I just finished reading Roy Gregory's review of teaming up a Focal subwoofer with the EJ Jordan Greenwich speakers. In it he lays out a four-point rule for proper subwoofer integration:
Do not run the sub with a high-level input derived from your power amp's outputs – run the sub at line-level.
Do not use the sub's crossover to roll-off the bottom end of the main speakers – instead roll the sub in underneath them.
Do not skimp on the cables – you need to use the same interconnects and power cord that you are using through the rest of the system.
Do not rely on DSP to dial in the sub's response – optimise placement, crossover point, output level and phase setting first, with DSP as a last resort that's best avoided.
I know that you have a lot of experience with subwoofers so want to ask what your take is on this subject. Thank you very much. Roland
I agree with all of Roy's points but would add that ideally, you handle the hi/lo-pass division of labour in an external analog crossover. Relieving the main speakers of even seeing bass signal reduces their excursion needs (that's a win on lower distortion) and also keeps their voice coils cooler (that's a win for dynamic linearity). High-passing the mains properly is a big benefit but as Roy says, I'd not want to use a sub's own internal crossover for that. As to DSP, a parametric EQ embedded in player software like Roon or Audirvana can be ace to notch out our three primary room modes. Finally, time alignment matters and many subs suffer digital latency from their DSP crossovers. That should be offset with physical placement so the bass doesn't delay in time. Finally, dipole/cardioid bass dispersion holds key advantages over omnipolar box bass because it suffers less room involvement; and subwoofers want to properly decouple from the floor to eliminate structural resonances. So in my book, Roy's short list of rules would be just a bit longer but I otherwise see no fault in his. Srajan
What do you mean by offsetting digital latency with physical placement, please? Roland
For example, my Dynaudio sub incurs a low 2.5ms of digital latency from its internal DSP processing. Sound travels 34.4cm per millisecond. Multiply that figure by the sub's delay et voilà, the distance of how much closer it should sit to your chair than the speakers to lock in equal time arrival. In my case that's 86cm. Easy. Srajan
So your sub sits 86cm closer to your listening chair, correct? Roland
Exactly. The last place it should go is into the front corner because that would add another 2 metres worth of time delay. Srajan
But isn't the front corner where most manufacturers propose we place their sub? Now I'm confused. Roland
Corner placement leverages the meeting of three room boundaries for acoustic gain so anything placed there will play louder than if it sat in free space. Manufacturers who propose such placement don't believe that time alignment matters. I do so selected a force-cancelling sealed not ported sub and then one with a low-enough latency figure which I could easily compensate with placement. My downstairs sub is passive and its outboard crossover analog for zero latency. Now the sub can sit between the speakers equidistant from my chair. But audio is full of conflicting claims and beliefs. You asked me so I'm giving you my opinion based on my personal experience and preferences. Ask somebody else and you could get a different opinion. In the end you have to experiment for yourself then trust your own ears. Srajan
Okay, got it, thank you. Roland
