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Omni versus Cardioid (Directional) microphones, How many do I need?

Posted by Jonathan McGarry on May 10, 2013

One of the best decisions you can make for the design of any given conference room is deciding on using Revolabs microphones to provide an exceptional audio experience.  Now that the most important decision has been made, let’s talk about some of the other ones you need to think about when designing a space with Revolabs microphones.

As a Field Application Engineer, I am often tasked with assisting on helping a consultant, an end-user, or integrator decide on which microphones are going to be the best fit.  One of the most common questions I get is, “Should I use omnidirectional or directional tabletop mics?”  Typically, I always answer this question with several more questions (something I believe Socrates would approve of).  What I am most keen on knowing is, “What does the room sound like when no one is making any noise?”  This is a leading question to tell me more about the ambient or background  noise (HVAC, projector fans, street traffic) in the room. Another important factor is how easily sound is reverberated throughout the room based on construction and furniture materials.  Does the conference room have three glass walls and/or windows that face a busy street?  Often architects want rooms that look nice, but sometimes that architectural design translates in to rooms that have less than desirable acoustic properties.  Knowing these properties will point you in the right direction when choosing a microphone.  Lastly, I will also ask if any local voice reinforcement is going to be done as well as this need can dictate what mic you want to choose.

When it comes to using Revolabs tabletop mics, the question becomes – omni or directional?  Well, both have their advantages.  Omnidirectional mics have a unique quality to them where their biggest asset can sometimes also be their biggest drawback.  They have a 360 degree pickup range that covers a large area.  If you’re in a large room that has low levels of ambient noise, this is great!  If you’ve got loud HVAC, glass walls, or trucks zooming by on the street all day, well then this can make the overall quality of the audio coming from the room suffer because based on their 360 degree design they could be picking up a lot of the unwanted ambient or background noise in the room.

  Omni.png

The directional tabletop microphone has a much more focused pickup pattern, which helps mitigate ambient noise and allows the mic to be more directly aimed at the person you are trying to "hear".  This more focused, precise pickup pattern can help minimize any unwanted background noise that is inherently in the room.

Cardioid.png

Often, the answers to my questions about the ambient noise levels in a room are unknown.  Whether it is a new construction, a bid, or whatever the case may be – sometimes we can’t know the answer.  If this is ever the case, I always urge that people err on the side of caution and use directional mics so that there are no “surprises” once a room is finished and fully operational.

Based on what type of mic you decide on, this then also dictates how many channels you will need.  Our rule of thumb here is that an omnidirectional mic can pick up 4-6 people sitting on either side of a table where the mic is at the center.   If going with a directional mic, we suggest that it cover 2-3 people that the mic is facing toward.

Another important thing to note is there is occasionally the need to locally amplify the microphones, what is commonly referred to as “voice lift”.  When the situation calls for voice lift, we always suggest that you use our directional mic as using the omnidirectional can cause feedback problems due to its larger pickup pattern.

In the end, I hope that you find this helpful in deciding which Revolabs microphone best suits your needs.  A little definition of how they work goes a long way, and in the words of Socrates, “The beginning of wisdom is the definition of terms.”  Please feel free to contact me by emailing support@revolabs.com

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What Revolabs Microphones Are Appropriate For Voice Lift?

Posted by Revolabs Technical Staff Writers on May 3, 2013

Voice lift specifically means the use of a microphone(s) to amplify or lift one’s voice in a given space.  When a system is setup for voice lift speaking into a microphone will cause their voice to be broadcasted back into the room through their speakers essentially amplifying it so that everyone in the space can hear them clearly.

NOT all Revolabs products should be used for voice lift!  The Solo series systems have a limited audio bandwidth.  They were originally designed for standard definition audio and video calls only.  They have a frequency response pattern of 100Hz-6.8 KHz.  Any frequencies that are outside this range will distort the audio as the microphones are not designed to handle those frequencies.

For audio conferencing the audio bandwidth of the standard telephone line is 300Hz-3.6 KHz.  This means that none of the audio artifacts/distortion are heard.  However should you attempt to do voice lift with a Solo series product, when you connect the system to a speaker you will get all the audio; the audio within their frequency response pattern and the artifacts/distortion outside of their range.   Even very low end speakers will have an output capability of 7 KHz or greater so the likelihood you’ll hear the artifacts/distortion is very high.

The Solo Series products include:  Solo Desktop, Solo Executive and the Fusion.   These products are NOT recommended for voice lift.  (Note: While not a part of the Solo series, the Xtag and FLX series should also not be used for voice lift).

With our HD series the microphone elements are designed with a frequency response pattern of 50Hz-14,000 KHz.  The HD microphones can process the entire band eliminating any distortion or artifacts. This is why we recommend the HD series whenever voice lift and/or HD Conferencing is taking place.

-Bryan Adams

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The Whole Wired World Can Now Be Wireless! - Part 2

Posted by Revolabs Technical Staff Writers on April 29, 2013

Earlier this month, we posted this blog about using phantom powered microphones with our wireless XLR transmitters.  We got a great comment back and wanted to address the question using some new photos, read on!

We often get asked the question.  “Can we use our wired boundary microphones with your XLR adapter?” And so far the answer has been, unfortunately not. That is not up until now.

This question came up so many times that we decided to look further into it and bought an off the shelf phantom power unit from Canford Audio to see what we could do.

The Polymer –Lithium rechargeable battery we use in our microphones and adapters has an excellent service life, but at 3.7 volts doesn't’t have enough oomph to provide the power requirements of condenser or other Phantom powered microphones. The principle behind this idea is to use the phantom power unit to provide the voltage these microphones need, and on the output transmit the signal to where it’s needed. Simple! Okay, so it needs to be plugged into the mains, but that doesn't usually represent a problem.

You can even use the Revolabs Always-On charger if you want your existing microphones not only to be wireless, but on all the time.

-Geoff Hellyer

Part 2 Update: On April 28, 2013, a reader named Scott H submitted this great comment

Geoff-

Thank you for addressing this question.

But, I'm not clear if you are saying it's now possible to use wired boundary mics with the XLR adapter or not. Are you saying it's possible with the Canford Audio phantom power unit? Which require each mic to be AC connected?

Thanks for clarifying.

Revolabs' response:

Hi Scott and thanks for taking the time to post back! To clarify we use the Canford phantom power supply in order to provide the wired microphone the power it requires as a condenser microphone and then use our XLR adapter to transmit the audio. This is great for Lectern units or many wired mic applications for that matter. Of course the phantom power supply still needs a mains supply but that's all it needs! Have a look at my photos below at the dual channel phantom unit in our UK test lab and let me know if you need more details.

Thanks

Geoff Hellyer

Revolabs Inc.

Field Sales Engineer (EMEA)

  

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