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Room correction advice (Dspeaker Anti-Mode 2.0 with gold phantom)

Discussion in 'audio' started by jamington2004, Jun 21, 2019.

  1. jamington2004

    jamington2004 pfm Member

    Now I have no need or interest in box swapping I have turned my attention to wasting my time on room correction :)

    So I go through a Dspeaker Anti-Mode 2.0 which flattens out a massive peak at about 50hz and a couple of littluns and 80 and 100hz. Really cleaned the sound up and got rid of the horrible ear hurting bloaty bass.

    I also a couple of big dips at 75hz and 115hz which auto correction doesn’t touch. There is an option in the Dspeaker manual called Compensation which talks about lifting / dropping overall bass levels for the compensated ranges. It also talks about lifting dips specifically but I don’t see how and not sure if they don’t do automatically for a good reason?

    “Compensation setting affects the overall bass level throughout the frequency range Anti-Mode calibration was performed on. This setting can also lift (compensate) dips residing in the area”

    Anyone know about dips / cancellations / nulls or whatever they are called? Why they are there - should they be left well alone - any easy tips on what might be causing them so I could try and remedy (not buying bass traps and can’t reposition speakers :) )

    Before I go down the route of attempting to learn about the advanced correction settings / custom PEQ to see what lifting the dips might do

    Hope someone can help explain a little bit more to a novice like me (please use layman’s terms) :)

    Kind regards
  2. Purité Audio

    Purité Audio Trade: Purite Audio

    You have to absorb bass to remove the nulls, adding energy will only make the nulls deeper.
    You may be able to increase output if the dip is caused by for example the room opening out on one side , where one speaker would be receiving more wall reinforcement than the other .
  3. marshanp

    marshanp ellipsis addict

    Please bear in mind that I'm no expert... but I have had an Anti-Mode 2 for a while, have explored its capabilities at some length and would never be without it now.

    As I understand it, filling in dips in the bass is unwise. If they are due to speaker/room interaction, they are likely to become more pronounced if "correction" via DSP is attempted. Pronounced dips are less audible than peaks, so it is to treat peaks that EQ is most worthwhile, although wide/deep dips can also be usefully addressed.

    I let my Anti-Mode decide for itself what to do up to 300Hz, and am perfectly happy with the result. The default "up to 200Hz" setting left me with a hump at ~250Hz, hence my change to 300Hz.

    Having done that, I run an all-frequencies analysis, extract the data to a PC and put it in Excel. I then plot a graph of frequency vs. level: a scatter chart, with data points connected by smoothed lines and data points themselves not shown. I include a line of best fit; by fiddling with the range of frequencies selected, I get this to give me the desired overall downward slope (in my case, -10db between 20Hz and 20kHz - many people will prefer a lesser (~6db) slope, depending on what sort of music they like; I'm a classical music lover with only occasional forays elsewhere).

    The line drawn through the data displayed on the graph enables me to identify peaks in the midrange which might want reducing by EQ. The formula for the line-of-best-fit tells me what the level should be at any given frequency, and thus how much of a cut is needed. The bandwidth of each EQ filter is chosen by close examination of the graph.

    I reduce peaks by only two-thirds; apparently, attempting to EQ for a flat response is unwise. I don't bother to address them at all if the resulting adjustment is less than 1.5dB; in my room this gives me a set of 6 useful EQ filters. The 6 are all set up on profile B, so that the whole set can be switched in and out. They make a positive difference, so they are always "in".

    Profile C has an additional 7th filter (+3dB centred at 1000Hz, bandwidth 1410Hz) which acts as a "presence boost" for those recordings which benefit from it (in my fairly laid-back system), switchable in and out at will. Profile D has a psycho-acoustic dip (-4dB centred at 3000Hz, bandwidth 2120Hz) for those few aggressive recordings which need it. These filters don't get very much use, because they seem to reduce overall clarity somewhat, whereas the set of 6 doesn't. I have no idea why.

    The Up/Down buttons on the remote are allocated to the full spectrum Tilt control; L/R to variable Loudness compensation.

    The Anti-Mode is a wonderfully powerful device.
    Last edited: Jun 21, 2019
    PhilofCas likes this.
  4. jamington2004

    jamington2004 pfm Member

    Thanks Keith appreciate the input. So turning the bass up on those dips will just naturally cancel them out again anyway?

    One speaker is a couple of inches closer to the side wall and it has a wooden door next to it as opposed to just wall on the other side.

    Probably I should just leave well alone and do some of the many chores needed around the house :)

    I am loving the sound anyway - just wondering if I am missing any magic from those frequencies especially with voices.....
  5. Purité Audio

    Purité Audio Trade: Purite Audio

    If the cancellations are room mode based, ( just due to the room’s physical dimensions ) then yes boosting will just increase the depth of the null.
    Perceptually nulls are often ‘heard through’ whereas the big peaks cannot be ignored.
    You can try ‘tuned’ Membrane bass traps , tuned to the specific frequency of the cancellation, subwoofers in a sink/source or just ignore them and enjoy the music.
    Junaman and jamington2004 like this.
  6. jamington2004

    jamington2004 pfm Member

    Wowsers marshandp!! So I think I will leave the dips well alone then as you both concur

    I certainly don’t have the time or desire to go to your level of set up - I think it would drive me insane as to what sounds better or not (like the old graphic equalisers I would be tweaking the whole time if I had one!)

    I did just try an advanced calibration which should also compensate dips I think? but it didn’t touch mine so I guess they aren’t wide enough? (it’s a sharp downward spike on the graph)

    Another question if I may - when I adjust the compensation level from audio settings - it is clearly affecting treble / loudness not just bass which isn’t what it says it should do? IE when I turn it right down you can hear the treble getting louder as well as bass lowering. And when I turn it right up you can the treble fade away?

    My calibration is set to standard range up to 150hz

    My only other quibble is there is no easy way to reduce bass on the easy tone controls - only increase it! Maybe they think I shouldn’t want to - but sometimes would be nice to leave all frequencies the same and just cut bass a bit) :)
  7. marshanp

    marshanp ellipsis addict

    I'm away from home and my manual and notes now, so I'm afraid I can't answer your questions... maybe on Monday.

    My setup procedure sounds like a lot of work, but if you are familiar with Excel it doesn't take long - half a day in my case, and I have felt no need to fiddle with EQ since. The EQ implemented is the outcome of measurement, after all; yet the results are entirely to my liking subjectively, too. I reckon that room and hi-fi system are now about as well matched as they can be, and just get on with enjoying music :)
  8. jamington2004

    jamington2004 pfm Member

    No worries - am enjoying the music after a firmware update which now allows channel balance via optical which is nice bonus :)

    I will reach out to Dspeaker about the compensation thing - doesn’t make sense to me that it affects loudness of mid / treble. I also notice an obvious jump in overall loudness when I switch from profile A which has correction, to Profile B which is factory reset. I would only expect those corrected bass areas to suddenly become louder / quieter when I switch.

    Interesting learning today anyway thanks :)
  9. jamington2004

    jamington2004 pfm Member

    Ok so a bit more fiddling and I noticed headroom gets set to 6db after room correction is applied, as well as the bass Compensation setting set to 6db by default.

    To my ear they both do the same thing when set to 0 - just make everything quite a bit louder (same effect as switching to the profile I just factory reset as mentioned above)

    Also if I get rid of the headroom the unit starts clipping - but as far as I can see I have no boosting in place, only the reduction of the bass peaks on the graph.

    Oh why did I start fiddling - am confused now :)
  10. adamdea

    adamdea You are not a sound quality evaluation device

    It may be counterintuitive but applying any filter (whether boosting or cutting at a particular frequency) is liable to raise the value of at least *some* samples. The sample values are not themselves peaks just voltage amplitudes at fixed intervals. Since the voltage at any given time is the sum of the components at each frequency, and the components may constructively or destructively interfere, reducing the amplitude of one frequency will at various different points in time variously increase or decrease the amplitude of the aggregate of all components. Innit.
  11. jamington2004

    jamington2004 pfm Member

    Ouch. Izzit?
  12. Tw99

    Tw99 source last

    There are a lot of options to use..

    I just let the room correction do it's thing, then use the House curve setting to boost bass below 100hz.

    I'm not sure there's any value in playing with the headroom setting.

    I don't think the manual is very clear about how the compensation setting works. I know it can be changed manually, but does it get set automatically after room correction?
  13. jamington2004

    jamington2004 pfm Member

    Yeah had been leaving it to do it’s RC thing and nothing else till I got the urge to fiddle with something!

    If nothing else I am glad I found out about the channel balance update so I can tweak ab bit depending on where I am sitting :)
  14. Nikola Krivorov

    Nikola Krivorov pfm Member

    I find the DSPmode one of the few very instructive devices in audio, it is not the perfect room correction device, far from it but the first time I heard it I was shocked... For the money it gives one of the very few instant satisfaction effects I have heard. Then I started to wonder why I spent so much (time) when the room is obviously one of the very very bad guys working against us.
    jamington2004 likes this.
  15. Strictly Stereo

    Strictly Stereo Trade: Strictly Stereo

    This happens on other software and hardware-based systems too. It is an artefact of the maths used to apply the filters. Sometimes, even if you are only cutting, the maths will generate an "over" and cause clipping. As long as you are only cutting, 3dB should be plenty of headroom.

    EDIT: Sorry, just re-read your post and noticed that you are using the bass compensation setting. Just increase the headroom until the clipping stops. Alternatively, dial down the compensation instead.
  16. jamington2004

    jamington2004 pfm Member

    Thanks for the extra explanation. Clipping only occurs when I mess about with the headroom and bass compensation settings post Room Correction.

    So i will try just setting headroom at 3db like you suggest. Just feels like I might be restricting things unnecessarily

    But then again if it sounds good - why touch it? That’s why I keep trying to get out of this hifi lark - and even with the phantoms as my only equipment now I am finding excuses to get involved :)
  17. Strictly Stereo

    Strictly Stereo Trade: Strictly Stereo

    I completely missed that you are using bass compensation. Compensation will boost the output, so you need to adjust the headroom accordingly. You might need more than 3dB headroom here. You obviously need more than 0dB if that is causing clipping. I would dial down the compensation instead, but it is really down to your own personal preference. As you say, if it sounds good...
  18. jamington2004

    jamington2004 pfm Member

    Well looking at the graphs it doesn’t seem to be compensating anything. As someone else said earlier - what the compensation setting is for seems a bit unclear.

    Anyway dialling headroom down to 3db seems to have lifted things a bit - but I guess it’s similar to just turning it up a bit?!

    Thanks again - will leave as is for now and try reducing compensation instead one day on a different profile so I can click back and forth at the press of a button and see what the difference is :)
  19. Hipper

    Hipper pfm Member

  20. jamington2004

    jamington2004 pfm Member

    Wrong model for me - I have the Anti-Mode 2.0 dual core

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