Frequency Response Measurement of Logitec LIC-iREC03P

There haven been a few requests regarding a recently released line input device called the Logitec LIC-iREC03P. To add to the frequency response measurements done previously, we decided to add this new device to the group. This measurement was made using an iPod Touch 2G. As before, the audio was routed through the phone using SignalScope Pro, and the measurement includes the response of the iPod’s headphone output. When compared to the previous measurements,  the Logitec has the lowest 3dB point of all the devices tested (around 5 Hz). One problem with this device is the availability. Currently, it appears to only be available from Japan. I was able to order it fairly painlessly from geekstuff4you.com, but your mileage may […]

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Measuring Loudspeaker Impedance with IOScope

Today, a new video, Measuring Loudspeaker Impedance with IOScope, was published on this site, as well as on the Faber Acoustical YouTube channel. The video is both a demonstration of IOScope, as well as a simple tutorial on measuring loudspeaker impedance. Although the video is largely self-explanatory, I thought it would be beneficial to include some further explanation and tips for those who are interested. The movie is essentially broken into four chapters and a similar format will be followed here. What is impedance? How is it measured? By a generalized version of Ohm’s law, we understand that voltage is equal to the product of electrical current and impedance. This means that electrical impedance is equal to the ratio of […]

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iPhone Microphone Frequency Response Comparison

With the advent of sound level meter apps for the iPhone OS (of which SoundMeter was the first) people began to ask, “How flat is the frequency response of the iPhone’s microphone?” Early testing indicated that the built-in microphone of the original iPhone was not a good candidate for sound level measurements, but that the iPhone’s headset microphone enjoyed a fairly flat response. Since then, additional iPhone models have arrived on the scene, each with its own set of weaknesses with respect to microphone frequency response. Additional Apple and third party headset microphones have also been introduced. At long last, some relevant frequency response measurements are presented here for the benefit of those who would really like to “see” how […]

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iPhone Line Input Frequency Response Comparison

Although I already listed some options for getting line-level audio into an iPhone or iPod touch, that list didn’t include much information that would suggest which option would be best. One important metric that people frequency ask about is frequency response. Well, I finally have some frequency response comparisons available to help answer that question. These measurements were made of various dock connector devices, attached to an iPhone 3GS. As in other frequency response measurements, the audio was routed through the iPhone, with a little help from SignalScope Pro. This means that each measurement includes the frequency response of the iPhone 3GS headphone output. The tested devices include: Tunewear Stereo Sound Recorder for iPod Alesis ProTrack Griffin iTalk Pro MacAlly […]

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iPhone Dock and Headset IO Frequency Response

People often ask about the frequency response of iPhone and iPod touch audio inputs. To shed some light on the issue, I made some frequency response measurements of the iPhone, iPhone 3G, iPhone 3GS, and iPod touch 2G with Electroacoustics Toolbox and an Edirol FA-101 audio interface. These measurements are broken into two groups, one for headset input and one for dock connector input. Since measurements were made by routing audio through each iPhone OS device (by way of the Audio Play Through function built-in to SignalScope/Pro), all measurements include the frequency response of the headphone output in addition to the response of the selected input. The frequency response of the Edirol FA-101 was removed from the measurement, using a […]

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iPhone Headset Input Options

One of the most obvious ways to get analog signals into an iPhone or 2nd generation iPod touch is through the headset connector. Several options exist for getting acoustic or electric signals into the headset input, which are discussed below. Any of these options will work with the iPhone, iPhone 3G, or iPod touch 2G. The original iPod touch does not have a headset connector with a mic input channel, so it is left out of this discussion. When making a decision about what to use the headset input for, or what to connect to it, you may want to take a look at the frequency response measurements of the various iPhone OS devices. Acoustic Signals Acquiring acoustic signals requires […]

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Dock Connector Audio I/O

Several options exist for getting audio signal into and out of iPhone OS devices via the dock connector. However, not all accessories are compatible with all iPhone OS devices. So, we put together this compatibility chart, based on our own tests with SignalScope/Pro and SignalSuite. Dock Audio Accessory Compatibility These devices were chosen for their ability to accept stereo audio input from external sources. Some dock connector devices simply feature built-in microphones, which are of limited use for test and measurement applications. It’s also important to remember that the iPhone OS automatically selects the current route for input audio signals (built-in mic, headset, dock connector, etc). iPhone iPhone 3G iPod touch iPod touch 2G Alesis ProTrack In/Out(1,2) In/Out(2) Out(3) In/Out(2) […]

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