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Originally Posted by Autophile In-between two subwoofers playing stereo and mono, mono will be louder as the signal is summed, amplified and the two subwoofers are powered by identical signal, they are perfectly in phase in their entire bandwidth of bass reproduction. |
If the subs are not in phase in stereo, and this owing to the nature of the recording rather than due to the relative placement of the subs, then it is to be expressly understood that the recording was intended that way in the first place. It is not our responsibility to correct that. But, why some recording engineer would like to have it that way is completely beyond me, and I'm sure that is not a very desirable effect. Causes could range from poor miking to bad recording studio/ location acoustics. The solution is to buy better produced music. A stereo subwoofer setup would gayly (ok it's spelt gaily
Crap, i just have one more smiley left) bring this acoustic anomaly to your car.
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Ideally one should have stereo bass in the car (only SQ users) it complements the front stage and imaging very well. Lot of users has single subwoofers running mono and the box is ideally in one corner. Now listen to the familiar track with good musical bass sitting in the driver seat and then in the passenger seat the bass will not sound the same there will definitely be a difference, even if you call it as omnidirectional, difficult to localise. But it will not sound right.
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In almost all cases, the phenomenon you describe is attributed to standing waves. Irrespective of whether stereo mono, or singular subwoofer, standing waves will occur unless the listening environment in concern is an anechoic chamber, the best of which will greatly minimize the effects on standing waves but yet not completely eliminate standing waves in sub-bass frequency.
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If you have stereo subwoofers this will not happen. It will be the same. |
Nahin yaar, stereo, mono, or just one sub in the car, this will always happen. This will only not happen between two geometrically identical seating positions in the car such as if the sub is equidistant from the two listening positions in consideration
and the triangle (triangle in case of one sub, it could be a rectangle or axially symmetrical trapezoid in case of 2 or more subs) comprising the two listening positions and the sub are symmetrically located along the axis of the car. Even then, it only means that the bass information perceived at these two locations are just identical,
not perfect or devoid of standing waves.
Moreover, stereo separation by physically separating the 2 subwoofer drivers is not so easy in the car due to space limitations. Hence, the relative difference in distance between the subs is not so great when measured from the front listening positions to remarkably and accurate pin-point one of the two subwoofers. Additionaly, your recommendation of enclosure is of 28" length. Even if the subs are at the edge of the box, the center to center distance of the subs will be 16" for a subwoofer of 12" diameter. How separate is that compared to the listeners about 8 feet away? This is not my major argument though.
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This is the reason why the subwoofers are not used in the stereo setups in home audio. The integration between the speakers and subwoofer in home audio is very difficult. I have tried a lot of times from budget components to ultra high end, bottom line is it just does not work.
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Large floorstanding speakers use large diamater bass drivers that play subwoofer frequencies in stereo, some with sparkling gusto. This is analogical to trying to mate two stereo subs with a pair of speakers in every conceivable way. For well-designed speakers, this always works. But of course, with the kind permission of the room. Therein comes placement. Results are bad when speakers are not placed properly and worse when subwoofers are detached from the mid-high sections. The worst scenario is having a sub near or behind your couch. The car environment takes the proverbial cake. Hence a case against stereo subs.
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On the other hand we can achieve that in car audio by using electronics for adjusting delay, crossover, level, eq in each driver (talking about active system). Even in passive system you can take care of delay, phase and eq to a certain extent but not as extensive as active system.
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But why do you want to correct things that were intended to play wrong in the first place? This is the basis of your case for stereo subs in the first place.
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Try using 20Hz subsonic filter on the sub it will sound different with the filter on and off. The difference is noticable because you can hear the effect of filter at 20Hz
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You would hear a difference if information on the track playing did exist at or below 20Hz. Even if it does, the primary reason for hearing the bass differently is because using the subsonic filter rids the amplifier of the burden of unnecessarily amplifying signals of such low frequencies, and quite a burden at that. I am not denying that humans cannot distinguish 20Hz frequencies, but the cause of the changed sound. Inarguably though, 20Hz is as omnidirectional as it gets for ears that are half a foot apart.
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Today companies are spending money in R&D of high frequency drivers capable of reproducing frequencies above 20Khz. Even there are dedicated super tweeters which are used to reproduce HF from 10-15Khz to 54Khz. Now if we go theoretically humans cannot listen above 20Khz but brain does recognises frequencies above that, one might not notice but it definitely adds to listening pleasure. If our listening band width is 20-20Khz why the hell do we need expensive supertweeters, preamps / amps with frequency response of 5Hz - 100Khz.
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This debate could spark a whole new thread.
Time for my second smiley..