Would someone volunteer to post a 'how to' paper with a summary of tips on how to properly obtain speaker FR measurements under the Files section of this group?  I think that would come in handy to prevent repeat questions here on the group and to set some generally accepted standards for consistency.  The search feature on the Yahoo group can be very tedious to track down conversations it seems and not the most user friendly.  I hope to do some FR sweeps with my LS3/6 and BC1s in the near future after I move into a new house.  Paul


                                        • laurie483000
                                          Fascinating information here guys. Agreed. Regarding searching the Yahoo archives, before Neo came along, it was possible to search on a topic, key words /
                                          Message 20 of 22 , May 13, 2014
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                                            "Fascinating information here guys."

                                             

                                             

                                             

                                            Agreed.

                                             

                                            Regarding searching the Yahoo archives, before Neo came along, it was possible to search on a topic, key words / phrases and for message authors and this worked reasonably well, but does anyone know if this is still possible.  I only know how to search by typing in a message number (clicking on spy glass icon - Go to Message) or lists of messages month by month (under View - Message History).

                                             

                                            I see they're still playing around with the interface - in the last week or so the main menu choices have been changed to small icons rather than text headings, so maybe better search facilities will be restored sometime.

                                             

                                             

                                            Laurie

                                             

                                          • regtas43
                                            I shall try to write something at some point. But here is a quick summaary By far the easiest thing is to use time averaged 1/6th octave RTA first close to the
                                            Message 21 of 22 , May 13, 2014
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                                              I shall try to write something at some point.

                                              But here is a quick summaary

                                              By far the easiest thing is to use time averaged

                                              1/6th octave RTA first close to the speaker and then

                                              backing up. This is about the resolution of what

                                              one actually hears. If this is or is made smooth and nice

                                              then things will sound good usually.

                                              Micro structure measurements via sweeps or impulses

                                              are only useful if one checks for spatial stability(which

                                              in principle one ought to check for the RTA too--but that is easy.

                                              Just move the mike around a bit during the measurement).

                                              Fine structure that is not spatially stable is worse than meaningless --
                                              it is totally misleading-- and correcting it ought not to be done.

                                              If one is doing impulse or sweep measurements one need to time-window

                                              in the higher frequencies. Otherwise one gets garbage as far

                                              as connnection to what is heard is concerned.

                                              Even if one does time window one needs to spatially average.

                                               

                                              REG

                                              PS It is worth noting on REGONAUDIO that the effect of

                                              correcting with DSP correction is to give smooth RTA. Of course

                                              the correction typically corrects finer structure than that.

                                              But this is largely meaningless--if the system  is EQed relatively broadbnd

                                              to get the RTA right then the fine structure correction does

                                              little to the sound thereafter--except sometimes to make it worse.

                                              Over-correction of one point measurements is a real possibility.


                                               

                                               

                                            • regtas43
                                              The claim that the fine structure correction does rather little when the system has been broader band corrected to be right--on the 1/6th octave level of
                                              Message 22 of 22 , May 13, 2014
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                                                The claim that the fine structure correction does rather little when the system has been broader band corrected to be right--on the 1/6th octave level of resolutiion say--id not theory only--I have tried this over and over If one EQs by analogue means to get things balanced right and pretty smooth, micro structure correction does not do much--and it may even make things sound worse.

                                                This field is full of audiophile obsession. People who for decades have listened to systems with huge errors without worrying about them suddenly decide they have to EQ to flat with 1 Hz resolution or something. Never mind that what they are EQing to flat is the wrong thing!

                                                This is crazy.  EQ is vital--but this does not mean one needs to do it with microstructure that is spatially unstable. Remaining sensible seems to be hard for people in all directions

                                                REG

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