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Multi-Channel Audio - is there a magic number?

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Multi-Channel Audio - is there a magic number?

Postby magnaton » Fri Sep 09, 2016 10:11 am

One of the nice accidental benefits I've received from my on going efforts into Hauptwerk is the incremental build up of my rig: single keyboard, 2nd keyboard, keydesk, MIDI AGO pedal conversion, audio interface, Launchpad, swell pedal MIDI conversion (x2), multi-channel audio, surround sound & sample sets, etc. This has kept the fire going so to speak which nurtures my mechanical & DIY side. So the my passion continues verses having had a MIDI ready console, HW Advanced, and multi-channel audio all on day one.

For a while it seems I was adding a pair of (identical) studio monitors every 2 months courtesy of Craig's List. I have maxed out my MOTU interface with 12 channels. Ok, to be honest, I do have my eye on the headphone jack to accommodate 2 more channels! I currently have 2 full range speakers with 15" woofers, an array of 8 studio monitors (4 stereo pairs), and a pair of passive studio monitors for surround sound or a few 'distant' stops for fun. I'm extremely happy with the sound. :D

Is there anyone here on the forum that has added speaker pairs over time until they reached that magic number? Was there a noticeable difference/improvement when the extra pairs were being added say from 10 to 12? I guess the deeper question is, when do you start to get into diminishing returns with regards to the number of speakers? Of course in dealing with pipe organ ranks and notes being played, there probably is never a diminishing return for speaker count :lol:

A quick side note - The Paramount Organ Works "Multi-Channel routing guide" states that using the "Cyclic within octaves, octaves and ranks cycled" algorithm, 4 stereo pairs will perform the sames as 16. In my current state of SAS (Speaker Acquisition Syndrome) I'm not believing that too much.

Comments?

Danny B.
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Re: Multi-Channel Audio - is there a magic number?

Postby engrssc » Fri Sep 09, 2016 11:59 am

The hypothetical answer is dependent on who you ask because the basis is opinions and opinions can't be quantified. Ask 5 people and you are apt to get many more than 5 answers. Some being it all depends . .

If realism is the goal, you have to factor in the acoustics of the space, size, and shape of the space for starters. Then the audio system(s) being involved. You can take a given (total) setup from one location and install this same setup in a completely different environment and get totally different results. The same is true with real pipes. Some folks have done an acoustic treatment of a given space. Haven't heard of total fulfillment doing that either. Bang and buck wise, again, has a direct bearing.

Altho addressing a different topic, there are some interesting observations here.

http://forum.hauptwerk.com/viewtopic.php?f=1&t=14968&p=111525&hilit=Leo#p111525
and further other comments of that post.

Rgds,
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Re: Multi-Channel Audio - is there a magic number?

Postby jkinkennon » Fri Sep 09, 2016 12:15 pm

I would suggest that to achieve a significant improvement you would be looking at going from 10 channels to 20 rather than to 12. Just my thoughts at the moment, but it seems that every doubling of the number of channels would produce a similar effect. I'm running three pairs (6 speakers) for the front channels and will get to hear exactly double that at an upcoming installation. I'm expecting to hear some improvement plus the fact that the individual speakers will be running at slightly lower levels which may be an audible improvement in itself. Multiple channels need some space between speakers to be effective. I may resurrect my old demo of this effect though when I first mentioned this a couple of years ago I got the impression that no one actually tried the experiment for themselves. It involved listening to beats between two stereo speakers playing a major third and hearing the beats decrease as the speakers were moved apart.

Larger registrations may need more channels than small registrations to achieve the same clarity. Curious what others are finding as well.
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Re: Multi-Channel Audio - is there a magic number?

Postby josq » Fri Sep 09, 2016 12:16 pm

My understanding is that you have to find a balance between avoiding intermodular distortion (more speakers is better) and reproducing the proper stereo image (a single pair is ideal). Therefore if you play wet sets you better get a single pair with maximum quality (two pairs for surround) and as much speakers as possible for dry sets. If I am wrong on this one I am happy to be corrected.
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Re: Multi-Channel Audio - is there a magic number?

Postby organtechnology » Fri Sep 09, 2016 12:29 pm

Hi Danny,

Since the purpose of the cycling algorithms is clarity (minimal distortion) the statement about 4 pairs and 16 pairs can probably be proven mathmatically but not from the subjective perception of a single person. Is 16 pairs better than 4 pairs? Certainly but how much better and along what axis?

The opinion of those more learned than I, that have been on the forum, suggests that if the recordings were made as 'close stereo' or binaural, the best audio is from really good headphones in stereo. Perhaps there is a subwoofer or 'butt kicker' to provide tactile feel of the low frequencies.

But when you switch to speakers, the game changes. A speaker array should be good enough to reproduce the pipe sounds as originally recorded in the new venue. It has been suggested that the ultimate is one speaker per pipe or one pipe per speaker, however you want to look at it. But that is not possible on an organ with more than 512 pipes because that is the channel limit of Hauptwerk.

So where does that leave us? It is our collective experience that 2 speakers in stereo are minimal with a subwoofer to cover 16-100 Hz spectrum. Increasing to 6-8 channels with one speaker per channel and a subwoofer provides improvement in sound and generally fills a small venue such as a home. Going to 12 channels does increase the clarity as well as reducing the load on the associated amplifiers but not as much as going from 2 to 6 channels/speakers.

When talking about a large venue such as a church or auditorium the problem becomes much more complex and for true realism it may be necessary to have a sound system which can produce an SPL in the volume equivalent to the organ pipes. That is a lot of speakers!

So to condense to what I think you want to know, 3-4 identical stereo pairs and subwoofer(s) will get you where you want to be. Add Reaper and an impulse response based convolution reverb and you will be a happy camper. Sell your extra speakers and buy a better ASIO sound module.
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Re: Multi-Channel Audio - is there a magic number?

Postby engrssc » Fri Sep 09, 2016 12:54 pm

Well said, Thomas. Good, realistic approach. However, some folks are impressed more with a large array and find fault with the smaller grouping. Identical, good quality speakers are a must IMHO. Esp true when using cycling algorithms.

Then there is the variation of the sample sets. In our church installation, I found limiting to only a single, well voiced for the space, sample set, has been the better approach. For home, that's a different story.

Rgds,
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Re: Multi-Channel Audio - is there a magic number?

Postby mdyde » Fri Sep 09, 2016 1:08 pm

magnaton wrote:A quick side note - The Paramount Organ Works "Multi-Channel routing guide" states that using the "Cyclic within octaves, octaves and ranks cycled" algorithm, 4 stereo pairs will perform the sames as 16. In my current state of SAS (Speaker Acquisition Syndrome) I'm not believing that too much.


Hello Danny,

There would be nothing to be gained by adding additional speaker pairs into a given audio output group if that group already had 12 pairs in it (i.e. one pair for each note in the octave). However, 12 pairs in a group would in general distribute the pipework more considerably more widely (with the associated benefits that brings) than 4 four pairs in a group. If you had more than 12 pairs of speakers then it would make sense to add the additional ones into further, separate output groups (as opposed to adding them all into the default group).
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Martin.

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Re: Multi-Channel Audio - is there a magic number?

Postby TheOrganDoc » Fri Sep 09, 2016 1:20 pm

I would like to Hear from someone that has installed all their left side speakers in Parallel ,
and all of their Right speakers in Parallel , In Just two channel stereo ,Just to determine if the
difference is only spacial
. :roll:
Living in an apartment and having to use my Headphones 95% of the time, does not qualify me as an expert on this subject !
(A good External Multi-channel sound board,
with a group of High quality self powered studio monitors, spread out and a Sub,
should be all anyone needs in a home ! ) :D
Mel..............TheOrganDoc...............
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Re: Multi-Channel Audio - is there a magic number?

Postby 1961TC4ME » Fri Sep 09, 2016 1:48 pm

TheOrganDoc wrote:I would like to Hear from someone that has installed all their left side speakers in Parallel ,
and all of their Right speakers in Parallel , In Just two channel stereo ,Just to determine if the
difference is only spacial
. :roll:
Living in an apartment and having to use my Headphones 95% of the time, does not qualify me as an expert on this subject !
(A good External Multi-channel sound board,
with a group of High quality self powered studio monitors, spread out and a Sub,
should be all anyone needs in a home ! ) :D


Hi Mel,

As part of my extensive testing earlier, I did indeed try what you ask about. I'll just say that I was first thinking it may sound pretty decent but I came away not very impressed at all with the end results. The issue in achieving best sound lies in gaining clarity without introducing harshness.

I'm sure a good number of the forum members here have seen this post in the past concerning my many attempts / experiments in various audio routing to improve realism, but in case some haven't here it is.....

viewtopic.php?f=17&t=14769

I'm also of the opinion 8 - 12 channels for home use is very adequate and will give very satisfactory results, anything above and beyond that then I guess as they say and I'd also say, "It depends." :lol:

Marc
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Re: Multi-Channel Audio - is there a magic number?

Postby dhm » Fri Sep 09, 2016 2:16 pm

One question hasn't yet been asked, but it's necessary in order to answer Danny's original question.
Presumably you are running all ranks through the same audio output group, shared among all the speakers? Or are you allocating different manuals/ranks/types of stops to different stereo pairs?
Most responses so far seem to assume the former.
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Re: Multi-Channel Audio - is there a magic number?

Postby engrssc » Fri Sep 09, 2016 2:59 pm

And 4 or 6 pairs has different results than 8 or 12 individual spkrs.

Marc's extensive testing a while back goes a long way to answer the above and other such questions for a home installation.

Rgds,
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Re: Multi-Channel Audio - is there a magic number?

Postby magnaton » Fri Sep 09, 2016 3:53 pm

Thanks for the great detailed responses.

dhm wrote:One question hasn't yet been asked, but it's necessary in order to answer Danny's original question.
Presumably you are running all ranks through the same audio output group, shared among all the speakers? Or are you allocating different manuals/ranks/types of stops to different stereo pairs?


After some experimentation over the last few weeks I use 2 separate configurations, thanks to the Alt Config shortcuts!
For Classical samples, stops are divvied across the channels by like sounding ranks (celeste in a different channel from its unison counterpart) as proposed by Marc (1961TC4ME) in his previous multi-channel titled threads. The clarity really opened with this design but wasn't too strict as I evened out some work to the various channels under utilized (i.e. Mixtures to the full range speaker set).
For Theatre organ its a single group for all the studio monitor pairs using the "Cyclic within octaves, octaves and ranks cycled" algorithm. Being able to hear solo stops or tuned percussions move across the speakers is a real thrill. With a TO's inherent large unification design plus the recommendation from Paramount themselves, this setup works very well. Again I'm very happy with both these setups.

jkinkennon wrote:Just my thoughts at the moment, but it seems that every doubling of the number of channels would produce a similar effect. I'm running three pairs (6 speakers) for the front channels and will get to hear exactly double that at an upcoming installation. I'm expecting to hear some improvement plus the fact that the individual speakers will be running at slightly lower levels which may be an audible improvement in itself.


I tend to agree. I noticed a considerable improvement when going from 4 to 8 channels on my Studio Monitor group. I have plans to add another 8 channels (4 stereo pairs) before calling it done. By all means, keep us posted on this new installation and the difference when you double the audio.

organtechnology wrote:Sell your extra speakers and buy a better ASIO sound module.

Hummmmm, sounds like a topic for a new thread. I currently have a MOTU Ultralite MK3 Hybrid. Maybe this is considered a semi-pro interface? I know this unit is used by several others here on the HW Forum. From my research, the next level up in audio interfaces are in the 1K to 3K price range. Would the sound be that much better using one of those? For my audio interface upgrade I'm seriously considering the MOTU 24AO model.
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Re: Multi-Channel Audio - is there a magic number?

Postby engrssc » Fri Sep 09, 2016 4:38 pm

Then there's the RME-UFX that I believe Martin and Brett use.

Rgds,
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Re: Multi-Channel Audio - is there a magic number?

Postby Eric Sagmuller » Fri Sep 09, 2016 5:58 pm

I have a real problem where the more stops are pulled the more harsh it sounds to me. Also the fast beats from higher pitched stops and somehow wild tuning fluctuations. I'm probably exaggerating here, but this leads me to think more speakers in a group are better, at least up to 12 pairs as Martin says. And I use all wet sets.

Some time ago I separated my pedal stops from the manuals and have them going to their own subs and studio monitors. I especially have a problem when adding reed stops and found this helps some, but not as much as I had hoped.

When listening to HW recordings, I actually find myself turning the volume down and not even listening at times to a piece once it gets many stop pulled. For whatever reason live organ recordings don't phase me nearly as much as a rule. More often than not I find myself playing with only several stops enjoying their clarity and beauty. I've also found some sample sets seem to keep more clarity when adding stops, than others of similar acoustics.

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Re: Multi-Channel Audio - is there a magic number?

Postby toplayer2 » Sat Sep 10, 2016 9:51 am

There have been some good comments shared on this topic. Dr. Colin Pykett has an intereating article on his website:

http://www.pykett.org.uk/EndOfPipeOrgan.htm

In essence, the most important goals are to reduce indermodulation distortion and "signal mixing". These are the primary culprits that contribute to the harshness with large registrations that Eric describes.

Hauptwerk assigns notes to speakers based on this algorithm:

speaker_num = (note_in_oct + oct_num + rank_seq_num) mod num_speakers

The rank_seq_num, or RankID, is determined for each rank by the sample set developer. At Paramount we have planned this out in a scheme we call "Optimized ORC" such that ranks with very similar spectral content, for example a string unison and celeste, are guaranteed to be routed to different speakers. The Paramount 450 is optimized for 2, 4, or 6 stereo pairs. The Paramount 341 also includes 3 pairs.

Originally, I used 6 pairs of Mackie HR824 monitors but have now scaled down to three. Six sounded better, but not enough for me to justify the additional space. For dry sets, adding a nice sounding reverb is very important. Based on recommendations from friends, I am now using Reaper with East West Quantum Leap Spaces. For wet sets, I much prefer headphones.

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