Allan Songer Posted August 25, 2005 Share Posted August 25, 2005 English: When you engage the mono switch on your preamp when playing a mono LP it will sound better. Quote Link to comment Share on other sites More sharing options...
3dzapper Posted August 25, 2005 Share Posted August 25, 2005 dragonfyr, If I read your polar plots correctly, The comb filtering occurs off axis and is minimal or nonexistant at the listening possition? Rick Quote Link to comment Share on other sites More sharing options...
Guest BobG Posted August 25, 2005 Share Posted August 25, 2005 Dragonfyr has very clearly described the problem of multiple sources covering the same band of information. Intelligibility is a huge issue in sound reinforcement and sound reproduction systems and there are a number of ways to quantify that parameter. If you get the chance in a large performance venue with a sound reinforcement system, take careful note of the clarity of the sound in your seat and then go into the aisle and listen again. A properly set up reinforcement system puts the overlapping lobes of output (from the multiple speaker cabinets) in the aisles rather than in the seating areas. Intelligibility is far better in the seats and this is a little-known part of the art/engineering of large space reinforcement systems. If you want to surprise yourself, there is a fairly simple test you can do at home. You'll need a source of pink noise such as a test CD or lacking that, you can use interstation noise from an FM tuner with the muting turned off. You'll also need a couple of speakers, but I'm guessing that's not a problem. Put the two speakers right next to each other (did I mention this is easier with small speakers) and play the pink noise. Listen to it from your normal listening position. Now, have your lab assistant (whaddya mean you don't have a lab assistant?) move one of the two speaker backward about 2 inches. You'll hear HUGE shifts in the tonality of the pink noise. Now have Assistant move the speaker slowly forward and backward a few inches. Again, you'll hear major changes in the tonal balance of the noise. This is due to the cancellation and reinforcement of the sound at different frequencies and different distances between speakers and listener. Classic comb filtering as Mr. D stated above. It's called comb filtering because the resulting frequency response looks like the teeth of a comb; especially in the mids and highs due to their progressively shorter wavelengths. The same thing is happening when you listen to mono through more than a single speaker. The distance between the sources causes severe comb filtering of the sound. As Max points out, it isn't horrible, but that's due to the ear/brain's ability to sort through the tonal errors. They are still there and if you do the test I described above, you'll seek another solution. By the way, this same thing happens when you try to use two center channel speakers which seems to be popular in some circles. Thanks Dragonfyr for the informative posts. Quote Link to comment Share on other sites More sharing options...
ben. Posted August 25, 2005 Share Posted August 25, 2005 ---------------- On 8/25/2005 8:46:30 AM Allan Songer wrote: English: When you engage the mono switch on your preamp when playing a mono LP it will sound better. ---------------- My point exactly. Douchefyr is overreacting as usual in his pathologically desperate attempts to impress us, which is really strange considering his overt contempt for the members here. Quote Link to comment Share on other sites More sharing options...
DRBILL Posted August 25, 2005 Share Posted August 25, 2005 It would be a good discipline for all of us to go back and read or re-read Paul's technical papers with an eye to style and form. He acheived clarity through brevity and parsimony. He was a humble man who genuinely wanted to share his discoveries with others. He made his wisdom accessable. I almost didn't post this. It is not intended to be critical. DRBILL Quote Link to comment Share on other sites More sharing options...
Dflip Posted August 25, 2005 Share Posted August 25, 2005 Bob, thank you for dumbing down the response for those of us who are not engineers by including examples which we are familar with and could actually experiment with to see how it works. I actually think I understood what you said. Don Quote Link to comment Share on other sites More sharing options...
fini Posted August 25, 2005 Share Posted August 25, 2005 What would be the effect of the two speakers (mono source) being 180 degrees out of phase with each other? I would guess the comb effect would be gone, but the sound "muddied." Quote Link to comment Share on other sites More sharing options...
dragonfyr Posted August 25, 2005 Share Posted August 25, 2005 ---------------- On 8/25/2005 9:18:18 AM ben. wrote: My point exactly. Douchefyr is overreacting as usual in his pathologically desperate attempts to impress us, which is really strange considering his overt contempt for the members here. ---------------- What Bob described is exactly the classical experiment to demonstrate comb filtering! I apologize for confusing a few of you who only offer attacks. And impress you Ben!? Gee Mr. Wizard. Come now! I would be ecstatic if you simply understood a few of the small words! The problem is not in the signal processing (although there is the potential for issues here if the signals are combined incorrectly), it is in the acoustical playback of multiple channels of the identical signal. And the comb filtering and polar anomalies will still exist, as the two mono signals are not emanating from point sources!!!!!! And this in phase point is just that a point that shifts (generally) vertically and is not coincident for the differing drivers! There are differing degrees of abstraction in the sound 'chain', and while small differences in phase between adjacent pass bands are not critical, the varying acoustic centers of the drivers in multiple speakers also create a problem with comb filtering. It is also the issue directly behind the concept of the coaxial driver - to combine multiple pass band recreation with coincident coherent acoustic origins. Sorry Ben for the emotional distress I caused you, but this is simply time domain acoustics 101! And I am really not too surprised that some choose to remain oblivious to the concept. But then for some, ignorance is indeed bliss. As as far as your "point", if you comb your hair just right, people may not notice! For others it is a real issue that presents a challenge to address in its many layers of complexity.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /> Quote Link to comment Share on other sites More sharing options...
garymd Posted August 25, 2005 Share Posted August 25, 2005 ---------------- On 8/25/2005 8:46:30 AM Allan Songer wrote: English: When you engage the mono switch on your preamp when playing a mono LP it will sound better. ---------------- Exactly! Allan, Didn't you once post a closeup picture of a stylus in a groove and explained what happens with a mono LP vs stereo? I actually understood that and it made perfect sense. Do you still have that somewhere? I have no problem with you guys getting technical. I wish I could follow but there's no way I could even pretend to understand. I'm not sure I have the energy for that today anyway. Quote Link to comment Share on other sites More sharing options...
dragonfyr Posted August 25, 2005 Share Posted August 25, 2005 ---------------- On 8/25/2005 9:49:04 AM fini wrote: What would be the effect of the two speakers (mono source) being 180 degrees out of phase with each other? I would guess the comb effect would be gone, but the sound "muddied."---------------- Its often referred to as "active noise cancellation". The same technique used in noise cancelling headphones, many auto mufflers, and many other technologies. Oh, and Flipper, the experiment has been stated several times in past posts regarding this same issue. And isn't it nice to observe that if some don't understand an idea, instead of asking for clarification or engaging in conversation, they simply whine - and then persist in demonstrating their ignorance. Quote Link to comment Share on other sites More sharing options...
sunnysal Posted August 25, 2005 Share Posted August 25, 2005 to be clear...does the comb effect remain the same for these three cases? 1. a mono recording played back via stereo stylus and stereo amplication and speakers setup and... 2. a mono recording played back via a the same stereo setup with the preamp stage set to "mono" 3. a mono recording played back with a mono stylus same stereo setup and the preamp stage set to "mono" does the comb filtering just change form one scenerio to the other? better or worse cases? I find it hard to listen to mono recording with only one speaker since it annoys me to hear music from only one corner (khorns here). I wonder if some of the DSP units (lexicon, etc.) have a "mono" setting that can avoid comb filter effects? thanks for the information, this has been very interesting. I have some old jazz records in mono. regards, tony tony Quote Link to comment Share on other sites More sharing options...
fini Posted August 25, 2005 Share Posted August 25, 2005 I would guess the comb effect might tame really hairy recordings. Quote Link to comment Share on other sites More sharing options...
Allan Songer Posted August 25, 2005 Share Posted August 25, 2005 ---------------- On 8/25/2005 10:20:10 AM garymd wrote: ---------------- On 8/25/2005 8:46:30 AM Allan Songer wrote: English: When you engage the mono switch on your preamp when playing a mono LP it will sound better. ---------------- Exactly! Allan, Didn't you once post a closeup picture of a stylus in a groove and explained what happens with a mono LP vs stereo? I actually understood that and it made perfect sense. Do you still have that somewhere? I have no problem with you guys getting technical. I wish I could follow but there's no way I could even pretend to understand. I'm not sure I have the energy for that today anyway. ---------------- MONO: STEREO: Quote Link to comment Share on other sites More sharing options...
ben. Posted August 25, 2005 Share Posted August 25, 2005 ---------------- On 8/25/2005 10:18:39 AM dragonfyr wrote: ---------------- On 8/25/2005 9:18:18 AM ben. wrote: My point exactly. Douchefyr is overreacting as usual in his pathologically desperate attempts to impress us, which is really strange considering his overt contempt for the members here. ---------------- What Bob described is exactly the classical experiment to demonstrate comb filtering! I apologize for confusing a few of you who only offer attacks. And impress you Ben!? Gee Mr. Wizard. Come now! I would be ecstatic if you simply understood a few of the small words! The problem is not in the signal processing (although there is the potential for issues here if the signals are combined incorrectly), it is in the acoustical playback of multiple channels of the identical signal. And the comb filtering and polar anomalies will still exist, as the two mono signals are not emanating from point sources!!!!!! And this in phase point is just that a point that shifts (generally) vertically and is not coincident for the differing drivers! There are differing degrees of abstraction in the sound 'chain', and while small differences in phase between adjacent pass bands are not critical, the varying acoustic centers of the drivers in multiple speakers also create a problem with comb filtering. It is also the issue directly behind the concept of the coaxial driver - to combine multiple pass band recreation with coincident coherent acoustic origins. Sorry Ben for the emotional distress I caused you, but this is simply time domain acoustics 101! And I am really not too surprised that some choose to remain oblivious to the concept. But then for some, ignorance is indeed bliss. As as far as your "point", if you comb your hair just right, people may not notice! For others it is a real issue that presents a challenge to address in its many layers of complexity.<?xml:namespace prefix = o /> ---------------- I understand the point completely. You're still overreacting. Of course, I own Klipschorns, which completely disregard the issue. Al KLappenberger has done some interesting work in this regard with his ESNs. Quote Link to comment Share on other sites More sharing options...
boomac Posted August 25, 2005 Author Share Posted August 25, 2005 boomac has both mono and stereo copies of several of his favorite LPs. boomac thinks the mono copies sound better in most cases. boomac has a mono/stereo switch on his 299A and his C29. If boomac were to go out today and buy another pre amp, should he avoid all preamps that are void of the mono/stereo mode selector? -------------------------------------------------- Information contained in this thread and several informative e-mails have provided my answer. I will not consider a preamp without a stereo/mono switch. I may consider a second turntable dedicated to mono only recordings, however! Quote Link to comment Share on other sites More sharing options...
Parrot Posted August 25, 2005 Share Posted August 25, 2005 For mono playback, how about using the mono switch on the preamp to eliminate most of the vertical noise AND listening to one speaker only to eliminate comb filtering? Quote Link to comment Share on other sites More sharing options...
Allan Songer Posted August 25, 2005 Share Posted August 25, 2005 ---------------- On 8/25/2005 11:42:15 AM Parrot wrote: For mono playback, how about using the mono switch on the preamp to eliminate most of the vertical noise AND listening to one speaker only to eliminate comb filtering? ---------------- I have done that. I think the sound is much better with BOTH speakers playing. I mean, I tend to sit in the same spot whenever I am seriously listening to music and when you shut down one speaker it's jarring to have the music coming from one side. I suppose I could rotate the speaker and the sofa every time I wanted to listen to a mono record (between 50-60% of the time), but that's really impractical. Plus, I think this whole "comb filtering" thing is being way over-blown--it certainly doesn't annoy me in any way, and I'm pretty picky about how my records sound. Quote Link to comment Share on other sites More sharing options...
pauln Posted August 25, 2005 Share Posted August 25, 2005 I would like to experiment with this... Assuming that the source terminals are standard RCA plugs (two of them in stereo), and assuming that the preamp inputs are likewise, how would one go about converting the stereo source to dual mono before going into the preamp? This is, without shorting anything or starting a fire. Paul Quote Link to comment Share on other sites More sharing options...
CaptnBob Posted August 25, 2005 Share Posted August 25, 2005 I haven't read every word here, but I haven't noticed one of the primary reasons for "the Mono Switch." A mono record will sound better "in mono" because, among other things, you will be cancelling out some random phase and just about all out of phase information - usually distortion and rumble components. I suppose if you really wanted to be hard core about this you could just flip the mono switch and turn the balance control all the way to one side or other and then move the sofa so it's facing the speaker... Quote Link to comment Share on other sites More sharing options...
Parrot Posted August 25, 2005 Share Posted August 25, 2005 Pauln: You would run the left and right output interconnects from the turntable into a y-cord, then connect that y-cord single end into another y-cord's single end (depending on the configuration, you might need a short mono cord or connector between the two y-cords), where it will then divide into two again, but this time each will be the same mixed signal instead of separate left and right. Quote Link to comment Share on other sites More sharing options...
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