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Audio A10 Vs Lectro SSM Phase with DPA 6060


LuisT
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Hello Everybody,

 

i did recently some range tests with a Lectrosonics SSM and an audio LTD A10 with 2 DPA 6060.

 

I appeared after i put the files in Pro Tools that the 2 channels' phase are completely reversed. I swapped both mics and i have still the same result.

 

The SRC and the A10 Rx phases are all positives.

SSM compatibility mode is set to DPA.

 

Am i missing something here?

 

I never had to invert phase on similar mics in the past with different transmitters. (Also, same position for the 2 mics of course)

 

Thanks

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Hey Karl,

 

my ssm's are running 1.08 and into "In DPA" mode.

 

Could it come out of the A10 as well? Someone from Sound Devices?

@Paul Isaacsmaybe ?

 

Basically my problem is that the SSM and the A10 Tx are phase reversed with the same mic and same polarity on the Receiver end. I never encountered this before and i try to understand it.

 

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assuming that have you compensated for the different latencies of the two systems (2ms for A10, 3.6ms for lectro),

it could be that having the SSM in DPA mode has swapped the phase, but because there isnt a DPA mode for the A10, you'll need to change the output phase in the A10 menu, or at your recorder

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Hey rich, thanks for your input. Does not look like 1.6ms delay beetween the 2 systems but like you say the SSM DPA mode vs the A10 with no mode.

 

But what is still weird is that i shoot many times with A10 from rentals and never had this issue.

 

 

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On 12/27/2021 at 11:53 AM, rich said:

assuming that have you compensated for the different latencies of the two systems (2ms for A10, 3.6ms for lectro),

it could be that having the SSM in DPA mode has swapped the phase, but because there isnt a DPA mode for the A10, you'll need to change the output phase in the A10 menu, or at your recorder

The end-to-end latency with the SSM and any 3rd-generation Hybrid receiver (SRc, Venue 2) is about 2.9 ms. Your figure for the A10 is correct, thus the difference between the two should be about 0.9 ms.

 

There are several ways to adjust for the polarity mismatch - first, as you suggest, the output polarity in the A10 receiver can be switched to reverse. This can also be done in the Lectrosonics receiver. Also, instead of "DPA" input setup in the SSM, use a custom setup with the following values: Bias 4, Reistance Lo, Polarity pos (normally it is "neg" in the standard "DPA" setting).  

23 hours ago, LuisT said:

Hey rich, thanks for your input. Does not look like 1.6ms delay beetween the 2 systems but like you say the SSM DPA mode vs the A10 with no mode.

 

But what is still weird is that i shoot many times with A10 from rentals and never had this issue.

 

 

It may be that either the A10 system or the Lectrosonics system reverses polarity in an absolute sense. But if you ever only use one of the systems, you would never notice. It's not something you can typically hear on its own. If the two systems are used for different things, i.e. lav and boom, you might not notice it then, either, since the boom mic is usually a couple of feet away from the voice while the lav is a few inches - the natural delay difference means that you wouldn't necessarily hear a phase cancellation from different signal polarity. But, you might be able to see it in the waveforms. 

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Update: we dug through the archives from a few years back and found the background info on why we "corrected" the polarity of the DPA input setup for the SSM. We found that the original version reversed absolute polarity. With firmware v1.03 this was corrected so that a positive sound pressure at the mic capsule results in a positive voltage on pin 2 of the receiver output. It may be that the A10 system then is "reversed" in this regard.  

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2 hours ago, karlw said:

The end-to-end latency with the SSM and any 3rd-generation Hybrid receiver (SRc, Venue 2) is about 2.9 ms. Your figure for the A10 is correct, thus the difference between the two should be about 0.9 ms.

 

There are several ways to adjust for the polarity mismatch - first, as you suggest, the output polarity in the A10 receiver can be switched to reverse. This can also be done in the Lectrosonics receiver. Also, instead of "DPA" input setup in the SSM, use a custom setup with the following values: Bias 4, Reistance Lo, Polarity pos (normally it is "neg" in the standard "DPA" setting).  

It may be that either the A10 system or the Lectrosonics system reverses polarity in an absolute sense. But if you ever only use one of the systems, you would never notice. It's not something you can typically hear on its own. If the two systems are used for different things, i.e. lav and boom, you might not notice it then, either, since the boom mic is usually a couple of feet away from the voice while the lav is a few inches - the natural delay difference means that you wouldn't necessarily hear a phase cancellation from different signal polarity. But, you might be able to see it in the waveforms. 

thanks for the info Karl.

it had been a while since i had checked the specs on the latency of the Lectro systems. and i was either gong from memory from a very old figure, or (which is very 2021) made up a likely sounding number and used that without actually doing any double checking.

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Hello, so from my tests, indeed what seems to solve it is to set the custom IN into the SSM with Bias 4V, Lo res and Phase Pos.

The A10 does not have an input adaptation so the phase is positive by default. 

You can clearly see in Pro tools also the Latency beetween the A10 Rx and the Src.

 

 

 

 

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  • 2 months later...
On 12/28/2021 at 9:58 PM, karlw said:

Also, instead of "DPA" input setup in the SSM, use a custom setup with the following values: Bias 4, Reistance Lo, Polarity pos (normally it is "neg" in the standard "DPA" setting).

Hi Karl,

Bias 4 is maybe to low...or I am missing something..?

"The bias voltage available in most transmitters is in the range of 5-7 volts. However, a few brands provide only 2-4 volts. DPA miniature microphones (lavaliers, headsets and instrument mics) need 5-10 volts to work correctly. One exception, however, is the low voltage version DPA 4063 which works down to 3 volts." - https://www.dpamicrophones.com/mic-university/how-to-properly-attach-a-dpa-microphone-to-a-wireless-transmitter

 

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Dejan, bias of 4v works just fine with the DPA lav mics and 4099s, etc. In fact, I'm doing a setup right now with our SSM and some 4099s, and they sound great together. I do set the load impedance to "0" instead of low, though, for more sensitivity with this particular mic. That is always an option. 

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15 hours ago, karlw said:

I do set the load impedance to "0" instead of low, though, for more sensitivity with this particular mic. That is always an option. 

I will try the same with 6061 for those "from a whisper to a scream moments"...Thanks.

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