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Speaker/Room Measurement Witchcraftery

Discussion in 'audio' started by S-Man, Apr 8, 2018.

  1. Strictly Stereo

    Strictly Stereo Trade: Strictly Stereo

    Suffice to say that the UK distributor Kii appointed in January has rubbed me up the wrong way. It has nothing to do with the product or Kii itself.
     
  2. S-Man

    S-Man Kinkless Tetrode Admirer

    Some very good points. Unfortunately I don't have any stands for the LS50.
    In the past, when I did have stands but no microphone, I tried the boundary loading thing and didn't like the audible result.
    I suspect my LP is around 38% from the back wall/window.

    BTW, Lee from Stricktly Stereo considered my room to be a "good sounding room". That was using the current speaker positions for both Kii3 and CAOW1/ZRB.
    He commented that he could "hear the room" but it was not intrusive. I totally agree that the 30Hz peak is audible. Lee was sat off axis, where the 30Hz lump is more audible than the hot spot.

    LS50/ZRB at my friend's house with a much larger room sounds better. Actually I put it in the "best systems ever" thread. That's why I had to have a pair of LS50s.
    Mine ought to sound even better because I don't have to look at orange drive units :D
     
  3. Ayya Khema

    Ayya Khema pfm Member

    get yourself stands :)
     
  4. S-Man

    S-Man Kinkless Tetrode Admirer

    Spend money to make the measurements better and the sound (most likely) worse :confused:
     
  5. Strictly Stereo

    Strictly Stereo Trade: Strictly Stereo

    I thought that the Kii Three sounded great in your room and that was without getting out the microphone or experimenting with positioning. I only had a brief listen to the CAOW1/ZRB combo. Your room has the potential to sound very good indeed, not least because its length, width and height are all rather different, so the major modal frequencies are spread out somewhat. With the Kii Three placed in the same spot normally occupied by your CAOW1/ZRB, there was some audible "purring" during louder passages when I sat off to the side. I would have pegged that at closer to 50Hz, but it was months ago now and my ears are by no means golden. This sort of thing is to be expected at boundaries and I doubt that moving the speakers will help with this. It was not intrusive and I have certainly heard much worse. I am confident that you can achieve better results than your charts suggest.
     
  6. Hipper

    Hipper pfm Member

    I would be interested to see waterfall plots and perhaps spectrograms (all available using your mdat files of the measurements in REW).

    These will tell is about timing - how long the sound takes to die down, or even if there is some external sound, such as traffic.
     
  7. tuga

    tuga European

    Most of what you describe is high frequency related, partly due to the LS50 tweeter being 2 or 3dB too hot, which is why you see the shelving in the FR above 1.5kHz:

    [​IMG]
    Listening window 20Hz - 20kHz (measured @ 2m, plotted @ 1m) (anechoic)
    Response curve is an average of five measurements: on-axis, 15 degrees left and right off-axis, 15 degrees up and down off-axis
    https://www.soundstagenetwork.com/i...&catid=77:loudspeaker-measurements&Itemid=153

    But the waterfall is very clean meaning no cabinet nor driver resonances, which can affect clarity:

    [​IMG]
    KEF LS50, cumulative spectral-decay plot on HF axis at 50" (0.15ms risetime). (gated)
    Read more at https://www.stereophile.com/content/kef-ls50-anniversary-model-loudspeaker-measurements
     
    S-Man likes this.
  8. S-Man

    S-Man Kinkless Tetrode Admirer

    REW really is rather wizzy!

    I have just found the room simulation thingy and it would appear to tally very well with my measurements. I have aligned the x axes:

    [​IMG]

    My LP is ~37% from the back wall/window.

    My conclusion is that my speakers are so damned accurate at LF that they can be used to measure the room! :cool::D
     
    ToTo Man and tuga like this.
  9. Strictly Stereo

    Strictly Stereo Trade: Strictly Stereo

    If he wants to give me a call, I would be happy to help. Probably of more use to him are the step-by-step guides I found on the Internet a while back. I have the links saved somewhere. I will try to dig them up.
     
  10. Tony L

    Tony L Administrator

    I think its a little hot as its a coaxial driver and drops a fair bit off axis. They certainly don’t sound over-bright with a typical toe-in so they are crossing a fair bit behind the listening seat IME. No one listens to anything on axis at a metre!
     
  11. tuga

    tuga European

    According to Soundstage the measurement above, taken at 2 metres, "Averages five frequency response measurements and plots them as a single frequency response. The five frequency response measurements that are averaged for the Listening Window are: on-axis, 15 degrees left and right off-axis, 15 degrees up and down off-axis."

    The following plot, with measurements at 2m, shows that the tweeter response is still exaggerated at 15º:

    [​IMG]
    Frequency response 20Hz - 20kHz (measured @ 2m, plotted @ 1m)
    Top curve: on-axis response
    Middle curve: 15 degrees off-axis response
    Bottom curve: 30 degrees off-axis response
    https://www.soundstagenetwork.com/i...&catid=77:loudspeaker-measurements&Itemid=153
     
  12. tuga

    tuga European

  13. S-Man

    S-Man Kinkless Tetrode Admirer

    I think the LS50 is a bit hot around 2.5KHz. My pal actually uses a budget vintage analogue graphic equaliser to take them 2 or 3 dB down at that frequency.
    in his system they undoubtedly sound much better that way versus bypassing the graphic equaliser.
    In my system, I didn't find the ALSAmixer software equaliser helped in the same way. I prefer to tune the mid forwardness with careful choice of cables :eek::eek::eek::eek::eek:
     
  14. Ayya Khema

    Ayya Khema pfm Member

    as we can see the forwardness is the ls50 when listened on axis. when 30 degree off axis, it make the whole 2khz to 10khz flat. when I had my kef ls50, i preferred the ls50 with no toe in as well. but the metallic tonality was still apparent even if it measured flat off axis.
     
  15. Tony L

    Tony L Administrator

    Interesting. I do like the LS50, but I’ve only heard them in a very high-end system (Conrad Johnson etc). I didn’t notice anything odd or metallic about them at all, very open and natural on the jazz material I favour with a surprising sense of scale and impact for such a tiny speaker.
     
    jologstyme likes this.
  16. Elephantears

    Elephantears Trunkated Aesthete

    I heard the LS50 at Dave's place with the ZRB some time ago; I had a pair then and took them around for comparison. I was amazed at how clean they sounded with the ZRB. I would like to hear a pair of LS50s again; perhaps I'll end up buying some for a third time! I still cannot quite account for the treble performance. On the one hand they have this forward presence region, which does not offend me - perhaps it is forward in the right part of the presence region for my ears (I do have issues, however, with a peak at 3Khz with my current speakers). On the other hand, I am going to have to repeat myself and mention that trumpet problem again. Well, Ayya has mentioned the metallic issue again, and we've already been through that discussion a year or two ago (Dave and I heard it once, then never heard it again, as far as I remember). I've still not heard any explanation as to why the LS50 cannot convey Freddie Hubbard in full reach or Miles with harmon mute, and certainly nothing in the measurements explains it. However I believe Dave has heard much better results from trumpet recordings since.

    Regarding measurements, just an aside, but I was recently looking through all the various measurements of speakers I've taken over the last 2 or 3 years, and I noticed two or three things. One was that measurements taken with REW do not correlate very precisely with those taken with Dirac. The second is that I have certain room mode characteristics that are the same for virtually all speakers (e.g. 40Hz peak followed by big trough at 63ish). The third is that some of these speakers sounded completely different when their FR was almost identical in all but the presence region.
     
  17. S-Man

    S-Man Kinkless Tetrode Admirer

    I think that quite gross one-off "colouration" we heard must have been an aberration. I have never heard anything like it from my new LS50s (mind you, the new black drivers obviously sound much calmer than those orange ones :)) or any others. I wonder if AK's "metallic issue" is perhaps what others hear as forwardness?

    On your 2nd para...
    The REW room simulator is quite enlightening and can certainly save a lot of moving and measuring - or buying of speaker stands. I urge anyone to try it out and "drag" the sub(s) around and it soon becomes apparent that the room peaks are troughs are only modestly affected by the sub position(s). The only arrangement that seems to defeat the room modes is the "Move subs to wall midpoints" one, but this would totally destroy any time alignment and I have no idea what effect it would have with stereo bass (like mine). So far I haven't found any reason to change my opinion that putting a "flat" signal into a real room sounds better than eq'ing the signal to counteract the room effects. OTOH I have heard a system with gentle eq that sounded superb, so I guess it's all a question of balance and moderation.



    I will not be able to take any more measurments for few days.
     
  18. Ayya Khema

    Ayya Khema pfm Member

    The "metallic" coloration is probably brightness. When swapping my atc scm7v3 and p3esr and the kef ls50, they all measured almost precisely the same (proof that in room response FR trumps any small anechoic difference in the speaker "built in FR").

    however, the atc scm7v3 and p3esr had very similar sound. The kef ls50 imo sound edgy in comparison, like overly crisp. Impressive at first, but not as musical to me, too analytical. Without talking about the boomy bass that adds 10% THD at 100hz when driven at 85db. Imaging is very good, but I heard a distinct colouration in The timbre of instruments, every sounds had that sort of coloration, making everything sound the same. In 3 different room, with different front end, it was obvious that the p3 and scm7 shared very much the same sound, and the kef ls50 was brighter.
    how can you find the best speaker placement without stands?

    why do you think when you have better measurements you have worst sound?
     
  19. Ayya Khema

    Ayya Khema pfm Member

    ok. Then you need to look at your Listening position (where your mic is) which is directly in a room mode.
    as a experiment, place each sub against the front wall, behind each speaker. then move your mic (listening position) around. you should be able to find a area that give the flattest result. then, dont move the mic (LP) around anymore. now take each sub and move them around to find the best Frequency Response.

    problem with trying to EQ room problems, especially dips like yours that are 15db deep which is clearly a room mode,its well known that room eq can help to reduce peaks, not really helpfull to improve dips.

    Digital room correction is a great in untreated rooms, but Id do everything I can to at least deal with your 40hz dip and also the 70hz and 100hz dip.
     
  20. cooky1257

    cooky1257 pfm Member

    Bit obvious I know but have you tried inverting the polarity of either your subs or the Kefs?
     
    Ayya Khema likes this.

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