Tuning unusual rooms (practical advice wanted from pros)

[Jay Wyatt]

Hasn't Meyer put in a ton of LCR line arrays into the larger CinemaxX (primarily German cinema chain) rooms over the last decade and a half? I haven't been the biggest fan of the chain itself due to multiple reasons, but never had any complaints about the audio.

Those were done before my tenure but no they don’t appear to be line array deployments. Acheron w/ Acheron LF according to my records.

[Steve Guttag]

The R2/D2 system captures the audio a bit differently and it is a very calibrated/normalized system. Each mic is going to deliver the same effective response as they were all calibrated against the same reference. So, it starts there. Then there is how it captures it, particularly on multi-mic. Each mic is measured unto itself (you aren't capturing all mics at once...it steps through them and then does a logarithmic average over the sample time). As I said, you get a very consistent measurement to measurement average and, equally as important, rig-to-rig average. The other notable thing is if several different people do the measurement, you get, effectively, the same result, presuming the mic locations were reasonable (not off next to a wall or covered or some other disqualifying thing). But if you put your Mic3 towards house left and I put mine towards House Right...the result is going to be pretty much the same. And by same, I mean, if one person sees that the response is within SMPTE specs, they all will. There isn't going to be this "woah...what happened here" sort of response.

Again, having used one for decades now, I really trust it in a way I don't on the SMAART and I have the calibration files for the SMAART too (I'm using the Beyer MM1 with the Octacapture, for reference). There are more variable in the SMAART rig whereas the software itself is the common item instead of everything. I also note, doing Atmos systems, since "DAD" does the tuning, it doesn't use your calibration files.

[Marco Giustini]

If you "calibrate" your sound device, you'll find that it's probably very, very flat, usually not worth bothering. That said, if that was the problem, then Smaart would also delivery consistent results - consistently wrong but that's not the point.

I believe Steve's point on the R2/D2 system was that it was the only system normalising microphones 2-3-4 to microphone 1 BEFORE they were considered for the average. But now Smaart seems to be able to to the same (I haven't tested how well though) so I'm wondering whether the advantage has gone or has somehow reduced.

[Ryan Gallagher]

Our day 2 of experiments went something like this:

The live audio dept head for that room was available today, and started with putting a re-tune for a flat response on the mains via the DBX processors. Just a touch up really for what is likely some age/performance variation on them now.

He also set up the reference signals to measure system delay on both the L+R mains, and as compared to Center. We discovered DBX drive units were applying a 7 meter base delay to land the mains soundstage back to more even with typical band locations. We realized we had no way to "pull them forward" again in the CP750 or in the console. So we elected to copy all the parameters for the mains into a second preset on the DBX drive units with no delay or alternative delay active. From the middle of the house this put our measured delays about correct for the film setup.

We switched to 1 center cabinet and I put an initial level/EQ on it.

I touched up the L+R EQs in the previous day's efforts due to the processor and delays being poked.

Listened to a bunch of content. Then restored to two center cabinets and listened again with the prior day's EQ for two cabinets.

The concensus of those present was, for whatever reason, were preferring the fullness of the 2 cabinet affair. One cabinet, although clearer perhaps in prime seats, was just feeling a little too burried elsewhere.

But not being entirely satisfied with our tuning efforts from yesterday, we did one more experiment by re-applying my "last best" tuning effort on center from my prior efforts responding to complaints. It stood out as the much better center EQ with minimal dialog issues comparatively. So we merged them, Center from my efforts prior, and L+R after today's touch up, did the rounds with Surrounds and LFE too, adjusted relative levels based on SPL in the center of the room.

So big circle sorta, we are moving forward for now inheriting a lot of what I did in previous efforts on center that started from our existing room tune, but with a more recently tuned/touched L+R and some time alignment topics addressed (as much as this room permits anyway).

I am sure with a bunch more time we could have become satisfied with the entirely new tuning effort, but I have two films tomorrow, and opted to deploy a known good quantity for now (at least relative to dialog) until other efforts are ready for prime time or we get a tech to come sit over our shoulders etc.

I was a bit suprised by the consensus moving away from the single cabinet center solution today.... but I think due to placement, we'd really have to drive it hard to get the balance feeling correct in most of the room, and the down front center zone would be even more blasted than before.

Our TD was also pretty immediately sour on the single cabinet center idea on principles... I think he was willing to consider removing the splay. Is a flattened version worth even listening to with these narrow coverage cabinets? Two narrows adjacent to each other feels like it would just have more volume headroom, but be the worst of both worlds, poor coverage combined with frequency nodes/interference not dissimilar to the splay?

[Marcel Birgelen]

You mean, removing the splay mount from the speakers and aiming them straight at the audience without an angle? To me that sounds like a terrible idea. Those speakers were designed with this splay in mind, their sound field aimed in such way that the interference. between both speakers will be minimal. Sure, you can try it, maybe I'm overseeing some potential magic here, but I'd expect the interference to increase dramatically.

[Marco Giustini]

Our TD was also pretty immediately sour on the single cabinet center idea on principles

Re-do the test but this time without telling them which is single cabinet and which is double, I bet the result might surprise you

One thing I thought about the whole "one cabinet sounds better" is: if you remove ONE cabinet and you don't touch the EQ, everything is going to be different, SPL first. I'd imagine - as Jay said - you're going to lose some LF as well.

So be aware that the original "one cabinet sounds better than two" might also be the consequence of a lower SPL (= less reflections in the room) and less "boomy" sound, which might give your dialogues more clarity.

Ages ago I was doing a Dirac EQ in a very, very large room, mostly untreated. The echo was unbearable. I completed the Dirac EQ and when I went to test it with the "enable/disable" button on the AP20, the Dirac version sounded remarkably better.

Only then, did I realise I had not compensated for the level drop which naturally happens with Dirac EQ (Dirac can only cut on frequencies so the outputs normally decrease after an EQ). Lower SPL = less reverberation = clearer sound.

Once I re-balanced the levels and tried A/B again, the "massive improvement" was gone.

So bear in mind that in a room like yours, removing one cabinet might have some "positive" side effects which might "spoil" your tests.

Ideally, you'd want to re-eq every time you apply a physical change to the system.

[Ryan Gallagher]

Yes on the removing the splay idea in center, glad my instincts were mostly accurate there. Not much to gain and likely worse.

at this stage I think re-testing the single cabinet idea will only occur if the dialog complaints continue, and as far as I can hear they were mostly resolved in my first round efforts there. But yeah a blind test would be better,

we had adjusted SPL and EQ between the single/dual for the center room listening position. But we could have been just hearing flaws in my own EQ efforts for the single cabinet, and dual was inheriting the slightly better EQ I had going previously.

[Tj Hopland]

Sound like things are less bad now so that is a net gain for the customers. Hopefully many people have have leaned some things that can maybe influence whats going on in the big room and for sure the remodel in this room? What would be really cool to do now that you hopefully have some interest and attention of people that can influence future decisions is see if you can get a hold of a proper cinema speaker and for testing stick it as close to the proper location as possible possibly on a lift in front of the screen? Run similar tests and let everyone hear what sticking a correct speaker in the correct location does.

Do you have a cinema dealer you work with? They should have or know where there are things laying around. If they don't have 'stock' they should know that so and so has a spare speaker behind a screen or in a store room that could maybe be borrowed for testing. If you don't have a cinema dealer then check with whoever is doing the live sound, they should be reps for at least one brand that has cinema specific systems and can maybe send over a demo unit. Could always check marketplace and local auctions, cinema speakers often end up on those sorts of sites and usually go really cheap.

[Marco Giustini]

we had adjusted SPL and EQ between the single/dual for the center room listening position. But we could have been just hearing flaws in my own EQ efforts for the single cabinet, and dual was inheriting the slightly better EQ I had going previously.

Ah ok, sorry for assuming you didn't do that
Well, then two cabinets it is! I'd still love for you to do a blind test and see if the outcome changes!

[Ryan Gallagher]

Sound like things are less bad now so that is a net gain for the customers. Hopefully many people have have leaned some things that can maybe influence whats going on in the big room and for sure the remodel in this room? What would be really cool to do now that you hopefully have some interest and attention of people that can influence future decisions is see if you can get a hold of a proper cinema speaker and for testing stick it as close to the proper location as possible possibly on a lift in front of the screen? Run similar tests and let everyone hear what sticking a correct speaker in the correct location does.

Do you have a cinema dealer you work with? They should have or know where there are things laying around. If they don't have 'stock' they should know that so and so has a spare speaker behind a screen or in a store room that could maybe be borrowed for testing. If you don't have a cinema dealer then check with whoever is doing the live sound, they should be reps for at least one brand that has cinema specific systems and can maybe send over a demo unit. Could always check marketplace and local auctions, cinema speakers often end up on those sorts of sites and usually go really cheap.

Staff and technical managers here are very aware of the benefits of properly placed film channels... there were just too many logistics with the minimal staffing when this room was outfitted to permit a more elaborate deployment of screen channels. The projectionist alone is often responsible for the full setup and tear down of the cinema configuration before and after a screening. Even if we had benefit of a perforated screen, 3 screen channels on crank ups (or even one) might have been a bridge too far on labor budgeting, storage, and time/safety. A motorized truss like we had next door would have been ideal, but the storage (out) location would have been problematic, and not enough staff to otherwise set it up and break it down for storage elsewhere every film call.

If this room was staying open another couple years there would still be high value in considering alternative center channels, screen channel placements, and a professional re-tune. That is just not the timeline it is on and influences budget and priorities.

I know this theatre will likely still have a roll down screen in it's rebuild, it is going to become an even more hybrid space... with configurable seating vs standing GA/comedy dinner-theatre but there was discussion of it becoming an ATMOS room, so a more complete dedicated film effort in design of the new room is certainly in the cards.

I think it's too far out to know the integrators on this one. Brown Note and BLS (for 35/70mm) are involved in elements of the big venue currently undergoing the architectural restorations, there may be others I'm not privy to yet.

Even if we never re-visit this subject due to complaints vanishing, a lot was learned in a short amount of time, discovered configuration aspects we were not considering (drive rack soundstage delay). I now have a slightly modified tune to actively listen to and critique, as well as at least a couple alternative experimental tunes I can just play with to my hearts content to develop better ears for this sort of thing aside from X-Curve starting points. The mains used for all the remaining live shows also got a tune up and re-focus... so benefits were had all around, even if they were incremental. I think we safely dodged a "one step forward two steps back" scenario though. At minimum we solved a historic SPL issue between L+R and C. L+R were always prone to ripping your head off with sound effects, and we had gotten in the habit of pulling those faders -3 to -5db below unity on the console when noticing particularly offensive balance issues.

Edit: Loaning in an alternative wider focus center cabinet is an interesting test. But unless Mgmt was came around to considering spending money on something, it might be difficult to arrange for purely A B listening tests for curiosity sake. We do have some dealers and techs we regularly interact with for festival needs, one of whom is local-ish. It would probably more resemble me phoning in a favor, and I'm leary of continuing to push more payroll time into this experimentation path.

[Ryan Gallagher]

Subjective results (to my ear) after four 5.1 films with our slightly tweaked situation. Overall the room is just sounding much more balanced and knit together. Relative channel SPLs were probably a big part of that, and maybe the removal of the L+R soundstage alignment for live events.

I can still detect a hint of our perhaps room dependent problematic frequencies in dialog if I intentionally listen for them, but they are very much minimized into the background now, with enough of the other needed frequencies present for intelligibility over them without getting distracted.

Have not felt a need to ride the L+R console faders to balance dialog to score/effects at all. Have been closer to reference on playback levels when making that decision too.

I'm gonna see if management will let us experiment with a reflection absorbing audio rug and pad downstage of the center channels next.

I'm still encouraging management to get dolby or a tech out to critique our efforts. Just in education alone there is value to sit through it with someone who has intimately familiar material to spot further areas of improvement that are possible given the limits of the cinema deployment, or point our our newbie mistakes in over-relying on measure curve fitments and over-adjusting for this live room. But that decision is above my pay grade. If I had to guess it will be only if complaints continue.

We'll play with more LFE analysis and alternative placements and time alignments to mains subs when that RMA repair comes back.

If we repeat a A to B single versus double center cabinet experiment... I'll do it with a flat EQ and only SPL adjusted... to really listen/measure for what problems the pair is potentially causing compared to the single. I think my imperfect EQ efforts on the single colored our survey results last time.

[Marco Giustini]

reflection absorbing audio rug and pad downstage of the center channels next.

Remember that the ability to absorb sound is proportional to the thickness and density of the material - it has to do with the wavelength again. A thin rug, might absorb 10K but not 1K. When it comes to sound there is a lot of black magic involved (see "directional sound cables") so be careful when you search for materials!