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New speaker DSP in Media Center 14.0.127 [Room Correction]

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mojave:

--- Quote from: Matt on February 25, 2010, 10:31:25 am ---Thanks for the details mojave.

How are you wiring your 2.1 and 4.1 systems?  Normally the subwoofer isn't on its own line coming out of the soundcard in 2 and 4 speaker setups.  We haven't focused on 2.1 and 4.1 wiring configurations.

The subwoofer is on its own line for 5.1 and 7.1, and in my opinion, Media Center does a really nice job in these cases.  I especially like the Subclarity filter to remove drones and leave thumps on the subwoofer line.  I'm not sure what more we would do here except for your idea to filter bass off other speakers (although I personally prefer letting the speaker's natural rolloff work)

--- End quote ---
The subwoofer is always on its own line coming out of the soundcard if you have more than a two channel soundcard (or multi-channel output on the motherboard). You should be able to output whatever combination of speakers you want using the maximum channels on your soundcards. I have 7.1 soundcards in each of my systems. My subwoofer output on the soundcard obviously goes to the subwoofer. My other channels go directly to my 7 channel amplifier or to two 2-channel amplifiers (at the office). There are no wiring changes. If I use AC3 Filter and select 2/0+SW or 2/2+SW and select bass redirection with a crossover in its mixer then the bass is routed to the subwoofer channel. It is just like using a receiver with its crossover settings and large and small settings for the speakers. I can do this with AC3 Filter, ffdshow, Theatertek with advanced audio, WINDVD, PowerDVD, ArcSoft TotalMedia Theatre or any other software player with built in DD or DTS decoders. I can also do it with M-Audio, Creative, and Asus drivers although I could only do 4.1 with the M-Audio drivers.

Here is a quote from Arcsoft:

--- Quote ---Having obtained DTS-HD certification, ArcSoft TotalMedia Theatre now not only has the ability to decode the lossless DTS-HD Master Audio – a “bit-for-bit” identical recreation of the original studio master sound track, DTS-HD High Resolution Audio, etc.; it also provides end users the ability to control and direct bass signals to the most appropriate speakers or subwoofer(s) in the system, a process known as Bass Management System, an important recognition from DTS. Also noteworthy are “Speaker Remapping” which offers support for various speaker playback configurations
--- End quote ---

There are two sources for the bass. One is the LFE track on the Blu-ray or DVD. This is all that is sent to your subwoofer if you don't use bass management. The other is redirected bass from the other 7 channels. The bass for the other 7 channels on DVD or Blu-ray can be as lower than 20Hz and with peaks up to 105 dB (I think the lowest bass I've seen in the 7 channels is about 8 Hz). It is very rare that the speakers (either mains, center or surrounds) can output the same dynamics and low frequency range as a subwoofer. I would bet that 99% of all home theater calibrators would use a crossover even on the mains for movies. My mains are towers and while their -3dB point is 40 Hz my dual 15" subwoofers do much better from 100 Hz and down.

What exactly does the Subclarity filter do? I have never had thumps or anything else on the LFE channel or on redirected bass to the subwoofer that wasn't intentional. If it is mastered properly why would there be anomalies? Are you sure you aren't just filtering out frequencies that your sub can't play properly?

Pjotr:
Hi Matt,

Just my 2 cents.

I like the idea of a convolver for room correction, but to my experience so far with the free VST  “Convolver” plug-in  and REW it is only useful below the Schroeder frequency and as such only for subwoofers.

For high-end audio a 2.1 stereo system with dedicated bass-management would be already a big advantage. I really like the idea of taming room modes in the bass region which is pretty difficult in normal living rooms. For bass-management that requires multi position impulse measurements for single/multi-sub set ups. But not only that, a CB sub can gain a lot from a good shelving filter that is a neat bi-quad IIR filter, to shift the Qb and Fb of the sub neatly instead of the wacky boosting filters usually found inside subs.

REW is free and already there, probably that can serve as a measuring front-end to obtain the FIR correction files for a convolver implementation in MC?

One problem with the free VST convolver plug-in I encountered is that the sample rate of filter file must be the same as the music processed. Otherwise it gives really weird results. This must be proper handled when we deal with various sample rates of the music as with MC.

gappie:
Mr. Mojave, i enjoy your posts a lot. very informative and even i understand them.  8)
and it all make sence. and maybe it would make it even easier for my unothodox setup..

so thanks
 :)
gab

mojave:
Thanks, Gappie.

Now that I can use a 2.1 mode with MC, I enabled the Room Correction DSP and set the distances for speakers and sub. It was mentioned earlier that the volume levels would be changed based on distances. I confirmed that when I change the subwoofer distance setting, the volume level also changes.

When setting the correct phase between a subwoofer and the mains, the distance setting is adjusted until the volume at the crossover frequency is the loudest. I have found that this distance is typically closer than the actual measured distance, but it varies by subwoofer model. If the volume keeps changing as one adjusts the distance setting, how are we supposed to use measuring software or an SPL Meter to find when the phase is correct? It could be argued that the change in volume will be inconsequential, but if I would rather not have to worry about it. I don't mind the volume changes for all other channels but I think they are rather useless. One still has to measure the SPL and set the right volume for each channel. Can I at least get the sub level to remain constant? Thanks. 8)

Pjotr:
My wish too ;) Level changes for a sub are of no use. For 2.1 stereo I don’t see any use for level changes for the L and R channels too.

What does the distance setting actually do? Apart from the level changes, does it simply adjust the delay and what is the reference then, just the seating position? Maybe for a 2.1 system a delay setting for each channel in just ms can be a handy option. Only for the sub channel, or only for the set of LR channels is a need for delay then.

Also I like the option to have a customable HP filter for the LR satellites. This can give better integration with the sub. But if once extensive true bass management becomes reality in MC all will change anyway I suppose.

Oh, and please can you make the distance setting also available in metric units. Rulers in feet are rare in Europe… (except for GB :D ).

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