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Sonic beacon Loudspeaker Test Software

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Application Notes

 

 

 

PCI Sound Cards with Extended Frequency Response

An audio codec is responsible for the A/D and D/A conversion of the audio signals in sound cards. Although many audio codecs have responses from DC to 100KHz usually their frequency response is rolled off at both the low and high ends by the electronic hardware surrounding the codec.

Low cost cards roll off at the low end to increase dynamic headroom/reduce clipping problems on the little pc speakers which usually aren't equipped to handle low frequencies anyway. Sometimes unintentional bass attenuation is caused just because the analogue design has been made to be as cheap as possible and uses too small signal coupling capacitors.

Almost all older low cost sound cards roll off at 24KHz or below just because their maximum sampling rate is 48KHz.

In order to measure frequency response of an audio component a sound card with relatively flat frequency response of 20Hz to 20KHz is required. In order to measure ultra-sonic signal even higher upper frequency response is required.

The following table compares three PCI sound cards with balanced inputs/outputs and frequency responses extending from at least 20Hz to beyond 22KHz.

Parameter

M Audio Audiophile 192

 

ESI Juli@

Lynx 22

Sample rates

44.1, 48, 88.2, 96, 176.4 and 192 kHz from internal clock

44.1, 48, 88.2, 96, 176.4 and 192 kHz from internal clock

8 kHz to 200 kHz, including all standard rates with variable adjustment

Analogue I/O

two inputs and two outputs, balanced/unbalanced quarter-inch jack sockets, maximum input level +14.2dBu

two of each, either balanced quarter-inch jack sockets at +4dBu sensitivity, or unbalanced phono sockets at -10dBV sensitivity

two inputs / two outputs Electronically balanced or unbalanced, XLR connectors on L2Audio Cable +4 dBu nominal /+20dBu max. or -10dBV nominal / +6dBV max., software selectable in channel pairs

Digital I/O

S/PDIF in and out on phono co-axial, sync'able to external sample rates from 32kHz to 192kHz, supporting AC3 and DTS pass-through, plus MIDI In and Out.

S/PDIF in and out on phono co-axial, additional S/PDIF optical out, MIDI In and Out

one input and one output
AES/EBU or S/P DIF format, transformer coupled, XLR connectors on L2Sync cable

Converters:

AKM 5385A dual-bit delta-sigma 24-bit/192kHz (A-D), AKM 4358 multi-bit 24-bit/192kHz (D-A).

AKM5385A dual-bit delta-sigma 24-bit/192kHz (ADC), AKM4358 multi-bit 24-bit/192kHz (DAC)

24-bit, multi-level, delta-sigma

Input Dynamic range

113dBA (ADC)

114dBA (ADC)

117 dB, A-wtd specs measured at 44.1 kHz sample rate, 24-bit, card installed in computer

Output Dynamic range

109dBA (DAC)

112dBA (DAC)

117 dB, A-wtd. specs measured at 44.1 kHz sample rate, 24-bit, card installed in computer

Frequency response

±0.5dB, 20Hz to 80kHz at 192kHz sample rate

±0.5dB, 20Hz to 40kHz at 192kHz sample rate

< 10Hz - 92 kHz @ 200 kHz sample rate
< 10Hz - 46 kHz @ 96 kHz sample rate
< 10Hz - 23 kHz @ 48 kHz sample rate
(analog input to analog output)

 

Input THD + noise

0.0006 percent

0.0006 %

-108 dB (0.0004%) @ -1 dBFS
-104 dB (0.0006%) @ -8 dBFS
1 kHz signal, 22Hz - 22kHz BW

Output THD + noise

0.0023 percent

0.0006 %

-97 dB (0.0014%) @ -1 dBFS
-104 dB (0.0006%) @ -8 dBFS
1 kHz signal, 22Hz - 22kHz BW

Software Compatibility

Windows XP/2000/Vista, Mac OS X 10.1 and newer compatible

Windows 98SE/ME/XP/2000/Vista, Mac OS X 10.1 and newer, Linux (ALSA) compatible

EWDM driver: MME, DirectSound, ASIO 2.0 and GSIF 2.0 support

Windows 2000/XP/XPx64/Vista/Vistax64, Macintosh OSX: CoreAudio (10.4), Linux, FreeBSD compatible

MME, ASIO 2.0, WDM, DirectSound, Direct Kernel Streaming and GSIF support

Price

US$180, €116

US$190, €119

US$925, €596

 

 PCI Sound Cards with Replaceable Op-Amps

The sound cards shown below have swappable op-amps in common 8-Pin Dip packages (as below) configured in a balanced configuration on their line outputs.

 

You could use a SO-8 to 8-pin DIP adaptor such as the Brown Dog 970601 to replace the op-amp in your sound card with a high current SOIC op-amp such as the LMH6672. This amp can drive +4.8Vpeak into 25 ohms (200mA or 960mW) with a +6V supply. In a bridged configuration this would translate to +3.2V into 8 ohms or 640mW. In this case the distance from the loudspeaker to the measurement microphone could be reduced so that a lower audio interface output level can be used to drive the loudspeaker and still produce results that can be traced back to the 1Watt at 1 meter loudspeaker measurement standard. For a loudspeaker in a box, sound pressure level (SPL) increases 6dB each time the distance between the source and the measurement microphone is halved. The table below shows six possible scenarios. If your sound card can drive 640mW into an 8 ohm load reduce its input level so that it drives 500mW into the speaker and set the distance from the microphone to the driver to 0.71 meters. Reducing the distance between the driver and microphone too much reduces the time of arrival of the first floor reflection effectively cutting off the low frequency response of the measurement.

 

Power Available (Watts)

Current @ 2.83V (Amps)

Audio Interface Output Level (Vrms)

Output Level (Vpeak)

SPL Increase over 1 Watt

Distance to Microphone (meters)

2.000

0.706

4.000

5.66

+6.0

2.00

1.000

0.353

2.000

2.83

+0.0

1.00

0.500

0.177

1.414

2.00

-3.0

0.71

0.390

0.138

1.250

1.76

-4.0

0.63

0.250

0.088

1.000

1.41

-6.0

0.50

0.125

0.044

0.701

1.00

-9.0

0.35

 

Do your research and be very careful when attempting something like this.

 

Parameter

AudioTrak Prodigy HD2

Xonar HDAV 1.3 Deluxe

Auzentech  X-Fi Prelude 7.1

Sample rates

22.05, 32, 44.1, 48, 96, and 192KHz

24bit Playback

22.05, 32, 44.1, 48, 96KHz 24bit Recording

44.1K/48K/96K/192KHz @ 16/24bit

192 KHz @ 16/24 bit Playback

32, 44.1, 48 and 96kHz  @ 16/24 bit Recording

Analog Inputs

1 x 1/8” TRS unbalanced

Line-In/Mic-In 3.50mm mini jack

1 x MIC IN (mono)  unbalanced 3.50mm TRS jack

1 X LINE IN unbalanced 3.50mm TRS jack

 

Input

Op-Amps

 

TI RC4580, NJM5532

Both DMP8 Not replaceable

TI OPA2134 SOIC Soldered In

A/D Converters

AKM AK5353 24-bit, multi-level, delta-sigma

1 x Cirrus-Logic CS5381
(120dB SNR, Max. 192kHz/24bit)

1 x AKM-5394 high resolution 24/192 ∆Σ ADC

Input Dynamic range

114dBA

145dBA @ 48KHz

104 dBA

Input THD + noise

 

-108 dB (0.0004%) @ 1KHz

-90.9 dBA

D/A Converters

AKM AK4396 24-bit/192kHz

 

4 x TI Burr-Brown PCM1796 (123dB SNR, Max. 192kHz/24bit)

4 x AKM AK-4396 96kHz 24-bit multi-bit DAC

Output

Op-Amps

2 x OPA 2134 & 1 x JRC 5532, (Line Out)  All DIP8 Replaceable

2 x JRC 4580 (Headphone) Soldered In

 

JRC 2114D, LM4562

Both DIP8 Replaceable

unbalanced levels nom -10dBV (max +7dBV)

TI OPA 2134

National LM4562NA for Front L-R Replaceable

Analog Outputs

2 x unbalanced RCA phono jack

1 x 1/8” TRS Unbalanced (Headphone)

8 x unbalanced RCA phono jack

4 x unbalanced 3.50mm TRS jack

 

Output Dynamic range

110dB

145dB @ 48KHz

120dB

Output THD + noise

-92 dBA

-108 dB (0.0004%) @ 1KHz

(0.001%) @ 1KHz

Frequency response

+0.5dB  10Hz - 15 kHz @ 96KHz sample rate

+0.5dB  10Hz - 30 kHz @ 96KHz sample rate

+0.05dB 10Hz - 20 kHz @ 192KHz sample rate 24 bit

Digital I/O

Optical S/PDIF digital output following IEC-958C standard

 

Coaxial and High-bandwidth Optical Combo Output Connector. Supports 192KHz/24bit
Coaxial and High-bandwidth Optical Combo Input Connector. Supports 192KHz/24bit (Shared with Line/Mic In). HDMI1.3 - In/Out Type A *1

S/PDIF receiver and transmitter

Software Compatibility

Windows 2000/XP/XPx64/Vista/Vistax64

Windows Vista/XP(32/64bit)/MCE2005

Microsoft® Windows Vista™ or Windows XP (Service Pack 2, x64 or Media Center Edition)

 

Price

US$145, €103

US$210, €150

US$199, €142

 

Auzentech X-Fi Prelude Soundcard -- angled view

What We Do

Sonic beacon produces electrical and acoustical data acquisition and analysis software for the Windows operating system.

 

About Us

Sonic beacon is a Canadian organization founded in 1997. It is located in Pakenham Ontario which is near Ottawa, Canada. Ottawa is also home to the National Research Council of Canada's anechoic chamber, a key facility for acoustics testing. The chamber has been instrumental in the development of Canadian loudspeakers, hearing aids and microphone arrays.

News and Events

July 8, 2009:  Sonic beacon Version 1.1.0.6 released. Data-Logger can now save in .FRD and .ZMA file format. Data-Logger and Spectrum Analyzer can perform .FRD and .ZMA clipboard copy transactions. Signal generator can output signal complements on each sound card channel to allow bridging in many consumer audio interfaces. Module status bar shows current data type, FFT size and sample rate

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