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Post by boomzilla on Aug 4, 2020 5:41:08 GMT -5
It is audio dogma that any frequency less than 100 Hz. is non-directional, and thus no stereo separation is required. This truism is presumably golden whether the bass is coming from a room-diffused sub or from a pair of near-field computer speakers, yes? So on to my question: I will be specifically using an 18dB / octave low-pass filter for my subwoofers set (at least initially) to 70 Hz. That means that if I have an 80dB bass tone at the crossover frequency of 70 Hz., then by 140 Hz. the amplitude will be only 62dB. And by 280 Hz., the amplitude will be 44dB. These amplitudes ignore the natural roll off of the subwoofers, so actual amplitudes above the crossover frequency will actually roll off at a significantly steeper rate. I do have two subwoofers, and the "normal" lineup would to be to run them in stereo mode, one for each channel. But to do this wirelessly, not one but two Emotiva VSUB-1 "Virtual Copper" subwoofer transmitter / receiver pairs would be required. The wireless units are not inexpensive at $130 per pair. Not outrageous, but not inexpensive either... So my question is - Since the crossover frequency is below the directional limit, and since the slope of the low-pass filter is steep (18dB / octave), would there be any audible degradation in performance noted by using a common, monophonic low-pass signal from the crossover to simultaneously feed both subwoofers? This would eliminate the stereo information from the audio signal below 70 Hz., but would it matter? My thought is that I can always try the bass in mono, and if I'm not satisfied, I can easily add stereo to the system again for an additional $130. But my other thought is that even if I use a mono signal, I may have eliminated the signal wire from the crossover to the subwoofers, but I still need a jumper wire from the wireless receiver to BOTH subwoofers. So - not as big a wiring reduction solution as initially it seems... For the extra $130, maybe just buy two transmitter / receiver pairs? Open to suggestions. Thanks - Boomzilla  |
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Post by ttocs on Aug 4, 2020 9:37:46 GMT -5
I was recently happily educated on a fact which I had not known about previously, which is that most musical recordings sum the bass below 100Hz. I couldn't see this as being true, but it is. I could only confirm that some, few, recordings are produced with stereo bass.
That said, you can buy Receivers individually, so it's really a $60 decision to go from Mono to Stereo - two receivers and one transmitter or two tran/rec pairs. Knowing what I now know, I would get two pair.
When I ordered mine, I bought one transmitter and three receivers because the subwoofer outputs are mono so I thought, why bother? Well, now that I'm getting into all this calibration stuff and thinking that I'll probably get the Dirac Live Bass Control, this would mean that I need to keep the subs separate with each on its own channel. This is all to say that I hope Emotiva will sell the transmitters individually so I can get two more.
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Post by garbulky on Aug 4, 2020 9:48:41 GMT -5
I was recently happily educated on a fact which I had not known about previously, which is that most musical recordings sum the bass below 100Hz. I couldn't see this as being true, but it is. I could only confirm that some, few, recordings are produced with stereo bass. That said, you can buy Receivers individually, so it's really a $60 decision to go from Mono to Stereo - two receivers and one transmitter or two tran/rec pairs. Knowing what I now know, I would get two pair. When I ordered mine, I bought one transmitter and three receivers because the subwoofer outputs are mono so I thought, why bother? Well, now that I'm getting into all this calibration stuff and thinking that I'll probably get the Dirac Live Bass Control, this would mean that I need to keep the subs separate with each on its own channel. This is all to say that I hope Emotiva will sell the transmitters individually so I can get two more. My amateur recordings are produced with stereo bass and no dynamic compression  I know little about recordings other than how to setup stereo mics and press record, but I am always astounded how good the stereo field ends up being despite all my other newbie mistakes. |
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DYohn
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Posts: 18,340
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Post by DYohn on Aug 4, 2020 10:27:02 GMT -5
Almost all commercial recordings made in the last 50 years are mastered with mono sub-bass tracks.
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Post by jackfish on Aug 4, 2020 10:27:19 GMT -5
While bass tones below 100 Hz may be non-directional, the human brain works very hard to make sense out of what comes in through the senses. There are other aural cues that belie the non-directionality of certain low frequency program material. The slap of a standup bass string or kick drum associated with a low note can provide the locational giveaway of the subwoofer, or in many cases the note seems to come from the position of such aural cues. This has been observed in many studies.
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Post by AudioHTIT on Aug 4, 2020 11:24:22 GMT -5
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Post by boomzilla on Aug 5, 2020 4:38:31 GMT -5
The higher frequency clues (the slap of the bass string) provide the steering clues for the ears. The fundamental is non-directional. Of the list of dual subwoofer virtues:
Less excursion for each sub driver reducing intermodulation-distortion for the bass frequencies.
Tighter bass (from less excursion)
Less strain on the sub amps
Separation of bass sources when it exists in the recording
Diminution of room resonances (standing waves) due to the separation of bass sources
Less excitation of the subwoofer enclosures' vibration modes due to lower SPL from each
Better coupling to the room due to more cone area
The ONLY one that would apply to stereo bass (separation of bass sources) is moot because such audible "separation" is not in the subwoofer's frequency range, but rather at higher frequencies. Therefore, provided the crossover is done at a sufficiently low frequency, having the actual subwoofer signal in mono is fine. This is NOT to say that a single subwoofer is as good as two or more. It merely asserts that the subwoofer signal need not be true stereo for ideal bass effects.
In fact, the argument can be made that a monophonic subwoofer signal is actually SUPERIOR to stereo subwoofer signals (when using two or more subwoofers). Why? Because if a bass signal appears in one channel only, and the subwoofers are in stereo configuration, then one and only one subwoofer is reproducing that low-bass content. The entire goal of using two or more subs was to specifically AVOID having one subwoofer reproduce the low bass. Using both subs smooths room response.
Although a "single channel only" bass signal would be unusual for acoustic music recording sources, it would be far more common for synthesized music and for movie soundtracks. Therefore, I'd argue that even when stereo right and left subwoofer signals are available, better performance will be obtained by using a summed, monophonic subwoofer output and letting all the subs come to the party.
Boomzilla
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Post by audiobill on Aug 5, 2020 5:51:31 GMT -5
Please keep in mind that the in-room response of each subwoofer will likely differ, maybe by a lot, regardless of what's on the recording.
For this reason, if two subs are used, perhaps equalize them separately or at least equalize the average in-room response when measured.
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Post by ttocs on Aug 5, 2020 7:34:28 GMT -5
2 pair for stereo. Everybody's happy.
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Post by vcautokid on Aug 5, 2020 7:52:56 GMT -5
Dyohn is correct. 2 channel or 5.1 is the usual in most recording applications. We use the dual or more subs to help us in our less than perfect room with DSP help and software. I get by just fine with one Sub but that is my room plus space and eviction are not attractive to me. Many rooms however benefit from multiple Subwoofer layouts due to nodal and null responses in the room. This has been around forever. Emotiva should do a dual Subwoofer deal with transmitters as an option ot Dual Subwoofer packages. A few other vendors do and it sweetens the deal for solution option that can be explored that otherwise for some would be left on the table.
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I know little about recordings other than how to setup stereo mics and press record, but I am always astounded how good the stereo field ends up being despite all my other newbie mistakes. 
