Why You Need A Sub
REFERENCE AUDIO – WHITHAM, ESSEX
BOB’s Blog Series - No 78 – The Sub-Woofer – Why do you need one (or more) at home?
TO SUB OR NOT TO SUB
To Sub or not to Sub, that is the Woofer. For all his attributes and foresight, I doubt that old Will could have conceived the purpose, need or desire to have a Sub in the Globe Theatre, we are talking 1599 after all. It is however a valid and often confusing question for today’s audiophiles, do I need a Sub in my home system? Today subwoofers are prevalent throughout the audio industry including two channel home audio, professional audio, home and commercial cinema and in-car entertainment. Why is that and why is the Sub often the elephant in the room that everyone wonders about, but most don’t understand? Surely a well-designed pair of speakers should provide all the bass extension needed in the average sized room at home. That may be the case, but every room is different, and our individual needs are, well, individual and this makes designing speakers that fulfil the needs of everyone and every room virtually impossible to achieve. Then we must consider the very different circumstances where a Sub might be used, a home stereo system for instance has very different needs to a home cinema system where the former needs a Sub to enhance the sound and the latter needs a Sub to reinforce the sound, in general terms at least. The needs of professional and commercial audio are vastly different from the needs of the home stereo and AV cinema users and I’m not going there in this article, instead concentrating on the home user experience.
WHEN DID IT ALL BEGIN
The short answer is just 60 years ago in 1964, on the 29th September to be precise, when Raymond Dones received a US patent for a low frequency speaker enclosure. In those early days sub woofers were solely used in home audio systems, multichannel cinema systems didn’t really take off until the mid 80’s. Those early Subs tended to use large and often flappy bass driver units with a 12” driver considered small. This was because amplifiers weren’t very powerful or dynamic in those days and getting decent bass extension and volume out of smaller drivers and enclosures was not practical unless the Subs were literally room sized boxes. Today of course most Subs have their own internal high-power amplifiers, commonly Class D ones, capable of delivering hundreds of Watts to drive the Subs main driver allowing smaller and more domestically sized drivers and cabinets to be used. These powerful onboard amps are used to power smaller and faster drive units that have greater pistonic movement than was possible back in the day. It’s not uncommon for bass drivers in subs to have 4” of travel, 2” forward and 2” backward giving previously unheard levels of bass response. To achieve this many Subs use modern driver materials such as carbon fibre and stiff, heavy and well braced cabinets. Today a 15” driver is mostly never seen or indeed needed in a home stereo or even a home cinema system.
CAN YOU HEAR IT
Stereo- Whenever I read reviews of Subs used in stereo systems and read about how they have been set up by the reviewers they inevitably intimate that a Sub should be seen but not heard. By that I guess what they really mean is that a Sub shouldn’t be intrusive because otherwise what’s the point of installing a Sub if you can’t hear it. There is a great deal of sense in not wanting the Sub to compete with your main speakers because you tend to end up with annoying boomy bass, loss of overall detail, definition and fidelity. Setting up a Sub can be a time consuming and frustrating event that, just when you think you have mastered it, another track comes on and suddenly the Sub is way too dominant or way too quiet. My advice here is to keep trying but after first installation and setup wait a couple of weeks before tweaking it again to let it settle in and to let you get used to what it does in your system. Where a lot of users go wrong initially is in setting the crossover point far too high and the volume far too low and this more than anything creates those annoying circumstances where the Sub is competing with your main speakers and swamping the sound. Getting a Sub set up to be right 95% of the time is something to strive for, 100% is I find often a challenge too far in a stereo system. This is particularly the case when using a Sub with stand mount speakers where finding that happy point where Sub and speakers are working seamlessly together is often harder to achieve. Contrary to most popular thinking Subs work better with larger floor standing main speakers than the ever will do with small floor standers.
Home Cinema – Integrating a Sub into a home cinema system is another matter entirely. This is where you definitely want to hear your Sub and where the system just can’t perform at its best without one or more than one in circuit at all times. Watching movies is a very different experience than listening to a two-channel music based system and its where you need your Sub to be a physical part of the action. Be prepared to experiment and I believe it’s going to be easier to get closer to 100% perfection than it ever will be in a stereo music only system.
HOW MANY DO YOU NEED?
Although many audiophiles are also home cinema enthusiasts the vast majority are still just interested in stereo systems and both have their own specific needs when considering whether to incorporate a Sub, or Subs into the home. It’s probably fair to expand on that by saying not all two channel systems incorporate Subs but virtually all (probably all) home cinema systems include at least one Sub.
How many Subs you install in a system very much depends on room size, whether you must share the room with other uses and of course how much bass you want to hear and feel. It’s not uncommon these days for more than one Sub to find its way into a stereo system and I find that having two is generally a better solution than just one. Installing two Subs tends to increase volume by around 3dB over having just one Sub so adding a second one may result in you needing to turn the Sub volume down a little.
For home cinema use it’s quite possible to stack Subs two or three high and use two or more stacks, but be careful, it’s easy to overload your room, but hey, those action movies will certainly impress.
SUMMING UP
I’ve tried here to answer the question ‘do you need a Sub’ but in case you are still in doubt then my answer is yes, I think you do, whether you have a stereo or multi-channel setup. I certainly use one at home in my stereo system and would miss it if it was removed. If I had a home cinema setup then my answer would be absolutely yes and probably more than one is needed. Installing subs and getting the setup right is always going to be a challenge, more so I think in a two channel only rig. I generally find that two small ones are better than one large one, particularly in a stereo system. Where to place the Sub or Subs in your room can depend on many factors and again some experimentation is called for. Placing in a corner can be the best place as the room corners help to boost the bass response but I often feel this gives just too much boost so try them in different places and if you have two then placing them beside but just behind the main speakers can be rewarding. Once installed and setup to your liking you will find it hard to remove a Sub and you will wonder why you didn’t include one sooner.
What a Sub brings to your system, especially a traditional two channel system, is a level of clarity and dynamic freedom that escaped it before the Sub was introduced (provided you don’t overcook the level settings). This is especially the case if you connect a Sub via its high-level input to the speaker terminals of your amplifier so that it receives exactly the same signal, in exactly the same timeframe as your main speakers. This is important for timing and that oh so important stop and start on a sixpence dynamic presentation that makes a Sub such an important part of the system. It also seems to free up the bass and midrange of your main speakers allowing them to perform better. Quite how a Sub can do this when it has no say about the signal being delivered to your main speakers is beyond my understanding, it just seems to have that effect. Perhaps it’s the audio acoustic way in which our brains receive and process sounds, especially music. But trust me, it works.
October 2024
Bob – Team Reference Audio