So you want more bass? Simple, just add a subwoofer, job done.
If only. Sure, getting it right can make a big difference. But subwoofer setup is difficult, fine-tuning things so your sub doesn’t dominate the sound isn’t easy. As I found out when I reviewed Elac’s SUB3030 for Darko. I was still making changes – fiddling – weeks after I started.
It’s difficult because we the listener play the role of speaker-designer, blending the bass into the overall sound for a seamless whole. It’s just that we haven’t done it before and we don’t have the tools for the job. The published spec of the main speakers is probably the only thing to help us. Like I said, difficult. Think Muggles taking on Severus Snape at the Dark Arts. Even Harry Potter struggled with him.
Get the set up wrong and bass can be overblown, the subwoofer overlapping with the main speaker as both pump out music in the 30-120 Hz region. There’s also the temptation to hike the subwoofer volume up, to hear what you spent your money on, to impress friends. Which just makes it stand out more, ruining the overall balance.
One option is to get someone experienced to do it for you. Rob Hunt from REL cut the process down from weeks to just 20 minutes when he set up two REL subwoofers for me to review. Rob’s quite busy though. Maybe your dealer can help.
Or you can do it yourself. With time, a methodical approach, and maybe a small dose of luck it can be done. Up for it? There are four things you need to focus on – where you put the subwoofer, its phase, the crossover point and the gain.
Location location location
Bass is supposedly non-directional, meaning you can’t hear where it’s coming from. Not everyone agrees with that. Better to play it safe and keep the subwoofer up front, close to your main speakers. Try not to hide it behind that sofa.
A front corner is ideal as it helps the subwoofer go lower, the bass reflecting back into the room off three surfaces (two walls, one floor). For the technically-minded that’s a theoretical 9dB increase (+3dB per surface), which makes a difference.
Room constraints / aesthetic considerations may nix corner placement. If so, experiment. Against a wall will probably be best (two surfaces). Alternatively try putting the subwoofer between the main speakers, or to one side but level with them. It helps with timing – the subwoofer bass reaches your ears at the same time as the rest of the sound. And finally if the driver in your subwoofer fires forward, not down, then turn it to face the listening position. It sounds a lot better than firing across the room (the positioning shown in the last photo below didn’t work).
More than any other factor, the best position for a subwoofer will vary from room to room, so be prepared to experiment a bit to optimise things.
This one’s a bit easier as generally you choose between 0 and 180 degrees for phase. The one that produces more bass is the right setting. Then it’s working with your main speakers, not against them.
The crossover point defines the frequency below which the subwoofer works. But where to set it?
Some subwoofers make it easier by splitting the frequencies between the sub and the main speakers. The full signal is routed through the subwoofer. The crossover point is set on the sub, with only the frequencies above it being sent to the main speakers. Frequencies below the crossover point are handled by the subwoofer. Easy (relatively speaking, you still have to decide what frequency to use).
With many subwoofers – RELs for example – the full signal is sent to both the main speakers and to the subwoofer. The crossover point is set so the subwoofer handles only the lowest frequencies, the ones the main speakers can’t get down to. The main speakers cover all the frequencies they normally would.
That sounds easy in principle but isn’t. Set the crossover point too high and there’ll be overlap between the sub and main speakers that will muddy the sound. Set it too low and there’ll be a gap, frequencies that neither the subwoofer or the main speakers are reproducing.
The best approach is to set the subwoofer to roughly the right crossover point* and then experiment. Listen for the crossover frequency at which the subwoofer is making a difference but not so much that it stands out. When you find it, the subwoofer and main speakers will sound seamless, as if your main speakers are just going lower. It will take a few iterations for sure.
* try the ‘-3dB at xx Hz’ figure that should be in the specification of your main speakers. If there’s only a -6dB number then add about 5Hz to the associated frequency.
All that’s hard enough. But you can’t set the crossover point in isolation, you also have to set the volume of the subwoofer relative to your main speakers. The gain. Remember that trick where you pat your head and rub your stomach at the same time? Try it after a couple of beers. That’s what setting crossover and gain simultaneously is like.
App control = simpler rear panel on this Elac sub
Experimentation is the only option, your ears the final arbiter. I find the best approach is to focus on the crossover point first. Get that somewhere near right, then bring the gain up incrementally. Stop when the subwoofer starts to intrude, then reduce the crossover point slightly.
At all times…is the sound a little bloated? If so, reduce the crossover point. Is the bass dominating proceedings? Turn the gain down slightly. Then listen again. And again, and again. The closer to the optimum settings the longer the listening sessions will be, the more subtle the changes you make. At some point it should all click, at which point relax and enjoy the impact the subwoofer is having. Try not to fiddle any more (easier said than done)
Oh and don’t be afraid to set the crossover point quite a bit higher than the low point of your main speakers. When I reviewed the Elac SUB3030 I had it crossed over at 40Hz. When Rob Hunt set the T/5x subwoofers up for me he had the crossover much higher, at around 60Hz. Yet I was using the same main speakers with both subwoofers. Crossing the REL over at 60Hz felt really wrong in theory, but worked well in practise.
And that’s all there is to it! OK, I’ve painted subwoofer setup as a bit of a thankless task. True it can be frustrating, you certainly need patience. A methodical approach also helps.
The good news is that it gets easier with experience, witness speedy gonzales Rob Hunt. And it is worth persevering. When it all slots into place the subwoofer won’t just add bass to your system but greater meaning to the music. The REL T7/x I’m currently using certainly does. Why not give it a go?