Guest contributor and Senior Product Training Specialist Ben Hagens shares some interesting background as to why the standard 80 Hz crossover setting for subwoofers in home theater and stereo setups may not be so valid anymore.
Setting up a home theatre can be a daunting prospect – I distinctly remember my first day in my AV career where my manager asked me to set up a 5.1 surround system for demo with zero training or supervision. Suffice to say, it was not good. So, I did what we all take for granted now – turned to the internet for advice. I became inundated with advice and gospel – often conflicting – from all corners (and I appreciate the irony that I am going to be doing exactly this in this blog).
Technologies change, knowledge improves, and experience deepens over time, but there’s one piece of home theatre setup advice that has stayed consistent for years – set your crossovers to 80Hz. It’s the golden rule. Or is it?
In the simplest terms, a crossover in an AV Receiver essentially routes the lowest frequencies from the main speakers to the subwoofer. In the 1980s, THX determined 80Hz to be their standard with the rationale that 80Hz downwards becomes difficult to localize, making it seem like the bass is coming from all around the room.
Technologies change, knowledge improves, and experience deepens over time, but there’s one piece of home theatre setup advice that has stayed consistent for years – set your crossovers to 80Hz. It’s the golden rule. Or is it?
In the simplest terms, a crossover in an AV Receiver essentially routes the lowest frequencies from the main speakers to the subwoofer. In the 1980s, THX determined 80Hz to be their standard with the rationale that 80Hz downwards becomes difficult to localize, making it seem like the bass is coming from all around the room.
In a practical sense, it’s also useful to have a single standardized frequency. An 80Hz crossover is a relatively okay compromise between being high enough to take the strain off smaller satellite speakers which may struggle with reproducing bass, and being low enough that the subwoofers stay difficult to localize. Sometimes it may need to be higher, especially when using much smaller ‘lifestyle’ type loudspeaker systems.
But what if you have large speakers that are capable of playing below 80Hz with authority?
It’s amazing how much difference spending the time to really dial in the crossovers in a home theatre system makes. I’m a big believer in getting as much of the sound through the speaker position it’s meant to go through – and sometimes this does mean everything at 80Hz. However, bass below 80Hz being hard to localize is not the same thing as steering of sound. The experience simply becomes better if the fundamentals, overtones and harmonics of a sound are coming from the same (or close to the same) position, just as it does in reality.
But what if you have large speakers that are capable of playing below 80Hz with authority?
It’s amazing how much difference spending the time to really dial in the crossovers in a home theatre system makes. I’m a big believer in getting as much of the sound through the speaker position it’s meant to go through – and sometimes this does mean everything at 80Hz. However, bass below 80Hz being hard to localize is not the same thing as steering of sound. The experience simply becomes better if the fundamentals, overtones and harmonics of a sound are coming from the same (or close to the same) position, just as it does in reality.
The shoot-out in Kevin Costner’s ‘Open Range’ is a great example. When I play that scene with our KML theatre set to our usual settings (LCR/RR/RL at full range, SR/LR at 40Hz, overheads at 60Hz), the soundstage is expansive and immersive, each gun sounds unique to its type (as opposed to everything sounding like a hand cannon), and the steering of the gunshots through the room has you ducking your head. But the sense of openness is something else entirely: You really get a feel for how large the space is in the film – after all, it is set outside.
When I switch the system to 80Hz crossover all around, that all changes. Don’t get me wrong – it still sounds great, and if it was the only way I listened to it, I’d be more than happy. But compared to our truly dialed in crossover selections the scene loses so much of that excitement and realism. The crack and percussiveness of each gunshot becomes slightly disconnected from the subsequent echo into the distance. The whole soundstage starts to feel as if it’s being drawn toward the front of the room and the environment feels somewhat closed in (again, compared to our normal settings).
When I switch the system to 80Hz crossover all around, that all changes. Don’t get me wrong – it still sounds great, and if it was the only way I listened to it, I’d be more than happy. But compared to our truly dialed in crossover selections the scene loses so much of that excitement and realism. The crack and percussiveness of each gunshot becomes slightly disconnected from the subsequent echo into the distance. The whole soundstage starts to feel as if it’s being drawn toward the front of the room and the environment feels somewhat closed in (again, compared to our normal settings).
In ‘Never Enough’ from ‘The Greatest Showman’ – a common scene in demonstrations and shows across the world, the periodic bass drum is another great representation of how crossover settings can really make a home theatre system shine. So many times I’ve watched that scene and it feels like the bass drum kind of camps out in the front of the room. That bass drum is meant to wash through the room, like a real drum sound does. After all, it’s a soundwave, right? The higher the crossover is set, the more the subwoofers reproduce the harmonics and overtones, as opposed to being drawn through the room by the surrounds and then rears in such a way that it more closely represents how that sound would travel in real life.
Sometimes the answer is 80Hz – a lot of factors come into play here, but I can almost guarantee where you end up will depend on a combination of your system and the room. Spend some time this weekend tweaking those crossover settings – it could very well be one of the best upgrades you do.
P.S. If you’re setting a crossover in the AV receiver, make sure you set the subwoofer to its LFE mode (all KEF subs have this option except T2 which is always in LFE mode)!
Sometimes the answer is 80Hz – a lot of factors come into play here, but I can almost guarantee where you end up will depend on a combination of your system and the room. Spend some time this weekend tweaking those crossover settings – it could very well be one of the best upgrades you do.
P.S. If you’re setting a crossover in the AV receiver, make sure you set the subwoofer to its LFE mode (all KEF subs have this option except T2 which is always in LFE mode)!
By Ben Hagens for KEF
