Axiom Home Page Forums General Discussion Advice from Axiom Owners Dual Subwoofers - Why - How?

Now I have seen posts with folks that have two ep500's or even (god help me) two ep600's.

Question is WHY? and HOW?

My receivers have a sub out...which I take to the subwoofer. Simple, easy.

How do you connect two of them? And does it really help the bass?

You can buy a Y splitter to connect the 2 subs to the sub out on your reciever, I use one for my sub and my amp for my bass shaker.
I'll let others that are more knowledgeable explain the benefits of 2 subs.

Basically, it makes it so you can have CLEAN bass and a flat bass response throughout the whole room.

I know you may have heard about how hard it can be to find a good spot in a room for a sub. This is because bass frequencies are very long and create what is known as "peaks" and "valleys" in the frequency graph. These peaks and valleys can change significantly depending on where someone is sitting in a room.

For example, if you sit in the front of the HT, There may be a bass "hole" at 50Hz, which means that in the position you are sitting in the room, you are sitting in a valley of a sound wave (from the reflections off all the walls). You will hear very little bass at the 50Hz frequency. In another seat (let's say the back row) you might have a bass spike at 50Hz, which means that the bass sound at 50Hz is much louder than it should be.

Depending on the combination of bass holes and spikes in certain sitting positions, the bass can sound empty (like something is missing) or bloated (like there is too much bass).

Now, when you set up a sub you try to keep all these hills and valleys to a minimum, but in some rooms it really isn't possible to get a flat bass response for all the seating positions.

When you have two subs, you can have a flatter bass response because you have two positions to work with rather than just one. This allows for the whole room to get a nice, even bass response. There are many strategies out there in placing two subs. You can place one sub in the front of the room, one in the back. You can have the subs in diagonal corners of the room, you can have them against the same wall, etc. Basically, it allows you to have clean, consistent bass throughout the room.

Two subs doesn't really mean louder, it just means cleaner sound.

While I am no expert in the field, I've tried to lay out what I know.

Many of the members on here know a lot more about me on this subject, but I think I got the gist of it.

There are TONS of articles on placing subs and stuff...it really can get complicated.

I hope that helped!

Dual subs give you more options for getting smooth bass response in your room, and for getting more even bass response at different listening positions.

They also let you get more clean bass output before the sub starts complaining. For a comparison, let's listen to WOTW in the scene where the tripods come up through the pavement :

My system (single SVS 20-39 PC Plus) - floor shakes, sounds scary, LF noises build, sounds really good, GRUNK BANG GRUNK (turn down the volume)... maybe we'll skip to the next track ;(

Jakeman's system (2 EP600, 1 EP500, 1 SVS 20-39 Ultra) - floor shakes, sounds scary, LF noises build, sounds really good, LF noises build, dogs leave the room, LF noises, build, wow this is neat, LF noises start to fade, cool can we listen to that again ?

Jakeman doesn't seem to have his subs turned up "hot", everything sounds very well balanced -- it's just that the subs can ALWAYS keep up with the other speakers no matter what, even on the toughest tracks. Being a subwoofer is hard work.

Tarun, as far as the strength of the response, when two widely separated subs(or any speaker for that matter)play the same sound, the result is an increase of 3dB in combined sound level. As an alternative to getting the 3dB increase each sub could be set slightly lower, presumably resulting in lower distortion, while keeping the overall sound at the same level.

Another advantage of multiple subs beside an increase in level/reduction in distortion is more even room response due to at least partially canceling some of the primary room modes. The paper prepared by Dr. Toole's colleagues at Harman discusses this and is worth studying. The basic idea is to place two subs opposite each other either at the middle of the front and back walls or the middle of the side walls. In the mid-wall position some modes are at a minimum, and the subs being opposite each other results in partially canceling some other modes.

Nice link JohnK, was very interesting.

For those who are thinking "Boy, this really IS complicated...I wonder what the best configuration is..."

Just skip to the last page. That's all you really need to know.

That's cheating, Dan! Those who thirst for knowledge should be willing to suffer a little bit in pursuit of it!