Bass for stereo

leeSK

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Feb 19, 2006
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Okay, when I want to watch a dolby stereo or mono DVD, obviously there is no discreet LFE but I can still have the option to have the sub on for bass anyway. My question is, for all mono and stereo films, do you just switch the sub off or have it on for extra bass?

I'm beginning to switch it off since the sound design wasn't made with an LFE channel and would probably sound more closer to how it was originally made than with a sub on.

On the other hand, ppl listen to stereo CD music with the sub so what gives?

What do you think?
 

SethH

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Dec 17, 2003
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When listening to a stereo or mono source the sub is not for LFE, it is used to reproduce the range that your other speakers cannot. Now, if your front speakers dig down to about 30Hz or lower then you probably don't need your sub for those sources as they are unlikely to have too much information below 30Hz (a 5-string bass guitar's lowest note is a B which has a frequency of 30.87Hz).

If your speakers start to roll off around 60Hz or above then I would think you would definitely benefit from having your sub on.

The key, however, is to make sure you sub is calibrated with your speakers. If it is perfectly calibrated then you shouldn't really be able to tell when the sound transfers from your mains to your sub.
 

leeSK

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Feb 19, 2006
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Well, I calibrated my sub 4 decibels higher than the mains using a needle point SPL meter because that's what I read, looking around the internet. The mains themselves are perfectly calibrated to each other.

I'll be honest, I don't understand this Hz stuff much but from what you said, I gather you are saying in simple terms that it's okay to have the sub used for bass on stereo and mono DVD's even without it being a discreet channel if the speakers themselves don't have much kick behind them.

I played songs from cd's and a stereo dvd without the sub on and it all sounds rather flat, no bass at all that I could pick up on.
 

ChrisWiggles

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How is your system setup? In most systems the subwoofer output is LFE plus bass below the crossover point chosen in the reciever from all the other channels. So absolutely you should have the sub on, or you're losing all that bass. Indeed, in many mixes there can be a very significant amount of bass in the main channels that in many systems is being properly routed to the subwoofer. Remember that LFE is not synonomous with "subwoofer channel" they are not at all the same thing.
 

JeremyErwin

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Feb 11, 2001
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The 3 db adjustment is used to compensate for inherent inaccuracies in the meter, iirc.

In movie sound, if the average SPL is 85 Hz, the main channels have an upper limit of 105 db. The LFE channel, has an upper limit of 115 db. This extra headroom allows a sound designer to insert effects that are more felt than heard. Human hearing is less sensitive to the lowest of the low frequency notes, so if a designer wants his 8Hz rumbling to be heard/felt, a lot of power needs to be behind it.

But a subwoofer can also extend the range of satellite speakers down to 20 Hz or so. The crossover splits the sound into low and high frequency signals, and the sounds are played accordingly.

Of course, if you have a sub par crossover, and really good speakers, "Direct" modes might, at times, sound better than "Stereo with crossover".
 

ChrisWiggles

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Actually the meter falls off down quite low, so you would actually end up slightly lower than the other channels as measured by the meter to be flat. By setting some dbs hot, many people prefer this and as they often listen well below reference, it helps recover some of the "slam" and impact you would get when listening at reference, but without everything else being so overly loud.
 

LanceJ

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Just an FYI for people using the stereo analog outputs on their dvd player when a multichannel soundtrack is being played:

Unless things have changed recently, when the above is happening conventional dvd-video players take the left/center/right/surround channels and convert them to a stereo signal, but the LFE channel is NOT part of this new mix i.e. it is thrown out.

This is done to prevent the cheapie 3"-5" speakers in most TVs from getting distorted and/or burned out.

What I don't want to speculate on is how dvd-video and dvd-audio players with built in Dolby/DTS 5.1 surround decoders behave. For example, some oddball brands that sell dvd-audio players won't decode DTS tracks and send them out via their analog 5.1 output, like all the Pioneers and Panasonics I've read about.

So yea, try to use the disc's stereo track if it has one, since it will have specially chosen bass frequencies that will work better with most 2.0 audio systems or 2.1 systems with small subwoofers.
 

ChrisWiggles

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It also is often a compressed dynamic range for a downmix to stereo. This may not always be the case, with a PC you can preserve everything including LFE to analog output, but it's because you can have complete manual control. Most regular sources don't have this kind of user-defined capabilities.
 

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