What good is a Center Channel Speaker?

The question in a thread on Audiogon recently came up which I thought would make a better blog post than an answer in the thread:

How much of a difference does a center channel make for video?

Honest answer:  Depends on where you sit and how well matched the center is. 

Long answer:  My first real jobs were centered around motion picture sound systems, and I recently built my second center channel speaker.   I've been experimenting with center and surround sound systems both professional and at home for decades. Let me share with you my experience.

Double Blind Testing

A few years ago I purchased an Anthem MRX 540 as an upgrade to my previous Anthem processor.  Little did I realize I'd be doing blind A/B testing with it and Netflix.   To make a long story short, the combination of Netflix + Anthem MRX disables the center channel speaker for many sources which should have it on.  This does not happen with Amazon video, DVD/Bluray or other video sources which use PCM.  As a result of this, depending on what I'm watching on Netflix I have the center enabled or disabled. It's essentially a double blind test for me, or it was until I started noticing the audio icons. 

Truthfully, though I consider myself an educated/trained listener who was constantly looking for signs of failure in an audio or video chain, I remained oblivious to this problem until I started lying down to watch.  I noticed the audio was no longer coming from the center of my TV but from whatever speaker I was closest to it.  To make the rest of the story very short, here's the lesson I learned: 

When I'm seated in the middle I cannot tell if the center channel speaker is being used or not.  

On the other hand, when I move around the room, and sit or lie down off center it's immediately obvious.  Despite all the marketing hype about a center channel being better for vocals I've found this not to be the case, and in fact in some cases can make things worse.  Here are things to consider: 

• A mis-matched center may actually sound worse tonally
• Budget and very short center channels  are often 2-way speakers aligned horizontally, which end up with similar off-axis listening problems that we discussed above. 

From these experiences I recommend a center as important when you have a variety of seating positions (which I do) and your screen is particularly large / speakers are very far apart relative to the screen. Otherwise, honestly having both side and rear surround speakers can make more of a difference in movie enjoyment. 

What follows below is a more in-depth discussion of the Anthem MRX/Netflix problem. 

Anthem MRX Bugs

This is either a limitation and a bug, or two bugs, depending on how strongly you feel.  The primary issue with Anthem and Netflix is they strictly adhere to the encoding flag being set by Netflix.  I'm not sure why Amazon Prime Video doesn't do the same, but it seems Netflix says "This is Dolby Digital 2.0" and defeats the Anthem's ability to apply post processing like Dolby Prologic (DPL).  This is the first time I've ever run into a home theater processor/receiver which did not also allow you to apply DPL.  Anthem argues this is them following the spec, but not everyone does, so I encourage you to look for processors instead of Anthem which give you more control than it gives Netflix. 

 

The second issue, and it really is a bug, is that the Anthem receiver/processor will display "Dolby Surround" even when it's NOT actually on.  At the very least, this is a bug which Anthem has refused to fix. If they are going to stick to their guns and insist it's a Netflix problem, then don't say "Dolby Surround" because Dolby Surround exactly means 2:4 channel matrix processing.