In this application note we calculate the maximum output level and noise level produced by an amplifier/loudspeaker combination.
This application note can serve as an example for calculating the maximum sound pressure levels and noise output levels for any amplifier/speaker combination.
At the 143rd AES conference in NYC, we demonstrated two Benchmark AHB2 monoblock power amplifiers driving a pair of 4-Ohm PMC MB2S studio monitors.
We were extremely impressed by the unusually clean, distortion-free, output of these monitors. They fully compliment the distortion-free performance of the AHB2 to provide a system with outstanding clarity while delivering high sound pressure levels.
In this application note we will calculate the peak SPL produced by this system. We will also calculate the acoustic noise at a distance of 1 meter from each monitor. We will also discuss some of the unique design features of the MB2S monitors that contribute to their impressive performance.
Speaker sensitivity is a measure of how loud a speaker will play at a given input power or at a given input voltage. Sensitivity is normally measured with a 1 watt power input or a 2.83 Vrms voltage input.
There have been many different speaker designs over the years and there are vast differences in speaker sensitivity. The speakers below have sensitivities ranging from about 85 dB to 109 dB.
In this application note we calculate the maximum output level and noise level produced by an amplifier/loudspeaker combination. Use this example for calculating the performance of your system.
At the 141st AES conference we demonstrated two Benchmark AHB2 monoblock power amplifiers driving a pair of 4-Ohm PMC IB2S studio monitors. These monitor are also available the PMC IB2SE hi-fi version.
In bridged mono, the AHB2 can deliver over 518 watts into each of these 4-Ohm speakers. This is a perfect match to PMC's 500 watt recommendation. The AHB2 easily provides the power, the output current, and the damping required by these low-impedance speakers.
"I am very impressed with the clarity and accuracy of these outstanding professional monitors. The Benchmark AHB2 and PMC IB2S are an absolutely killer combination!" - John Siau, VP, Benchmark Media Systems, Inc.
In Benchmark's listening room we recently demonstrated the importance of the first watt using two 100 watt stereo power amplifiers. One amplifier was a traditional class-AB amplifier, the other was Benchmark's AHB2 power amplifier with feed-forward error correction. Using a double-blind ABX test, we verified that there was a clearly audible difference when the amplifiers drove speakers at an output level of 0.01 watt.
"Switching supplies are noisy."
"Linear power supplies are best for audio."
About 5 years ago, Benchmark stopped putting linear power supplies into our new products, and we replaced them with switching power supplies. We did this because linear supplies are too noisy. Yes, you read that correctly, linear supplies are noisy!
A well-designed switching power supply can be much quieter than a linear supply!
Find out why!
Benchmark has created a bi-directional 12 Volt trigger interface that is compatible with almost every trigger input and output. This interface can be used to connect Benchmark products together so that they will power up and down in a sequenced fashion. This same interface can be connected to the trigger inputs and outputs on other brands of audio products. This application note describes some typical configurations and it includes the full technical details of the Benchmark bi-directional trigger system.
This short 8-second video clip demonstrates some of the differences.
The following measurements and scope photos demonstrate the effectiveness of the feedforward system in the AHB2.
From the first Watt to the last Watt, the AHB2 shows no evidence of crossover distortion. In contrast, all conventional class-AB amplifiers have crossover-distortion artifacts.
Dick Olsher once said that "the first Watt is the most important Watt". We agree!
Most audio power amplifiers suffer from a defect known as "crossover distortion". This distortion is particularly troublesome at low output levels. At low power levels, the crossover distortion can rise to a high percentage of the output level and become the dominant source of distortion.
There are two distinct types of audio products. Some audio products are designed to be transparent while others are designed to provide a euphonic experience. These types are as different as a Porsche and a Cadillac. There is not a right and wrong type of car. Likewise there is not a right and wrong type of audio product. The choice belongs to the user, but the user must be fully aware of the differences before they buy.