REL Acoustics - Subwoofers - All about the Bass

“The subwoofer’s task to deliver musical fundamentals below the reach of ordinary loudspeakers. It’s an approach that can work well with compacts, but often works even better with large speakers…” Alvin Gold Gramophone

One secret to a REL sub-bass system’s success resides not only in its ability to extract the deepest sounds in the mix, or in its bullet-proof reliability and conspicuous overbuild, it resides in its ability to integrate effortlessly with the main system, enhancing its sound by naturally underpinning the output from the speakers – to make them sound as if they’d doubled in size. REL defined the conditions for successful integration years ago by following three simple but hitherto elusive principles:

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To ensure no blurring or other sonic degradation to the main system, the solution is to connect the sub-bass system from the power amp. REL sub-bass systems are designed to be connected to the existing power amp’s speaker terminals using the gas-tight high-level Neutrik connection supplied with virtually all RELs. In this way there is no interference or possible corruption of the main signal going to the speakers. By connecting at high level, the sub will reproduce exactly the same character of bass as the main speakers. 
The sub-bass system draws virtually zero current from the power amp because it is a very high impedance load (technically we say it is voltage driven). No harm can come to the sub-bass system whatever the power of the main amp, even a kilowatt can be accommodated with ease.


There is also the substantial benefit of the bass engine in a REL system being driven by its own dedicated, high current REL power amplifier – optimised for that specific driver. It is DC coupled in all but our smallest design, meaning there are no capacitors in the signal path causing phase problems and limiting its ultimate low frequency performance. REL power amplifiers are designed to produce high levels of current and built in the most robust manner practical.


Because of this built-in high current REL amp, there is no power drain on your main system amplifier. It goes on happily driving your main speakers precisely as before, albeit with the significant benefit that because the REL is now fully energizing one’s room it is possible to enjoy the system at lower volume levels and with less sense of strain. Women, in particular, come to love this aspect of REL ownership. As counterintuitive as it may seem, restoring bass by adding a REL can result in lower average listening levels precisely because one doesn’t need to turn up the volume as high to provide the drive and pressure one is often seeking in higher volume levels.


REL know the secret to a perfectly balanced system is their filter circuits. Evolving over several generations the REL filter circuit is considered a trade secret, To this day, we embed them in a matrix designed to destroy the components hidden within should our competition try to discover the ideal way to crossover. Speed is incredibly important to a sub crossover and so we employ, simple, direct and very fast-acting filters. Based on second order designs, they are intended to allow all the speed and slam of Music to emerge—and importantly, all of the subtlety—while still performing the necessary crossover filtering.

The filters used in Gibraltar are, to our knowledge, the fastest ever built into a production sub bass system and measure at the theoretical limit of a filter circuit at approximately 4 milliseconds of group delay. Those used in our other models are still remarkably fast and weigh in at around 8-12 milliseconds. In order to properly reproduce music and film sound’s dynamics and natural qualities, we do not offer room correction modes. While these can, sometimes, have a positive gross effect they also slow down the transient speed of the system hugely.