It does not get there by just winning several industry awards or even by being particularly amazing at what it does, although both of them certainly won't hurt. Having gear that is branded as an industry standard is immeasurably hard to come by. Despite the major departure from the original objectives, his initial ambitious quest for the absolute best in quality, reliability, clarity, and accuracy can be seen in all of Earthwork's products to this day, especially the Earthworks M30. After Blackmer's unfortunate death in 2002, the company decided to focus on mics and preamps and stopped making the Sigma 6.2 speakers. Blackmer's dream of the ultimate audiophile's loudspeaker was realized eventually, after many many years of research, with the release of the Earthworks Sigma 6.2. Soon after that, the OM1 omnidirectional measurement mic was born.Įven though this new mic was initially meant as just a means for Blackmer's true goal of a better loudspeaker, he was persuaded by his colleagues to design other mics. A new standard in measurement tools would be needed to be created if he was to come close to the results he knew was possible. It was actually during the initial design states of the dream speaker that he realized that the measurement tools which he was using, tools considered to be the world standard at the time - were just not good enough. It started with company founder David Blackmer and his lofty goal of creating the absolute best loudspeakers possible. Interestingly enough, Earthworks Audio, the brand behind the Earthworks M30, did not start off as a mic designer and manufacturer. However, the big chiefs in the industry say you need to get the mic away from the speaker for appropriate wavefront formation in the low end so it can be far field.The Earthworks M30 Microphone is essentially a precision engineered 30kHz omnidirectional measurement mic that is ideally suited for acoustic measurements, including loudspeaker design and quality control, troubleshooting and sound system setup, room acoustic, or any application where accurate free-field measurement mic is required. The closer your mic is to the speaker and the higher the speaker is off the ground, the longer the gate you can have. You'll be able to get a longer time period/cleaner measurement from higher directivity speakers as the reflections won't be as powerful. At 3 milliseconds your resolution becomes 333Hz or roughly 350Hz.
This limits your lowest frequency measured and resolution to 166.67Hz. Let's say after you do your Pythagoras, a 6 ms gate is given(which would be excellent for in home).
Frequency Resolution of your gated frequency response = 1/Period(Gate). Sound travels at about 1ft per ms or 1 meter per 3 ms. The time difference between the arrival of the direct sound and first reflection is how you set your gate (reflected time-direct time=gate length). There are 2 right triangles in the pic above, just draw a straight from the midpoint to the floor and use it as 'A' or 'B'. The triangle in the top picture is the key to the math though the above(impulse) method is more useful-Pythagoras is your friend. You can try the same thing for any speakers you would like, but there are other ways as well. As you look at the frequency response graphs and how they are gated, you can see the impact of the time and amplitude of the reflections shown in the spectrogram at that gate setting. So the longer the gate, the more detailed your gated measurement. Gating not only removes room reflections, but also the amount of data points in the measurement. In the spectrogram you can see not only the timing and frequency of the reflections, but their amplitude as well.
In the impulse you can see where the major, high amplitude reflections come into play just after 6 ms, but the spectrogram makes things a bit clearer if a bit less absolute. You can essentially close the gate on the reflection trying to get into the graph. The frequency responses at your left were achieved by various levels of gating using either the impulse or the spectrogram to discover where the room reflections enter the response. In order to do that you need to see what is speaker generated and what is boundary/room reflection generated. Since sound has a time element to it-it is a temporal thing, we'll have to look in the time domain to separate it out. IOW, remove the reflections out of the visible frequency response measurement. You need a pseudo-anechoic measurement, but how does one make a pseudo-anechoic measurement? Eazy Peazy, you have to gate out the room reflections. So you want to get a nice clean measurement to design a speaker or measure a speaker you already have and you don't have an anechoic chamber at your disposal.
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