miniDSP 2x4 "delay" problem? - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 8 Old 07-10-2019, 06:31 PM - Thread Starter
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miniDSP 2x4 "delay" problem?

I am looking to integrate a miniDSP 2x4 into my system to act as an advanced low-pass filter for my subwoofers. Right now I'm just using a pair of simple 70hz FMOD low-pass crossovers in front of my subwoofer amp to do the job, but the results are barely adequate and offer me no advanced control of the crossover slope, etc.

Ideally I would like to put the miniDSP 2x4 in the same spot the FMODs are now, right before the inputs of my subwoofer amp, and not touch anything else. The potential problem is that anything going through the miniDSP 2x4 goes through an ADC -> DAC conversion (because processing is done digitally) and this results in an added delay of 1.2-2.5ms depending on what sort of processing is being done.

This delay is not an "issue" in most cases because, as far as I can tell, in all of their guides they show the main speakers being run through the miniDSP 2x4 also, even if no processing is being done on the main speakers. This would subject the main speakers to the same delay. An example from one of their guides:




Unfortunately, I could not setup my system like this even if I wanted to. My Yamaha C-80 preamp has 2 sets of pre-outs, one normal and one inverted, and I use this to run 6 amps total, 4 bridged and 2 in stereo (one of those stereo amps being the amp that powers my subwoofers). This is beyond the scope of what I could run through the miniDSP. I'm also not sure that subjecting all of my mains to an unnecessary ADC -> DAC conversion would be something that I would want to do anyway. I would like everything other than my subwoofer amp to remain directly connected to my preamp, bypassing the miniDSP.

So now, down to the real question. What is this 1.2-2.5ms delay going to do for me? If my subwoofers are 1.2-2.5ms behind my mains, is that even going to be noticeable? Does this sound like a deal-breaker so to speak?
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post #2 of 8 Old 07-11-2019, 10:59 AM
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Quote:
Originally Posted by GotNoRice View Post
I am looking to integrate a miniDSP 2x4 into my system to act as an advanced low-pass filter for my subwoofers. Right now I'm just using a pair of simple 70hz FMOD low-pass crossovers in front of my subwoofer amp to do the job, but the results are barely adequate and offer me no advanced control of the crossover slope, etc.

Ideally I would like to put the miniDSP 2x4 in the same spot the FMODs are now, right before the inputs of my subwoofer amp, and not touch anything else. The potential problem is that anything going through the miniDSP 2x4 goes through an ADC -> DAC conversion (because processing is done digitally) and this results in an added delay of 1.2-2.5ms depending on what sort of processing is being done.

This delay is not an "issue" in most cases because, as far as I can tell, in all of their guides they show the main speakers being run through the miniDSP 2x4 also, even if no processing is being done on the main speakers. This would subject the main speakers to the same delay. An example from one of their guides:




Unfortunately, I could not setup my system like this even if I wanted to. My Yamaha C-80 preamp has 2 sets of pre-outs, one normal and one inverted, and I use this to run 6 amps total, 4 bridged and 2 in stereo (one of those stereo amps being the amp that powers my subwoofers). This is beyond the scope of what I could run through the miniDSP. I'm also not sure that subjecting all of my mains to an unnecessary ADC -> DAC conversion would be something that I would want to do anyway. I would like everything other than my subwoofer amp to remain directly connected to my preamp, bypassing the miniDSP.

So now, down to the real question. What is this 1.2-2.5ms delay going to do for me? If my subwoofers are 1.2-2.5ms behind my mains, is that even going to be noticeable? Does this sound like a deal-breaker so to speak?
This may not be of any value but in my secondary "mostly for music" system which is 2.2, (and quasi 3.2 with the center in bridged mono the few times I use it), I use the base MiniDSP 2x4 as a crossover/EQ for my subs using the preouts and main ins of my NAD 7250PE stereo receiver from the 1980s.

It works like a charm but of course the MiniDSP is also sending signal to the front left and right so I don't have the possible "delay" issue.

I will say that the sound, despite the analog to digital to analog gymnastics (which many abhor on theoretical grounds) is fantastic; far better than the piece of junk Rolls analog crossover I was using before.

Using a Umik and REW I was able to EQ my two teeny little Yamaha subs using the parametric EQ function which made them "disappear" more from a frequency response standpoint if that makes any sense.

Geoff A. J., California
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post #3 of 8 Old 07-11-2019, 04:32 PM
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Like lip sync problems with video, having one signal take one route and the second a different route (and the routes aren't the same length and no mechanism to re-sync the signals), well, you get what you are getting. I could only suggest you try near-field placement of the subs to minimize the delay, using physical distance to try to sync up the sound. If the subs are closer, the sound will get there earlier.

Sorry, that's all I got.

It's a VIRTUAL channel unless stated otherwise.

Last edited by RayGuy; 07-11-2019 at 04:35 PM.
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post #4 of 8 Old 07-11-2019, 05:42 PM
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Quote:
Originally Posted by GotNoRice View Post
Unfortunately, I could not setup my system like this even if I wanted to. My Yamaha C-80 preamp has 2 sets of pre-outs, one normal and one inverted, and I use this to run 6 amps total, 4 bridged and 2 in stereo (one of those stereo amps being the amp that powers my subwoofers). This is beyond the scope of what I could run through the miniDSP. I'm also not sure that subjecting all of my mains to an unnecessary ADC -> DAC conversion would be something that I would want to do anyway. I would like everything other than my subwoofer amp to remain directly connected to my preamp, bypassing the miniDSP.

How are the 6 amps wired to the preamp today? Daisy-chaining RCAs?

Quote:
Originally Posted by GotNoRice View Post
So now, down to the real question. What is this 1.2-2.5ms delay going to do for me? If my subwoofers are 1.2-2.5ms behind my mains, is that even going to be noticeable? Does this sound like a deal-breaker so to speak?

Yeah, introducing delay on one channel sounds like a bad idea. It's within the bounds of which a trained listener might notice it. I found this info on another forum:


Quote:
How finely can we divide our little 3-second lives? The shortest perceivable time division – sensory psychologists call it the fusion threshold – is between 2 and 30 milliseconds (ms) depending on sensory modality. Two sounds seem to fuse into one acoustic sensation if they are separated by less than 2 to 5 milliseconds. Two successive touches merge if they occur within about 10 milliseconds of one another, while flashes of light blur together if they are separated by less than about 20 to 30 milliseconds.
(Nick Herbert, Elemental Mind, Dutton, 1993, p. 50.)


Have you looked at the MiniDSP 10x10? It has many more outputs for your collection of amps, but might not be enough. You could run multiple MiniDSPs linked digitally for no delay.
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post #5 of 8 Old 07-12-2019, 09:11 AM - Thread Starter
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Originally Posted by granth View Post
How are the 6 amps wired to the preamp today? Daisy-chaining RCAs?
Y-splitters mostly, but I do have two sets of preamp outputs on my preamp (normal and inverted) and I use both, so it's not like I'm trying to run all 6 amps from one set of outputs. Really though it's not so much the number of amps that is the roadblock to running them through the miniDSP as it is the inverted preamp outputs. I make effective use of the inverted preamp outputs to bridge 4 of my amps that don't otherwise have any built-in way of being run bridged. I even use the inverted preouts for the amps that I run in stereo as there is supposedly a benefit. I don't know that it would even be possible to run an inverted preout through a miniDSP, and since bridging requires mixed use of the normal and inverted preouts, i'm really not sure how that would work. Otherwise it's a matter of completely re-configuring my system (not running any amps bridged, etc) when what I'm really looking for is just an upgrade for my subwoofer amp's low-pass filter.






Last edited by GotNoRice; 07-12-2019 at 09:28 AM.
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post #6 of 8 Old 07-12-2019, 11:00 AM
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Quote:
Originally Posted by GotNoRice View Post
I don't know that it would even be possible to run an inverted preout through a miniDSP, and since bridging requires mixed use of the normal and inverted preouts, i'm really not sure how that would work. Otherwise it's a matter of completely re-configuring my system (not running any amps bridged, etc) when what I'm really looking for is just an upgrade for my subwoofer amp's low-pass filter.

Are you using the preamp for source switching? If not, you could put the MiniDSP between source and preamp. Even the 2x4 has enough I/O for this.


Analog source -> Input 1&2 on MiniDSP
MiniDSP Output 1&2 -> Preamp L+R -> Main amps
MiniDSP Output 3&4 -> Sub amp



In this case, the MiniDSP becomes your primary volume control. You can add a potentiometer to control this externally, or go with a different MiniDSP like the 4x10HD since it comes with a volume knob and would mount well in your rack.
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post #7 of 8 Old 07-12-2019, 01:32 PM
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Personally, I don't see a problem since many people use the "sub distance" tweak to ensure the smoothest response over the crossover frequency (and that's introducing delay to the sub(s)).
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post #8 of 8 Old 07-13-2019, 01:24 PM
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From what I can gather, 2.5 ms delay is the equivalent about 3 ft of distance or so.


I experimented with some 2ch music listening, first increasing the subs distance settings to be 5 ft farther away than actual, then I made them 8 ft less (3 ft closer than actual) listening to the same music. I did not take any measurements, but subjectively I'd say the differences were subtle and might be detectable by perhaps a musician listening carefully. A casual listener (especially not doing back to back comparisons) probably wouldn't notice. I paid special attention to the bass drum beat as aligned with lyrics and other instruments.


So I don't know...…. If you can move the subs closer to your listening position than the speakers I might try it. Your subs amp/dsp is probably adding a bit of delay to the mix already.

Last edited by dpc716; 07-13-2019 at 01:30 PM.
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