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I have a problem room....

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I have a problem room....

Postby Craigslee » Thu Jan 09, 2020 5:59 am

Hi all,

I have a set of QSC KS212 Super Cardiod Subs and QSC K12.2 tops for my FOH. I have a room that is posing some problems for me and seek some guidance.

The stage, with a full length single step to the LHS, has a smallish dance floor in front of it, and I'm reluctant to use up too much of that space if possible.

The KS212C subs are approx. 3' deep and QSC recommends they be at least 15" from any wall (in this case, the permanent stage (which is 15" high). That being the case, I would protrude 41/2 feet in front of the stage if I wanted to place them on the floor either at a left/right or a central cluster configuration. Furthermore, with the subs centrally positioned in front of the stage, I would probably place my foldback wedges on the subs (they are at a similar height to the stage).

Another option is to place the subs on the timber framed stage with the tops on poles over the subs, however QSC (and most manufacturers don't recommend the left/right sub under tops configuration).

So, my question is, what would YOU do? I'm all ears!

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Re: I have a problem room....

Postby Sam Spoons » Thu Jan 09, 2020 11:39 am

I'd put the subs together on the floor stage right* and the tops in the usual one either side configuration.

* How to the cardioid subs react to each other in a cluster though?
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Re: I have a problem room....

Postby Craigslee » Thu Jan 09, 2020 12:25 pm

Hey Sam, side by side they need to be a minimum of 15" apart. They work well clustered or one on top of the other.
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Re: I have a problem room....

Postby Sam Spoons » Thu Jan 09, 2020 1:22 pm

One on top of the other then, stage right? Or side by side with a 15" gap. Stage right seems the sensible place as long as you can avoid them being in the way of punters coming into the room. Do you need both or could you run with just one sub (I only have one conventional sub in my QSC rig, an old EV sBA750)?
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Re: I have a problem room....

Postby Craigslee » Thu Jan 09, 2020 9:03 pm

Yes Sam, I was actually thinking just one might be adequate. They are rated at 3600w each. I'm guessing that's peak, so 1800 continuous.
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Re: I have a problem room....

Postby Sam Spoons » Thu Jan 09, 2020 9:32 pm

The max SPL is a better indicator with powered speakers, my QSC K12s do 131dB SPL the mk2 you have 1dB louder. My sub quotes 128dB but, in practice, I find myself turning it down more often than wishing it was louder.

The KS212C manual says they are 1800 watts peak not 3600 (that's the KS118), they still have 132dB SPL available so one could well be enough. But the manual suggests stacking two KS212Cs in a horizontal orientation. You only lose 2.5dB front to rear attenuation and the stack can safely support a pole mounted top cab so that would be my choice if a single sub proves inadequate or you just want to play safe.
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Re: I have a problem room....

Postby Craigslee » Thu Jan 09, 2020 9:44 pm

Thanks Sam, the specs state 2x1800w (3600w). I agree with you, stacked for sure if one is not sufficient. I'll probably setup both in a stacked config, run one and see how that goes for future gigs, and fire up the 2nd if it's required.

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Re: I have a problem room....

Postby Sam Spoons » Thu Jan 09, 2020 9:58 pm

You are right, my mistake :blush: .

However the Max SPL figure is the most relevant WRT powered speakers as it takes driver efficiency into consideration. Either way I concur, seting up two in a stacked config and trying one to see if it works makes complete sense.

Have a good gig :thumbup:
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Re: I have a problem room....

Postby Craigslee » Thu Jan 09, 2020 10:02 pm

Thanks Sam, I will definitely come back with some results in about a fortnight!

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Re: I have a problem room....

Postby Craigslee » Thu Jan 09, 2020 10:05 pm

Just to be clear, when you state *right... you mean the Right Hand Side as if I were looking at the band/stage (i.e.) adjacent the wall with the shelf?

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Re: I have a problem room....

Postby Sam Spoons » Thu Jan 09, 2020 10:21 pm

No, sorry, theatre speak for the position related to the view from the stage. Actors refer to the positions on stage from their perspective (and, occasionally, those from the audience perspective as "House Left/right etc) so next to the corner of the stage nearest the bar, asuming there is room (hence my comment about them maybe causing a problem with audience access).
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Re: I have a problem room....

Postby Craigslee » Thu Jan 09, 2020 11:14 pm

Great, thanks Sam.

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