What Every Residential Integrator

Needs To Know About 70-Volt Systems

P R E S E N T S

NEAR is a Division of Bogen Communications, Inc.

• Typically 70V systems have poor sound • Usually found only in commercial

settings • How did 70V get that reputation? - It earned it - Most 70V installations use cheap speakers & transformers

70V – A Bad Reputation

Why You Need To Know About 70V

• 70V systems can sound better than you think • Easier to install multi-speaker 70V systems than low-impedance systems • Can overcome coverage problems with sound “sculpting”

• Amplifier outputs constant voltage (70V) - Similar to power grid - Minimizes power loss

How 70V Works

NEAR 6XL - 600W Power Amplifier

How 70V Works

Transformer on the speaker steps down voltage just like the transformer outside your house steps down high voltage AC grid power

How 70V Works

• Transformers can be built-in or… • Added to any low-impedance speaker • Power taps select maximum

power going into the speaker

70V Benefits • Less power loss over long wire runs

A55footlengthof16-gaugespeakerwirewilllose21%ofavailablepowertoa4-Ohmloadspeaker.Thesamespeakerina70Vsystemcanbeona2687footwirebeforelosingthesame%ofpower.InpracHcalterms,thereisvirtuallyzerospeakerwirepowerlossin70Vsystems.

First 70V Benefit • You can hook up more speakers to an amplifier channel

• Why do you need more speakers? - More even sound coverage

Two Medium Directivity (120° dispersion) Speakers Cannot Uniformly Cover a Large Outdoor Area

Four Medium Directivity Speakers in a Large Outdoor Area – Better Coverage

Six Medium Directivity Speakers in a Large Outdoor Area – Even Better Coverage

• Most installers wire multiple speakers in parallel • System Impedance (X) = 1/(1/R1+1/R2 +1/R3, etc.)

Two 8-Ohm speaker example: X = 1/(1/8 + 1/8) or X = 1/(.125 +.125) or 1/.25 = 4 Ohms

• Fine for two 8-Ohm speakers, but what if you need more speakers to achieve uniform sound coverage? • And then there is…

Typical Wiring

• It is not constant • It’s usually lower than you think • Can increase the odds of amplifier failure due to low impedance of speakers wired in parallel

The Dirty Secret About Impedance

Nominal8-Ohmspeakersarenot8-Ohmsatmanyfrequencies

• Use more amplifiers - expensive • Series/parallel wiring (illustrated at right) can get the impedance right but is inconvenient to wire speakers to each other

Alternative Solutions

• Can run many more speakers off an amp channel – safely & reliably

70V – A Better Solution

70V – A Better Solution

DiningPool

DesiredSPL:+9dB

DesiredSPL:0dB

BBQPit

DesiredSPL:+6dB

Sound Sculpting

+--

50 Watt Amp

16W = +9dB 8W = +6dB 4W = +3dB 2 W = 0dB 2 W = 0dB

Doubling power = +3dB

Total power = 32W.

Do not draw more power than 90% of total available power.

Sound Sculpting

70V Configuration

• Negligible power loss over long wire runs • Can run more speakers off an amp for more uniform sound coverage • No low impedance and amp failure worries • Sound sculpting puts the right amount of volume in each area • But miracles come at a cost…

70V Benefits Summed Up

70V Downsides

• Cheap transformers sound bad –  Easily saturated = distortion –  Severe roll-off of lows

and highs

• Even good transformers roll off bass

70V Downsides

30Hz

Data Measured: Jun 30, 2015 Tue 3:45 pm Data Measured: Jun 30, 2015 Tue 3:42 pm

Person: Company:

Project: File: IG8.lib

Jun 30, 2015Tue 3:49 pm

4.6.0.371May/29/2007

Notes

Map

92: 8 ohms (low impedance)94: 70V (high impedance) 8W Tap

9K Hz 10K 20K

dBSPL

50

55

60

65

70

75

80

85

90

95

100

105

110

SPL vs Freq

• Even good transformers roll off highs

70V Downsides

10kHz

• But these 2-3dB losses at frequency extremes are not musically significant compared with the benefits

70V Downsides

Data Measured: Jun 30, 2015 Tue 3:45 pm Data Measured: Jun 30, 2015 Tue 3:42 pm

Person: Company:

Project: File: IG8.lib

Jun 30, 2015Tue 3:49 pm

4.6.0.371May/29/2007

Notes

Map

92: 8 ohms (low impedance)94: 70V (high impedance) 8W Tap

9K Hz 10K 20K

dBSPL

50

55

60

65

70

75

80

85

90

95

100

105

110

SPL vs Freq

• Running subwoofers at 8-Ohms and mid/high speakers in 70V mitigates potential bass loss of 70V transformers. • To do this run 70V on one channel and low impedance on the other • Use a direct drive (no output transformers) power amplifier

Hybrid Systems

Hybrid Systems

• 70V Pros - Allows longer speaker wire runs - Allows use of smaller gauge speaker wire - Allows many speakers to be run off of each amplifier channel without endangering system reliability - Allows “sound sculpting” – different volume for each speaker

• 70V Cons - Higher distortion (with low quality transformers or when high quality transformers are over-driven) - Low frequency roll off - High frequency roll off (with low quality transformers) - Variability (low quality transformers)

Summing Up