quote: Tim OBrien

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My thought was to run the 5.1 stream from the film reader and the discreet analog outputs from the BD player into a CP650. Is there any way to create a 2.1 downmix on the 650, or am I approaching this all wrong?

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quote: Carsten Kurz

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The easiest way to do this is probably to use a small analog mixer (Mackie, Yamaha, Behringer, etc.) connected to the CP650 analog multichannel out. That is, between CP650 and amps.

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Gee, why didn't someone else think of that?

Oh, wait..someone did:

quote: me

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1) Buy or rent a mixing console with a minimum of twelve input channels and use it to downmix to either 2 or 3 channels. Bonus: If you have more than 12 input channels (or don't use the subs or surrounds, whatever is best at the time) you can also run a few mics for P.A. use as well. For example: 16 in x 2 out line level for $150. That one does NOT have mic preamps built in. Or: 16 x 2 with mic preamps for $230.

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Amazing, ain't it?
 

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Posted by Carsten Kurz (Member # 5396) on 01-24-2013, 06:57 PM:
 
Sorry for wasting your time, Tony. I enjoyed it, though ;-)

Didn't know this forum is a being-first competition.

- Carsten
 

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Posted by Tony Bandiera Jr (Member # 2365) on 01-24-2013, 06:59 PM:
 
It's all good Carsten, I enjoyed it too.
 

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Posted by Tim OBrien (Member # 5605) on 01-24-2013, 08:11 PM:
 
Great minds think alike? Thanks for the tips, gentlemen.
 

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Posted by Manny Knowles (Member # 1171) on 01-24-2013, 09:40 PM:
 
Tony, I interpreted your solution as meaning he should go from each device's outputs into the mixer -- hence the 12 inputs?

Carsten's solution wouldn't require 12 inputs -- only six.

For a permanent solution, I've seen the Soundweb London BLU-16 Signal Processor used at d-cinema drive-ins. But this would be overkill for the OP's temporary situation. I'm only including it in case some future person searches this thread.
 

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Posted by Tim OBrien (Member # 5605) on 01-25-2013, 06:53 AM:
 
Manny, thanks for clarifying this as I was a bit confused. I know I need to do some homework as I've never used a mixer but the BSS product is a bit more intuitively appealing due to its flexibility. It seems I would need to combine the L and C outputs (from the 650) to become the left channel; and the R and C for the right channel. I can't see how this is possible on some of these mixers, but again, I'm in unfamiliar territory... And there's no such thing as overkill.
 

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Posted by Carsten Kurz (Member # 5396) on 01-25-2013, 07:08 AM:
 
Tim, get a manual or closeup photo for one of these cheap mixers, you will understand it very quickly.

Wether that mixer has 6 or 12 inputs - it doesn't matter as long as it fits your need and is available. These tiny things are sold in huge masses to musicians for home studio, you get great value for very little money.

Basically, you e.g. feed L to channel1, center to channel2, right to channel3.

The mixer mixes these into a stereo channel, which can be controlled by a master fader. The output from the master fader goes to your stereo amp and controls presentation volume.

Now, every input channel has a PAN or balance pot where you can decide, which amount of this input goes to the L or R output of the stereo master output.

For L, you have it set all counter clockwise to L only, for center you would have it 'center' for equal amounts to L and R out, for R fully clockwise to R output only.

That's it.

The input channels and sometimes also output channels usually have a simple equalizer or low/mid/high tone controls, so you can do slight(!) adjustments to the sound balance as well.

With the separate input faders, you can as well control the amount of center/dialog volume very easily to your needs.

And as I said, most mixers will probably also allow a separate feed out of the center channel to a separate center amp/speaker so you have a better solution than the phantom center.

The actual input layout of these mixers vary a little bit - some have 1-6 mono mic channels, + some stereo channels, but it actually doesn't matter as every mic channel will also accept line signals from the CP650. Doesn't matter wether you start with channel1 or channel 7.

Best is probably to get a mixer with at least 3 identical mono(mic) input channels, as it makes setup easier.

Wether it actually has faders or volume knobs on the channels is not important for this application.

http://www.bhphotovideo.com/c/product/421989-REG/Behringer_1202_XENYX_1202_12.html

- Carsten
 

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Posted by Manny Knowles (Member # 1171) on 01-25-2013, 09:48 AM:
 
^^ I'll second this.

But why not include Ls, Rs and LFE and mix those in too?
 

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Posted by Louis Bornwasser (Member # 3063) on 01-25-2013, 10:51 AM:
 
Manny: in fact you HAVE to. On the discrete digital mix, there is no bleed, so any effect not mixed in is completely lost. This includes the subs. Louis
 

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Posted by Scott Norwood (Member # 30) on 01-25-2013, 10:54 AM:
 
But he's using a separate subwoofer. Assuming that the CP650 is set to the correct crossover point, he should be able to feed that signal directly to the power amplifier for his subwoofer.
 

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Posted by Manny Knowles (Member # 1171) on 01-25-2013, 01:15 PM:
 
I'd urge running LFE through the mixer -- the overall mix of the main channels will be affected, so I'd want an easy way to bring the LFE into balance with this "new" mix -- and to have its level follow any level changes made during show.

Oh, and to get dedicated center and subwoofer outputs, you'll need a mixer with 4 outputs (L/C/R/LFE). Most likely, the smallest compatible configuration for a mixer will be 8in/4out. You could use leftover inputs for mic and/or non-sync music.
 

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Posted by Tim OBrien (Member # 5605) on 01-25-2013, 04:41 PM:
 
Ahh, the light is on now! All of this makes good sense. I had planned to run the sub straight through but Manny's suggestion will provide for a convenient control point. An 8-4 mixer will do nicely and provide and extra output for a possible center speaker. Thanks, everyone, for the education!
 

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Posted by Carsten Kurz (Member # 5396) on 01-25-2013, 06:35 PM:
 
Actual '8to4 Mixers' are a rare species. You will usually find it among to more expensive xto4to2 or xto8to2 mixers with so called subgroups.

However, some smaller mixers have a feature called ALT 3-4.

These have a switch for each channel which can be used to route it to either the master fader/stereo out, OR an alternative 3/4 output.

One example is the Mackie 802-VLZ3 at around 200US$. You can also get it very cheap second hand at ebay:

http://www.ebay.com/itm/Mackie-802-VLZ3-8-channel-Stereo-mixer-/271143575422?pt=US_Live_Studio_Mixers&hash=item3f216 a9f7e&_uhb=1

Another option would be the Behringer 1204 in either the plain (second hand), FX or USB variant.

It does not have enough mono input channels for a 5.1 mixdown, but you can easily use two stereo channels for L/R and Ls/Rs, and the mono inputs for C and LFE.

So L/R and Ls/Rs going to the Master L/R output, while C going to ALT-3 and LFE going to ALT-4. 2 Stereo amps and you're set.

If you don't have an actual subwoofer, but your L/R speakers have enough bottom, you can just route LFE from the CP650 to both L/R, not using the ALT 3-4 switch for LFE.

- Carsten
 

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Posted by Steve Guttag (Member # 268) on 01-25-2013, 07:50 PM:
 
Here is something that will do the mixdown in 1U of space and is made in USA

http://www.rane.com/sm26s.html
 

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Posted by Carsten Kurz (Member # 5396) on 01-25-2013, 08:44 PM:
 
Costs two to three times as much as the Mackie 802, with the missing functionality of separate C/LFE routing, tone control, headphone monitoring, Mic In, VU meters.

- Carsten
 

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Posted by Steve Guttag (Member # 268) on 01-26-2013, 07:05 AM:
 
To each their own, I guess. Note, the routing capabilities of the SM26 are better than you are giving it credit for, between the master in, mono-ins, master out, direct outs and the mode headers, the thing can be set to be in just about any configuration needed...including whatever you want to do with the center/LFE. It also all fits in 1U of rack space.
 

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Posted by Antti Nayha (Member # 4980) on 08-06-2013, 12:26 PM:
 
So what's the Film-Tech Experts Board's consensus on the best way of downmixing 4.0 matrixed audio (Dolby A/SR or LtRt video source) to a 2.0 or a 3.0 outdoor setup?

The three front channels are obvious and were already discussed, but should the mono surround output go:
1) to C channel only (surely not?)
2) to L and R channels equally
3) to L, C and R channels equally
4) nowhere?

I would lean towards option 2, but it'd be nice to hear your opinions. Also, would you mix the surround channel to the front speaker(s) at full volume, or at let's say 50%?
 

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Posted by Carsten Kurz (Member # 5396) on 08-07-2013, 06:20 PM:
 
I guess I would choose L+R.

I - Carsten
 

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Posted by Manny Knowles (Member # 1171) on 08-07-2013, 09:24 PM:
 
Option 2
 

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Posted by Scott Norwood (Member # 30) on 08-08-2013, 07:42 AM:
 
I have done a number of screenings in temporary setups with L/C/R and no surrounds. In all cases, the surround channel information was just discarded completely. It sounded fine. I would be a bit wary of doing this with digital sound, where there is no leakage between the front channels and the surrounds, but it works fine for analog matrix decoding (although, admittedly, I am talking about art-house-y stuff...not Star Wars).
 

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Posted by Gordon McLeod (Member # 33) on 08-09-2013, 10:58 AM:
 
We built a protype drivein interface and what we did was to the LT RT outputs we matrixed as follows
L to +LT
C to +.707LT +.707RT
R to +RT
LS to +.707LT -.707RT
RS to +.707LT -.707RT
SW to .707LT .707RT
Then we put a limiter on it and also provided 2 mono outputs for field speakers and one for AM
If i can ever find some time i will attempt to finish it off
 

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