How do wireless subwoofers do this?

Sorry if this is a bit off topic but those of you running two subs, I assume you use the right and left channels from the second preamp output to drive the two subs. That being the case, if the preamp output impedance is 600 ohms (@ 1KHz) and the to outputs are in parallel, would the preamp still "see" 600 ohms from the main output as well as each output, left and right,  from the secondary output?  Just trying to understand how would a single (tube) preamp handle these three separate amplifiers without any negative impact on the bass performance due to possible impedance mismatch.  

Both my subs are wireless but I have never bothered to try them wired so cannot compare.

However I went wireless for a different reason to most I am sure.
With my old wired sub I was getting some ground loop hum I could not eliminate.
The first wireless sub cured that and even though I have changed main equipment since which may have also fixed the ground loop hum I have never bothered to try wired again.

Besides as noted it does make placement and cable runs much less of a problem!

A download of the Syzygy application will give you a clear description of their DSP design. The 120 or 80Hz crossover settings your referring to sound like a surround receivers LF/Sub bass management settings.

If your electronics offer a separate pair of left and right RCA/line outputs they're what you'd use to connect to a wireless transmitter or directly to the subwoofer. 

Many powered subwoofers provide crossover adjustment as do a few preamplifiers. Since DSP can vary greatly crossover adjustment can range from a simple variable dial to a wide range of multi frequency bands of analog filters or digital parameters. 

This level of detailed crossover adjustment has been included on a few powered subwoofers and in the aftermarket for over a decade. To the best of my knowledge reviewers have only commented on the ease and improvement of a products auto equalization but little or nothing on the potential of a products manual adjustments. Its not a widely used tool but the effort and results can be quite satisfying.

Thanks to erik_squires whose been commenting on his methods.  

I have 2 of my 5 subs connected wirelessly. They don't sound any different than they did when I was using cables.

On a related note, anyone has direct experience how these 'wireless" subwoofers sound as compared to the 'wired' models? I assume the importance of the impedance matching between the preamp output and the plate amplifier still applies. The concept can definitely address some general room placement issues associated with wiring and cabling.    

Subwoofer DSP room correction does not implement a crossover. A preamp with bass management will implement a crossover.

A crossover is a combination of 2 filters.  Low pass and high pass.

A subwoofer's input can certainly implement the low pass. The high pass function is the main speaker's natural roll off.

So, it is possible to implement this limited filtering in the subwoofer alone.

Doesn't this mean there is an overlap of what the subwoofers are covering and what your speakers are covering so both your speakers and sub are producing any music below 120 or 100?

Yes. That's the idea. The more overlap the better. The whole point of multiple subs (Swarm, distributed bass array, etc) is the more places the bass comes from the smoother, faster, and deeper the results.

 Doesn't this cause distortion?

Only in the sense that on paper it looks like the timing is all wrong. Which would indeed be a very serious problem, if we were talking about midrange and treble. Precise equidistant symmetry is absolutely critical in order to get good imaging from the stereo speakers.

Bass however is completely different. At 20 Hz for example a human being cannot even hear the sound AT ALL at less than one full wave. That's 1/20th of a second. Cannot hear it at all! We simply cannot localize low bass anywhere near like what we can with higher frequencies. Read up on it. Its two completely different animals.

The multiple drivers in a 2+ way speaker, or when using a subwoofer plus speakers, always has overlap in the frequencies covered. That's how things are designed, on purpose, in order to get the best sound.

However when using a subwoofer, it depends on whether or not you have bass management or not. If you do, then the preamp or crossover will split the signal at the crossover point (there is still overlap). If you do not, then you'll end up running full-range to both the speakers and the subwoofers, and will need to calibrate based on that fact.

Subwoofer DSP room correction does not implement a crossover. A preamp with bass management will implement a crossover.

Ideally, the sub handles the integration seamlessly.


Yes, you can do this without adding a filter on the satellites. I do it this way. I suggest if your main speakers are ported, seal them before calibrating.

Best,

E