Film-Tech Forum ARCHIVE: Is 7.1 worth doing in this situation

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Posted by Frank Cox (Member # 6258) on 03-07-2019, 03:40 PM:

As I mentioned the other day, one of my amps died and I replaced it.

I'm just about to send the old one in for repair and was thinking that I will just put it in the corner when it gets back and now I have a spare amp if another one decides to quit.

But it just occurred to me that this amp might be all that I need for 7.1 sound and if so then would it be worth setting that up the next time the tech is here?

I don't know much about 7.1 sound so maybe I still don't have something important that I would need to do this, and if so then it's probably not worth the extra cost in such a small room.

My room is 25 feet by 60 feet, roughly, and I have L R C and LFE behind the screen and 3 Ls and 3 Rs speakers along the side walls.

My sound processor is a JSD-100.

For 7.1 sound would I need to add speakers to the rear wall of the room, or would the existing Ls and Rs speaker located the furthest back be all that's needed? The surround speakers are JBL-8320's so they aren't very big.

Would it be worth making this into a 7.1 auditorium since I'll ultimately have this spare amp laying around anyway? Would I have to buy anything else to make this work?

And ultimately, would it make a noticeable upgrade from 5.1 in such a small room?

Posted by Carsten Kurz (Member # 5396) on 03-07-2019, 04:03 PM:

I would think that the difference between 5.1 and 7.1 is actually more noticeable in a smaller room. However, you definitely need some more 8320 on the back wall. Yes, you could have 2 left/right for left/right surround, and the existing 3rd rear pair plus another pair on the back wall for the rear surrounds. That would be the minimal config.

60 feet long? That isn't a 'small' room!?

- Carsten

Posted by Steve Guttag (Member # 268) on 03-07-2019, 04:30 PM:

In truth, you should have surrounds on the back wall for a 5.1 system. Surrounds have always been a "horseshoe" configuration, even when they were monaural. So, if you put up back surrounds for your 5.1 system, then yes you are close to a 7.1 system in components BUT you will need at least 4 going across the back (and really with a 60-foot room, there should be more than 3 down each side) because in 7.1, the rear surrounds could be asked to play as loud as the side surrounds and with just one speaker to play the 60-foot theatre, it will likely not do well. So, unless you put in some honkin' speakers like the 9350 where you could get away with just 2, plan on having four back there.

When we did the digital conversions, if the customer was essentially wired for 7.1 and had the amplifier channels, we set them up as 7.1. If they were wired but merely lacked the amplifier, we gave them options (stay 5.1, add an amp for 7.1). Note, in Multiplexes, We could put a new 4-channel amp in one theatre and take the supplanted stereo amp and use it to make another theatre 7.1...so one amp purchase resulted in two screens of 7.1

All of our new screens are 7.1 unless the room is so odd it just wouldn't be worth the effort.

My guess is, this is likely more expense than you want to make. It likely isn't going to sell any more tickets and it is very movie dependent on if 7.1 makes a significant difference. It is an incremental improvement, not night and day.

Posted by Leo Enticknap (Member # 534) on 03-07-2019, 04:43 PM:

It's a relatively minor issue, but you may need to replace or upgrade the AES connection between your media block and the JSD-100. If you currently have a single RJ-45/ethernet wire going between the two, using the direct RJ45 input 1-8 on the JSD, and carrying 5.1 plus HI and VI, you will need to add a second for the back surrounds (channels 11 and 12). If you're using a DB25 to DB25, you should be OK if it's pin to pin. But if it's a bespoke cable that was made to cross different pinouts between the media block and the processor, you'll likely need a new one made up.

Posted by Frank Cox (Member # 6258) on 03-07-2019, 08:32 PM:

Sounds like yet another thing that's not worth paying for. I'll just put the spare amp in the corner when it gets back as I had originally intended.

Incidentally, I counted the surround speakers earlier tonight. There are four on each side, not three as I posted before. Funny how I see something every day of my life and still don't know how many there are....

Posted by Justin Hamaker (Member # 2165) on 03-07-2019, 09:46 PM:

Frank, it might be worth penciling the cost to at least see if you could make up the difference by increasing ticket sales by advertising "Now Featuring 7.1 Surround Sound". I know you're in a small and isolated market, but a small upgrade could help keep things fresh and give people a reason to come more often.

Posted by Leo Enticknap (Member # 534) on 03-07-2019, 10:57 PM:

Agreed with Justin - no harm in figuring out how much you're looking at before making a decision. From the info you give, and following Steve's best practice recommendation (four new 8320s for the back wall, with two paralleled from each channel on your spare amp), it looks like you'll be looking at:

- Four new 8320s

- Some new wiring runs (cable plus installation labor, if you're not doing that yourself)

- Upgrading the AES connection between your media block and processor; if you describe the existing connection to your tech, then if you need anything custom made, your tech can likely bring it with them ready to plug and play;

- Having a tech configure and tune the processor the next time (s)he makes a planned maintenance visit

The new speakers will be the biggest expense of the project. One phone call or email should get you a quote for those.

Posted by Marcel Birgelen (Member # 6801) on 03-08-2019, 05:26 AM:

I think 5.1 to 7.1 can be a worthwhile upgrade. In a small room, it's much more beneficial than moving from 7.1 to e.g. Atmos.

In a bigger room, especially one with under-powered surround speakers and/or amps, the benefit of 7.1 is pretty marginal.

But for a small room, the investments are relatively small, plus, with modern sound mixes relying heavier on surrounds, you can get a real benefit out of it.

It also has some marketing value. Maybe you can advertise that you upgraded your sound and ask your patrons if they heard any difference. [Wink]

Posted by Monte L Fullmer (Member # 2797) on 03-08-2019, 06:51 PM:

..plus, needing 7.1 Keys .... but, that's a minor thing.

Posted by Randy Stankey (Member # 64) on 03-08-2019, 08:16 PM:

Although I like the idea of upgrading to 7.1, I consider it a "Some Day" project. (Something we ought to do... Some day...)

Are you asking whether today is "Some Day?"

Can you afford it? Do you have bigger fish to fry?

If you can afford it, if you don't have anything more important to spend the money on and you don't have any other, more pressing, projects... what the hell?... "Some Day" might as well be today.

Or, at least, move it up from a "Some Day" project to a "Some Day Soon" project.

[Big Grin]