Tighter, Punchier Bass

February 7, 2018 by Ben Stowe, CTS

One of the biggest mistakes I see audio professionals of all walks making is that they have high-frequency boxes and subwoofers out of time-alignment. Their system is sabotaged against them and they don’t even realize it. To try compensate for the poor result they just continue to pump more power into their speakers and in many cases cause component failure.

The solution is incredibly simple and the results may astound you. The problem that we have here is simply that frequencies around the crossover point are arriving at different times which is causing power alleys, nulls and phase shifts at those frequencies. To correct this, we simply need to time-align those loudspeakers. In plain English, we need to slow down the sound coming from some of them to match the sound coming from the others. We can’t speed up sound, so slowing it down is the only option we have. This is easily done with a “delay” in a signal processor, and some powered loudspeakers now include one in their processing.

A simple scenario that we could use to visualize this is that perhaps we have a pair of high-frequency boxes on stands to the left and right of our DJ booth, and to achieve coupling with and avoid cancellation from the wall behind us, we’ve placed our subwoofer against that wall. Let’s say that the wall is 8 feet behind us. We now have approximately 7mS of delay between our tops and our subs. Most modern signal processors will allow you to enter the distance in feet or meters, or we could enter 7mS for our delay and see if it sounds better, then adjust to suit.

There are more scientific ways to do it using a software package like SMAART and measuring impulse response, but one of my favorite ways to do it is simple and solid. I generate a tone around the crossover point of my system, then invert the sub so it is 180º out of phase with my tops, and then watch an analyzer as I adjust delay time. I watch for the bar representation that frequency on that RTA to dip down to it’s lowest point as I adjust delay time. That tells me that I have maximum cancellation between tops and subs. Consequently, when I turn off the phase invert and flip the subs back in phase with the tops I should have maximum summation and a tightly aligned system.

Ben Stowe, CTS Ben Stowe, CTS (26 Posts)

Ben’s love of electronics and technology led to years of schooling in Electricity, Electronics, Robotics and Lasers. Ben supported himself through school by building and selling strobe lights and other electronic devices. He built his first DJ show largely from scratch and scrap, often repairing broken items others had thrown away because he could not afford to buy new equipment. He holds a Minnesota electrical license, and his AV installs have been featured in almost every major industry trade magazine. His relentless passion for education has led to a number of other certifications and accreditations, including the most widely recognized one in the AV industry, the InfoComm CTS. His love for education inspired him to begin the ProAcademy educational sessions, focused on increasing understanding of AV technologies within the industry. Ben has been involved in a number of technical writings, lectures, presentations, as well as research and development assistance with a number of manufacturers for products, industry wide. He is also a regular contributing author to industry magazines in the United States and Europe. Ben’s presentations have been featured across the world both as a part of industry leading trade shows, and as a presenter for various groups and functions. Some of these events include BPM in the United Kingdom, Mobile Beat, the ADJA National Convention, Wedding MBA, and a national tour as a headlining presenter for an industry magazine. The United States Armed Forces branches have also called upon Ben to provide engineering and training assistance. His highly informational, slightly nerdy and always funny presentation style have made him a favorite at events, while his sincere desire to help people with their application of technology have made him a favorite with them after the event. Ben serves the industry as the President of NLFX Professional, an industry leading supplier of sound, lighting and video systems, a role he has maintained since founding the company in 1993.

Filed Under: Mobile DJ Equipment, Sound, Sound Engineering for Mobile DJs