Rational Acoustics



Dr. J
June 2nd, 2010, 10:45 AM
Hello FFT users -- Maybe you can help me out. I have been using Smaart 6 for about a year now and I have always set my system up with the ground plane method. I am pretty happy with the way it sounds. I am always asked why I don't run Smaart at the venue while there isn't anyone there.

Everything I have read and have been taught (so far) suggests that changing my system from a flat response (heavy in the low end though) to supposedly conform to the room is a bad idea BUT yet everyone I know wants to run a dang RTA at the club. I know Smaart is waay different than an RTA.

So my question is this: Would you bother with measuring in a venue (If your system is already smooth in it's response - outdoors) when the venue is acoustically terrible (as most bars are) and also knowing that if you measure the place empty that is it going to fill up with people when the show starts?

Please set me straight. Thank you!

Harry Brill Jr.
June 2nd, 2010, 06:15 PM
Yes. Making the assumption your system configuration does NOT change in regards to component arrangement, there are still some room related issues you may want to address with EQ. Most of these issues will be in the low frequency and you could probably do much of it by ear. Be careful not to make the system too flat at the mix position as it will be harsh up front. Smaart is also very useful when ringing out feedback.

Dr. J
June 4th, 2010, 10:55 AM
Thanks Harry. Yes -- my trace changed in the low end. It actually ramped up stronger by quite a bit. Are you saying that I should minimize this by bringing the trace back down to match what I achieved outdoors?

Harry Brill Jr.
June 4th, 2010, 12:00 PM
This would be a good use of EQ. Just don't overdo it. Smaart can be very handy when it comes to finding the right filter but your ears will often determine how much to cut. Smaart doesn't know equal loudness contours, although it would be really cool if it did ;).

Dr. J
June 16th, 2010, 10:50 AM
Thanks Harry. I have another question if you don't mind. I align my system outdoors -- horns, mids & subs & I know how much delay it takes. When I go into a venue, is it necessary for me to re-align my subs to the tops and if so -- where would be a good spot to place the measurement mic?

I have done this in the past with one side (one stack) and with the mic in the middle half of the right stack listening area. In other words -- from the center line (mix position) the middle of the right stack & mix position. I hope that makes sense. In the half of a half area....:D My mic was in the on-axis position. I have seen several posts where the mic was pointing straight down on a case lid or a table. Any clarification on this would be great. Thanks!

Harry Brill Jr.
June 17th, 2010, 02:20 AM
You should not have to re-time your system indoors. There is no reason it would change within the box. When we have more than one stack per side this becomes more complicated. Still anything within a single box should not need to be re-timed.

Placing the mic on the floor is a way to reduce reflections from the floor from getting into the mic. These reflections cause comb filters in the measurement. When the people come in, the reflections are no longer an issue so we would not want to correct our system based on that response. Ever spend a lot of time EQing a system in an empty room, only to find yourself flattening the EQ when the crowds are there?

Dr. J
June 18th, 2010, 12:55 PM
Thanks Harry! I have not done much measuring inside other than to see what the room has done to my system compared to the free field. It doesn't change much except the low end so I may adjust that. I haven't tried to re-do my live trave to be flat inside since I am told it would only make matters worse.

Thanks Again!

Kip Conner
July 15th, 2010, 02:34 PM
J- Assuming that you capture your traces and keep it's a good way to determine quickly what the room acoustics are doing to your system. I like to keep my free field measurement traces as references when moving the rig indoors. Although it's true you can't "tune a room" with an EQ, you can overcome some issues by not exciting frequencies by adding to the problem.

Case and point: your floor wedges. You can align and eq the perfect wedge and as soon as you put into a wierd stage space you have to do it all over again. Example- a tent or gazebo. That space has a sound that a good flat response box usually doesn't play well with and a quick retune can fix it.

Harry Brill Jr.
July 15th, 2010, 02:45 PM
Kip, I have to respectfully disagree with you at least from the fundamentals stand point. The correct solution to the examples you give are to fix the acoustic issues with treatment. As you said, you can't EQ a room. If you are having stability problems then your first solution may be the only practical way to go, remove the frequencies that have too much gain at the mic (reduce feedback). Keep in mind the flat wedge isn't necessarily the problem, but rather the off axis response of the mic that is feeding back, and at times reflections from that tent ceiling that are bouncing back into the mic. In the case of EQing to correct bad acoustics, it's just important to KNOW what you are doing is kind of like leaving the knife in so you don't bleed out all at once. Removing energy from the signal that is supposed to be there is an unfortunate compromise.
In combat audio we do what we have to do to get through the day, but if we all push just a little to correct these venue related issues, change will come eventually. The best compromise is one that involves only the artist, IEMs. This compromise helps in so many ways to give the audience a better sounding show. The artist that won't work with them isn't thinking of the audience first, or doesn't fully understand the compromise they are making, or it could just be budget oriented, but I have a larger investment in gear than most working musicians so I'm not buying the budget argument.

Kip Conner
July 15th, 2010, 02:58 PM
I wasn't referring to stability (feedback) issues, I was thinking more along the lines of "wow, what happened? this monitor sounds terrible in the enviroment." I typically don't have feedback issues it's more of what happens when I excite the performance space with a source and than have to listen to it work it's way back in to the vocal mic so my whole audience gets to hear it.

The situations that I had in mind were these town square gazebos and tents that our agent loves to book us in. To help speed up the process I broke down and purchased 12am's and it's a challenge when you the monitor is pushing 110dB.

Harry Brill Jr.
July 15th, 2010, 11:00 PM
I wasn't referring to stability (feedback) issues, I was thinking more along the lines of "wow, what happened? this monitor sounds terrible in the enviroment." I typically don't have feedback issues it's more of what happens when I excite the performance space with a source and than have to listen to it work it's way back in to the vocal mic so my whole audience gets to hear it.

The situations that I had in mind were these town square gazebos and tents that our agent loves to book us in. To help speed up the process I broke down and purchased 12am's and it's a challenge when you the monitor is pushing 110dB.

I advocate correcting the system at the system EQ and the source at the channel strip. Do you think the monitor spill into the mic as well as off the edge of stage is something you are fighting at FOH? Do you EQ the main PA or the source to account for this spillage? I think this does NOT fall under the system techs responsibility, but rather the FOH engineer. Since you are both, I think you may be wearing both hats at the same time which comes from having the same experience over and over. Ultimately the right place to solve the problem is in the acoustic realm (correct the signal before it gets into the mic). Treatment to the tent ceiling? Turning down the wedges? IEMs? If you can't do that and instead start EQing to make it bearable, the question of where to attack the problem comes up. Do you find you use channel EQ as well as system EQ or do you favor one over the other? What about board tapes? Do they sound like the live performance? Do you find the frequencies you've cut as lacking in the recordings? If not, I'd say you are already doing the right thing. If so, you may consider moving the corrective EQ to the channel strip rather than the system. If the spill going into the mic (I call it feedback even if it's not ringing) is coming from the wedge and it's the same signal that is coming directly from the artist (the voice, the guitar, etc), perhaps it's combining constructively both acoustically and in the mixer and should be EQ'd at the channel strip. This would help the wedge and the main at the same time. It would also help the recording. Make sense or am I off my rocker?

Dr. J
July 16th, 2010, 11:47 AM
Makes sense Harry. Thanks for your help.