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Upgrading my acoustical room treatments

Discussion in 'audio' started by ToTo Man, Sep 14, 2021.

  1. ToTo Man

    ToTo Man the band not the dog

    Funnily enough the way I have the speakers and mic aligned just now the stereo and average measurements are a perfect mirror of each other, but I only experience this once in a blue moon!

    See this Gearspace post for more info on the pros and cons of single and dual measurements:
    Two speakers or one speaker for ETF,REW etc? - Gearspace.com
     
    tuga and Tony L like this.
  2. tuga

    tuga Legal Alien

    Looks a lot better. Are you applying EQ over the whole range or just the bass and sub-bass?

    The upper-bass has improved a lot but the peaks in the mid-range look a bit nasty, particularly the one at 600Hz. If you're still feeling like it, perhaps you could try moving the mic some 10cm forwards (maybe also backwards if possible), just to see what happens.
    Also, have you repositioned the side panels in the early reflection zones?
     
  3. ToTo Man

    ToTo Man the band not the dog

    I've applied narrow notch filters at 43Hz (-3dB), 52Hz (-5dB), 85Hz (-1dB), and 107Hz (-1dB), and a broad notch filter at 800Hz (-2dB) which covers from 400Hz-2kHz as the Ditton 66 naturally has around 2dB too much output across these frequencies.

    The 600Hz peak needs attention but I don't like to apply narrow notch filters in the midrange. I'm pretty sure this can be improved either by adjusting the toe-in, the listening position or repositioning the side panels in the early reflection zones as I haven't done this yet.
     
    Last edited: Oct 3, 2021
    tuga likes this.
  4. ToTo Man

    ToTo Man the band not the dog

    Third stage of testing: measuring effect of listening position

    For this test I positioned the speakers more like how I’d be listening to them, toed-in a little and tilted backwards by around 30mm to achieve correct phasing at the MF/HF crossover frequency. This necessitated pulling them forward slightly so that the inside, middle edge and outside edges of the baffle were 36cm, 42cm and 47cm out from the front wall. Distance to side walls remained at 103cm.

    I then varied the distance of the mic to the back wall in 5cm increments from 60cm to 190cm (190cm = the midpoint of the room).

    Graphs below show stereo speaker measurements in 10cm increments because there are too many overlays for every 5cm increment.

    Summary of results:
    - 75Hz null gets significantly smaller as LP moves towards middle of room.
    - 75Hz null moves higher in frequency towards back of room and lower in frequency towards middle of room.
    - 95Hz null gets slightly smaller as LP moves towards middle of room, but not a huge improvement.
    - 95Hz null moves slightly higher in frequency towards back of room and slightly lower in frequency towards middle of room.
    - Flattest response from 100Hz-400Hz when LP 160cm from back wall, +/- 7.5dB with 1/48 smoothing, but loses too much support from 43Hz axial mode.
    - LP 130cm or 140cm from rear wall is better compromise, 43Hz now at a level that no longer needs cut or boosted with EQ, and 100Hz-400Hz response is +/- 9dB with 1/48 smoothing.
    - The 43Hz axial standing wave cancellation behaviour suggests that the 'modal midpoint' of my room is 180cm from the back wall. I expected it to be at 190cm which is the physical midpoint of the room, the bay window must pull the modal midpoint back a little.
    - Something funky is going on between 600Hz-1kHz but I’m confident this will resolve by adjusting toe-in angle and applying absorption at first reflection points.

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]
     
    Last edited: Oct 5, 2021
  5. cooky1257

    cooky1257 pfm Member

    Thought you may find this before and after comparison from your refurb thread measurements vs the latest ones interesting.. far field on mid axis on the left.

    [​IMG]
     
    ToTo Man likes this.
  6. ToTo Man

    ToTo Man the band not the dog

    Which areas of difference are catching your eye? It's difficult to compare as I'm using 1/48 smoothing on these latest measurements to really magnify the size of the nulls. Also the old measurement on the left shows Left speaker only whereas the new measurement on the right is a stereo measurement, so again not an apples-to-apples comparison.
     
  7. cooky1257

    cooky1257 pfm Member

    Yeah I see. It's not quite like for like but the earlier measurement looks generally better to my eyes(700hz not withstanding) so I thought it might be useful to reset speakers/seat/mic back to that position, I did notice as your earlier refurb thread progresses though that that deep 100-200hz null makes it appearance...so I'll belt up, carry on ;-)
     
  8. ToTo Man

    ToTo Man the band not the dog

    Yes I had them in a more nearfield (just under 2m equilateral triangle) arrangement before, well away from the front wall, so the mid frequencies were a bit smoother as they weren't subject to as many reflections. Once I've tweaked the speaker position, toe-in, first reflection absorption, etc, I'll upload a new 1/12 smoothed measurement of the left and right speakers and we'll be able to compare more reliably to the old measurements on my refurb thread. ;)

    I had a really enjoyable listening session last night at the new listening position (10cm-20cm) further forward than my usual 120cm from the rear wall. Imaging was spookily lifelike on a lot of tracks, e.g. in the intro of the album cut of Chris Rea's Auberge and Road To Hell, I could precisely follow the sounds as they moved across the soundstage. On some tracks the centre image still pulls outward slightly towards the speakers instead of remaining narrow in the centre, but I'm finding this is happening more with vocals that have been processed with reverb, which is common to the anthemic rock genre! Interestingly, no matter what system I play it on, the lead vocal on 'Clarice' from America's eponymous album probably has the strongest phantom centre image I've heard, and its placement is always above the height of the speakers. I'd love to know how they achieved this!
     
  9. cooky1257

    cooky1257 pfm Member

    OK I gotcha, look forward to see how you get on.
    I find the floating centre vocalist's image happens on a lot of recordings over Tannoys-The The Mind Bomb and Christine and the Queens are good examples-that outward tangible projection is one of my favourite attributes of DC's..
     
    ToTo Man likes this.
  10. Tony L

    Tony L Administrator

    Do bare in mind it is usual to double-track rock vocals, either by the vocalist doubling up themselves, or with one or more delay tracks, often panned to some degree to add scale to what otherwise would just be a mono mic feed. I suspect ‘anthemic rock’ would be about as over-processed and layered as it gets in this respect, though it happens in most rock and pop recording. Even jazz, e.g. there’s at least five Norah Joneses on some tracks on her debut album (I class that as jazz as its on Blue Note). If you want ‘honest’ vocal recording you really need to go back to Ella, Nina Simone, Billie Holiday etc or classical. Some early Joni etc too. Pop/rock is almost always people who can’t sing smothered with sufficient outboard FX processing to give the impression they can!
     
    ToTo Man likes this.
  11. ToTo Man

    ToTo Man the band not the dog

    TBH I think I'm also making things worse by consciously fixating on it. My system invariably sounds its best and most holographic late at night, and this isn't due to quieter mains noise etc nonsense, it's because I'm relaxed almost to the point of falling asleep. A similar state of mind could no doubt be obtained earlier in the day with hallucinogenics if I were that way inclined. I'm also a teetotaller so I can't even get a helping hand from a little drop of liquid inebriation!....
     
    RJohan likes this.
  12. Tony L

    Tony L Administrator

    Don’t overlook the closing of curtains and being able to control lighting (or ideally remove it entirely)! Makes a big difference IMHO.
     
    Del monaco likes this.
  13. jobseeker

    jobseeker pfm Member

    I installed remote controlled full multi-colour lighting in my new room, so that I could tweak my ‘psycho-acoustics’ :)
     
  14. ToTo Man

    ToTo Man the band not the dog

    @cooky1257 , Celestion 66 measurement from 2020 (when they were sitting on the floor in front of my Tannoys) -vs- Celestion 66 measurement now when they have been moved back to almost touching the front wall.

    Note the grilles were OFF for the 2020 meaurement but ON for the 2021 measurement, hence the 2020 measurement has a little more and smoother HF output.

    Looks like my Tannoys were helping to absorb some of the 75Hz null!

    2020:
    [​IMG]

    2021:
    [​IMG]
     
    tuga likes this.
  15. cooky1257

    cooky1257 pfm Member

    Wow, not that much in it, which (100-300hz) do you prefer?
     
  16. ToTo Man

    ToTo Man the band not the dog

    It's tough to focus on just one area as since removing the Tannoys from the room the room has become more resonant at low frequencies, so the scoop from 150Hz-300Hz doesn't bother me. My Tannoys had a similar saddle, but I noticed it more on those, probably because they were brighter up top and/or because the room was more damped.

    I'll get a better idea once I add more treatment. The trouble is deciding exactly which treatments would be best as I don't want to waste money on things that aren't optimal. But I won't know if the treatments are going to help unless I buy at least some, since I don't currently have enough of them to experiment with positioning. e.g. If I move my back wall treatments onto my front wall I'm chasing a moving target because I'm changing two variables at the same time!
     
    tuga likes this.
  17. cooky1257

    cooky1257 pfm Member

    Yeah I can appreciate the predicament. Obvs curves wont tell the whole story -only you can assess your place/system so FWIW If it was me I'd leave things as you are in that 2021 graph and concentrate on taming those 2 peaks at 600 and 1khz either with eq or treatment at first reflection and see where that gets me(I'm aware you may well have already tried this!) sound wise.
     
  18. ToTo Man

    ToTo Man the band not the dog

    It would appear that treating the first reflection at the far side of the speaker sorts the peak at 600Hz and treating the first reflection at the near side of the speaker sorts the peak at 1kHz :).

    I wasn't expecting such a drastic change in the upper bass however! It must be because the panel is angled instead of parallel to the wall:

    [​IMG]

    [​IMG]

    [​IMG]
     
  19. cooky1257

    cooky1257 pfm Member

    Oh that's cool-so long as it sounds good like!
     
  20. Si74

    Si74 pfm Member

    Given I have no truck with spikes and my rack, speakers and all my equipment is isolated from the solid floor(and the rack) as much as possible, I find the absorption panels on the ceiling make things very acceptable to my ears with a solid floor. Panels at first reflection points, speaker wall, tri corners, wall to ceiling points and large bass traps behind speakers? no way should my 6ft plus horns and two subs work in a room 4 by 3 mtrs. Funnily enough they do, hence the end of 40 years of box swapping:). Long since gave up trying to persuade people that room correction could save them a fortune. Photos by email to anyone interested enough to prove my point, love to say videos but a bit beyond me after 20 years in telcomms, lol.
     

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