The CoLine Audio System is an integrated package consisting of the Full Range CoLine Loudspeaker System and if desired the matching CoSub low frequency cabinet, Power Amplification, Digital Signal Processing, and proprietary DSP configurations.



The Coline Audio System is a coaxial, coincident, and phase coherent sound source that distributes a true cylindrical wave front from 120Hz to 18KHz. Its overall frequency response without subwoofer is 45Hz to >20Khz

The integration and positioning of driving elements, acoustic treatments, and the unique crossover design and signal processing creates a system that reassembles the electrical audio signal into an acoustic signal that is the most accurate reproduction capable of any loudspeaker on the market today.

The high degree of horizontal pattern control provides even room coverage. The very narrow and controlled vertical coverage from 120Hz to above 16Khz minimizes room reverberation. The lack of a "crossover notch" means that everyone within the CoLines coverage hears the same accurate reproduction. The narrow cylindrical vertical coverage makes the room sound smaller and more intimate than it actually is.

The minimal phase response and group delay contributes to an unprecedented impulse response that covers the entire audio spectrum, not just one particular band. Voices sound natural and music retains its dynamics as if you were hearing it without sound reinforcement. Since the drivers are in temporal and electrical alignment, the system appears louder because all frequency components are reproduced simultaneously. The true line behavior carries sound to the back of the room with incredible accuracy and without overpowering those near the stage.



Almost every loudspeaker system on the market today splits the reproduced sound into frequency bands that can easily be handled by the driver for that band. These drivers occupy different positions in space, time and phase. The crossovers used to divide the electrical signal introduces frequency dependent phase shift and group delay. Each frequency range is handled by a driver and directivity control device (horn) that differ in angular coverage vs. frequency for their range. All of these elements prevent this common type of loudspeaker system from ever achieving the goal of accurate acoustic summation of all devices. Frequency response is compromised at some angles in the vertical coverage for vertically stacked drivers of multi-way loudspeakers and the impulse response is flawed everywhere because of the crossover design.

A close inspection of a conventional loudspeakerís manufacturerís data sheets will always show a deep notch in the frequency response around the crossover frequency (s) at vertical angles other than 0 degrees. Some of these notches exceed 15 db at a typical 1.5Khz crossover frequency. which happens to be  right in the center of the frequency range most important for speech reproduction and intelligibility. This compromise alone should render this loudspeaker system useless, but it has not. It is hard to imagine using a loudspeaker that creates such a problem, and baffling to us why a loudspeaker of this type continues to be used in light of this grievous flaw.

If this has not caused you to question the utility of this type of multi-way loudspeaker system, a closer inspection of the phase response and group delay and itís implications for the acoustically reconstructed audio signal certainly will.

At first glance, phase response seems like a difficult to understand and perhaps insignificant performance parameter. In reality, it is very important. It is the phase response and group delay response that demonstrates how well a loudspeaker reassembles the electrical signal into an acoustic signal.

We do not often think of this aspect of loudspeaker performance because it is rarely discussed or revealed by manufacturers. This is likely to be because the phase response and group delay response is typically so poor that the manufacturer really would not want this performance parameter scrutinized. After this discussion, I hope the reader will understand how important these performance parameters are, and how they affect intelligibility. The result is that there are many more listeners in areas of compromised sound reproduction than in areas of flat power response. Remember that anyone sitting in an area other than 0 degrees vertical relative to a speaker system with vertically aligned components is listening to a loudspeaker with a notch in the response. The more off-axis vertically a listener is, the deeper and wider the notch is. This should make you begin to wonder why anyone would use this type of loudspeaker.

You might think that a coaxial speaker configuration is the solution, and you would be partly correct. However, most coaxial speakers also have their share of flaws. Problems stem from the phase response and group delay of the crossovers implemented along with diffraction around the central HF device. There is one manufacturer of coaxial loudspeakers that gets it all correct. Unfortunately, the application of this loudspeaker requires it to be flown above the audience to provide even sound coverage. Our device, the CoLine, solves this problem without the need to be flown. This has a number of advantages. Installation costs are minimized. The sound originates in the same plane as the acoustic source, thus better preserving the acoustic image of the amplified sound. A cluster of loudspeakers pulls the acoustic image above the stage or area of sound origination, thus skewing the acoustic image to above the sight line. This skewing becomes more severe for those listeners nearest the stage or platform. For those in the front row, the sound comes from almost directly overhead.

Sound reinforcement systems exist to amplify speech, music and sounds. The goal is to reproduce as accurately as possible those sounds that listeners could not otherwise hear without amplification.

When a microphone is placed in front of a sound source, the goal is to capture the sound, amplify it, and deliver it to the listenerís ears exactly as it occurrs acoustically. The microphone, being a single diaphragm captures the acoustic source exactly as our ear would hear it. The electronic amplification chain reproduces the signal rather accurately (sans filters) and the loudspeaker attempts to convert this electrical signal into an acoustic pressure that is identical to the sound which the microphone picks up. Here is where the accuracy falls apart: The displaced transducers and the crossover network destroys the integrity of the original acoustic signal. The transducerís misalignment in space creates a situation where different frequency bands reach the listener at different times. While the manufacturer may provide delay and physical separation of the reproducers to sum on axis 0V-0H, off axis vertically there exists anything but a flat frequency response. This is due to the comb filtering between devices. The depth and width (Q) of the notching is a function of the crossover filter frequency, spacing and slopes. We all know and understand the concept of comb-filtering and notching, but I am presenting it as only one the flaws in a typical loudspeaker system that degrade its ability to acoustically reconstruct the electrical signal it is given.

Now we will talk about phase response and group delay and try to make it understandable. Phase response and group delay is the effect of a filter whereby a frequency is delayed in the time domain due to the action of the filter. The amount of phase offset and group delay is a function of frequency and filter type or slope.

What does this mean? Some frequencies arrive at the listenerís ears at a different time than other reproduced frequencies and the amount of arrival delay is dependent on frequency. Every frequency arrives at the listenerís ears at a slightly different time. This is referred to as time smear. As an example, let us use a snare drum as our sound source. When the snare drum is struck, a burst of noise is created. This noise contains a very wide spectrum of frequencies. (Look at it with an RTA and you will see every band jump up with each snare hit) When a typical loudspeaker system reproduces the sound of the snare it is time smeared enough that it does not exactly resemble the sound that one would hear if one were listening to the actual snare drum without amplification. No amount of equalization or signal processing can correct this problem.

This time smear affects all reproduced sound, most importantly speech. The effect of this time smear is that our ear-brain interface must work harder to understand the spoken word. When using the CoLine system and some others loudspeakers that implement crossover and driver arrangements intended to eliminate this time-smear problem, there is a much better understanding of the spoken word. Listening and understanding becomes much less fatiguing. Some listeners have described the effect by saying "the sound gets into my head faster". Regardless of the description, all agreed that the sound reinforcement was significantly improved.

Another advantage of this loudspeaker system is itís reduced susceptibility to feedback. Because there is not a single point source, the total acoustic output is distributed along the length of the array. Since the CoLine is coherent, coaxial, and coincident, itís on and off-axis behaviors are equally well behaved. Gain before feedback characteristics are also much improved. As much as an extra 10 db of gain before feedback has been observed during live productions. For theatrical and musical performances this means that foot microphones, hanging microphones and wireless microphones can be operated at much higher sensitivities and levels compared to conventional loudspeakers. Equalization beyond voicing is not required. Tricks such as Feedback Eliminators can be dispensed with, perhaps sold on Ebay!

Less Is More

Today we see more and more line array systems being applied to acoustically inhospitable venues. While this approach is possible for very high-level concert sound reinforcement, multiple loudspeaker systems would be required to achieve a high volume level. This approach does carry the consequence of degraded audio due to the multi-path comb filtering and the phase response and group delay of the crossover topology used.

For most events that require sound reinforcement, a CoLine Audio System is all that would be needed. If extended low frequency output is required the companion CoSub can be added.

The Coline itself has a frequency response that extends down to 45Hz, -3db. The output of the CoLineís low frequency section is output matched to the mid/high section allowing at least 6 db more output capability than the mid/high section. In an auditorium that has rear seating 100í from the CoLine location, outputs over 105db are achievable at the rear of the auditorium.

Adding the CoSub extends the low Frequency reproduction to 22 HZ. A combination of box tuning and inverse shifted low-pass filtering provides stunning Low Frequency Reproduction. Again, the crossover topology and filter implementation make the added subwoofer section work with the CoLine to provide a coherent audio signature that is devoid of the typical peaks or dips in frequency response. You do not have to be resort to tricks such as inverting the phase of the woofer section to eliminate the notch in frequency response that occurs with typical systems. We can provide DSP's with configurations that allow the subs to be fed from an auxiliary send so that only those inputs will have the added benefit of the subwoofer. Unlike most aux send subwoofer configurations, no interference notch exists at any frequency as subwoofer level is added. Only additional XLF output is added.

Because the Coline Audio System can cover from front to back so well, under balcony loudspeakers may not be required. This is important because this can reduce the cost of an installed sound system.

Balcony coverage is also easy to implement. Just like the ground floor coverage, all listenersí ears need to be between plus or minus 5 degrees vertical relative to the loudspeaker's direct on axis aim point. If the slope of the seating is significant, simply stack two or more CoLine loudspeakers to meet this requirement. The application of these loudspeakers is so simple and intuitive that costly and time-consuming computer modeling programs are not needed.

The CoLine loudspeaker is typically placed on a stage deck or behind a cinema screen to achieve the desired results. All that is necessary to consider is that every listeners ears are on a perpendicular plane somewhere between the top and the bottom of the CoLine Loudspeaker System.





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