GOPHER Posted July 1, 2005 Share Posted July 1, 2005 How is this done with a 2 channel amplifier? I have a vintage system with three speakers and a 2 ch. amp. Last time I listened it, the center "Cornwall" did not work. I assume it did at one time? Thanks much- Quote Link to comment Share on other sites More sharing options...
Number 9 Posted July 1, 2005 Share Posted July 1, 2005 There is an old school, and new school approach to this. The old school, which PW Klipsch seemed to advocate at one time, was to have a mono center channel to supplement the discrete right and left channels. An ultimate system at one time, was to have Klipschorns in the corners along a long wall, with a Belle in the center (fed a mono summed signal). Some of the '60s receivers, for example Fisher, offered an output for a summed center channel. Nothing sophisticated about it. But there were three, not two outputs. Many people felt this approach caused more problems than it solved, and pretty much was abandoned by everyone. The New School, uses electronic circuitry to create a center channel based on a variety of techniques, including phase differences between the L and R channels. There are various approaches. Look at James Bongiorno's site for his explanation of his trinaural circuit. http://www.ampzilla2000.com/trinaural.html Meridian adopted some of the approaches floating out there for Ambisonic and Trifield and included these algorithms in the DSP of their uber preamp controller. http://www.meridian-audio.com/m_800_bro_861.htm Do a Google on trifield, ambisonics or trinaural ... you will find various explanations as to the science of this, including a review by Kalman Rubinson of Stereophile of Bongiorno's Trinaural. But just shoving a mono channel in the center as they did back in the '60s ... well, I'm not convinced. Quote Link to comment Share on other sites More sharing options...
scriven Posted July 1, 2005 Share Posted July 1, 2005 ---------------- On 7/1/2005 3:25:13 PM Number 9 wrote: ... Many people felt this approach caused more problems than it solved, and pretty much was abandoned by everyone... ---------------- Not everyone! I run a derived center! Quote Link to comment Share on other sites More sharing options...
Seadog Posted July 1, 2005 Share Posted July 1, 2005 "Not everyone! I run a derived center!" Same here. I am a big fan of the derived center in a two-channel system under the right conditions. Quote Link to comment Share on other sites More sharing options...
Number 9 Posted July 2, 2005 Share Posted July 2, 2005 Hey, I tried it too at one time. Maybe I should not have said "everyone". Let's put it this way, there are purists who have moved on to more sophisticated approaches than just a summed channel. I can see the logic with Klipschorns, that are wide apart in a room, to avoid a hole in the middle effect. Quote Link to comment Share on other sites More sharing options...
scriven Posted July 2, 2005 Share Posted July 2, 2005 ---------------- On 7/2/2005 1:21:23 AM Number 9 wrote: Hey, I tried it too at one time. Maybe I should not have said "everyone". Let's put it this way, there are purists who have moved on to more sophisticated approaches than just a summed channel. I can see the logic with Klipschorns, that are wide apart in a room, to avoid a hole in the middle effect. ---------------- Oh, so now I am impure and unsophisticated? Quote Link to comment Share on other sites More sharing options...
Hardhead Posted July 2, 2005 Share Posted July 2, 2005 ---------------- On 7/2/2005 1:21:23 AM Number 9 wrote: Let's put it this way, there are purists who have moved on to more sophisticated approaches than just a summed channel. ---------------- Number 9-- No, you can't get away with such a foolish statement. The "purists" knew how to do 3-channel correctly. You didn't, so you "moved on." Seventy years ago the "purists" at Bell Labs discovered that a minimum of 3 channels was necessary to hear stereo (3 dimensional sounds) correctly. No subsequent research has come along to challenge that conclusion. The third channel isn't about a hole in the middle. The "sophisticated" way of deriving a third channel is simply a more complicated (but not better or "purer") way of doing the same thing as a summed third channel. It's a shame you've never heard 3-channel stereo done right. Those of us who have heard both 2- and 3-channel sound know how uninformed you are. GOPHER-- Do a search on this forum on derived third channel stereo, and you'll find out what you need to know and get an education in the process--which I might suggest for Number 9 as well. Quote Link to comment Share on other sites More sharing options...
DRBILL Posted July 2, 2005 Share Posted July 2, 2005 I second the motion. Quote Link to comment Share on other sites More sharing options...
Royster Posted July 2, 2005 Share Posted July 2, 2005 ---------------- On 7/2/2005 1:21:23 AM Number 9 wrote: Hey, I tried it too at one time. Maybe I should not have said "everyone". Let's put it this way, there are purists who have moved on to more sophisticated approaches than just a summed channel. I can see the logic with Klipschorns, that are wide apart in a room, to avoid a hole in the middle effect. ---------------- HOG WASH........ Read Dope from Hope vol 15, no. 6 760061 and YOU will have the blueprint for a supurb 3 channel stereo. There are many of us here that run such a system. And I can not imagine returning to a 2 speaker system. No, most of us DO NOT use the gadetry of todays ht set ups, rateher prefer the "bridged" center. I third the motion to do a search of the topic. You will find much here on the subject. Quote Link to comment Share on other sites More sharing options...
ZAKO Posted July 2, 2005 Share Posted July 2, 2005 At one time I did some true discrete Three channel tape recordings. Playing back master tapes on multitrak mixer, with 3 amps & 3 speakers. It also depends on how well you place your mics. That could make or break the illusion. Alot of the present pop recordings do not sound very good in trying a phanthom center channel, too phazy. The new RCA Living Stereo SACD releases have some 3 channel music. Some are good. Some so so. Quote Link to comment Share on other sites More sharing options...
scriven Posted July 2, 2005 Share Posted July 2, 2005 ---------------- On 7/2/2005 10:05:01 AM Maron Horonzak wrote: ... Alot of the present pop recordings do not sound very good in trying a phanthom center channel, too phazy... ---------------- A lot of the present pop recordings do not sound very good in 2 channel! Quote Link to comment Share on other sites More sharing options...
ZAKO Posted July 2, 2005 Share Posted July 2, 2005 Its hard to find a good recording engineer these days. On TAPE OP magezine I saw a photo showing 10 mics on the drum kit. Now how do you get a stereo image out of that. Plus no two mics were alike. My therey on a good recording was to set the level than shoot the engineer To keep him from rideing the controls. Quote Link to comment Share on other sites More sharing options...
Ray Garrison Posted July 2, 2005 Share Posted July 2, 2005 Let me throw in my 2 cents... Creating a three channel system by feeding a properly derived center channel signal to a center speaker can work wonderfully well with some types of recordings. I used to run (many moons ago) an early sort of surround system by using a summed center channel in conjunction with rear effects speakers that used the Hafler trick of sending out of phase info to the rear. You'd run a parallel set of patch cords to a second amp that drives the rear speakers. Take the amp's right channel positive speaker lead, connect it to the right rear speaker's positive post. Take the negative speaker post on the right speaker and connect it to the negative speaker post on the left rear speaker. Connect the positive speaker post on the left rear speaker to the left channel positive speaker lead. This results in a mono signal consisting of the out of phase info going into the rear speakers. Recordings made using any sort of "natural" microphone placements, particularly with spaced omnis, produced a very, very realistic 3D soundstage that wrapped around you using this technique. You needed an amp with a volume control for the rears, to adjust the sound level of the "effects" channel. This setup doesn't do much with recordings made without any natural ambience. Multi-miked recordings where the "stereo" soundstage is artificially created by the engineer at the sound board just come out kind of mushy sounding. IMHO the advantage of using the newer, digital signal processing to create a center channel is that you have more control of just what signal processing is going on, and when playing recordings that don't have anything for the simple approach to work with, you can still create a reasonably pleasing sound. Quote Link to comment Share on other sites More sharing options...
scriven Posted July 2, 2005 Share Posted July 2, 2005 I can go back to a 2 channel with the flip of one switch. That switch only gets flipped when I am demonstrating the difference to someone. As Royster said, " most of us DO NOT use the gadgetry of today's ht set-ups " it is not because we are not purists or unsophisticated. In fact, I will argue that we are the purists in this discussion. Gopher, Back to your original question " How is this done with a 2 channel amplifier?" The short answer is - it isn't! You need a third amp to drive the center channel. As far as how to wire it, Gil McDermott posted the DfH with the mini box plans late last year. Here is the thread. Here is the DfH pdf. Quote Link to comment Share on other sites More sharing options...
PrestonTom Posted July 2, 2005 Share Posted July 2, 2005 Okay, okay, okay ... I just got sucked into this argument also. I am firm believer in the simple, additive three-channel approach. It does require some fine tuning however. The center channel sould not be turned up much. All you are trying to do is give a bit more "firmness" to the center of the image. When the left and right are far apart, then the stereophonic center (phantom image) can be a bit weak. It is difficult to describe so I need to resort to words like "firm and weak". A second advantage is that it will widen the sweet spot so your chair does not need to be in the exact middle. A third advantage was perviously noted in the reference to Snow et al's demonstations (the Bell Lab work) in that the image has more depth. A fourth advantage is that the center channel can (but not always) smooth out some the ups & downs in the frequency respones due to room acoustics (delay and add, comb filtering). I think when folks are disatisfied with the setup, it may be because they have the center turned up too much. This is where the fine tuning comes in. Some adjustment may be required in placing the center speaker also. Do give it a try, even it is with a mock up (cheap speaker and amp). This will at give an approximation of the effect. If it is appealing, then do a proper job of it with a better speaker cabinet. Good Luck, -Tom Quote Link to comment Share on other sites More sharing options...
scriven Posted July 2, 2005 Share Posted July 2, 2005 Tom, Good point on the volume. After playing around with my speakers in my room I found that 3db below the mains works well. Since you will be using your speakers in your room - your mileage WILL vary! Quote Link to comment Share on other sites More sharing options...
sunnysal Posted July 2, 2005 Share Posted July 2, 2005 gopher, see scriven's post with the link to the klipsch dope from hope article. it has the two schematics posted to enable a third middle channel using line level OR speaker level input. Try it, what have you got to lose? some people have been thrilled with the results of a middle channel in thier heritage setups, others seem non-plussed. YMMV. tony Quote Link to comment Share on other sites More sharing options...
GOPHER Posted July 2, 2005 Author Share Posted July 2, 2005 Thank you all. There must be a third mono amplifier hidden in the cabinet that is not working. It is an inheritance in a far away country that I must figure out what to do with. I'm thinking maybe a Mcintosh MC40 or some other tube monoblock, since the rest of the system is Mac. I will investigate further and check the "Dope from Hope" for more tips. Thanks again.... Quote Link to comment Share on other sites More sharing options...
Number 9 Posted July 2, 2005 Share Posted July 2, 2005 ---------------- Oh, so now I am impure and unsophisticated? ---------------- Man you guys are touchy ... I did not mean it to be derogatory. What I really meant to say: Is if you look at (for example) what takes place with trinaural or trifield, espescially the science and reasoning behind it, it is far more sophisticated than a summed channel. If you read some of the discussions about it, they also talk about the many downsides to just a simple summed channel. Trifield, ambisonics and trinaural in fact recognize the benefit of a middle speaker, but just try to do it better. In fact, ambisonics began as research back in the 1960s. So why knock down progress and improvement? Quote Link to comment Share on other sites More sharing options...
sfogg Posted July 2, 2005 Share Posted July 2, 2005 I am one of the ones that use more advanced methods of deriving a center and surrounds out of two channel music. Both the basic summed center and more advanced methods have advantages and disadvantages to each other. Shawn Quote Link to comment Share on other sites More sharing options...
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