This is topic EQ'ing a poor auditorium in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Ken McFall (Member # 845) on 02-13-2010, 01:14 PM:
Here's a problem I've got with a small independant who runs a cinema in a multi use hall.
The hall is on two levels and is rectangular with seating on the two long sides and one short end. An organ is at the other short end. The lower floor is similar ecept the stage is under the organ. A very tall roller screen is dropped down from the rafters. The ceiling is pitched with exposed rafters.
Speakers are JBL's all round (Not too sure of the model but supplied by a reputable cinema supplier.
Westar 2002 sound head and 2001 picture head. CP65 processor.
The acoustics of the hall were a known problem when I installed the projection system some years ago. The local film society had ran there for some years and that was their main problem.
However recently the complaints have been worse than ever so I made a service trip yesterday.
Did a full A chain and no problems with the sound head at all. Flat illumination and responce. B chain was pretty good and I didn't have to force anything at all.
Here's the problem. End of last year they had a fault with the transformer card in the cp65 which I repaired. While waiting for me to get there thay ran in bypass and the sound was much more intelligable but very raw as there was no noise reduction or processing at all. So it was mono from all stage speakers.
This past week they have started to use bypass more because of the complaints. I've dome more eq's than I care to remember but this is the most difficult auditorium I've ever come across.
I suspect the reason that bypass sounds better is becuase the sound isspread across the three stage speakers which may be negating some of the acoustic properties if the building. Similar to the reason they use lots of smaller speakers in large train stations...
Acoustics is a very specialised science that I know practically nothing about so I'm always happy to learn.
So anyone got any ideas.
Posted by Demetris Thoupis (Member # 833) on 02-13-2010, 01:26 PM:
When doing a two floor cinema its always best if you have a multiplexer to place two mics at the ground level and two mics at the floor level. You'll be suprised how different things will sound. Also don't rely too much on the analyzer. While you may be getting good responses from the eq, it does not mean that its fine. You most probably have a lot of reverberation in that room and thus the result of lack of intelligebility you are mentioning. The other factor is that something might be happening when you are not there that you are unaware off. What kind of symptoms do they mention? Did you try leaving just the centre speaker amp on and walk around the auditorium to listen to how it sounds and then add one channel at a time to see how it changes? Wall carpet and wall treatment like curtains is a good way to kill reverberation. On the other hand, you could go with Renkus Heinz digital steerable beam Iconyx range to solve reverberation and direct the sound beams directly at the listeners ear. Renkus Heinz Iconyx Live ![[Big Grin]](biggrin.gif)
Demetris
Posted by Monte L Fullmer (Member # 2797) on 02-13-2010, 01:30 PM:
Center channel EQ levels: turn down the LF's, keep the mid range levels where they are at, and roll off the HF's after 4k.
Voice is reproduced mainly in the mid range, thus why do you need the other two sides hot of the EQ spectrum?
Works pretty good in halls and houses with acoustical problems.
-Monte
Posted by Ken McFall (Member # 845) on 02-13-2010, 01:38 PM:
They don't use the top floor so that's not an issue but yes there is a lot of reverb. I've done all of the usual checks and some of as you have suggested.
As I've said this is a long term difficulty and I'm not the only person who has tried eq'ing this place.
I was toying with the idea of bridging the left center right outputs so all stage speakers were giving the same output...
The other difficulty I have to contend with is that the guy who runs the place has an hearing aid so is totally reliant on the comments of others as he cannot hear what everyone else does.
Many of the complaints have been contradictory... muffled sound and too sharpe hf etc etc. Speach too low compared to the effects. I know some of the complaints are simply different audiences, sound tracks and age groups but the overall problem is the auditorium.
Nothing jumps out as being a fault.
Posted by Demetris Thoupis (Member # 833) on 02-13-2010, 01:50 PM:
Ken did you try listening the Dolby Jiffy test film? It can help with realising some problems in the auditorium. Again the Renkus Heinz seem to be a solution but prepare of a big cheque for each speaker! ![[Smile]](smile.gif)
The other possibility is a bad 2:4 card in the Dolby unit.
Demetris
Posted by Ken McFall (Member # 845) on 02-13-2010, 01:58 PM:
Demetris running my jiffy film was the VERY first thing I did so I knew exactly where I was starting from. No problems were evident with the speakers or matrix.
I'll give Montys suggestion another try and maybe be a bit more aggresive with the roll off's than I have been before.
Posted by Gordon McLeod (Member # 33) on 02-13-2010, 02:11 PM:
I would first look at the positioning of your stage speakers and their horns
position and aiming to minimise reverb will help
Posted by Demetris Thoupis (Member # 833) on 02-13-2010, 02:19 PM:
![[thumbsup]](graemlins/thumbsup.gif)
Ken. It's good some times to suggest obvious things in case your search has blinded you!
Posted by Ken McFall (Member # 845) on 02-13-2010, 02:20 PM:
Hi Gordon,
The speakers are positioned as close to the rear of the screen surface as possible. Unfortuatly the lower roller of the screen is at the rear so they are not as close as I'd like. Also they have to be on stands that are easy to remove as required. The horns are aimed downward to direct the hf to the audience as much as possible. Maybe I could try aiming them very sharply downwards to minimise the hf spread upwards?
There is some open space behind the lower half of the screen that has a grand piano but it is curtained. However, the top part of the screen is fully open behind, up to the rafters, where the organ is.
If you can follow my descriptions its FAR from an ideal situation for film sound.
Posted by Gordon McLeod (Member # 33) on 02-13-2010, 02:53 PM:
It may be that a narrower horn would be desirable it would also be interesting to see what a TEFF anaylzer would show on the room as the decay of the reverb sounds like part of the issue
Posted by Ken McFall (Member # 845) on 02-13-2010, 03:09 PM:
Gordon.
I don't think I'd be able to get agreement on much of a spend to investigate the issues with an acoustoc engineer or other. I certainly don't have the skills to persue things much further than I have done so far.
Demetris, you are quite right in that you sometimes don't see the trees for the woods... That's why I posted the question.
I can at leats show the posts to the guy and try a few things suggested and see what happens.
I have explained that at the end of the day he may well be stuck with things as they are. It's not his building so spending a lot of money is out of the question especially with the current finacial situation.
I'll give it a couple of weeks and maybe spend another day there just working on the sound possibly even working overnight.
Thanks everyone so far for your help.
Posted by Steve Guttag (Member # 268) on 02-13-2010, 03:26 PM:
First off...you can't fix a bad room with EQ....but here are some things to consider....
If have a reverberant room...try to stay away from direct-radiator speakers...you really want horn-loaded speakers (Altec, Klipsch, JBL PD5000 series...etc)...you want to keep the sound off the walls as much as possible.
Do NOT over-eq...particularly the HF...you will find that if you do a TEFF analysis that you probably have too much HF boost despite you using the X-curve...the X-curve presumes a normal amount of reverberation...which you do not have.
A couple of things to try...lower Left/Right by at least 3dB. They are playing mostly music...which will build up in a live room and drown out dialog...which is a series of short bursts. Don't go crazy with the bass either...watch out in the 150-250Hz range as well...don't over emphasize as everyone will sound tubby. In the States...we also have a problem with British accents in live rooms...but I suppose your people have overcome that ![[Wink]](wink.gif)
. Not to worry...Aussie accents are even worse (witness that Mad Max had to be dubbed on its original release).
This is a case where having a DSP for EQ with a wireless router and a laptop with wireless Ethernet can be a God-send since you can sweeten the sound to the room based on actual material. With tough rooms...you have to use more than just Pink Noise...you have to listen to actual voices (male and female) and listen for what is getting muddied.
Steve
Posted by Ken McFall (Member # 845) on 02-13-2010, 03:34 PM:
Thanks Steve some great pointers.
May see if I can rig up at entesion for my cat 67 E2 Alignment Extender. Would not need to be too long and I could sit in the auditorium and hear 'real' film sound live.
I'm sure I can improve on the sound but it's getting input from you guys that is invaluable given your experience.
Thanks again.
Posted by Sam D. Chavez (Member # 1841) on 02-13-2010, 03:46 PM:
Don't discount that there may be a card problem, so if you have not already done so, listen to the sound in bypass and then normal, but with flat EQ and subwoofer off, and see what you hear.
Might be a bad 222 card if I was to choose one most likely at fault.
Posted by Steve Guttag (Member # 268) on 02-13-2010, 03:48 PM:
Remember too...when in bypass...you have a compressed track and that will improve dialog in a live room as the problems are less exaggerated. There are times when good mono really does beat stereo.
Steve
Posted by Ken McFall (Member # 845) on 02-13-2010, 04:04 PM:
Steve and Sam,
in my first post thats exactly what I had explained. Bypass seemded better but raw.
I have a spare cat 222 card but not a 222sra.
I'm really not too bothered if we ended up running in 'Good' mono at the end of the day as long as I can help reduce the compalints.
You've given me a lot to think of and try out so I'll get them all a try as soon as I can.
Thanks again.
Posted by Bruce Hansen (Member # 281) on 02-13-2010, 04:30 PM:
What is the floor made of? What is the ceiling made of? What are the exposed beams made of? Having a floor and a ceiling that are both reflective can cause bad reverb problems. Can you cover the ceiling and beams with carpet? How about the walls?
Posted by Ken McFall (Member # 845) on 02-13-2010, 04:57 PM:
Wooden floor with carpet in isle, wooden beams, plaster walls with fabric window blinds lower hard board covers upper. Possibly plaster ceiling.
In general everything you don't want in a cinema!
As the auditorium does not belong to the guy he is not in a position to make any modifictations even if he was able to afford them.
The only way I can go is to try and minimise the effect by trying out the suggestions already given for which I am very greatful.
I'll pass all the info on and arrange another visit soon and have a play....
Posted by Louis Bornwasser (Member # 3063) on 02-13-2010, 04:58 PM:
Wow! Great posts guys! Especially boosting the dialog +3 db. I also think normal eq on Left and Right is OK. Run a normal film in sr but unplug/kill all but the center channel. "Play" with center channel eq just as Gordon suggested. Normally on eq, "less is more" use bass/treble mostly.
If all else fails, raise the speakers (or just the horns, experimentally)to the top of the screen and angle radically downward so as to cover only people/seats. Only had to do it twice, but it really helped.
On Dolby, you cannot sum L-C-R together to get mono so if you do this be prepared to losesome information. Louis
Posted by Brad Miller (Member # 2) on 02-13-2010, 06:00 PM:
Ugh, I feel for you Ken. I detest rooms like this. For what its worth, this has worked pretty well for me in the past
After you have verified the processor is working properly, definitely start clean by flattening your EQ cards. From there go to the center speaker only and aim it for the best possible sound (as was suggested prior turn the other channels off). Then match the angle on the left and right.
At this point you almost HAVE to have a processor that can be controlled via ethernet (or a really long DB9 cable) so you can plant your butt in the auditorium as you make changes. I will assume that will not be the case though, so go ahead and eat some donuts before you head into there to do your job, because you will more than work them off running up and down the stairs. These rooms can not be tuned well with test gear alone.
At this point get a multiplexer (don't even try with one mic) and tune the room as best as you can with the bass and treble controls only. Only then touch the other controls, and do it VERY sparingly. When you are finished, "even them all out". Don't let any control be more than 1:00 and none less than 10:00 is a good rule to start with.
Some notes, beware of the frequencies from 150-400. They are your enemy in a live room like this. Equally awful is the treble. Do a severe drop off on the treble, but make a turn back up starting at 10k. (Yes I know it sounds like the wrong thing to do, but if you don't your system will sound dull and lifeless.) Also boost your lower bass frequencies (below 80hz).
Now turn off the surrounds and play some film that you are familiar with and pay most of your attention to the dialogue first. I keep a reel just for this purpose and I have it embedded in my head how it is SUPPOSED to sound. If you hear any muddiness or boominess in the dialogue, watch those bass frequencies I listed above. They are usually your problem. Then making sure you are listening to a female voice, attack your higher frequencies.
After you have the dialogue sounding decent, start listening to everything. If you hear ANY shrillness to the sound, kill the 4-8Khz frequencies. You WILL have to do a severe high frequency rolloff to get it to sound semi-decent.
In case I didn't make it clear, be looking at the RTA while you are playing content. When you hear something that stands out, you will generally be able to see the offending frequency area.
And again, be very careful about making large changes between adjacent frequencies. At the end of the day, your ears are your best tool for the job.
When tuning the subwoofer, adjust it for a solid bottom end with a rolloff down toward its higher frequencies.
Finally, boost the center and subwoofer a little and lower the surrounds a little.
If this or any of the other tips in this thread don't work for you, go to the nearest gas station, fill up a 5 gallon bucket of unleaded, get some matches, etc.
Posted by System Notices (Member # 2357) on 06-02-2012, 12:42 AM:
It has been 839 days since the last post.
Posted by Bob Ezra (Member # 841) on 06-02-2012, 12:42 AM:
This is a case where having a DSP for EQ with a wireless router and a laptop with wireless Ethernet can be a God-send since you can sweeten the sound to the room based on actual material. With tough rooms...you have to use more than just Pink Noise...you have to listen to actual voices (male and female) and listen for what is getting muddied.