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shots fired across the bow! (engineers vs 'the hifi people')

Discussion in 'audio' started by Jonathan, Jan 4, 2019.

  1. yuckyamson

    yuckyamson pfm Member

    The only way to really settle this argument, in my opinion, is to bring in Bob Stewart to mediate.

  2. suzywong

    suzywong pfm Member

    Who is Bob Stewart?
  3. Jonathan

    Jonathan pfm Member

    honestly I've seen LOTS of writing about physical science (aka 'physics') in audio journals throughout the years - i'd like to think I'd learned a thing or two - technical discussions are everywhere in audio - and to be honest it's what inspired me to do my first undergraduate degree in physics ... though i cannot speak for others nor maybe familiar with the particular people which you speak of ...
  4. davidsrsb

    davidsrsb pfm Member

    One of the problems is that the physics of amplifiers is well understood and has been since Peter Walkers time. This means that there is little to write about or really innovate.
    The acoustics of the room is another story, while we know the physics, actually calculating the behaviour of a real room with furniture and doors etc is not practical yet.
  5. Purité Audio

    Purité Audio Trade: Purite Audio

    Simply use a microphone and REW software.
  6. davidsrsb

    davidsrsb pfm Member

    Measurement after the installation. Predicting the behaviour is much more challenging. There have been some high profile disaster concert halls.
    Jonathan and Dozey like this.
  7. h.g.

    h.g. pfm Member

    It has been relatively straightforward for a few decades. It is common these days to listen to binaural recordings of the acoustics of a room when designing a new building. Obviously this is for architects working with acoustical engineers and not salesmen of add on acoustic room treatment products like EW. However, even here, if you look on room acoustic product web sites they usually have data for their own products to include in room simulations.

    I am intending to start sorting out the acoustics of my living room in a few months and will do so primarily by simulation. It is a poor shape and the configuration makes it difficult to place speakers in the optimum locations. The acoustic properties of the walls and furniture will initially be estimated to avoid having to lug stuff around but if anomalies remain I will measure what needs to be measured. It won't be as accurate as using the facilities in an acoustics lab but should be sufficient to quantitatively get on top of the room acoustics in order to determine what will and won't work.
  8. h.g.

    h.g. pfm Member

    And the reasons for those disasters were? (hint: acoustical engineers are not in charge and the visuals are often considered more important by those with the power to make decisions).
  9. davidsrsb

    davidsrsb pfm Member

    I have never seen acoustic modelling to the level of furniture etc.
  10. darrenyeats

    darrenyeats pfm Member

    In-room measurements give you part of the story. Reverberation time is interesting (bass waterfall and RT60, that type of thing). But separate from that in my book is the location of surfaces relative to speaker and listener, and set up of speakers relative to listener - I wouldn't try to decide such things with mic and chart, any more than I would determine room modes by ear.
    Last edited: Jan 7, 2019
  11. Cesare

    Cesare pfm Member

    I think you have if you've been in a modern auditorium, as I believe unoccupied seats are designed to absorb as much as ones occupied by people, so that the reverb isn't unduly influenced by the size of the audience.
  12. Purité Audio

    Purité Audio Trade: Purite Audio

    Why on earth not, keep the microphone still and experiment with positioning of the speakers, listen and use the measurements to corroborate, same procedure with your listening position.
    Unless you have a dedicated room there are probably only a few placement options.
  13. ToTo Man

    ToTo Man the band not the dog

    Measurements can show you the best placement for speakers in terms of frequency response, decay times, reflections, etc, but not where the best placement is to recreate a believable soundstage, IME this can only be done through backbreaking trial and error and trusting your ears, unless of course you want to cheat and use DSP to optimise time alignment etc.
  14. h.g.

    h.g. pfm Member

    This is what basic level room acoustic simulation looks like today as would be typically taught and used on undergraduate teaching programs.
  15. davidsrsb

    davidsrsb pfm Member

    A lot better than I expected, but still simplified for dry wall, false ceilings etc. I suppose that there is a lack of data on many construction materials.
  16. h.g.

    h.g. pfm Member

    This is one of the significant problems with my new living room which is far from symmetrical and likely to have a convex corner close to the seating position. I am expecting the better solutions to come from using a relatively narrow beamwidth for the main speakers with a small amount of strategic absorption to limit the strength of the louder earlier assymetrical reflections. DSP is not a substitute for either of these. Inevitably given Sod's law I bought a pair of wide bandwidth coaxial drivers just before moving house.

    I agree that there can be many configurations to consider but simulations are much more efficient at sorting things out than measurements because they tell you why things are as they are which guides the next step. Measurements are both limited in scope (not everything everywhere throughout the room) and require whatever is being considered to be physical present and installed in the room (way too much time, money and effort to consider). One obviously needs some measurements to check the simulations are behaving but I wouldn't even consider sorting my living room if they were the primary approach.
  17. ToTo Man

    ToTo Man the band not the dog

    Are there any free Room Simulators available that are better than the one in Room EQ Wizard? The REW Room Sim is less accurate for the speakers located on the right side of my listening room than those located on the left side. I presume this is because I have a door located nearer the right speaker, which I am unable to model in the REW Simulator (if you think any other construction features are contributing to this divergence then please feel free to comment! :)).

    My room layout and acoustic treatments:

    REW Simulation for left & right speaker independently (subwoofers excluded), assuming 15% absorption (I have no idea how to estimate the amount of absorption in my room):

    Actual measurement of left & right speaker independently (subwoofers excluded) with 1/48th smoothing applied:
  18. darrenyeats

    darrenyeats pfm Member

    What if the best measurements occur with speakers 6 inches apart?! There are some considerations separate from mics and charts.
    mattgbell and ToTo Man like this.
  19. davidsrsb

    davidsrsb pfm Member

    You need subs with big Tannoys in that tiny room?
    Rotating everything with the speakers facing the door might help. The bay window behind your left side is going to mess reflection
  20. hammeredklavier

    hammeredklavier owner of two very cheap hi-fis

    Why? The null test tells you absolutely and certainly whether two signals actually differ and by how much. If two amplifiers null down to below -60dB or so then you can be pretty sure they will sound identical.

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