Hello, I’m interested to purchase the qu sb mixer. I would like to know if there is rta function in the peq section of the input channels. I’m only aware of rta in geq in outputs. Thank you!
No, the RTA is mated to the GEQ in that the display references the 1/3 octave divisions of the GEQ.
For me, the ability to sweep a narrow PEQ filter, either boosted or cut, tells me what I want to know more quickly and accurately than RTA. I feel that making such decisions by ear is preferable than by eye.
Partly Losted; you can see which eq-band is peaking by a little red dot on that band. The full blown RTA follows the PFL which you can than watch in the home → meters sreen
Giga
Thank you for your answers!
Dick Rees, for sure ear comes at first, but RTA is a helpful tool in some circumstances.
Giga, you mean that if PFL is enabled i.e. only in ch.1, the RTA in meters screen should only show the ch.1 frequencies? And not all the other channels’?
During a gig, how can be found which input(s) creates the feedback and at which certain frequency band?
In my opinion this is the only flaw of this appealing mixer. And I think it can be changed with a software update.
“During a gig, how can be found which input(s) creates the feedback and at which certain frequency band?
In my opinion this is the only flaw of this appealing mixer. And I think it can be changed with a software update.”
The correct answer to this is that a properly set up and configured system should not feed back in the first place. However…
If you want a mixer which can give you an exact visual representation of an offending frequency, you need something which runs something like SMAART. Presonus has this, but you need to run the program on a laptop. If you want, you can do the same thing with a Qu or any other mixer by using a laptop with SMAART, Spectra-foo or the like.
If you can’t tell which input (mic) is feeding back then you have a LOT to learn. Feedback is a SYSTEM phenomenon. The quickest way to identify the most likely offender is to mute/unmute your mic channels one at a time and see which one sets off the feedback. The quickest way to identify the offending frequency is to sweep a very narrow PEQ filter set to -12 dB across the channel spectrum. When the filter reaches the guilty frequency, the feedback should disappear.
If ALL the mics feed back at the same point there is only one thing to do:
Turn down the entire system and proceed at a workable level within the room/system limitations.
Giga, you mean that if PFL is enabled i.e. only in ch.1, the RTA in meters screen should only show the ch.1 frequencies? And not all the other channels’?
That’s correct
Giga
Use your ears. If you can’t identify problems by listening then maybe you need to be doing something else. I see this all the time. I have to setup systems and then the people run faders and mutes. That’s it. They have no concept of frequencies. Drives me crazy.
George, you old codger…you probably remember Garnet Mimms (Cry, cry baby).
Here’s another relating to lessons hard won:
“The Truth Hurts”
Keep telling it like it is.
DR
That’s cool Dick. Sometimes I get in trouble for telling it like it is. I would more but have to restrain myself.
losted…
Never mind us old folks. We’re so used to being independent of certain aspects of technology that such things seem cumbersome and time-consuming compared to a trained, experienced operator. So here’s something for you to try utilizing both available technology and training directed towards honing the skill set implicit in audio engineering.
Since you’re considering an Sb you obviously have an iPad to run the control app…and I further presume you have a cell phone. Well, there are free apps you can get which can be found under the heading “pitch pipe”:
https://play.google.com/store/apps/details?id=com.i2app.free.pitchpipe
Or you can go to the music store and purchase an analog pitch pipe:
When feedback occurs it will have a specific pitch…unless something is DRASTICALLY wrong with your entire setup…this pitch being most easily found at the onset of the feedback loop before it gets totally out of control, so when you hear the sound, match it with your voice: sing the note.
Now whip out your phone, open the pitch pipe app and find the pitch you’re singing by tone matching with the app or with an old-fashioned analog unit. All you have to know once you’ve identified the pitch is the basic frequency of that pitch. Look up a frequency chart for a chromatic octave of tones, A to A’ for example.
A = 440/880/1760 etc doubling with each octave up.
A bit of practice and you can easily learn how to identify the ringing frequency and apply corrective measures more accurately than a mere RTA. It doesn’t take long to learn/memorize enough of the basic frequencies and not have to refer to the small chart you’ve taped to the back of your iPad. It’s quite easy to quickly calculate the higher frequencies since they’re just two or three doublings of your basic pitch frequency.
Middle C is 262, but I find it easier to remember and do the doubling by just using 250. So if the offending pitch should be C, I know it will be one of the higher multiples of 250: 500/1k/2k/4k
You know, it takes longer to explain how to do it than it does to do it. I would say with practice that within a few months you should be able to identify and correct pitch anomalies in under a minute, better and faster than guesswork aided by RTA…which at the typical level of development and resolution is severely inadequate.
So you see, our frustration in this area comes from the fact that even if integrated into an audio console, it is simply not a good tool to use…especially considering that a little time spent in training yourself will be much more accurate and useful and as I have learned can be applied without even having to be at the console or on the iPad. I hear the note, sing the note, compare it to the lowest note I’m comfortable singing (which happens to be a G one octave below middle C, approximate frequency 200), ascertain the pitch, do the doubling thing and BINGO…problem solved within 10 seconds.
It can be done. YOU can do it.
I’ll leave it to someone else to explain how to use PEQ sweep for feedback loop identification, yet another more precise and rapid method to address the problem.
Right now I have to go teach someone how to catch fish…
For those us who cant sing…
A friend of mine is a walking rta. He spend a good while (years ago) with a signal generator- just learning the ‘sound to frequency’ conversions.
Not only will he tell you what frequency feedback is at without batting an eyelid (single peak analysis) he will also identify broader issues by freq range rather than words like muddy…
Really useful to have that kind of ear around. I’m nowhere near that, but am sufficiently practiced to know what I’m aiming for. Interestingly I can ‘see’ frequencies on the eq screen (rta is cool, but I have a feel for the shape I want to apply to an instrument/PA (somewhat excludes very specific problem freq cuts)
Can I ask a stupid question about the fader flip please - When it shows eq-band’s peaking by a little red dot on that band do you normally just cut that frequency on the respective fader or is there more to it like going into the parametric eq and sweeping, cutting frequency’s?
That’s the loudest, it might not be the offensive peak though…
It depends is the normal answer here…
“Can I ask a stupid question about the fader flip please – When it shows eq-band’s peaking by a little red dot on that band do you normally just cut that frequency on the respective fader or is there more to it like going into the parametric eq and sweeping, cutting frequency’s?”
The question is…
How does it sound???
As Bob said, the red leds in fader flip just marks the currently loudest band. Pulling that band down will let another one flash. Not necessarily related to the problem frequency and/or channel resp. mix.
For me the GEQ is much too coarse to consider it for feedback handling, its like removing a splinter with an axe… 
Can someone explain why the GEQ is not best for killing feedback? I use it quite effectively for ringing out monitors as I can be a bit more surgical about it. The PEQ surely doesn’t give you quite as many points to cut where required (although it’s good for ID’ing offending frequencies). That said, I’ve created my own presets for wedges (flat environments and reflective environments) that works for pretty much 95% of the time as I find the same offending frequencies popping up.
Can someone explain why the GEQ is not best for killing feedback? I use it quite effectively for ringing out monitors as I can be a bit more surgical about it.
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You can’t “kill” feedback. You can either deal with the causal factors up front or apply some palliative adjustments to compensate for out-of-balance factors.
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“Surgical” implies precise, narrow cuts. One octave wide GEQ filters are pretty much the opposite of “surgical”. Although your typical GEQ is qouted as “1/3 octave” units, the 1/3 bit applies only to the center frequency of the one octave wide filters.
Causal factors involve quality/pattern of your wedges, placement, mic polar pattern and such, but the bottom line is always “loudest sound at the mic wins”. Poor quality monitors, poor placement and unrealistic expectations from the person at the monitor are commonly addressed by gutting the frequency spectrum with GEQ. Unfortunately, making the performers wedge/position safe from feedback sacrifices headroom and thus monitoring capability output-wise. An apt analogy here is that fixing monitor feedback/headroom at the end of the chain with GEQ instead of addressing quality, processing and placement is like the difference between applying a tourniquet instead of sewing up the wound.
The PEQ surely doesn’t give you quite as many points to cut where required (although it’s good for ID’ing offending frequencies).
Typical PEQ gives you four bands. Prevailing standards say that if you have to apply more than four filters you need to go back and figure out what’s wrong in the first place. If you’re thinking that GEQ is good because you use fewer filters, remember that the filters are very wide, fixed-width filters and applying them in place of a variable width/center PEQ filter essentially removes more desired frequencies than undesired frequencis. IOW, the baby has been tossed out with the bath water.
If you prefer wide filters, you can always widen the PEQ filters, but you cannot narrow a GEQ filter. Having the option should obviously be preferable. Again, if you find the need to use copious amounts of ANY type of EQ, you have more serious problems which need to be addressed up front, not at the output end.
That said, I’ve created my own presets for wedges (flat environments and reflective environments) that works for pretty much 95% of the time as I find the same offending frequencies popping up.
This is preferable. I use coaxial monitors as I find they have a smoother, tighter output pattern to start. The wedges themselves have DSP which I’ve spent time optimizing for my use. I have several presets saved for varying program requirements.
I also have several presets stored in my Qu. None of these involve GEQ, just the needed PEQ and occasionally a bit of delay.
To sum up this long reply, using GEQ instead of PEQ is often likened to using a chainsaw to trim your fingernails.
Really good explanation - thanks Dick.
Out of interest, your use of delays in monitors - is that a stylistic decision or something more scientific? The one time I tried this the vocalist hated so never did it again.
Roy
A tiny delay (few mSec) may help to eliminate higher pitched feedback, since it shifts the resonating spots to lower frequencies (which may be cut by simply low shelf/cut on monitors).
Roy…
I mentioned delay as a tool along with PEQ. WHERE you apply the delay was not specified, but I see it got your attention. Remember, feedback loops are a SYSTEM phenomenon, so you have many variables to juggle and we’re not talking about FX delay, rather input and/or output delay.
Feedback occurs at specific frequencies. Notch that frequency and you’ve gained (or ceased to diminish) headroom. But since each frequency has a specific wave length, if you change the distance between the mic and the speaker by, say, a quarter wavelength, the offending frequency will cease to set itself off into the self-reinforcing loop. Of course, some other frequency may then take off…
Delay (channel input delay, mix output delay, mains output delay) can effect a virtual change of distance. If you’re working in a small space or suffer from severe reflectivity, your mains and monitors are going to reinforce/cancel each other in a touchier relationship. As noted, delaying the monitors or monitor content can occasionally bother a vocalist…so try delaying your mains to change the time/virtual distance relationship with the monitors. My experience is that the tiny amount of delay applied for any virtual changes in the spatial relationship should be unnoticeable to a vocalist.
Of course, having mains and monitors with as much EFFECTIVE pattern control as you can afford is where to start, but simply being aware of the variables in positioning and nulls will certainly help without re-investing. But sometimes you just have to accept that certain situations with limited or poor se-up options means you simply will not have as much headroom as you would like. Couple this with musicians who expect YOU to find a technical solution so they can be mindlessly loud or operte at 11 on their amps because “I have to crank it to get MY SOUND, man” and…well, you know the rest.
I use a Qu-16. If I had groups I could get more PEQ/mix by routing a critical MIX via a group. That would give 8 PEQ filters. I’ve never needed more than 4, relying on proper set-up and realistic expectations for system headroom given the laws of physics and the level of cooperation from all concerned.
DR