OTop8 dispersion angle and Bi-amping

[Bill Fitzmaurice]

It will have wider dispersion than all vertical, just as a melded array has wider dispersion than flat, and the SLA CurveArray has wider dispersion than a vertical SLA. However, that wider dispersion comes at the cost of comb filtering. It's not going to be severe the way it is with outward splayed trapezoid boxes, but it will be there. Which way to go depends on the venue.

[Bruce Weldy]

Is something like this a possible set up option?20250127_093830.jpg

I'm not sure what your goal would be, but just FYI... it's a little counter intuitive, in that side-by-side splayed will have a reduction in horizontal dispersion. Which can be used to your advantage if that's an effect you're wanting to achieve. But, it will be a disadvantage if you're thinking it will cover more left and right than a single column. Additionally, a tall column will have less vertical coverage which is useful in reducing the amount of energy directed it the ceiling and floor (indoors) and maximizing the energy delivered to the audience (indoors and outdoors).

Tall thin array = short and wide dispersion pattern
Short wide array = tall and thin dispersion pattern

The crossfire setup he showed is much better than just side-by-side as far as dispersion.

[Keryn O'Shea]

It is, if all vertical isn't possible.

However, that wider dispersion comes at the cost of comb filtering. It's not going to be severe the way it is with outward splayed trapezoid boxes, but it will be there. Which way to go depends on the venue.

Ok, that's good to know, thank you

Tall thin array = short and wide dispersion pattern
Short wide array = tall and thin dispersion pattern

This sounds similar to beamforming with subs, could that be said?
I managed to AutoEQ & give them a 5 song lash with Led Zeppelin, Tash Sultana, Live & Kings of Leon, they were HP at 80hz 38dbBW

Initially l thought the HP was turned off, as there was considerably more bottom end than expected.. but no, it was set. As l increased the volume (l was using my iPod through a headphone amplifier) l realised how much grunt l had at my fingertips! With only the first signal & output lights flickering on the Driverack, it was properly loud & clear but also warm... big smile & goosebumps!
The intelligibility impressed me, l noticed the drums more in the songs played.
Just two more T48s to build & we'll head West for a proper lash of this system

[Keryn O'Shea]

3 painted, 3 more to go..
Thanks for your tips on priming the cabs with flat black & cling wrapping the rollers Bruce, that's saved a fair amount of paint.

[Bruce Weldy]

They look great!

[Tom Smit]

Wow! Look at the size of those things! They're huuuuge. I know it sounds silly, I know that they can be that wide, but, to see them!

[Keryn O'Shea]

They look great!

Thanks mate,
it's taking a quart of primer & a gallon of Duratex per cab

Wow! Look at the size of those things! They're huuuuge. I know it sounds silly, I know that they can be that wide, but, to see them!

They're sizeable yes, however really easy to move around, even the last two which are LAB15s.
You've probably already worked out the bumper strips on the driver access door & top are for trucking them around upside down.. all the weight is down low & back on the trolley
Painting these seems to be taking forever..
I'm also having thoughts even 6xT48s won't be quite enough to match the 8xOT8s, l guess we'll see..
Aiming to be finished painting in the next two weeks, then l can finally hear them all together

[Bruce Weldy]

it's taking a quart of primer & a gallon of Duratex per cab

Yikes!! Per cab?

How many coats are you putting on?

[Keryn O'Shea]

Yikes!! Per cab?

Yes, 1 of primer, and 2 heavy of Duratex.
As Seth said & l agree that keeping the roller saturated gives a better result.
It takes me over an hour to Duratex the mouth area with the small roller, and l'm painting all the way in and up for as far as you can see & a bit more. The rest of the cab is easy.. just slap it on with the large roller, takes 25 minutes.
A gallon of Duratex here is $200au, so with the OT8s included it'll be 9 gallons

[Keryn O'Shea]

Cabs 5&6 are finished..

I'd like to run the limiter values past you guys to check please. There's 3 different drivers: 2x 3015LF, 2x 3015CX & 2x LAB15, one of each on 2 channels of a CVR D2004 amplifier.
Calculating the 2 KL cabs at 10ohm, and the LAB at 8ohm, this is 3.08 ohms, yes?
Setting the limiter for the lower rated 400watt 3015CX, at 35.1v, correct?
I feel the amplifier should be able to handle this, what do you think?
Will there be a noticeable difference in max output:
-Deploying these 6 cabs lined up versus stacking with the V-plate?
-Having to set the limiter to the 3015CX specs?

When set up in a line, it shouldn't matter where the different drivers are, yes? For ease of cabling l was going to go from the inner cab out, LAB-3015CX-3015LF
As soon as the rain leaves us alone I'll be able test this system, can't wait!

[Bruce Weldy]

The amp is 2 ohm capable, so there's no problem putting 3 cabs on a channel. As far as the voltage limit, I'd think you could go more than 39 volts with 8.7 xmax.....of course, it depends on where you plan to high pass them......the lower you go, the more careful you have to be. Even at 40hz, I'd think that 45 volts would be safe for the CX.

Bill would be the final word on voltage limits.

Just realized that Eminence doesn't make the CX in a 15 anymore.

[Keryn O'Shea]

The amp is 2 ohm capable, so there's no problem putting 3 cabs on a channel.

Nice

As far as the voltage limit..

The 35v limit value l came to is with three cabs connected one one channel at 3ohm. The plans state 35hz HP is acceptable with four or more cabs, l'm hoping not to bash the limiter too much, but if l do, l want to be within a safe envelope.

I'd think that 45 volts would be safe for the CX.

Yes, if it were on it's own channel at 10ohm..?

Just realized that Eminence doesn't make the CX in a 15 anymore.

Yes, l don't want to cook it!

[Bruce Weldy]

The 35v limit value l came to is with three cabs connected one one channel at 3ohm. The plans state 35hz HP is acceptable with four or more cabs, l'm hoping not to bash the limiter too much, but if l do, l want to be within a safe envelope.

Voltage is voltage. The impedance rating lets you make sure you don't overload the amp with too little resistance. The voltage is the same whether there are two speakers or three.

Whether there are 2 cabs or 6 cabs, the amp is still putting out the same voltage and driver still has the same excursion. Lowering the high pass means more excursion. If you are going to try to get down to 35hz, then I'd definitely pull the limit down to the 35-40 volt range to keep things safe. I could be wrong, but unless Bill adds his 2 cents, I'd stay on the safe side.

[Keryn O'Shea]

..Whether there are 2 cabs or 6 cabs, the amp is still putting out the same voltage and driver still has the same excursion..

Oh! I thought the limiter was set to the total impedance on that channel, which is lucky for me as that makes it a conservative setting.
When inputting the data to the limiter calculator:
-Is the subwoofer limiter is best calculated for the 3015CX, at 8ohms, or 10 (Driver 8ohm, plus 2 for horn loading)?
-The midwoofers are 360w/16ohm per cab, l'd input 180w/16ohm? 53.7v
-The HF CDs are 120w/16ohm per cab, so 60w/16ohm? 31v

[Bill Fitzmaurice]

The limiter is set for the maximum voltage of the weakest link in the chain. When all of the cabs/drivers are parallel wired impedance doesn't enter the equation. Xmax does.