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Adjusting Room sound using material damping methods (not DSP)

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  • #76
    How far to sit from speakers

    Because of my room, the most I can mangage is approximately an 8' equilateral triangle between my head and the speakers. One thing I love about Harbeths is that, due to their monitor heritage, they work very well in the nearfield.

    I couldn't care less about what "order" crossover is in a speaker, but I have heard that you need to sit further away from speakers with first order crossovers to make them sound coherent. Is that true, and why is it so? Is 8' going to work or is something more necessary.

    The reason i'm asking is because I'm going to audition the M30s, which my dealer believes is extraordinary. However, he is also a Sonus Faber dealer and he thought I might like to listen to the Cremona Auditor, roughly in the same price range. I know these speakers have a 1st order x-over and I thougt i'd ask.

    I'm heavily biased towards the M30s, although I'm willing to listen. Thanks for you help.

    Comment


    • #77
      Re: How far to sit from speakers (filter orders)

      Originally posted by Chayro
      ... I couldn't care less about what "order" crossover is in a speaker, but I have heard that you need to sit further away from speakers with first order crossovers to make them sound coherent...
      I don't know much about 'first order filters' used in some other speaker crossover networks but I think what you are referring to is the overlap of energy where the drive units are simultaneously reproducing sounds around the crossover frequency. Not ideal.

      What is a 'first order filter' - or indeed a 'third order filter'? It's simply a way of describing how steeply the sound is handed over from one drive unit to another through across the audio spectrum, how the designer makes a cross-over between the top end of the woofer and the bottom end of the tweeter.

      If the crossing over is very gradual covering a very wide frequency range as it would be with a 'first order filter' which is a very simple network with as few as two components (!) this seems to be asking for trouble. At worst, it means that the tweeter is forced to pass not only high frequencies, for which it is optimised, but some mid frequencies which leak trough to it because of the simplicity of the network. It also means that at the very top end of the woofer/midrange driver (where the response is no longer perfectly smooth because if it was you wouldn't need a tweeter!) it will be attempting to reproduce high frequencies which have leaked through to it via the simple crossover network.

      The solution is of course to use more components - hence a higher 'filter order' (third order being a higher order than first order) where each drive unit is fed sound appropriate to its optimum capabilities. When you listen to hi-fi speakers you can quite often hear tweeters 'barking' and that is a sure sign that they are being operated uncomfortably low and are under mechanical stress. You can also hear a loss of purity - a sort of mush - because bass/mid drivers are far to heavy to trace the lower high frequencies properly and is fighting the tweeter's contribution.

      As I understand it, with a first order filter you need to be some distance away so that in the crossover region the sound waves from the two drivers can somehow merge according to the position of your head vertically and/or you can find a point vertically where you can hear more tweet and less mid.

      This sort of issue is the result of the designer taking a strong line on a particular aspect of the design - as we all do in our own ways. If the designer strongly believes that fewer components in the crossover must sound better then he is trapped by his low-order filters with all their (insurmountable) issues. If he takes the line (as I do) that every real-world drive unit has its optimum working range then he'll go for whatever complexity is necessary to get the best from them.

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

      Comment


      • #78
        Re: How far to sit from speakers

        Alan - thank you for your detailed reply, but as it turned out, it wasn't a problem. As my dealer explained, the listener should not worry about what's in the box, just what sounds better. Sensible advice, I think. In any case, after the audition, I'm sitting in front of my computer listening to my new Monitor 30's. Well done Alan.

        Comment


        • #79
          Re: How to limit room resonances?

          Originally posted by T.W.
          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...

          TW

          Here are some ideas for the bass:

          http://www.sennheiser.com/klein-hummel/globals.nsf/resources/tmt2002.PDF/$File/tmt2002.PDF

          http://www.avsforum.com/avs-vb/printthread.php?t=837744

          I trust Frau T. W. will not object......

          Comment


          • #80
            Re: Measuring toe-in

            This isn't an exactly an answer but I thought it might be of interest. This is my toe-in adjustment technique.

            Gather up a piece of string or fishing line that will reach from the back of the listener’s chair to at least the rear of your loudspeaker. Now insure that the listener’s chair is centered and equidistant to the loudspeakers. Anchor one end of the string to the center of the back of the chair at ear height with strong tape, tied to a weight, or attached to a safety pin. Holding the other end of the string bring it to the inside front corner of one of the speaker cabinets. Mark that point on the string with a permanent marker. Now adjust the toe-in so the outside front corner is that same distance and recheck both corners. Okay, do the other speaker using that same mark for the inside and outside corners. When all corners are the same distance from the anchor point the speaker cabinets will be equidistant to the listener and tangent to an arc with the center point (focus) approximately at the listener’s ears.

            Ron

            Comment


            • #81
              Re: Measuring toe-in

              From personal experience id agree most with the latest post, since i've found that aligning the speaker with the listener is far more important than lining it up to the walls. Also one must not assume (as its my case) that walls are perfectly 90 degrees to eachother, floors and ceilings are perfectly horizontal etc..

              Comment


              • #82
                Professional (BBC) Room treatment and correction

                This thread concerns techniques that have been used to treat the listening room. Much research was undertaken by the BBC who had a thorough grasp of the technical requirements of well balanced studio and monitoring environments as long ago as 1930. These solutions involve new-build considering the room acoustics right from the first architectural drawings and to damping (lagging) existing rooms.
                Alan A. Shaw
                Designer, owner
                Harbeth Audio UK

                Comment


                • #83
                  BBC (original) Broadcasting House, 1932

                  The document covering the 1932 construction ..... (to follow)
                  Alan A. Shaw
                  Designer, owner
                  Harbeth Audio UK

                  Comment


                  • #84
                    Re: Getting the best from your listening room [size, furnishings, construction]

                    Hi! Good Day!

                    I recently purchased a Harbeth HL-P3 ES2 (still in transit from overseas)...I am currently using a Conrad Johnson Evolution 200wpc Power Amp (w/ 4 x 5751 inout tubes), Counterpoint SA-1000 Tube Pre-Amp and a pair of floorstanders...I've been to a friend's store and the P3s are giving me sleepless nights after I've heard them...So I've taken a bite at the bullet and purchased a pair (in Eucalyptus Real Wood Veneer)...My room size is approximately 11feet x 15feet...I have been used to the "low-end" that my floorstanders deliver...With this room size, would you think (given the proper placement and toe-in), the P3s will give me sufficient bass particularly for fast music like rock, acid jazz??

                    Thanks! :D

                    Comment


                    • #85
                      Re: How to limit room resonances?

                      An effective, flexible and cheap (assuming you already have the raw materials) solution to bass issues in room is a strategically placed bookshelf or two (or three or four). Books and speakers

                      The bookshelf in the picture has also helped deal with some grievous corner loading issues.
                      Books have also allowed me to fine adjust damping and resonance control. It's very cheap and easy to do.

                      The Yamaha speakers are excellent (3-ways approx same size as M40s), but I'm looking forward to the M40.1in Japan (finally)!

                      Comment


                      • #86
                        Listening in a concrete room ....

                        Hi Alan and Others:

                        Alan, when you design Harbeths, are you assuming that a listener will be seater at least a specific distance from the speakers? I am seated about 5.5 feet from the speakers measured from my ear to the woofer. Alan, in another post, you referred to Harbeths as having a Low Q, relaxed sound. Well, at that listening distance, My Monitor 30's are anything but relaxed. The sound is definitely high intensity, particularly when I listen with them pointed at me.. They are slightly more than 50" from the wall behind them.

                        Because of my room's concrete construction, it really holds onto bass, which is why I place the speakers so far out into the room. Also, the wall behind the speakers has a large expanse of glass window and positioning the speakers well out into the room, helps with that. I also have heavy drapes and quarter-round bass traps in the front corners. Listening off-axis does reduce the level of intensity and yields a more relaxed sound at a slight loss in detail and less pin-point imaging..

                        I am wondering if I am violating any design principles with respect to how close I can sit to the speakers? Can good results be achieved with really nearfield listening and if so, does one have to make any accommodations for listening very hearfield?

                        Thanks,

                        Jay

                        Comment


                        • #87
                          A seething mass of ripples in the listening room ....

                          Um. You have a very difficult acoustic environment - concrete walls (+ floor/ceiling) is really the worst possible situation for listening to hi-fi. What you are experiencing is a sound at your listening position which is dominated by the room's surface reflections.

                          To visualise what is going on inside your room, its easier to imagine waves in water than sound waves in air. Don't try this at home! - but this may help. Imagine your listening room is completely sealed and water tight. Fill it with water right up to the ceiling and wearing your diving gear (with oxygen bottle) get into the room with a heavy cricket ball. The ball will represent sound waves as they radiate from the speakers. Stand where the speakers would be and throw the ball towards your listening seat. Observe ....

                          1. As the ball travels towards your listening seat it leaves in a wake its path ...
                          2 ... this wake will radiate as an expanding cone behind the ball in along the height and width directions i.e in 3D ...
                          2. ... the wake spreads out behind the moving ball until it touches nearby surfaces ....
                          3. ... by the time the ball passes your seat the wake has widened out so much that it has reached the floor and probably nearest side wall, and shortly thereafter the wake will touch the ceiling ...
                          4. ... the ball continues past your seat until it hits a surface behind your seat, probably the rear wall ....
                          5. ... according to the angle the ball hits that surface it reflects at the same angle off the surface (as all tennis players know) ...
                          6. ... and probably arrives at the opposite side wall, and according to the incident angle it hits the side wall it bounces off ..... until it runs out of energy seconds later ...
                          7. ... meanwhile, the wake the itself also bounces off surfaces according to the incident angle ....
                          8. and within a few seconds the entire room has been transformed from tranquil, still water to a thrashing mass of ripples as every molecule of water (air) in the whole room space has been energised and is in motion.

                          - and that's just with the first pulse of sound, the first note, from one speaker! Imaging the seething confusion of ripples when two speakers are playing a distance apart! It is a miracle that the human brain can tease out of this sonic mess anything that resembles natural sound. Even the most complex computer would have the greatest difficulty doing that.

                          So, what can you do to help improve the situation? The simplest way is to sit closer to the speakers so that what you hear is more of the direct sound from them, and less reflected sound from surfaces. Second, you can make the surfaces more absorptive, especially those surfaces near to the speakers - floor, side wall and behind the speakers so that those early reflections (from surfaces near the speaker) are robbed of some energy, so that there is less they can reflect and pass on. Those really are the only options available.

                          Incidentally - if you don't fancy flooding your room (and who would!) you can achieve a somewhat similar effect next time you are in the dentist's waiting room. Wait until you are the last one in the room, put your hand into the tropical fish tank and furiously agitate the water; watch how the ripples fill the tank. (Caution: think of the fish; think how you can explain the wet arm to the dentist as you lie dripping in his clean chair).

                          Does this help?
                          Alan A. Shaw
                          Designer, owner
                          Harbeth Audio UK

                          Comment


                          • #88
                            Re: The best from your room [size, positioning furnishing, construction, temperature]

                            Alan

                            Thanks so much.

                            You have only scratched the surface of how bad the room is. The walls are concrete and cinder-block with a skim coat of plaster. The floor and ceiling are 18" of concrete. It is L shaped with no true rear wall (opens into an entrance foyer) and it is only 12 feet wide. I have rugs and drapes and a bookcase on the left wall near the speakers and LP's on that same left wall.

                            Questions:

                            1) Is there a minimum distance regarding how close one can sit to the speakers?
                            2) In this type of room nightmare, should the speakers be fireing at you (on axis) and pointing at you or your ears?

                            Thanks,

                            Jay

                            Comment


                            • #89
                              Re: The best from your room [size, positioning furnishing, construction, temperature]

                              I feared that might be the way your room was constructed. To answer ...

                              1). No minimum. You can 'wear' your Harbeth speakers like headphones. One of the remarkable properties of a Harbeth is that even very close, they sound sweet. Try that with other speakers and they harden-up as you get closer to them.

                              2). I truly can't answer that. Listening off axis (i.e. speakers are parallel with the walls and you sit at the apex of a triangle) will slightly reduce the energy at the bottom of the tweeter band a little. This may reduce harness - conversely, it may spray more energy into the room, and onto those side walls in that irritating frequency band. See how difficult it is to give advise? I'd strongly recommend some sort of drapes over the side walls, and then play around with to-in.
                              Alan A. Shaw
                              Designer, owner
                              Harbeth Audio UK

                              Comment


                              • #90
                                Re: The best from your room [size, positioning furnishing, construction, temperature]

                                Thanks Alan

                                Drapes along the side walls. That would start WW IIII. I have bookcases and 2000 LP's along the left wall, so that should help a bit. The pleated drapes on the wall behind the speakers, which has widows the width of the room and half-way up the wall, really cut down the energy.

                                I am usually reluctant to draw the drapes, since we are blessed with a NYC skyline view that is spectacular, but I may have to resort to that for serious listening. I have oriental rugs on the shorter right wall that opens into the "L" and in the adjacent open dining area..

                                There is only so much that I can do and maintain domestic harmony.

                                Thanks so much.

                                Jay

                                Comment

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