Coaxial monitors present known challenges, both technical and sonic (the latter because our ears had become accustomed to silk tweeters and fourth-order crossovers, not coaxial horns). How we address these challenges in a new era? By designing monitors that incorporate serious DSP.
Equator studio monitors have an incredible amount of internal DSP control that allows us to match transducer output at the assembly line so that every speaker built within a model delivers a matched response. This is vital in achieving accurate imaging.
In speaker manufacturing, no two transducers come off an assembly line exactly alike. Ever.
In speaker manufacturing, no two transducers come off an assembly line exactly alike. Ever. Most professional speaker companies pass a transducer if its performance is within +/-2 dB of spec. That means that at the end of the transducer assembly line, the speaker is swept for its frequency response, accurately revealing its response from 20Hz to 20kHz. A line is placed above 0 at +2dB and one is placed below 0 at -2dB. If the average of the peaks and dips is greater than + or- 2dB, then that transducer makes its way into the trash. If the average is less than +/- 2dB, into production it goes. Some manufactures adhere to a lower tolerance. As such, they are throwing away fewer speakers so they can charge less for the end-product. The greater the average +/- spec, the worse the imaging will be during use.
Even with two passed transducers at +/- 2 dB, you can wind up with a left/right pair having a +2 dB peak on one side and a -2 dB dip on the other. That is a 4dB problem. Because speakers cannot be matched during the transducer manufacturing process, the answer is to match them inside the speaker cabinet using DSP. We've put the power inside each unit to do just that.
Each of our transducers are digitally adjusted not only to compensate for manufacturing tolerances, but also to precisely match its output performance with that of every other transducer within a system, from stereo through 8.2 setups. We adhere to the pro standard specification of +/- 2dB but we go much further.
We match output for every speaker of the model which ensures dead accurate imaging.
When an Equator transducer passes the initial frequency tolerance and moves to the next production phase, the frequency response data, the detailed peaks and dips across the 20Hz to 20kHz range (its DNA) is captured. When that transducer makes its way into a cabinet, the response information (the DNA) of that particular transducer is then loaded into its individual amplifier system via a back panel data connection. The internal DSP recognizes it as transducer information and assigns a host of filters to ensure that this particular unit deliverss corrected, uniformed output. To put it simply: at Equator we digitally match every Q10 with every other Q10 or every Q12 with every other Q12 or every D5 with every other D5 etc. We match the output for every speaker of the model which ensures dead accurate imaging.
Impact of Serious DSP
The impact of incorporating serious DSP into the Equator Audio studio monitors was immediately apparent in the overall development process. In the pre- Equator days, a sample transducer would be developed along with an amplifier, cabinet, crossover, port tube, and so on. The design would be tested and a review of the measurements would direct changes to fix whatever problems were seen. The main test was done with a MLSSA Measurement System. The prototype speaker was placed in the center of a huge wooden baffle with the exact size for the prototype cut out of the center, creating a huge wall around the unit. A test microphone was positioned exactly 27 feet from the center of the speaker. The computerized test would be run and would reveal a graphic display of the audio pointing out the problems that existed.
Each revision created new unforeseen problems which meant new components would need to be redesigned and manufactured to address those problems
In order to improve the results a change in the design was necessary. Each change required new prototype components, which meant waiting for new samples to be designed and manufactured (usually 8 weeks or so), then taking the old speaker system apart and reconstructing it with the new components. Each revision created new unforeseen problems which meant new components would need to be redesigned and manufactured to address those problems, another 8 week wait for new samples, another reconstruction, and another test. So on and so on and so on. It was like trying to get your hands around jello. One problem gets fixed and another problem would develop. After a long series of design changes and compromises a good product would emerge. It was a long, laborious process.
Fast forward to spring 2007. A prototype Q12 studio monitor equipped with our coax transducer and internal DSP was taken to a prominent acoustic test lab which was originally built for NASA in the 40s. This lab had become a premier test lab and houses one of the largest anechoic chambers in the United States. A Q12 was placed in the chamber and bolted down to a table; an arc of 19 microphones, each spaced successively off-axis in 5-degree increments, hovered above exactly 27 feet from the Q12 compression driver horn. A test signal was sent through the Q12, the readout was analyzed.
With a laptop and a new set of coefficients based on the test results, new code was downloaded via USB into the Q12, where the monitors on-board CPU made adjustments. Multiple times, back and forth from control room to chamber retesting. More analysis, more code. The Q12 never left the table. The readout at the end of the day: flat both on axis and off. In one afternoon we accomplished what used to take many months.