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Old 23rd January 2013, 03:07 AM   #1
ZLyzen is offline ZLyzen  United States
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Default Question On 2.1 Audio

So I know this question goes a lot deeper than what I'm asking, but I'm sort of asking for the quick answer for the time being:

For 2.1 audio, a common approach I've seen is that the right and left channels are added together after the low-pass and then sent to the sub-amplifier. This would mean, since the low frequency spectrum of music is usually quite similar for both right and left channels, that the voltage of this signal is now double what it used to be. Is this compensated by giving the satellite speakers say a gain of 20 and the sub a gain of 10?

Now I know there's a lot more to this, driver sensitivities, configuration of satellite and sub amplifiers, but in general, am I looking to match the sub's voltage rating to one channel. OR, since the sub is technically taking over for both channels it just has a higher (double) output over one channel. Because, to me, if the subwoofer gain is reduced so that the voltage is sort of linearly amplified, then why do all of these 2.1 systems brag that their subwoofer has a higher output power then their satellite speakers? Is that just because replicating bass frequencies takes more energy to achieve the same spl?

I guess I've just always wondered this and would like it cleared up.

Thanks!
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Old 23rd January 2013, 04:35 AM   #2
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Quote:
Originally Posted by ZLyzen View Post
Is that just because replicating bass frequencies takes more energy to achieve the same spl?

I guess I've just always wondered this and would like it cleared up.

Thanks!
May be you are thinking 2.1 has 2 channel amp and at output we filter the lows and add em up and feed to sub. if so, I guess not
2.1 would have 3 channel amp, 2 for speaker and 1 for sub. sub freq are filtered for both channels and added up and fed to the dedicated sub channel with more power

mid range and tweeters can be more efficient/sensitive than subs

Yes it takes lottts of more power to achieve same loudness in low frequency. I am not sure about SPL but would assume not more power is needed for same SPL at lower level unless driver efficiency/sensitivity changes.
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Old 23rd January 2013, 10:46 PM   #3
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Quote:
Originally Posted by ZLyzen View Post
For 2.1 audio, a common approach I've seen is that the right and left channels are added together after the low-pass and then sent to the sub-amplifier. This would mean, since the low frequency spectrum of music is usually quite similar for both right and left channels, that the voltage of this signal is now double what it used to be. Is this compensated by giving the satellite speakers say a gain of 20 and the sub a gain of 10?
Because, to me, if the subwoofer gain is reduced so that the voltage is sort of linearly amplified, then why do all of these 2.1 systems brag that their subwoofer has a higher output power then their satellite speakers? Is that just because replicating bass frequencies takes more energy to achieve the same spl?
A change in power by a factor of two is only a 3 dB change, twice the power.
A 10 dB change requires 10 times the power.
Doubling voltage is a 6 dB increase.

Most 2.1 systems brag about how much power is used up, not how much SPL is produced .

Small subs are generally less sensitive than the satellite speakers, and most consumers like a "loudness contour" low frequency boost, so it is not unusual to see 10 dB or more power used for a sub than the tops.
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