4-channel audio
Join Our Community Subscribe to Paul's PostsThere’s a lot of information in a stereo recording that some systems don’t reproduce well. In fact, most systems keep the room cues and ambiance locked away in our recordings.
One way to unlock them is by careful 2-channel setup and the very best electronics. Like what we’ve done in Music Room Two with our BHK electronics and IRSV speakers. That system has spatial cues that often times surround the listener in uncanny ways.
Yet, few of us have an IRSV and a complete BHK stack. Is there a way to get more of what’s locked away in our recordings with what we have? David Hafler certainly thought so.
In the 1970s, audio designer David Hafler experimented with what has since become known as The Hafler Circuit. In it, 4 speakers are employed rather than just two. The extra pair of speakers are in the rear of the listening room and provide a sense of space that few systems can come close to duplicating today. And the Hafler Circuit required no extra electronics.
If you want to experiment, dig out that old pair of bookshelf speakers that might be gathering dust in a bedroom or closet. Position them the same distance apart as the front speaker, but behind the listener. Then, run another set of speaker cables to the rears. Connect only the + lead from each channel to the + input on each rear speaker. Using a single speaker cable lead, tie the two – terminals of the rear speakers together.
Voila! Surround sound from 2-channel.
This scheme actually works and takes advantage of the fact that in a live performance, the distance between the audience and the performers is great enough that there’s a phase difference between them. Thus, the audience is out of phase with the performers and that difference is played on the rear speakers. When you play studio recordings there’s always enough phase differences to light up the rears and you get a sense of surround sound.
It’s more of a fun project than anything I recommend, but that’s what we’re here for.
“There’s a lot of information in a stereo recording ” = Yes, on one of my CD’s you can hear a bird that shouldn’t bee there.
If you got a really resolving stereo you can hear lots of things…………and that’s bad sometimes because you loose your focus on your music. At least I do that sometimes.
I often heard phantom images from behind when listening to 2-channel stereo in a dealer’s show room with careful room treatment. Thus I guess that there are not only room cues but cues based in the recording and mixing or in the speaker design which can create phantom images behind the listening chair. The basic problem of two channel stereo is the crosstalk between left and right speaker output. Thus instead of perceiving the sound wave of an instrument with a time delay at the ear more distant from the instrument the two channel listener of this instrument perceives two sound wave (left and right speaker) which produces strange combfiltering effects our brain has to interpret. And adding more and more speakers for home theater applications makes things even more confusing with maximizing comb filtering/crosstalk. I cannot understand why recording and sound engineers having the most sophisticated mixing tools on hand do not provide us with crosstalk-free music.
Zeppelin Whole Lotta Love has those behind you cues in the recording in droves.
Fairly extensive research on this subject, which was popular in the 1970s, can be found here.
http://downloads.bbc.co.uk/rd/pubs/reports/1974-29.pdf
This was based on having a 4-channel broadcast source and the BBC resumed trials by broadcasting the Proms in 2015 in surround 4.0.
https://www.bbc.co.uk/taster/pilots/proms-surround-sound
https://www.bbc.co.uk/blogs/radio3/entries/c90406f4-2f88-3f4d-ad99-74523941b9c1
TV broadcasts are in 5.1 if you fancy that.
thx for posting these links
Off topic.
The Australian Federal Govt. decided 12 yrs ago to create the National Broadband Network (NBN); basically $65AU billion down the drain.
They are optic fibering the whole of Australia & by the time they finish this mammoth project 5G will be 12 times faster.
Our street got hooked up to it 2 months ago; we had no issues when we were with the privately owned ‘Telecom’ company NOW we are having issues…drop-outs occurring all f#@king day & night.
It’s such a disaster that we have nick named it the ‘No Bloody Network’ (NBN)
A tech is coming out tomorrow between 13:00 & 17:00 to asses the problem.
I might be off-line for a while…you won’t have to read my drivel 🙂
Mike & Richtea from yesterday’s post ‘DG 4D’; thanks guys.
Don’t know when I’ll be back, as I’m using a friend’s cell phone sim card to send this.
Sorry to hear FR – best of luck back in the dark ages.
I did find it amusing that you used the word asses instead of assess. It Seems very fitting.
My experience is that every time the gov’t gets involved in some endeavor (especially if it’s business) the people loose . But politicians and regulators know what is best, just ask them.
Mike,
You mean that you find it amusing that I can’t spell ‘assess’
I wish that I could ‘claim’ what you read into it 🙂
The ‘techy’ came out today (Indian dude; of course) & fixed the issue within two hours…yaaaay!
I meant what I said. I’m not laughing at you, but with you. It’s amazing how one “s” can change the whole meaning.
Glad you’re up and running again. (Hoping it stays that way)
Happy Holidays and Merry Christmas
Mike,
I know you wasn’t laughing at me; not that I mind at all, as I laugh at me quite a bit. (I’m always up for a laugh, whether it’s at my expense or somebody else’s…that’s the Aussie way)
Frustration from months of dropouts & the crap excuses that cust. serv. give time after time until you force them to send a Tech.
Hoping that it now stays that way too.
Best wishes to you & yours too!
Technology, we love it, we get used to it, we come to depend on it. But when it fails we can get lost, that world we are used to collapses, we can’t communicate as we would like to, we just start to feel so detached.
Oh well, will just have to listen to some more music, providing of course you’re not dependent on streaming! Or read a book, hope you have a hard copy.
Look forward to your return F R.
Richtea,
Yeah, give me a pen & paper any day 🙂
Like when you take an umbrella with you & it doesn’t rain (insurance)…having informed you all that I may be off-line for a few days meant that the ‘techy’ solved the issue within two hours today.
I’m a dinosaur, I don’t stream, I’m drowning in CD’s.
I’m back baby!!
(Not that I was ever gone, as it turns out)
Fat Rat,
Expect the worst, hope for the best. Good they were able to get you ‘Bach’ online so quickly, especially at this time of year.
I’m a CD dinosaur too, thankfully not extinct… yet.
Richtea,
As I said to Mike here, that the NBN cust. serv. has been fobbing us off for weeks with crap excuses. We have fibre to the street & then copper to the house. It’s the stupid, cost cutting way that our Govt. decided to implement the network…morons!
Best wishes to you & yours!
Was expecting Fed Ex to deliver the DSDAC yesterday. Didn’t happen.
May play with with this now , who knows, this scheme this may make the difference I’m looking for.
In the early 70s this was experimented with by most of the HiFi buffs I knew who had a spare speaker or speakers. Initially it had a considerable ‘Wow’ factor; listeners were impressed by the surround sound effect. Although we didn’t talk about soundstage in the UK at that time I suspect that most listeners were soon confused by the 3d effects created and abandoned the experiment, although a couple I knew introduced resistors to reduce the volume coming from the rear and persisted for longer. I felt it was an amusing novelty, and was glad that I tried it, just as I was happy to abandon it.
Hafler also manufactured a small metal control box with a volume control. One version (if Irecall correctly) had a balance slider. A number of equipment manufacturers also integrated it into their 4-ch. receivers, along with Ben Bauer’s SQ and the JVC discrete systems. For classical music I preferred the (normally) lack of direct rear sound of the Hafler system. For me, the key was to keep rear speakers far enough away, high on wall, low in volume, and pointed at ceiling for the ambience bounce. Added simple, acoustical enhancement without detracting from over-all sound quality (most of the time). When listening to metal and other musical genre, I could turn the rear volume up.
Today, the same high-end audio police, who refuse to allow even a loudness control for low-level listening, frowns on such. Paul could have his credentials pulled by the high-end audio police for the apostacy of talking about it. 🙂
Paul loves playing the outlaw. 😎
The best way to hear music live the way it sounds in an arena from your seat is to capture it at a live event, not a studio. The way most studio recordings are mixed they are not meant to sound like music played live in Carnegie Hall but rather a very controlled quiet environment. There’s no real hall sound in a studio and you can hear the difference. Not to say studio recordings are bad. In fact I believe in many cases they sound better then in a live hall which is why we can distinguish live from studio. If you want your system to sound live you will never get that just by upgrading to a state of the art system. The most you will get if at all is better studio sound. Buy quality live recordings in you want to get closer to live. Buy a well recorded video. It’s easier to feel you’re hearing live when you can see the performers.
I’m sure the kit, the size of a small car, in Paul’s music room can blast music from all walls and ceiling and sounds amazing.
While I sometimes listen in Pure Direct Mode Stereo with largish floor standing speakers in my relatively small, by American non-city apartment boasting standards, English living room I now typically listen using my high-end’ish Denon AV Amplifier in multichannel stereo mode. This uses quite subtle techniques to add more than ambiance from the surround channels and more focus from the centre. While Paul has stated the surrounds don’t have to be that big or good I disagree. My front centre uses the same midrange and tweeters with quite big 6” pair for bass, with centre back and rears using similar tweeters and not exactly small bass units. This is great for real surround in movies and music, especially in lossless high quality modes from Blu-rays not available to steaming video sources.
When used with good stereo sources the subtle but high quality multichannel stereo mode sounds stunning to me, from mostly vocal and small acoustic groups to large orchestral and pop/rock from the Beatles to Led Zeppelin and more…
… while there are some totally stunning SACDs with 5.1 sound, like The Dark Side of the Moon, and DVD-Audio like Court of the Crimson King when I listen to most stereo sources it’s using multichannel stereo mode.
I’ve just tried it again, with some of Paul’s picks. While the pure direct stereo mode sounds great from the Monitor Audio 6G Silver 500 floor standing stereo pair, there’s no gap in the middle from wide spacing or booming from corner placements or noticeable step differences from its three way speakers, when multichannel stereo is turn on the room disappears and I’m there. Be it a close mic studio, a live concert hall or the weird and mesmerising Pink Floyd etc – it seems to sound more spacious, more real and always more enjoyable.
If the stereo purest of you ever get the chance to take a listen on similar kit I’d like hear what you think. It might not match the glorious IRSVs, but then it doesn’t take up most of a largish room or cost hundreds of thousands. Perhaps you could tell me what I’m still missing that’s good, or hear what’s bad?
Paul,
Will this Hafler set-up work off of a pre-amp? If so, one could just get a small amp for the ‘surrounds’ and leave one’s stereo amp’s out of the equation.
Thanks
There’s a number of ways one might make this work but the way David Hafler described it is easiest. I wouldn’t put too much tho0ught or energy into it as, in the end, it’s more interesting gimmick than valid process one should follow.
Particularly brilliant designers such as: James Bongiorno, Dick Sequerra, David Hafler and others equally famous, worked for Dynaco, in the golden age of this brand. It is my guess that Hafler has been behind the QD-1: 4 Dimensional Quadaptor, marketed by Dynaco at the time the quadraphonic sound appeared on the market.
The Quadaptor (QD-1) is connected between a stereo amplifier and 4 speakers without the need for a second amplifier, this small device (weight: 2.5 Lb) provides up to 12 dB of attenuation in the rear speakers plus a null balance switch for correct separation adjustment, and switch-out of the back speakers for conventional stereo listen. Like the other matrix decoder the Quadaptor recovers properly processed front, rear, left and right signals from stereo sources.
It was a novelty for the fans, that we had the ability to make good solderings, because it also came in a kit at a price much lower than the $ 80.- that the factory assembly cost.
I stopped using it when I found that the separation of the front speakers was compromised (the device being connected in the recommended way) when the rear speakers were not used.
In this link you can see the QD-1 whose operation is so interesting although more complex than described in today’s post.
https://www.google.com/imgres?imgurl=https%3A%2F%2Fus.v-cdn.net%2F5021930%2Fuploads%2Fattachments%2F1%2F6%2F4%2F3%2F9%2F7311.jpg&imgrefurl=https% 3A% 2F% 2Fforum.polkaudio.com
Sorry for the error in copying the link:
https://www.google.com/search?rlz=1C1SQJL_esEC817EC817&q=Dynaco+4+channel+device&tbm=isch&source=univ&sa=X&ved=2ahUKEwia8sStmsnmAhWXZs0KHd11BBAQsAR6BAgGEAE
“David Hafler and others equally famous, worked for Dynaco, ”
Hafler was not a Dynaco employee, but the co founder and owner.
It’s nice news for me, and thanks for the clarification, but Hafler worked for Dynaco anyway, delivering his valuable input while he was there.
Who was the other co-founder?
Ed Laurent was Hafler’s partner and was a designer of the ST70 and other later models while Hafler mostly kept to the business side of the firm.
You are free to think of Hafler as having done work for Dynaco as long as you also write that Henry Ford worked for Ford Motor Company.
Quadraphonic sound had an interesting evolution. Back in the early 1960s just after the invention of the wheel and discovery of fire, one problem with stereo sound was the dreaded hole in the middle. And so the center channel was born. Some amplifiers even had a center channel output jack with a volume control like my first amplifer HK A500. One problem was you not only needed a separate speaker but also a separate amplifier. Then someone got the idea of putting the center channel behind you. I think Stereo Review magazine published the idea of using the main amplifier and wiring the rear speaker between the two hot terminals. Halfler’s Quadaptor was the same idea for the rear channels only wiring two rear speakers in series. It was noted that this L-R signal carried “ambient” information and so the idea of quadraphonic sound was born. Record companies realized they could encrypt four channels into two using tricky phase manipulation during recording and the inverse during playback with an adaptor, an extra stereo amplifier, and an extra pair of stereo speakers. Among the pioneers were CBS records, Sansui, and a few others. This system was called the “matrix” system. It had the advantage of being compatible with two channel record players. RCA had their own idea for “discrete” quadraphonic sound recording the rear channels above 20 khz and then downconverting it during playback. It required a special cartridge that could respond to at least 40 khz and a decoder. The records were also compatible with conventional 2 channel systems. I’m only aware of two companies having made such cartridges, B&O and Empire. I still have Empire’s TOTL of three models they manufactured I bought it at a trade show from Empire, model 4000D/III for $50, a 67% discount. It sounds identical to the 999VE to my ears. And then there was tape. The quarter track system virtually universally adopted by audiophiles that had two tracks in each direction was adapted to have four tracks in one direction with an extra pair of recording amplifiers and playback preamplifiers. This model Crown CX844 may have been the best tape recorder sold to the consumer market.
http://www.audioasylumtrader.com/ca/ca.html?ca=160591
Having just come back from spending two years abroad I was eager to try quadraphonic sound out. The advertising hyperbole promising concert hall sound and ambiance was enormous. So I set one up in my parent’s basement with equipment I already had. I had great expectations for it. The “experts” promised. It didn’t work. Not close and not a chance. It was clearly a fatally flawed idea. By this time I was an engineer with a strong background in many sciences. My curiosity led me to think about why it didn’t work. (So many ideas that sound so good on paper and get such great accolades don’t work well if at all in the real world.) And in comparing what quadraphonic sound delivered and what concert halls delivered I came to understand why. That was my point of departure from the audiophile world that took me down an entirely different road and I never looked back. It wasn’t the road less traveled, it was the rod NEVER traveled.
There’s a blast from the past. I used to have a Hafler setup back in the day, and yes, it did actually work! But not enough that I wanted to keep it in place long-term. It would be interesting to revisit that today, with the quality of equipment I now have in service, but I’m not sure how it would actually fit in my listening room!
It depends on what you mean by “works.” Does it create an interesting effect that is different from two channel stereo? Yes it can. Does it come close to recreating a live concert hall experience? No, it misses by a country mile for a whole slew of reasons. Ironically it overlooks the same fact about sound that binaural recordings played through headphones does and so while the failure of binaural playback sounds different, the underlying cause is the same. IMO the reason quad was a market failure wasn’t because of the large number of competing systems but because it was a technological failure when judged against what it promised. Had there been a winner that one would have persisted. I call HT son of quad and 7.1, 9.1, 11.1 grandsons of quad.
Agreed. It “works” in the sense you described, but no more than that, primarily because it fundamentally cannot.
I think one of the issues with multi-channel sound in general is that there is a considerable disconnect between the requirements for pure audio and for Home Theatre, and it is the latter that drives the technical aspects of the multi-channel market. For Home Theatre, the emphasis is totally on spectacular sound-effects, rather than on the re-creation of a plausible acoustic event.
Also, as I consider how difficult it is – with all the compromises involved – to get a good in-room stereo experience properly set up, that whole imbroglio seems to me to multiply exponentially with the number of additional speaker channels added. I have heard multi-channel audio demonstrated many times, and have never once heard anything that totally convinces me. On the other hand, Peter McGrath, who has made some of the finest-sounding stereo recordings I have EVER heard, told me that he prefers to listen to his own recordings at home in 4.0 multi-channel sound, which he considers to be the optimal audio format. In particular, he disdains the use of a centre-channel.
Bravo, Paul! I did exactly this, around 1981 and the results were astonishing. (In a good way.) I also inserted a volume control in the line to the rear speakers to help control the volume of the rear speakers, which was helpful. I heard things I never heard before!
Hafler was an attempt…. I was back then and had access via a stereo shop I worked for. It was interesting. Up to a point. What was the true key to real live sound was a high quality digital time delay that would recreate the effect of the time delays that take place in various rooms/halls. At one time when I had been selling audio I was thinking of starting my own shop which was dedicated to this tool for audio. And, to blow the minds of the listeners? Have small speakers in front hooked up around larger speakers that were not playing. Then allow the listeners to guess which speakers were playing the front channels. That is a mind blower. And, its a humbling experience to see how wrong one can be. The sound shrinks when the rear delay is turned off in a most startling way. For those little guys were sounding like giants!
To make it work. Big speakers with excellent bass need to be the ones behind you! Being hall/room effectors. They do not need super high frequencies ability. They need to replicate what a room reflects. But it must be done right. Not for sound effects. You can make it sound like a band is playing around a large indoor pool with reflections not like what is heard with live music.
Its just got to be perfected which never took place back then because electronics were not as advanced as we now have today. Back then only the wealthy at that time could afford it, and it never caught on because salesmen wanted to sell huge speakers/expensive instead. But, the bigger speakers are needed in the rear! If they have excellent bass, the small speakers up front will not need any subwoofers!
Yes…. I was considering opening a shop that was to sell digital time delay systems. But, that was only a desire that I had no means for doing. When its set up right people would save their money till they could afford such a system. It makes two speaker systems that might sound mediocre transform into something fantastic when the rear speakers were set properly. What is needed is phase coherent front speakers for the best live sound illusion. It trumps all other illusions that a two speaker system can offer. It gives you the hall and depth… Not some ersatz illusion of it.
This is not about having fours channels. Its two channels in stereo up front, and having the ability of sensing the lost ambiance coming from behind you as you would sense hearing a live band. You will not hear a helicopter flying from behind you and over your shoulder heading up front. That is theater effects. You will just feel like you are sitting in a concert hall with the musicians up front on stage… or adjust the delay for a small intimate club.
I still have in my closet an old Yamaha DSP delay I found on Ebay that needs to be refurbished. Maybe one of these days it will see action again.
Merry Christmas….
I
In my organ audio system I have one 2-channel source but two amplification systems: the front 2-channel system which reproduces the original 2-channel recording and a second rear-channel system that includes a Bricasti M7 stereo reverb processor that coverts the original 2-channel signal into a 2-channel hall response, which when played through the rear system simultaneously with the front system gives the listener the illusion of being in a hall, such as a music studio, a concert hall or a cathedral. The parameters of the hall (reverb time, decay characteristics, liveliness, frequency response, listening position, etc.) are adjustable so the hall can be whatever you want it to be. This is one way to simulate 4-channel without a 4-channel recording. It also allows you to change or enhance the spatial characteristics of the original recording if that is something you want to do. Even just playing the original 2-channel recording through front and rear speakers without any reverb applied gives a fuller, more engaging sound. Sound reflected from the rear of a space is typically high frequency attenuated and less crisp in its attack. I simulate that phenomenon by using a tubed amp and warmer speakers in the rear system. My simulated 4-channel system allows the hall characteristics to be adjusted to suit my listening room and tastes. I’m not stuck with the original acoustics. Yes, I’m cheating. But sometimes cheating results in a better sound!
JosephLG… That must sound quite pleasing.
Genez, I just noticed that you commented on a similar approach as mine. We are on the same wavelength. I would add that I think big, full-range speakers in both front and back are beneficial for maximum realism. Also, the reverb unit and the amplification system must be extremely high quality, otherwise the reverb will not sound natural. The Bricasti M7 is the best stand alone reverb unit I’ve heard. I combined it with an audio amplification system that is as expensive as the primary system. To skimp on either will degrade the sound.
JosephLG… I just looked up the Briscasti M7… balanced mode! Now that is what I have been looking for, but had no idea existed… Now, to win the Lottery. 😉 Beautiful!
Yes… you can use large speakers in front. It will make you feel closer to the performers. If you like sitting back a bit in a concert hall? A small speaker will give that effect, and the bass will be strong throughout the listening area with large speakers in back.
Another benefit. The sound will be full and can fill the room. Yet, you will be able to converse with someone sitting next to you, like you can do at a live concert. The music seems subjectively louder. We used to get a smile out of that factor in the sound room in the audio shop.
The Bricasti does indeed look splendid – I worked with Lexicon gear for many years (mostly the PCM70 et al) and really enjoyed designing individual spaces piece by piece.
Out of my price range at the moment but good to see someone took Lexicon’s already good position and developed it further 🙂
.
have two problems with this. First, commercial recordings have too much reverb for my taste, and de-reverb algorithms add un-acceptable temporo-spatial distortion.
Second, although the Bricasti is among the better professional digital reverb units, it is still based on statistical reverb, that is the reflection statistics match the statistics of theoretical rooms, instead of replicating the impulse reflection signature of a real room (convolution reverb). Bricasti calls this “synthesized algorithimc” reverb.
The easy way to tell the difference: REAL reverb is too complex to calculate, so it can’t have parametric controls, just pre-recorded presets.
Fortunately your problems are not my problems. I love the smooth, realistic sounding Bricasti reverb in part of my system, even if it is “based on statistical reverb” and not convolution reverb. I do not use, nor have I ever needed to use, “de-reverb algorithms.” In addition to dry samples, I use Hauptwerk organ samples which capture the “REAL” room reverb, The new Hauptwerk version 5 has in addition built in convolution reverb. I agree with you about too much reverb. I typically favor halls with something like 2.5 seconds for best pipe organ clarity and tonal rendition. I prefer a mix of wet and dry samples. I have up to 12 separate channels and 35 speaker drivers in play simultaneously at times.
I had big fun setting up comparisons at audio shows between stereo recordings decoded with Hafler and the Quad versions of the same recording. In the vast majority of cases, the Hafler absolutely trounced the Quad version and it wasn’t at all subtle.
I began my recording career in 1965. At that time, most pop music was intended for mono reproduction and everybody made production decisions using a single monitor speaker. The “suits” wanted the extra income from stereo versions. These got mixed after the fact with little or no artist or producer participation. They pretty obviously were not nearly as engaging as the original mono versions. This was because pop music mixing is all about balancing musicality out in front while tucking in the inevitable warts.
Around 1968, the big chain stores began refusing to order mono albums and FM stereo radio had become an important form of exposure. This resulted in producers starting to make decisions based on stereo monitoring. A couple of years later, “quad” arrived with hi-fi manufacturers and record labels hoping to repeat the sales explosion stereo had created. Again the “suits” ordered remixes and again these were not nearly as good as the originals. One exception stood out which was Dark Side of the Moon which had actually been produced using four-channel monitoring. Unfortunately, by the time it got released, almost no stores still had the ability to demonstrate quad. To this day, record production is almost all done using stereo monitoring.
A friend of mine got hired to produce a 5.1 recording of an independent band. After they completed the album, they wanted a stereo version for streaming. To his shock, he found that he needed to choose completely different takes in order to create an equally compelling stereo version. The production monitoring format is a big big deal!
Also the jazz genre would have a load of lemons less, if labels would have trusted the good ones of the engineers more often!
This reminds me of a Jerry Wexler interview. He said he checked his mixes at Stax by sitting on the back porch with the door open, and that he mixed to 1/4dB. These are very important factoids.
1dB is the best people can hear isolated sine waves in headphones, but musical balance is far more critical. Further, the difference is important through a window or door – which is essentially what audio is, a window onto the the music.
Actually, contemporary research shows that 0.1 dB. is very much audible although it is generally recognized as being “better” as opposed to “louder.”
There is no time delay with the Hafler system? It does not adjust for room sizes trying to recreate?…
The Hafler circuit at its most basic uses nothing but speaker wire and at its most complex ads a pot and a few resistors.
Paul, I see a new product. Lets say $1,000 in cost. It sits between a DAC and a pre-amp. Most/many of us have audio systems that have surround speakers, maybe because SACD promised must-channel audio, maybe for other reasons. It looks at the non Left and Right Audio channels and looks fir noise, if it sees it it puts some combo into other channels for surround music. It uses other balanced inputs into your high-end pre. …
I’ve implemented the Hafler hookup several times over the years but always end up going back to 2 channel. What I learned was that all 4 speakers need to be sonically identical so as not to draw attention to the rear signal. A level control(potentiometer) needs to be inserted into the rear feed to control the rear signal level. The rear set of speakers needs to be placed so as not to sonically interfere with the front stereo signal as a signal that is panned hard left or right will be produced at full signal level in the rear speakers which will cloud the stereo separation. One application that produced some serious 3D sonic images was to use 4 sonically identical speakers but instead of sending the ambiance signal to a rear set of speakers, place an ambiance speaker a foot outside of the left front speaker and
an ambiance speaker a foot outside of the right main front speakers with both ambiance speakers pulled back about 1.5 feet.
I did this with a pair of Alon Lotus SE mk ll’s as the front mains and a pair of Alon 1’s as the ambience speakers and the Hafler hookup combined with the dipole nature of both Alon speakers produced some extreme 3D signals that would appear right next to ones left/right ears and even some strong behind the head images! Watching movies was a blast!! The main drawback was again a smearing of the stereo signal with hard panned images. It was both a fun and educational experiment to say the least.
Hello Paul,
Thanks for the circuit. I have a pair Spendors sitting around which I have hooked up and am enjoying it. I am driving my Mirage M6s with a pair of old Quad IIs . Was concerned that they may not drive all the speakers but no issues there!
I am amazed at how easily the old Quads 15 watts each are able to drive the Mirages. I was using your old PS Audio 4.6 but have temporarily retired it and have hooked up my PrimaLuna pre amp. Great sound stage.
Thanks once again.
All the best for 2020
Pheroze Madon
Fun! Thanks for letting us know.
Paul, you asked, “Is there a way to get more of what’s locked away in our recordings with what we have?”
Yes, there is a way to unlock what’s been locked or perhaps better stated, make audible volumes of music info including much ambient info that until now has remained inaudible and it has everything to do with drastically lowering a much raised universal noise floor. Assuming of course that we agree any music info below a given noise floor remains inaudible while the music info above the noise floor remains audible.
Sorry to say but your / Hafler’s example 2-channel x 2 does not unlock any hidden (inaudible) music info whatsoever. Rather I suspect it simply mimmicks a type of surround sound to create a bit more interesting sounding phenomena. Which pretty much is all that surround sound accomplishes.
And like surround sound you could add 30 more pairs of speakers to generate an even greater sounding phenomena. But in the end such examples do zero to make audible any of the large percentage of music info that remains inaudible below a much raised noise floor.
This might be a better example. Say MP3 formatted music is all you can listen to on your playback system because your CD transport is out for repairs. If memory serves, MP3 music contains roughly 10% of the same Redbook recording. So there you are listening to your favorite tracks in MP3 and you know there’s more info to every track you listen. So you add 2, then 4, then 8 more pairs of speakers to your 2-channel output and low and behold you have an interesting phenomena that you’re listening to. But it’s the exact same music info as before. Due to universal and quite severe distortions that plague every last playback system (think universal performance-limiting governor), listening to digital or analog music is not all that much different from this example. IOW, when we don’t address the root cause, it really doesn’t matter much how we deal with the effects.
So what are we really talking about regarding this locked music as you put it? IMO, today’s best SOTA-level playback systems might be able to keep audible at the speaker maybe 55 – 65% of all the music info embedded in a given recording. And I would not doubt that it could be worse than that and no doubt impossible to measure but certainly not impossible to hear.