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Author Topic: Mixing room speakers, information about Hornspeakers Chris Erkal Film Handler Posts: 6 From: Hagen, NRW, Germany Registered: Oct 2018 posted 12-09-2018 08:23 AM                     Hello! I'm new here - and in the whole film scene. I have a background of a self taught mixer (of audio for music, radio plays and installative pieces) who is into his first feature film. It's an independent production, I've also done set tone/boom, part of the sound design and score. I mix for 5.1. We have checked a small piece of the movie as a dcp test in a smaller cinema here in Düsseldorf, Germany. Levelwise, localization and general "fit" were good, I just experienced the way the speakers transmitted the sound, especially the dialogue, a bit "off". I didn't check yet which brands and models they used but these were def. horn speakers, which I've read about often in the context of cinemas. The dialogue lacked a bit of clarity (not intelligibility), they didn't sound super muffled, some consonants and esses were a bit harsh, but especially right below the highs I experienced a little peak. Maybe at 7kHz starting the Highs rolled of a bit, they weren't super present, compared to memories of other movies I got in this theatre. I do my main work on active Yamaha Speakers (Hs 80m) and can check sporadically on Genelec 1032 and a BlueSky System in a treated room. It's nice to figure out room modes and general balancing. But what do I have to "aim" for to get a more natural sounding dialogue on a cinema system? It seems like a high mid boost is going on, but it's always nice to have some reference recomendations from people who can rely on experience. Let's all assume that my dialogue sounds good, i.e. cinema-esk on the different monitor systems (and headphones). Is there any general charateristic of a cinema PA I have to hear out for? Is a horn speaker a generalization that is worth to use in order to differentiate the cinema-realm from the Hifi or music realm or is it nonsense to think that way? I might get another test screening but before I wanted to get some information in order to verify what I've heard. Thank you very much!  |  IP: Logged Carsten Kurz Film God Posts: 4340 From: Cologne, NRW, Germany Registered: Aug 2009 posted 12-09-2018 08:45 AM                     Hi Chris, I guess before you adjust your mix for a single, unknown cinema auditorium, you should make sure that the sound system is properly set up and calibrated. An easy first step is to create a DCP with Dolby/SMPTE Pink noise at -20dB RMS FS and do at least some basic frequency response and SPL (C) sound pressure measurement at your listening position in that auditorium. Yes, normally, all cinemas should be calibrated and tuned properly, but even if staff claims they have been calibrated 'at some time', you need to get confidence yourself. I also suggest you take the time and read this: http://www.associationdesmixeurs.fr/wp-content/uploads/2017/09/NIVEAU-DE-MIXAGE-CINEMA.pdf Especially the parts that deal with near field monitoring. - Carsten  |  IP: Logged Chris Erkal Film Handler Posts: 6 From: Hagen, NRW, Germany Registered: Oct 2018 posted 12-09-2018 09:16 AM                     Hello Carsten, thank you for the quick response. Good thoughts, I will ask for an opportunity to do a measurement there! I assume you print a dcp with various signals assigned to the individual channel over time for this purpose and set the dolby unit to 7? I'll work through the paper as well. Best regards Chris  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 12-09-2018 09:25 AM                     If I were you, and I was really concerned with how a mix sounded in a theatre, I would have a set of theatre speakers and room to test my mixes in. Sort of why there is a pair of Yamaha NS10s in most mixing rooms...to simulate the "typical" home speaker. Most cinemas use some form of 3-way speaker now (for better or worse) and in the USA, JBL and QSC are the dominate manufacturers. Listening on a JBL 3732 or a QSC 323 (or the new 223) might give you some insight (neither are the company's top of the line either). Likewise on the surrounds, these are often not stellar pieces so using a high-end studio speaker may not give you the "feel" of a cinema. But also remember, you are not working in the size of a cinema so the RT60 times will be different too.  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 12-09-2018 10:58 AM                     Back in the day(1980's & 90's) most west coast re-recording rooms were equipped with real world theater speakers, although it was always kept up to date with the latest components released and they were either bi-amped or tri amped depending on the speaker. Todd-AO had five Altec A-4's in the big room where most major Hollywood movies were mixed up until the demise of that location. Saul Zaentz also had Altec A-4's. Both rooms were capable of ear drum shattering levels and they sounded awesome. Lucas used a mix of EV and JBL... some times in some systems the top end was EV and the bottom end JBL. They used what ever they felt gave them the best results in a given room. Yamaha NS-10 is a shitty speaker and hardly represents real world today. Mark  |  IP: Logged Marin Zorica Jedi Master Film Handler Posts: 671 From: Biograd na Moru, Croatia Registered: May 2003 posted 12-09-2018 12:42 PM                     If you're goal target for future DCP is cinema audiances, there is no doubt you NEED to mix it in real cinema. Not mean normal "cinema", but i mean for setup, that way you will get max out of sound that audiance will be hear in cinema when played back. I have experiances with "bas" sounding mixes in real theater where guys would come to pre-check and they would keep talking sound is bad, and in studio were ok.....al because in studio they would be using quite normal 5.1 near field setup. There RT60 reverberation is close to 0, horns are not used (which are common is cinemas as you said, and for reason) etc......cinema setups are common by horns still back from 40's, back there because of lack of power in amplifiers, so you compensate that by horns, and by fact that you should have effect that sound is comming from one point to whole auditorium, etc.... So when mixing film, point is not to make is great, but to make it best sounding in cinemas. This reminds me to first situation, because while listening to those guys mix, yes, sound was bad....in same room, while playing some other material, sound was great......because they made it sound great on small studio speakers like yamaha NS10, which is not bad at all, it's great studio nearfield monitor used in 90% of studios. Another situation was in Croatian national TV....a younger sound guy did mix some overdub on some documentry.....and they had Genelec in CR, plus normal TV set used worldwide......as for sure, that one did hear mix only in new genelec, older guy came in and wanted to hear it on TV set....which, you guess sounded awfull! He did remix all based on TV set sound, as, that is real situation where audiance will be watching and listening to that documentary.  |  IP: Logged Harold Hallikainen Jedi Master Film Handler Posts: 906 From: Denver, CO, USA Registered: Aug 2009 posted 12-09-2018 01:51 PM                        During the mix, were speakers behind a perforated screen? They are, of course, behind a perf screen in a cinema, which results in a 3 dB / octave rolloff from 2 kHz to 10 kHz, and then 6 dB / octave above that. So, to hear what you'll hear in the cinema, yu either need to shoot through a screen or apply similar rolloff in your monitoring Harold  |  IP: Logged Chris Erkal Film Handler Posts: 6 From: Hagen, NRW, Germany Registered: Oct 2018 posted 12-09-2018 03:14 PM                     Thank you all for the model recommendations and experiences. Steve Guttag: Yes, since I on a cinema mix, a big dub stage would be awesome. Unfortunately I don't have access to one, so I've got to approximate somehow. Well, at least the DVD version will be easy to accomplish afterwards, won't it? Mark Gulbrandsen: When working on music I always keep wondering, what's the real world today, system-wise: smartphones, bluetooth speakers, etc. So I aim for a broad perspective. Cinema mixes on the other hand appear to have this very narrow perspective of what works and what doesn't. Marin Zorica: it appears as if you describe my situation. Well, I doubt that my brain is able of make up for the RT60 differences, but you gotta start somewhere! I try to consciously experience the differences. E.g. the placement of a cinema surround vs. a 5.1 equidistant setup: If you dig into the whole topic of mixing for cinema surround it's obvious, but it's nice to hear how different a diffuse surround works on a mix in comparison to a directed 5.1 surroundspeaker So, obviously there are two important factors when it comes to "cinema sound": The size and aural tuning of a cinema or dub stage and the used loudspeakers. As far as seperating the two is possible, let's virtually do this for the sake of the question: Is it possible to describe certain characteristics of a horn speaker that would seperate it from a music studio monitor? What are these? I'd be happy for some reads! I haven't found useful information yet and still await Glenn Ballous Handbook for Sound Engineers to be avaible to arrive in my library. I understand, that hearing one and working with a horn loaded speaker is the way to go, I still feel that knowing concepts help to tune your ear for the right spots. --- Harold: No, they werent! Whats worse, in the room with the Genelecs and BlueSky monitors, the center speaker is as far away as the distance towards the L & R speakers... Would it be suitable to programm an EQ for the C channel to simulate the screen?  |  IP: Logged Carsten Kurz Film God Posts: 4340 From: Cologne, NRW, Germany Registered: Aug 2009 posted 12-09-2018 05:38 PM                     You could probably do some tuning, but, you need some back and forth between your studio and a 'decent' cinema. Repeatability is very important, and you won't get that with a minimum of measurements. - Carsten  |  IP: Logged Harold Hallikainen Jedi Master Film Handler Posts: 906 From: Denver, CO, USA Registered: Aug 2009 posted 12-09-2018 05:44 PM                        I think it would be worthwhile programming the equalizer to simulate the X-curve. If the speakers are flat, the curve should simulate the screen plus any correction applied by auditorium equalization. The curve is linear on a log frequency curve. It's -2 dB at 31.5 Hz, 0 dB at 50 Hz, 0 dB at 2 kHz, -7 dB at 10 kHz (-3 dB / octave), and -11 dB at 16 kHz (- 6 dB /octave). It'd be nice to apply this with a few slope filters instead of a graphic eq to minimize the number of filters. I think this would sound better when played back in a cinema. You can either do a high frequency cut before driving the speakers (but the recording is before applying this cut), or listen flat and apply a complementary high frequency boost to the recording. Though not everyone agrees with me, I think of the X-curve as a pre-emphasis / de-emphasis network where the de-emphasis is applied by the screen. You boost the highs on the record side to compensate for the loss on the play side (through the screen). I was at Dub Stage F referred to in http://www.screenexcellence.com/downloads/SMPTE_TC_25CSS_B_1_oct_2014.pdf#page=175 during the measurements for this report. This dub stage uses a woven screen instead of a perforated screen. The woven screen has much less HF loss than the perforated screen, so they have to roll off the highs before driving the speakers to simulate a perforated screen. This is mentioned in section 20.4.1. I remember a graph of the applied eq being in the report, but it looks like it was removed. It had HF rolloff. By the way, SMPTE has a new study group on "B chain expectations." Interested people are invited to participate! Harold  |  IP: Logged Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 12-09-2018 05:48 PM                     Harold I don’t think the X-curve is there because there is a screen in front of the speakers. EQ compensated for that and the response could be flat if needed. Whether there is a screen or not, the same X-curve - or similar curve - should be adopted.  |  IP: Logged Harold Hallikainen Jedi Master Film Handler Posts: 906 From: Denver, CO, USA Registered: Aug 2009 posted 12-09-2018 06:20 PM                        Thanks for the comment! Here's a report showing screen HF attenuation http://www.screenexcellence.com/downloads/ISVR_screens_evaluation.pdf#page=2 . There's a similar report from SMPTE from 1982 at https://ieeexplore.ieee.org/document/7245270 and another from SMPTE in 2012 at http://www.acousticdirections.com/wp-content/uploads/smpte_mot._imag._j-2012-long-46-62.pdf . From http://www.acousticdirections.com/wp-content/uploads/smpte_mot._imag._j-2012-long-46-62.pdf#page=15 , "As shown in Fig. 34, when the on-axis frequency response is smoothed over a third octave bandwidth, the loudspeaker’s frequency response falls in the tolerance bands of the SMPTE 202:2010 X-curve standard when the theater-perf and mini-perf screens are used. We conclude that the screen itself is one of the greatest contributors to the frequency response observed in a cinema. In contrast, the woven screen shows a much flatter response." Harold  |  IP: Logged Marco Giustini Film God Posts: 2713 From: Reading, UK Registered: Nov 2007 posted 12-10-2018 01:38 AM                     Harold Indeed the screen provides an HF attenuation but that’s not the reason why the pink noise is eq’d to the X-curve in a cinema. If you place speakers behind a screen in a small listening room, you’ll likely end up with an almost-flat curve if you wanted to match the timbre of a bigger room. In other words, if you removed the screen from a cinema and you wanted to achieve the same sound timbre than when the screen was up, you then need to lower the HF to match the same XCurve that you were using before. Ergo, a screen is not sonically necessary to achieve the sound required in a cinema as long as the sound system is eq’d properly. This is AFAIK, happy to be corrected of course.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 12-10-2018 07:58 AM                     Marco is correct. The "X" curve was developed as a repeatable means to use common materials of the 70/80s (and today) to achieve a more uniform response in cinemas and dubbing stages. The common materials being a pink noise source and an RTA, preferably 1/3-octave or greater. Pink Noise, a steady state source. will cause an RTA to pick up both direct and reflected audio. The RTA will capture both and sum them, despite the reflected audio having a time component to them due to their extra travel time. This will add in a negative manner, however. The low frequencies will not be as affected as the longer wavelengths will cut through the walls or be absorbed in them (depends on your walls and their construction). The double-hinged characteristic of the "X" curve is a straight line approximation of the decay due to direct and reflected audio. It also takes into account, above 10KHz where very little information is recorded and the ability to get that audio through a screen gets progressively harder but primarily it accounts for the RT60 (reverberation of the room). With or without the screen, the desired response for a given room should be the same. Screen compensation is a separate entity entirely and, as a consequence of tuning, gets factored in since the microphone doesn't know if there is a screen there or not. As RT60 times go down, the "X-Curve" should be adjusted up to a more flat position (smaller theatres). As RT60 times go up (larger theatres) the X-Curve should be adjusted down. SMPTE 202 has/had table A.1 (I don't have the latest in front of me) that gives some X curve adjustments based on theatre size (seat count). It is telling of the era in which the X-Curve was developed in that the middle portion of the adjustment is for a 500-seat theatre (conventional seats, not recliners). A size that might be considered large today. That said, due to stadium seating, the volume of the room versus seat count is not as constant (still some variations) as it was in a traditional sloped floor era. Furthermore, the acoustic treatment of the room plays a big roll (including the space above the ceiling tiles). Does one want a ultra-dead theatre and tune for "FLAT?" No. A little reverberation has been shown to improve intelligibility in a theatre environment. Ever try to talk to someone in an anechoic chamber? It is VERY difficult. You have to be staring right at them and at close distance.  |  IP: Logged Harold Hallikainen Jedi Master Film Handler Posts: 906 From: Denver, CO, USA Registered: Aug 2009 posted 12-10-2018 09:47 AM                        Thanks for the comments! As I said at the start, not everyone agrees with my X-curve thoughts! Here's a bit more of my reasoning. Impulse response can be used to determine the frequency response without reflections by doing the analysis with a short window. Looking at http://www.screenexcellence.com/downloads/SMPTE_TC_25CSS_B_1_oct_2014.pdf#page=38 , we see "Although minor differences can be seen, the responses of the RTA and steady state IR methods are very similar." To me, this is because HF reverberation in a cinema auditorium is quite low relative to the direct sound, so it contributes little to an RTA reading. From http://www.screenexcellence.com/downloads/SMPTE_TC_25CSS_B_1_oct_2014.pdf#page=87 "In all venues, the responses of the 10 ms, 50 ms, 48 PPO and 2 second windows are remarkably similar from approximately 800 Hz up. This indicates that the direct field strongly dominates the measurements, and that reverberant build-up contributes only a small amount of sound to the total energy at these frequencies, even deep into the rooms. This behavior is strongly similar to the cinema measurements described in (4)." "One component of the change in frequency response described in (8), apparently due to the effect of the reverberant field clearly does not occur here. There is nothing to suggest that the X-curve as measured in the room is a measurement artifact resulting from reverberant buildup; i.e. an artifact resulting from steady-state measurements of typical cinema acoustics." As mentioned, I participated in some of the tests for this report (at Dub Stage F) and helped with the writing of the report. I believe it, including its conclusions, is accurate. Again, SMPTE is a new study group on B-Chain expectations. Anyone interested is invited to join. Thanks for the interesting discussion! Harold  |  IP: Logged

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