Minidsp Flex Review (Audio DSP)

[Genstruktur]

Im just wondering about one thing. I run my Flex at 0 global volume and 0 at both input and output. Seems im quite near clipping the Flex, and perhaps even my amplifier rated 1.9V at input, when i play the loudest.

If i would make any filters with positive gain in Flex that would mean a loss of headroom right, and it would be even easier to drive the system into clipping?

I know, i need a more capable system. Its was fine before when i lived in an apartment but with my own house i play at significant higher volumes. I need to upgrade .

 

[brombo]

I run the usb or toslink audio output of my htpc at 95% and only use the volume control on the Flex 8 or Flex balanced to control the sound level from the speakers. Note that each channel on the Flex 8 drives a 250W Hypex Ncore channel on my Buckeye amps. I have not come close to clipping on any of the channels. For the home theater (basement) I have the Flex driving at Crow amp (500W/channel for subwoofers) and Buckeye amp (Hypex Ncore 500W/channel for JBL CBT 70J-1 speakers). The main difference is that upstairs I drive the amps single ended and downstairs balanced. No sign of clipping in either system.

 

[Genstruktur]

Well doesent it depend at what spl you are listening to also? Im quite near 0dbfs in the Minidsp software console.

 

[brombo]

What also counts is what is the gain of your power amplifiers and what is the sensitivity of your speakers?

 

[antcollinet]

I run the usb or toslink audio output of my htpc at 95% and only use the volume control on the Flex 8 or Flex balanced to control the sound level from the speakers. Note that each channel on the Flex 8 drives a 250W Hypex Ncore channel on my Buckeye amps. I have not come close to clipping on any of the channels. For the home theater (basement) I have the Flex driving at Crow amp (500W/channel for subwoofers) and Buckeye amp (Hypex Ncore 500W/channel for JBL CBT 70J-1 speakers). The main difference is that upstairs I drive the amps single ended and downstairs balanced. No sign of clipping in either system.

What also counts is what is the gain of your power amplifiers and what is the sensitivity of your speakers?

None of your amp specs, or speaker specs matter - if you are clipping digitally in the Mini DSP before the signal even reaches the amp.

Which is what I believe @Genstruktur was referring to. If you put near 0dbFS into the mini DSP, then implement a filter with positive gain - it is going to clip.

 

[brombo]

What is the input to the miniDSP? Using my htpc as a digital source I don't see how to clip digitally unless over amplification is turned on (there is a warning about that). Note that I am running Ubuntu 22.04 as my OS and using Kodi and VLC to play back digital source files. If you use the analog inputs of the Flex I can see digital clipping happening if the analog signal is too large.

 

[SoySalsaPicante]

What is the input to the miniDSP? Using my htpc as a digital source I don't see how to clip digitally unless over amplification is turned on (there is a warning about that). Note that I am running Ubuntu 22.04 as my OS and using Kodi and VLC to play back digital source files. If you use the analog inputs of the Flex I can see digital clipping happening if the analog signal is too large.

If you’re using DSP and apply any sort of filters that boost, and your volume is 0dB, you will clip.

 

[Genstruktur]

Yes i use analog in/out only. You are right @antcollinet thats what i meant. My English, and knowledge, isn't allt that great .

But i understand that using the Flex at 0 is recommended for best Audio quality (and bit-depth?), when using it for analog in/out just passing the signal? I also do not wish to lower my overall spl at MLP.

The only thing i can think of is maybe get another amplifier with let say 1.4 V max at input for 200w@8ohm (like my the one a have now or more W would be even better). Then i could lower the volume on Flex output but get the same watt? Or am i mistaken?

Im not sure that im clipping the Flex but when i play loud i have noticed peaks up to -1.5 at input and output in device console.

 

[TurtlePaul]

Yes i use analog in/out only. You are right @antcollinet thats what i meant. My English, and knowledge, isn't allt that great .

But i understand that using the Flex at 0 is recommended for best Audio quality (and bit-depth?), when using it for analog in/out just passing the signal? I also do not wish to lower my overall spl at MLP.

The only thing i can think of is maybe get another amplifier with let say 1.4 V max at input for 200w@8ohm (like my the one a have now or more W would be even better). Then i could lower the volume on Flex output but get the same watt? Or am i mistaken?

Im not sure that im clipping the Flex but when i play loud i have noticed peaks up to -1.5 at input and output in device console.

Is the volume of your amplifier turned up as loud as it will go? If not, turn it up and turn down the flex by a few dB.

 

[Genstruktur]

Is the volume of your amplifier turned up as loud as it will go? If not, turn it up and turn down the flex by a few dB.

Well it depends since im controlling the volume with it, it's an AVR Denon X3800h.

Oh you mean my power amplifier? Its a Rotel RB-1582 MkII and it has no volume control.

 

[antcollinet]

The only thing i can think of is maybe get another amplifier with let say 1.4 V max at input for 200w@8ohm (like my the one a have now or more W would be even better). Then i could lower the volume on Flex output but get the same watt? Or am i mistaken?

That wont help with digital clipping. If your analogue input results in -1.5 dB at the input - then you have a filter that boots some of that by (say) 10dB then. you might have peaks as high as +8.5dB. This will clip. and will sound bad.


The solution is either to turn down the input, put a negative gain on the input - or only use filters with negative gain. Ie tame the peaks in your room response, don't attempt to fill the nulls (which can't be done very successfully in any case)

 

[Genstruktur]

That wont help with digital clipping. If your analogue input results in -1.5 dB at the input - then you have a filter that boots some of that by (say) 10dB then. you might have peaks as high as +8.5dB. This will clip. and will sound bad.


The solution is either to turn down the input, put a negative gain on the input - or only use filters with negative gain. Ie tame the peaks in your room response, don't attempt to fill the nulls (which can't be done very successfully in any case)

Well you are maybe right. I have a hard time wrapping my head around this .

I dont think i will boost that much because my system isnt that capable in the lower regions. I have only filters with negative gain in my Flex right now but i havent tried them yet. Will negative filters increase the headroom in the Flex?

 

[SoySalsaPicante]

Well you are maybe right. I have a hard time wrapping my head around this .

I dont think i will boost that much because my system isnt that capable in the lower regions. I have only filters with negative gain in my Flex right now but i havent tried them yet. Will negative filters increase the headroom in the Flex?

If you run only negative filters, you will very likely be able to safely use 0.0dB volume without clipping. You’re not adding headroom, but you’re not losing headroom compared to if you use filters that boost.

 

[antcollinet]

filters increase the headroom in the Flex?

No - because they will only reduce the output level for part of the frequency range.

 

[Genstruktur]

Great, thank you both for helping me . @antcollinet @SoySalsaPicante

 

[antcollinet]

Great, thank you both for helping me . @antcollinet @SoySalsaPicante

Welcome.

 

[Genstruktur]

I did a test. Maybe not so scientific.

Plugged in the computer and ran a 0dbfs 50Hz signal. Max volume on the computer connected via hdmi. Monitored the dB meters in Flex Device Console.

The receiver's master volume is at 0 in the test and also Flex's master volume at 0. Analog in Flex is at 0.

Fronts +4 (current in the receiver)
Flex input/output 0
Main in in Flex= -7.3 - 8.8dB
Main out Flex= -7.3 - 8.8dB


Fronts -2 (max reduction if I want to be able to maintain the balance to surround/atmos speakers).
Flex input 0
Flex output +6.
Main in Flex= -13.3 - 14.6
Main out Flex= -7.3 - 8.8

From that test it seems to be possible to set the fronts down in the receiver and get the same dB out in Flex if I raise the main out as much as I lower it in the receiver. I also tested a few steps in between with the same results. The meters fluctuate a little so that's why a range is indicated.

I raised the receiver's main volume to +7.5 (wanted to check when Flex clips). This would also clip my Rotel RB 1582mkII of course.
Fronts receiver -2
Flex input 0
Flex output +6
Main in Flex= - 6 - 7.6 approximately
Main out Flex= Sometimes 0 and a little over (like +0.3), red color on the meters.

I actually wonder if it doesn't sound a little better to lower the receiver fronts and raise the Flex Main out.

Im aware that this do not create moore headroom for boosting filters in the Flex.

Hold on, do i really need to adjust level of surround and atmos speakers inte the receiver? Because if don't need to adjust the surround and atmos speakers maybe i should aim for 0.6 - 0.8 V max att receiver pre out?

Edit: I do not need to adjust surround and atmos speakers in the receiver!

So i measured with multimeter that i was at 0.6V from Denon (from Amirs measurements) pre out att 0 main volume (-4 fronts receiver and +8 Flex output), this is reference volume for movies. I usually listen at 0 to + 3 with music and around -3 with movies.

 

[testp]

already mentioned above, i would clarify: negative filter mean, if you want to boost some area, you actually lower everything else around it, then you get the same effect as using negative gain (with boosting). <- both do the same thing.

 

[Acapella]

Some question to the users of the MiniDSP Flex (Balanced or Unbalanced I think does not matter).
Does your MiniDSP Flex stay in standby (when you set it to standby with the remote) when plugging out the power supply and then plugging it in after some time?

Maybe some users can give me some feedback here.
Because I plan to use some MiniDSP Flex and when I am not at home then the power for the complete stereo system is removed using some smart plug, so when the MiniDSP Flex will not stay in standby after the power comes up again, then this will be a blocker for me.

 

[vicenzo_del_paris]

Some question to the users of the MiniDSP Flex (Balanced or Unbalanced I think does not matter).
Does your MiniDSP Flex stay in standby (when you set it to standby with the remote) when plugging out the power supply and then plugging it in after some time?

Maybe some users can give me some feedback here.
Because I plan to use some MiniDSP Flex and when I am not at home then the power for the complete stereo system is removed using some smart plug, so when the MiniDSP Flex will not stay in standby after the power comes up again, then this will be a blocker for me.

When power comes up again after power loss, unit reboots and stays on.
Which indeed can be annoying.
I am using Logitech Harmony automation.
When power comes back, I have to put the unit in standby otherwise next time I use it, my harmony activity puts in in standby.