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Mac Aggregate Speakers For Super Stereo
20 November 2014
I spend a fair amount of time sitting in the recliner in my home office — reading, writing, surfing the Web on my iPad Mini, listening to music, or just thinking. When I listen to music, it’s playing in iTunes on my Mac Pro, which is sitting on the desk on the other side of the room.

Last month it suddenly struck me that I’m not enjoying very much stereo separation when I listen to music, because the two speakers are about 4 feet apart, on either end of the desk, and both are about 10 feet to my right when I sit in the recliner. By the time the music reaches me, for all intents and purposes the stereo sound has become mono.

I’ve made the diagram to the right to illustrate. From top to bottom, my office is 13.5 feet wide (it’s about twice as long, but I didn’t need to include all of it in the diagram), and all the furniture and devices are to scale. On the desk you can see the two speakers — and of course, the cylindrical Mac Pro — with the subwoofer under the desk.

You can also see that when I sit in my recliner (the yellow square), the music listening experience is not ideal. If only there were some way to have the left speaker on the coffee table or the cabinet which are to the left of the recliner. But then when I am working at my desk, I would want the left speaker to be back in its normal place on the desk.
About three and a half years ago I purchased the Monster Clarity HD bluetooth wireless speaker. This tiny Monster has a great sound for its small size of 4.3 x 3.5 x 2 inches (111 x 89 x 50 mm), and its light 7.75 oz (220g) weight. Now that it has been replaced by a newer (better?) model, you can get it on Amazon for the great price of $50!

I don’t use this speaker very often — usually only when I am travelling, or when I want some music while working in the garage. Because it normally just sits in a drawer, I thought that maybe I could use it to solve my speaker problem.

You may be asking how a separate Bluetooth speaker can be used to fulfill the function of the left speaker of my wired desktop speakers. The answer lies in a little-known capability of the Mac which can work wonders! I think it would be safe to say that only a small minority of Mac users know that Apple’s Audio MIDI Setup app (AMS-app) even exists. You may have seen its icon in the Utilities folder (inside the Applications folder), and mistakenly believed that its only function is to set up MIDI devices.

I have good news for you! Not only can the AMS-app configure MIDI device interaction (which I have never done since I don’t own any such devices), but more importantly for our purposes, it can also adjust the Mac’s audio input and output configuration.

The AMS-app allows you to group two or more physical audio devices into a single virtual audio device — and to configure the characteristics of that device. That probably sounds a bit vague and abstract, so let’s walk through an example step by step. Here’s what I did to enable my Monster Bluetooth speaker to perform the role of my desktop speaker system’s left speaker.

First of all, I turned on the Monster and paired it with my Mac. Then, in the AMS-app, I clicked on the plus sign ( ) at the bottom-left corner of the app’s window. A menu appeared with two choices: “Create Aggregate Device” and “Create Multi-Output Device.”

If you are thinking that I would want to choose “Create Multi-Output Device,” I’m sorry to tell you that that’s the wrong choice, even though it seems right. A Multi-Output Device is useful if you want to have your music playing through more than one set of speakers at the same time, most likely in two different rooms.

For my setup a Multi-Output Device would not be helpful, because the music would be playing out of the left and right speakers on my desk, AND out of the Monster’s left and right speakers at the same time. That is NOT what I want!
That’s why I chose “Create Aggregate Device” instead. Once the new item appeared in the list, I clicked on that entry, and then clicked on the text “Aggregate Device” so I could change its name to ”Main Speakers Remote”.

Next I chose the speakers that I want to be a part of this aggregate device. Because the Monster speaker is going to be my left speaker, I’m going to choose it first. You will notice that there are two Monster Clarity devices listed: one with 1 input and 0 outputs, and another with 0 inputs and 2 outputs. That’s because this Bluetooth speaker also has a microphone so it can act as a speakerphone for taking cell calls. So I put a check mark next to the Monster Clarity entry with 2 outputs, and another check mark next to Built-in Output, which is where my primary desktop speakers are plugged in.

Things start to get more interesting when I click on the Configure Speakers... button and the dialog box to the right appears. Because I selected the Monster Clarity speaker first, it has been designated Stream 1. Its left channel is 1 and its right channel is 2. Because I selected the Built-in Output second, it has been designated Stream 2. Its left channel is 3 and its right channel is 4. Make sure the check boxes next to both streams are marked.

Now the real magic happens. In my new aggregate device, I want the left channel to play through the left speaker of the Monster Clarity, and I want the right channel to play through the right speaker of my desktop speakers. So for the left-front entry I chose channel 1 from the dropdown list, and I chose channel 4 for the right-front entry. Now click the Done button.

Before we finish with this setup, I need to point out a couple of things in the main AMS-app window. You see where it says “Output Channels” and there are four little boxes with the numbers 1-4 underneath? Those don’t affect the configuration of the aggregate device — they are merely labels so you can document how you set things up in the previous step. So I clicked in the little box above the 1 and typed an uppercase L, and then clicked in the box above the 4 and typed an uppercase R.

The Clock Source and Drift Correction options are a bit of a mystery to me. My feeling is that they don’t really matter, because I am not using any kind of device that has a built-in clock for synchronization. I’ve played around with having the Bluetooth speaker being the Clock Source, and Drift Correction for the Built-In Output, and then vice versa. It didn’t seem to make any difference that I could hear.

For further information about creating and configuring an aggregate device with Audio MIDI Setup, see Apple’s article How to combine multiple audio interfaces by creating an aggregate device. You might also find this article interesting: Audio MIDI Setup: Your Mac’s Secret Sound Manager. The updated diagram to the right shows the placement of the Monster Clarity Bluetooth speaker, on top of a cabinet to the left of the recliner.

By holding down the Option key on the keyboard and then clicking on the Volume icon on the system menu bar, you can open the menu you see to the left. From there you can choose which device to use for audio output. As you can see, I’ve chosen the aggregate output device I’ve called “Main Speakers Remote”.

A strange quirk of the Mac is that it does not allow you to adjust the system volume of an aggregate device, as shown by the first screen shot to the right. Of course, when playing music, you can still adjust the overall volume in iTunes.

As I mentioned before, when sitting in my recliner and playing music through the aggregate audio output device I created, the left channel of the stereo music is coming out through the left speaker of the Monster Clarity Bluetooth speaker, and the right channel of the music is being played through the right speaker of my desktop speaker system. In order to have the music sound right, it is vital to have the proper balance between the two speakers. Unfortunately, achieving this is somewhat harder than it should be.

The key is to adjust the relative volumes between the two speakers. One approach is through software. If I want the Monster Clarity to be louder or softer, I can switch back to that speaker and adjust the system volume for it up or down, as shown by the second screen shot to the right. Then, when I switch back to the aggregate device, it remembers the system volume I set for the Monster.

The problem with this method is that I have to adjust the volume of the Monster on my Mac, which is across the room from my recliner. Therefore, I have to do quite a bit of adjusting while moving back and forth from one side of the room to the other. Seeing that the balance between the two speakers often needs to be adjusted depending on the music I am currently playing, this solution leaves a lot to be desired.

There is a way to perform these software adjustments remotely through a $2 iOS app called Mobile Mouse Pro. When in its iTunes mode, it gives you the ability to both change the audio output device and to adjust the Mac system volume (separately from the iTunes volume). With this wonderful app, I can make the necessary adjustments from the comfort of my recliner in order to achieve the proper balance between the two speakers.

The other approach to adjusting the balance is to use the volume control buttons on the speakers themselves. The location where I placed the Monster speaker is just (barely) within reach when I am sitting in my recliner. I can grab it, adjust the volume, put it back, and see how that volume setting sounds in relation to the desktop speaker across the room. If the Monster speaker needs further adjustment, I go through the process again, as many times as necessary. It is not an ideal solution, but it is not too bad either. It beats having to get up each time and cross the room to my Mac and/or the desktop speakers.

Back in the Audio MIDI Setup app, you may have noticed that in addition to configuring the virtual aggregate audio device, you can also separately configure each physical member of that virtual device. In the screen shot to the right, you can see that I have selected my primary desktop speakers which are plugged into the Build-in Output.

In order to have the right-channel output of the aggregate device play only through the right speaker of the Built-in Output, you may think it could be easily achieved by simply muting the left channel, as I have demonstrated in this screen shot.

Unfortunately, that not only mutes the left speaker of the Built-in Output WITHIN the aggregate device, but also OUTSIDE of the device. So when I choose to output the audio through the Built-in Output only instead of through the aggregate device, the left channel is STILL muted. Therefore, this apparently-good solution won’t work in a practical way after all. Even though the Monster Clarity sounds really good for its very small size and weight, the audio quality just doesn’t stand up to my desktop speaker system. Which is natural, because that’s like comparing apples to oranges — or hamsters to lions! Nevertheless, these two totally different types of speakers are very mismatched.

For quite a while I have been dreaming of buying a much bigger Bluetooth speaker for use around the house, and reserving the Monster Clarity for when I want to travel light. Once I had set up my aggregate audio output system, I thought that this might be a good time to take the plunge. So I headed over to Amazon.com to research the options.

After carefully considering the available Bluetooth speakers, and their features, price, and the reviews they have received, I decided that the Creative Sound Blaster Roar excelled in all three respects. “Free” two-day shipping via Amazon Prime always makes me happy!

My first impression of the Roar was its weight. The speaker has a modest size — 2.2 x 7.9 x 4.5 inches (57 x 202 x 115 mm) — but a heavy-duty weight of 2.5 lbs (1100g). Unfortunately, despite its glowing reviews and hyped marketing, the sound it produces is not as impressive as its heft. What promised to be a roar seemed pretty wimpy to me.

Well, I suppose the volume was loud enough, but the sound itself was quite tinny and not at all natural — very artificial. And there was not very much bass, even with its TeraBass feature turned on. It is hard to believe that I was listening to the same speaker that professional and customer reviews were raving about. I was so disappointed with the Roar’s performance that I sent it back to Amazon the next day. As I thought further about the available Bluetooth speakers, as well as my particular audio needs, it suddenly dawned on me that I was on a completely wrong track. In order to solve the audio problem in my home office, I did not need portable speakers, nor did I need battery-powered speakers. What I did need was something comparable to my existing desktop speaker system.

The solution was SO obvious! What I really needed was another desktop system, with two satellite speakers and a subwoofer. Duh! But as I looked at the small number of such Bluetooth systems, I found that they were too expensive and/or had features that I didn’t need.

Of course, I didn’t really need a Bluetooth system. I could simply run a cable the 10 to 12 feet between my recliner and my Mac. But in that case, I would need to buy a USB sound card for my Mac to plug the speakers into. And besides, I really like Bluetooth, and it seems like a more “high-tech,” “cutting-edge” solution. Therefore, I settled upon a fairly-inexpensive but highly-rated non-Bluetooth desktop speaker system — the Cyber Acoustics Subwoofer Satellite System (CA-3602a). To it I added the almost-as-expensive and highly-rated Logitech Bluetooth Audio Adapter.

Thanks once again to Amazon Prime shipping, in only two days I was ready to try out my new solution. I set up the satellite speakers on either side of the recliner, and stuck the subwoofer in the ample space behind the chair. The updated diagram below gives you a visual of the setup.

Once I had plugged the speakers into the Logitech Bluetooth adapter, which I placed on the coffee table to the left of my recliner, I paired my Mac with the adapter. Both the speakers and Bluetooth adapter work great!

One of the primary reasons I chose these speakers over the competition is because of its desktop control pod, which you can see in the product photo. With that sitting on the coffee table next to my recliner, I can adjust the overall volume level, adjust the volume of the subwoofer independently, and turn the speakers on and off (without changing the volume, as with some other speakers). In addition, I could plug in a pair of wired headphones if I so desired. I would NEVER buy a desktop speaker system that does not have some sort of control pod like this!

You might be thinking that with a second desktop speaker system arranged around my recliner, there would be no need for a virtual aggregate audio device which routes the audio output through both those speakers and the speaker system at my desk. When sitting in the recliner, I could switch to the speakers located there, and when I’m sitting at my desk, I could use the speakers located there. In theory that is true, but the reality is something quite different. I don’t know if it’s the placement of the satellite speakers or what, but when I sit in the recliner and use only the speaker system located there, the sound is very “closed in” — almost like I’m wearing headphones. I get a strong feeling of what you might call “acoustic claustrophobia.” It feels like I’m listening to the music in a very small, acoustically dead room.

In stark contrast, when I switch to the aggregate audio device I created, which routes the right stereo channel of output to the right speaker on my desk, and the left channel to the new speaker on the coffee table to the left of my recliner, the sound is very “live” and spacious, as if I were perhaps in a large concert hall, or something like that. Everyone has their own tastes, but for me the listening experience is much, MUCH better — a night and day difference!

I think the the primary reason for this spaciousness is a very slight time gap in the audio output from each speaker. I would imagine that the whole processes of sending the left channel wirelessly across the room via Bluetooth does create some sort of delay in the output.

As an experiment for this article, I attached to my Mac the Behringer UCA202 USB sound card I bought recently, and plugged the “recliner speakers” into that. Then I created a test aggregate device with the same setup as the first one, except I included this USB adapter instead of the Bluetooth adapter for the recliner speakers.

When I listened to a song through the test aggregate device, there was still more of a live and spacious sound than compared to the recliner speakers by themselves, although it was not as pronounced as when listening through the aggregate device that uses the Bluetooth adapter to connect the remote speakers. So if the timing difference between the audio output of the Bluetooth speaker and the wired speaker is large enough to sound unpleasant, using a USB sound card instead of Bluetooth could be a good option.

Whenever I’m playing music on my Mac and switch to the aggregate Bluetooth / wired audio output device — or even when I’ve already switched and I pause the music and then start it again — I’ve noticed a very interesting phenomenon. The timing gap between the two speakers starts off fairly large, which is very noticeable and not very pleasant. But within 10 to 15 seconds the timing gaps narrows down to a very small delay.

I don’t really have a good explanation for this phenomenon. I don’t think it is just my ears adjusting to the different timing of the two audio outputs. Perhaps it has something to do with the ‘Drift Correction” feature in the aggregate audio device setup? Is my Mac somehow figuring out that there is a timing difference between the two outputs, and if so, how? Very interesting!

I’m almost always sitting in my recliner when I listen to music through the aggregate audio device. As a final test before wrapping up this article, the other night I played some music through the aggregate device as I was moving around the room doing some other work. During that time, I realized that the timing difference between the two speakers was much more noticeable. In fact, it was unpleasant enough that I switch the audio output to the speakers on my desk only, which sounded much better.

So in the end, the amount of timing delay in such a system depends on how you set it up. And your personal preference regarding how much timing difference you find acceptable will be a major factor in determining what will work for you. I found a system that works for me, and I am VERY happy with it!
In the photo to the right, you can see the coffee table to the left of my recliner. On it, to the very left, is the tiny Logitech Bluetooth adapter. Into that I have plugged the Cyber Acoustics speaker system — the left satellite speaker is there on the table as well.

In front of the speaker is the control pod I had mentioned above. With it I can easily change the volume of the remote speaker, thereby adjusting the balance between that speaker and the one on my desk when routing the audio output through the virtual aggregate device.

And finally, there’s my iPad Mini, for giving voice commands via Siri. I can reach over and press the home button to activate Siri without looking — without even opening my eyes! I love it! And no, that’s not Siri on the screen, but an itsy-bitsy spider I found in my office one day.

In closing, let me list some of the benefits of my current setup:
  • The desktop speakers I chose are more evenly matched to my primary desktop speakers than were the small, underpowered, tinny, portable Bluetooth speakers I had tried.
  • These remote desktop speakers run off of AC power instead of batteries like the portable Bluetooth speakers.
  • Because the Logitech Bluetooth adapter runs off of AC power and is always turned on, it pairs with my Mac automatically when I start my computer in the morning. This eliminates the repetitive manual pairing that I had to perform with the portable Bluetooth speakers each day.
  • The control pod on the remote speakers allows me to easily adjust the balance between the speaker on the coffee table and the speaker on the desk. It also allows me to adjust the amount of bass coming from the subwoofer behind the recliner.
Have you tried setting up a similar aggregate audio output device on your own Mac? Be sure share your experience with us by leaving your comments and questions in the Feedback section below!

Now that you have learned how to create an aggregate audio output device, wouldn’t it be great to remote voice control your Mac’s audio output devices and Bluetooth audio devices? In my next article — Control Mac Bluetooth and Audio With Siri — I explain how!
This article is 13th a series of articles on this Web site related to Technology and Computing which also includes (scroll to see the entire list):
26  Oct  2010
11  Jan  2014
29  Jan  2014
5  Feb  2014
7  Feb  2014
14  Feb  2014
15  Feb  2014
16  Feb  2014
17  Feb  2014
1  Nov  2014
12  Nov  2014
Mac Aggregate Speakers For Super Stereo
20  Nov  2014
22  Nov  2014
2  Dec  2014
6  Dec  2014
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