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Author Topic: the 5.1 delima  (Read 2730 times)

Brent Handy

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the 5.1 delima
« on: January 04, 2007, 09:47:58 pm »

I am seeing many people not follow the surround monitor recommendations by the big boy wing.  I was just wondering if the best option for a surround monitoring set up would not be a rectangular room, with consistant, broadband trapping throughout, as opposed to splayed walls and big glass windows/doors on the sides.

What's your thought on that?  Should we not be reworking our rooms so that the surround speakers have the same "soffit" mounting as those in the front of the room (if they are)?  Should we not move towards the same amount of bass trapping in the front as in the rear of the room, since many engineers mix full bandwidth material in all speakers?

What about the rooms with splayed walls with glass doors?  It seems to me that some of the people that leave them open, would be doing more harm than good, trying to eliminate reflections, but changing the volume of the room.

Thoughts?
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jfrigo

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Re: the 5.1 delima
« Reply #1 on: January 07, 2007, 05:33:45 pm »

If you are suggesting a mirror image room, then no. There are three speakers up front aiming more directly to the rear, you are seated facing the front (and have directional hearing), and the rear speakers are more to the sides and pointing somewhat more inward. All of these factors, not to mention functionality and ergonomic issues, mean that things aren't going to be exactly mirrored. Yes, you have to take into account rear speakers when figuring out the treatments and geometry, and while a surround room should work for stereo, there is no guarantee that a stereo room will work well for surround. There are significant differences, though there are also significant similarities.

Rectangular rooms are pretty easy to predict, and with treatment, can work fine for stereo or surround. However, you don't need to avoid splaying altogether for a surround room. You do need to be careful about where you are sending reflections and what treatment they will encounter at the first reflection points of all 5 full-range speakers. If you ray trace the room, you can come up with a non-rectangular geometry that will work just fine.

For wall or soffit mounted speakers, if they are soffited up front, they should be soffited in back. If you can't use identical speakers, they should be timbre matched and substantially similar. This means you can get away with, for example, Quested 412s for L,R, and 212s for C, LS, and RS. They are the same drivers, same kind of box, and same electronics. The 212s just have 2 less woofers. You wouldn't use 212s up front with some bookshelf speakers in back, or Questeds in front and PMCs in back. However, realistically and practically speaking, though idetical is ideal, it is not imperative given reasonable planning.

As far as doors, windows, and glass or reflecive surfaces in general, you want symmetry, and you want to choose the placement and geometry carefully so that they don't cause reflection problems at the listening position. You also will take into account the reflective surface area vs. the absoption. You don't want a room completely covered by absorption, and given that you will have hard surfaces, you can place them such that they won't cause problems, and there's no reason that doors can't be some of those hard surfaces.

The last point to remember is that control rooms are places to get work done; they are not acoustics labratories. If you need a window to help your workflow, then put it in. You need to figure out how to impliment it to avoid problems, but the last thing you want to do is avoid things that will make your work better in a misguided quest for so-called "perfect" acoustics which simply don't exist, especially in small rooms.

Remember, the examples above are with music oriented rooms in mind. Re-recording stages and movie theaters are also surround environments, but with some different criteria, including greater room volume, surround arrays instead of direct radiators, and different absorption characteristics.

Brent Handy wrote on Thu, 04 January 2007 21:47

I am seeing many people not follow the surround monitor recommendations by the big boy wing.  I was just wondering if the best option for a surround monitoring set up would not be a rectangular room, with consistant, broadband trapping throughout, as opposed to splayed walls and big glass windows/doors on the sides.

What's your thought on that?  Should we not be reworking our rooms so that the surround speakers have the same "soffit" mounting as those in the front of the room (if they are)?  Should we not move towards the same amount of bass trapping in the front as in the rear of the room, since many engineers mix full bandwidth material in all speakers?

What about the rooms with splayed walls with glass doors?  It seems to me that some of the people that leave them open, would be doing more harm than good, trying to eliminate reflections, but changing the volume of the room.

Thoughts?

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Brent Handy

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Re: the 5.1 delima
« Reply #2 on: January 07, 2007, 07:22:14 pm »

I was not suggesting a mirror image front and back.  The recommendations from the Grammy Engineers Producers Wing suggested consistant treatment (absorption and diffusion) throughout.  This makes sense to me.

I don't have to have any windows.  I can use cameras and monitors as needed.  My ultimate goal would be to have the windows in the lower half to one quarter of the walls, on the left and right.  This would be possible by having the two iso's on a lower grade.  So I would be able to look down to the left or right, and look the "talen" in the face.  This would keep the glass reflections out of the equation, atleast at ear level.
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franman

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Re: the 5.1 delima
« Reply #3 on: January 08, 2007, 10:36:22 pm »

What jfrigo says is all spot on.. We try to handle reflection control with all 5 monitors in a good surround setup. I still tend to stick a little closer the ITU original 5.1 spec with regards to speaker placement, erring a little farther to the rear than 110deg off the centerline (as this is where P&EW is headed).

With regards to treatments, I agree that well dispersed broadband trapping is essential, just as in a good stereo room.. Considering the rear speakers with sppropriately placed diffusors is always an interesting design challenge, as we don't want to put them in the near field for the front speakers. If it's a mastering style setup, with free standing monitors out "in the room", than we can usually try to get some diffusors in the front/sides further forward than the line of the L-C-R monitors.. make sense??

Symmetry is equally important for a good sounding surround setup as it is in stereo, maybe more so...

One thing to remember is that regardless of the size of your room or monitoring circle, when monitoring in surround, there will always be really one seat that is in the sweet spot... With stereo, you can get reasonable stereo imaging across a wider-than-one-seat listening area. This is not to say that other participants can't enjoy a surround experience, but to make positional, balance or timbral decisions, one should really sit in the good seat!!.... some of my observations from doing many, many surround setups at this point.

Brent Handy wrote on Sun, 07 January 2007 19:22

I was not suggesting a mirror image front and back.  The recommendations from the Grammy Engineers Producers Wing suggested consistant treatment (absorption and diffusion) throughout.  This makes sense to me.

I don't have to have any windows.  I can use cameras and monitors as needed.  My ultimate goal would be to have the windows in the lower half to one quarter of the walls, on the left and right.  This would be possible by having the two iso's on a lower grade.  So I would be able to look down to the left or right, and look the "talen" in the face.  This would keep the glass reflections out of the equation, atleast at ear level.

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Brent Handy

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Re: the 5.1 delima
« Reply #4 on: January 09, 2007, 11:19:19 am »

Do you think that they will go as far as 130?
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jfrigo

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Re: the 5.1 delima
« Reply #5 on: January 09, 2007, 05:36:20 pm »

Brent Handy wrote on Tue, 09 January 2007 11:19

Do you think that they will go as far as 130?


My personal feeling is that 120 is good, but 130 may be pushing it a bit.
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franman

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Re: the 5.1 delima
« Reply #6 on: January 12, 2007, 10:57:19 pm »

sorry for the delay.. I also, would not go more than 120 deg of the centerline... I still like my setup rig and several great studios we've setup at 110 degrees... The time issue is at least as important as the angle on the surrounds... Get (ALL) your speakers equa-distant either physically, electronically (with delays) or a combination of both... This is what really makes the surround mixes (good ones) sound like a surround field as opposed to 5 speakers with a sub... Small discrepencies really mess things up in our experience..
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Yannick Willox

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Re: the 5.1 delima
« Reply #7 on: January 13, 2007, 05:48:57 am »

Is this crazy or is there actually an argument in favor of putting the surround speakers too close and then delaying them ?
This way, clients sitting too far to the back hear the surrounds a bit later as well, instead of really before the mains.
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Yannick Willox
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jfrigo

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Re: the 5.1 delima
« Reply #8 on: January 14, 2007, 01:28:34 am »

Yannick Willox wrote on Sat, 13 January 2007 05:48

Is this crazy or is there actually an argument in favor of putting the surround speakers too close and then delaying them ?
This way, clients sitting too far to the back hear the surrounds a bit later as well, instead of really before the mains.


Or putting the surrounds "too far" back and delaying the mains, so that everybody is within the surround field...  Personally I like to avoid any unnecessary processing on speakers (which in a perfect world is to say avoid all processing on speakers), but then I'm mostly coming from a mastering perspective. Why buy an $8,000 DAC to put it through a speaker with ADC, DAC, processing, amps, crossover, cabinet, and drivers that may cost less than just the converter? In a less critical multimedia application (authoring room, sound design suite etc.), delay to aid in functionality is a possibility. For any critical mix or mastering work, I'd prefer to stick with getting the physics right.
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Yannick Willox

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Re: the 5.1 delima
« Reply #9 on: January 14, 2007, 12:26:28 pm »

Yes, but when mastering inthebox (how many studio's do 5.1 analogue mastering ?) the necessary delay can be added with extra ADDA steps.
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Yannick Willox
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franman

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Re: the 5.1 delima
« Reply #10 on: February 14, 2007, 09:44:11 pm »

Look, just my opinion, but is a proper 5.1 (or 7.1) setup, there is really only ONE SEAT that can experience the surround properly, regardless of how large the room is or how big the speaker circle is....I've done it from 5ft to 11ft and it's always the same. In the larger setups, people who are even in the back of the room (behind the surrounds) still can enjoy the fact that there are multiple sources BUT only the person sitting in THE SEAT in any of these scenarios will experience the nuance of any well done surround mix IMHO...

Of course if you want to get into a more Dolby Digital, or Home theater type setup (NOT 5.1 ITU Music Surround).. then, you can have a more open area of enjoyable surround experience... AND this is much more like the typically home surround setup.. How many non professional rooms actually have a 5.1 music setup with 5 equal full range speakers??? Ummmm, let me see,,, NONE!!

How many people have some type of surround rig for the TV and movies... Ummmmm a WHOLE LOT MORE!!

Not making any suggestions here, just an observation... I don't know. I love surround, and it's been a great boom for our business... but I don't know ANY consumers who can enjoy any surround SACD or DVD-A material without going to a studio, or my office demo setup... I still love it though!
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