Room EQ Wizard Pro and miniDSP's New UMIK-X Microphone Array Make Multi-Channel Measurements a Reality

(October 20, 2020). Room EQ Wizard (REW) has launched a new Pro upgrade to its mega-popular REW software package. While still in its early stages, Pro’s first advanced feature is capturing multiple inputs simultaneously for both measurement and real-time analysis. Individual SPL metering is available for the first four inputs.

Measurements made using multiple inputs will deliver data showing an rms average of all captured channel magnitudes, with an option to view each channel individually or a span of individual channels collectively. REW Pro allows users to select which channels are the first and last to be captured; Java drivers on Windows limits channel capture to two channels, while macOS and Linux Java drivers offer as many channels as the interface supports.

The REW Pro Upgrade costs $100, requires REW V5.20 or later, and can be purchase by clicking here. It can also be purchased as part of a $550 miniDSP package that ships with the company’s all-new UMIK-X distributed microphone array. This array includes up to 16 microphone capsules for true real-time multi-channel measurements. Each UMA4 microphone module includes four capsules, and up to four UMA4s can be daisy-chained together with a single twisted cable. Because theater rooms can be quite large, the chain can be made up to 40 meters long and connects to a computer using a USB-A2B interface (16 channels, 24-bit/ 44.1kHz or 48kHz). And, of course, it’s fully compatible with REW Pro.

The UMIK-X kit includes the USB interface, four UMA4 microphone arrays, adjustable 1.2m stands, and a REW Pro license. You can purchase it by clicking here.

 

[Sonnie Parker]

So if I am understanding this correctly, the benefit is to capture 4 measurements at one time. It's 6.3 inches/160mm wide, so that's about the width of most heads. However, how will it take into account the first measurement that should be measured center?

 

[Kal Rubinson]

6.3" = 160.02mm.
The dimensions I see are

However, how will it take into account the first measurement that should be measured center?

Good point. I have asked them that but, so far, no reply.

 

[Todd Anderson]

Yes, that's my understanding. As for that first measurement... I guess you have to place the microphone pad with mics 1-4 at the center position?

 

[Sonnie Parker]

6.3" = 160.02mm.
The dimensions I see are
View attachment 36285
Good point. I have asked them that but, so far, no reply.

I was reading specs of 160 x 180... confused them. So that's actually 6.92 inches. Probably okay, although I prefer 6 inches since that's my head width.

Yes, that's my understanding. As for that first measurement... I guess you have to place the microphone pad with mics 1-4 at the center position?

If it measures them all at one time, they won't actually be centered like a single mic. Perhaps the averaging has some sort of magic in it to determine what the measurement would be in the actual center of the frame, since it's main purpose might be to set levels and timing.

 

[Kal Rubinson]

Probably okay, although I prefer 6 inches since that's my head width.

My wife says mine is much larger.

If it measures them all at one time, they won't actually be centered like a single mic. Perhaps the averaging has some sort of magic in it to determine what the measurement would be in the actual center of the frame, since it's main purpose might be to set levels and timing.

Perhaps but programs generally use the first "dead-on-axis" mic position for more functions than they use the others.

 

[Todd Anderson]

Ah, I see what you mean, Sonnie. Hmm... maybe @John Mulcahy can chime in! :-)

 

[Nordo]

Great to see John M actually getting some real money for his years of developing and maintaining REW.
A great man and a great product.

 

[Sonnie Parker]

Great to see John M actually getting some real money for his years of developing and maintaining REW.
A great man and a great product.

Amen to that...

 

[FrankV]

Can this great new feature be used with four individual UMIK-1 mikes for multi-seat measurements? The UMIK-X works out rather expensive if used for multi-sub balancing with MSO. The miniDSP application note for this use shows just one mike of the 4-array being used, so for four single position readings four array UMIK-X modules will be needed costing $750 and wasting 75% capability! I already have 1 UMIK-1 and new ones are currently $75 each, giving a total cost of $225 + $100 for the Pro licence.

 

[John Mulcahy]

UMIK-X has been used in automotive applications (i.e. car manufacturers) for measuring cabin acoustics.

The REW Pro upgrade can be used with any input sources that can be presented as a single multi-channel source. That would usually mean a mic array like UMIK-X or a multichannel interface with a set of analog mics. On Windows an ASIO wrapper like FlexASIO or ASIO4All would typically be needed to make multiple sources appear within a single ASIO driver wrapper.

Whilst it is possible to use this feature with multiple USB microphones on Windows when using an ASIO wrapper, this is NOT recommended because:

• REW would only be able to access the input volume for the first USB mic and would use that to adjust SPL values for all the mics, so all the USB mics would need to have the same OS volume setting
• USB mics typically provide a stereo pair of inputs, each carrying the same data, so there would be two identical input captures for each mic

I have added a note to the help about that.

 

[FrankV]

UMIK-X has been used in automotive applications (i.e. car manufacturers) for measuring cabin acoustics.

The REW Pro upgrade can be used with any input sources that can be presented as a single multi-channel source. That would usually mean a mic array like UMIK-X or a multichannel interface with a set of analog mics. On Windows an ASIO wrapper like FlexASIO or ASIO4All would typically be needed to make multiple sources appear within a single ASIO driver wrapper.

Whilst it is possible to use this feature with multiple USB microphones on Windows when using an ASIO wrapper, this is NOT recommended because:

• REW would only be able to access the input volume for the first USB mic and would use that to adjust SPL values for all the mics, so all the USB mics would need to have the same OS volume setting
• USB mics typically provide a stereo pair of inputs, each carrying the same data, so there would be two identical input captures for each mic

I have added a note to the help about that.

Thank you for your response. I was referring to using four UMIK-1 mikes, which are mono, although I notice they do present as a stereo mike in Windows. I was not aware that REW changed the input volume record level, but I guess this would explain something I've seen in the past where if the mike gets unplugged and re-plugged with REW still running (e.g. when the lead falls out whilst moving the mike), the levels are several 10's of dBs different. When does this adjustment happen and what determines if it should be changed? I presume from the calibration file? I was under the impression that using such a calibrated mike would always give the same SPL readings? If I first individually check what record volume level REW sets each mike+calibration file to and then apply these values to mikes 2 to 4 this should solve the levels problem?

I run ASIO4ALL anyway in order to access multichannel output via HDMI and I guess if all four mikes were plugged into the same USB hub then their clocks should be synchronised.

 

[John Mulcahy]

The input volume setting alters the signal level from the mic. REW needs to read the input volume setting so that it can calculate what the SPL is, taking into account the mic's sensitivity value from the cal file and the gain or attenuation corresponding to the current input volume setting.

The sample clocks are internal to the mics, they will not be synchronised.

Edit: Re your comment about the mic being disconnected, this bug was fixed in V5.20 beta 59:

• Bug fix: If using a USB mic via an ASIO wrapper and the mic was disconnected and reconnected while REW was running REW would believe the mic input volume setting was zero and increase SPL readings accordingly

 

[FrankV]

The sample clocks are internal to the mics, they will not be synchronised.

I meant synchronised in terms of long term clock frequency, they have to be locked to the USB clock or there will be dropouts.

 

[FrankV]

Edit: Re your comment about the mic being disconnected, this bug was fixed in V5.20 beta 59:

• Bug fix: If using a USB mic via an ASIO wrapper and the mic was disconnected and reconnected while REW was running REW would believe the mic input volume setting was zero and increase SPL readings accordingly

Ok, thanks. I'd missed that.

The input volume setting alters the signal level from the mic. REW needs to read the input volume setting so that it can calculate what the SPL is, taking into account the mic's sensitivity value from the cal file and the gain or attenuation corresponding to the current input volume setting.

So REW accesses the input volume just to read the level, not to adjust it. If I calibrate each mike's input level first and set their individual input volumes accordingly using software which does not apply a correction factor based on the input setting, I presume this should then work fine.

 

[John Mulcahy]

That's not how USB audio transfers work. Sample clocks are not derived from or linked to the USB frame rate. Device clocks will be running at slightly different rates and that will eventually cause problems for something like ASIO4All, which is trying to treat multiple devices as if they were one device. That is why ASIO requires inputs and outputs to be on the same device, a requirement the wrappers try to cheat. In most cases all will be fine since the rate differences are typically very small.

 

[FrankV]

I do not know how the UMIK-1 specifically works, but sound interfaces I've designed use the 1ms USB polling frequency (which is pretty accurate) to adapt to what the PC thinks is a 1 second. Synchronous mode as mentioned in the article you linked to. This way, any devices on the same bus will keep in long term sync.

 

[John Mulcahy]

I checked on the UMIK spec, it is UAC1, synchronous streaming, so does slave to the PC clock. Since PC clocks are typically 20 to 50 ppm and around 1 ppm/C drift that probably explains the clock differences between output device and input device sometimes seen when using the UMIK (which is why REW has a feature to compensate for the rate error).

 

[FrankV]

I think the USB clocks may even be derived USB master host clock rather than the PC clock. At least it should mean that four mikes on the same hub should stay in long term sync and ASIO4ALL should be able to combine the mikes and then I presume REW Pro will work with it in a similar way as an A2B Audio system such as the UMIK-X?

 

[John Mulcahy]

There would still be the issue of getting two identical inputs from each UMIK, but beyond that it should probably work. It would be prudent to check that results are as expected, since multiple USB mics providing input wasn't something that was considered when writing the USB mic handling.

 

[FrankV]

Thanks. If I go down this route I'll let you know how it turns out. Currently developing a custom DSP solution using an ADAU1466 for four subs and two mains which I hope to have working nicely as a stereo system, then will allow the AVR to provide input switching, LFE channel and bass management just for the surrounds.

 

[JoachimStrobel]

View attachment 36277

(October 20, 2020). Room EQ Wizard (REW) has launched a new Pro upgrade to its mega-popular REW software package. While still in its early stages, Pro’s first advanced feature is capturing multiple inputs simultaneously for both measurement and real-time analysis. Individual SPL metering is available for the first four inputs.

Measurements made using multiple inputs will deliver data showing an rms average of all captured channel magnitudes, with an option to view each channel individually or a span of individual channels collectively. REW Pro allows users to select which channels are the first and last to be captured; Java drivers on Windows limits channel capture to two channels, while macOS and Linux Java drivers offer as many channels as the interface supports.

The REW Pro Upgrade costs $100, requires REW V5.20 or later, and can be purchase by clicking here. It can also be purchased as part of a $550 miniDSP package that ships with the company’s all-new UMIK-X distributed microphone array. This array includes up to 16 microphone capsules for true real-time multi-channel measurements. Each UMA4 microphone module includes four capsules, and up to four UMA4s can be daisy-chained together with a single twisted cable. Because theater rooms can be quite large, the chain can be made up to 40 meters long and connects to a computer using a USB-A2B interface (16 channels, 24-bit/ 44.1kHz or 48kHz). And, of course, it’s fully compatible with REW Pro.

The UMIK-X kit includes the USB interface, four UMA4 microphone arrays, adjustable 1.2m stands, and a REW Pro license. You can purchase it by clicking here.

I happened to own two Umik1. Could I use both of them now with this Pro upgrade? Would that help, like recording phase?

 

[AJ Soundfield]

So if I am understanding this correctly, the benefit is to capture 4 measurements at one time. It's 6.3 inches/160mm wide, so that's about the width of most heads.

4 points/over the area of that rectangle at once, so as you note, more approximate to "head size", where 2 ears would be, vs a single point.

However, how will it take into account the first measurement that should be measured center?

Eh? Why would that be?

cheers

 

[Sonnie Parker]

4 points/over the area of that rectangle at once, so as you note, more approximate to "head size", where 2 ears would be, vs a single point.


Eh? Why would that be?

cheers

Dirac, Audyssey... I suppose all of the DSP auto-EQ brands, state that the first measurement has to be center to get levels and timing set.

John Mulcahy stated that since the four mics in the UMIK-X can be used as single mics, simply align one of them in the center for the first measurement.

 

[AJ Soundfield]

Dirac, Audyssey... I suppose all of the DSP auto-EQ brands, state that the first measurement has to be center to get levels and timing set.

John Mulcahy stated that since the four mics in the UMIK-X can be used as single mics, simply align one of them in the center for the first measurement.

Ah, I see. So "center" being a single point somewhere for those systems. Ok thanks.

cheers