Otop12 integration

[Wylandright206]

Over the weekend I deployed 2 otop12s per side and I decided to go with 1 cabinet per amplifier/processing channel, to experiment with integration. I stuck a mic in front of the stack and measured them both individually, and messed around with alignment simulations. I came to the conclusion that one should ideally use these square cabinets with 1 cab per channel as they simply do not sum properly without delay. I have attached screengrabs of my simulations below. The summation between the two enclosures where the early cabinet sees .78ms of delay is the clear better option and you can see this in the time and frequency domain. This sounded MUCH better than vertical otop arrays we have deployed in the past.

[Wylandright206]

Photos of the deployment in question. Lol yes we straightened out the crooked stand, I just thought the giraffe was funny

[Bill Fitzmaurice]

Distance to the mic? Mic height? Ideally you want it on the axis where the two cabs meet. With the cabs that high and the mic relatively close you'll see some phase zits that should smooth out with distance.

[Wylandright206]

Yes it was exactly that. On axis about 1 meter from the center of both cabinets with a boom stand. I should have tried measuring this from the floor as well, though getting proper alignment from the source would result in higher efficiency overall. This was easily my favorite deployment of these tops. I have observed this phase mismatch when verifying enclosures in a stack and did not realize it could be mitigated with delay. I'm also fairly new to line array processing so . I would imagine that the version of this box with the curved expansion and trapezoidal enclosure would be superior in this regard. Better integration, and less beaminess from the conical horns constant expansion. It makes me want to build some of these versions of the otop lol

*Edit: I should clarify I did move the mic around in front of the stack of tops and eventually settled on equidistant on axis, which is what these simulations represent. Though, it did not appear to make a huge difference. The mismatch was there regardless of mic placement.

[Seth]

As always Wyland, I appreciate the report!

Looks to me the bottom of the lower cab is about 7 feet above the ground, which is good. Just for the sake of conversation, I wonder if the improvement in SQ you perceived with the delay could or would be duplicated by tilting the array downward, making each cab more equidistant from the listening position. Am I misunderstanding or perhaps over thinking, that applying the delay is possibly contributing to some beam forming of some of the frequency range, perhaps downward towards the listening position?

[Bill Fitzmaurice]

Try it again at a normal listening distance.

[Wylandright206]

This certainly warrants more testing. But I would imagine that if they are not aligned at the source where they are supposed to be coupling optimally for maximum efficiency, you are throwing away output, and coherence. I don't think the otop is exactly missing out on output, however, personally, I am a glutton for precise time alignment. They do tend to smooth out in the context of the room, however if the starting point were aligned it could be smoother and louder. I personally do not think the tradeoff is a bad one. I buy these symetrix processors for 300 bucks on eBay the last one had an expansion card for 12 output channels. Now this rack has 24 output processing channels. Lol I can spare 4 for the tops.

[Bill Fitzmaurice]

The only way to know is by testing them at a distance with and without the time align. There are factors that influence the result with close measurements. That's why I measure at no less than 2 meters, while Tom Danley measures at 10 meters.

[Seth]

Wyland, I'm not entirely understanding. Are you saying two cabs that are as nearly identical as they can be, are measuring differing phase responses and therefore aren't 100% coupling? Or, is it the tweeters to the mid drivers phase response? If it's cab to cab, I'm curious what primary contributing factor would be causing a large enough variance to be caught in response testing, let alone an actual and discernably audible misalignment. Perhaps loose driver manufacturing tolerances?

Don't take this the wrong way, but I highly suspect you may be hearing what you want to hear more than an actual change in the sound quality. I only say so because it's something I've personally experienced myself with myself and artists I've worked with also do it all the time... and then swear there was SOMETHING different, when there wasn't at all. The only way to tell is quality measurements, and when it get's to that point, more times than not it's just because I'm geeked out on something in particular more so than actually refining the sound for an audience that will never know the difference.

That said, I am genuinely interested in this conversation and understanding the problem and solution.

[himhimself]

The summation between the two enclosures where the early cabinet sees .78ms of delay is the clear better option

Wyland, when you say the early cabinet, are you referring to the lower OTop, meaning it is a little closer to the listener? Making me wonder how this would work with my JArrays since I typically have the bottom cab angled slightly down.
BTW, are you able to check your PMs? Tried sending you a few messages back when I was in the neighborhood some weeks back. Was hoping to catch you at Vice.