[Rocky139]

I have powered Mackie CR5BT powered speakers and I'm wondering if there is some way to add a powered sub to them?

 

[theveterans]

Input your pre outs to sub then to monitor out. Set your preferred crossover high and low cutoff

 

[Rocky139]

Would I keep the speakers powered or not plug them in?

 

[theveterans]

Speakers are still powered. Mine goes like this

Preamp to sub then sub to speakers

 

[Rocky139]

These are the backs of my speakers/ subwoofer

How exactly would I connect them
I’m using my computer and a 3.5mm plug as inputs

 

[theveterans]

The McKie is an active speaker so you can't use a sub without having a preamp with 2 outs. I recommend Schiit Saga (which I use),but on a tight budget, this will do: https://www.amazon.com/Nobsound-Sel...qid=1520402287&sr=8-4&keywords=passive+preamp

To use that, connect your 3.5mm to RCA to one of the inputs. Then use both RCA (A and B) outs one for your McKie and another for your Polk sub. Make sure to use common ground to avoid ground loop hum when setting this up. Then listen to your favorite music and adjust sub volume as well as the phase switch (using the right phase should make the subwoofer's bass integrate well with the satellites (speakers) and the sub sounds "out of sync" when the sub is in out of phase. There is no "right" phase since the phase depends on the polarity and wiring of the satellites, but 0 phase is more common than 180 phase in my experience.

Also, check your McKie's frequency response within the Polk's low pass filter to ensure that you don't have dips in frequency response at the cutoff if your cross over frequency filter setting is optimum

 

[Rocky139]

Thank you very much!

 

[Rocky139]

Would the low pass do anything to the speakers or would I just leave it as is?

 

[theveterans]

^ Low pass means the frequency that the sub will cutoff its sound. The trick is to check the frequency response of your McKie at each of those frequencies and see where it starts rolling off. I would guess that 80 or 100 Hz would be ideal. If you don't have the right cutoff, there will be either a hump in bass (due to both satellite and sub reproducing frequencies) or a dip (the satellite has an early roll off and the sub hasn't make up for it yet since the cut off is too low)

 

[Rocky139]

Would those be the cut off’s if so would I put the sub at 60hz (look where is says CR5BT in parentheses)

 

[ProtegeManiac]

Would those be the cut off’s if so would I put the sub at 60hz (look where is says CR5BT in parentheses)

Crossover settings depend on more than the rated response of the sub and mains. You'll have to tweak the settings to match acoustic realities - sub placement relative to you and the main speakers will affect where you can set the low pass and the gain.

Ideally you have to set it as high as you can without the bass becoming overpowering and easily localizable, ie, the bass drum for example needs to still sound like it's coming from dead center and behind the vocals. The sub needs to "disappear" in the set-up, like it's barely there (unless you're playing really bass-y music) but when you switch it off the absence of the sub will be easily apparent.

 

[Rocky139]

Thank you very much!

 

[Rocky139]

Speakers are still powered. Mine goes like this

Preamp to sub then sub to speakers

Is there a reason you’re using a XLR to TRS cable?, Also the input on you sub goes to you’re Saga right and the output to the speakers?

 

[theveterans]

Is there a reason you’re using a XLR to TRS cable?, Also the input on you sub goes to you’re Saga right and the output to the speakers?

No particular reason for the TRS other than being slightly cheaper than the XLR to XLR version. Input from Saga then you can set the low cutoff and high cutoff anywhere from 80-120 Hz and the output goes to the speakers. The sub automatically converts the output to balanced.