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Author Topic: QSYS Corner Sean McKinnon Phenomenal Film Handler Posts: 1712 From: Peabody Massachusetts Registered: Sep 2000 posted 02-15-2019 08:49 AM                        Not to de-rail another thread but I think that the biggest "Bang" for the buck with Atmos is the bass management subwoofers in the surround field. I find this to be such an improvement I am starting to include them in my 7.1 designs where appropriate.This brings another benefit of Q-Sys in that I can build a bass management signal path to cross over the surrounds and send that audio where I want. I can also mix in the regular .1 if I want. As a matter of fact I did a Q-Sys install recently where I felt the stage channel speakers did not go low enough (this was a specialty install that required unique non-cinema loudspeakers) so I was able to high pass the stage channel and mix all of that information into the subwoofer channel. It sounded GREAT! you COULD NOT tell that the low frequency information wasn't coming from the same place as the high frequency information. Once your ears localized to the HF it all appeared to come from there. I have also done an install where I did a "7-way" loud speaker system which consisted of two seperate High/Mid Boxes (These were flown and are very "high q" speakers so one was for the underbalcony and the other was aimed for the balcony) and a subwoofer for the low end of the channel. I also did the reverse of the above here and mixed the .1 (there were 5 subs three for each screen channel and 2 for the .1) into the screen channel subs and it totally rocked the house! These are things that I could not have done with a traditional cinema processor easily if at all.  |  IP: Logged Harold Hallikainen Jedi Master Film Handler Posts: 906 From: Denver, CO, USA Registered: Aug 2009 posted 02-15-2019 09:32 AM                        It's also possible to do simple bass management with the JSD-60 by mixing additional channels into the LFE which then passes through the SMPTE 125 Hz LPF. Harold  |  IP: Logged Carsten Kurz Film God Posts: 4340 From: Cologne, NRW, Germany Registered: Aug 2009 posted 02-15-2019 10:17 AM                     The AP20 can do that as well in it's output matrix (doubling surround outs and adding low pass filters), and yes, I think with todays more advanced sound tracks, this will certainly pay out and is a comparatively cheap improvement. - Carsten  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 02-15-2019 10:55 AM                     The DCP line of processors also offered bass management. Bass Management can get tricky when you factor time alignment into it since each speaker, relative to the subwoofer will have a positional difference as well as level and you don't want to create a null. But, like Sean, I have done non-traditional speakers (flown) and wanted to have bass-management as an option and with QSYS you can switch it in/out and decide which works best for the equipment and the venue. Here is one I recently did: So you can quickly set the turnover frequency, level (per speaker or overall to the LFE) and any necessary delay). I don't know if I agree with Sean on the benefits of surround LFE or not. I've had surrounds that can get down to 40Hz on their own and some people complaint that they don't hear them. If you make them mid/high centric, people notice them more even at the same SPL. I also think that one shouldn't tune surrounds to the same "X" curve as the stage. Most of what one hears from the surrounds is direct so no large-room type roll off should be applied. (and I'm sure Harold will bring up the current theory that the "X" curve has screen loss built in, but we'll leave that for another discussion). I definately push the roll off on the surrounds out further (flat to 4-8KHz and then a gentle roll). When one listens to a sweep around the room, if surrounds have the same roll as the stage, their timbre gets very dull compared to stage and it shouldn't be the case if not the opposite (they aren't playing through a sheet of vinyl). That said, I plan to play with Surround LFE a bit to see the benefit they really bring (which I'm sure is soundtrack dependent). They are expensive and require more extensive rigging.  |  IP: Logged Sean McKinnon Phenomenal Film Handler Posts: 1712 From: Peabody Massachusetts Registered: Sep 2000 posted 02-15-2019 11:55 AM                        I am curious what he argument is surrounding the "x" curve having screen pre emphasis built in? Since our measurement is taken beyond the screen and in the far field I can't see how the curve that we are trying to reach would have any built in pre emphasis. Now... since the mixing stage has been calibrated to the same curve and if their speakers are behind a screen I could see how there would be some HF pre emphasis in the actual content so unless your playing your screen channel information through your surrounds you should be ok! I find that most good surrounds like from QSC, or JBL, or even Klipsch do not need that much adjustment. I have had good results from finding the surround that is closest to the "x" curve out of the box and using that trace as my "target" so that all of the surrounds have the same tonal quality without over eq'ing them.  |  IP: Logged Harold Hallikainen Jedi Master Film Handler Posts: 906 From: Denver, CO, USA Registered: Aug 2009 posted 02-15-2019 12:21 PM                        http://www.screenexcellence.com/downloads/SMPTE_TC_25CSS_B_1_oct_2014.pdf#page=87 Quoting: The responses of the close-field microphones and the averaged close-field response of the reference cinema are far from flat. In general, the responses of the close field microphones above 1 kHz show strong similarity with both the reference position and average responses. There is a little more high frequency energy in the close field responses, which is consistent with the loss due to air-absorption as the sound travels to the audience area. In other words, the close-field microphones essentially show an X-curve with a little more high frequency response, corroborating the results shown in (2). e) 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. In addition, venue F in the report above (a dub stage where I was there for the measurements) has a woven screen. Electronic equalization is set to roll off the highs of the screen speakers since the screen does not. Further, a paper by Brian Long (of Skywalker Sound) and others has frequency response measurements of various perforated screens. They are very close to the X-curve. Harold  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 02-15-2019 01:11 PM                     I would say that the paper didn't look at enough rooms to draw the conclusion and I would definitely look at some extremes (large reverberant and small and dead). I have definitely seen large rooms have a steeper drop-off and if corrected, sounded very spitty. I've had the reverse true too...small dead rooms where the HF was dull. I don't dispute the effect of the screen on the response, or what work the HF driver has to do to compensate but I think the final response is the sum of what the sound went through and by tuning to a common response (dub-stage/cinema) you have taken the screen out of the equation if both rooms have similar screens. What is left are the effects of the room's RT60 and equipment (speakers).  |  IP: Logged Carsten Kurz Film God Posts: 4340 From: Cologne, NRW, Germany Registered: Aug 2009 posted 02-15-2019 01:13 PM                     Brings us too far off the QSYS corner. But keep in mind, in many constant height/variable width installations, L and R may also suffer additionally from screen masking in flat position. - Carsten  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 02-15-2019 03:43 PM                     Actually, with DSP like QSYS, you could keep track of masking open/close and adjust according by format! That said, decent masking does very little attenuation. It is about .5dB overall with about a 1dB drop at 20KHz and less the lower in frequency you go.  |  IP: Logged Scott Norwood Film God Posts: 8146 From: Boston, MA. USA (1774.21 miles northeast of Dallas) Registered: Jun 99 posted 02-16-2019 09:37 AM                        I don't know much about Q-Sys (I still live in analog-land as far as sound systems are concerned, for better or for worse), but am curious as to what is required on the network side. Does it use IP or its own protocol? Is anything special (MTU sizes, etc.) required in the swtich configuration? Presumably, it should live on its own VLAN, correct?  |  IP: Logged Leo Enticknap Film God Posts: 7474 From: Loma Linda, CA Registered: Jul 2000 posted 02-16-2019 12:52 PM                        It uses what QSC calls a "Q-LAN," which is essentially a physically independent LAN, separate from the management and media networks. All the digital audio data between the core, and input and output points (cards in the core, DCIO, power amps, etc.) travels on the Q-LAN. The core will connect to the management network as well as the Q-LAN (and is therefore device through which the Q-Sys interacts with external, non Q-Sys devices), but only Q-Sys devices should be connected to the Q-LAN. The Q-LAN uses IPv4, but the subnet is totally different from that of the management or media networks. The Q-LAN can be redundant: you can choose to have two of them, with separate switches and cables. There are technical specifications for the managed switches in a Q-LAN, and things that have to be configured in them, for it to work. I have these in my notes from the training, but can't remember them off the top of my head. QSC also publishes a list of known good models. The bottom line is that most enterprise grade managed switches will work, but they do have to be configured to do some managing. You could be right in that enabling jumbo packets is one of those settings - I can't remember. One gotcha, which I found out the hard way at the Egyptian, is that the hardware in the primary and backup Q-LANs have to be of the same model in order for the automatic switching to work if one fails. Shortly after the system was installed, I got a panic phone call: all the stage channels had gone out. This system consisted of power amps for the stage channels behind the screen, and for the surrounds in the booth. The Q-LAN was redundant, with switches in the booth connected to switches behind the screen using two separate fiber runs. To cut a long story short, it turned out that the model of fiber transceiver being different in the primary and redundant Q-LAN switches at the stage end was what prevented it from changing from the primary to the backup automatically when the power supply board in the primary Q-LAN switch at the booth end failed.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 02-16-2019 01:19 PM                     It uses standard IT stuff...BUT...there are criteria for a successful implementation. The chief of which is a strict QoS policy (Strict Priority) to ensure that audio always gets through in a timely fashion. That said, the more things you do to let QSYS live in its own world, the better. I have completely separate networks for it. In particular, I tend to have QLAN-A only have QSYS devices on that network. Once configured (IPs set), there is no need to communicate, directly, with a QSYS device besides the CORE. Larger COREs like the 510 have 3 NICs so one can have two QLANs and a separate AUX NIC to be on your control network. QSC has documented the requirements and suggestions for the network and network switches. QSC also has preconfigured switches (OEM by Dell that QSC supports directly). For fun reading here are some links to the QLAN specifications/recommendations that might make sense to you: https://www.qsc.com/resource-files/productresources/dn/q_dn_qlan_notes.pdf https://www.qsc.com/resource-files/productresources/dn/3rd_party_control/q_tn_sys_dn_qsys_switchtesttopology.pdf https://www.qsc.com/resource-files/productresources/dn/3rd_party_control/q_tn_sys_dn_qsys_generalswitchrequirements.pdf https://www.qsc.com/resource-files/applicationguides/systems/q_ag_sys_dn_qsys_vlan.pdf Leo..Jumbo packets are to be avoided on a QLAN to avoid timing issues. So I'm guessing that nobody tested your redundant system before it was actually needed? I know that I've always checked mine on installation to verify good fall back (device by device too).  |  IP: Logged Leo Enticknap Film God Posts: 7474 From: Loma Linda, CA Registered: Jul 2000 posted 02-16-2019 01:41 PM                        I didn't install it (I was just an end user, not an installation tech, at that point, and had not done any formal Q-Sys training: I since have), but was assured that both the primary and backup Q-LANs had been tested. However, I have a strong suspicion that while they had been tested independently, automatic switching between the two had not: at least, not that specific cause of failure. All the switches involved were of exactly the same model and hardware revision, and QSC-approved: it was just the fiber transceiver module in one of them that was different to the other three. When we replaced that with the same model as the others, we simulated the failure again with a DCP playing (by pulling the power cord from the switch that had failed, which by then had been replaced with an identical, new one), and the fallback didn't even interrupt the audio playback.  |  IP: Logged Sean McKinnon Phenomenal Film Handler Posts: 1712 From: Peabody Massachusetts Registered: Sep 2000 posted 02-19-2019 12:24 PM                        I have heard claim that Q-Lan does not need to be its own separate V-Lan and can share with Dante and regular TCP and UDP traffic. I usually V-Lan but in a recent small install I did not. The management and Q-Lan networks for this single screen live together and they are just fine. FWIW YMMV  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 02-19-2019 02:49 PM                     I'm willing to let LAN-B in a redundant network system live on the "Management" (or Control network) but I'll always let LAN-A be an island. My other thought is to use the router to allow automation commands to go to/from QSYS and the Management network. CORE's can even have persistent static routes put in them via Configuator.  |  IP: Logged

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