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Monday, May 03, 2010

Audio-Technica Wireless Micrphone Systems At 41st Annual GMA Dove Awards

A-T 5000 Series wireless utilized by numerous performers as well as part of the mic setup for a gospel medley performance

Audio-Technica provided wireless systems for the 41st Annual GMA Dove Awards, recently taped live at Nashville’s Grand Ole Opry House and broadcast on the Gospel Music Channel (GMC).

Several featured performers used Audio-Technica Artist Elite 5000 Series UHF wireless systems paired with the AEW-T5400 cardioid condenser handheld transmitters, including co-host Bart Millard of MercyMe; Amy Grant, Francesca Battistelli; Jars of Clay, Tenth Avenue North, Red, Donald Lawrence, Phillips, Craig & Dean, Kari Jobe,  and Michael W. Smith.

A-T 5000 Series wireless was also used as part of the mic setup for a gospel medley performance, and additionally the house band used a selection of A-T hardwired microphones throughout the show.

Marc Repp served as the Audio Producer/Broadcast Music Mixer working out of MTV Networks’ Pegasus HD truck; White House, Tennessee-based Blackhawk Audio, Inc., provided the sound system with FOH (front-of-house) mixer Rick Shimer; and Bruce Bodor was the RF Audio Coordinator.

Bodor, whose credits involve wireless work for ESPN and CBS Sports, stated, “For this year’s Dove Awards, using Audio-Technica wireless systems, we experienced zero dropouts, which is always a great thing to be able to say. We had a wide variety of artists singing in different vocal ranges, and the A-T wireless systems performed flawlessly for all with great sound. There was absolutely no distortion, unlike some other wireless systems, and A-T’s wireless is also very user friendly. This adds another level of confidence for the performers, engineers and show producers.”

Audio-Technica Website

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Memphis Train Revue Mixes Live On A Laptop With Allen & Heath iDR-32

Allen & Heath iDR-32 Mix Rack and laptop to eliminate his front of house footprint

Memphis Train Revue, a 10-piece R&B/soul band based in Austin, Texas and audio engineer James Duvall have been utilizing a sound reinforcement system designed around an Allen & Heath iDR-32 MixRack connected to a laptop, eliminating the mixing console completely.

Memphis Train Revue is a high-energy show band that plays a lot of private events. “One of the things we specialize in is making things efficient and seamless for our clients. Everything we do can happen within the boundaries of the stage itself. Eliminating the mixing console frees up a significant amount of floor space, and that can be the difference in getting the gig, whether it’s a club, theater or ballroom,” says James Duvall of Creative Engineering & Solutions in Austin, who does both the house and monitor mixes for the band. “It saved us a lot of money, too.”

Duvall uses Allen & Heath’s iDR-32 MixRack, which provides all the inputs, outputs, processing and routing for the band.

“I love the fact that the iDR-32 gives me all that in a rack-mount box that I can literally hide under the stage. I don’t carry any outboard gear at all, and there’s no sacrifice in functionality,” he says. “When I was designing the system, I figured, why not push the envelope? Memphis Train Revue may be a cover band, but that doesn’t mean this can’t be cutting edge.”

Duvall’s core mixing setup consists of the iDR-32 and his 13-inch MacBook laptop. The MixRack case also contains the band’s Audio-Technica M2 in-ear transmitters and a Furman power station, making the mix totally self-contained.

The MixRack, which runs Allen & Heath’s Version 1.43 firmware, is connected to the computer using a Linksys Wireless-N router via a Cat5e cable.

“The router is actually Velcroed to the back of the MixRack, so I can set up anywhere. I can see all my inputs and outputs on the MacBook, color-coded just like I would have them on an iLive surface. And since I’m running untethered, I can set up anywhere; which is the whole point.”

Generally, Duvall mixes Memphis Train Revue from offstage, in the traditional monitor position. When he ventures out into the house, he leaves his laptop behind, controlling it from his iPhone.

“I run something called iTeleport Jaadu VNC, which is a virtual network control app. It’s basically a remote desktop client that lets me access my computer directly,” he relates. “It’s basically a viewer, but it also lets me ride faders and spin knobs. So when it comes to fine-tuning the room, I just carry my iPhone.”

To have the entire sound system capable of operating without consuming floor space has definite advantages to the band’s clients.

Theater venues can actually strike their house mix position and sell those seats, while corporate and wedding events can accommodate more guests.

In addition, set-up time is greatly reduced, as Duvall simply pulls up his in-ear mixes from saved snapshots, and connects to the house PA system with two XLR’s out of the left and right outputs of the iDR-32.

Duvall is convinced that he found the right solution with Allen & Heath’s modular MixRack design. “The iDR-32 makes it a totally professional solution,” he says. “There’s no compromise. We get the same sound that we would with the mixing surface. I feel like I’ve helped make something here, like we’re a step ahead of what’s going on.”

Ultimately, the motivation behind the setup was to make Memphis Train Revue a more attractive band to hire.

“This band is absolutely amazing, but this set-up gives us a huge competitive advantage,” notes Duvall. “When our manager tells the talent buyers that we are not going to exceed the stage, and that we don’t even need any storage space, it really opens their eyes.

“In fact, we actually got two recent jobs, in large part because of all the benefits the iDR-32 provides. So literally, using this iDR-32 is helping Memphis Train Revue to get more gigs and make more money. And that says it all.”

 

A&H iLive Website

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Waves Audio Ships SoundGrid I/O Card For Yamaha Consoles

Card enables direct connection to Waves' SoundGrid platform to run large numbers of Waves plug-ins with low latency.

Waves Audio is now shipping the WSG-Y16 mini-YGDAI SoundGrid I/O card for Yamaha mixing consoles.

The card affords live engineers the opportunity to more accurately duplicate the sounds of hit studio recordings through the use of Waves plugins.

Together with Waves SoundGrid Server, a Control PC, a network switch and an authorized iLok with SoundGrid-compatible Waves plug-ins, the WSG-Y16 enables Yamaha consoles to process 16 channels of audio with Waves plug-ins.

Additionally, the WSG-Y16 supports MIDI input, for remote plug-in control directly from the console or external control surface.

“We are delighted to add the Waves WSG-Y16 SoundGrid MY-card to the ever-growing list of cards for our digital consoles,” states Kevin Kimmel, Mixer Product Manager, Yamaha Commercial Audio Systems, Inc.

“The WSG-Y16 will allow the most desired third-party set of plug-ins available to be at the fingertips of the largest group of live sound engineers on the planet.”

“With the combination of the variety of plug-ins from Waves and the reliability of Yamaha consoles, we have high expectations for both the new card and the Waves SoundGrid Server.”

Waves Audio SoundGrid technology gives users the ability to run large numbers of Waves’ audio processors with low latency, using standard PCs via Ethernet, far surpassing the specs of dedicated DSP-based platforms.

Waves’ SoundGrid system takes advantage of the recent advances in both Ethernet and CPU technologies. With the introduction of the WSG-Y16 mini-YGDAI card for Yamaha consoles, Waves brings the networking and processing capabilities of SoundGrid functionality to the live sound realm.

Waves Audio Website

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Harman Professional Highlighting AVB At 2010 InfoComm With Seminars & Training Sessions

New AVB system to demonstrate the benefits of the technology with an emphasis on house of worship applications

Harman Professional will hold multiple training sessions and discussions throughout the upcoming 2010 InfoComm show in Las Vegas that focus exclusively on the AVB protocol.

The training sessions and discussion will take place at the Las Vegas Convention Center on separate days throughout the 3-day exhibition, while its new AVB system, which demonstrates the benefits of the technology with an emphasis on house of worship applications, will also be on display at the Harman Professional booth, number C6236.

The house of worship demonstration system features the three interconnected elements of Harman’s AVB system solution: next generation hardware, next generation software, and the next generation audio network.

The next generation hardware consists of a dbx SC Series digital matrix processors, Crown CT Series amplifiers with USP4/AVB installed, BSS Audio AVB wall plates, and the BSS Audio/Netgear Ethernet AVB switch.

The system is operated through next-generation software HiQnet System Architect version 2 with its new configuration and routing paradigms based on designing the system directly ‘into’ a floor plan of the venue; all audio running over the next-generation audio network, Ethernet AVB. 

Visitors to the booth will not only be able to experience the extrodinary simplicity of Harman’s AVB routing mechanisms, but also take real-time control of the system with System Architect’s new full-screen kiosk mode functionality.

“As more members of the professional A/V community begin to adopt AVB protocols, and the single A/V network standard becomes a reality, Harman Professional will continue to support and introduce new products that enhance the efficiency of A/V delivery,” commented Adam Holladay, Market Manager, System Development and Integration Group.

“It is important for us to educate our customers on the benefits of AVB, and we encourage anyone who is at InfoComm to come by our booth or seminars to learn more – particularly those connected with house of worship system design.”

The first public event, a training session entitled “Designing The World’s First Ethernet AVB Systems With HiQnet System Architect”, will focus on configuring an Ethernet AVB system with System Architect in a house of worship system design, and will take place on Wednesday June 9 from 2:30 pm - 4:30 pm at room N208. It will be hosted by a complete Harman Professional team, including Adam Holladay and Tom Cram for SDIG, Iain Gregory for dbx / BSS Audio, and Brad Benn for Crown.

The next event will be an AVnu Alliance panel - featuring representation from Harman International, and several other AVnu Alliance member companies - and will take place on Friday, June 11 from 10:30 am - 12:00 pm in room N219. The panel will discuss the new IEEE 802.1 AVB standards and how they affect the A/V community.

Harman Professional will also be showcasing its new AVB product technologies along with other members of the AVnu Alliance at the AVnu Alliance Pavilion at booth number C7934 throughout the show.

Harman Professional Website

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Swing House Synergizes Sunset Strip & South By Southwest With Soundcraft Consoles

With little time to spare between performances, reliability of the audio consoles was as important as sound quality

As it has done for the past three years, Los Angeles-based Swing House Productions provided live audio services and event production for performances at the Rusty Spurs club in Austin during the South by Southwest festival.

This year, however, Swing House made a change by drawing from its own audio inventory for the festival, deploying a Soundcraft Vi4 console for Rusty Spurs’ indoor stage and a Soundcraft GB4 console for a smaller stage in the outdoor area.

Starting out as a rehearsal studio, Swing House Productions has expanded into studio recording, rental department, full event production and artist development and management. The company’s work at South by Southwest is an extension of its relationship with the renowned Roxy music club in Hollywood.

“Each year at South by Southwest, the Roxy sponsors one venue in Austin and that venue essentially transforms into the Roxy for the week,” says Phil Jaurigui, President of Swing House Productions.

This transformation includes performances by artists who are synonymous with the Roxy. To wit, this year saw the likes of Tom Morello’s Street Sweeper Social Club, Minus The Bear, Michael Monroe of Hanoi Rocks, and Grace Potter and the Nocturnals. In total, Rusty Spurs hosted 112 bands over the span of five days.

Because Rusty Spurs does not normally feature live music, the onus fell on Swing House to not only set up a complete audio system, but one that would recreate the feel of the Roxy.

“Rusty Spurs is a regular bar with no stage and no PA, so we provided the PA, the backline, the staging and everything else that it takes to change a country bar into a rock and roll nightclub,” Juarigui says.

To that end, Swing House brought its Vi4 console from its Los Angeles headquarters to Austin for the week. The audio system also included JBL SRX728 loudspeakers and SRX718S subwoofers for the main stage, with powered JBL EON15 portable loudspeakers for the outdoor stage. Crown amplifiers power the audio system, which also includes system EQ from dbx.

“Tom Der of Soundcraft turned us onto the Vi4 last year when he rented it to use for South by Southwest and we loved it,” Jaurigui says. “We have our own now and we use it in our studio for rehearsals with everyone from Maroon 5 to Iggy and the Stooges.”

Sam Coy served as the primary sound engineer for the week, which required him to quickly and repeatedly switch bands over from stage to stage for 14 hours each day. With little time to spare between performances, reliability of the audio consoles was as important as sound quality.

“The attendance at Rusty Spurs was higher than it’s ever been,” Jaurigui says. “It was packed all the way through and while it was overwhelming at times, we didn’t have a single instance where either console went down.”

Moreover, Jaurigui notes that the Vi4 is not only easy to use, but also ideal for high-impact, high-volume performances. “The Vi4 is so intuitive where even if you’re only used to analog consoles you can pick it up quickly,” Jaurigui adds. “The sound is so clean and it’s very powerful and very punchy—you can really get that aggressive sound out of it that you need with rock acts.”

In addition, because the Vi4 packs so many features into a reasonably sized chassis, the transformation of Rusty Spurs into the Roxy was even more seamless. “There are so many built-in effects that sound great and it doesn’t take up much space for a fairly big console,” Jaurigui says. “Even in a small bar like Rusty Spurs, it fits comfortably. It looks great, too. All week, people were walking up to the console and were fascinated by it.”

Soundcraft Website

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Symnet Provides Console Free Control At St. Stephen Catholic Church

Multiple rooms are controllable via SymNet ARC wall panels.

Parishioners founded Saint Stephen Catholic Church in 1847 on the outskirts of what was then the frontier town of Milwaukee in the Wisconsin Territory.

Its first church survived until 1927, when a fire burned it to the ground, and its second church served the community from that time until the close of 2009.

In time for Christmas, Saint Stephen moved into a brand new structure that perfectly blends the rich aesthetic of its earlier buildings with a range of modern conveniences in a 1,000 plus-seat sanctuary.

Not least among those conveniences is a console-free, state-of-the-art sound system that delivers consistent, intelligible music and voice across multiple rooms in multiple configurations.

In cooperation with Scott Riedel & Associates, David Hosbach of DSH Audio Visions designed the system using Symetrix SymNet processing.

The classic church has a large gathering space leading into the nave, with an adjacent fellowship hall and church offices. The congregation knew that frequent large events would make use of all of those spaces in coordinated ways, ranging from simple overflow to more complex logistical timing of events among the spaces.

On the other hand, they also knew that the spaces would be frequently used independently. Simply put, they needed a sound system that could route audio from anywhere to anywhere.

“Although they were determined that they wanted the system to be incredibly flexible, they were equally adamant that they wanted it to be incredibly simple,” explained Hosbach.

“They didn’t want to have to contend with an audio console. They wanted to turn it on and have it go.” Hosbach designed the system, and Metro Sound & Video of New Berlin, Wisconsin installed it. Scott Riedel & Associates of Milwaukee designed and installed the acoustical treatments. 

Inputs to the system consist primarily of voice, chorus, and acoustic instruments, such as guitar, flute, clarinet, piano, which use distant mic’ing to provide general sound reinforcement. Both the Nave and the fellowship hall employ CD and iPod inputs for background music.

All of the mic lines go straight to the open-architecture SymNet DSP units, which perform all of the mixing, in lieu of a traditional console, in addition to the post-mix processing and loudspeaker conditioning.

Two SymNet 8x8 Express Cobra units combine to give the nave sixteen inputs and sixteen outputs and a single SymNet 12x4 Express Cobra gives the fellowship hall twelve inputs and four outputs. All three units interconnect via an Ethernet switch to provide coordinated routing across the entire church.

In addition to direct outputs from the SymNet Express Cobra units, a Symetrix 581E distribution amplifier feeds two eight-channel, 250W Electro-Voice CPS-8.5 amplifiers in the nave. S

ix Electro-Voice EVH1152/64 and two EVH1152/94 large format full-range loudspeakers cover most of the nave, with fourteen Electro-Voice EVID 6.2T compact surface mount loudspeakers supplementing under ceilings and in the narthex. Twenty Electro-Voice C8.2 coax ceiling speakers cover the fellowship hall.

System control is delivered by SymNet ARC wall panels. Four ARC-SWK and four ARC-SW4 wall panels expanded with an equal number of ARC-EX4 provide all of the control the church needs – and no more. They can mute or unmute all sixteen inputs, with some commonly-combined inputs conveniently grouped. The ARC-SWKs provide volume control. Complementary panels present routing options intuitively so that any area can listen to any other area at the touch of a button.

“I gravitate toward SymNet for three reasons,” said Hosbach. “First, I love the audio quality, which is extremely transparent. Second, installation and programming is a snap. The installer can hook the whole thing up with inexpensive Cat5 cable, and I can program a whole system like this in less than a day.”

“In fact, when I go in for tweaks, it often takes longer to boot up the computer than it does to get the system updated! If there is ever a question, Symetrix’ tech support is nothing short of outstanding. Whenever I call, I get to a human right away who is happy to walk me through whatever I need no matter the time of day.”

Alternatively, I’ve often simply emailed a file and received an answer with improved programming right away. The third reason is critical. All of the clients I’ve had over the years love the SymNet ARC remotes. They push a button and turn a dial and that’s it. The ARC controllers make complicated systems as simple to operate as a car radio.”

Saint Stephen Catholic Church is pleased with the capabilities and simplicity of the sound system in their new building. “If they decide they want to get a little more involved in the mixing down the road, the infrastructure is already in place,” said Hosbach.

“We can get them a touchscreen computer with a SymVue interface. That would truly give them a console without a console, again tailoring the depth of access to the needs of the church.”

Symetrix Website

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Mackie Launches New SRM1801 1000-Watt Powered Subwoofer

Designed specifically for the Mackie SRM450v2 compact full-range loudspeaker

Mackie has just debuted a new compact, powered subwoofer designed specifically for use with the SRM450v2 full-range portable loudspeaker - the SRM1801.

“We are excited to offer a powerful subwoofer for our best-selling SRM450v2,” remarked Greg Young, Mackie Brand Director. “It sounds great, it’s really easy to transport and, of course, it gets loud. Very loud.”

The SRM1801 subwoofer delivers 1000 watts of efficient Class-D power in a lightweight portable design.

The 18-inch woofer delivers superior output and active electronics include a precision crossover and tuning filters, providing amazingly accurate bass response.

The robust, solid-wood enclosure is covered with high-durability textured black paint and includes an integrated pole cup.

“It’s a powerful, plug-and-play solution for small clubs, DJs or anyone that needs massive low end.” concluded Young.

The Mackie SRM1801 powered subwoofer will be available worldwide in June, 2010, and will have a U.S. MSRP of $879.99.

It will be shown at the upcoming 2010 InfoComm Show in Las Vegas at Mackie booth #C7390 and demo room #N112.

Mackie Website

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Saturday, May 01, 2010

Amplifier Power Master Class: Not All Ratings Are Similar

How loudspeaker loads affect amplifier power output; how to compare power ratings of two different amp models; why to avoid 2-ohm operation; using bridge-mono operation to get more power; and the advantages of bi-amping

In designing a live sound system, you’ll come up with all sorts of questions, such as: One power amplifier is rated at 1,000 watts, and a different brand is also rated at 1,000 watts. Do they actually produce the same power?

Suppose you add more loudspeakers in parallel to a power amp output. Does the amp produce more power, less power, or the same? Does each loudspeaker have to handle more or less power as you add more loudspeakers?

To answer these and other questions, we need to explore the finer points of amplifier power ratings and loudspeaker loads.

In this article we’ll explain several concepts related to amplifier power:
(1) How loudspeaker loads affect amplifier power output
(2) How to compare power ratings of two different amp models
(3) Why to avoid 2-ohm operation
(4) Using bridge-mono operation to get more power
(5) The advantages of bi-amping

How Loads Affect Power Output
As amplifier data sheets show, an amp’s power output tends to increase as the load impedance in ohms decreases. You might see a spec of 400 watts into 8 ohms, 600 watts into 4 ohms, and 800 watts into 2 ohms. Why does that happen?

To explain, let’s start with the basics. As Ohm’s Law states, Current = Voltage divided by Resistance. The smaller the resistance, the higher the current. So low-impedance loads draw more current than high-impedance loads.

Here’s an example. When you play a 1 kHz tone through a power amp at a low level, it puts out a constant voltage, say, 20 volts. What is the current drawn by an 8-ohm, 4-ohm, or 2-ohm loudspeaker?

    Volts / Resistance = Current
• 20 volts / 8 ohms = 2.5 amps
• 20 volts / 4 ohms = 5 amps
• 20 volts / 2 ohms = 10 amps (assuming the amplifier can provide 10 amperes)

Power = Voltage x Current. So the three loads would receive this amount of power:
• 8-ohm load: 20 volts x 2.5 amps = 50 watts.
• 4-ohm load: 20 volts x 5.0 amps = 100 watts.
• 2-ohm load: 20 volts x 10.0 amps = 200 watts.

As you can see, the amplifier power doubles every time the load impedance is halved. That’s at low levels, where the power supply is not forced to produce much current.

What happens when you add more loudspeakers in parallel to a single amplifier channel?

See Figure 1. If you connect one 8-ohm loudspeaker to a power amp output, the load impedance is 8 ohms. In the example above, that loudspeaker receives 50 watts.

Now suppose you connect two 8-ohm loudspeakers in parallel to the same power amp. The total impedance seen by the amp is 4 ohms, so the amp puts out 100 watts, and each loudspeaker receives half that power, or 50 watts.

Now wire four 8-ohm loudspeakers in parallel and connect them to the same amp. The total impedance is 2 ohms, so the amp puts out 200 watts, and each loudspeaker receives 50 watts.

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So each loudspeaker gets 50 watts no matter how many loudspeakers you add in parallel. That means the SPL goes up as you add more loudspeakers to one power amp. Again, we’re talking about low levels where the amplifier doesn’t have to produce much current.

Imagine an ideal amplifier connected to an AC mains supply with unlimited current. This amp’s power rating doubles whenever the load impedance is halved. If an amp produces 400 watts at 8 ohms, it could do 800 watts at 4 ohms and 1,600 watts at 2 ohms.

In this ideal amplifier, the power supply’s DC voltage is constant no matter how much current is drawn from it. The supply could drive hundreds of loudspeakers in parallel with a total impedance near zero ohms. But real-word supplies can’t deliver infinite current. Nor can the AC mains or the output transistors – they would melt.

In a real-world power amp with limited current capability, the typical 4-ohm power rating is about 1.5 times the 8-ohm rating, not 2 times. And the 2-ohm rating is about 2 times the 8-ohm rating, not 4 times.

Most power amplifiers are rated for 4-ohm and 8-ohm loads, and high-end models can handle 2-ohm loads as well. A low-impedance load (like 2 ohms) is harder to drive – it draws more current – than a higher-impedance load (like 8 ohms). A “heavy load” means “a low-impedance load.”

Amps with puny power supplies run out of current when they drive low-Z loads. Amps with hefty power supplies can produce more current, hence more power, with low-Z loads.

Check the amplifier data sheet. It should specify how much power the unit can deliver into different loads. If the data sheet provides an 8-ohm and 4-ohm spec, but no 2-ohm spec, that means the amplifier probably can’t drive a 2-ohm load continuously without overheating or failing.

Comparing Amplifier Power Ratings
Let’s move on. Do two amplifiers with the same power rating produce the same power? Not always. Specifying amplifier power only in watts is insufficient.

A complete power rating includes several factors:
• Power per channel
• Number of channels driven simultaneously
• Load impedance
• THD
• Frequency range
• Continuous (long-term) power or peak (short-term) power

Here are a few examples. Suppose one amp produces 500 watts per channel at 0.01% THD. Another amp produces 500 watts per channel at 1% THD. Although both amplifiers could be called “500 watt amplifiers,” the first one will produce more power than the second when both are turned up to the same distortion level.

Or suppose one amplifier puts out 500 watts continuous, and another puts out 500 watts peak (but 250 watts continuous). The first one will sound clean at 500 watts continuous, but the second one will clip if forced to produce 500 watts continuously.

You need to compare apples to apples. 500 watts in one amp is not necessarily the same as 500 watts in another amp. Compare both amps at the same THD, at the same load impedance, at the same continuous power, and over the same frequency range.

Also, manufacturers vary in how conservatively they rate their products. Some companies underrate a unit’s power to allow for manufacturing tolerances – to ensure that all production units will meet the power spec.

Most amps produce a little less power when all channels are driven. That’s because the power supply voltage tends to sag when more channels are in use. Amps with dual independent power supplies don’t have that problem.

Avoid 2-Ohm Operation
Although some amps can handle 2-ohm loads continuously, it’s best not to operate the amplifier that way.

When a loudspeaker’s impedance is specified as 8 ohms or 4 ohms, this is the nominal or average rating. Actually, the impedance varies with frequency, so an 8-ohm rated loudspeaker might be 6 ohms at a certain frequency.

Four 8-ohm loudspeakers combined in parallel might be 1.5 ohms at that frequency, which is almost a short-circuit across the amp! The result is overheating and possible failure. That’s one reason not to apply a 2-ohm load.

Also, loudspeakers are reactive loads, not just resistive. They have inductance and capacitance. That makes some loudspeaker loads especially difficult to drive, causing more heat in the power amp. Top-quality amplifiers can drive these “difficult” loads with less distortion than lesser amps.

Running an amplifier into a low-impedance load makes the amp run hotter because low-Z loads draw more current. More current causes more heat dissipation in the amp’s devices. High heat tends to destroy transistors and should be avoided.

Because 2-ohm loads draw a lot of current through the loudspeaker cables, more power is lost by heating those cables than if you used a 4-ohm load. A 2-ohm load requires very thick loudspeaker cables to prevent losing power via cable heating.

What’s more, a 2-ohm load reduces damping factor compared to a 4-ohm load, so the bass and kick drum may sound less tight. That’s because damping factor = load impedance divided by amplifier output impedance. As the load impedance decreases, so does the damping factor.

Even if a power amp is claimed to drive a 2-ohm load at high power, I don’t recommend using a lot of loudspeakers to take advantage of that power.

Instead, consider a 2-ohm rating as the ability to handle 4-ohm loudspeakers whose impedance might dip to 2 ohms at certain frequencies. If you need more power, I suggest getting a second amp and more loudspeakers, which will also provide redundancy.

Bridging Power Amps
One way to get more power from an amp is to run it in bridge-mono mode. When you bridge a stereo power amp, you wire the load across the amp terminals in such a way to get more power than the two channels combined.

For example, a 200-watt stereo amp might produce 600 watts mono when bridged. Note that bridging is not the same as bi-amping.

Caution: Make sure the amp’s data sheet says that the unit can be run in bridge mono mode. If not, you may damage the amplifier. Some amps require a switch to be set to bridge mode before you apply power.

To bridge a stereo amp, enable its bridge-mono switch and connect one loudspeaker across the two red terminals of the two channels.

Figure 2 shows how to do it. The 2-channel signals are opposite in polarity in bridge-mono mode, and so the total voltage across the loudspeaker is twice the voltage of a single channel.

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In bridge mode, one red terminal becomes the positive polarity signal, and the other red terminal becomes the negative polarity signal. The manufacturer’s manual tells which terminal is which.

A bridged amp provides double the voltage of a single channel. That double voltage forces twice the current through the load.

So in theory, with 2X voltage and 2X current, you get 4X the power in bridge mode compared to a single channel in stereo mode.

Real-world amps provide something like 3X the power in bridge mode because the amount of current available is limited.

Bridged amps should be used with loudspeaker impedances that are twice the minimum rated impedance in non-bridged mode.

For example, if an amp is rated at 4 ohms minimum in stereo mode, the load for bridge-mono operation should be 8 ohms minimum. Avoid driving a 4-ohm load with a bridged amp unless the specs say that the amp can handle it.

Bridging a stereo amp effectively turns it into a mono amp. So if you want to use two loudspeakers in a system, you’ll need two bridged stereo amplifiers.

Feed each amp a single mono input signal. In a stereo system, you’d feed the left-channel signal to amp 1 and feed the right-channel signal to amp 2.

Because the output signals of a bridged amplifier are floating, you should not connect an amplifier output terminal to a grounded device. That shorts one channel and may blow the amp.

Bi-Amping
Here’s our final topic. A single amplifier-loudspeaker system uses one amplifier channel driving a loudspeaker with an internal passive crossover.

Operating at high power, that crossover filter sends the lows to the woofer and the highs to the high-frequency driver.

In a bi-amplified sound system, you use one amplifier for the woofer(s) and another for the high frequency driver(s). An active crossover sends the lows to one amp channel and the highs to the other amp channel.

Each channel covers a specific frequency band, not the entire audio range. With a single-amp system, one amplifier handles the complete audio range (Figure 3).

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Some systems can be tri-amplified, and some touring systems are four-way or five-way. They are the norm for high-power systems.

The advantages of bi-amplification include:
• Distortion frequencies caused by clipping the woofer power amplifier will not reach the tweeter, so there is less likelihood of tweeter burnout if the amplifier clips. In addition, clipping distortion in the woofer amplifier is made less audible because the woofer can’t reproduce high frequencies.
• Intermodulation distortion is reduced.
• Direct coupling of amplifiers to loudspeakers improves transient response – especially at low frequencies.
• Bi-amping reduces the inductive and capacitive loading of the power amplifier by a passive crossover.
• The full power of the tweeter amp is available regardless of the power required by the woofer amp.
• The active crossover can be variable frequency, so it adapts to a wide range of loudspeaker systems. It also lets you control the level and polarity of various drivers.
• The active crossover can have steeper roll-offs. This protects loudspeakers by keeping out unwanted frequencies.
• You omit the non-linear passive LF crossover used in passive loudspeakers. The result is higher sound quality.
• Peak power output is greater than that of a single amplifier of equivalent power.

Let’s explain that last advantage in more detail. Suppose you have an 800-watt single amplifier, and also a 600-watt LF amp and 200-watt HF amp as part of a bi-amped setup.

In general, you can get more volume – higher peak levels –  from the bi-amped system even though the two systems have the same total power. A loud bass note and a loud high-frequency note sounding simultaneously might clip the 800-watt single amp.

But since the bi-amped system is split into low and high bands, each amp is more likely to pass the signal without clipping.

As we’ve seen, there are many aspects of amplifier power to understand. The more you know about the nuances, the higher your skill level as an audio professional.

Bruce Bartlett is a microphone engineer (http://www.bartlettmics.com),  an audio journalist, and a recording enginee (http://www.bartlettrecording.com). He is the author of “Practical Recording Techniques 5th Edition” and “Recording Music On Location”.

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AVnu Alliance Hosts Second PlugFest & Announces Five New Members

New pro audio members include Audinate, Sennheiser

AVnu Alliance, the industry forum dedicated to promoting the adoption of the IEEE 802.1 AVB (Audio Video Bridging) standards and the related IEEE 1722 and 1733 for professional A/V, automotive and consumer applications, recently hosted its second PlugFest and added five new members.

With these latest developments, the AVnu Alliance continues to expand the adoption of the non-proprietary AVB standards and advance interoperability among AVB-enabled networked products.

“The member PlugFests are key to moving the AVB technology from paper to practice,” says Rick Kreifeldt, Chairman of AVnu Alliance and Vice President, Systems Architect at Harman International. “By implementing compliance test procedures to ensure AV devices work together, we continue our collaboration with member organizations to refine interoperability specifications and enhance the network backbone.”

The five new members that recently joined the AVnu Alliance represent diverse industry segments committed to reliable, low-latency, and high-resolution networking capabilities for a high-quality A/V experience.

The new members include: Audinate, creator of the Dante digital media networking technology; Micrel, global manufacturer of IC solutions; Sennheiser, manufacturer of microphones, headphones and wireless transmission systems; Universal Media Access Networks (UMAN), developer of the Universal Network Operating System; and University of New Hampshire Interoperability Lab (UNH-IOL), a third-party laboratory dedicated to testing data networking technologies.

Quotes from new members:

“Since our inception, Audinate has used standards to develop a complete IP-based media networking solution. AVnu Alliance’s goal for promoting interoperability and openness among A/V equipment vendors across the industry will give customers greater flexibility in implementing A/V networked systems.” - David Myers, COO, Audinate

“Micrel intends to leverage its innovation and market presence in the automotive and consumer electronics segments to proactively contribute as a promoter member to AVnu Alliance. As pioneers for automotive Ethernet with a strong track record in enabling connectivity for consumer entertainment devices including the digital home infrastructure, AVnu Alliance is aligned with our strategy.” - Wiren Perera, Director of Ethernet Products, Micrel

“A common and open standard that allows the use of computer networks for digital audio and video transmission will be a great benefit for our customers. Through AVnu Alliance, Sennheiser plans to support the implementation of compliance tests that ensure interoperability of future AVB-compliant products.” - Dr. Heinrich Esser, President Global Research & Development, Sennheiser

“UMAN is pleased and excited to be part of AVnu Alliance. As a network company we believed from the very beginning in media networks based on open standards. There is no doubt that AVB will change the industry quite radically in a very short time. With the netOS UNOS we are happy to contribute an easy migration tool for manufacturers towards AVB, plus a unified command & control solution.” - Juergen Scheuring, CEO, UMAN

“Compliance and interoperability are the cornerstones of the AVB technology. We are very pleased to bring UNH-IOL’s extensive real-word test lab experience to AVnu Alliance as a promoter member to help define and assist in forthcoming testing efforts.” - Bob Noseworthy, Technical Sherpa, University of New Hampshire InterOperability Laboratory (UNH-IOL)

AVnu Alliance Website

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