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Image 8: Off-axis microphone response vs off-axis PA response
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Image 4: DPA Microphones’ d:screet SC4098 Supercardioid Podium Microphone
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Image 6: Sensitivity curve
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Image 7: DPA Microphones’ SC4098 Frequency Response Graph
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Image 3: DPA Microphones’ d:screet Necklace Microphone on Reverend Ryan Sweet of Addisville Reformed Church is Addisville, Pennsylvania.
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Image 5: Waveform Format of Cats versus Cass
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Image 2: DPA Microphones’ d:fine Headset Microphone on Reverend Douglas J. Dwyer of Addisville Reformed Church in Addisville, Pennsylvania.
Today's audiences have higher expectations of sound quality. As we design venues, it has become more important to ensure that every step between the source and the ear is carefully considered in order to maintain premium quality. As consoles, amplifiers, software and control platforms advance, we continuously see users forget the one thing that should be at the front of their minds: the microphone. It is most often the least-thought-about component in the design phase, but it may actually be the most important element in the sound chain.
Delivery of the message is the main priority of the Church. If a microphone is to deliver premium intelligibility it must have a fast impulse response, a wide frequency bandwidth, on/off axis linearity at all frequencies and angles, high SPL handling and exceptional stage separation. These attributes are critical in sending a clear sonic image through the sound chain. From there, everything that follows supports, manipulates and reinforces your message as acoustic energy transforms into electrons. It's critical that your microphone has the ability to capture the source with clarity and accuracy. In addition, if the acoustic design of your space is less than desirable, the first element in your sound chain needs to be able to mimic the source without adding coloration.
In a typical church, we use headworn, necklace, and lectern microphones. Each has a correct application. We want to capture sources and not capture reflections from close surfaces or sound coming from the room. Those reflections will decrease intelligibility. The closer a microphone is to the source, the more intended information you get into the microphone. The chosen angle and directionality can also further isolate the microphone from unwanted noise. A variety of microphones can be used:
•Headworn Microphone: With excellent signal-to-noise ratio, headworn mics capture detail without having to contend with reflections from surfaces around the microphone. (See image two in top image slide show.)
•Necklace Microphone: These mics maintains consistent placement and are wardrobe-friendly. A necklace microphone will put the microphone in the same place regardless of body type or clothing considerations. The necklace microphone will also compensate for lost intelligibility due to its position under the chin. This is achieved by an acoustic soft boost cap over the capsule. (See image three in top image slide show.)
•Lectern Microphones: Lecturn mics often work well because they are placed directly in front of the presenter. The directional capsule will further isolate the microphone from the reinforcement system. These microphones also display speech uniformity approximately 60 degrees around the mic capsule ensuring consistency when the presenter is pivoting his head to look at the video screen or look down to read, for example. (See image four in top image slide show.)
Proper polar pattern choice and microphone positioning is very important in battling comb filtering and feedback issues. Comb filtering occurs when identical signals picked up by two or more microphones arrive at different times, or when one microphone picks up direct and reflective sound from the same source. When the peaks and valleys of the signals are identical, they are ‘in phase,' when they drift they are considered ‘out of phase' and when the peak of a signal is in line with the valley of another, a canceling out of the signal occurs. Here's what you can do to help prevent this:
•Use enough mics to capture your performance; unnecessary microphones increase your chances of feedback/clarity issues.
•Use sound tools to adjust delay between competing microphones. Ensure that they are in-phase.
•Select proper polar patterns in order to reject unwanted stage sound.
•To maintain intelligibility when leakage does occur, select microphones with on/off axis linearity at all angles.
•Make proper use of onboard filtering. For example, you can engage the high-pass filter (HPF) on a flautist's microphone to reduce low-end energy from the string bass is leaking into it. Once the proper frequency cut-off is found, the low energy leaking into the flautist's microphone will be minimized, and will give a much more accurate image of the Flute. This will reduce phasing and un-pleasant coloration due to the distance between the instruments.
When using headsets in a live situation there are two types of polar patterns available. They are omnidirectional and directional. Both provide distinct advantages.
Omnidirectional:
•More natural tone in a controlled environment
•No proximity effect and balanced sound/not reliant on exact placement
•Better for concealment
•When used by un-trained staff
•When feedback is not an issue
Directional:
•Better choice for high energy stage with drums/instruments
•Better choice in un-controlled environment-background noise issues
•When feedback is a problem
Regardless of placement, to maintain the most intelligible sound possible, a microphone must accurately capture transients (impulse responses). Much of the intelligibility of non-tonal languages lies in the consonant. Part of what makes consonants sound different from each other is their transient content or rapid variation in level. For example: the words “cats” and “cass,” if you miss the transient of the “t” in “cats” you hear “cass.” It is important the microphone can react quickly and can handle the dynamic range. (See image five in top image slide show.)
Another major factor in intelligibility is tonal content. The graph below shows, in octave bands, what parts of the spectrum are most important to intelligibility. Be aware of how noise from other sources, including the sound system, play into what we are hearing. Human hearing is most sensitive in the ranges where intelligibility is most important. We want to make sure that the vocal content is captured with a microphone that can mimic or exceed the sensitivity of the human ear. A linear frequency response will ensure the natural reproduction of the voice. (See image six in top image slide show.)
When we consider frequency response and choosing a microphone, we consistently hear the term “flat” or “linear” response. That means we are looking for a microphone to react the same at all frequencies. If it doesn't react the same, we will get more level in the lows than highs or vice-versa and the source will be sonically compromised.
Another key point when looking at frequency response is what the microphone hears off axis. It is the sum of the signal from all angles that equals the output of the microphone. Although, it may sound amazing on axis, if off-axis sound is not represented linearly you end up with an unnatural sound. Most manufacturers who make premium products will publish specifications as polar plots and frequency response charts. Below is the corresponding chart for a DPA d:screet SC4098 Supercardioid Podium microphone. (See image seven in top image slide show.)
With this microphone, you would find the on axis sound would be true to your source. It will not make the source sound unnatural. Furthermore, as the sound system and reflections come back into the microphone on the back and sides, it will not discolor the sound of the additional information.
If an angle of the microphone is not faithfully reproducing the sound, the first thing we do is reach for the EQ. We end up turning down sections of the sound spectrum attempting to compensate for the sum total of the microphone's response. If, for example, the microphone is not linear off axis and we have an increased response at 2 kHz at the same angle as the PA speakers, the EQ would be cut at 2 kHz in order to adjust for a linear room response. While the overall response of the system would sound more natural, what happened from a speech intelligibility standpoint is because the PA is bleeding into mic at 2 kHz, we had to cut into the core area for intelligibility. We are hearing a higher noise ratio at 2 kHz and thus our intelligibility suffers even if we are able to achieve a natural tone. (See image eight in top image gallery to the right)
A microphone with a linear off axis response would not have this issue. While there will always be some PA bleed, we would not need to sacrifice quality of the source to compensate for a design flaw in the microphone. Remember, DSP cannot fix a bad microphone.
There are multiple preaching styles and comfort levels, but only a few elements that need to be intact in the microphone to achieve maximum speech intelligibility:
a.A fast impulse response
b.A high SPL handling
c.On/off axis linearity at all frequencies/angles
d.An accurate polar pattern
e.Mobility and wireless adaptability
f.Flexible mounting accessories
g.Rejection of background sound, like the Worship band…
When a microphone design possesses all these qualities, your congregation, and staff will benefit from the natural experience.