Cleaning up bass in FOH

You cross before the sub ? Why? The lpf in the sub matches the hpf in the K12... An external x-over is probably not going to help and fact may hinder...

Run the sub flat, not in deep mode.
Be sure that the sub itself is not up too high.
Be sure that you are listening out far enough that you can hear both the 12 and the 18. The 18 by itself sounds muddying you put your head down in front of it It is but one component of a system.

One of our systems is K12's on KW-181's. I run that system last night in an auditorium setting. Multiple performer setting. I had an acoustic Hawaiian jazz thing with Upright Bass, mic'ed with an omni condenser. That worked nicely. A 15 member chorus with electric piano. A few Kareoke things with really strong performers - weird but variety show gig... You just never know... Then grand piano...

When I was sound checking, the sub, by itself sounded like @ss... The whole system up and balanced sounded great... I did dial the sub back a bit so if the volumes on the 12's were at noon, the volume on the single sub was say 10:20 to 11:00. No RTA other than my ears as there was not time to play with SMAART and shoot the room...

The 181 is a pretty strong woof. One of QSC's recommended configs is a single 181 on the ground with 2 KLa line array boxes as tops... The KLA's will bury the K12's if the listener is in the dispersion pattern...so basically, watch the balance...

Last night I ran everything full range and put steep hpf's on eveything. I often, more often in fact - run aux fed subs. I get a lot of acoustic instruments in loud settings and the aux fed subs thing really helps.

 

Never fine aux subs myself but that's why the lowpass before it? The overlapping feeds will be what's muddying things.

 

I drone on but... Get a wireless and go out front and listen. Auditioning the components on a system in isolation is a skill that should be developed. If you want to do the sound company thing. For the most folks it is enough to be able to go, yep, sounds like us...

 

In my system, aux fed subs provides a brick wall as opposed to the curve associated with an HPF. Crazy sound company dates, it makes total sense - at my end of the game. The big guys, have good reasons, better tools and more time to do it differently...

 

Is anybody else adding bass you don't need that could be muddying up your sound?

 

What does that mean?

 

Hpf is in db per octave so it is a slope so setting a 6db per octave hpf at 120 means that 60 is only 6 db down. The BSS crossovers in my 'large' rig allow for a custom filter in an absolute mode. Set it at 120 an nothing below 120 is in the output or above on the case of the lpf. They also allow me to route the signal from one input into the other side so my aux drives sine B and main drives side A. A drives the tops and B, the bottoms. Bass, kick, keys, maybe a bit of guitar, anything else that need's low end support goes out the aux but is in the full range mix as well.

This also means you have to deal with both the master Vol and the Aux vol when changing the vol of the entire system which is a pita while you are getting used to it. In the case of my SL 16.4.2, the Aux is on a knob and the Master is on a slider, double pita... Second nature now but for a while it was confusing...

 

This post is much different if we're talking about bass the fish.

 

I'm pretty sure that any filter you can find or design will have some sort of rolloff slope. Active filters can rolloff steeper than passive ones but I am fairly certain that there is no real world filter that can pass 0dB at 120Hz and minus infinity at 121Hz.

 

Quite the opposite. When done properly the subs and mains have appropriate high and low pass filtering, so their is no overlap. Running subs off a post fader aux allows you to send only the instruments to the subs that are appropriate such as bass guitar, kick drum, and perhaps keyboard. There is typically no reason to send vocal, sax, trumpet, overhead, etc, to the subs as it just mucks up the sound with garbage below the fundamentals of these sound sources. By keeping all unnecessary open mics out of the sub mix it tends to tighten the bass significantly.

As a caveat, the bass, kick, and keyboard levels must be appropriately balanced between the main mix and the sub. IMHO, the reason running the subs off an aux often fails is because people run the sub levels too high.

Another trick for tightening up the bass is to run high pass filters on pretty much every channel and adjust the frequency to the sound source. For example I typically high-pass male vocals at 180 hz or higher and female vocals at 250 hz or higher.

 

I am quite sure this could be easily done in the digital domain. I am less certain that it would have any practical benefit.

 

You are probably correct but my BSS MiniDrives get really freaking close and without sounding 'peaky'. It is an incredibly steep curve and effectively, it is a vertical line ... New those crossovers each cost about what I just paid for a KW-181... They are no longer in production. I wish Harmon would add similar functionality in the drive rack line ... I paid $600 for the last used one I bought. Of course the management software is XP based AND comms is via a 9 pin null modem cable - welcome to the 90's... Fantastic pieces in spite of that ...

 

From the manual:

• Active crossover filters with up to 52dB/Octave slopes to divide the audio spectrum into separate passbands for each transducer.
  

 

What would be hip for Presonus, Mackie, Soundcraft, Behringer to do would be add a variable slope to their HPF's... That really should be easy to accomplish in the digital domain. It would obsolete my architecture but let me sleep easier knowing that I could implement around more standard / current / less expensive crossovers... I have redundancy built in but those MiniDrives represent potential failure points in my system...

52 db per octave is you'll admit, pretty freaking steep...

 

uhhhh...the OP had a question in there somewhere...???

 

I meant the huge overlap where subs and mains are playing same thing at 90hz.

 

The QSCs have built in DSP and are designed to work together as system without an external crossover. Selecting the appropriate user options crosses the system over at 100 HZ per the KW181 and K12 manuals. The subs are low passed at 100 Hz at all times, and the K12s are high passed at 100 Hz when the Ext SUB switch is engaged. Keep in mind the signal coming from the post fade aux and main outputs would be identical in all regards except level which is adjusted to properly balance the sub and main level in order to maintain a flat response and proper phase relationships at the crossover point. Improper equalization and running the subs too loud are likely sources of the OPs problems. If the OP is running an external crossover inline with the subs, this could cause some phase issues that would be perceived as an uneven response or a loss of bass around the 100 Hz crossover region.

 

Think we had covered by post #5...