Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[mojave]

I am building some line source speakers this fall/winter (and maybe spring). The volume of line source speakers decreases by 3 dB per doubling of distance vs 6 dB/doubling of distance like point source speakers. I don't plan to initially have a line source center speaker so I could use my current point source speaker. This means that it will be hard have the center channel volume constant with the mains as one moves to different seating positions. The line source mains will also be much more dynamic than my current center speaker.

A solution is to use a phantom center channel in which the center channel is split to the left and right channels. I also need this for my 4.1 setup in my office.

Rather than changing output format, I thought maybe in Room Correction under the center speaker we could check a box for a phantom center. MC could perform the correct gain adjustments just like it does for bass management. I can't decide if this step should be done before or after bass management.

I currently use FFDShow to handle this in my office setup. However, I would like to have MC handle any DSP needs. You would also probably preserve energy better by keeping it to MC's Room Correction DSP.

[Matt]

I am building some line source speakers this fall/winter (and maybe spring).

Fun!  Just don't tell jmone, or you'll end up on the same list as me because I want to build a custom subwoofer someday.

A solution is to use a phantom center channel in which the center channel is split to the left and right channels. I also need this for my 4.1 setup in my office.

So how many channels are you actually outputting: 4, 6, or 8?

Most computer consumer-level desk speaker systems I've seen have two or four inputs and do their own bass management for the 0.1.

Rather than changing output format, I thought maybe in Room Correction under the center speaker we could check a box for a phantom center. MC could perform the correct gain adjustments just like it does for bass management. I can't decide if this step should be done before or after bass management.

It would probably be fine in either place, although a checkbox below 'For stereo sources, only mix to 2.1' makes sense to me.  Bass management would just fall into line as the center channel would be marked as silent (just like happens to the rears, etc. with 2.1 mixing).

[mojave]

So how many channels are you actually outputting: 4, 6, or 8?

At my office I input 6 channels and output 5. At home I use 8 channels, but I might want to input 8 and output 7.

Most computer consumer-level desk speaker systems I've seen have two or four inputs and do their own bass management for the 0.1.

If I was consumer-level, I would be using Windows Media Player.  I have four bookshelf speakers, two 2-channel amplifiers, and a Hsu subwoofer in my office.

It would probably be fine in either place, although a checkbox below 'For stereo sources, only mix to 2.1' makes sense to me.  Bass management would just fall into line as the center channel would be marked as silent (just like happens to the rears, etc. with 2.1 mixing).

That would be fine, although it should work even if someone isn't using JRSS. I always like an option that lets me compare. If it was in Room Correction, I could (or others) check/uncheck the box and compare a phantom center channel to my current center speaker. I really like this ability with Bass Management. It helps one easily test various theories. For example, I might initially like the phantom center setup better because of the better dynamics of the mains. Then I will start thinking, "What if I raise the crossover frequency on the center speaker. Now it has less mid-bass to play and it might be more dynamic sounding." So, I'll change the crossover frequency and compare back and forth to a phantom center. Then I'll think, "Maybe I need to increase the volume slightly on the center speaker. That might make it blend better." So I'll test that and compare.

I found this quote interesting in this Stereophile article:

"For audiophiles who love multichannel music, the center-channel speaker is a problem second only, perhaps, to that of bass management."

[Alex B]

A typical home theater receiver can be configured to work without a center speaker. The receiver will output C through L & R if it is set to not use C. AFAIK, this a standard feature in most HT receivers.

MC should be able to do the same when it replaces a HT receiver.

[)p(]

A typical home theater receiver can be configured to work without a center speaker. The receiver will output C through L & R if it is set to not use C. AFAIK, this a standard feature in most HT receivers.

I have a 4.1 setup and use ac3filter to create the virtual center. I like the dialog a little louder...most receivers wont let you set the volume of the virtual center but with ac3filter you can. If a virtual center option is added to jriver's room correction it would be great if we can set its relative level too.

[mojave]

If a virtual center option is added to jriver's room correction it would be great if we can set its relative level too.

If this option was added to the center channel in Room Correction, then maybe the gain settings could be used to fine tune the center channel's gain.

I like to watch football without the center channel sometimes. This way you don't have to listen to the announcers, but still get all the crowd noise. If the phantom center option is in Room Correction, it would be easy to mute the phantom center, too.

[mojave]

I found out that with ffdshow's audio decoder, you have to leave the matrix at 5.1 or 7.1. Then you add the center channel to both the left and right channels (I used .707). If you try to use the quadro setup, then the channels all slide down when the center channel is eliminated. This puts the LFE in the center channel and it doesn't mix correctly with the redirected bass from the other channels when using Bass Management. Why does everything have to be so complicated? 

I did some switching back and forth between phantom and actual center speaker the other night. Due to the some of the drawbacks of a horizontally placed center speaker, I would have to say that I actually like the phantom center arrangement better. I have removed the center speaker now at home and have watched some movies without it. I sure helps with placing a projector screen when the center isn't in the way.

[)p(]

I did some switching back and forth between phantom and actual center speaker the other night. Due to the some of the drawbacks of a horizontally placed center speaker, I would have to say that I actually like the phantom center arrangement better. I have removed the center speaker now at home and have watched some movies without it. I sure helps with placing a projector screen when the center isn't in the way.

If you can sit close to the center axis in most cases I also prefer a virtual center. That is why we know use 4.1 in our projector room.

[mojave]

I played around with ffdshow's settings again last night. I found that if I want to use JRSS to go from 5.1 to 7.1, I need to set the "Output speakers configuration" to 3/0/2 - 5 channels and check the LFE box. Then I have to use "Custom Matrix" with Side Left, Side Right, and Rear Center all set to 0. Back left and back right need to be set to 1 with the corresponding back left and back right. This actually routes the surrounds to my side left & right (channels 5 & 6) and doesn't send channels 7 & 8 so that JRSS can create them.

[mojave]

I found out that when ffdshow decodes the FLAC, it reduces the bit rate from 24 bit to 16 bit. jmone confirmed this on the ffdshow development thread at doom9. In order to maintain the 24 bit output, I need to use madflac as my decoder. Madflac doesn't offer any mixer options for a phantom center. Therefore, for best audio quality, a phantom center option in MC would be nice.

[Matt]

Coming in build 130 and later:
NEW: Added DSP Studio > Output Format > Move center to side speakers option for configurations with no center speaker.

[mojave]

I tried this out this morning and it seems to be working great. Thanks.

[mojave]

I've used this now on several movies and haven't noticed any problems. Yesterday I listened to a DVD-Audio that I had ripped. This is a 5.1 mix that is 96 kHZ/24 bits. I started getting a headache within a few minutes of listening. As soon as I turned off the phantom center, I was okay. I again activated the phantom center and the headache returned. This used to happen to me all the time when I used the M-Audio Revolution 7.1 and SRS Circle Surround Sound upmixing. I could tell within a few minutes that I had left SRS on (I used in on for movies and off for music). Certain Dolby ProLogic II settings produce the same result. Its not really an issue, but I wonder why it happens.

More importantly, I realized that the label says, "Move center to side speakers." I think most consider the side speakers to be the side surrounds. Saying, "Move center to mains" or "Move center to front L/R" is more keeping with the way most refer to their speakers.