SAC gig report....

[Donnie Frank]

Jeff,

What would be interesting would be to see if you can reproduce this fix in another room. All the math in the world is trumped by a little experimentation. Good for you for thinking out of the box. BTW, what did you use to the delay the stacks? Bob's delay?

[soundchicken]

He's a bassist... he doesn't need time aligning, he needs tequila aligning.

[Jeff Scott]

Jeff,

BTW, what did you use to the delay the stacks? Bob's delay?

I used this little VST that I picked up off of the KVR website. Called RS Exact Delay

http://www.kvraudio.com/product/rs_e..._rough_surface

[RBIngraham]

I used this little VST that I picked up off of the KVR website. Called RS Exact Delay

http://www.kvraudio.com/product/rs_e..._rough_surface

Just curious, why not just use the delay plug that's included with SAC?

[Jeff Scott]

I like the idea of being able to enter the input in increments smaller than 1ms.

[airickess]

Just curious, why not just use the delay plug that's included with SAC?

I've used the included delay plug-in successfully for speaker delays, but one does have to jump through a few hoops to make it work. It appears that the plug-in linked by Jeff has a much more straightforward design for this task.

[RBIngraham]

I like the idea of being able to enter the input in increments smaller than 1ms.

Good point. I don't think it really makes that much difference unless you're doing driver alignment within a box. (i.e making a crossover) But it's nice to have the option to really dial it in properly.

[RBIngraham]

I've used the included delay plug-in successfully for speaker delays, but one does have to jump through a few hoops to make it work. It appears that the plug-in linked by Jeff has a much more straightforward design for this task.

Also true, but the included delay is controllable via a SAC Remote which is why I always just stuck with that. As well as stability. Less 3rd party stuff the better to me.

[Brent Evans]

+1 on that. I assumed the bass player was complaining of super frequencies, not sub frequencies. A 100Hz wave is omni and 11 feet long. 50Hz wave is twice that length. So it's funny to see people "time align" subs..

That's exactly why you DO time align subs. Phase is an angle, not a switch. At 100hz, 5 feet is 180 degrees out of phase, meaning you'll have a perfect null. 2.5 feet at 7.5 feet are 90 degrees (and 270 degrees, if you want to get technical) out of phase, so you'll have a partial null. The degree of interference thus varies with the phase angle, which can be anywhere from zero to 360 degrees out of phase.

When you get past 360 degrees, you're a wavelength plus an angle, so your interactions lessen with each sweep around the phase circle because one waveform has less amplitude than the other, per the inverse square law.

By time aligning, you keep all the wavefronts in phase with each other and create constructive interference instead of destructive interference.

I'd post an article, not that you'd read it, but this explains it somewhat:

[RandyHyde]

By time aligning, you keep all the wavefronts in phase with each other and create constructive interference instead of destructive interference.

You have to be careful, though. This is in one direction and works well *beyond* both sources. In between the sources (as is the case here) you've got a complete mess. The "perfect delay" to put things into phase changes depending on your position.

For example, I typically use cardioid subs in my larger shows. The effect is quite amazing in FOH (in front of all the speakers, where the sound combines constructively) and on the stage (behind all the speakers, where it combines destructively @60Hz in my case) but if you stand between the two sets of subs (they're about 2' apart in my case) the sound gets really weird.

Cheers,
Randy Hyde