Two Each His or Her Own.

Quote:
Originally posted by Gonk:
Two sub outputs only provides a sound quality benefit over one output if the subs can be operated in a stereo mode...
Quote:
Originally posted by bestbang4thebuck:
Currently, I also run ‘stereo’ subs, two of the same make/model, facilitated by an Outlaw ICBM between pre/pro and power amp... if you have the ability to try things three ways – single mono sub, dual mono subs, and stereo subs – I’d say give it a try and see what you think. Some folks advocate an additional sub to separate LFE duties from the low frequencies of the full-range channels, but I’ve never tried two subs set up that way, nor have I tried stereo subs with a third sub for LFE only.
Stereo Subs (before): For the past two years, my system consisted two 15" Def Tech subs, which were paired (with speaker level inputs) with the Right and Left front speakers (Outlaw 990 set to Large), resulting in a full range stereo mode configuration. The “LFE Only” signal was sent to third Velodyne sub. I was very pleased with the balance and tonal quality for HT, and especially for high quality stereo and 5.1 channel recordings. While I have been using stereo parametric equalizers for the main L/R channels, I have been unable to attain the same control of frequencies under 60 Hz compared to the new Velodyne Subwoofer Management System (SMS).

Dual Mono Subs (after): Three weeks ago I made the plunge for 2 LFM-1 EX’s and the SMS-1 Parametric Equalizer. The SMS-1 does not lend itself to a stereo sub set-up, and the crossover in the 990 only provides a summed mono signal sub output. To achieve true stereo subwoofer output would require a separate stereo crossover between the 990 Pre-Processor line-level outputs (at large, full range signal) and two SMS-1’s. (Yes, you can use speaker level connections if you dare) In any event, it would be very complicated. At this time, I cannot justify the effort and expense of achieving a true stereo sub configuration, and believe that the benefits of the SMS-1 to be significantly more important.

Analysis: The SMS-1 is both a powerful analysis tool, and room/speaker correction device. Using the crossover network of the 990 (mains set to Small with 60Hz XO), the SMS-1 is easy to configure and set up. It was possible to compare the performance of one versus two subs easily, with the test microphone placed at various positions in the room. I found that two subs were significantly better for three reasons; 1) Much larger sweet spot, 2) More consistent sound level throughout the frequency range of the subs and 3) deeper base extension. One LFM-1 EX had a -2dB point of 17 Hz (one port plugged), whereas two subs were solid down to 15 Hz, which was the limit of the test trace. The controls and frequency response measurements are displayed through one of the 990’s audio/video source inputs.

Other Observations: My LFE channel is now also routed through both subs, so I no longer have a separate third sub dedicated to the LFE channel. I have not found any compression or other adverse affects in combining the LFE signal with the crossover signals from multi-channel recordings. As mentioned by others, I believe it is a good idea to place the subs close to the main L/R speakers or at least at a similar distance to the main listening position to preserve phase alignment of these long sound waves (a 40Hz wave is approx 25 feet long).

Testimonial...
In A/B testing, comparing the Def Tech subs vs. the Outlaw LFM-1 EX’s, there was an astonishing improvement, even before dialing in the EQ. The tonal balance, smoothness, and power of these Outlaw beasts (coupled with the SMS-1), allow for music to be played at preposterous dB levels without sounding “loud”. Distortion is the enemy of volume, and Outlaws.
Thanks Outlaws.