Hi,
I have been wondering about this thing.
In a normal 2 channel stereo, mono sound comes from a phantom center. However compared to a mono speaker it doesn't sound the same. So in some sense sometimes mono might sound a bit more realistic especially if the music source is essentially mono. Example a guitar, piano or cello. Tilting the speaker inwards tend to improve on the imaging giving it a more robust phantom but still not as good as a mono speaker.
My purpose is not to do a DSP or mess around the signal chain but just to improve on the presence of the phantom center to be as close as possible as a mono speaker in front. I am wondering if an additional speaker connected to the left and an additional speaker connected to the right placed right in the center together, so acoustically mixed, at much lower volume, say -10dB compared to the side will produce a more robust phantom center?
Has anybody tried such an experiment? Or come across some work on it.
Thanks in advance.
Oon
I have been wondering about this thing.
In a normal 2 channel stereo, mono sound comes from a phantom center. However compared to a mono speaker it doesn't sound the same. So in some sense sometimes mono might sound a bit more realistic especially if the music source is essentially mono. Example a guitar, piano or cello. Tilting the speaker inwards tend to improve on the imaging giving it a more robust phantom but still not as good as a mono speaker.
My purpose is not to do a DSP or mess around the signal chain but just to improve on the presence of the phantom center to be as close as possible as a mono speaker in front. I am wondering if an additional speaker connected to the left and an additional speaker connected to the right placed right in the center together, so acoustically mixed, at much lower volume, say -10dB compared to the side will produce a more robust phantom center?
Has anybody tried such an experiment? Or come across some work on it.
Thanks in advance.
Oon
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like your idea I seem to remember reading about a company doing a second set of stereo speakers infront of the mains and pointing at 90degrees but think this included some dsp or similar . why don't you try it and see what happens ?
You nailed the insight - your observation is spot on. It becomes quite obvious if you consider the direction of the sound fields involved - one coming from dead front center (as in reality) vs. two coming from say 30 deg (stereo). There's a few different ways to go about it. I think you should try your idea. I think it's called "matrix decoding" if you would like to search on the concept.
Perhaps gurgle: "center channel for stereo recording matrix".
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Perhaps gurgle: "center channel for stereo recording matrix".
//
I've done similar things in car audio. If you carefully set the volume and also limit the center's high frequency content, you can fill in the center pretty well without messing up the rest. You do sacrifice a bit of soundstage width, but this is only obvious with immediate comparison of one condition vs the other.
That doesn't mean that other methods can't do it better, just that you can probably get acceptable results doing it the way you're describing.
Sounds like a good idea, in HT is this very common (and even more channels) and the HT market is interesting for gear sellers, because you need a lot more speakers than plain stereo. This makes me wonder why companies selling music audio gear do not jump this bandwagon. Appearently there are some but it is not very common. There was 4 channel audio in the past, I think in the '70, with bands recording in 4 channel, but it did not take off. There are also multichannel modern recordings available, maybe they are more targeting the HT market.
The interaction with the room of a center speaker will make the outcome certainly different. But there will be another phantom image between the center and left-right.. why not fill it with yet another speaker... and so on and so forth? I believe that there has been experiments in the past with this kind of "wall of sound".
The interaction with the room of a center speaker will make the outcome certainly different. But there will be another phantom image between the center and left-right.. why not fill it with yet another speaker... and so on and so forth? I believe that there has been experiments in the past with this kind of "wall of sound".
I've been exploring use of the Syn for just this purpose for several years now, building a lot of stuff to do so. I'm thrilled with the current status.
Current chain of devices: RPi 4B running MoOde with a ProtoDAC hat > into source selector switch > Pass FullRange EQ > Schitt Syn > 3ch out into 3 Pass 2022 FE cards for gain > 3 Cinemag transformers SE to Bal out > Neurochrome MOD86 for R and L speakers, ACA Mini bridged for Center > 3 MarkAudio Alpair 11MS drivers in small Nostromo cabinets.
Working this summer on bass augmentation though the Nostromos go deeper than I would have expected and do well. My room will support deeper bass, so I will be working there with an eye toward Burning Amp 2025/
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Current chain of devices: RPi 4B running MoOde with a ProtoDAC hat > into source selector switch > Pass FullRange EQ > Schitt Syn > 3ch out into 3 Pass 2022 FE cards for gain > 3 Cinemag transformers SE to Bal out > Neurochrome MOD86 for R and L speakers, ACA Mini bridged for Center > 3 MarkAudio Alpair 11MS drivers in small Nostromo cabinets.
Working this summer on bass augmentation though the Nostromos go deeper than I would have expected and do well. My room will support deeper bass, so I will be working there with an eye toward Burning Amp 2025/
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Another word about the Schitt Syn. It seems they may be nearing the end of their run, though Jason Stoddard has said that Gamers are purchasing them fairly steadily. I suspect they my be available used for reasonable prices. Never were very expensive given their quality and flexibility. Lots of fun.
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I've tried several things that might give you some ideas:
The best was a three channel Miles Davis SACD played back through three identical speakers. I think this is exactly what you are looking for, but you won't find a lot of three channel mixes. I think Mercury had three channel SACD's.
Another thing I tried was two full ranges stacked in the center. I used an L pad to bring the level down and I measured with speaker cable
to get the time delay the same. I actually tried taking down the left and right channels first which over clarified the center, dugh, but I had to try it. This setup works really well if your listening room is wide. Solo instruments appear in the center, it seems to work well for large scale orchestral works too. If you have more room just put two speakers in the center.
The other thing I do is use Dolby Pro with mono recordings and listen through the center channel, a proper center channel, not a sound bar. This makes mono recordings sound great.
I think the best for your application would be three identical speakers L L+R R the center channel would be left plus right mono. This would work fine, I think, with four speakers, two as the center. and it's best to have all the speakers be the same.
I remember a while back someone used a forward shaded array to derive ambiance. You seem to be doing the opposite of that.
The best was a three channel Miles Davis SACD played back through three identical speakers. I think this is exactly what you are looking for, but you won't find a lot of three channel mixes. I think Mercury had three channel SACD's.
Another thing I tried was two full ranges stacked in the center. I used an L pad to bring the level down and I measured with speaker cable
to get the time delay the same. I actually tried taking down the left and right channels first which over clarified the center, dugh, but I had to try it. This setup works really well if your listening room is wide. Solo instruments appear in the center, it seems to work well for large scale orchestral works too. If you have more room just put two speakers in the center. The other thing I do is use Dolby Pro with mono recordings and listen through the center channel, a proper center channel, not a sound bar. This makes mono recordings sound great.
I think the best for your application would be three identical speakers L L+R R the center channel would be left plus right mono. This would work fine, I think, with four speakers, two as the center. and it's best to have all the speakers be the same.
I remember a while back someone used a forward shaded array to derive ambiance. You seem to be doing the opposite of that.
Perhaps to some extent. But well-imaged (time-coherent) speakers may be able to resolve the "face" of the instrument (such as harp, violin, piano, harpsichord) to an uncanny degree.
I have done a bi-amped wall-bouncer with side-firing L/R dipoles and up-firing L/R centers. There have been many (uncountable?) related threads; some get woken up from time to time.
If you're after an ambient centre channel, try an open back driver, like a GRS planar or DML panel, placed edge on, meaning you are not looking at the face of the panel, but at the edge of it, so everything you hear from it is reflected sound. The ambience it adds is pleasantly surprising, and so conventional speakers alone sound lacking to me now.
Another idea is to go with one conventional centre speaker, with open backed on either side of the centre, with the open back's orientated edge on as above. Run the open backs from a second amp so you can change the volume ratio in relationship to the conventional speakers, assuming you can control the overall volume up stream somewhere.
I'm still trying to tune into my favourite setup, currently it's just 1 conventional speaker and 1 small DML (200mm x 300mm) but I don't listen loud and my room is small.
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Another idea is to go with one conventional centre speaker, with open backed on either side of the centre, with the open back's orientated edge on as above. Run the open backs from a second amp so you can change the volume ratio in relationship to the conventional speakers, assuming you can control the overall volume up stream somewhere.
I'm still trying to tune into my favourite setup, currently it's just 1 conventional speaker and 1 small DML (200mm x 300mm) but I don't listen loud and my room is small.
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If you want to mess around with this stuff and don't want to spend $400, MiniDSP basically created a plugin based on some discussion I had about this, fifteen years ago:
https://www.diymobileaudio.com/threads/minidsp-intelligent-rear-fill-plugin.81935/
https://www.diymobileaudio.com/threads/space-the-final-frontier.81244/
Plugin is ten bucks: https://www.minidsp.com/products/rear-center-channel-detail
The Schitt Syn doesn't have steering. That seems like a deal breaker to me: https://www.audiosciencereview.com/...it-syn-analog-surround-sound-processor.43434/
If there's no steering, you might as well just do it for free; you can turn stereo into five channel without a processor. Here's the Dolby ProLogic II Matrix:
Here's my article on it: https://www.diyaudio.com/community/threads/diy-prologic-ii.308266/
I wrote this ten years ago, but IIRC, this is my definitive thread on the topic: https://www.diymobileaudio.com/threads/five-channel-soundstage.210570/#replies
I have a friend who does this stuff for a living, and his personal preference is for https://www.perfectsurround.com/
I've been screwing around with upmixing for decades now, and I think it's still really hard to beat ProLogic II. Keep in mind that PLII has very little in common with PLI, and PLII was engineered by Jim Fosgate. It was his life's work, to a great extent. Jim is the "Fosgate" in Rockford Fosgate of course, and though they're know for amplifiers, Rockford Fosgate was selling upmixers and DSPs in the car audio market in the 90s, about a decade before that was commonplace. Jim was really ahead of his time.
My personal favorite way to expand the soundstage is to use speakers near the listener to augment the sound radiated by the speakers, or nullify the sound radiated by the speakers. If you remember the old Polk SDA speakers, the thing that I came up with works in a similar fashion. But instead of putting the cancellation speakers in the same cabinet as the primary speakers, my method takes them out of the box and puts them by the listener.
The reason that it works better this way, is because the cancellation signal used in crosstalk cancellation makes the bass sound thin. This is because the cancellation signal kills the bass - it's out of phase. By moving the cancellation speakers by the listener, it's much less of a problem.
The method that I describe in the last two paragraphs, it requires DSP delay and preferably EQ and a crossover too. Because the speakers that are there to augment the signal, or reduce the crosstalk (pick one), they must be delayed so that the wavefront from the closest speakers arrives at the same time as the sound from the mains.
https://www.diymobileaudio.com/threads/minidsp-intelligent-rear-fill-plugin.81935/
https://www.diymobileaudio.com/threads/space-the-final-frontier.81244/
Plugin is ten bucks: https://www.minidsp.com/products/rear-center-channel-detail
The Schitt Syn doesn't have steering. That seems like a deal breaker to me: https://www.audiosciencereview.com/...it-syn-analog-surround-sound-processor.43434/
If there's no steering, you might as well just do it for free; you can turn stereo into five channel without a processor. Here's the Dolby ProLogic II Matrix:
Here's my article on it: https://www.diyaudio.com/community/threads/diy-prologic-ii.308266/
I wrote this ten years ago, but IIRC, this is my definitive thread on the topic: https://www.diymobileaudio.com/threads/five-channel-soundstage.210570/#replies
I have a friend who does this stuff for a living, and his personal preference is for https://www.perfectsurround.com/
I've been screwing around with upmixing for decades now, and I think it's still really hard to beat ProLogic II. Keep in mind that PLII has very little in common with PLI, and PLII was engineered by Jim Fosgate. It was his life's work, to a great extent. Jim is the "Fosgate" in Rockford Fosgate of course, and though they're know for amplifiers, Rockford Fosgate was selling upmixers and DSPs in the car audio market in the 90s, about a decade before that was commonplace. Jim was really ahead of his time.
My personal favorite way to expand the soundstage is to use speakers near the listener to augment the sound radiated by the speakers, or nullify the sound radiated by the speakers. If you remember the old Polk SDA speakers, the thing that I came up with works in a similar fashion. But instead of putting the cancellation speakers in the same cabinet as the primary speakers, my method takes them out of the box and puts them by the listener.
The reason that it works better this way, is because the cancellation signal used in crosstalk cancellation makes the bass sound thin. This is because the cancellation signal kills the bass - it's out of phase. By moving the cancellation speakers by the listener, it's much less of a problem.
The method that I describe in the last two paragraphs, it requires DSP delay and preferably EQ and a crossover too. Because the speakers that are there to augment the signal, or reduce the crosstalk (pick one), they must be delayed so that the wavefront from the closest speakers arrives at the same time as the sound from the mains.
If you a use an independent power amplifier, then simply adding a single resistor [ of the right value ] from Left active to Right active input connections
will reduce the 'stereo content' a little and increase the 'mono content' a little, thereby raising the phantom centre.
If you use an integrated amplifier, this resistor has to be connected to the correct volume control connections.
This narrows the soundstage as opposed to widening it.
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