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Upgrading my acoustical room treatments

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

  1. rag987

    rag987 pfm Member

    Yes good point. My room is for audio and home-theatre, so I actually have 2 options for seating. Primary single seat for music, as above. And secondary seats in the back of the room when watching something with more people. I have tried not to compromise too much for music listening, and more compromises for home theatre seats. Luckily my pre-processor has some flexibilty to set speaker parameters per input.
     
    RJohan likes this.
  2. Riotvan

    Riotvan Snoofer in the Woofer

    Maybe try moving the speakers a bit closer together? A dip in the midbass can sometimes be alleviated with that.
     
  3. ToTo Man

    ToTo Man the band not the dog

    I've spent the last week having my arse handed to me over on Gearspace :eek::Dover. I don't have the energy to summarise what's being discussed on my thread over there but if your interested you can head over and have a look-see.

    Something that maybe of interest to the pfm community is the effect of simply placing two 600mm x 1200mm x 170mm broadband bass absorbers on the back wall, centred behind my listening seat. This changes the perceived tonality of my speakers significantly, making them sound both bassier and at the same time brighter. Output from 70Hz-120Hz increases (confirmed by the measurements) and the midrange output is less prominent (not confirmed by the measurements but I'm trusting my ears on this one!).

    This necessitated some adjustments to my EQ to restore the speakers' tonality to what I had previously, and I'll have to keep this in mind when planning my room treatments because the more broadband absorption you add, the more you increase the ratio of direct-to-reflected sound and the more you are tuning the response at the LP to the speaker's anechoic response (at MF and HF at least).

    The increased bass might be welcome as it may allow me to pull the speakers away from the walls to improve their imaging without losing too much bass reinforcement. I've still to try this.

    I'd noted previous in another thread that placing a 600mm x 1200m x 170mm absorber behind my listening seat helped to reduce the deepness of a 75Hz null caused by SBIR. The improvement was small when the absorber was mounted on the wall but improved significantly when I pulled the panel forward by 60cm so that it was halfway between the wall and the back of my chair.

    This time I measured the effect with two absorbers instead of one, and raised up off the floor by 40cm so that the centres of the panels were now at ear height. Placing the absorbers against the wall reduced the 75Hz null by 3.5dB, a small but audible improvement. Pulling them 60cm out from the wall shaved an impressive 7.5dB off the null (the change was measured without applying any smoothing to the graphs, that's why it doesn't look as impressive on the graph below with 1/12 oct smoothing applied).

    Of course, having two big monoliths standing 60cm off the wall isn't exactly practical, it also cuts out a ton of daylight from my room, but it was an interesting experiment. If I'm serious about going after this SBIR then a more practical choice may be to use the "FlexRange" version of the Monster trap which is tuned to 80Hz and designed to work best against the wall.

    Here's the FR before & after adding the two absorbers behind the LP without adding any EQ:
    [​IMG]
     
    Last edited: Sep 25, 2021
  4. Tony L

    Tony L Administrator

    Fascinating threads both here and on Gearspace. I’ve nothing constructive or otherwise to add regarding commercial treatments, I know nothing about them, but I would be very interested to know what changes if you shift the listening position around a bit both from a subjective and measurement perspective. It would be interesting to see both substantially back and substantially forward (i.e. try both far field and nearfield).

    I’m in kind of a similar position in the upstairs system due to the confines of it being a storage area (pfm record shop) that needs space and access, so the speakers are quite close to the wall and the listening seat just a little forward from the middle of the room. It results in amazing clarity and imaging, but as you’ve seen from my 149 and LS3/5A measurements I sacrifice low bass as there is little reinforcement here, in fact I’m likely in a null. It is very clean and agile though! If I move the beanbag back I lose the amazing imaging and detail, but gain bass.

    Given your room is square, and therefore very hard to work with, I’d suggest trying everything possible no matter how crazy. Maybe even try setting the room up as a ‘diamond’, or slightly skewed variation on that as that way you can get first reflections to miss the listening seat to a large degree. It would look daft, but would be interesting to see what effect it had.
     
  5. graystoke4

    graystoke4 pfm Member

    Hi, I've ordered Two Polka Sound Diffuser Proof Panels from SKS Acoustics Ltd - Foam, a couple of weeks ago, £65, had to wait, as the owner/maker went down with covid, will get them next week, not because i have a problem room, Scattering range: 800Hz to 3'000Hz;Dimensions: (850x550x53mm);, but they can't do any harm, and at that price i could always move them on, but because i can't upgrade anymore, due to price, maybe cables, :rolleyes:, i have paintings and pictures on the walls, and the room is dead but not overly dead, will put these on the wall at first reflections, this does seem like an ongoing tread/threads, i saw a thread last week the guy spent more on room acoustics than the system, well that what it looked like, the room was not to my taste, but i don't have to live their, also i do have a dedicated music room, will try to find the photo's of this guy's room,
     
  6. ToTo Man

    ToTo Man the band not the dog

    A diagonal arrangement is something I'm considering, but it's messing with my head as I'm used to working in symmetry! I'm most likely going to rotate my room 90 degrees so that the window wall becomes the new left side wall. This will make the room feel bigger and give me more freedom to pull the speakers out from the wall, and will also enable me to max out the number of bass traps I can put behind me. I then may be able to get away with just a single broadband absorber on each side wall and therefore not obscure the window too much. I am however going to take measurements with the speakers moved over onto that wall before I go humping furniture around, just in case the response is horrible (I seem to recall seeing a pretty nasty SBIR dip in the bass when I had my JR150s set up on that wall but don't remember what my listening distance was).

    I'm not really able to listen 'nearfield' to the Dittons due to the tall vertical driver spacing which causes lobing in the FR if you sit too close. I imagine Celestion had much longer rooms than 4 metres in mind when they designed these! 2 metres is about as close as I can get before weird things start to happen at the crossover frequency when I change the height of my seating position.

    EDIT - If I move my listening seat back 20cm so that it's 1m from the back wall (which is where I sat for years), the 75Hz SBIR null gets a lot worse (the D# is missing from the bass guitar!). Further back than that and the low end gets pretty bumpy. See these measurements.

    The trouble with Gearspace is they are very uncompromising when it comes to treatments as a lot of the contributors are professional installers. I think they sometimes forget that my goal isn't to make my room accurate for mixing/mastering, simply enjoyable for replay, which it already is (to my ears anyway!). I'm just looking to get my strong centre image back without losing too much bottom end, - a quest that's possibly going to result in re-jigging the entire space! A re-jig might just be what I need though from a psychological POV as my room has remained unchanged for the last 8 years and I'm growing tired of the current set of compromises dictated by the position of the door and window. If I had a magic wand I'd reposition the door and window to be central on each wall, then the door wouldn't dictate placement of the speakers and I'd be able to throw bigger bass traps in the corners (the ones I have at the moment are 'toys' apparently! :rolleyes:), and the reflections off the window wall would be symmetrical and easier to treat.

    To end on a positive note, at least I don't have to share this room with anyone else so the acoustic treatments can be as ugly as required! :D
     
    Big Tabs likes this.
  7. graystoke4

    graystoke4 pfm Member

    will post the photos over the weekend,
     
    ToTo Man likes this.
  8. Old Shatterhand

    Old Shatterhand pfm Member

  9. Tony L

    Tony L Administrator

    Likewise, it would trigger the hell out of me, but I’d probably try it as an experiment just to see what happened. Someone (Simon/Tenson IIRC) suggested it to me when I was struggling to get the MEGs not to boom, but I never tried it as there was just so much crap to lump around and I know I’d not have been able to put up with the room like that aesthetically!

    That makes a lot of sense, I was on the verge of suggesting it, though I couldn’t figure out if the cupboard was going to be an issue. If your speaker cable is long enough I’d be inclined to leave the system itself where it is and just move the speakers, that way you’d have more options to play with distance from the rear wall/corners etc. Corner horns aside I’ve always found getting the speakers well away from corners to be a huge advantage. Then just balance bass balance from the rear wall. I’d never deliberately try to use a side wall for reinforcement.

    I’d totally forgotten that! So used to point source and little ‘uns! I guess a lot depends how wide they run the mid dome, if that’s doing much of the work you could likely get about 2m to them without it being terribly obvious. I ended up crazy close to my Bricks in That London for a while. Fun, but obviously wrong.
     
  10. ToTo Man

    ToTo Man the band not the dog

    Well it's the deepest panel absorber that GIK make, so I don't really have much choice unless I go the DIY route! ;)

    They do a 413mm deep Soffit trap designed for wall-wall and wall-ceiling corners, but I'm not sure if I'd want to cover up the attractive 120 year old plaster cornice on my ceiling! :(
     
  11. ToTo Man

    ToTo Man the band not the dog

    The cupboard hasn't been a cupboard since I put GIK corner traps in front of its door in 2013! :D It's currently empty but I wonder if I'd get any benefit from stuffing it with broadband absorption, or if this would only be of benefit if I removed the door so that the sound waves can get through to it?

    Wouldn't the hifi rack affect imaging by messing with the side wall reflection? The rack is 115cm high so it's quite a big acoustic obstacle. Plus I'm not sure how easy it would be to mount the TV (which currently sits on top of my hifi rack) on the other wall because there's a chimney behind the plaster which may prevent a secure mounting. The joys of old houses, eh?! :)

    I will at some point be replacing my existing hifi rack, probably with a couple of coffee tables or benches stacked on top of each other, so that I can finally push my Yamaha amp all the way in and not worry about a lack of ventilation.
     
  12. Riotvan

    Riotvan Snoofer in the Woofer

    Honestly as you mentioned earlier the 4 subs might be an option. Get the best position for your speakers/chair from 80hz-90hz and up and have the subs handle the rest with a proper crossover in place. Like Grimani recommended. Can also try this with just the two you have. I have two 10” xls200’s and it’s flat down to 25hz at the seat. They are both in mono.

    I do agree though with the gearspace thread that you need to sort the side reflections as well as toe in and distance between the speakers.
     
    ToTo Man likes this.
  13. Tony L

    Tony L Administrator

    I’m 40 years or so behind with room treatment so I’d just call it a diffuser in a ‘live end/dead end’ scenario! I try only to live in places with good sounding rooms to start with, so treatment is much less an issue. I aim for a rectangular room as close to the ‘golden ratio’ as I can find and then fire the system across it. I’ve learned how to get that to work to my taste just using normal furnishing and my record collection, books, art etc.

    I always set the system up to the side of the room whenever I can. As much as anything as I hate having any lights between the speakers as I like listening in the dark now and again (removing the visual aspect is the best free hi-fi upgrade ever!). The upstairs rig is a compromise due to space, I just can’t do it up there and keep the record shop storage functionality.
     
  14. Frizzy

    Frizzy Liberal anarchist

    Cool thread, I use gks tri traps , 242, and diffusers. Saving up for stillpoint aperture panels.
    I got the boenicke w8se as even tho they require oodles of free space (17ft by 12ft, 9ft ceiling) they seem to be less affected by the room than my obx rw or esl57.
    I think I should remove treatments (were in place before new speakers) have a fresh listen and see\hear if they are needed as is.
    I feel rack in between speakers is audio suicide, sorry.
     
  15. ToTo Man

    ToTo Man the band not the dog

    I experimented a little tonight with speaker positioning, moving them forward so that the baffles are now in-line with the front of my hifi rack, and moving them away from the side walls as far as possible (1.03m measured from side wall to middle of speaker), which places them 2.1m apart instead of 2.85m. This now means the speakers are closer to each other than they are to my listening seat, i.e. the opposite of what I had before. 1.03m happens to be exactly a quarter of my room's width, which is an in advisable place to put a speaker, but I thought I'd try it anyway. To keep things simple I didn't toe-in, the speakers are firing straight towards the back wall (hence the steeper HF rolloff). I now have a much louder centre image that's more 'forward' in its placement. The effect is noticeable on both music and TV dialogue. I am also passing more of the imaging tests I linked to on the previous page. Unfortunately the bass has taken a hit, I now have a huge broad peak around 200Hz where there was previously a null. This starts to grate pretty quickly so needs addressing, which with some more tweaking of positioning and toe-in I think I'll be able to ameliorate. It's surprising how different the speakers sound by moving them a relatively small amount, - it highlights just what a huge impact a small room has on a speaker's voicing.

    [​IMG]
     
    tuga likes this.
  16. Old Shatterhand

    Old Shatterhand pfm Member

    In short, there is no way to avoid every peak and dip. You fill in dips and get new peaks or you lower peaks and get new dips. With different positions you only shift the frequencies where this happens.

    The guy from GIK told me that even in properly treated studios you still have some +-6dB peaks and dips in the lower bass frequencies. Your result now looks much better. If you place the right absorbers on the back wall you maybe can lower the peak around 200Hz a bit.
     
  17. Tony L

    Tony L Administrator

    What happens if you push them back hard against the wall where they now are? To my understanding the Ditton 66 (like the rest of the Ditton range) is a wall proximity speaker, I’d expect just getting them well out of the corners to make a huge difference. Don’t worry about imaging/dispersion/diffraction etc at this stage, the equipment rack can be moved elsewhere in the room if need be. I’ll be interested to see what happens to the 150Hz null/210Hz peak. I have a feeling the dip might fill out, though not sure about the peak.
     
  18. Old Shatterhand

    Old Shatterhand pfm Member

    I guess the dip is the first reflexion of the floor.
     
  19. ToTo Man

    ToTo Man the band not the dog

    The dip @ 130Hz becomes much deeper when the speakers are measured in stereo:

    [​IMG]

    I'll experiment with positioning to see what's causing it.
     
  20. cooky1257

    cooky1257 pfm Member

    One thing it looks like you haven’t tried is seat height, mic height, imho it’d be worth a quick look at the effect it has ...
     
    ToTo Man likes this.

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