PDA

View Full Version : Wiring for MONO Beatles CD



STHLS5
22-11-2009, 05:55 AM
Hi Alan,

There's a local forum here on the topic MONO CDs. There are some saying using that a mono switch for the MONO Beatles CD improved the sound and MONO CDs must be heard as such.

My thinking is, if it is already a MONO recording then the MONO switch is not going to change anything but obviously I am in the minority as the majority of them argue you must engage the MONO switch even though the CD is playing left and right channel with identical sound.

Since my preamplifier got no MONO switch and out of curiosity, can I try to connect my left and right channel output from my Amplifier to both speakers. Meaning - positive left and right from Amplifier to my left speaker's positive. Negative left and right from to my left speakers negative. And I do the same for my right speakers.

Will it change the sound? or is it the correct way to listen to MONO Beatles CD as many seem to think so.

Thank you.

Regards,
ST

keithwwk
22-11-2009, 06:00 AM
Very interesting. I think I am confusing myself too...Now I also want to know if the configuration can work..but I still guess the amp will overloaded.

hifi_dave
22-11-2009, 01:03 PM
Hi Alan,

There's a local forum here on the topic MONO CDs. There are some saying using that a mono switch for the MONO Beatles CD improved the sound and MONO CDs must be heard as such.

My thinking is, if it is already a MONO recording then the MONO switch is not going to change anything but obviously I am in the minority as the majority of them argue you must engage the MONO switch even though the CD is playing left and right channel with identical sound.

Since my preamplifier got no MONO switch and out of curiosity, can I try to connect my left and right channel output from my Amplifier to both speakers. Meaning - positive left and right from Amplifier to my left speaker's positive. Negative left and right from to my left speakers negative. And I do the same for my right speakers.

Will it change the sound? or is it the correct way to listen to MONO Beatles CD as many seem to think so.

Thank you.

Regards,
ST

It will certainly 'change the sound' as, depending on the amp, it might well blow up. You are connecting the two channels together which means that one is playing into the other. Some amps will be fine with this, but most will go - bang !!!

If you want to mono a signal, do it in the pre-amp section. Just pick a spare input and join the two positives to each other and the two negatives to each other.

garmtz
22-11-2009, 01:19 PM
It will certainly 'change the sound' as, depending on the amp, it might well blow up. You are connecting the two channels together which means that one is playing into the other. Some amps will be fine with this, but most will go - bang !!!

Nope, ALL amps will switch off/give up the ghost, not just some.

A mono recording has two channels with the same information, so engaging the mono switch will theoretically do NOTHING! These people are wrong.

I think where the confusion comes from, is that some of the albums in the box were issued in stereo in some markets, but were supposed to be mono in the first place. In this case, it is a matter of preference, if you want to listen to the 'stereo' (more of a panned mono) or mono mix.

STHLS5
23-11-2009, 12:19 PM
I wouldn't say "no effect" at all. There appears to be some differences. Just can't understand the principle behind it.

ST

A.S.
23-11-2009, 12:41 PM
Do I understand correctly that someone has seriously suggested shorting the left and right speaker terminals together to create a mono signal? That's utterly irresponsible! Amplifiers do not like to see short circuits! Why not use a Y phono adaptor and combine then connect the L+R signals from the CD player into both input channels ... so the L amp input comes from the L and R CD outputs, and the R amp input also comes from the CDs L and R outputs.

I have been studying the latest Beatles remaster and am working up to a TechTalk on this very subject. The most obvious thing to notice is that they have raised the replay levels in mastering and boosted the top .... Of course the new versions sound different ....

STHLS5
23-11-2009, 12:50 PM
Ok. That was silly anyway. But how about some Beatle fans claiming better sound when they engage the mono switch to listen to already a mono Beatles CD? Wouldn't that make the sound worse because of comb filter effect?

ST

A.S.
23-11-2009, 01:27 PM
If the CD is mastered as mono, then both the L and R channels from the player will carry identical information. So pressing the mono button will sum two (hopefully) near-identical signals and should be no comb-filter problem.

I recall Sir George Martin (who I was introduced to by his wife some years ago) saying that the procedure was that the Beatles (I think it was mainly John at this stage?) sat with Martin and the engineers and agreed a mono balance between the instruments and vocals. That was the end of their interest. They handed over the production of the stereo mix to Martin (and engineers) who bar by bar panned performers L-R and decided how loud they should be within the limits of the technology. Remember, EMI were reportedly so unwilling to buy the then new multi-track tape recorders (from competitor Studer) that even Sgt. Pepper was recorded on only four (or was it eight) tracks. To be able to handle the large numbers of performers, they 'bounced down' or grouped and re-recorded tracks as they went along onto other tracks just to keep within the very few available tracks. This meant that individual performers couldn't always be isolated or panned if they had already been merged into a group. So the use of L-R stereo was rather limited, and hence not much risk that left to their own devices, the engineers would radically change the result in mixing for stereo. Hence, why the Beatles were so little interested in the stereo result in the era of mono broadcasting and portable (mono) record players.

STHLS5
23-11-2009, 02:34 PM
This is really getting confusing. I read in the Home Theater forum that you cannot have two centre speakers because identical signal causes comb filtering effect. Wouldn't the effect of merging the mono left and right signal itself can cause problem at preamp level if they are not 100% identical?

ST

A.S.
23-11-2009, 03:19 PM
I don't think we're talking about the same issue here.

There is definitely no comb-filter problem combining two mono signals electrically. But your forum is talking about combining two signals acoustically, at your ears. In such a situation, there will be a greater path difference from one speaker to you ear than the other speaker. As sound travels through air slowly, that seemingly innocuous journey difference (as we say, time of flight difference) will, at certain frequencies, cause cancellation at a reference point: one particular ear. A fancy word for cancellation from two sources when there is a time difference between them is comb filter. Do you know why?

STHLS5
23-11-2009, 03:29 PM
Please pardon my ignorance but from what you are saying it appears that the best way to listen to mono recording is to use ONE speaker only.

And the part about comb filtering I have no idea about that and just trying to understand them from the wikipedia and some other links.

Regards,
ST

A.S.
23-11-2009, 03:50 PM
Please pardon my ignorance but from what you are saying it appears that the best way to listen to mono recording is to use ONE speaker only.That's a very astute answer. I tend to agree with you.

However, the very first experimental stereo recordings illustrated the point that the quality of the central image was critical to the successful enjoyment (and marketing) of two speaker "stereophonic sound" to a general public who for two generations were accustomed to single-speaker-mono. This new "stereo" concept couldn't be too radical because the public wouldn't take to it and so much thought was put into how to present the performers in space, left to right and front to back. The front to back (z plane) was easy: the louder the sound the nearer the listener. The height plane (y plane) couldn't be encoded* into just two channels. And as for positioning the performers across the stage left-right that was again something to do with their relative loudness. If you recall, for many years there was in small type the words "mono compatible" printed on LP records to be sure the largest audience, mono or stereo equipped, would buy and enjoy. So, 'mono compatibility' meant two things: that the stereo effect on the recording had to be ignored by single-speaker monophonic reproducing equipment without markedly degrading that reproduced mono signal. Conversely, a mono record reproduced on the two speakers of a stereo system would be ....... solid and in the middle just as if the performer ghost-like materialised there, in the air, right between the speakers. That central image is called the phantom image.

The solidity and character of this central phantom image** is extremely critical to the enjoyment of stereophonic sound. Yes, as you say, the alternative would be to dispense with one of the speakers and then you have a real sound image and that will always be more vivid and 'solid' than the phantom image. This is because the phantom image, regardless of how satisfactorily it appears to you, is wholly a construct of your mind. It is the consequence of your two ears hearing the same (or nearly the same) sound from two points in space (your speakers) and then doing some processing that says 'there is no example of this in nature, so I must be hearing double, and that means I should combine these sounds together'. Just as if you were temporarily seeing double and you brain working to fuse the two images together because they must in fact be one.

I've noticed in one or other threads over the past month or two that we're beginning to touch the subject of how speakers paint that phantom image. I wrote about this in great detail here. Have a look at the jottings (http://www.harbeth.co.uk/uk/index.php?section=products&page=designersnotebookdetail&id=6)about the central phantom image, it may dovetail with this mono CD subject. The speaker designer or recording engineer who wants to grab your attention will manipulate that phantom image - needless to say, modern pop music (excluding the Beatles actually) is extremely strong in the middle of the L-R sound stage.

Comb filter: looking at a comb sideways you can see a series of teeth and grooves. This is what you'd see if you plotted a frequency response chart across the audio band.

*Some say that they get a positive sense of height from stereo. This height component is a mental construct as we associate high frequencies with vertical elevation.

** We're returned to The X-factor studio (last week) to make a follow-up video (http://www.harbeth.co.uk/uk/index.php?section=products&page=harbethinthestudio) in which sound engineer Robert Edwards specifically talks about the quality of the phantom image on his M40.1 - M30 - M40.1 system with the M30s turned off. He can't tell if the central sounds are the phantom image of the M40.1s or the M30 playing because all are perfectly matched in sonic quality and loudness - as they should be.

Pluto
30-11-2009, 06:31 PM
...because the phantom image, regardless of how satisfactorily it appears to you, is wholly a construct of your mind. It is the consequence of your two ears hearing the same (or nearly the same) sound from two points in space (your speakers) and then doing some processing that says 'there is no example of this in nature, so I must be hearing double, and that means I should combine these sounds together'.I don't believe it's altogether a "construct of the mind". Consider a stereo pair of speakers reproducing a mono source - i.e. the signal fed to each speaker is identical in every way. The left ear hears two things - the sound from the left speaker plus, slightly later because of the extra distance involved, the sound radiated by the right speaker. And vice versa for the right ear. Now it might be wise to trust me on the next point, that if you do the appropriate mathematics to resolve fully the signal present at each ear, they are identical. Complicated sums aside, this stands to reason because the entire system is totally symmetrical. If each ear gets an identical signal, you have central mono!

A good phantom image of a mono signal is, as Alan has said, vital to rendering good stereo. It also tells you quite a lot about your listening environment. The prerequisites for a good phantom image are:

matching between speakers must be impeccable
the listening room must have reasonably symmetrical characteristics
the gain & phase of the electronics in the chain must match from the lowest frequencies of interest to at least 15kHz, perhaps higher.

The final item in the list should be simple these days but in a world where that most unpredictable of components, the transformer, is making a odd comeback in particular circles, I often wonder whether the matching of new age valve amplifiers is as good as it needs to be for stereo. When you hear (or overhear) conversations implying that "1950s MONO recordings have great width on my system", I can only wonder what these folks are actually hearing!

yeecn
01-12-2009, 02:52 AM
The comb-filter effect pertains to the distances that the sound signals has to travel to reach our ears, and it is frequency dependent. The difference in distance cause the sound waves from the left and right speakers to get out of phase - so in one location two waves of a particular frequency band can enhance each other, but a few inches to the side they can cancel each other out!

I recalled reading that moving our head sideway by a just few inches the response for a particular frequency band can vary by as much as 10dB.

Honestly - I don't think the human ear is particularly sensitive to this phenomena, especially for complex music. I knew about it in theory, but I was never bothered by it. I did not even notice its existence in reality.

I just downloaded a sine wave/pink noise generator. So I may test it out later with my desktop speakers.