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BT MIC issues for BT calls - asking for a sticky

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The Mic issues have been talked to death, but are still an issue it seems. I'd like to review the process of the steps involved with using the mic VC and phone calls. There seems to be a lot of confusion about whether this is a Bluetooth problem or something else. There are actually several steps along the way from your mouth to the destinations "ear" whether that destination is a person on the other end of a phone call or the VC processing unit in the AVIC. If the forum thinks we should start a new fresh thread on this since it is more a technical discussion of mic issues then we can see about that too.

 

Here are the steps I see in the process, if I've missed anything let me know.

 

 

Voice + background noise -> Microphone

Microphone (analog signal) -> AVIC audio input (AI)

AI -> Analog to Digital Converter (ADC)

ADC -> Noise Cancelation Algorithm (NCA)

NCA -> Voice Command Module (VCM) or Bluetooth Module (BTM)

If VCM then

Complete

else

BTM -> Bluetooth Hands Free Profile (HFP)

HFP -> Telephone

Telephone -> Phone Call Listener

End If

Complete

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Some of the features I have listed out above may be handled by the Bluetooth software, which seems to be from Parrot, although I cannot actually confirm anywhere online that the AVIC-Z1?0 series really does use Parrot for their Bluetooth integration. Here is a break down of the first step.

 

Lets start with the microphone.

There are three broad choices for a microphone.

non-noise cancelling Mic

differential port passive noise cancelling

Multi-microphone with active or passive noise cancelling

 

A non-noise cancelling microphone is just what it sounds like, a very simple mic that takes in sound at a single point and transfers it to an analog signal. This kind of mic has a very high signal to noise ratio. Inspecting the mic that came with the Pioneer, I believe that even that mic is not of this low basic level, although listening to all the mic issues with the Pioneer products it makes you wonder.

 

Differential port passive noise cancelling microphones have been around for a long time, (60+ years) and at first glance this appears to be the kind of mic that has come with the Pioneer. It is also the technology that is used to make a mic more directional. Basically, there are 2 openings on the mic, the opening at the front, and another opening at the back, behind the diaphragm. Sound enters both ports, and if the sound pressure wave was exactly the same through both ports, it would completely cancel out the signal because the pressure wave would be identical pushing on the front of the diaphragm and the back. Ambient sound, or noise is assumed to be coming from all directions more or less equally, while the signal, your voice, should be coming directly in front of the mic, causing a much larger pressure wave at the front than at the back ports. If all ambient noise was entering the front of the mic and the back ports with exactly the same pressure, while your voice was at a higher pressure on the front opening compared to the back this would completely eliminate all noise. Of course noise is not entering the front and back identically, so it is still picked up, but a good differential port passive mic will dramatically reduce the signal to noise ratio.

 

There are several things that can be done to make this kind of mic work better. Increasing the distance between the front port and the back port enhances the directional signal by making the pressure gradient from a signal coming from directly in front of the mic all the greater. You may recognize that this is the same thing as making the microphone more directional. Good directional mics are long and skinny. Of course, most people don't want a long skinny microphone in their car.

 

Finally, if ambient noise is not consistent in the environment then this type of microphone performs very poorly. If you have a audio signal that is very strong behind the mic, or directional from one side, it will make a large pressure differential on the diaphragm and not be cancelled out. Lets think of your car environment. If you put the microphone on the steering column in front of the dash, you may think of this as a good location because it not a very noisy location, and you may be correct on the noise. But most likely, with the back of the mic close to the instrument panel, all the ambient noise in the car will be coming more strongly to the front of the mic, making it have the same pressure differential that you are trying to create with your voice, and therefor not being cancelled out very well. Now think of a position at the headliner, right at the edge of the the windshield. this may have the opposite problem. If your vehicle generates a lot of wind noise at the windshield, then this noise will create a larger pressure differential on the back of the mic, and also be picked up and transmitted to the analog signal. It doesn't matter that the larger signal is on the back of the mic. Is there a position in the vehicle that will have most of your background noises become uniform to the front, sides and back of the mic? Where ever this magical spot is, is where you want to position your mic.

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finally there are multi-microphone units with active and passive noise cancellation circuitry. Multi-mic units are a lot like stereo vision in that differentials between microphones are measured and focused to try to pinpoint the source of a sound. In a simple 2 microphone set up, like the Parrot dual microphone unit, the signal directly in front of the mic, and directly behind the mic creates the strongest, and equal, signal on both mics and can be isolated. Isolation can happen with simple analog circuitry, or in more sophisticated systems with an active noise cancellation digital signal processor (DSP) The microphone itself may have the circuitry, or it may be relaying the stereo signal to the unit it is hooked up to for it to do the processing. This brings up the Parrot dual mic unit. I do not know if it has any noise cancelling circuitry. If it does, it would be passive for sure. I don't know if it outputs a stereo signal or not. (you'd have to look at the 3.5mm mini jack) If it does, then it would be keeping the signals from both mics separate and they could be worked on by the DSP unit in the receiver. If it only has a mono connection then the signal from both mics is combined, and without either passive or active circuitry in the mic it would be useless. You need some kind of circuitry in this case because you are trying to amplify sounds that create an equal signal on each mic, and dampen sounds that are not. This is the opposite of how the front-back ports of a directional mic work, and usually some kind of circuitry to be accomplished.

 

Some of you have, on recommendation of an installer or others, put in a parrot mic, and I have seen mixed reviews about how much it has helped. I think it is possibly just a somewhat better quality mic so perhaps gives somewhat better performance. Looking at pictures of the microphone online it seems to have a stereo 3.5mm mini jack. This does not bode well for the microphone providing significant improvement to the AVIC unit. First, if you don't use a stereo to mono adapter before plugging into the AVIC you are only getting a signal from one of the mics. Second, since the Parrot seems to output the signals separately, it indicates that there isn't any circuitry in the microphone doing noise cancellation. If the microphone is depending on the receiver unit to do that processing, then results hooking it up to the AVIC will be disappointing. I'm not sure if the noise cancelling in the AVIC is being processed by the Parrot software in the unit, but it is definitely not expecting a dual-mic stereo signal to process and therefor would not really be helpful anyway. A stereo to mono adapter would combine the signals of both mics, before they entered the AVIC, but this is problematic too. Depending on how the microphones are wired in the Parrot this may cancel signals that are close to equal on both microphones, or it may enhance them. My suspicion is that it may cancel them out but it really depends on how Parrot engineers designed the microphone to work with their receiver unit. So, potentially by making both mics work, you are making the signal to noise ratio even worse.

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That leaves us finally with just active noise cancellation microphones to talk about. There are not a lot of choices for this in your car but an active noise cancellation microphone combines 2 or more microphones, with the digital signal processing(DSP) unit required to take care of all the noise cancellation right in the unit. It outputs to the AVIC a pre-cleaned up mono signal. I haven't talked about what happens to the signal after it gets into the AVIC unit, and the AVIC is supposed to have it's own noise cancellation, although that obviously doesn't seem to work that great. With that said, sending a cleaner signal to the AVIC should help it produce a cleaner signal to the VC unit or to whoever you are talking to on the phone. I think it was VBLUE who said in an earlier post garbage in - garbage out.

 

The only choice I've found in this arena is the Andrea DA-350 auto Array. You can look at it here

 

http://shop.andreaelectronics.com/default.aspx?page=item+detail&itemcode=DA-350

 

This is not an inexpensive choice as the microphone costs $317 on Amazon. but it outputs a very very clean signal to a 3.5mm mono mini jack, exactly what the AVIC unit is looking for. My suspicion is that the pioneer VC and Bluetooth issues would be significantly reduced with this microphone since it is doing all the heavy lifting. I haven't bought the microphone yet, but I am considering it. Have any other forum members tried using an active noise cancellation microphone?

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i know this would be kind of silly, but if the bluetooth doesnt work well in the 130bt, could i use my old bluetooth adapter that i had on my avic-d3. That thing seems to work flawlessly. i cant remember the pioneer model number but it was the add on bluetooth available at the time.

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First time poster here, so is the BT calling issues,  are they also in the AVIC-Z140BH?  I am thinking of buying this unit and this is the one aspect of the unit I want to work and work well.  Any thoughts would be most appreciated!!!

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i know this would be kind of silly, but if the bluetooth doesnt work well in the 130bt, could i use my old bluetooth adapter that i had on my avic-d3. That thing seems to work flawlessly. i cant remember the pioneer model number but it was the add on bluetooth available at the time.

It doesn't really matter what passive noise cancelling mic you use, you will get a similar result. The factory mic is a piece of junk, but you aren't going to get significantly better performance by replacing it. The noise cancelling circuitry that does the processing inside the AVIC is the part that sucks. If you can find an active noise cancelling mic, like that Andrea DA-350, it will take some or all of the burden off the internal processing.

 

I'm really tempted to try out an Andrea DA-350 with my z130bt, but the cost is just too high. I've been looking for cheaper options, and found the Phoenix Audio MT107A. It's seems to be more flexible than the Andrea, as the mics are external and it also has a phantom power supply, so you can use something much better like FET mics. You can plug the box into a usb port and tweak the various parameters with the available apps. Retail price seems to be ~$150, which is half of the Andrea. It's still not cheap, but I'm hoping to sniff out a deal...

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Ok, I've been in some give and take with Andrea technical support as to the use of their DA-350 mic with any of our AVIC Z units.  The key issue is (cut and past key parts):

 

"after doing some research on the Pioneer devices it looks like the DA-350 will not work with the" Z1-3 or Z110-140 "as they are showing a mic level in and the 350 is a line level in device."

 

"The problem with this is that you are going to have a digital in signal and analog output."

 

"What I was meant by converting the signal was to take the DA-350 plug which is line level and convert it to mic level"

 

Ultimately they suggested a solution so the DA-350 could be use.  Final cut and paste:

 

"I have spoken with one of our technicians and we could modify a product that we sell to one of our industrial users for you. The unit is a 3.5" solid adapter and the DA-350 plugs in one side and you would need a short double ended extender to plug into the Z3. Basically this would be an attenuator, which will reduce the strength of the line level in to match the lower mic level in. The price of this unit would be $19.95."
 
Since I use my bluetooth in my rather noisy sports car regularly for work calls, I'm intending on making this investment.  To that end I'm in the process to "sniff out a deal".  If it all plays out, I'll report back results. 
 
If our units had a USB input port, the adaptor wouldn't be needed.
 
Here is a link to a spec sheet that compels me to investigate this option further:  http://shop.andreaelectronics.com/customer/anelco/images/product_thumbs/da-350/DA350SpecSheet2.pdf
 
and
 

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So basically the DA-350 as is won't work on our units.

 

I guess since my system is only in my "pleasure" car it's not a big deal, and I can live with the shitty mic for the times I drive it.

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So basically the DA-350 as is won't work on our units.

 

I guess since my system is only in my "pleasure" car it's not a big deal, and I can live with the shitty mic for the times I drive it.

 Maybe not "as is", but for another $20 not that big of a difference to as needed.

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Found a source for a DA-350 that wasn't so out there, so will order the adaptor and will report back.

You bought the one that sold for $20 on ebay didn't you? That damn ebay app didn't send me a reminder, otherwise it would be mine. I checked the auction and it had ended 20 minutes prior.

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