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Since its inception ten years ago, the Harbeth User Group's ambition has been to create a lasting knowledge archive. Knowledge is based on facts and observations. Knowledge is timeless. Knowledge is human independent and replicatable. However, we live in new world where thanks to social media, 'facts' have become flexible and personal. HUG operates in that real world.

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The Moderators' decision is final in all matters regarding what appears here. That said, very few Posts are rejected. HUG Moderation individually spell and layout checks Posts for clarity but due to the workload, Posts in the Subjective Soundings area, from Oct. 2016 will not be. We regret that but we are unable to accept Posts that present what we consider to be free advertising for products that Harbeth does not make.

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Adjusting Room sound using material damping methods (not DSP)

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  • Room treatment - a little at a time and a thorough proposal

    I'm in the process of designing and building acoustic absorbers and bass traps for my business. The idea came recently whilst preparing the living room for my SHL5's, soon the be delivered. Looking at the absorption coefficients, most rooms can be adequately treated with a broadband absorber behind each speaker and to the adjacent walls, with a bass trap in the corner. I had a look at the rather ugly foam options for bass traps, but unless they have a true density of 45kg/m3 they are all but useless below 500Hz. A far better approach is to use glass fibre wool (loft insulation is perfect) in at least 45kg/m3 density, preferably 60kg/m3 and make up some 1.2m by 300mm by 100mm thick pine panels. Fill these with the insulation and cover in acoustic fabric.

    At 100mm thick, the wool has an acoustic absorption coefficient some 4 times greater than that of 50mm panels. Place across the corners of the room. Bass which isn't absorbed will pass through the panel into the air gap to the corner, and be reflected back through the panel, cutting down bass boom quite effectively. You can make larger panels using the same design and have them free standing 0.75m behind the speakers with a small air gap to the rear wall, for the same effect.

    Making up 50mm panels using the same materials and placing on the points of first reflection plus another few along the rear wall is all the average under-damped room will need to make a significant improvement. These panels will be far more effective than the cheaper thin foam tiles commonly available and can be covered in FR acoustic cloth to a colour to closely match your own decor.

    It's important not to overdo it though as overall SPL levels can be reduced considerably and the room made too "dead". A little at a time, then listen to the results is the key. You cannot overdo bass traps though. The more corners treated the better.

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    • Stick-on surface treatments

      Attached a scan of the Vicoustic brochure. They specialise in surface treatment for absorption of room sonic reflections etc.. There are numerous examples of real-world rooms. The makers have done their best to offer a range of attractive styles and finishes, to suit all tastes?
      Attached Files

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      • My experiences with Vicoustics dampers

        Originally posted by HUG-1 View Post
        Attached a scan of the Vicoustic brochure. They specialise in surface treatment for absorption of room sonic reflections etc.. There are numerous examples of real-world rooms. The makers have done their best to offer a range of attractive styles and finishes, to suit all tastes?
        I used some more Vicoustic products to dampen my ceiling (adding to big bass absorbers in the corners and some Vicoustic Damping at the wall behing my listening position).

        The picture shows my construction. It combines some damping and difusers (and some lamps). In my opinion it looks quite good. At least for a listening room. In a living room it might be a little over the top.

        The acoustic result speaks for itself. The sonic improvement is quite obvious. Resulting in a pretty good sounding room. Something that you only realize when you know both versions. I doubt that many rooms sound good without any help in that area.

        100_0180 (Large).JPG

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        • The Schroeder Frequency and how it Effects Room Treatment

          I would like to offer my current views based on my limited experience of the last ten years trying to get the best out of my domestic listening room.

          Sound in the room behaves in two different ways depending on its frequency. Lower frequencies resonate with the room and higher frequencies reflect. The dividing point where frequencies change from one behaviour to the other is called the Schroeder Frequency and varies for each room based on room dimensions. It's usually around 200Hz for a typical domestic listening room. These two different behaviours can be treated differently.

          With bass (those frequencies below the Schroeder value in your room) absorption is the solution and you need to absorb as low {a frequency} as possible. I first used Auralex foam products and thought I got a good sound. These absorbed down to 125Hz but did little below that. As my understanding grew I changed to GIK Soffit Bass Traps, which absorb down to 50Hz and a bit below. The result is much better room bass. In other words, along with very careful speaker and listening positioning (and a bit of EQ), I can now hear more of the music's bass and much less of the room's. That I think is what you should be trying to do for the frequencies below the Schroeder Frequency in your room. It's remarkable how important getting the bass right is and until I did, I hadn't fully realised that.

          For the reflective frequencies (above around 300Hz) it's not so simple. You would think that only the direct sound from the speakers, with all the information from the recording, would be all that we should want to hear and reflections would either add unwanted sounds or muddy the music. This is made more complicated by the Psychoacoustic phenomenon called the Haas effect already mentioned on this thread (reflected sound received by the ear within a certain time after the initial note - around 30 milliseconds or so - will be added to that note, but any reflected sound received after that time will be heard as a new note, or echo).

          Of course there are not just first reflections, but second, third etc., getting weaker the more reflected depending on the material of what is reflecting it. Floyd Toole in his book 'Sound Reproduction' says that whilst it's good to have absorption on rear and front walls, most listeners preferred reflections off the side walls, or rather first reflections. This gives that sense of spaciousness that we get in real world music listening.

          My experience is that this is true. I have absorbers on the back wall (behind my ears), and absorbers and diffusers on the front wall but nothing on the side walls (or ceiling for that matter).

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          • Egger room treatment materials and a handbook

            I am thinking about mildly treating my room and was referred to the mostly wooden products of the Egger company. The stuff looks clean and will fit modern home decors. Here is a catalogue and towards the end a long text explaining room acoustics and treatment. Here: http://www.egger.com/downloads/bilda...esungen_EN.pdf

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            • Collected links to articles concerning the design of listening rooms

              Here is a collection of links to some publications related to the design of listening rooms. Some of these were mentioned in previous responses made to this thread. I thought I'd collect them in one place for easier reference.

              1951 - Recording studio design
              1951 - An investigation of small talks studios
              1958 - The acoustic design of talks studios and listening rooms
              1966 - Data for the acoustic design of studios
              1983 - LEDE control room design
              1990 - BBC Engineering Guide To Acoustic Practice
              2004 - Building a reference grade listening room
              2007 - Room reflections misunderstood?
              2015 - Acoustics of small rooms, home listening rooms, recording studios
              2015 - Acoustical Physics of Music: Lecture Notes and Other Hand-Outs

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              • Taming minimalist decor

                Thank you very much indeed. It is a lot of study, but I am sure it will be an important upgrade. I have been very happy with the Antimode 8033 room equalization for my subwoofer, and this has made me acutely aware of the importance of the listening room.

                My listening room needs a new coat of wallpaint, so this is the right moment. I was attracted by the wooden Egger panels because, unlike foam stuff, they do not attract house dust (I am allergic). Esthetically, I am in the modern minimalist camp, and the Egger panels beautifully blend in with that.

                First, however, it is time for study to figure out what I need. So thank you Witwald.

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                • Thanks a lot.

                  ATB

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                  • Now... acoustic panels?

                    Very useful information, thanks all. I have just today received my P3ESRs, and am finding the room reflections quite bright, robbing the speakers of any sweetness.

                    Actually, one of the reasons I bought them was for a darker, more neutral sound after my bright B&W 685s, but it seems much of the brightness was my room after all (not that the Harbs aren't an improvement in themselves, especially at sociable listening levels). Time to invest in some acoustic panels, methinks.

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                    • Diy

                      You can DIY for minimal outlay. No need for expensive treatments.

                      {Moderator's comment: There is a full article about sound proofing materials in Sound-on-Sound magazine out now}

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                      • Room treatment...

                        Sound Proofing and Room Treatment are different things.

                        Sound Proofing usually means stopping sound getting in, or out.

                        Room Treatment is trying to control the acoustics in a room so that it sounds better.

                        DIY for acoustic room treatment is of course much cheaper and there is plenty of advice on the net. However working with fibre glass, if that is required, is in my experience a very unpleasant experience, even when you are clothed properly.

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                        • My new room plan

                          I am in the process of completey overhauling my music-room.

                          New cosmetics (colours, curtains, and so on) but also, and more interestingly for the folks in this forum: enhanced acoustic treatment.

                          Meaning: the whole ceiling is being made of a wooden acoustic ceiling.
                          This in addition to corner-blocks of Rockwool and the Vicoustic elements on the back wall (where I sit relatively near to) should result in a pretty good room, acoustically.

                          The work has mostly been done in recent weeks (evenings after my dayjob) and will be finished in (hopefully) the next week.

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