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miniDSP Flex

mdsimon2

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It's pretty confident it's not volume attenuation on my Mac. Both connections are USB from the Mac, and volume on the Mac all the way up. The path's are Mac > USB > Topping D10s > optical > Flex vs. Mac > USB > Flex. The Topping/Optical path has noticeably more gain. I'm working now, but I'll see if I can get some more specific information later.

On a side note, another observation is that the Flex display turns off 2 minutes after you've last touched it (except when you are working in the plugin software and it's connected). I can't find any way to disable that, but I wish I could keep the display active all the time.

How much is noticeably more gain? I've seen ~1 dB difference between TOSLINK and USB on other products, noticeable but not a huge difference. Should be really easy to measure the difference using the Flex as recording device in REW and running some frequency sweeps with the TOSLINK and USB inputs.

Michael
 

anotherhobby

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How much is noticeably more gain? I've seen ~1 dB difference between TOSLINK and USB on other products, noticeable but not a huge difference. Should be really easy to measure the difference using the Flex as recording device in REW and running some frequency sweeps with the TOSLINK and USB inputs.

Michael
Oh, definitely not the MAC then :). Sorry the full context wasn't clear from your earlier posts. Do still check the input levels shown by the FLEX though to get a better idea what's going on, as I'm still doubtful the FLEX is the cause.
I finally had a minute to test it today, and whatever was going on last night was not the miniDSP. Doing a simple controlled test pushing 1 kHz tone from REW shows the same level in the Flex thru the TOSLINK hop or directly thru USB. REW shows it's outputting -10.00 dBFS, miniDSP shows inputs USB and TOSLINK both at -10.00 dBFS. I'm not sure what I messed up in my excitement last night, but they measure identically, so who knows. I amended my original post so nobody gets confused. ¯\_(ツ)_/¯
 

Glasvegas

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Bear in mind that it's an OLED display that may not do so well being on permanently. There have been some display issues on SHDs, although a firmware update that reduced the display refresh rate is meant to help with this. I still think I'd avoid having the display on permanently myself though, and I'm sure the current default behaviour of the FLEX is partly with this in mind.

I can speak from experience. I had to get a replacement display sent from HK for my SHD because of burn in. My own fault really, I had it set permanently on at full brightness. Now I set it to turn off after 30 secs. It turns back on when you touch anything on the remote.
 

anotherhobby

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I can speak from experience. I had to get a replacement display sent from HK for my SHD because of burn in. My own fault really, I had it set permanently on at full brightness. Now I set it to turn off after 30 secs. It turns back on when you touch anything on the remote.
Good to know, and I appreciate the info! I'll learn to be happy with it's default behavior then. :)
 

Maverick AF

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Measurements and high resolution board photos of the balanced flex here:

 

Eetu

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Thanks for the measurements. That ch 4 performance is unacceptable. Maybe someone can measure their Flex so we can confirm if all units are affected.
 
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Maverick AF

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No problem. Yes disappointing. How many people here are using their flex for an active 2 way? If channels 3-4 were only used for subs, people probably wouldn’t hear the distortion anyways. But doesn’t make it acceptable. There’s obviously something wrong. I can’t see that being something they decided was acceptable for the design.
 

Ultrasonic

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For info. a firmware update has been released:

 

RHO

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No problem. Yes disappointing. How many people here are using their flex for an active 2 way? If channels 3-4 were only used for subs, people probably wouldn’t hear the distortion anyways. But doesn’t make it acceptable. There’s obviously something wrong. I can’t see that being something they decided was acceptable for the design.
Your measurements are analog in, analog out?
 

RHO

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abdo123

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@Maverick AF Thank you for the measurements, your distortion readings were higher than any MiniDSP device in the history of the company's inception, So i'm 99% sure it's a unit fluke. However, there has been worse scandals on this site so i would not be completely surprised if that wasn't the case.
 

abdo123

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Btw if someone from MiniDSP is reading this forum and added the auto switch to bluetooth when the play button is pressed because of my comment, Thank you!
 

Ultrasonic

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It's the start of the Chinese New Year holiday so be aware miniDSP staff will be having some time off over the next few days.

@Maverick AF were your measurements at 0 dB on both source and the FLEX? If it was I'd be curious if you see the same with a very small output reduction?
 

Maverick AF

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It's the start of the Chinese New Year holiday so be aware miniDSP staff will be having some time off over the next few days.

@Maverick AF were your measurements at 0 dB on both source and the FLEX? If it was I'd be curious if you see the same with a very small output reduction?
Yes 4v output is 0dBFS with this unit. And the distortion is still there at least 30dB higher than the other outputs at all output levels.
 

anotherhobby

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I've tried a few things with setting up my Flex so far, and I thought I'd share my results. I'm also curious to hear what other people are finding works well. My setup is near field with Revel M105s and dual 8" subs in a small treated room (about 115 sq/ft with 8' ceilings).

My first attempt was to follow the manual exactly, and it turned out bad. It said to leave the sub crossovers off. My subs don't have crossovers (that's what the miniDSP is for), so they will try to play whatever you send them. This seemed like a bad idea. It also said to not have any DSP filters active at all. I don't know much about Dirac, so I did what they said and just let it rip. When it was done I set 80 Hz 12dB/oct crossovers and ran a sweep with Dirac on vs Dirac off and here is what I got:

first-run-dirac.png


It's better than no correction, but I was not impressed at all. I can get better response and sound quality with DSP alone, and I think the problem here is that Dirac runs BEFORE the routing, so it don't split the subs from the mains and has no idea I have subs. For my next run I sat down with REW for a couple of hours first and carefully crafted DSP filters on all of the 4 channels after setting the crossovers. This is where I landed compared to Dirac.

dirac-vs-dsp.png


And not surprisingly to me, my DSP filters were better than Dirac, hands down. Not just in comparing measurements, but it sounds way better. With the room response better dialed in with DSP and crossovers, I then Dirac directly on top of this without disabling any of it, and here is how that turned out:

dirac-after-dsp.png


WAY better! Doing it this way, Dirac offers a noticeable improvement in the measurement. The nulls are handled much better, and the response is smoother overall. In subjective listening, I think it sounds way better with Dirac. I don't know how to describe the sound with flower audiophile review language, but the difference is dramatic and I'm very happy with the result at the moment. That said, I just finished this about 20 minutes ago and have a lot of listening to do.

Here is a final comparison of me setting DSP+Crossovers first then running Dirac vs just running Dirac on it's own with no DSP or crossovers set first. I did not attempt to DSP after running Dirac, but I might get around to trying that too.

dirac-dsp-vs-no.png
 

Ultrasonic

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My first attempt was to follow the manual exactly, and it turned out bad. It said to leave the sub crossovers off. My subs don't have crossovers (that's what the miniDSP is for), so they will try to play whatever you send them. This seemed like a bad idea. It also said to not have any DSP filters active at all. I don't know much about Dirac, so I did what they said and just let it rip. When it was done I set 80 Hz 12dB/oct crossovers and ran a sweep with Dirac on vs Dirac off and here is what I got:

Not sure if I'm misunderstanding your post but the process that you want to follow is to first configure the crossovers (and ideally delays) in the miniDSP plugin, and then make a set of Dirac Live measurements with these active. Also, was there a particular reason you chose such a slow roll-off on your crossover? I go the other way myself and use 48 dB/octave LR filters.

Experiment with Dirac but note that some (including me) prefer to only use it in the low-bass region so do give this a try.

In the graphs you're showing above, are these measurement with both speakers playing simultaneously?
 

anotherhobby

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Not sure if I'm misunderstanding your post but the process that you want to follow is to first configure the crossovers (and ideally delays) in the miniDSP plugin, and then make a set of Dirac Live measurements with these active. Also, was there a particular reason you chose such a slow roll-off on your crossover? I go the other way myself and use 48 dB/octave LR filters.

Experiment with Dirac but note that some (including me) prefer to only use it in the low-bass region so do give this a try.

In the graphs you're showing above, are these measurement with both speakers playing simultaneously?

When I ran it the first time with no crossovers, it was because I was following the Dirac manual which stated this for subwoofer settings:

If using a subwoofer in a multichannel system, we recommend that its low pass filter be disabled if possible, or set to its highest frequency if it cannot be disabled. Any EQ on the subwoofer should be disabled or set “flat.” High pass filters used to protect the driver from over-excursion should be left in place. If the subwoofer’s low pass filter is an important part of the overall bass management in the system, it can be re-enabled after completing Dirac Live calibration and loading correction filters into the miniDSP processor.

However, after after running it, seeing my results, and thinking about it a bit more, I realized that my 4 channels (2 speakers and 2 subs) is probably not what they mean by multichannel, and I'm assuming they meant 5.1 or whatever. Also, thinking a bit further, since Dirac is applied before the routing matrix, it has no idea about even having subs, or how many, and has to more broadly apply the filters to both the subs and the mains together. Granted with a crossover it should mostly land where you expect, but it clearly can NOT apply any logic to the subwoofers individually, especially since the subs are mono. I'm honestly a bit disappointed that Dirac is being done to before the routing and is completely ignorant of subs, but maybe I'm missing something.

Following the logic that it can't separate subs from mains in the Flex, I then EQ'd the subs individually first, and as long as I was in there with my mic set up and all, I EQ'd the mains as well. It might very well be better to not EQ the mains first, but my current untested hypotheses is that it has to better to EQ and balance the subs first, then set crossovers, and then run Dirac.

I do plan on running it again without the main's EQ'd to compare. I'm really happy there are 4 preset slots so that I can try some more ways of doing things and maintain reasonable a/b testing. What I do know thus far is that the process I went through sounds really good. Better than EQ on my own, and way better than doing nothing.

As for the crossover slope, I tried some other slopes between my bookshelf sized Revel's and the subs, and the slower roll off sounded more natural and smooth/blended to me, but it was a pretty short test and not scientific. I'm open to any tips and would like to hear your thoughts on other slopes and what advantages there might be. This is a very new setup of mine (never had a miniDSP or Dirac) and I haven't messed with it that much yet.
 
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