Time Alignment vs. Phase Shift

[helotaxi 5,000+ posts]

That Alpine unit is a PITA to work with. I had one until it met with an unfortunate accident involving a short circuit.

Phase shifting is completely different and not nearly as useful as TA. They are distantly related in that phase is affected by the time domain.

 

[Sarthos 10+ year member]

Let's see if this works. Here's a hypothetical graph for a note played at 1000 Hz, with the front left speaker 2 feet from the driver's ear, and the front right speaker 6 feet from the driver's ear.

http://graph-plotter.cours-de-math.eu/graph.php?a0=2&a1=sin%281000%2A%28x-0.001776%29%29&a2=sin%281000%2A%28x-0.005329%29%29&a3=sin%281000%2A%28x-0.001776%29%29%2Bsin%281000%2A%28x-0.005329%29%29&a4=1&a5=3&a6=7&a7=1&a8=1&a9=1&b0=500&b1=500&b2=0&b3=0.01&b4=-2&b5=2&b6=10&b7=10&b8=5&b9=5&c0=3&c1=0&c2=1&c3=1&c4=1&c5=1&c6=1&c7=0&c8=0&c9=0&d0=1&d1=20&d2=20&d3=0&d4=&d5=&d6=&d7=&d8=&d9=&e0=&e1=&e2=&e3=&e4=14&e5=14&e6=13&e7=12&e8=0&e9=0&f0=0&f1=1&f2=1&f3=0&f4=0&f5=&f6=&f7=&f8=&f9=&g0=&g1=1&g2=&g3=0&g4=0&g5=0&zalt=

The blue line is that of the driver's side speaker

The red line is that of the passenger's side speaker

The green line is that of their overlap

As you can see, the two waves mostly offset each other. The result is that the two speakers aren't as loud combined as either individual speaker

Now, if the driver's side speaker is delayed

http://graph-plotter.cours-de-math.eu/graph.php?a0=2&a1=sin%281000%2A%28x-0.005329%29%29&a2=sin%281000%2A%28x-0.005329%29%29&a3=2%2Asin%281000%2A%28x-0.005329%29%29&a4=1&a5=3&a6=7&a7=1&a8=1&a9=1&b0=500&b1=500&b2=0&b3=0.01&b4=-2&b5=2&b6=10&b7=10&b8=5&b9=5&c0=3&c1=0&c2=1&c3=1&c4=1&c5=1&c6=1&c7=0&c8=0&c9=0&d0=1&d1=20&d2=20&d3=0&d4=&d5=&d6=&d7=&d8=&d9=&e0=&e1=&e2=&e3=&e4=14&e5=14&e6=13&e7=12&e8=0&e9=0&f0=0&f1=1&f2=1&f3=0&f4=0&f5=&f6=&f7=&f8=&f9=&g0=&g1=1&g2=&g3=0&g4=0&g5=0&zalt=

In this graph the two speakers have perfectly matched waves, which are indistinguishable. As you can see from their resultant, it is far larger than the original green wave before time alignment was added, in fact it is double the volume of either individual speaker. That is perfect overlap.

High frequencies suffer the greatest offset. To figure out how far offset a wave is, multiply the frequency of the note by the distance difference in the distance between the speakers and divide it by 1126. That is the offset of the sine wave. If the number happens to equal 3.14159... you (theoretically) have perfect cancellation. In this example 1000 Hz will suffer a lot since 1000*(6-2)/1126=4.44, which isn't total cancellation, but it's still bad. In this example of a speaker 6 feet away and one 2 feet away the speaker will have complete cancellation at 884 Hz, as well as any multiple of 884 * (2n+1) so 884, 2652, 4420, 6188 Hz, etc. will all be cancelled nearly completely. This is devastating to sound quality.

I could continue with calculations on this, but instead I'll just state the fact that this is a problem more with high frequencies than with low frequencies. a note at 1000 Hz has a wavelength of just over a foot, but a frequency of 40 Hz has a wavelength of over 28 feet, so the distance between different subs won't make a big difference. But with high notes that have frequencies of a foot or less are easily thrown off by the difference in distance between the speakers.

 

[dumple 5,000+ posts]

my eclipse cd5030 does it automatically but im subscribing to learn

 

[helotaxi 5,000+ posts]

The benefit of time alignment over a phase shift processor is that time alignment affects all frequencies correcting for distance differences. Phase adjustment only works for one freq and its harmonics but makes a mess of other freqs in the process.

 

[Sarthos 10+ year member]

**** computer going back a page everytime I hit backspace

Too bad about the phase shift on amplifiers. If it was a 100% digital shift it might work right, but it's not. It'd have to separate every frequency and shift them separately to really improve sound. Or you'd have to run like 50 way component speakers on an active setup.

Any recommendations for an external time alignment processor?

 

[helotaxi 5,000+ posts]

Alpine H701. The Alpine that was pictured above. The PPI DCX-730. JBL used to make an analog one.

The phase adjustment on an amp assuming that it is infinitely variable rather than 0/180 does have a purpose. It can do a lot to smooth out the transition between the mids and subs by adjusting the phase relationship at the point where both sets of drivers are still playing.

 

[Sarthos 10+ year member]

Yes it can. Not as nice if it doesn't adjust each frequency separately, but if it is variable like a knob as opposed to a switch it is useful.

And holy crap that Alpine would have to be dang nice for that much. I already have a 30 band x 6 channel EQ so it's almost completely redundant. I would've gone with the Alpine instead if I would've known about it at the time.

 

[helotaxi 5,000+ posts]

Impossible to adjust every frequency separately. Even with a digital processor. Not only would you have to adjust every whole frequency but also every fraction of a Hz. You would effectively need an infinite number of adjustment points. Completely pointless since the whole thing can be accomplished with time alignment and steer the soundstage in the process.

 

[whitedragon551 5,000+ posts]

Heres some info I have out of my CD7000 manual pertaining to this:

From what I gathered at other sites this equation is basically spot on and its very easy to do. Takes about 5 minutes to figure out TA for each speaker.

 

[Sarthos 10+ year member]

Time alignment isn't *quite* the same. Time alignment will let your speakers have matching sine waves when they reach your ears. Phase shifts will let your notes have maximum amplitudes when they reach your ears. Yah it'd take a ridiculous number of phase shifts, not quite infinite, but if someone did have a setup to do phase shifts for every 1/5 of a Hz it'd sound unbelievable. And that'd only require like 100,000 shifts

 

[emilimo701 10+ year member]

lulz

poast dumperz shud b bannd

 

[12voltz+- 10+ year member]

lookin to the ms8 "did a install and factory speakers in a new 300 used the ms8 to amp the factory's and it actually sounds freaking great and a good listening volume not much volume due to the factory's speakers and small internal amp the ms8 has but deff a great sounding unit a lot easier to use them out other like the alpine or the dqsx ect

 

[emilimo701 10+ year member]

The benefit of time alignment over a phase shift processor is that time alignment affects all frequencies correcting for distance differences. Phase adjustment only works for one freq and its harmonics but makes a mess of other freqs in the process.

i wouldn't say phase shifting only affects "only one" frequency. sure, it will help if you have a couple of low frequencies canceling each other out though.

phase shifting changes the polarity of the alternating current going through your speakers. everything is exactly in original time alignment.

time alignment delays certain channels to compensate for certain speakers being further away from the listener. Sound waves, just like any other waves, are not instantaneous. They travel at constant, slower-than-optimal speed(s).

 

[helotaxi 5,000+ posts]

Phase shifting only works at one frequency, it affects all of them but as soon as you move any distance from the speaker, the relative phase of every frequency is different. If you shift the phase to correct a cancellation or reinforcement node at one freq, you've created a bunch of other nodes.

I'm well aware of what TA does. If you delay all but the farthest driver, you've effectively changed the relative phasing as well.

 

[Louisiana_CRX 5,000+ posts]

I do it the simple way buy something with a built in mic and let it take care of all phase and alignment issues...