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Asking Differently - Setting Sub Delay
#1
Happy new year,

Asking here because Devialet tech support is just the worst, and because I've had a tough time following answers in other threads.  I'm terrible at math.

I have a Dev 120 with a sub card.  My speakers are Raidho X-1's, and a I use a Genesis 928 sub.  The sub sits 2 meters to the right and just behind the right speaker.

How should I measure/calculate/and set the sub delay in the configurator?   From where to where should I measure, and then how do I calculate the delay?  I delay the Raidho's not the sub, right?

If it matters, I run SAM at 0%, and for now, the sub and speakers are crossed over at 80hz.

Thanks for your help.  Devialet engineering has basically said, "this is really hard, don't bother."  Damn I miss my dealer.
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#2
Sound travels at 343 metres per second
So to compensate for the 2 metres distance, it is 2/343 which equates to 0.00582ms
Looking at the Configurator, you can change the delay of the stereo pair by 70 microsecond increments, so you can select 485 or 605 microseconds, save it and see if you can detect a difference
My sub (B&W db1) is 1/2m in front of my stereo pair and I could detect no difference
I think low frequencies are less evident than those above say 250Hz
80Hz sounds right to me. Mine is set the same
                                                           Cape Town - South Africa, the home of good wine
Listening stuff:  Mercury Pi2 / Gentooplayer,  Expert 440PRO CI.  4Tb SSD.  Mogami speaker cable to ET LF8bs, B&W DB1 sub, Power from 7.5kW inverter.  2 x Dachshunds
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#3
(02-Jan-2020, 16:48)chrisc Wrote: Sound travels at 343 metres per second
So to compensate for the 2 metres distance, it is 2/343 which equates to 0.00582ms
Looking at the Configurator, you can change the delay of the stereo pair by 70 microsecond increments, so you can select 485 or 605 microseconds, save it and see if you can detect a difference
My sub (B&W db1) is 1/2m in front of my stereo pair and I could detect no difference
I think low frequencies are less evident than those above say 250Hz
80Hz sounds right to me.  Mine is set the same
Many thanks Chris.  Seem simple enough.  I'll give that a go this weekend.  If folks have other thoughts/comments - they are welcomed.

Baffled that it's taking Devialet a week and counting to answer a question you seemed to clear in under two minutes.
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#4
One reason for adding a delay to the main speaker output is to compensate for the difference in length of the acoustic paths from the sub to the listener and from the main speakers to the listener.  If the sub is behind (further away than) the main speakers, delaying the main speakers compensates for the fact that it takes longer for the sound to arrive from the sub.

From your description I'm not sure whether the 2m is actually the difference in path length as @chrisc has suggested - rather it sounds to me as though some trigonometry is needed.  Would you be able to post a diagram of your set-up with measurements? - it should show the position of both speakers, the sub and the listener.

As well as the difference in the acoustic path length, the delay can also be used to compensate for signal path delays (e.g. due to DSP) in the sub and to match the phase of the sub with the main speakers around the cross-over frequency.  I did quite a bit of reading around this topic when I ran a sub with my previous set of speakers and concluded that there was no "on paper" way to work out the correct delay -- it needs some experimentation and listening, although setting the delay to compensate for differences in the acoustic path length might be a reasonable starting point.

I'll try to dig out the articles I found when I was looking into this, and will post links here if I can unearth them.
Roon (Mac Mini), Wilson Benesch Full Circle, Expert 1000 Pro CI, Kaiser Chiara
Warwickshire, UK
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#5
(02-Jan-2020, 16:48)chrisc Wrote: Sound travels at 343 metres per second
So to compensate for the 2 metres distance, it is 2/343 which equates to 0.00582ms
Looking at the Configurator, you can change the delay of the stereo pair by 70 microsecond increments, so you can select 485 or 605 microseconds, save it and see if you can detect a difference
My sub (B&W db1) is 1/2m in front of my stereo pair and I could detect no difference
I think low frequencies are less evident than those above say 250Hz
80Hz sounds right to me.  Mine is set the same
To avoid confusion: I think you meant to say 5.83 ms, that's to say 0.00583 s.
Roon (Mac Mini), Wilson Benesch Full Circle, Expert 1000 Pro CI, Kaiser Chiara
Warwickshire, UK
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#6
As promised, here are some articles I found helpful when setting up my sub-woofer:
There's quite a bit to absorb in that lot...
Roon (Mac Mini), Wilson Benesch Full Circle, Expert 1000 Pro CI, Kaiser Chiara
Warwickshire, UK
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#7
To add to what @thumb5 said:

1) the delay is always added to the closer speaker. Your sub is further away than your speaker so in your case the delay is added to your speaker to stop the sound from it arriving before the sound from the sub. In @chrisc's case his sub is in front of his speakers so the sound from it arrives first. Normally that would mean that you would add a delay to the sub but he said he could detect no difference in arrival times. That could be because of the electronic delay the sub adds (see my point 3 below). because of the fact that the sound from the speaker had to bend around the sub (see point 2 below), or a combination of both.

2)you need to actually measure the difference in distance from your ears to the speakers and to the sub. The difference in distance is then calculated by subtracting speaker distance from sub distance since the sub is the most distant speaker. The result you get will be different from 2 metres. If you can't see the sub from your listening position because the sub is hidden by the right speaker then the distance may be a little longer because the sound can't travel in a straight line from sub to you and will have to diffract (bend) around the speaker. If you need to specify a time delay in the configurator then a rough guide to the calculation is 1 ms per foot distance. If you need to be more accurate than that then there's lots of online calculators for doing a more precise calculation.

3) the electronics in a sub (the amp, the phase control, and so on) actually delay the sound from the amp reaching the driver. That kind of circuitry isn't present in the signal parts from amp to speaker. It makes a small difference and, from what I've read on an AV forum about the Audyssey room correction system (I have a separate HT setup in a different room which uses Audyssey) it seems that the extra delay added by the sub's electronics is usually around 3 ms so you may need to add 3ms to the time delay you calculate or 3' to the distance as a starting estimate and to perhaps decrease that by 1 ms or feet depending on how you enter the figure, or increase it by 1 to 2 ms/ft in order to get it correct.

As @thumb5 said, there is no "on paper" way of calculating the correct delay. You need a combination of physical measurements and a bit of adjustment to compensate for differences in the travel path of the sound if it can't get to you without bending around a speaker and also for the fact that the circuitry in most subs imposes an additional small delay of its own.
Roon Nucleus+, Devilalet Expert 140 Pro CI, Focal Sopra 2, PS Audio P12, Keces P8 LPS, Uptone Audio EtherREGEN with optical fibre link to my router, Shunyata Alpha NR and Sigma NR power cables, Shunyata Sigma ethernet cables, Shunyata Alpha V2 speaker cables, Grand Prix Audio Monaco rack, RealTRAPS acoustic treatment.

Brisbane, Qld, Australia
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#8
Y'all are great - will read all of this carefully and try some things out.  Deeply appreciated.
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#9
As already said, it's not enough just to measure the distance - the DSP in subwoofer(s) adds some delay.
The best way is to experiment and measure (REW, XTZ Room Analyzer...) the frequency response - to achieve the best integration in the crossover area.
E.g., for SVS subwoofers (in my case dual SB16-Ultra) I need to add additional 2 ms to compensate the DSP.
Devialet Expert 440 Pro | Dynaudio Confidence 50 | 2x SVS SB16-Ultra
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#10
Thanks everybody for the help and encouragement. After some playing around I’ve landed on a 10 ms delay. Using that in combination with rolling off my main speakers at 90 Hz and the subwoofer at 75 Hz seems to result in the most even, and really surprisingly dimensional, sound in my room.

FWIW - Still no response or guidance from Devialet. I even tried calling their flag ship store in New York, and nobody there was able to help either.
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