No headroom for our PA

axeman80

Hi all,

I've spent the better part of the week looking through posts here (and may very well be more confused than when I started)...

Anyway, set up our new Driverack PA last night for band practice. We're running 2 Carvin 1540 passive 15" speakers for mids/highs (Carvin DCM 3000 amp) and 2 Harbinger 18" passive subs (QSC GX7 amp) through a 16 channel Carvin C1600 mixer. Did all of the wizards (didn't get to EQ the speakers outside however no rmess with the PEQ). After the feedback wizard ran, we were stuck with our main faders on around -24 (right near the bottom). The room volume was fine and, quite honestly, sounded fantastic. However, we have a gig next week were we have to use our PA. We will not have any time to mess with settings. When we tried to raise the faders even slightly, the room last night would errupt in feedback. I was hoping to use last night's preset as the baseline for our gig, but am worried we won't have enough headroom to push the bar with 100+ people in it.

Am I safe to assume the larger space for the gig will not have a problem with louder volumes even using this present?

Also, I noticed that the DRPA set the low crossovers around 200Hz which seems high to me (I had heard 100-120Hz was normal). Should I manually change these, or trust the settings?

Thanks in advance!
Jeff/Axe

Dra

PA or PA+?
Where are the gains set on the x-overs that the wizard set for you?
Where are the used channel input gains set on each channel?
Where are the used faders set?

axeman80

PA+ (sorry)

I figured there was more info that was needed. I'll check those settings at Sunday's practice and post them.

Thanks

Gadget

Subs
HPF 45hzBW18
LPF 118hz LR24
Tops
HPF 118hz LR24
you have barely enough power so be careful

The ONLY way to get that feedback under control is flatten the system...If you have the mic do an auto EQ pass EVEN IF IT"S INDOORS..
If not... well.. set up the mic you have with the flattest response and aim it at the system...engage the RTA and turn up the system set up the way it is for practice and watch the RTA display...push up the main fader till the system starts to feed back... note the peak frequency that is feeding back and either use the GEQ or a PEQ and cut those frequencies to match the feedback displayed...rinse and repeat..

Note in all your reading did you read:

viewtopic.php?f=61&t=959

Or check out any of this:

viewforum.php?f=60

If you have the mic read up on the AUto EQ process in the Start here thread, and the FAQ's..

Gadget

axeman80

Used the mic and did the auto eq. Watched to make sure there were no nulls where the system tried to crank a specific frequency. The desired flatline we requested looked about right to me anyway (small adjustments, most adjacent frequencies had similar small cuts or boosts).

When doing the auto feedback set up, we could only get the main faders up a notch or two before the feedback started in (well below where we have had them in the past, however the PA+ had us setting the amps higher than our usual also). I know there are a few channels that had gain up around 12 o'clock, but the individual channel faders were all the way down, so would that make a difference?

I read the initial set up, still trying to grasp the gain structure information.

Read most of the other section you suggest, but certainly haven't learned it all...

Thank you

Gadget

So where exactly did you place the mic for the auto eq pass? (on a stand or on the floor on a towel or carpet) how far out... what pre curve (hopefully flat -0-)

Were both sets of speakers on?

If you use the amp sensitivity settings on the DRPA + you would HAVE to use the auto level feature as well, OR manually set them as per the "start here" thread which was written PRE DRPA+ ...

In that event...you would usually either crank the sub amp.. or set the sensitivity as per the driverack, and then use the amp sensitivity control on the tops amp to balance the sound between the subs and the tops...

All of the above can affect the way the speakers sound, and how much you can push the system before feedback...

Gadget

P.S. I went in a modified the "start here" thread to more accurately include the PA+ in the thread...

Dra

axeman80 wrote:

When doing the auto feedback set up, we could only get the main faders up a notch or two before the feedback started in (well below where we have had them in the past, however the PA+ had us setting the amps higher than our usual also). I know there are a few channels that had gain up around 12 o'clock, but the individual channel faders were all the way down, so would that make a difference?

I would suggest that you get the "system" gain structure under control (with the main output meters bumping RED and the amps not , but just below, clipping. Then, with the main faders at -0-, channel faders at -~- (all the way down), Cnannel gains all the way down, and PFL your vocal mics so you can check their output on the meters. One at a time "check" them with max input while increasing their input gains. Watch the channel clip and the output meter. Stay below the clip point and max input. Do this for all vocal mics, with their own max input source.

Now engage the AFS on the PA+. You will have to play with different scenarios to find what best floats your boat. How many fixed filters, and at what width (Q), etc.
In case you did not know, you can mix the filter widths. This is useful because the first frequencies that feed back are typically in need of a wider (speech) than those that really have to be hot to ring (music high). The speech width in way more narrow than a band on a 31-band EQ, so don't fret too much if you end up having to use them instead of the music width filters. Anyway you can start in Speech and catch a couple of frequencies, change the setting to Music - low and catch a few, change to Music - med, for a few, etc. I will use Speech for the live filters, as they are the fastest to respond.

I am not sure of the science involved, but I have discovered that "feed back catchers" of all kinds work faster in general with the amps turn down so that the signal in the "catch device" is very hot, as opposed to the amps. (I suppose that you could reduce the gains in the x-over section as well to get the same result, just reduce by the same levels in case there are problems around the x-over point.) That way the oscillations that ARE the feedback will be most detectable to the devise and be grabbed much more quickly. The volume level would have been the same with the amps up, but the duration of the feedback before caught will be shorter and therefore less likely to do damage to the speakers and your ears. When done, turn the amps (or x-over gains) back to the normal settings (after reducing the boards levels). I don't do this a lot, but it is a tool if the process seems to be a "pain" in a giving set-up.

DRA

axeman80

Mic was placed near the floor about 15' feet out from speakers in between both (which are 15-20' apart). Pre curve was set flat. Both sets of speakers were on. We did use the auto level feature.

I will look over the "start here" thread again.

I'll work through the gain structure tomorrow at practice.

Thank you both!

Gadget

Mic was placed near the floor about 15' feet out from speakers in between both (which are 15-20' apart). Pre curve was set flat. Both sets of speakers were on. We did use the auto level feature.

BAD BAD JUJU :roll:

You didn't read the whole thread did you.... What you did was to open up a can of worms... allowing multiple paths to the mic...

Try again... one stack only...mic ON THE FLOOR on a towel or carpet, laid down and pointed at the speakers ...strait out... 20-25 feet is best or at least make sure the horn is in the primary coverage area (the mic needs to SEE the horn directly. this may require you to put the top down on the sub or even next to it... see the indoor micing method in the the FAQ section...

Try the methods in this thread:
viewtopic.php?f=60&t=953

But try the bottom picture and lay the mic on a towel on the floor... don't worry about the sub...and let the speaker do what it can ...set the HPF @ 50hz BW 24

Set up a new preset and just do it stereo tops and subs (linked not dual mono) and then just do one top and don't worry about the subs.. simply add the sub HPF/LPF later, and then EQ the subs by ear.. and I have some suggestions there too if you wish..


G

axeman80

That's what the Evelyn Woods speed reading course will get you...

Practice last night had some interesting sounds in the air to say the least. Cranked the power amps, turned all gains and faders to zero. Rung tha gains out on all 5 vocal mics, then did the same for drums (electronic drums/2 channels), bass, keyboards, and 2 guitar channels. Turned on the AFS and started with 6 fixed and 6 live filters, used "speech" as recommended. Slid faders up, got them slightly higher than last practice before feedback took over. One tom in particular seemed to send the whole system into a frenzy. Did my best with the PEQ to cut that frequency, and had a fairly feedback free practice and a decent sound volume from song 3 on until the final song of the night which has both male and female lead vocals. That combination couldn't be tamed in quick trips to the rack.

I will take the main speaker down off it's pole mount at Thursday's practice and re-do the speaker set up with the mic on the floor 15' in front of the main (about as far as we can go in our practice space). Then set up the new preset as described.

Until then, I just have to learn 2 Van Halen solos, figure out a 3 hour set list for the group, confirm gig-night items with the bar, and teach my wife 8-9 songs on bass... :?

Thanks again!

Dra

Something doesn't add up. Electronic drums feeding back? Do you have something looped back into itself? Not sure I follow which faders are at what level.

DRA

axeman80

My guess was it had to do with that sound/frequency coming through the drummer's monitor and getting picked up by any combination of the 7 mics we use. We do have a lot of gear in a fairly small space which I realize causes problems. I figure if we can make it work in our drummer's basement, a small/medium sized club should be easier (for feedback at least).

Gadget

Um...Hey... the Indoor method with the mic on the floor and the speaker laid sideways (LOOK at the picture...) is NO WHERE near 15 feet... more like 4-8 feet...

Ok were starting to get old school, and new reality mixed up here...(remember we have been offering this information since the driverack came out....OVER A DECADE ago...)


Look, the speaker on a stick, or speaker on a sub needs a fair distance to develop and then only if the mic is on a towel and ...UP TO 25 feet out from one speaker/side at a time(top OR tops and sub..1x2-2X4** ...then use that as a baseline (and as always use your EARS as the final judge) BUT... the speaker on the floor.. on it's side is a MUCH closer proximity thing, it should be 4-8feet max...and it DOES NOT work for monitors PERIOD! ***

** I use mostly 2x5/2X6 systems where I power the horn in my system separately... I also have specific mid and sub xover and tunings to fit the speakers...you add a LOT of power by eliminating the passive xover...the trick is to balance the system hi's, mids, and subs...and make sure that the different speaker elements are in phase and reproducing their frequencies accurately. This is a TOUGH thing to do... Factory specs need to be looked at VERY carefully...if there aren't any you might as well move on...

*** monitors seem to need to have a "mic on the stand" in the singers "head" position, aimed at the speaker... see the " 121.7 dB monitor" FAQ...ALSO OF NOTE... ANYTHING that reflects the sound BACK to the mic needs to be looked at INCLUDING a hat brim... especially a COWBOY hat!!!

Too much to cover tonight..

be well
G

axeman80

Certainly hadn't thought of cowboy hats!

Thanks again Gadget - a lot to take in for a "sound guy by default"

Dra

Another killer is eye glasses.
Big poodle perms and thick shaggy beards helps a lot.
DRA

Dennis

Dra wrote:

Another killer is eye glasses.

And eye glasses in addition to a hat is lethal

axeman80

My wife (bassist) has the big hair, but we don't let her sing. No eye glasses to speak of in the group, so I may have just caught my first break!

axeman80

Quick update:

We played our first Driverack fueled gig on Friday and, overall, it was very successful. We had a feedback problem with 2 of our mics (and the drummer's monitor I believe) which flared up a few times during the evening, but eveyone said we sounded great a put on a really entertaining show. We were supposed to stop at 1:00am, but got asked to do several encores (including one from the owner of the bar) and ended at around 1:25am.

Now we have the entire PA sitting in piles in our drummer's basement, I plan on starting over with EQing the main speakers and doing the gain structure of the entire system over again along with the AFS/filter set up.

Gadget

Are you SURE that the monitors didn't cause the feedback... and NOT the mains?

You do realize you can do a mono tops and subs AND one monitor mix with the DRPA+ AND auto EQ them separately?

viewtopic.php?f=60&t=2228

Only one monitor mix ..but...

whats with the drummers monitor? Monitor info please...

G

axeman80

Honestly, not sure of anything - we were just doing our best to squash the problem quickly when it occurred (never during a song, only between songs actually).

Our drummer normally uses IEMs, but for some reason they were not working properly when we did a quick sound check. We have a back-up set of main speakers and stacked them up next to him and ran a speaker cable (in series) from the closest monitor to the top Yamaha speaker so he could hear. I believe it's a Yamaha BR15. I made sure the Yamaha was pointed away from the vocal mics, but we didn't have any problems until that speaker was plugged in.

jemthebullfrog

Hi there

I've just read this thread with interest and think that I may have tripped across a possible mine field. However, if I may be so bold as to off my thoughts on your issue of feedback. The number one cause of feed back in small systems is having the microphones in too close proximity to the loudspeakers. No matter how much you try to eq out that pesky frequency, if your microphone is 'hearing' too much of the loudspeakers, feedback. Feedback suppressors are great tools used to help tame a correctly setup system and should never be used as a remedy for a possibly incorrectly positioned loudspeaker.

Thanks for not getting offended

Jem The Bullfrog

Gadget

The number one cause of feed back in small systems is having the microphones in too close proximity to the loudspeakers. No matter how much you try to eq out that pesky frequency, if your microphone is 'hearing' too much of the loudspeakers, feedback.

I'm not going to "get offended" but I might take issue with your comments...I have, at a specific volumes...(121.7 dB) gotten my monitors to be stable with the mic aimed directly into the throat of the horn @ under 1 foot...

The thing about the Yamaha's is, they can be made to be fairly stable, but require a significant amount of processing..

By paralleling in another speaker you very well could have changed the way both sounded...you also very likely are using cardioid pattern mics and the off access rejection point is at the base of mic as if it were on a stand... not off to the side like you would a drum monitor...THAT would be much better served by a Super Cardioid or hyper cardioid pattern mic...

Gadget