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Adjusting Room sound using material damping methods (not DSP)

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  • #61
    Re: Best way to demo the system?

    Originally posted by TNIC
    The listener often arrives with a somewhat numb ear that is not ready to pick out the details a good reproduction can offer (I sympathize and need to warm up my ear to someone else’s system to). Do you have any technique for sensitizing your listener’s ears (short of tying them into a chair for a long period of time)?
    Thanks in advance.
    I am a great believer in starting a listening session at a level that seems too soft at the time. I agree that our ears are numbed from the constant noise and when we listen to soft music, the ears seem to "open up", almost like your eyes dialate when going into a room with soft light. After a tune or two, I will nudge the volume up just a bit and the music sounds full and vibrant, but still at a lower volume than most people would have started at.

    I think that too many people think that the ear-damaging level they listen to music on their Ipod with is what a home audio system is supposed to do.

    Comment


    • #62
      Adjusting Room sound using material damping methods (not DSP)

      Whilst searching on Wikipedia, I found this. Scroll down to the section marked as above ..... simple, effective and accurate. No tools required!

      http://en.wikibooks.org/wiki/Acousti...pots_In_a_Room
      Alan A. Shaw
      Designer, owner
      Harbeth Audio UK

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      • #63
        Re: "How to Find Overall Trouble Spots In a Room"

        very useful, thank you Adam !

        regards,
        David

        Comment


        • #64
          Measuring toe-in

          Here is a math question for you. If I want to toe in my new C7s, say 10 degrees, is there an equation I can use to measure the two back corners of the speaker from the wall to know the angle that I have? There must be, I just don't know what it is.

          Comment


          • #65
            Re: Measuring toe-in

            Here is a quick calculator for you. Please double check my result!

            All you need to do is decide upon distance d1 from the rear wall to the speakers nearest back corner (in mm, cms or inches) and the toe-in angle which in this worked example is 10 degrees.

            Then, using a pocket calculator find Sine 10 = and that number you fit into a equation as you do the distance d1. The number that falls out of the calculation (d2) you add to distance d1 and that tells you how far away from the rear wall the furthest back corner of the speaker is.

            Hope that helps.
            Attached Files
            Alan A. Shaw
            Designer, owner
            Harbeth Audio UK

            Comment


            • #66
              Re: Measuring toe-in

              Thank Alan, that is perfect. Now I get to count down the days until my Skylan Stands arrive...until then I'll stare at the C7s sitting patiently in the corner of my room.

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              • #67
                Re: Measuring toe-in

                Taking advantage of Google's spreadsheet tool I have made the following from Alan's post. I am not aware of how to protect the cells containing the formula so make sure to only change the cells that are blue in colour.

                NOTE: Unless I discover a way around it, I now realize I need to give individual access to the spreadsheet for you to be able to edit. Please send me an email at [email protected] and I will be glad to do this and send you the link. As an alternative if you have excel I could email you the spreadsheet.

                If you have any questions please contact me

                Don
                Last edited by Don Leman; 08-03-2007, 06:40 PM. Reason: to remove link

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                • #68
                  Re: Measuring toe-in

                  Don: that's a really great idea, but when I try and run it it is locked for viewing only. If you supply me (privately) with the XLS file, I'll see if we can make it available directly to our Users and without file locking.

                  PLEASE NOTE: this is not resolved yet to allow users to enter data into the spreadsheet.
                  Alan A. Shaw
                  Designer, owner
                  Harbeth Audio UK

                  Comment


                  • #69
                    Room treatment and correction

                    My living / listening room is about 6.8 x 4.2 x 2.5 m. This gives me some quite
                    heavy room resonances. With my old HL5LE this wasn't a big problem. But with
                    my M40's, which have much deeper bass, it's a serious problem in the moment.

                    A tool calculated resonances at 25, 50, 76, 101,... Hz. I verfied the ones at about 75 and 50 with a test CD. At 75Hz you have the fear that the walls come down :-)

                    Moving the speakers helps a bit, but not enough.

                    I read a lot of acustic foam in the corners and helmholtz resonator that seem to be quite easy to build. There are also some companies around selling special wall panels and other stuff.

                    Damping the room with big boxes of mineral wool would probably help, but this is not an option. I also haven't yet tried to put socks into the vents. I may try this.

                    I'm looking for another and hopefully nice looking solution.
                    Does anyone have an idea or any experience in this area?

                    Thanks,
                    Thomas

                    Comment


                    • #70
                      Re: How to limit room resonances?

                      I think you are not going to be able to put enough thickness of sound absorber on the walls to make a real difference, so a better strategy is to reduce the amount of bass from the speakers. Suggestion: remove the grilles of both speakers and stuff the ports with foam or even (clean!) pairs of socks.

                      The attached picture shows how poor general-type absorbers are at soaking up low frequencies.
                      Attached Files
                      Alan A. Shaw
                      Designer, owner
                      Harbeth Audio UK

                      Comment


                      • #71
                        Re: How to limit room resonances?

                        Thanks Alan,

                        That's exactly what I assumed. Next I will try some socks. I hope that I can find clean ones. Does it matter if they have holes? :-)

                        Have you ever tried these bass traps? Here is a link to a company that seems to be quite professional in studio technology. (Sorry it's in German)
                        http://www.mbakustik.de/main.php?tar...onanz_absorber

                        With some nice painting the may even look quite good.

                        Comment


                        • #72
                          Re: How to limit room resonances?

                          I stuffed all the vents with damping material. They still have some output, but much less than before. That really helped! But this also removed some of deep bass I love. Unfortunately, we can't have everything ...

                          I have to experiment a bit more. Maybe it's a good idea to fill just one vent or not to fill the vents completely.

                          My understanding is that damping just changes the Q-factor of the bass reflex tuning and not the characteristic frequency. Is that true?

                          Comment


                          • #73
                            Re: How to limit room resonances?

                            Originally posted by T.W.
                            ... we can't have everything ... my understanding is that damping just changes the Q-factor of the bass reflex tuning and not the characteristic frequency. Is that true?
                            Not quite so simple I'm afraid! According to my empirical observations the Q will fall (i.e. the LF system output will broaden over a wider range of frequencies) and so will the level at very low frequencies. Also, I note that the centre frequency of the Q will shift (upwards I recall) by a few Hz.

                            It's difficult/impossible to beat the physics here of deep bass in small, untreated domestic rooms. Those bass traps look very interesting indeed.
                            Alan A. Shaw
                            Designer, owner
                            Harbeth Audio UK

                            Comment


                            • #74
                              Re: How to limit room resonances?

                              In my room - not too different in size from yours - I found getting my M40s away from the walls helped. Also, getting them on high enough stands - at least 23". But ultimately I also added equalization to get a really flat frequency response.
                              A simple analog equalizer helped, but the digital pre-amp/room correction unit I have now is more refined and effective.

                              Comment


                              • #75
                                Re: How to limit room resonances?

                                Yes an equalizer / dsp is propably a good idea. But for now I don't want to have another part in the chain where I can play with...

                                For me room acoustics is an interesting theme. I never really cared about it. But the more I read or "google" about it, the more interesting it becomes.

                                I may ask a professional to analyze my room and to give some advice what to do. It seams to be affordable.

                                When I have moved forward I will post my results here.

                                Thanks,
                                TW

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