Minidsp Flex Review (Audio DSP)

[Multicore]

Do you have the ability to generate a test tone (REW)? Do you have a DMM? If so I would play a 100 Hz test tone in REW and measure the output voltage of the D50S and Flex with the DMM and see what you get. I expect both to be around 2 V (assuming no filtering on the Flex) at 0 dBFS.

Michael

I could but it's a slog. Everything is installed in the living room a long way from any computer i could use for that.

 

[Multicore]

Fair point but he is using a TRS to RCA adapter which should result in 2 V just like the D50s.

I had thought that the cable just ties one end to the RCA's ground. But it actually divides the voltage swing?

 

[RHO]

I had thought that the cable just ties one end to the RCA's ground. But it actually divides the voltage swing?

Balanced is 2V - -2V = 4V. When only using the hot you get 2V - 0V = 2V.
Cold gets subtracted from hot at the input of a balanced connection. This means you subtract the noise that was injected from the noise (resulting in 0 noise left) and the useful signal from the inverse of the useful signal, resulting in 2x the useful signal (voltage).

 

[mdsimon2]

I had thought that the cable just ties one end to the RCA's ground. But it actually divides the voltage swing?

From the TRS side the miniDSP cable leaves the ring (-2 V) unconnected so the voltage at the RCA out will be tip (+2 V) referenced to ground.

Flex Balanced connectivity: Which TRS to RCA cable should I use?

The Flex balanced is balanced in/out. If you'd like to use an unbalanced amplifier (e.g. Powered subwoofer) downstream of the Flex series, here is the recommended TRS to RCA cable to minimize detrimental effect on the audio quality. Note how...

support.minidsp.com

Michael

 

[Multicore]

Balanced is 2V - -2V = 4V. When only using the hot you get 2V - 0V = 2V.
Cold gets subtracted from hot at the input of a balanced connection. This means you subtract the noise that was injected from the noise (resulting in 0 noise left) and the useful signal from the inverse of the useful signal, resulting in 2x the useful signal (voltage).

From the TRS side the miniDSP cable leaves the ring (-2 V) unconnected so the voltage at the RCA out will be tip (+2 V) referenced to ground.

Flex Balanced connectivity: Which TRS to RCA cable should I use?

The Flex balanced is balanced in/out. If you'd like to use an unbalanced amplifier (e.g. Powered subwoofer) downstream of the Flex series, here is the recommended TRS to RCA cable to minimize detrimental effect on the audio quality. Note how...

support.minidsp.com

Thank you both. This probably accounts for some of the surprise I related by saying "The output seems low". Although I think not all. Sometimes I use both the Flex's and amp's knobs both max. Any my Ascend Sierra Towers aren't especially inefficient.

Now I want to go check if I've read about other ways of wiring balanced to unbalanced, perhaps suitable for particular driver types, that might have led me to understand this differently. But I really need to pay attention to other things.

 

[SlowCar]

Will this device with basic Dirac handle well 2.1 system or i will have to buy subwoofer Dirac extension (dirac bass control)?

 

[Multicore]

Will this device with basic Dirac handle well 2.1 system or i will have to buy subwoofer Dirac extension (dirac bass control)?

Idk. We're not getting the Dirac option. The User Downloads page for Flex has only two firmware builds, one with and one without Dirac. But maybe licensing options exist within that build.

MiniDSP's own support incl. its forum may have or be able to give the answer.

 

[TheBatsEar]

Will this device with basic Dirac handle well 2.1 system or i will have to buy subwoofer Dirac extension (dirac bass control)?

Idk.

Dirac bass control is not part of the Dirac firmware for the 2x4 HD or Flex.

You have to integrate subs using the normal plugin (DDRC-24 and Flex use the same plugin), then you use Dirac:

2.1 Sub integration + REW

miniDSP is a leading manufacturer of Digital Audio Signal Processors for the HomeTheater, Hifi, headphone and Automotive market. Join our large community of Audiophiles, Engineers and DIYers using our innovative products.

www.minidsp.com

 

[MCH]

Will this device with basic Dirac handle well 2.1 system or i will have to buy subwoofer Dirac extension (dirac bass control)?

I asked something on these lines long time ago in the other thread and members explained that dirac bass control or whatever it is called is only available in expensive devices and seems unlikely that the flex ever offers it. Well, this is what i understood from the coments.

 

[SubsonicLurker]

Will this device with basic Dirac handle well 2.1 system or i will have to buy subwoofer Dirac extension (dirac bass control)?

I'm in the same 2.1 channel situation you're in. When I checked Dirac's site regarding last month, it looks like 2.1 channel management requires an upgrade to their multichannel suite which is an additional $150.

Dirac Live Room Correction Suite – Dirac

Dirac Live Room Correction Suite features patented algorithms to digitally reduce the room impacts and enhance the accuracy of sound reproduction, from timing and frequency...

www.dirac.com

 

[mdsimon2]

I'm in the same 2.1 channel situation you're in. When I checked Dirac's site regarding last month, it looks like 2.1 channel management requires an upgrade to their multichannel suite which is an additional $150.

Dirac Live Room Correction Suite – Dirac

Dirac Live Room Correction Suite features patented algorithms to digitally reduce the room impacts and enhance the accuracy of sound reproduction, from timing and frequency...

www.dirac.com

It depends on what you mean by "2.1 channel management". Fundamentally the Flex is a 2 in, 4 out device and Dirac is applied on the 2 channel input. Therefore unless there is a substantial architecture redesign it will never do anything more than 2 channel Dirac. A 2.1 setup can easily be used with such a device, just requires you to establish the subwoofer / main crossover before running Dirac.

Multichannel Dirac does NOT equal Dirac Live Bass Control (DLBC). Multichannel Dirac just means that individual Dirac correction can be applied on each channel. Take for example the DDRC-88A or DDRC-88D, those are 8 in, 8 out devices that can apply Dirac correction to each channel, however they do not have DLBC.

The purpose of DLBC is to automate the crossover between your main speakers and subwoofer(s). Like multichannel Dirac it applies correction to more than 2 channels of output so in order for it to be implemented you need to have a device which can apply Dirac correction on more than 2 channels.

Michael

 

[SubsonicLurker]

It depends on what you mean by "2.1 channel management". Fundamentally the Flex is a 2 in, 4 out device and Dirac is applied on the 2 channel input. Therefore unless there is a substantial architecture redesign it will never do anything more than 2 channel Dirac. A 2.1 setup can easily be used with such a device, just requires you to establish the subwoofer / main crossover before running Dirac.

Multichannel Dirac does NOT equal Dirac Live Bass Control (DLBC). Multichannel Dirac just means that individual Dirac correction can be applied on each channel. Take for example the DDRC-88A or DDRC-88D, those are 8 in, 8 out devices that can apply Dirac correction to each channel, however they do not have DLBC.

The purpose of DLBC is to automate the crossover between your main speakers and subwoofer(s). Like multichannel Dirac it applies correction to more than 2 channels of output so in order for it to be implemented you need to have a device which can apply Dirac correction on more than 2 channels.

Michael

I'm referring to the use of the Flex as an active crossover between the L/R & sub channels, combined with the ability of Dirac to measure & adjust for those channels independent of each other. Not their bass control system.

 

[mdsimon2]

I'm referring to the use of the Flex as an active crossover between the L/R & sub channels, combined with the ability of Dirac to measure & adjust for those channels independent of each other. Not their bass control system.

As I mentioned in my previous post the Flex does Dirac on the input, therefore you will not be able to apply independent correction to each output. This is clear from the user manual which shows Dirac on the 2 channel input upstream of the routing matrix / xover / PEQ.

Michael

 

[antcollinet]

As I mentioned in my previous post the Flex does Dirac on the input, therefore you will not be able to apply independent correction to each output. This is clear from the user manual which shows Dirac on the 2 channel input upstream of the routing matrix / xover / PEQ.

View attachment 204478

Michael

Neverthe less. If you integrate your mains and sub(s) with xover and any delays prior to running dirac, dirac will happily correct the combined mains and subs as though they were just a stereo 2.0 pair.

 

[Geronimo.USMC]

Good evening. I'm looking for opinions, facts, and guidance on a Balanced FLEX for my use case since they are currently in stock, and I want to get one ASAP.

I currently have a miniDSP 2X4 HD optimizing 4 subs via RCA from my ONKYO RZ50 (RCA in).

I will buy a processor, and change all of my Single Ended RCA interconnects to XLR in the future.


My question is regarding using the Balanced TRS FLEX with my current setup. I have read about the guidance regarding the drop in performance using RCA to TRS Balanced on the input side.

Does it matter when carrying only a LFE/SUB signal to one of the inputs in my use case?

Will, at least for now, the input signal quality be at least as good as the 2x4 HD in my use case?

What exact wire/cable would I need for optimal performance on the input side? I have electronic soldering skills, so I'm willing to make or mod an existing off the shelf cable for RCA input to TRS. I saw a few suggestions, but still unsure.

Thanks in advance!

 

[amper42]

Good evening. I'm looking for opinions, facts, and guidance on a Balanced FLEX for my use case since they are currently in stock, and I want to get one ASAP.

I currently have a miniDSP 2X4 HD optimizing 4 subs via RCA from my ONKYO RZ50 (RCA in).

I will buy a processor, and change all of my Single Ended RCA interconnects to XLR in the future.


My question is regarding using the Balanced TRS FLEX now with my current setup. I have read about the guidance regarding the drop in performance using RCA to TRS Balanced on the input side.

Does it matter when carrying a LFE/SUB signal in my use case?

What exact wire/cable would I need for optimal performance on the input side? I have electronic soldering skills, so I'm willing to make or mod a pre existing cable RCA input to TRS).

The balanced FLEX is not in stock. I ordered April 25 and still have not received a shipping email. They emailed me the wait is about 3 weeks to late May. Most likely the orders after May 3 will ship June.

The Balanced to RCA cable output will simply drop to 2V going into your sub. It's not a concern for most users.
Using an RCA source to balanced input on FLEX can drop SINAD almost 20 points. However, that may not be drastically detectable to the ear.

As far as cables, shielded 1/4" TRS to RCA should work.

​

 

[antcollinet]

Good evening. I'm looking for opinions, facts, and guidance on a Balanced FLEX for my use case since they are currently in stock, and I want to get one ASAP.

I currently have a miniDSP 2X4 HD optimizing 4 subs via RCA from my ONKYO RZ50 (RCA in).

I will buy a processor, and change all of my Single Ended RCA interconnects to XLR in the future.


My question is regarding using the Balanced TRS FLEX with my current setup. I have read about the guidance regarding the drop in performance using RCA to TRS Balanced on the input side.

Does it matter when carrying only a LFE/SUB signal to one of the inputs in my use case?

Will, at least for now, the input signal quality be at least as good as the 2x4 HD in my use case?

What exact wire/cable would I need for optimal performance on the input side? I have electronic soldering skills, so I'm willing to make or mod an existing off the shelf cable for RCA input to TRS. I saw a few suggestions, but still unsure.

Thanks in advance!

I think you loose about 15dB of Sinad with the RCA to balanced input. Flex Sinad is about 115, 2x4hd isn't given as Sinad as far as I can see, but second and third harmonics alone are above -100, so yes, you'll be at least as good as the 2x4 HD. In any case, the SINAD of your subs will probably be much worse.

On the input side, you can use standard RCA to TS connectors. (DO NOT use these on the output). I'm using these:

2 x 6.35 mm to 2RCA Cable,Dual 1/4 inch TS Stereo Jack Male to 2 RCA Male Stereo Audio Cable Splitter Adapterwith PVC Shelled Housing and Nylon Braid(0.5M/1.5Ft) : Amazon.co.uk: Business, Industry & Science

2 x 6.35 mm to 2RCA Cable,Dual 1/4 inch TS Stereo Jack Male to 2 RCA Male Stereo Audio Cable Splitter Adapterwith PVC Shelled Housing and Nylon Braid(0.5M/1.5Ft) : Amazon.co.uk: Business, Industry & Science

www.amazon.co.uk

If you want to make your own, pin of RCA to tip of TS, Ring of RCS to sleeve of TS.

 

[anotherhobby]

As I mentioned in my previous post the Flex does Dirac on the input, therefore you will not be able to apply independent correction to each output. This is clear from the user manual which shows Dirac on the 2 channel input upstream of the routing matrix / xover / PEQ.

View attachment 204478

Michael

It actually works quite well for a 2.2 setup, with the crossovers set up before Dirac (as mentioned above). When you run Dirac, the subs should not be set up as mono, they should be set up as stereo. Then Dirac will effectively correct each sub independently below the crossover point as R and L channels. I get that it's less optimum than separate sub channels where you could correct them as mono, but it still works great in practice.

 

[mdsimon2]

Neverthe less. If you integrate your mains and sub(s) with xover and any delays prior to running dirac, dirac will happily correct the combined mains and subs as though they were just a stereo 2.0 pair.

It actually works quite well for a 2.2 setup, with the crossovers set up before Dirac (as mentioned above). When you run Dirac, the subs should not be set up as mono, they should be set up as stereo. Then Dirac will effectively correct each sub independently below the crossover point as R and L channels. I get that it's less optimum than separate sub channels where you could correct them as mono, but it still works great in practice.

Yes, I agree. And I mentioned this in my first post to @SubsonicLurker.

It depends on what you mean by "2.1 channel management". Fundamentally the Flex is a 2 in, 4 out device and Dirac is applied on the 2 channel input. Therefore unless there is a substantial architecture redesign it will never do anything more than 2 channel Dirac. A 2.1 setup can easily be used with such a device, just requires you to establish the subwoofer / main crossover before running Dirac.

Michael

 

[Dan B]

No, its much more than a dac - its a dsp two-way digital crossover as well, and you can aparently use USB digital input from a computer as sound source . This unit uses a XMOS at the USB input. The future for highend performance at normal prices looks good.

• Processor: 32-bit floating-point 400MHz Analog Devices SHARC DSP
• Multi-Core USB Audio processor (XMOS)
• Bluetooth streaming: LDAC™/aptX™ HD/aptX™/AAC/SBC
• Optional upgrade to Dirac Live® 3.x Digital Room Correction, Full Range Room Correction (20~20kHz)
• Audiophile performance (SINAD
• Inputs: Stereo digital (USB Audio/SPDIF/Optical/Bluetooth), stereo analog (Unbalanced RCA)
• Flexible Output versions: Unbalanced (RCA), Balanced (TRS), Digital (Future)
• USB audio recording feature (4xCH processed output via USB audio to record inputs, e.g. Vinyl)
• White/Black OLED front panel controller with IR control

The internal DSP of the MiniDSP Flex allows digital processing, including precise EQ and 2-way crossover functionality. However, the almost completely unique feature is its ability to implement FIR based phase coherent crossovers between woofer and tweeter.

It is a fact that any normal analog crossover, and any normal IIR digital crossover that emulates an analog crossover, that has a slope over 6 db/octave, has uncorrectable phase shift. While the woofer and tweeter outputs can be in phase (or 180 degrees out of phase, correctable with a polarity reversal of the tweeter) at the crossover frequency, there is a net phase shift across the audio spectrum. For example, a 12 db/octave crossover has a net 180 degree phase shift from lows to highs across the audio spectrum. A 24db/octave crossover has a net 360 degree phase shift from lows to highs.

This wreaks havoc with phase coherency. It is thus impossible for a speaker system consisting of a separate woofer and tweeter with anything greater than a crossover with a 6 db/octave slope to reproduce a recognizable square wave. To reproduce a square wave correctly, both the amplitude AND phase of each harmonic must be reproduced accurately.

Here is a snapshot of what a 4th order 24 db/octave LR crossover does to a square wave:

The only practical way around the inherent phase shift is to use an FIR (Finite Impulse Response) based digital crossover. This MiniDSP product is one of the very few devices on the market that has FIR based crossover filter capability. It allows a woofer/tweeter based speaker to actually reproduce a recognizable square wave.

Here is one cycle of a square wave from one of my homemade line source speakers using a digital FIR based 100db/octave crossover, in room, with the microphone about 5 feet from the speaker. Note the room reflections starting immediately to the right, and even in the lower half of the square wave.

The question is, is being able to line up the fundamental and harmonics of a square wave accurately audible? Most people can't answer that because they have never heard fundamentals and harmonics properly lined up with near zero phase shift across the audio spectrum from a speaker, and thus can't say if it's audible or not.

Having read of studies on the audibility of phase coherence, and then having experimented with it myself with the MiniDSP 2X4HD, phase coherence (or lack of it) is indeed audible. Here's a link to a study on the audibility of midrange phase shift:
https://www.audioholics.com/room-acoustics/human-hearing-phase-distortion-audibility-part-2

The main audible effect of lining up all harmonics with the fundamental is a less 'speakerish' and more realistic sounding midrange, especially with percussive musical instruments with lots of harmonics. It sounds more like live music and less like speakers reproducing music. 'Midrange transients' sound more realistic. Well recorded applause sounds more like applause. A well recorded solo singer sounds more realistic and 'present'.

I am not financially associated with MiniDSP in any way. I have just experimented with phase coherent crossovers using the older Mini DSP 2X4, and have become strongly convince that phase coherence (or lack of it) is indeed audible. Phase coherency is indeed a step forward in audio reproduction. I am looking forward to getting this new and improved product.