DIY Time Alignment.

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#21
jol50 said:
In the old days we would always try the tweeters/mids/or subs out of phase. It affected the sound at the crossover point, depending on where they were at and overlap they had. If you had midbass boom running the subs out of phase cut it down as it canceled the frequencies at the overlap in the midbass area. The change in phase might also change the sub sound. If you had active crossovers you would move them around also when you did that.
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Ah, the good ol' days
😀 wasn't it great! now we have to deal with mp3's and DSP

oh well.
 
#22
Dan2 said:
just thinking now - if you adjust the sub to blend in with front mids, then it won't integrate with rear mids, so it will never be perfect (unless maybe delaying the front speakers😕 )
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you don't need rear speakers in a sq stereo(2ch) system. 5.1 is different.

when you TA the fronts with the sub, the bass is right upfront and it sounds like all the bass is being reproduced by the front speakers.

To quote a friend(navin advani) The presence of the sub should not be felt. The absence should.

cheers
 
#23
Eva said:
Don't underestimate the usefulness of all-pass filters at low frequencies, they come quite handy when wavelenghts become long, for example 90 degrees of 160Hz is already over half a meter delay.
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So if I was to build an op-amp based active crossover, could I simply add lots of all-pass filters in the circuit for my sub channel? Then make each all-pass filter have a bypass switch so I could bypass them all for no delay, and not bypass them for some delay? So the less bypassed filters, the more delay.

For example 100Hz, each full wave is 10ms. 1 all pass filter at 1/4 wavelength (90 degree phase) = 2.5ms delay?

I assume that each all-pass filter will add some noise, but as this is a sub channel that is not the end of the world is it?

I'm not really going to try and attempt to delay my left of right channels, I know there is a difference, but I'm happy with them as they are (for now)! 🙂
 
#24
It's the front system what you have to delay because the subwoofer is the speaker furthest away from you and the one suffering the highest acoustic group delay.

All-pass filters are adjustable. For example, you could use 4 stages and 4 variable resistors to get a 0 to 2m delay range valid up to 170Hz. The highest frequency where delay is still good increases as the delay is reduced.

You can use one or two more all-pass stages to compensate for the inherent group delay of bandpass enclosures (or straight boxes tossed in trunks). The effects of this group delay is cancelled by applying a similar group delay to the front system. Group delay compensation comes handy too when tweeters and mids are used near their lower cutoff.
 
#25
have you tried to simply adjust the gains on both amps? itll probably get you 50% of the way there alone.

or

experiment with reversing phase of your components one by one?

a cheap form of time alignment is to simply bypass the crossover for the speaker farthest from you, but the louder you turn it up the less affect it will have. 😉
 
#26
Thread Revival!
What electrical component is used to make time alignment/delay circuits? The delay needed is both left to right, front to rear and sub to the rest of the system? Can the delay be done passively between amp and speakers like a passive crossover?
 
#28
This type of delay circuit looks to be a bit easier to construct than I thought. I think it all depends on a particular digital processor and then figuring out how to control and adjust it. I think it could be installed like a PLLXO on the input side of an amplifier or rather between an active crossover and amplifier. One per channel except on the driver farthest from the listener since the delay needs to match it.
There are some inexpensive guitar delay box pedals that incorporate a few pre set delay values, I wonder what they use?
Surely someone here has experimented with this but maybe in another section on this forum.
 
#30
If it doesn't run at near 12v single rail after the internal transformer you could check each rail's voltage. You may even be able to parallel your amp's preamp power supply rails to the delay to power it. PPI used to run their preamp power rails through the din jack so they could power their processors and eliminate noise, you could try a similar method if you're crafty enough.
 
#32
After further review, discussing it with a co-worker and finding a couple of schematics online, it would be much more feasible to buy a DSP EQ unit. A basic delay circuit can be done DIY but to make it with fidelity in mind is where it gets a bit more complicated not to mention ease of adjustment and storing memory etc.
 
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