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Subwoofer to compliment 2x QSC K8 1000w

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Subwoofer to compliment 2x QSC K8 1000w

Postby Math335 » Fri Nov 22, 2019 6:01 am

Hello,

I am looking for a powered subwoofer to complement two QSC K8 1000 watts that I already have. This is for a room of about 700 square feet for a maximum of 80 persons (more often 60). The speakers and sub will be connected to a Yamaha mg20xu mixer. We have one party every month and we use a laptop to play music and as the night goes on the music move to EDM... One important thing is that the subwoofer needs to be 240v compatible (or 240v only). I noticed that the EV active subs seem to be dual voltage compatible as I could see on the label at the back (Internet images). I am waiting for a confirmation from EV. What do you think about the EV EKX-15SP? Would it be overkill for the QSC (which are not the K2.2 2000w) and the size of the room / amount of people? What about the ELX200-12SP? The QSCs are loud enough for what we need. Any other recommendation?

On a side note, this setup will be permanent (for a while anyway) and I would like to keep the QSC powered on (I need to check if they go on sleep mode if no signal after a while). When I turn on the Yamaha mixer it created a big "boom" from the speakers which can't be good. Do you have a trick to avoid that?

Many thanks for your help.
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Re: Subwoofer to compliment 2x QSC K8 1000w

Postby AlecSp » Fri Nov 22, 2019 3:09 pm

Math335 wrote:On a side note, this setup will be permanent (for a while anyway) and I would like to keep the QSC powered on (I need to check if they go on sleep mode if no signal after a while). When I turn on the Yamaha mixer it created a big "boom" from the speakers which can't be good. Do you have a trick to avoid that?
Most kit (like mixers) tends to give a startup transient. The trick to avoid that (at no cost) is to turn on the source first and the amplifier/speakers last. Not sure why you want to leave the speakers powered on but, if you do, you will always have this - and the ultimate possibility of damage to the speakers.

You could get a power sequencer that will turn everything on and off in the right sequence with just a single switch. But these cost money ~ UKP 500 and need to be configured correctly.

What sub for your K8s? (which are rated at 127dB peak). A good place to start would be in the same family with the KSub, which should integrate well. The only question is that you use the system for EDM, where you might want a sub with more poke, and more bottom end extension. I haven't used the K8, so I won't give any recommendations beyond considering one or more KSubs if you can audition them with your tops. But, if the KSub lacks the grunt you might want, then there's a big market out there.

The EV EKX-15SP is rated at 133dB peak, which on paper looks like it's way more than the tops need, but nothing wrong with headroom, and you might appreciate the grunt for EDM. When using the K series with a sub, remember to set the LF switch on the top to "Ext sub", which adds a 100Hz high pass filter. And you'll need to find the right low pass frequency for the sub, which for the EKX-15SP has options for 80, 100, 120, 150 Hz. I'd suggest 100 would be a good starting point to try. But that's where there's a bit more to play with when mixing and matching subs and tops.
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Re: Subwoofer to compliment 2x QSC K8 1000w

Postby Sam Spoons » Fri Nov 22, 2019 6:01 pm

Faild to post a couple of hours ago so Alex has answered but since I've typed it here's what I said :-

I have an old EV 15" sub and it is excellent but no useful experience of newer EV 15" subs (I did have a EV12" sub briefly but did not think it was very good). But, you can always turn it down to match the levels of the K8s. The issue you might have is with crossover frequency. The best match would be a QSC K-Sub if funds allow.

Always power on the mixer before the speakers and power off the speakers before powering off the mixer. Leaving them on is not a great idea.
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Re: Subwoofer to compliment 2x QSC K8 1000w

Postby Math335 » Mon Nov 25, 2019 6:56 am

Thank you for your replies, they are helpful.

The reason why I wanted to keep them powered on is because the system will be used by others and the speakers are not easily accessible (to turn them on and off). I think I will connect the speakers along with the sub on a dedicated electrical circuit with a switch (in the DJ booth). I don't see any problem leaving them on but cutting the power with a switch.

As for the connections I have a few choices. The QSCs have one full range line level output for each of the two input. It also has one mixed output. I will test both options but I believe that one type of output is controlled by the gain knob of the speaker.
The other option which might be the best one is to connect the sub to one AUX (TRS) of the mixer (Yamaha MG20xu). It will give the ability to control the volume of the sub with the AUX knob.
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Re: Subwoofer to compliment 2x QSC K8 1000w

Postby Sam Spoons » Mon Nov 25, 2019 1:00 pm

Yes, you'll have no issues using a master switch to power the speakers on and off, power the mixer separately so you can switch it on an off in the correct sequence with the speakers.

WRT the sub you can feed it from an aux but I would usually run both L&R to the sub and use the links to drive the K8s. Make sure you have the eq switch on 'ext sub' to engage the 100Hz HPF and, whichever sub you buy make sure it has a matching 100Hz 24 dB/8ve LPF (The K Sub has this built in and permanently active).
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Re: Subwoofer to compliment 2x QSC K8 1000w

Postby Wonks » Mon Nov 25, 2019 1:13 pm

And neither the filtered or straight output levels will be affected by the volume level of the QSCs.
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Re: Subwoofer to compliment 2x QSC K8 1000w

Postby Sam Spoons » Mon Nov 25, 2019 3:05 pm

I don't think either the K8 or K-Sub have filtered outputs?
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Re: Subwoofer to compliment 2x QSC K8 1000w

Postby Wonks » Mon Nov 25, 2019 3:13 pm

Sam Spoons wrote:I don't think either the K8 or K-Sub have filtered outputs?
You're right. I misread a bit in one of the OP's posts.
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Re: Subwoofer to compliment 2x QSC K8 1000w

Postby Sam Spoons » Mon Nov 25, 2019 5:59 pm

:thumbup:
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Re: Subwoofer to compliment 2x QSC K8 1000w

Postby Math335 » Tue Nov 26, 2019 2:12 pm

Thanks again for the info.

I finally bought the KS112. It was more expensive but they had it in stock and I need it asap. Same brand as the tops so I know it will blend right in. Even though it's a 12" know it will be enough (even too much).
Can't wait to try it.
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Re: Subwoofer to compliment 2x QSC K8 1000w

Postby Sam Spoons » Tue Nov 26, 2019 6:11 pm

:thumbup: I'm sure that will be a great match for the K8s.
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