I have a government client who is in need of 7 new wireless microphone receivers in their facility. The application is for a conference meeting center that consists of multiple microphones in use at the same time. It is also inside of a large concrete facility. The client is wondering if they should purchase analog or digital receivers and would like to know the advantages and disadvantages to both systems. They are worried about interference from different frequencies in the building as well as security. What do you believe is the best system type for this application?
Shure's Dave Mendez provided the following observations:
It is difficult to say whether analog wireless or digital wireless systems are better or worse than one another as a rule. In general, digital wireless systems tend to have "better" audio as far as dynamic response and frequency response as well as usually being less noisy at end of range situations since, like with most things digital, they are either on or off. This difference is much more noticeable though at lower to mid tier wireless. Some high-tier analog wireless systems have been designed in such a way that the audio section is actually quite good and comparable, especially if the application is only speech which requires far less dynamic range and range of frequencies for good fidelity and intelligibility.
One key thing that people latch onto with the digital versus analog discussion is latency and whether it will be an issue. Analog, of course, has zero to negligible latency while digital wireless has differing amounts of latency depending on the processing and RF mechanisms employed in the particular digital wireless system. This amount can be as little as a few milliseconds. The amount of latency that can be tolerated depends on the application as well as the people involved. For teleconferencing applications with limited to no local sound reinforcement, latencies of 15 ms or more are typical and completely acceptable. However, for performance applications, especially those involving situations where the talker/singer will be able to monitor themselves through an in-ear monitor, headphone, or close loudspeaker, latency generally needs to be much lower than that to work well.
As far as RF performance goes, the differences depend somewhat on what RF spectrum range the system actually tunes within. This can determine how many compatible systems are possible for that product and whether it is appropriate for the application. For example, we have both analog and digital wireless systems that exist in the UHF TV Band range. In this case, the digital wireless systems are much more spectrally efficient, allowing almost twice as many compatible systems (more) in the same RF footprint as an analog counterpart. However, a digital wireless system that works in the 900 MHz (902-925 MHz ISM band) or 2.4 GHz range can usually only handle about 4-5 compatible systems in total...much less than an analog wireless. Also, in certain cases, analog systems tend to do better at end of range in that they tend to hold on (with albeit noisier operation) where digital wireless may just drop at end of range (though digital usually requires less RF signal-to-noise which may balance out this difference a bit).
An important point, though, is that no matter if the system is analog or digital, RF interference is something that can happen. In the case of UHF systems (again, this applies to digital or analog wireless in this range), you still need to coordinate the frequencies to avoid direct interference from active TV broadcast and other UHF wireless sources while, at the same time, using a set of frequencies that don't interfere with each other. This can be done with software programs such as our Wireless Workbench (version 6), available for free on our web site. This can be used to help you or the customer find frequencies that avoid interference from other UHF wireless in the building. If however, the system is not UHF...many digital wireless systems in these other bands (2.4 GHz, 1.9 GHz, etc.) cannot be coordinated and instead rely on scanning and automatic frequency coordination and interference avoidance to deal with interference from other devices in those spectrum ranges. That sounds much easier (and it is) but, of course, these systems also are usually not able to do quite as many compatible systems. In this case, seven mics is not that many, though.
If security such as encryption of the wireless link is a must, the choice is already made for you between analog and digital. If you want encryption, you will need a digital wireless system. Most of our digital wireless systems employ AES-256 bit encryption, generally thought to be the most secure encryption standard. Some of our key systems that employ this standard are our Microflex Wireless operating in the 1.9 GHz DECT band, ULX-D Digital UHF Wireless, and QLX-D Digital UHF Wireless.
Another key thing to look for is the form factor of the microphones that are required by the user. In some cases, transmitter types like wireless goosenecks and boundary mics may or may not be offered within a particular product family. Therefore this also narrows your decision. For example, if you do require goosenecks/boundaries, we only have two wireless systems to choose from. These are the Microflex Wireless (Digital DECT band) or the SLX wireless (analog UHF band). The other systems only have the standard handheld and body pack style transmitters.
These are just some general points to help distinguish analog and digital wireless systems. Are digital wireless systems better than analog wireless systems. Not necessarily. The answer depends on the particulars of the application. Based on the couple of points you provided, my guess is that either the MXW or ULX-D systems would be best.