Placement of Single Subwoofer Affecting Sound of Main Speakers

How is the sub connected?

It’s connected to the amp’s preout with a pair of RCA interconnects. That’s the only method of connection that is available.

Maybe I should.. We'll see how it goes as I've just invested in some springs to enhance the sub's performance, still in transit.

The effect you may be having is that the sub is acting like a tuned bass trap, OR you are finding it’s reflecting a lot from the speakers.

Yes, either one must be true. Somehow any furniture in the room will affect the sound, especially things placed very close to the speakers. I tried placing a 2nd set of speakers just beside the main speakers in an attempt to run 2 pairs of speakers in the system. I hoped it would work but the sound was ruined. In the end only a pair of speaker can remain in the room.

Thanks for all responses. I find the below from Mapman particularly useful.

Ideally you want one sub front and center. Front and slightly off center is next best. Avoid the corners. Rear center is another decent option especially if you sit closer to the sub than the front mains. You can get away with a lot with sub placement though when needed especially if sub is set to not do much above 60-80 hz or so.

The corner placement with a single sub mirrors my experience. The current placement at the rear of speaker slightly away from the corner yields much better result. However, the effect or impact of a working sub is minimal since I have to set the crossover quite low at around 50 Hz. I tried setting it up to 60-80Hz and the sub is doing more harm than good with the bass sticking out like a sore thumb. Turning down the volume helps but there’s very little to no difference with the sub switched on or off.

I will likely try the 3rd option by pushing the sub further out to the centre of the room / speakers but it cannot be directly at the centre. When I tried this placement about a week ago, I recall the sound to be good but again the impact of the sub was minimal. Pushing the crossover and volume up too much and the bass sticks out too much. I will attempt this placement again once I receive the Nobsound springs.

I understand 2 subs(or more) are better but it is out of question. It is either 1 or nothing at all.

Should ask what sub are you using and what speakers? Also consider using white noise and a sound meter ( app on smartphone) to get an idea of what is going on in regards to sub filling in lowest octave at your listening location smoothly.

The sub is a PMC TLE1 (dual 6.5" woofer, transmission line) and the speakers are Marten Duke 2. Will try the more advanced set up method you brought up sometime. At the meantime, using the ears will do it for me. I have a Radioshack SPL meter though.

I’ve also replaced these lowly interconnects

with some decent ones as below. Van Damme cables.

I’m not sure if it has made a difference but the new one is certainly more sturdy than the thin flimsy wires I was using before this.

The Nobsound isolation feet will be the icing on the cake.

An update. To cut a long story short, the sub is staying. I’ll keep this short and avoid being long-winded. Most experienced folks would have known about this. After moving the sub around, I figured out that the placement of the sub is everything. The difference it makes is just massive.

As expected, the current best placement of the sub is between the speakers. It’s not at the centre but closer to the left speaker. I also found that the front of the sub needs to be on the same plane as the main speakers after moving it front and back. The sub now has about 2 feet from the rear wall (previously 5 inches).

With the new placement of the sub, the volume and crossover settings are completely changed. After trying several settings with different music, I’ve settled with these. The crossover frequency can now be turned up higher without the bass sounding forced or unnatural. Please feel free to comment if the settings need some adjustment. The volume and crossover settings are most important, phase setting is least important as I’ve always left it at 0, presuming the sub is in phase.

The volume is at 75%, rather high.

Crossover frequency is currently at 62 Hz.

Phase at 0.

It’s still a stock power cord. Will look for some better cords soon.

I’m amazed at the transformation of the system. It is quite rewarding once the integration of the sub to the speakers is close to seamless.

Added some isolation to the sub. Bass now sounds tighter and more seamless. Crossover frequency is bumped up from 62 to 68Hz without any ill effect, an increase of 6 Hz. Volume on the sub is now lower to compensate for the higher crossover frequency.

In summary, it’s an improved performance with these isolation feet which is a worthwhile addition. Previously on spikes or the sub sitting directly on the floor without spikes.

The image below shows the previous set up where the sub was sitting on the floor without any spikes.