70 volt sound systems sound terrible, right? They don’t have to! Most people associate 70 volt systems with the sound that you get in the mall – from the system that was installed 30 years ago using the lowest cost parts available. 70 volt systems were designed to be easy to design and install in commercial environments. They are a great fit for corporate and professional offices, restaurants, outdoor public areas, and more. You can still go that “mall sound” route today, but there are a ton of options that can help you get all the benefits of 70 volt and still offer a system that sounds great.
We recently started a project to install a new music system in our office and want to take the opportunity to share our experience with you. Because of our existing wiring topology, a 70 volt commercial system was in order. We chose an amplifier and speakers from Speco and we are very happy that we did. The amp is a basic PBM series that has standard RCA line level inputs. We chose the SP6MAT speakers. These are not the paper-cone 70 volt speakers that you associate with that thin background music. These feature a 6.5” woofer and tweeter with built-in crossover network and a huge ported backbox. They are capable of producing so much bass that we had to trim it back a bit on the amp.
Speco publishes a Commercial Audio Guide (http://www.specotech.com/images/PDF/1410-087-Comm-Audio-Guide-2014-2.pdf) that is a fantastic resource for designing one of these systems properly and so that the sound is even in your entire space. We recommend that you use it when designing a system, but here’s a brief overview of how 70 volt works. Keep in mind the amp combines the left and right channels, so speaker placement is all about getting sound everywhere. Wiring is a simple daisy-chain – use 14 or 16 gauge speaker wire from the amp to your first speaker, then the second, and so on.
For a design, start with the speakers and work your way back to an amp. 70 volt speakers all have a transformer with multiple taps built-in. The taps determine how much power the speaker draws from the amp. Don’t think of them as volume controls, but they do allow you to provide more or less sound per speaker on the same daisy-chain. Our speakers have .25, .5, 1, 2.5, 5, 7.5, 15, 30, and 40 Watt taps. We are using the 1W and 2.5W taps in our office. Refer to Speco’s guide to help you determine how many speakers you need on a given space. It’s based on how high the speaker is from the floor. Then use the wattage chart to get an idea of what wattage setting you should need for each speaker.
Now it’s time to pick an amp. They range from very simple units with plain inputs, to more advanced units that have built-in tuners and even digital media players. Sum up the wattage setting from all your speakers, add in a 10% or so buffer, and you have the wattage you need.
So here’s the short story on 70 volt audio. Would you use it in a residential application? No – and that’s’ not what it was designed for. But in a commercial scenario it is typically the right choice and it can sound awesome when designed properly. Give us a call for help designing your next commercial audio system.