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Thread: Subwoofer to compliment 2x QSC K8 1000w

  1. #1
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    Subwoofer to compliment 2x QSC K8 1000w

    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.

  2. #2
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    What you are proposing will work reasonably well but the system would be missing 1 important feature... a high pass crossover for the K8's. I like these EV speakers, I own a pair of EKX12p's and 18sp's so I'm confident the 15sp would perform well for you, but the K8's don't have a high pass filter built in like all of these EV speakers or most other powered speakers these days so they won't get a break from all that bass when a sub is added and that is one of the main reasons for doing it.

    As for your other problem, there are 2 solutions. Either get in the habit of turning the speakers off first and on last or get a power sequencer that will do the same automatically... or leave the mixer on all the time too. IMO it's better to turn everything off when not in use.
    Paul O'Brien
    Old Tech Guy
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  3. #3
    The K8 does have a high pass filter (crossover) built into it, (the original K8 has just "ext sub" switch which I think is a 100Hz high pass, the K8.2 I have not tried yet but think it gives you a choice of frequencies)also "standby mode" where it will go to low power mode (basically off) after a few minutes of no signal. So you're all good there and could in theory match them up with any modern powered sub.

    Like Conanski I am a fan of EV's powered stuff, especially the subs. I do think you'd be fine mixing brands there. But QSC is also really good stuff, and in theory you'll get a smoother crossover if you match brands.. only IF the manufacturer paid attention to the phase response when they were designing the system...

  4. #4
    As far as turning stuff off automatically (other than the standby mode that is hopefully in whatever sub and tops), I actually have this setup for my home system.. I use a thing by Parasound called the SCAMP.. that you connect to an output on your mixer. When you start sending signal, it powers up some outlets on the back.. and that powers your speakers/sub (or in my case, it powered up my amp rack). When the music stops for a couple of minutes, it turns everything off.

    Well, Parasound discontinued the SCAMP, and why, I don't know.. because I thought it would be easy to find something else similar. But guess what, it isn't. I could have cobbled something together using two or three pieces of gear.. great for a whole house setup or a corporate install, but total overkill for my setup... so I ended up buying a SCAMP used on ebay.. and they are actually really hard to get and not so cheap, because people want them. But if there's a new product out there that does the same thing I'd sure love to hear about it for next time.

    Long story short.. see if you can get a sub with an automatic standby mode so you don't have to worry about this problem.

  5. #5
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    Quote Originally Posted by light-o-matic View Post
    The K8 does have a high pass filter (crossover) built into it, (the original K8 has just "ext sub" switch which I think is a 100Hz high pass,
    Oh I missed that.. good catch, the EKX subs have a crossover option to match that and in my experience they work just fine with other brand speakers.
    Paul O'Brien
    Old Tech Guy
    www.Techott.com

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    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.

  7. #7
    In your setup you would not use the line (mix) output of the K8 because you have a mixer and are controlling the master gain there. It would work, but will be less complicated to get everything dialed in if you use the pass through outputs. But normally the way this is done is, you run two cables from the master outputs (left and right) on your mixer, to left and right inputs on your powered sub, and then two more cables from the passthrough outputs that your sub will have.. the left cable to one input on the left K8, right cable to one input on the right K8.

    Then you just set things up as so:

    First bring all speaker and sub volumes to zero and set any EQ's to flat (12 oclock position)

    Set the K8s to EXT SUB switch position, and make sure sub is set for 100Hz high pass if it has a choice for that.

    Play some music and bring the mixer up until the meters on the mixer are hitting around 0db or a bit above.

    Bring your K8 level knobs up until it is as loud as the loudest you think you will be playing it.. or until the limit lights on the speaker start blinking significantly.. whichever comes first. And you want to make sure it sounds balanced left to right when you are between the speakers.

    Now bring the level knob on the sub up until the amount of bass nicely balances the highs. Try a few different types of music until you've struck a good balance.

    Once you have got that all set nicely, you should not have to touch any setting on the speakers or sub again (or, very often), if you need to tweak the amount of bass or highs sometimes, use the EQ's on the mixer.

    That's the easy way, that is least likely to go wrong if people who are not as familiar with the setup want to use it...

    Now, the other way you mentioned, running the sub from the AUX send (post fader) on the mixer. That is actually very common on live sound setups, if you are mixing bands.. normally you would not want anything but the kick, bass, maybe keyboards.. certain guitars depending.. being fed to the sub. You wouldn't want for example a snare mic or vocal mic to feed the sub because any bass in that signal is just going to muddy things up. So yea, IF YOU ARE MIXING LIVE MUSIC.. then that is a legit way to do it. But keep in mind that this also puts a lot more responsibility in the hands of the person running the system to know the correct settings. Else you come in one day and the subwoofer is cranked twice as high as it should be, or worse, someone didn't know to bring it up so they just cranked the bass EQ trying to get bass out of the tops, and blew them. It's just a more mistake-prone setup for untrained people to use. But if you are mixing bands and have at least somewhat trained responsible people using the system, then go for it.
    Last edited by light-o-matic; 11-25-2019 at 12:11 PM.

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