Because it's All About the Bass: Upgrading my Gaming Chair's "Subwoofer".

Post #210
December 2, 2017

Gentle reader,

Once again, thank you SO much for taking the time to read my humble blog. When I started so  many years ago, I expected very few would ever even see it. But readership has passed 130,000 page views so far. I am truly humbled. Below the article are some of the posts that are most popular right now.

This post is a little off my usual genre. No collection here. No changes to the listening room. Just a small project that has been in the back of my mind for some time.

Notice in the title that subwoofer is in quotes? That's because the term is SO overused. A true subwoofer is designed to enhance or fill-in the bass notes that are lacking from stereo and/or surround sound front speakers. The prefix sub means below. As in subway being below the "way" or streets. Granted there is little bass in music below say 40 Hertz. But there are harmonics that go further and of course in movie soundtracks, there can be some very deep sounds.Yet, numerous .1 speakers are referred to as "subwoofers" when in fact they have small drivers in them completely incapable of producing true bass notes. 

Many years ago a coworker/buddy gave me some PC racing games. I'd had no interest in gaming at all then. Being 61 now, I do. Our generation did not have such things. We had board games, slot cars, model train sets, and other inside activities. But mostly, we used our imagination and played outside. Our kids however did grow up with video games, but they were primitive systems with terrible graphics. And of course boxy CRT TVs. The generations since are seemingly born with the innate ability to operate controllers and pick up the art of gaming rapidly. I watched my grandson's 7 year old cousin pick up a controller and within minutes was "driving" cars very well in Xbox 360's Horizon 2. Astounding.

So, anyway, one of these games was called Test Drive Le Mans. Since the 24 Hours of Le Mans race is my absolute favorite, I was excited. PC games are meant to be played with the computer's keyboard. Well, trying to "drive" a race car with a keyboard was nearly impossible for me. I soon found out about steering wheel and pedal sets for PC racing games and bought one. NOW, I was racing! But it was very unrealistic as one has to operate the car from above and behind it. I hate that!

My daughter a couple years later bought me a PlayStation 2 Slim and my son bought me Gran Turismo 3. Later I bought the 4th version and other racing simulations. Those can all be driven as if one is sitting in the car and looking out the windshield. Newer ones have actual in-cockpit views and the screen driver's arms mimic your movements on the steering wheel. They have force feedback which shakes the wheel realistically when hitting bumps and provides "steering feel" just as a real car. Plus the game designers include actual physics so the "car" reacts exactly like it's real counterpart does in the same situation. Makes for some realistic and challenging racing. I love it.

As time went by, my son bought an Xbox 360 and I tried that too. It was SO much better than the PS2 and had a steeper learning curve. Plus the cars sounded REAL, not like the PS2 games do. My wife, being the ever so supportive of my endeavors bought me a gaming chair which sits on a heavy swivel base, has folding arms and built-in 2.1 sound system with stereo speakers in the headrest and a subwoofer under the seat. The ".1" stands for the subwoofer in a sound system. Most movies are at minimum 5.1: Center channel for dialog, left and right front channels, left and right rear/surround channels and a subwoofer. These "surround" the viewers with all the sounds of the movie, like one encounters in a movie theater.

Below shows the new larger woofer fits just as well as the original smaller one did.

Here are photos of the chair. I modified it to fit my 6'3" frame. Since most of the target audience is teens and few are in the 1%* like I am, I added a steel subframe beneath and created a cushion for under my knees. The allows me to sit with the stereo speakers in the headrest next to my ears and my head on the headrest. *Less than 1% of the world's population is 6'3" or taller. I added cushions to the armrests since I sometimes spend hours racing.

Here it is from the top. That's Heidi on of our Dachshunds.

Below are a series of images showing the old 4" driver and new 5" driver. The box that contains the driver (speaker) is rectangular and made of MDF. Medium Density Fiberboard. They included a bass reflex port, the small round plastic tube that's screwed into the box as seen in the photo at the top of the article. More on that below.

Based upon the dust cap (small convex cover in the center of the cone) the voicecoils may be of a similar size. But I do not know this for a fact.

Note how wide the spider (yellow corrugated device at the bottom of the cone) is on the smaller original 4" driver is. Unusual. The spider keeps the cone and voicecoil centered so it moves smoothly with the sounds and music.

The 5" replacement woofer has a significantly larger magnet. It has the gasket on the front as speakers have had for decades even though the vast majority of drivers are installed from the front and not the back. The original driver has no flange (raised wall that holds the gasket) on the front and does have a gasket on the back.
A little explanation: Below a certain sound frequency, I don't know the number, WHEN the sound waves coming off the back of the cone (when the music drives it towards the magnet) AND the sound waves coming off the front of the cone (when the music drives it away from the magnet) MEET in the air, they CANCEL each other out and no sound is heard.
THIS is why woofers need a box to keep the front and rear sound waves separate. Sealed boxes are often used, but many speaker makers choose to make BASS REFLEX cabinets. That is what the small tube is for. Through a complex formula, designers choose the correct size box and length and width of the reflex port tube. The sound from the rear of the driver, once it exits the front of the port SHOULD reinforce the sound from the front. Did they do so in this case? I don't know.
The chart below came from a stereo magazine many years ago. Although 5" is not shown, 5.5" is. Extrapolating, we can assume the 5" cone is 85% larger than the 4" and thus can move that much more air. I tested it by hooking a portable CD player to the chairs amplifier. There is a LOT of air being moved by the cone and port tube!

Here is another view of the new woofer in place behind the grille. You can see into the port somewhat. It extends almost all the way to the back of the box. Is it in any way correct for this new 5" driver. Again, I have no idea since I have no specs on the new woofer.

Obviously, the opening in the box was too small for the new driver and I used an electric saber saw to enlarge it to 4 1/4" in diameter.  The original recessed area the 4" driver sat in needed to be filled to seal the back of the new woofer to the box. Foam rubber tape did the trick. To make clearance to reinstall the cover, I carved down where the squared "ears" of the new woofer could sit down into the wood then screwed it in place. I trimmed the plastic ridge on the back of the grille so it clears the ears and screwed it back into place as well.

I tested it by driving cars with large engines which thus have deeper engine notes. Sounds great. The new woofer was $5.00. Below is a photo of the chair's amplifier face. 

It's not that well made. I had to remove it and solder the power supply wires directly to the circuit board. It's Input port has failed and to my surprise, plugging into the Output port actually works! It is also a receiver, they included a battery powered transmitter that plugs into the TV and transmits on three frequencies to the receiver amp. Trouble is, it's on all the time and batteries die quickly. So, I have a cable with Left/Right RCA plugs on one end and 3.5mm/1/8" headphone plug on the other. In the case of this TV, it has no analog (RCA) audio output, so I have a Toslink optical-digital to analog converter between the TV and the game chair's amplifier. I may replace the whole original amplifier with a better amplifier board. The controls will of course not line up with the original knobs and switches, but that's nothing I can't overcome.

Once again, thanks for taking the time to read my blog,

Scott

December 2, 2017