Affordable Subs

Dual always works better and is simpler to set up. Let me explain some basics again. When we add a sub or subs we are using both the crossover and acoustical summing to combine the sub and the satellites. In theory as long as we keep the sub and each of the satellites within a distance of less than 1 wave length of the crossover freq they should sum. Unfortunately the real world is a cruel place and things are not really as simple as they seam. Most crossovers do not completely cut off at the stated crossover Frequency, instead they have a slope either -6dB, -12dB, -18dB, -24dB or even -48dB (via DSP) per octave and a corner frequency. What does this mean? OK let’s define it this way, 24dB at 120hz the filter is going to cut the highs out of sub and the lows out of satellites at a rate of 24dB per Octave, 120hz is not the frequency where the filter starts cutting its the point where both filters have cut 3dB. A 12 dB filter is cutting out half as much per Octave. From a simple one dimensional stand point, looking just at Frequency response steeper crossover slope (24dB) is best, but we also have to look at phase. Filters Also effect phase response and for the most part the steeper the filter the more phase shift. So from just a phase stand point -6dB per Octave great, -24dB not that great.

Now with a single sub we have 3 speakers (trying to) working together
Left with a response like this \, right also with a response like this \, the sub with a response like this /. Often you get things right with a single sub you notice an awesome lowend, more woomp it’s defined, it goes lower but there is a mid bass suck out and or smear.
This is where Stereo, not dual but stereo subs makes all the difference
With stereo subs we are summing 2 distinct stereo pairs that will also acoustically as one, think of it as first summing 2 groups of left sat \ / left sub, right sat \ / right sub. With stereo subs we get to move each sub closer to the satellite of the same channel the magic here is that idea of we will get acoustic summation if the 2 speakers are within 1 wave length, here we go back to the crossover of -24dB at 120hz. Let’s say our monitor level is at 74dB now let’s look at 60hz, it’s not all sub our satellites are still putting out approx 50dB and the opposite is true at 240hz, the sub is putting out 50dB. We want that 50dB the sub is putting out to sum with as little phase difference as possible to the sub the distance for acoustical summation at 240 will be half that of 120. And at 480 1/4 of that. At 480 our -24dB at 120hz at 74 dB sub will be putting out 26 dB and at 960 2dB, if we can get that sub driver cone within a foot of the satellite diaphragm operating at 960hz we should have acoustical summation! Stereo subs just make it easier to get good acoustical summation by putting each sub nearer its satellite.

Are to cheaper subs better than a single expensive sub? Well this the billion dollar question, in most cases with my 3 way Questeds when I can place a sub directly under the cabinets I have found the answer to be 2 cheaper subs are 100 times easier to dial in than a single sub 4 times the price if the cheap subs go deeper than the Questeds will go. Same if I set up the F11s or the Magnepans. The big TADs are the exception simply because it’s really hard to get the sub drivers close enough ( big heavy cabinets that I can’t just put on a stand and put a sub under or next to the woofer.
With the SVS I was up and running and wowing people in 10 min, with the DSP and App in an hour it was like the Questeds had simply grown an Octave range, if I had put up a scrim and visually hidden the SVS’s below them you would never have known the subs were there ( I know because I’m mean and did it to the kid and my wife who have both been trained by and have to live with me and didn’t know the SVS were even here wife and up and running kid). Wife has not forgiven the Dr who loaned me the SVS before we set them up at his place where they replaced a single JL fathom we couldn’t get to intergrate after 2 years.
It took 1/2 an hour to get the stereo SVS up and giant smile on his face, he says he has made a couple of small DSP changes in the month since.