[NIP]

guys...what is the Normal and Reverse sub setting on HU ?! it makes a slight difference when i toggle the settings...but how does it work technically !?

[low_bass_makker]

It is like reversing the polarity of the sub (in phase or out of phase)

or we can say physically changing wires of the sub

[NIP]

how does it matter ?! what difference does this make ?!

[low_bass_makker]

try this wire one sub reverse as shown in the above diagram and remain the other sub as normal this make the sub output out of phase thus canclling the output of each other. you will notice that the bass output will drop to great extent

this same feature is the sub normal and reverse.....

[Bass&Trouble]

The adjustment is offered for correction of a phemoenon termed as reverse polarity. It causes phase cancellation at the frequencies concerned. It has to do with the fact that audio signals are elementarily sine waves, and have peaks and troughs. So while co-incident peaks and peaks, or troughs and troughs, would add and produce more amplitude, a peak coinciding with a trough would result in cancellation rather than summation and produce lesser audible output while the amount of power utilized is the same. This is usually not desirable.

To cite an example, this effect is practically evident when in audio systems, there are full range speakers playing low-bass and thus overlapping into the region the subwoofer is playing. If they are not in identical phase, there will be a suck-out in the bass region which they are commonly playing. This is fairly noticeable.

Even more pronounced, is the effect when 2 subwoofers are connected in reverse polarity. Both diaphragms will move, but there is no audible bass. The most murderous situation has to be when a single dual voice coil subwoofer has both coils wired in reverse polarity. You can turn it up as much as you want, but the cone will refuse to budge, and there will be no bass. This is disastrous if the amp is a powerful one relative to the subwoofer, since there is immense tensile/ compressive stress in the moving parts, in addition to heat build-up because the cone is not moving adequately to cool the voice coil. These cannot be solved by switching the phase on the head unit since the head unit will reverse polarities on both coils, when actually only one has to be corrected.

Variable phase controls are also offered on certain subwoofer amplifiers to enable to perfectly align the phase of the subs with the rest of the setup, or with some other sub(s) in the case of multiple subs placed at different locations. These are variable continously from 0 degrees to 180 degrees.

Listening can help effectively correct 180 degree phase anomalies in good setups with the right program material. If the subs and some full range speakers are interfering, it's a good idea to play some music with a recurring kickdrum, assuming that parts of that frequency would be reproduced by both, the speakers and the subs, and by alternating phase on the HU one can quickly identify which is a more realistic and resounding kick-drum sound.

[NIP]

thanks for the enlightenment B&T....that was very informative indeed !!

[kb100]

Yup... truly is... will be a good addition to the Glossary thread dont you think???

[navin]

Sam, Sam read post 5. What does it remind you of?

[Bass&Trouble]

Originally Posted by navin

Sam, Sam read post 5. What does it remind you of?

I'm curious, what would it remind him of?

[Sam Kapasi]

I'll tell you.

It reminds me of NAVIN, who successfully scared many out of this forum, till we begged him to water down his superbly technical posts.
Your post, B&T, though perfect in every technical detail, will cause the average reader to black out completely halfway through

[navin]

Originally Posted by Sam Kapasi

I'll tell you.

It reminds me of NAVIN, who successfully scared many out of this forum, till we begged him to water down his superbly technical posts.

and then they made me a Mod. Go Figure!

[drpullockaran]

If you would go into the details of the Bose noise cancellation headphones it is this principle of "out of phase sounds" that is use to good effect to cancel out sound coming in from the environment outside of the headphones. Going to their site will clear some doubts one might have on the functioning of these very expensive headphones. Bye and wear your seatbelts

[low_bass_makker]

Originally Posted by Bass&Trouble

The most murderous situation has to be when a single dual voice coil subwoofer has both coils wired in reverse polarity. You can turn it up as much as you want, but the cone will refuse to budge, and there will be no bass. This is disastrous if the amp is a powerful one relative to the subwoofer, since there is immense tensile/ compressive stress in the moving parts, in addition to heat build-up because the cone is not moving adequately to cool the voice coil.

an the results are here with example.......

http://rapidshare.de/files/28543688/coilburn.1.wmv.html

[kkr2k2]

Originally Posted by Sam Kapasi

... will cause the average reader to black out completely halfway through

i think i am the first victim. couldnt understand anything .

[satish_appasani]

Originally Posted by kkr2k2

i think i am the first victim. couldnt understand anything .

kkr, the last post was in August 2006, so i am assuming you were trying to understand this post for the last 5 months (as you joined in Sep 2006) and finally gave up.