Velodyne Digital Drive Series subwoofer in stereo

Dear Truthseeker: +++++ " . If you play a 30, 40, 50hz pure tone thru a low distortion sub (<10%THD), YOU WILL NOT BE ABLE TO TELL WHERE IT IS COMING FROM " +++++

I agree with you on those frecuencies.

Regards and enjoy the music.
Raul.

After reading much of this debate, it is good to see that Raul & Truthseeker agree. Both agree when using low distortion subs at low frequencies (less than 40hz or so) that one cannot determine the location where those very low notes emanate from.

At these low frequencies the wavelenghs are so large, relative to the distance between the ears, that the source cannot be localized. This is because wavelength is inversely proportional to frequency (thus reducing the frequency by 50%, as from 40 hz to 20 hz, the wavelength is doubled in size).

Using a large driver with very low distortion (such as the Velodyne DD-15 or DD-18, rated at < 0.5% distortion), with a relatively low crossover point, so that the sub puts out very little information above 80 hz (relative to the mains), which is located in a time-coherent location (with correct phase, of course), when placed in a room (as opposed to placement outdoors suspended above the ground) the spatial cues for locating deep low frequencey notes are lacking, so the speaker's location cannot be detected.

If the crossover point is set so high as to allow upper bass (and higher) frequencies to be audible, then spatial cues become increasingly present and identifiable. Smaller drivers and higher crossover frequencies result in the intrusion of subwoofers into regions where they should not intrude.

However, if the equipment and room requires a setup where subwoofers operate at upper bass and higher, then they will be locatable by ear. Under these circumstances, although the location of the low bass notes cannot be localized, their higher level harmonics (and other spuriae) will be audible, thus allowing a degree of localization to be perceived. This is not ideal.

Ideally, the mains will create the soundstage - not the subwoofers. One or more very high quality subs with low crossover points, which are ideally matched to both the main speakers and the room, are the best way to go. I hope we can all agree on this last sentence.

By the way, I am not sure how much phase and time coherence affect this, but it seems logical to always strive for the correct phase and the most time coherent location feasible in a given room with any given system.

I really enjoyed reading the debate. Every opinion is welcome. Personal attacks are not.

What I would like to know is, assuming cost is no object, how many subs are best and how should they be placed in relation to each other?

Truthseeker and Cryptical -- Excellent information -- thanks!

My Rel Storm 3 has its crossover set at about 28 hertz, and it sits in a corner. I am generally not finding that the deep bass localized to that corner. Instead, it seems to emanate from between the mains, possibly sometimes just off the midline towards the sub-bass unit, but usually not.

On the other hand, I had a passive subwoofer in the back of my van, and it was clearly localizable to.....the back of the van. I don't know what frequency the crossover was set at on the amp feeding the subwoofer in the van, however.

It's just a stone cold fact that 65hz bass (which is where I cross over my Velodyne with full range speakers) is not locatable because of the extreme -about 15 feet- wavelength. There is simply not enough phase difference from one side of your head to the other for your brain to differentiate. Anyone who thinks they can is hopelessly delusional. So there are ONLY 6 possibilities:

1. The guys who hear bass in stereo have sub/small satellite systems with their variable crossover frequencies set way too high.

2. The guys who hear bass in stereo are actually hearing the effect of room nodes from the unpredictable interaction of the two subs nearly identical output, and interpreting that as "better" bass.

3. The guys who THINK they can hear bass in stereo on CD's have suboptimal systems with audible distortion coming from their subs which allows them to "locate" the subs output.

4. The guys who are SURE they can hear bass in stereo on CD's have vivid imaginations, are gullible, and therefore probably own Wilson Watt/Puppies, too.

5. The guys who are SURE they can hear bass in stereo on LP's are hopeless romantics, because - I got bad news for you - it ain't there. Even Direct Disk recordings have to be mixed down properly through the board so you can play the damn thing back. Here's a quote from a basic LP mastering text,

"Why is it so important for mixes to be mostly in phase and the bass being in mono?

If the mix is in phase (mono), the cutter stylus will move from left to right - if the mix is out of phase (stereo) it causes the stylus to move up and down. Too much up and down movement (out-of-phase) will produce a groove that's too shallow or interrupted. This will cause the playback needle to jump, especially the bottom end is very critical. If the bass is in stereo, the cutter stylus will leave the surface of the record – the plate will be unusable."

6. And last - They guys who ACTUALLY CAN hear stereo bass have HUGE HEADS - so their ears are far enough apart that the long wavelengths present enough phase shift. Of course, these guys can't use traditional headphones, and the large head has very negative WAF.