I've previously shared about podcast quality in terms of bitrate, CBR versus VBR, and LAME versus Fraunhofer(in iTunes). But whatever method you use for encoding still leaves a remaining questions: mono or stereo?
Consider the following five things as you decide whether to publish your podcasts in mono or stereo.
1. File size
We now have smartphones and portable audio players with 32 GB or more storage. But this doesn't mean file size should be ignored. A stereo file will always be twice the size of a mono file, when the same quality is used (more on quality later).
- LibSyn and BluBrry offer limited-space media hosting. a 45 MB file will instantly fill up a 50 MB LibSyn plan.
- iPhone and other smartphones on some carriers have a 3G download limit of around 20 MB. A 25 MB podcast file won't download through this 3G.
- Local storage for your raw files may be limited. A raw stereo recording of an hour will be about 620 MB. The same recording in mono will be 310 MB. This adds up quickly when you start working with high-quality raw audio in Audacity, Audition, or similar.
But if you host your media files with another host, such as Amazon S3 or even your own web host, bandwidth usage may become an issue.
In November, Noodle.mx Network uses 2.2 terabytes (TB) of bandwidth to serve mostly stereo podcast episodes. This would cost more than $200 with Amazon S3. But if all of those episodes were mono, I would have used only 1.1 TB, resulting in a 50% split of the Amazon S3 bill if I hosted my media with them.
3. Download speed
The USA is actually quite behind in average Internet bandwidth. While “broadband” is available in most of the USA, the speeds greatly vary. Some areas charge $30–$40 per month for around 1 mbps (megabit per second) download. In the greater Cincinnati area, I recently tested 30 mbps cable connections and have friends on even faster.
But whatever the connection speed, the size of your file will affect how fast your episode downloads to your listeners. You may think nothing of a 60 MB file. But would you listeners appreciate a podcast that downloads twice as fast as it used to?
4. Sound quality
Depending on the encoding program you use, mono versus stereo may present some confusion.
- Audacity with LAME will apply your selected bitrate to however many channels you have. Thus, a quality setting of 128 kbps will return the same file size for mono or stereo. If you use Audacity with LAME (not recommended), cut the quality in half when exporting as mono.
- iTunes or other programs with Fraunhofer will properly apply the same level of quality to your channels. A mono file gets 64 kbps for the one channel. A stereo file gets the same quality for each of the two channels, so you end up with 128 kbps. These programs will automatically split the file size without your having to change anything else when you switch to mono.
So when you make a direct comparison of a 64 kbps mono file to a 128 kbps stereo file, do you notice much of a difference? Yes, there is some. Stereo will sound more “surrounding”; mono will sound more centered and “direct.” While stereo may seem better, most listeners may not notice the difference, especially if your podcast is almost entirely voice.
Even if you have music or sound effects, the quality will usually seem just as acceptable in mono. But if you podcast audio dramas, then stereo will be a lot more important as you have to communicate location for some voices or sound effects, or you need that “surrounding” feel to the audio.
If you're a vocal podcast, please do not split the voices, even partially, between left and right channels.
I like listening to podcasts throughout the day. I may be playing them through my studio speakers or walking around with earbuds in my ears. My wife Jenny will sometimes need my attention and she'll have to either yell loudly or come find me before she has any of my attention. This is because I often wear my earphones in both ears. But I can't keep doing that because I need to be available to my wife or others who may be around. And I'm not the only podcast listener like this.
Many podcast-listeners may listen through only one ear using earbuds or Bluetooth headsets. These listeners get no benefit from stereo audio. But if you have any stereo effects, these listeners will miss them if they listen through only a single ear.
Your listeners are the most important in this. While we podcasters may think stereo sounds so much better, or we have our nice 50 mbps Internet connections on a home PC, our listeners may not be in the same place. Do what's best for the listeners, not just what's best for you.
How to Make Podcasts Open Directly in iTunes
Once you copy your iTunes URL, replace the “http” with “itms” to make the link open directly in the iTunes program and skip the websites. More details about making podcasts open directly in iTunes.
New podcast about Once Upon a Time
We're launching an exciting new podcast to talk about ABC's TV show Once Upon a Time. We're still in initial production, but watch for future announcements.
What do you do when you don't feel like podcasting?
I'd like a future episode to share how we podcasters give ourselves a kick in the pants to podcast when we don't feel like it, or how we refocus, or how we get new inspiration to keep going.
Need personalized podcasting help?
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This post may contain links to products or services with which I have an affiliate relationship and may receive compensation from your actions through such links. However, I don't let that corrupt my perspective and I don't recommend only affiliates.