[navin]

Originally Posted by naughty001

Not necessarily only T/A. .. Its the basic fact that no matter where the speakers are situated if the sounds from them all arrive to your ears at the same time then it seems like they all came from the speaker that has most of the frequencies playing or whichever speaker is louder

its all about your tuning and also how good your equipment is because its easier to create this "upfront bass" illusion with better quality speakers and a bit of tuning work which could or might not include time alignment adjustments and phase and polarity adjustments as well as volume level adjustments and frequency equalization to ensure that the conditions are correct for this illusion to come about

While one can create the upfront bass effect without T/A (careful selection of crossover points, slopes, phase, etc..) T/A just makes the job easier.

[gigy]

Frank, just to find out although must have done it , how have you connected the subwoofer? reverse polarity?

[frankmehta]

Normal polarity. My amp/head unit both have phase reversal options

[gigy]

Dose the phase reversal thing make the subwoofer move in the opposite direction? have you tried it already?

[Bass&Trouble]

Originally Posted by gigy

Dose the phase reversal thing make the subwoofer move in the opposite direction? have you tried it already?

I didn't get what you mean by that. It's not like a changed direction of movement of the cone can be judged by looking at the sub in operation, playing a music signal, in different polarities.

[nitrous]

Originally Posted by gigy

Frank, just to find out although must have done it , how have you connected the subwoofer? reverse polarity?

Thats the first thing B&T or Frank would have done.

[gigy]

What i ment was connecting amplifier positive to subwoofer negative. you can see the movement of the cone reverses with it with the thumps. Read in mp3car that when subwoofer is mounted inverted the connections needs to be reversed else it would sound muffled.

[navin]

Originally Posted by gigy

Read in mp3car that when subwoofer is mounted inverted the connections needs to be reversed else it would sound muffled.

this internet thingy is dangerous, google just maks it easier to get to such mis-statements. in the old days when we read books there was an editor and technical team (for engineering books atleast) that sifted through such mis-statements.

reversing the connection on speaker (any speaker - subwoofer, tweeter, etc....) makes it 180 deg out of phase. that is it. if it sounds muddled it is because the sound from all the drivers are not in phase. the muddled sound has nothing to do with connections of the drivers.

if you study old published crossover networks you will see that for 2 way, 2nd order networks the writer often reversed the terminals of the tweeter section. this is because 12db/oct netwroks shift phase by 180 deg and by reversing the tweeter connections (adding another 180 deg phase shift) the writer was in effect making the tweeter in phase with the woofer (there are some other acousitc phase shifts that happen depending on the topology of the drivers on the baffle but that is another story).

Originally Posted by navin

this internet thingy is dangerous, google just maks it easier to get to such mis-statements. in the old days when we read books there was an editor and technical team (for engineering books atleast) that sifted through such mis-statements.

reversing the connection on speaker (any speaker - subwoofer, tweeter, etc....) makes it 180 deg out of phase. that is it. if it sounds muddled it is because the sound from all the drivers are not in phase. the muddled sound has nothing to do with connections of the drivers.

if you study old published crossover networks you will see that for 2 way, 2nd order networks the writer often reversed the terminals of the tweeter section. this is because 12db/oct netwroks shift phase by 180 deg and by reversing the tweeter connections (adding another 180 deg phase shift) the writer was in effect making the tweeter in phase with the woofer (there are some other acousitc phase shifts that happen depending on the topology of the drivers on the baffle but that is another story).

But to be honest i would expect this situation reported in MP3car to be correct since when you reverse the actual physical driver ie face the cone into the box and wire it in correct polarity as compared to the other drivers you would have the speaker cone moving down when the others are moving up whilst it would be moving up whilst the others are moving down

this in essence is out of phase but again because of absolute phase being dependent on wavelength and distance you might have needed the sub to be out of phase anyway in order for it to be inphase so to me its a matter of listening for any obvious cancellations before reversing the polarity

but inverting the subwoofer will definitely take it out of phase as far as i can figure it out because the signal mechanically takes it out of phase but as i have said the distances involved in the wavelength could have already created a situation where having the polarity correct actually reversed the phase and even if you did not have the magnet facing up you would have had to play around with the polarity of the subwoofer to get it in phase

the more out of phase it is the more you hear it as a segregated sound, whilst the more in phase it is the more you would hear it as an integrated sound that makes it seem as if the sound from the subwoofer actually is coming from the front and is actually emanating from the speakers that you can see ie the front stage

the reason for this is generally that with subwoofers the wavelength is generally longer than the vehicle which is why most times you actually hear it peaking outside the vehicle and the spot where it would be perfectly in phase is also a distance away that is outside the vehicle. so this is the reason why you still have to play around with the polarity of the sub anyway. This is as i know it, and its mostly theory but its been something thats served me well because even with the magnet facing inside the enclosure there have been times when i have had to reverse the polarity of the sub in order to get the phase correct and make the sub sound upfront

[santosh.s]

I think if TA is adjusted using measuring tape, then polarity thing mentioned by gigy or mp3car should be considered. If it is done using "ears" (which I would prefer any day), then it should not matter. Because in later case, reverse mounting of the sub should be taken care automatically.

BTW, I always wondered about one thing- is polarity reversing exactly equivalent to 180deg phase shift or TA delay? I think no, because phase shift or TA delay is like literally delaying signal by certain time, whereas polarity reversing does not really "delay" the signal as such. For all practical purposes it's effect may be close to adding 180deg phase shift independent of frequency, or frequency dependent delay, though.

I think no, because phase shift or TA delay is like literally delaying signal by certain time, whereas polarity reversing does not really "delay" the signal as such. For all practical purposes it's effect may be close to adding 180deg phase shift independent of frequency, or frequency dependent delay, though.

ah but the question you are not asking is how do they electronically delay the time, the thing is most time alignment processing is basically phase and amplitude adjustment. Thats the electronic process. its not magically playing around with time, its more manipulating the parameters to affect arrival times

think of it, how do you take a recording thats already been recorded and during playback tell that recording to slow one side from playing a couple of milliseconds after another considering that audio signals are merely electrical pulses moving in wires. Its more manipulation of the electromechanical factors to affect the psychoacoustic factors ie to fool your ears into thinking that these things are delayed but it isnt really delayed. but the arrival time of the sound is affected by these manipulations and adjustments, for example your first adjustment would be a certain number of degrees different in phase and maybe a bit softer - whilst your next adjustment would be a few more degrees different and even softer and then the next adjustment would just be a few more degrees different and even softer. You could get more or less similar effects by placing speakers in different places and adjusting volume levels independently

have you never ever experimented to shift your centre image by playing around with the balance control only - it works because all you are doing is making one side softer. Obviously time alignment is adjusting that same balance but with finer increments for greater accuracy while adjusting the phase at the same time which is why electronic time alignment seems to delay the sound but it isnt technically really delay as such cos its not like when you are walking on a treadmill and you adjust it slower so you have to walk slower so you delay the amount of time that you actually walk. There is no way i can think off that you could create a real situation for delays like that with electrical signals

[Bass&Trouble]

Originally Posted by gigy

What i ment was connecting amplifier positive to subwoofer negative. you can see the movement of the cone reverses with it with the thumps.

How can someone be able to "see" the reversal of cone movement when it is typically moving at anything between 20 to 80 cycles per second. Trust me, this is not possible. The only time you can do this is if you feed it a DC signal. In which case, it will stay stuck at either the outer or inner limit of the cone's travel.

Originally Posted by gigy

Read in mp3car that when subwoofer is mounted inverted the connections needs to be reversed else it would sound muffled.

Yes. If it is with respect to other subwoofers installed in a normal fashion, then the inverted ones have to be in "opposite" polarity of those mounted normally. Does not mean that those mounted inverted have to be in reverse polarity, and the others in normal polarity, or vice versa. It could be either.

[santosh.s]

@naughty001, I don't think TA messes up with balance or volume, there is no need. TA and polarity change are probably among easiest functions to implement in digital world. For TA you have to just "delay" it by certain number of samples, while for polarity change you can change the sign of all samples, isn't it? Even for analog signals, polarity change is just a matter of flipping wires, while adding delay is somewhat more complicated and destructive.

Originally Posted by santosh.s

@naughty001, I don't think TA messes up with balance or volume, there is no need. TA and polarity change are probably among easiest functions to implement in digital world. For TA you have to just "delay" it by certain number of samples, while for polarity change you can change the sign of all samples, isn't it? Even for analog signals, polarity change is just a matter of flipping wires, while adding delay is somewhat more complicated and destructive.

when you adjust one thing it affects other things, so even using DSP in the digital domain to align drivers in differing distances, in order to keep the sound coherent you will be adjusting other things like phase and amplitude. Read this for a more overall picture on T/A

Live Sound International | Tech Talk: How to correctly get loudspeaker drivers in sync

[frankmehta]

This is slowly becoming like one of ibm_jennifer's technical jargon threads. All talk, no play. Lol.