EQ Dual subs

Discussion in 'Subwoofers' started by Bone9, May 28, 2019.

  1. Bone9

    Bone9
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    Right I've got myself another monolith plus :devil:

    I've yet to run Audyssey and just set it up quickly with the miniDSP 2x4hd. I now want to set it all up again to get the best result from the combined subs.

    Should I eq both subs individually or as one? I only have xt so that only sees one sub.

    Should I adjust the delay on the closer sub to get the best looking response before I eq?

    My plan is...

    1, Turn off audyssey and set the miniDSP to bypass.
    2, Run some sweeps in REW. Indvidual and combined.
    3, EQ as one with the miniDSP to flat.
    4, Run Audyssey.
    5, More sweeps and fine tune with miniDSP to flat.
    6, Add house curve.
    7, Adjust gain to preference and have a listen.
    8, If happy with the sound run compression tests to find out the headroom.

    What do you think?

    Cheers. :)
     
    Last edited: May 30, 2019
  2. D1gita1

    D1gita1
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    Auto eq will only ever apply eq as one. Start with no eq applied by the mini dsp.

    Manually set the subs up. If their positions are fixed then proceed with setup. Gain match them at the mlp using an spl meter and the gain dials on the subs. Run REW and measure each sub individually at 75 dB. Then run the subs combined but check the individual subs still read out at 75 dB each. Combined you should see about 6dB increase in output which will give you your first indication of their interaction.

    Run the combined sweep and overlay the graphs. The overlay will indicate where the subs negatively and positively interact with each other. If you see any sharp dips that will be a cancellation. You can play with the variable phase of one sub running graphs after each change if you want to learn about how phase affects response.

    If the combined response is pretty clean, by which I mean no major dips, then I'd use the combined response as your basis for any eq. If you can use less eq that is generally better, but feel free to experiment. I'd run just audyssey at that point and see what it gives you. Curiosity will then get the better of you, so turn audyssey back off, apply your REW filters into the mini DSP and see what that's like, the run Audyssey over that to see what that final result is like.

    If you have enthusiasm for running REW there's plenty to go at and play with. You want the subs to be in time with each other above all else, so being less aggressive with eq will help with that, and make sure Audyssey is always run last. If youre so inclined, run a massive delay on one sub to experience what out of time subs sound like, and make sure you stay as far away from that as possible.

    I'll keep an eye out for a post with a 1000 graphs :rotfl:
     
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  3. Bone9

    Bone9
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    That is a great help! Thank you :)

    When I was experimenting earlier I found the phase knob acted very similar if not the same as adjusting the distance of one sub. So all I did was leave the phase set to 0 on both subs but added a delay to the closest sub buy 1 second. One sub is 34cm closer that the other.

    For fun I added an 8 sec delay on the closest sub so I now no how its not supposed to sound :rotfl:

    Should I gain match the subs after eq as well as before?

    Prepare yourself for incoming graphs!! :smashin:
     
  4. D1gita1

    D1gita1
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    You shouldnt need to gain match both subs after eq as you will have a single eq acting on both subs, and their outputs should remain online with each other. If you apply eq to each sub individually using the mini dsp, then gain match them again before running audyssey.

    Phase is a function of timing. Delays and distance settings also work in the time domain. Time is everything in audio.
     
    Last edited: May 29, 2019
  5. DodgeTheViper

    DodgeTheViper
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    @D1gita1

    I may ask you at some point if you could check mine over. Your opinion and advice would be most welcome ;)
     
  6. D1gita1

    D1gita1
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    I moved from Manchester to Leeds, so it's quite the drive now, but you probably know Ive always been a sucker for looking at a fresh set up, my travelling days aren't quite over just yet. Im not sure you need any advice or I'd have any of use to offer, but assuming you're still running Arendals, I think you can probably guess my opinion :smashin:
     
  7. DodgeTheViper

    DodgeTheViper
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    Kind words, thank you. So maybe you would just fancy a good old fashion demo at some point in time ;)
     
  8. Bone9

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    Hoping to get on this tonight. Should I level match my subs or gain match them?
     
  9. D1gita1

    D1gita1
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    Not sure how you've got on, but initially I would keep the trim levels at zero and gain match them to 75 dB each at the mlp. Obviously only setting one sub at a time, then when both are set, run the test tone with both subs running and you should get around 81dB total combined output.
     
  10. Bone9

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    Right Aud is off, no eq with the minidsp. Gain matched subs at mlp. Rew sweeps run individually and combined. Showed a 6db gain.

    See graph.

    Dual Subs No EQ.jpg
     
  11. Bone9

    Bone9
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    I've also had a play with the phase on one sub and this is the best I can get. Will now run audyssey before and after EQ to do a comparison.

    All of this is done with a door open otherwise I lose all my low end. Audyssey is done with the door closed but then opened after to get the best results. I've tried both ways and this works out best.
     
  12. Bone9

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    This graph is Audyssey only with no eq from the miniDSP. I'll now turn Audyssey off and EQ with the miniDSP and re run Audyssey to compare.

    Dual Subs Audyssey Only.jpg
     
  13. Bone9

    Bone9
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    Right this is Audyssey first then eq'd after with the miniDSP...

    Dual Aud first then miniDSP.jpg
     
  14. D1gita1

    D1gita1
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    Did you eq with mini dsp with no audyssey applied, then finish off with Audyssey? I personally would run Aydyssey last otherwise its filters will be changed by the mini dsp which will cause smearing in the time domain that your spl graph won't show. The final graph does look very good however if your goal is a flat response. You can see the 80hz dip caused by the room but if you run a sweep that includes the speakers you may well find the speakers clean that up. Overall though I'd say the process has done a good job. You can see in your first graph how each subs weakness is covered by the others strength, a d besides your 80hz room problem, your ending up with only peaks to deal with. Eq is can deal with these peaks easily by reducing the energy in the signal, hence the very good looking end result.

    If you apply 1/3 smoothing to your final graph, it's claimed this would be more indicative of your ears true sensitivity as sub bass frequencies.if you find 80Db is to high, then you can trim the sub levels in the AVR, but just ensure you do them equally. You can see the eq hasn't lost much output in the process either, so that's also good.
     
  15. Bone9

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    This is Audyssey first then miniDSP second in blue. In red is Audyssey off and EQ'd with only the miniDSP. I'll now run Audyssey to see what it does with it.

    Dual, Aud and minidsp comparrison.jpg
     
  16. Bone9

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    That was Audyssey first then EQ'd with the miniDSP after. Im now doing miniDSP first then Audyssey last to see the difference. What does smearing in the time domain mean?

    I intend to add a house curve last after I have a flat response. I'm used to a flat response but believe a house curve would be best?

    Every sweep I adjusted the volume to bring them all back in line so the EQ did lose a fair bit.
     
  17. Bone9

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    My denon sets my speakers to 70db after calibration and I set my subs to 80db. I like it hot ;)
     
  18. Bone9

    Bone9
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    Hmmmm this is not good. (Green) This was EQ'd with miniDSP first then ran Audyssey. (Blue) Also here is the other way round Aud first then miniDSP.

    Dual miniDSP First then Audyssey.jpg
     
    Last edited: May 31, 2019
  19. Bone9

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  20. Ringnut

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    Personally I'd listen to both on a track you know very well that contains good bass and see which you prefer. I suspect blue would sound better, but D1gita1 has given you some good advice I think.
     
  21. Bone9

    Bone9
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    Yes very good advice, he's been a fantastic help!

    Blue to me looks better and cuts less of the sub output. I'm just concerned about smearing the time domain. Been trying to find out how to check if I am or not.
     
  22. D1gita1

    D1gita1
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    Audyssey tries to ensure its corrections remain accurate in the time domain as well as achieving a flat response. If you run eq after Aydyssey youre changing the environment Audyssey worked with when applying eq and likely negatively impacting things in the time domain.

    Timing is important as this is what keeps all your speakers and subs in phase for seamless integration and the most dynamic playback that can be aggressive and subtle at the same time. Audyssey always aims for a flat response so there's no getting around that unless you apply eq after you have run audyssey, or have the audyssey app available to you. The simple choice at this point is to go with what you like the sound of the best. My advice over the years has always been to aim for a flat and accurate response initially, and if you're not entirely happy, tune it to your preference favouring it over reference. Reference is good, but if you're not enjoying it as much then it's a minor point.

    My preference has always been to use high quality subwoofers, use at least 2, use sealed subs, eq flat in room at the mlp, then to run the subwoofers 3db or so hot. The cleaner the bass the hotter you can run them without it becoming offensive. I'm a bass nut but I'll sacrifice bass every time if it's not clean bass.

    A house curve is fine if that's what your after, but that tends to be a US trend and they like bass that's a little different to us in the UK in my experience. By all means experiment, but before you do, I would run with the flat result, put a couple dB on each sub trim and run the bass a little hotter and see what you make of that. That 80Hz dip is going to play its part but you may have to live with that. Did you run a full sweep with the speakers as well so you could observe the frequency response upto around 250Hz once the speakers are in play as well?
     
  23. Bone9

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    Thanks mate. Is there a way to check the time domain is ok?

    I could buy the app if its any good? Reviews suggest its not.

    I've always ran flat but this time i thought i'd try it with a house curve to see if i like it or not. Only thing is it would be applied after the audyssey eq.

    My avr shows only 1 sub trim so it will adjust both equally.

    I did a quick run with the mains enabled and it sorted that dip but i didn't save it. I'll do another once I'm happy with the response.
     
  24. D1gita1

    D1gita1
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    Time domain is whole other subject, but essentially you want to keep distortion low, group delay low, and keep your waterfall graphs in check. Eq filters add in their own processing delay to varying degrees depending on the type of filter used and how it's deployed. The filter effects are cumulative and they interact with each other, so stacking more and more filters inevitably leads to the potential to overly complicate things and add tiny time delays where the filters work and interact. These effects are typically very very small, certainly its way better to 'suffer' these effects in place of massive negative room modes, but if you go too far all those little delays add up and instead of detailed and textured bass, it begins to smear into more of a one note bass with no detail. Think of it like a large number of overlayed images projected onto a surface (imagine 120 images representing each frequency in the LFE range) , if they're all exactly aligned you have a bright crisp sharp image, if some of them move out of alignment however, the image smears and blurs and will lose all its detail, and it's this affect you want to avoid. That's why cheap subs sound like monotone bass and expensive subwoofers integrate and extract detail in a far better way, because the amplifier and driver combo tracks the signals so much better and stays accurate in the time domain. Remember, frequency itself is a function of time.

    If you want to try a house curve then go for it, if you like how that sounds then that's all that really matters. I personally have never used the Audyssey app, I moved away from Audyssey before it was ever released and to be honest I'd probably stick with what you have.
     
  25. Bone9

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    Thank you for a great explanation. I think I'll try running audyssey again to see if I get a different result. One thing though, how will Audyssey know where I've already added filters via the miniDSP and to know not to stack more on top of what I've already done? Surely thats the same for me If I EQ after Audyssey?
     
  26. Ringnut

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    I concur with what D1gita1 has been saying here.

    Re house curves, I have experimented with various degrees of house curve in the past but always come back to flat for the very reasons eloquently explained by D1igita1 above.

    My own reasoning is this. When a sound engineer creates the sound track for a film they already put into that track a ‘house curve’ (for want of a better name) to take into account that our hearing response deteriorates as the frequency drops. By having a flat response it means that you are faithfully following what the sound engineer intended.

    Adding your own second ‘house curve’ doubles up on that and not only reduces headroom but clouds the critical mid-range IMHO.

    I suspect that the reason many feel the need to add their own ‘house curve’ is due to the fact that many films are more and more increasingly filtered below a certain point, some from as high as 50hz and they need some extra low end boost. The problem with a ‘house curve’ is that it is too broad a sword and you end up boosting some films that haven’t been filtered.

    A far better way in my opinion is to make use of Bass EQ

    Bass EQ for Filtered Movies - AVS Forum | Home Theater Discussions And Reviews

    This restores the missing filtered bass individually according to need, so a film like WOTW gets very little extra boost

    Bass EQ for Filtered Movies - Page 135 - AVS Forum | Home Theater Discussions And Reviews

    whereas something like First Man gets a massive 48db of extra boost at 25hz! :eek:

    Bass EQ for Filtered Movies - Page 111 - AVS Forum | Home Theater Discussions And Reviews

    The difference it makes to First Man is the difference between having the subwoofer on for one and off for the other!

    As you can see from the graph all Bass EQ is actually doing is extending that ‘house curve’ from where it starts dropping off at around 50hz down to where it should be down into the single digits. :)
     
  27. Bone9

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    I have actually been following that thread and been enjoying beq for a while now just herd people on there use a house curve as well as. Just though I'd give it a try. Hopefully I can get a proper flat response from audyssey after my eq being done first.
     
  28. Ringnut

    Ringnut
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    Yes, but I guess the reason for that is that rooms in the US are generally open plan and far larger! :)
     
  29. Bone9

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    Very good point, my rooms tiny!
     
  30. Ringnut

    Ringnut
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    It looks to me like you've already acheived that. :)
     

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