High quality multi-zone commercial audio system on a budgetPosted by Alexander Komarov • Jan 23, 2011 • Category: IT
Surprisingly, these mediocre systems often cost tremendous amounts of money - but there are certainly ways of getting more value out of the audio investment. This is what this project attempts to achieve.
First, let's look at the decision process surrounding the possible options.
Ceiling SpeakersCeiling speakers are tricky simply because of what they are - a driver in the ceiling. A quality driver is matched to its cabinet, which is responsible for reinforcing the lower frequencies, proper resonation, etc. Ceiling speakers, then, have some disadvantages:
- A ceiling speaker (most of the time) has no cabinet at all, making the open plenum space its (unpredictable) resonator. Some come with fitted cabinets (plastic buckets), at increased cost.
- Another issue with ceiling speakers is that in a typical commercial setting the ceilings are fairly high. This is both bad and good as a distant speaker creates more even coverage (no extra-loud spots), but it needs to be more powerful to reach the people below.
- A ceiling surface is also probably a considerable area to cover for even distribution, which means a large number of speakers.
- Good ceiling speakers exist (in fact, even good impedance-matched speakers exist) but cost a substantial amount. If you are going for the inconspicuous look and ceiling (or in-wall) speakers are your only option, then the extra expense may be justified. Some examples are shown.
WiringThen there is the wiring. A typical speaker has 8 ohm impedance, and impedance drops if you wire speakers in parallel (or increases when wired in series). The reason this is bad is that a regular amplifier cannot tolerate a significant impedance deviation from its normal design target (typically 4,8 or 16 ohms). Lower impedance means that your amplifier is working too hard (likely to the point of a meltdown), higher impedance means that it can't drive your speakers at sufficient volume. Hence there are only a few wiring options that produce a working multi-speaker setup:
- Get a lot of amplifiers. For example, if a small(ish) amp drives two speakers and you have 20 speakers, set yourself up with a nice rack of 10 units, and run 20 wires to the rack. Of course in a hacky set-up you might buy a few low-cost 7.1 home receivers, set them to "All-Channel-Stereo" or similar mode, and drive 7 speakers at a time with each amp, but the idea here is that you drive only one speaker per amplifier channel
- Use impedance-matching transformers. This is the principle of operation in 70V and 100V systems. The idea is that the amplifier puts out a high-voltage signal, but because the voltage is high, the current can be low (and the speaker wire can be thin and cheap).
Also, in commercial environments where wires are pulled through the plenum, all wire typically has to be plenum-rated to meet code. Plenum-rated low-gauge speaker wire is not cheap! Anything plenum-rated is more expensive, and it becomes significant when you need a large quantity - for example, a 1000' spool of 14/2 speaker wire is $300, 16/2 is $200. If you choose to use powered speakers (as I did, see below), 22AWG shielded balanced audio is only about $90 (Markertek) at this time. This is even cheaper than plenum-rated CAT5e.
Amplifiers! Then there are amplifiers. Option 1 requires a lot of weak(er) amplifiers, Option 2 requires fewer (or just one) powerful amp (and thick wire), Option 3 requires one or more 70V (or 100V) amplifier and 70v speakers (and less wire). Either way, can't forget the cost of amplifiers
The pro's of this type are obvious:
- Matched to cabinet for better sound
- Can be larger as they aren't designed to fit in tight spaces
- Can be optimally positioned (closer to the listener, perhaps)
- A powered speaker is an option which simplifies the amplifier configuration (no amplifier needed)
Of course, these speakers are large(r), visible, and hard to integrate into decor if you're going after a particular look. They will often require wall mounting, or proper mounting from ceilings (flying) which has some liability considerations and should not be done carelessly.
Music SourcesAs we were looking for continuous music in all the zones, we needed a source of music that would ideally be non-repetitive and flexible in genre. We also wanted to avoid copyright issues, naturally. Since in our setup music is largely sourced from the servers, pirated MP3's were not a good choice. For that matter, public playback of a CD is probably questionable as well. The choices boiled down to:
This could work, but you need to research copyright issues. You'd probably need a changer, and there is only so much variety that you can get from even 6 CD's
MP3s on hard drive
Same issues as above, except variety is easier to achieve. Legal issues are likely more problematic.
Personal IPods (that come and go)
Legally speaking, this somehow feels safer because of their nomadic nature, though I'm not a lawyer. Practically speaking, this is a human-reliant configuration that's prone to failure - someone forgets their IPod, forgets to plug it in and turn it on, they have some inappropriate content that gets into the playlist, etc.
Internet Streams (free, eg Shoutcast).
While I cannot speak on the legality of this option, the transient nature of streamed data certainly feels better than possession of copyrighted material. RIAA has gone after stream publishers, if I recall, but you'd have research the current state of affairs. As these are free, a lot of publishers include advertising in the broadcasts, and some of the ads may conflict with your business offerings
- Internet Streams (paid, eg Sky FM)
Same as above, minus the ads, and at better quality. Typical bandwidth requirements are 256kbit for pretty good sound (per zone).
- Paid ISP-provided music Streams (eg Comcast, Cablevision, Verizon, etc)
Same as above but without bandwidth requirements. Typically fewer channels. Requires hardware (eg cable boxes) per channel.
- Good old radio
FM or XM is of course an option. For XM, same issues as Paid ISP hardware above.
The Case At HandMy challenge was to design and put together a low cost (relatively speaking) system that would impress people with quality (not by loudness), providing that "beyond expectations" experience. These were my requirements, give or take:
- Quality Sound
- Non-exorbitant pricing
- Multiple Zones. The space is 21,000 sq ft, with the main audio areas being:
- Fitness Floor (7000 sq ft) - must be able to adjust volume of each speaker individually
- Group Exercise (2000 sq ft) - potentially louder than Fitness floor. Some walls are glass, so watch out for flutter echo
- Lobby/Cafe (Tazi's Cafe, incidentally) (2000 sq ft). This area is also to become a mini movie theater in the future. This means that we would have a surround sound setup driven by the projector screen location, and use part of it for everyday music (probably only two speakers).
- Bath/Shower/Changing Rooms - no specific design goals other than having some sort of music in there, more or less evenly covering the space
- Ability to play background music (different channels) in each zone. Channels should be easy to change.
- Ability to plug in microphones, IPod's, etc to any zone temporarily for events
- Ability to send sound from any zone to any zone
- Speakers do not have to be hidden, but should not be ostentatious.
- Set up should be able to support or at least integrate with live performances as needed
- Integration with the (Asterisk-based) phone system (Public Address) would be nice
With this in mind, I made the following decisions: