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TOPIC: Mini DSP 2x4 mixed use delay

Mini DSP 2x4 mixed use delay 1 week 3 days ago #46579

  • eforer
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Hi all,

If I were to take the mini dsp and use it to process the output to my sub woofer only (low pass filter and possibly some eq depending on delay ramifications) would the delay relative to the unprocessed signal going to my speakers create nightmarish phase issues? My subs are as close to co-positional to my loudspeakers as possible in my space, but they are still a good foot farther away from the listening position. I really don't like the way my system sounds with the minidsp in the signal chain for my main speakers, but it does have numerous benefits for the subwoofers. I'm looking at going to a nano digi as a better solution, but in the interim, I'd like to see what the consensus is on this sort of mixed mode use would be.

Thoughts would be most welcome!

***Forgot to mention***
I have a mini digi board, so I could feed the minidsp spdif via the mini digi and use the minidsp's analog outputs to the subs and pass the unprocessed spdif to my dac and so on. This would take the ADC out of the process, I'm not sure how much meaningful impact it will have in terms of timing. Presumably, the spdif output is truly unprocessed in loopback mode and not re-sampled to the internal 48khz rate of the minidsp. Am I correct?
Last Edit: 1 week 3 days ago by eforer.
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Mini DSP 2x4 mixed use delay 1 week 3 days ago #46588

  • Ultrasonic
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If you already have a miniDSP you should just try it. The sound won't be obviously horrendous since what you describe is basically what most people adding a subwoofer to a stereo setup do. As in most won't use any form of DSP. Do still adjust the sub delay to optimise phase matching though.

I expect you would be happier having a miniDSP delaying the main speaker signal if you upgraded to a 2x4 HD or an SHD. (I've used both of these for sub integration but not a 2x4.)
Last Edit: 1 week 3 days ago by Ultrasonic.
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Mini DSP 2x4 mixed use delay 1 week 3 days ago #46590

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I'm going to give it a try. I think the nanodigi + 2 khadas tone boards might be a super sweet setup.
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Mini DSP 2x4 mixed use delay 1 week 3 days ago #46591

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eforer wrote:
***Forgot to mention***
I have a mini digi board, so I could feed the minidsp spdif via the mini digi and use the minidsp's analog outputs to the subs and pass the unprocessed spdif to my dac and so on. This would take the ADC out of the process, I'm not sure how much meaningful impact it will have in terms of timing. Presumably, the spdif output is truly unprocessed in loopback mode and not re-sampled to the internal 48khz rate of the minidsp. Am I correct?
I forgot to reply to this bit...

I don't know but my guess would be that the output is resampled to 48 kHz. You could check if you have a DAC that displays sample rate?

Regarding your nanoDIGI plan note that its DSP chip is not as good as the more expensive miniDSP products, so whilst the Khadas appears to be an excellent budget DAC option the overall performance could still be limited by the nanoDIGI. I have no direct experience to comment more though. Hopefully others here will but it would be worth searching the forum to see if you can find others discussions relating to what you're suggesting.
Last Edit: 1 week 3 days ago by Ultrasonic.
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Mini DSP 2x4 mixed use delay 1 week 2 days ago #46620

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I had a thought. If I crossover at 60hz, a total of 8.5ms of delay in the sub would get me to approximately 180deg out of phase. If I invert the polarity of the sub in the plugin and then measure the total delay of the sub relative to the speakers with all the components in place, I should minimize the phase issues at the crossover point. The delay of 8.5ms should be under the threshold of my perception of separation between the signals. Is this a crackpot theory, or does it have some merit?
Last Edit: 1 week 2 days ago by eforer.
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Mini DSP 2x4 mixed use delay 1 week 2 days ago #46623

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When I referred to the difference in DSP chip performance I wasn't actually thinking in terms of the maximum delay although you are right this is another factor.

For info in my current setup I'm using a roughly 9.4 ms delay crossing over at 125 Hz to combine arrival time and phase alignment between sub and main speakers, with the sub about a meter further away than the speakers. Just making the point that it's easy to find yourself wanting a delay greater than 8.5 ms.
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Mini DSP 2x4 mixed use delay 1 week 1 day ago #46639

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Noted on the minidigi. To clarify my point on the delay. What I’m proposing is adding delay to the subwoofer to net 360 degrees of phase shift at the crossover point. I’m using magnepans as my speakers and like many Maggie users, I just let the speakers roll off on their own and don’t provide any Hp filter for them.

I’d like to leave the spdif going to my dac and feeding the Maggies completely unaltered, split the spdif to feed the minidsp to create a low pass filter for the sub. Going this route, I cannot delay the speakers and thus the only way I can think of to get things aligned is to add delay to the subs to go 360 at / near the crossover point.

My question is whether this idea of gong 360 out is stupid in general for some reason I’m unaware of. My second question is if inverting this polarity at the minidsp plug in level is a valid way to decrease the necessary delay time needed to be added to go 360 at the crossover point.
Last Edit: 1 week 1 day ago by eforer.
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