I’m running a QU-24 mixer in a church environment. Recently, I’ve noticed a 1 second reverb from our church mics - been running this system for 7 years without issue. No changes have been made to either EQ settings or to the room acoustics, which is well-treated with acoustic panels. The FX sends are set to post fader. There are no time-delay electronics in this sound system. (Unnecessary for the length of the room.) Any suggestions as to possible causes for this reverb and remedies?
First, I would check the routing of the audio in each FX rack (via the FX racks “back panel”) and make sure the routing is as intended and hasn’t been switched to some random channel/buss.
Second, check the individual channel/buss delay settings on the console. It’s possible that someone has accidentally set a 1 second delay on a channel/buss that this is causing your “reverb” effect.
I’m hearing this just in the room - no reverb when pafl’ing with headphones. What’s odd is this hasn’t happened before - the auditorium is well treated with acoustic panels and the original room reverb without panels was about 3 seconds. I thought reducing the gain would minimize it, but to no affect. The reverb does decay and fade away over a 1 second duration, in my estimation.
Are you hearing what you could describe as natural reverb, or are you hearing a distinct “echo” or repeat of the audio?
If it is reverb and you have made 100% sure that the console and any FX units aren’t producing the reverb, then we have to assume it is the room’s natural reverb that you are hearing. Have you move locations where you are listening/mixing from recently?
If it is a single hard echo/repeat, then I’m confident that is a problem being introduced by the system somewhere. Is there a speaker DSP or processing unit after the console, but before the PA? If so, has this been reviewed to make sure everything is set up correctly and nothing has changed recently?
What elements comprise your PA system? Are there any “fill” speakers in the room for example? Is it possible that the “balance” between the different PA elements has changes, and therefore you might be hearing a speaker that is farther away because it has been turned up louder?
I would describe it as natural reverb. As I mentioned previously, I didn’t hear any reverb when pafl’ing on headphones - if it was system-generated, I’d likely hear identical reverb in both the room and headphones simultaneously, so I think it’s a room problem. (This puzzles me, as I’ve never heard this until recently - the acoustic panels installation eliminated the original room reverb. There have been n changes in the room in any way.) No change in the FX units or listening/mixing location (fixed sound booth). There is no speaker DSP or processing unit in this system other than a Listen iDSP Prime Level 1 Stationary RF System. This is a very basic sound system - 2 FOH speakers (Fulcrum Acoustic GX1277) in a LR arrangement. There are no fill speakers, as the room is only 38 ft. in length. (I realize fill speakers need to be time-aligned to eliminate echos, etc., but that’s not the case here.) There are no monitor speakers which can introduce feedback. (This system is for vocals only - a pulpit mic and platform mics for singers as needed.) The rest of the gear includes: AR2412 audiorack, QSC CMX800VA amp, Shure PGXD14-X8 belt pack, Shure PGXD24 w/SM58-X8 mic, Shure WL184 super-cardioid mic, Tascam SS-CDR250N recorder/player, Tascam BD-01U blu-ray player, Furman PL-8C power conditioner, Hitachi CP-WX8650W projector with Xantech DL85K IR receiver kit, and a FurmanM-8S sequencer w/RS-1 remote system control panel. Nothing has changed since installation 7 years ago. Could the amplifier be affecting the sound in some way? Perhaps the system needs to be ringed-out in the event a problematic frequency is causing the problem. (No one in the room minds how it sounds, but it sure bothers me!)
Even treated rooms will still have some natural reverb. You actually don’t want to create a completely dead room because it’s pretty unnatural. People will not enjoy singing in it either. A one second reverb time is actually on the fast side and likely within the design specs of the acoustic treatment as originally installed.
EDIT - and when I say “reverb time” a mean the length of time it takes for audio to decay in the room. Basically an RT60 time - although I would expect if you actually took an RT60 measurement in this room, it would measure longer than 1 second.
Good point. I suppose the slight reverb gives the room ‘sound character’ and you sure don’t want it to be like an anechoic chamber. Probably still a good idea to ring out the room and even have an spectral analysis done by a professional. I’ll likely find out the root cause by then. Thank you for your input.
I’ve just discovered this thread, and it is quite interesting. There have been no changes to the room acoustics, and you’re fairly sure the PA system isn’t generating the longer tails.
If I was investigating this, I would either get my ear up next to a speaker, or connect a speaker in another room to the amplifier, just to make 100% sure it is not being generated by the system.
If it is not, then I would look at perhaps the ambient noise in the room may have dropped due to a change in A/C, or other mechanical source, and with a lower noise floor, you are now noticing the lower level sounds that went unnoticed in the past.
I’ve checked into everything that was suggested in this thread, including DeltaWhiskeyBravo14’s mute test on all FXs - all normal. (i.e. no changes). I also checked the fill speakers in two other rooms (a nursery and fellowship hall) - no reverb heard from those speakers. (A good thing!) I’m absolutely convinced this is a room acoustic problem where the sound system is located, especially since I don’t hear the reverb when PAFLing with headphones. - I think that ‘nails’ it. The only things I can think of is there may be a mechanical issue with the HVAC system (I noticed rattle from it recently), plus there was a change to lighting fixtures at the rear of the room awhile back. It seems to me further acoustic treatment may be required, however a spectral analysis done by a professional should be done first. I’d like to thank everyone for their helpful suggestions which I’ve saved for future reference, if needed - greatly appreciate it! (P.S. I’ve come to the point of just living with the reverb - does make the sound more lively…)
I just did some work in a church with a mid band RT60 ranging from 3.3 to 4.7 seconds, yea that room has a lot of reverb! For reference about half that starts to sound decent with spoken word you can really understand well.
That’s about how the room was before acoustic panel treatment - the reverb was very noticeable with vocals. (i.e. spoken word) The walls and ceiling are drywall - one of the worst materials for reverb, and there’s a large window at the rear of the auditorium above double doors for ambient lighting - probably should put curtains on them. This room has a 38-foot peaked ceiling (untreated) which may be an sound issue. It’ll be interesting to find out it if the rear upper window is reflecting sound - most likely. Of course, having about 80 people in the room with heavily padded seats absorbs a good amount of sound energy, too - that helps. Great sounding room for singing - had an 8-person group on the stage recently, and it sounded great! (That minor reverb gave it ‘lift.’)