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  1. #26
    Audio casualty StevenSurprenant's Avatar
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    Quote Originally Posted by E-Stat View Post
    FR and efficiency, yes. Size and panel configuration, however, are different which most likely yields a slightly different radiation pattern.

    rw
    You are correct. Being a planer and that it sits horizontally, the vertical radiation pattern is greatly reduced. In the horizontal plane, the radiation pattern is much broader, but it still sounds slightly different than the flat panels.
    Last edited by StevenSurprenant; 09-14-2011 at 06:23 AM.

  2. #27
    M.P.S.E /AES/SMPTE member Sir Terrence the Terrible's Avatar
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    Quote Originally Posted by E-Stat View Post
    Who is it who made such a claim? What I did was observe that your sweeping statement (completely independent of the OP's question) that there is NO difference in horizontal dispersion between point source speakers and dipolar panel line sources is most certainly not a correct assertion.
    Majoring in minors a little Ralph. A mistake on a side issue does not change one thing. The OP idea is a bad idea, and there is enough science on the issue to support what I have stated.


    You seem to be caught in a negative feedback loop. While your point has been restated, you have returned to post #11 - to which I responded in advance in post #10. Let's review the facts:

    1. Optimum center channel speaker arrangement is uniquely found in the cinema environment employing vertical symmetry of the three front channels.
    2. Most HT arrangements don't allow for what is known to be ideal.

    Pick your own poison by determining which parameter you choose to optimize over another.

    rw
    1. You do not have to position your center speaker like the cinema environment to be considered optimal for HT. We have already discussed this ad nauseum previously. THX has already found that we are allowed 12" of vertical offset before panning images is disturbed by the offset. A center speaker can be placed under the set as long as it does not violate that rule. So you don't have to choose one over the other.
    Sir Terrence

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  3. #28
    M.P.S.E /AES/SMPTE member Sir Terrence the Terrible's Avatar
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    Quote Originally Posted by Feanor View Post
    I don't understand the implications of this for stereo. Of course we know that the central image in a stereo sound stage consists of the same sound coming from both left and right speakers. Isn't there dispersiona pattern interference in this case? But subjectively the central image -- singer, solo instrument -- sounds pretty good.
    You are correct, there is wave interference with the mono signal. However, we equalize the heck out of that mono signal to give it the clarity and stability it has.
    Sir Terrence

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  4. #29
    Audio casualty StevenSurprenant's Avatar
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    Quote Originally Posted by Sir Terrence the Terrible View Post
    You are correct, there is wave interference with the mono signal. However, we equalize the heck out of that mono signal to give it the clarity and stability it has.
    Just curious...

    Wouldn't it make more sense to correct the phase problem rather than equalize it? It seems to me that when two signals are 180 degrees out of phase that no amount of equalization can compensate for that. Where the phase angle is less than 180 degrees, equalization can have some benefit, but still changes the original waveform to be other than what it was and is more of a reflection of what the recording engineer thinks it should sound like.

  5. #30
    M.P.S.E /AES/SMPTE member Sir Terrence the Terrible's Avatar
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    Quote Originally Posted by StevenSurprenant View Post
    This is more directed at "Sir" ...

    As you are fully aware of, dipole, line arrays, dipole line arrays, box speakers, Multi-driver speakers and about every configuration has its inherent flaws and wave patterns. Throw in different room dimensions and reflecting surfaces, cross talk to both ears from the left and right speakers and you have this incredibly complex wave pattern that is hitting our ears from every direction. It's a wonder that we can hear anything coherent.
    On top of all of this you want to muddy the sound further with a dual center setup?

    "Sir"... Wave interference, combing, lobing, room reflections, speaker directivity, wave patterns from point sources versus line arrays, dipole, bipole, direct radiating speakers, and time alignment is all audio 101. Everyone who has followed this hobby knows this stuff. The only thing that is in contention is the audibility of these affects.
    The audiblity of these effects have been demonstrated with measurements correlated to what we hear.

    Heck, if I wanted to take it too an extreme, I would build a wall between my speakers right up to my face to prevent the right and left speaker from reaching the wrong ear (cross talk). Even though this cross talk has a large effect on soundstaging and more minor effects on wave interference, it is not worth the effort or concern to address.
    Oh brother.......(rolls eyes).

    As for the integration of my speakers, the distances are set, the volumes are set, and I can't tell where one speaker starts and another begins. This is all good and well, but if you want to be critical, the moment that you move out of the sweet spot, all these setting go out of wack. This occurs on your system and mine. The point is that you are being too critical here.
    How was the volume set? I'll ask this again, did you use a SPL meter with pink noise? With 3 speakers across the front, the sweet spot is quite large. It is certainly wider than my couch, so sitting out of the sweet spot is not really possible. This pretty much goes for all of my systems even if they use theater seating and multiple rows of seats.

    As for my center channel, where this all began, I've had it above the TV, below the TV, out in the room, and up against the wall. I've sat closer and further away and it sounds like the sound is coming from it and not the screen. You seem to be telling me to live with it, but I have a choice to do other wise.
    Then you are doing SOMTHING wrong here. I have ten HT/multichannel music system of which only three have the speakers behind the screen. Not one of the other seven exhibit this characteristic. I go to my friends house to watch movies in his hometheater with the center speaker just below the screen, no disassociation of the sound from the screen. When I am mixing soundtracks for DVD and Bluray on a system with the center speaker just below the projection screen, no disassociation of the sound from the screen. THX recommends placing its THX speakers either below or above the screen, and even with its limited vertical coverage, they don't exhibit what you speak of. I can go to each of the 25 sound editing rooms with their center speaker under a flat panel monitor at the studio I work at, and not one of them disassociates the sound from the picture like you mention.

    Something is wrong with this picture, and it has nothing to do with a single center speaker sitting under or over the set.


    While I'm at it, I'll tell you one more thing, which I have no doubt that you already know. Frequencies above about 40 Hz are directional and there is no way to hide where the speaker is. You can't make a single speaker sound like it is coming from the screen, but the effect can be reduced by increasing the distance between you and the screen/speaker. That is the only way except for placing the speaker behind the screen or using multiple speakers.
    Correction, that would be 80hz and up, not 40hz. You really are making stuff up here. I have 7 personal examples that you are completely wrong. THX standards for HT say you are wrong, 25 sound editing rooms say you are wrong on this.

    I have never heard anyone saying that using a single center speaker causes a auditory discontinuity from the picture around the net. You are the first person making this claim.

    I'm not even sure we are arguing the same point. If speaker articulation (clarity) is your point, then you have nothing to worry about. Clarity of sound has always been my goal since I've gotten into this hobby. I've had Quad electrostats, Magnepan, and more, and built present speakers for my 2 channel system using some of the best components money can buy. I can hear a gnat land on a dogs back with either of my systems. I've also listened to some of the best systems available. Still, I can find fault with any system I've owned and listened to.
    Wow..you can hear a gnat land on a dogs back. A little hyperbole on steriod perhaps?

    Two more things...

    My system ( I suppose all) brings the image out into the room as you mentioned that theaters do. regardless of the mechanics, having a deep soundstage behind the speakers is what makes home audio better, it that regard, than a theater. My stereo speakers are about 3 feet from the back wall, but it routinely images 20 feet or more back depending on the source music. My Magnepan speakers are mounted "on the wall" and I still get a very deep soundstage. The imagining is not as precise as my stereo, but I would have to guess that the soundstage is almost as deep. Yet, I do agree that the back wall effects this soundstage.
    The front soundstage of a movie theater is basically a dead zone. The speakers are built into baffles that surpress rearward reflections. That combined with the fact there is acoustical treatment behind the screen as well, there is no way a movie theater can replicate the artificial "reflections" that we get in the home.

    About lifting the center speaker. It has set directly on top of the TV and almost touching the bottom of the screen with the same results. The eye/ear thingy doesn't work for me. I should mention that my speakers are dipole and long, like line arrays, hence floor bounce is less of an issue. Besides, they only go down to about 100Hz. [/quote]

    Have you tried aiming the speaker towards the listening position whether it is above or below the screen?

    Let me ask you a question... Have you ever tried using two speakers for the center channel? Be honest.
    I have never personally tried it, but I have heard a setup that used dual center speakers. I hated the diffusiveness it imparted on dialog. Yes it had more depth than a single speaker, but that is not what we hear in the dubbing stage where soundtracks are created. It is not what we hear when the individual stems are assembled. There is no where in the process that we hear a diffusive dialog except when the dialog is process that way artistically.

    I appreciate your thoughts and I know you are trying to help. However, I'm with E-STAT on this issue.

    The more I learn, the less I know....
    Then both of you are wrong on this one. Sorry..
    Sir Terrence

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  6. #31
    M.P.S.E /AES/SMPTE member Sir Terrence the Terrible's Avatar
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    Quote Originally Posted by StevenSurprenant View Post
    Just curious...

    Wouldn't it make more sense to correct the phase problem rather than equalize it? It seems to me that when two signals are 180 degrees out of phase that no amount of equalization can compensate for that. Where the phase angle is less than 180 degrees, equalization can have some benefit, but still changes the original waveform to be other than what it was and is more of a reflection of what the recording engineer thinks it should sound like.
    Wave interference does not require the signals be 180 degrees out of phase. It is the interaction of the two in phase signals that cause this effect.

    Any spaced speaker system reproducing a mono signal is going to have a notch between 2-4khz because of the distance between our ears. We equalize mono vocals spread between the two speakers to minimize the effects of notching, and give that spread mono signal more stability.
    Sir Terrence

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  7. #32
    Music Junkie E-Stat's Avatar
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    Quote Originally Posted by Sir Terrence the Terrible View Post
    The OP idea is a bad idea, and there is enough science on the issue to support what I have stated.
    Choose you own compromise. And if you want to bring science into the discussion, next time use examples of the kind of speaker used!

    Quote Originally Posted by Sir Terrence the Terrible View Post
    1. You do not have to position your center speaker like the cinema environment to be considered optimal for HT. We have already discussed this ad nauseum previously.
    Indeed. Why is it that you want to discuss preferences again? Apparently you cannot hear what he and I do. Fine. Let it go!

    rw

  8. #33
    Suspended Smokey's Avatar
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    Quote Originally Posted by E-Stat View Post
    You might be surprised how many speakers use series wired components. Aren't you one of the Roger Russell disciples? You do realize that his IDS speaker is wired thusly, right?
    Don't know who Roger Russel is

    If speaker have series wired components, then its specification is designed to have 20 volt rail cross whole combined resisitance to have optimum sound. That would be different from combining two speakers that have optimum sound that was designed to have 20 volts cross each speakers.

    Quote Originally Posted by StevenSurprenant
    As a corollary of what you have said, does that imply that by running speakers in parallel at 4 ohms , the speakers should sound even better? I'm not being facetious, I really don't know. If I were to guess, I would think that, in parallel, there would be 20 volts across both speakers and the amp would just double the current output with no change in sound, except for the 3 db increase by having two speakers instead of one.
    That would be true if amp can handle excessive double current. But most amp can't which mean with excessive current also come excessive distortion. I rather have one speaker with less distortion than two with added distortion. There is old saying in electronic that "there is no free lunch". Which you have to give up something (distortion) to gain something else (volume).

    As an example... P = 20 volts squared/5 ohms = 80 watts for a single speaker, but in series... P = (20/3)squared / 5 ohms = 8 watts per speaker. Does that sound correct?

    Now considering my speakers... They are rated down to 100 Hz at which point I assume the impedance increases, so power is not wasted below that point. I have the speakers set to small and the crossover set to 200 on them so that I have 8 watts of electrical power available to drive each speaker from 200Hz to 16kHz. Besides that, by running three speakers, each additional speaker adds a 3db increase in acoustic power for a 6db increase.
    The formula is correct, but I am not sure adding more speakrs that have the same volume neccesary equal to added 3 db acoustice power since the loudness have not changed. I could be wrong here though so may be somebody else can chime in on this.

    In total, I have 8 watts of electrical power available but the 6db acoustic output gained by using 2 additional speakers gives me the equivalent acoustic power of 32 watts. In other words, I would get the same output running one speaker at a maximum of 32 watts. Does this make sense?
    I don't think that is correct. Since each speaker will have the same volume, adding more speakers with same volume does not equal "linear" added acoustic. Just like having a table fan in a room with 40 db acoustic noise. By adding more table fan to room, the noise level will not increase 3 db per fan since the noise level has not change.

    For example, if you add 10 more fans to room, the noise level will increase slightly, but not 3 db per fan (or the noise level in a room with 10 table fans will make you go deaf ). I hope you see the relation.

  9. #34
    Music Junkie E-Stat's Avatar
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    Quote Originally Posted by Smokey View Post
    Don't know who Roger Russel is
    You haven't missed anything worthwhile.

    Quote Originally Posted by Smokey View Post
    I could be wrong here though so may be somebody else can chime in on this.
    You are mistaken. I get a similar +6db gain from using double New Advents. Half of the acoustic gain comes from using doubles. The other half comes from the Threshold's added power. Which is not even breathing hard driving that load.

    rw

  10. #35
    Audio casualty StevenSurprenant's Avatar
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    Quote Originally Posted by Smokey View Post
    That would be true if amp can handle excessive double current. But most amp can't which mean with excessive current also come excessive distortion. I rather have one speaker with less distortion than two with added distortion. There is old saying in electronic that "there is no free lunch". Which you have to give up something (distortion) to gain something else (volume).
    I checked my amp specs and it supplies approximately 50% more power each time the impedance is halved which is a far cry from doubling. I realize that distortion increases with power output but as long as its below audibility, would it really matter? I only say this because at the volume I play music, I've never had too little power. At present, I use a Trends TA 10.1 digital amp on my stereo which puts out about 6 clean watts. That is more power than I need for the speakers I use and the room it's in. I built my own speakers so I'm guessing that they are about 91db efficient, at least that's what the tweeter is rated at and I don't have it padded down.

    Quote Originally Posted by Smokey View Post
    The formula is correct, but I am not sure adding more speakrs that have the same volume necessarily equal to added 3 db acoustice power since the loudness have not changed. I could be wrong here though so may be somebody else can chime in on this.

    I don't think that is correct. Since each speaker will have the same volume, adding more speakers with same volume does not equal "linear" added acoustic. Just like having a table fan in a room with 40 db acoustic noise. By adding more table fan to room, the noise level will not increase 3 db per fan since the noise level has not change.

    For example, if you add 10 more fans to room, the noise level will increase slightly, but not 3 db per fan (or the noise level in a room with 10 table fans will make you go deaf ). I hope you see the relation
    As I said, my knowledge is limited and I went by what I've heard repeated many times, especially on the speaker building sites. BTW, When I first built my speakers, I was using two SEAS drivers per box and a Newform ribbon, but I was also bi-amping through a digital crossover and so level matching speakers elements was a none issue. However, when I went to passive crossovers, two drivers would overpower the tweeter so I reduced it to one per box which sounds about right. I suppose the point here is that two drivers compared to one really does increase acoustic output. This correlates to what I've read. I didn't measure the increase, so I don't know if the suggested 3db increase is accurate. BTW, the SEAS woofers were wired in parallel.

    Again, thanks for your help.

  11. #36
    Audio casualty StevenSurprenant's Avatar
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    Quote Originally Posted by Sir Terrence the Terrible View Post
    Wave interference does not require the signals be 180 degrees out of phase. It is the interaction of the two in phase signals that cause this effect.

    Any spaced speaker system reproducing a mono signal is going to have a notch between 2-4khz because of the distance between our ears. We equalize mono vocals spread between the two speakers to minimize the effects of notching, and give that spread mono signal more stability.
    If I understand this correctly, the mono signal from, let's say the left speaker hits the left ear, travels across the face, which is about the width of the wave length at 2-4khz, and strikes the right ear. This is repeated with the right speaker. Now each ear has received information that was meant for the opposite ear which has the effect of blurring the image. (I apologize for approaching this in such a simplistic manner, but for me, this is a learning process and I have to crawl before I walk.) What you do is add information to each speaker to cancel out the cross talk across the face. Does this sound right? I didn't know that recording engineers payed any attention to this.

    It's similar to what Carvers "Sonic Hologram" did and more recently, what Edgar Choueiri is doing at Princeton University.

    3D3A Lab at Princeton University

    In my previous post I mentioned putting a wall in the middle of my face to eliminate cross talk, (to which you replied, "Oh brother"). I wasn't kidding, well sort of, but after reading about Choueiri's work I tried using a block of sound absorption to test this idea and yes, it did make a difference. What I discovered was that image quality improved, not enough to sit there with a block of foam strapped to my head, but the improvement was readily apparent.

    Perhaps his technology would be superior to the method you use?

  12. #37
    Audio casualty StevenSurprenant's Avatar
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    Except for perhaps 2 systems I have heard, stereos sound like stereos and cannot be mistaken for the real thing. We constantly bicker over an inferior technology like it's a true representation of what we experience in real life. If we were both blindfolded, I doubt that you or I could be fooled into thinking that either of our systems was the real thing. Blind folded, there would be no question that we were listening to a stereo or surround system. So whats the point?

    Your system is probably better than mine in almost every way, but it still sounds like a stereo/surround system.

    I've heard systems that were so detailed that you could place X's on the floor, both left or right and back, where everyone was standing during the recording, how tall they were, and how far apart they were standing from the performer next to them. In a sense, it was was the closest I have been to true virtual reality. This quality is rare and what most of us listen to is HiFi in comparison. Strangely, many people don't want this level of perfection. They want that warm fuzzy sound that tubes offer or the less distinct and spacious sound that dipoles offer.

    Even with all you knowledge and all the money you've spent on your system, I seriously doubt that your system approaches reality. It probably sounds like a very good surround system according to how someone else decided it should sound.

    This reminds me of Mr. Bose's discovery. When he first set off to create his company he tested different speakers, some attempting accuracy and others that were anything but accurate. What he discovered was that people preferred the sound that he now offers. Surround is the same way. Someone gave the people what they wanted, not accuracy, but excitement.

    In effect, surround systems are anything but accurate. For instance, the center channel that we've been discussing is an abomination. Ninety percent of the time, the sound is coming directly from the middle of the screen. If there are two people talking, left and right, we hear a mono signal in the middle. It's only when, for instance, a door opens far left or right, that we hear any directional clues to what we see on the screen during dialogs. Of course we hear the full stereo spread when there are things like space battles going on. Three center channels across make more sense to me. That way, they can be positioned across the width of the screen and create a stereo effect that is maintained within the screen dimensions. Of course, info could be added to the front speakers to create this same effect, but then that would somewhat negate the use of a center channel.

    I could go on and on about the inferiority of audio systems relative to reality, but you are in this niche where you think there is only one way to do things. All your theories are correct, well most of them, but you are missing the most important part. People have different preferences. You like box speakers and horns, I don't because boxes sound like boxes and horns are irritating. I hear the boxes because I am used to dipoles. To me, that is very distracting. There are some box speakers that do a pretty good job of getting rid of the box sound, but most don't. Most horns are harsh and lack delicacy. That is my preference, but that doesn't mean that everyone should like what I do. I like dipole bass. To me, it is the best quality bass that can be had, but it can't compete with the loudness and dynamics of a box speaker.

    It's odd, sometimes when I am watching a movie and things are banging and clanging, and shaking, I am truly enjoying myself, but then a thunderstorm comes along outside and I sit in awe how wonderful it sounds. It makes me realize how confined and boxy my subwoofer sounds and how small my surround system sounds. Even a movie theater pales in comparison.

    I have told you in the past that by using three speakers that the dialog is clearer, but you have insisted, in so my words, that I am lying to you. Why would I do that? You insist that interference patterns from the speakers reduce the intelligibility of the audio, without even hearing it. You don't take into consideration that I am using dipole planers, or that my room is much smaller than what you are used to, and you have no idea if reflections have been tamed in my room. You know nothing about my setup and yet you insist that using 3 speakers is one of the worse things I could do. In all probability there is some truth in what you say, but the overall effect might just outweigh the negatives. You don't know.

    I learned a lesson many years ago. I used to play chess constantly and as a result I got very good. I never lost. However, one day after winning, my opponent challenged me to a game of checkers. I thought, what the heck, it's much simpler than chess, so I should be able to beat him. Well... I lost every game.

    The point is that you should stick with what you know and what you have experience with.

    I've been down a similar road concerning the Trends TA 10.1 digital amp I use for my stereo. Some critics ran it through its paces and tested it with every piece of test equipment they could get their hands on and in the end, they declare it awful. On the other hand, most reviewers compared it with amps and used it with speakers that most of us cannot afford and in the end, everyone of them declared this amp astounding and was only bettered by true high end equipment. They liked it very much.

    The point is that you could take it apart, test the heck out of it and declare it junk, or... you could just listen.

    Ohh.. About that gnat landing on a dogs back... I might have exaggerated a little.

    "Something is wrong with this picture, and it has nothing to do with a single center speaker sitting under or over the set. "

    Why would I not hear the speaker above or below the screen where it really is? How is it that you don't? Even you said the frequencies over 80hz are directional.

    I'll ask you one more question and then I'll let it drop...

    We, the public, talk amoungst ourselves about movies and music, and we every once in a while, we mention how good a sound track a certain movie or CD has. Even more often, we complain about it. Most of the time, we say nothing because it's adequate.

    Why is it that only a few recording studios produce quality recordings? What do they do different?

  13. #38
    M.P.S.E /AES/SMPTE member Sir Terrence the Terrible's Avatar
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    Quote Originally Posted by StevenSurprenant View Post
    If I understand this correctly, the mono signal from, let's say the left speaker hits the left ear, travels across the face, which is about the width of the wave length at 2-4khz, and strikes the right ear. This is repeated with the right speaker. Now each ear has received information that was meant for the opposite ear which has the effect of blurring the image. (I apologize for approaching this in such a simplistic manner, but for me, this is a learning process and I have to crawl before I walk.) What you do is add information to each speaker to cancel out the cross talk across the face. Does this sound right? I didn't know that recording engineers payed any attention to this.

    It's similar to what Carvers "Sonic Hologram" did and more recently, what Edgar Choueiri is doing at Princeton University.

    3D3A Lab at Princeton University
    No not quite. When we are monitoring the mix, we are constantly listening to what happens to the sound as various tracks get mixed in. Bass instruments mixed down the middle are nothing to worry about, but when you get to instruments or voices nearing 1K, you have to start using EQ to prevent the voices from sounding hollow as a result of the notch. We don't try to fill in the notch, it would just make it worse. We just try to minimize its audible effect.

    In my previous post I mentioned putting a wall in the middle of my face to eliminate cross talk, (to which you replied, "Oh brother"). I wasn't kidding, well sort of, but after reading about Choueiri's work I tried using a block of sound absorption to test this idea and yes, it did make a difference. What I discovered was that image quality improved, not enough to sit there with a block of foam strapped to my head, but the improvement was readily apparent.

    Perhaps his technology would be superior to the method you use?
    He is addressing the playback side, and I am addressing the recording mixing side. You are referring to interaural crosstalk on the playback side, and that can be eliminated or at least lessened by including a center speaker for mono signals.
    Sir Terrence

    Titan Reference 3D 1080p projector
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    6 custom CAL amps for subs
    3 custom 3 way horn DSP hybrid monitors
    18 custom 3 way horn DSP hybrid surround/ceiling speakers
    2 custom 15" sealed FFEC servo subs
    4 custom 15" H-PAS FFEC servo subs
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  14. #39
    M.P.S.E /AES/SMPTE member Sir Terrence the Terrible's Avatar
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    Quote Originally Posted by E-Stat View Post
    Choose you own compromise. And if you want to bring science into the discussion, next time use examples of the kind of speaker used!
    It really does not matter what speaker is used, the penalty is exactly the same. That's science as well!


    Indeed. Why is it that you want to discuss preferences again? Apparently you cannot hear what he and I do. Fine. Let it go!

    rw
    Personally, I don't really care about what you and him do, its not even relevant. No matter what speaker technology is deployed, the effect is exactly the same. Perhaps you need to follow your own advice.
    Sir Terrence

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  15. #40
    Suspended Smokey's Avatar
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    E-Stat and StevenSurprenant,

    I found the formula for how much acoustic power (db) changes with added source that have the same volume. It is rather interesting.

    Formulas: Δ L = 10 log n where
    Δ L = level difference; n = number of equal loud sound sources.

    If we have two sources of the same volume, the loudness acoustic gain is 3 db. But if we have three sources of same volume, the acoustic gain is only 4.8 db. And if we have four, the acoustic gain is 6.0. Here is table:

    (Number of n equal loud sound sources) = (Level increase Δ L in dB)

    1 0 = 0 db
    2 = 3.0 db
    3 = 4.8 db
    4 = 6.0 db
    5 = 7.0 db
    6 = 7.8 db
    7 = 8.5 db
    8 = 9.0 db
    9 = 9.5 db
    10 = 10.0 db
    12 = 10.8 db
    16 = 12.0 db
    20 = 13.0 db

    As you can see, as we add more sources of equal volume, the changes in acoustic power changes less and less

  16. #41
    Suspended Smokey's Avatar
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    Quote Originally Posted by StevenSurprenant View Post
    I At present, I use a Trends TA 10.1 digital amp on my stereo which puts out about 6 clean watts. That is more power than I need for the speakers I use and the room it's in. I built my own speakers so I'm guessing that they are about 91db efficient, at least that's what the tweeter is rated at and I don't have it padded down.
    No matter how sensetive your speakers are, 6 watts of power is definitely not enough. Alot of poeple associate more power with more loudness which is not true because amp also have to have dynamic headroom which can go well above 100 watts.

    If you don't have dynamic headroom to take of music spikes, the result would be excessive distortion better know as Total Harmonic Distortion (THD). That is why low power amps always have high THD

  17. #42
    Music Junkie E-Stat's Avatar
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    Quote Originally Posted by Smokey View Post
    As you can see, as we add more sources of equal volume, the changes in acoustic power changes less and less
    The other variable, however, is the frequent increase of amplifier power driving lower impedance. In my case, the wattage doubles with the halving of impedance providing the cumulative +6db effect.

    I first discovered these two factors in high school back in '74 when I drove my first pair of double Advents with a Crown D-150. Its power also doubled into half the impedance load. Which worked great in the high school gym for the Miss RHS Pageant where they were used as the sound system for the talent.

    rw

  18. #43
    Music Junkie E-Stat's Avatar
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    Quote Originally Posted by Smokey View Post
    That is why low power amps always have high THD
    Ridiculous. Low powered First Watt amplifiers most certainly do not have high THD even with zero NFB.

    rw

  19. #44
    Audio casualty StevenSurprenant's Avatar
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    Quote Originally Posted by Smokey View Post
    E-Stat and StevenSurprenant,

    I found the formula for how much acoustic power (db) changes with added source that have the same volume. It is rather interesting.

    Formulas: Δ L = 10 log n where
    Δ L = level difference; n = number of equal loud sound sources.

    If we have two sources of the same volume, the loudness acoustic gain is 3 db. But if we have three sources of same volume, the acoustic gain is only 4.8 db. And if we have four, the acoustic gain is 6.0. Here is table:

    (Number of n equal loud sound sources) = (Level increase Δ L in dB)

    1 0 = 0 db
    2 = 3.0 db
    3 = 4.8 db
    4 = 6.0 db
    5 = 7.0 db
    6 = 7.8 db
    7 = 8.5 db
    8 = 9.0 db
    9 = 9.5 db
    10 = 10.0 db
    12 = 10.8 db
    16 = 12.0 db
    20 = 13.0 db

    As you can see, as we add more sources of equal volume, the changes in acoustic power changes less and less
    That's good to know and very interesting. Thank you!

  20. #45
    Audio casualty StevenSurprenant's Avatar
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    Quote Originally Posted by Smokey View Post
    No matter how sensetive your speakers are, 6 watts of power is definitely not enough. Alot of poeple associate more power with more loudness which is not true because amp also have to have dynamic headroom which can go well above 100 watts.

    If you don't have dynamic headroom to take of music spikes, the result would be excessive distortion better know as Total Harmonic Distortion (THD). That is why low power amps always have high THD
    I understand what you're saying and it's true, but keep in mind that it depends on how loud a person listens. I designed my system for ultra clarity, at least that was my goal, and so I can listen at very low levels and still hear everything. Also, the system is in a very small room which also allows me to reduce the volume. I know this doesn't mean much, but I normally run my volume control at 1/4 of the max. I tried the system in a larger room and there wasn't enough power.

    When I had my Quads I was pushing them with a Mark Levinson 331 which was rated at 130 watts per channel. Of course, power wasn't a problem, but personally, I think the Trends TA sounds much better. The last time I said that, the guy got mad at me and told me, in so many words, that I was out of my mind. I don't think the ML was the correct choice for my speakers, that's all. I think the Pass Labs Aleph 3 at 30 watts would have been a better choice.

    I remember many years ago listening to a ML system driving Wilson Watt/Puppies and thought to myself that it was decent, but then I found another store driving the same speakers with a Pass Labs amp similar to the Aleph 3 except it put out 45 watts. The difference was astounding. Comparatively speaking, the ML system sound flat like wall paper. ML products are great, but system matching is always a must. Anyway, the sound stage with the Pass Labs was so defined that I could have walked between the performers on the stage. I remember seeing (actually hearing) the drummer placed way back in the room on the right. This was the first time (only time) that I thought that there was too much separation between instruments and performers. It was surreal. The space between the performers was as defined as the performers themselves.

    I suppose that what I'm trying to say is that more power is always good, but there are some things that transcend pure power.

    The soundstage I get is nowhere near what I heard at that store, but it has a certain magic. I would go for a bigger amp, but I would not trade off the sound quality. There are better amps, but at what price?

    Read this...

    6moons audio reviews: Trends Audio TA-10

    Also

    TA-10 Modifications

    I've supplied a graph of the output power just in case you're interested. No need to click on the links if you're not. I would guess that the Trends amp would be similar to the Super-T on the graph.
    Attached Thumbnails Attached Thumbnails Center channel Impedance.-trends.jpg  

  21. #46
    Audio casualty StevenSurprenant's Avatar
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    Quote Originally Posted by E-Stat View Post
    The other variable, however, is the frequent increase of amplifier power driving lower impedance. In my case, the wattage doubles with the halving of impedance providing the cumulative +6db effect.

    I first discovered these two factors in high school back in '74 when I drove my first pair of double Advents with a Crown D-150. Its power also doubled into half the impedance load. Which worked great in the high school gym for the Miss RHS Pageant where they were used as the sound system for the talent.

    rw
    Nothing is ever simple, is it? Makes a person think! Arghhh...

  22. #47
    Audio casualty StevenSurprenant's Avatar
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    Quote Originally Posted by Sir Terrence the Terrible View Post
    No not quite. When we are monitoring the mix, we are constantly listening to what happens to the sound as various tracks get mixed in. Bass instruments mixed down the middle are nothing to worry about, but when you get to instruments or voices nearing 1K, you have to start using EQ to prevent the voices from sounding hollow as a result of the notch. We don't try to fill in the notch, it would just make it worse. We just try to minimize its audible effect.

    He is addressing the playback side, and I am addressing the recording mixing side. You are referring to interaural crosstalk on the playback side, and that can be eliminated or at least lessened by including a center speaker for mono signals.
    I guess that I don't get it. It seems that we are talking about the same thing, yet somehow, it's different. I understand how the same signal reaching across the face causes a loss of imaging, but I don't quite understand what causes the notch.

    The only way I can understand this is to think that the left signal reaching the right ear is out of phase with the sound from the right speaker and when the two signals combine they create peaks and troughs, hence, distorting the sound. If I understand it correctly, what we hear is a softening (less distinct) of the sound .

    Just thinking...

    What's different that you do compared to Choueiri is that you ( I assume) equalize both channels at the same time whereas, Choueiri actually adds information to each opposite channel to cancel the cross talk.

    It seems that Choueiri's method would better solve the problem except for one thing, his method is highly dependent on listening position since there is a timing/amplitude factor involved in when the signals reach the ears and moving away from that "sweet spot" ruins that timing/amplitude.

    You method is a compromise that maintains a more even response regardless of the listening position.

    Am I beginning to understand you?

    Thanks

  23. #48
    Suspended Smokey's Avatar
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    Quote Originally Posted by E-Stat View Post
    The other variable, however, is the frequent increase of amplifier power driving lower impedance. In my case, the wattage doubles with the halving of impedance providing the cumulative +6db effect.
    But where did extra 3 db came from?

    If we halv the impedance (add another speaker in parallel), wouldn't double power be needed to keep same volume as when there was only one speaker. Also remember that relation between power output and acoustic power out is not linear as for every 3 db increase in loudness require doubling the power.

    For example if a speaker that is connected to 25 watt amp put out 80 db loudness, then to have:

    83 loudness = 50 watts
    86 db loudness = 100 watts
    89 db loudness = 200 watts
    92 db loudness = 400 watts

    Ridiculous. Low powered First Watt amplifiers most certainly do not have high THD even with zero NFB.
    I went to their web site to look at First Watt amplifiers specifications. If you look at their amp's THD, you will see that %THD are only for 1 watt output. I would like to know what is THD for full power output. I bet it does not look pretty

    Quote Originally Posted by StevenSurprenant
    I understand what you're saying and it's true, but keep in mind that it depends on how loud a person listens. I designed my system for ultra clarity, at least that was my goal, and so I can listen at very low levels and still hear everything. Also, the system is in a very small room which also allows me to reduce the volume. I know this doesn't mean much, but I normally run my volume control at 1/4 of the max.
    I mentioned before that alot of poeple associate loudness with power

    Loudness and power are not directy related. Even 1 watt of power can make a speaker pretty loud. The extra power is not for loudness, but rather for cleanly reproducing transient peaks. Check out this web site that explain it better. I quote the most important part:

    "It is obvious from the example above that adequate amplifier power is necessary to provide an accurate portrayal of music. This is especially true when attempting to reproduce realistic levels, or when driving inefficient speakers. However, even small efficient speakers may require copious amounts of power to cleanly reproduce transient peaks. In the final analysis, it is difficult to have too much power. While a small amplifier of only a few watts output can produce surprising average loudness, the dynamic peaks will usually suffer."

    The Relationship of Voltage, Loudness, Power and Decibels

  24. #49
    Music Junkie E-Stat's Avatar
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    Quote Originally Posted by Smokey View Post
    But where did extra 3 db came from?
    3 db from acoustic gain. 3 db from a doubling of power. If you had a transformer driven amplifier whose output was consistent, then you would get 3 db from merely doubling the speakers. Additionally, you are now running twice the power to double the speakers.

    Quote Originally Posted by Smokey View Post
    If we halv the impedance (add another speaker in parallel), wouldn't double power be needed to keep same volume as when there was only one speaker.
    Nope. Re-read you own source!

    "If we have two sources of the same volume, the loudness acoustic gain is 3 db."

    Before the Sound Labs, I used Acoustat 2+2s which had four panels per speaker. There was also a 1+1 which used the exact same transformer for driving half the number of panels. While there were different taps to the bass transformer to optimize the frequency response, the 2+2 was twice as efficient having double the panel area. 400 watts into a double pair of Advents has 3db more output than 400 watts into a single pair.

    Quote Originally Posted by Smokey View Post
    Also remember that relation between power output and acoustic power out is not linear as for every 3 db increase in loudness require doubling the power.
    Or having two sources with the same power! You still don't get it?

    Quote Originally Posted by Smokey View Post
    I went to their web site to look at First Watt amplifiers specifications. If you look at their amp's THD, you will see that %THD are only for 1 watt output.
    You didn't look very far. Try again.


    Quote Originally Posted by Smokey View Post
    I would like to know what is THD for full power output. I bet it does not look pretty
    And you would be wrong. Again.

    Quote Originally Posted by Smokey View Post
    The extra power is not for loudness,
    At least you are consistently wrong. I assure you that the measurable levels I get at 400 watts is much higher than for 4 watts. You can teach me nothing in this regard. I know exactly the difference between what the Stasis output is at 0 db and at -20 db.

    rw
    Last edited by E-Stat; 09-16-2011 at 08:45 PM.

  25. #50
    Audio casualty StevenSurprenant's Avatar
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    Quote Originally Posted by Smokey;368846
    I mentioned before that alot of poeple associate loudness with power :D

    Loudness and power are not directy related. Even 1 watt of power can make a speaker pretty loud. The extra power is not for loudness, but rather for cleanly reproducing transient peaks. Check out this web site that explain it better. I quote the most important part:

    "It is obvious from the example above that adequate amplifier power is necessary to provide an accurate portrayal of music. This is especially true when attempting to reproduce realistic levels, or when driving inefficient speakers. However, even small efficient speakers may require copious amounts of power to cleanly reproduce transient peaks. In the final analysis, it is difficult to have too much power. While a small amplifier of only a few watts output can produce surprising average loudness, the dynamic peaks will usually suffer."

    [url=http://www.gcaudio.com/resources/howtos/voltageloudness.html
    The Relationship of Voltage, Loudness, Power and Decibels[/url]

    I understand fully and have two examples to prove your point...

    A long time ago, before man roamed the Earth, a friend had speakers that had peak indicators on them (little lights that would light up when the power reached the maximum that the speakers were rated at)...(cool huh!). I'm not sure what the limits were that would trigger these lights, but I assume it was over 100 watts.

    His amp also had meters (VU) on it. So one day, he was cranking it for the enjoyment of himself and his neighbors and the lights on his speakers were flashing, but when he looked at his power meters on his amp, it was only showing about 30 watts. He was confused and so I explained the difference between continuous power and peak power and that the speaker lights were indicating peak power while the amp was showing continuous power.

    Thinking in round numbers, let;s assume that his amp was putting out 120 watts peak and 30 watts continuous. This is a headroom of 6db (30/60/120). According the the article that you posted, this is a 4 times increase in power and only 50% increase in loudness.

    Here is a link to relative loudnesses that I will use as a reference (I assume these numbers are representative of continuous power). Sound levels (dB) and relative loudness of typical noise sources in indoor and outdoor environments.

    Using the numbers for "Moderately loud - Living room music" , it shows 76db. Since my speakers are 91db efficient. This means it takes about 1/5 of a watt to drive my speakers to this volume (76db). Since my amp is about 6 watts, this makes my maximum volume about 97db at 4 watts. We'll just toss the last 2 watts out since it won't add any appreciable loudness. This gives me a headroom from 76db to 97db of 21db. Also, the peak of 97db is almost equal (according the the link I sent) to a "Bell J-2A helicopter at 100 ft . . . 100 dB"

    That seems pretty respectable, don't you think? From these numbers, it seems, to me, that 6 watts is enough to create decent music. Of course, if I turn up the volume, the amount of relative headroom shrinks.

    If you think it will only play a low volumes, you couldn't be more mistaken. Have you ever watched the movie "Lost in Space"? It begins with a space battle where the good guys are fighting the Genteks over a space gate they are constructing. I play that movie at a realistic volume. Even a movie theater doesn't get much louder.

    Of course, listening distance and room size figure into all of this and believe me, it is minimal. Out of necessity, my stereo is in a small room. It's a funny thing, I was going to give up on this audio thing because I didn't have a suitable room to set it up in, but as it turned out, I couldn't be more pleased.

    The other story (much shorter) is that in the 70's I owned a pair of Phase Linear dipole speakers and a receiver rated at 80 watts. The speakers were rated at (if I remember correctly) 350 watts. While I loved the clarity of these speakers I also loved the dynamics and loudness that my friends box speakers put out. So, one day cranked my speakers as loud as I could to see if I could get them to sound like my friends speakers. Well I couldn't (it's the nature of dipole), but in the process, I blew out one of my drivers. I was surprised since my speakers were rated to take much more power. That's when I learned that too little power was worse than too much.

    However, and I'm not sure about this, at 6 watts which is way below what my present speakers can handle, I don't think I could blow a speaker even if I ran my amp into full clipping for a prolonged period of time. I'm not going to test this!

    Anyway, thanks again. I really enjoy being forced to think about things.

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