Jeff Matthews Posted October 23, 2005 Share Posted October 23, 2005 Dr. Who, you too seem to have savy, coupled with the right equipment to do a simple test for upload. Puting aside the issue of calculating the speed of sound, let's focus on audibility of the "two-tap" phenomenon. Can you put together single tone LF (but at the upper -not lower - end of the KHorn woofer's handling ability) tracks with increasing delays until you think you've found an audible echo? If so, upload it and tell us what the delay factor was. I think this would accurately tell us whether the relative pathways for woofers vs. mid-ranges in this model have any audible significance. Quote Link to comment Share on other sites More sharing options...
DrWho Posted October 23, 2005 Share Posted October 23, 2005 Hmmm, seems I'm talking about yet another thing (more along the lines of the beats)... Let me try an example: A = 440Hz B = 540Hz When A and B are playing at the same time, they sum to a complex frequency, C (that doesn't look like a sine wave). If we perform a fourier transform on the sum C, we will notice that there are measured frequencies at 100Hz (the beat or difference tone) and 980Hz (the combination tone)...the cool thing is we will also hear these two extra tones (so its not just something that we measure). The point I was trying to make is that the 100Hz and 980Hz "combination tones" will change based on the relative phase and amplitude of Tone A and Tone B. All of the tones will remain the same, but the relative amplitudes of each at any point in time will be different. Whenever A and B are not playing at the same time, we no longer have the "combination tones" or the summed complex frequency, C. We have A playing and then B playing. Let's say we are playing a sound over a time period where our ears wouldn't be able to distinguish between two different sounds. I think it is obvious that A and B playing at the same time over that time period will sound different than if the first half was A and the second half was B, even though both cases will be percieved as a single pulse of sound. The difference is in the combination tones. If our song is supposed to play two frequencies at the same time, then our khorn is going to change the single note into a different sound. The higher frequency will arrive first by itself for 7ms (no combination tones even though they should be there), then for a short segment of time we will hear both at the same time (but the phase between A and B will be different and that implies a new phase and amplitude for the combination tones), and then finally we will hear the lower frequency by itself for 7ms (again no combination tones that should be there). By the time our pulse is finished, the khorn will also have stretched the note out an extra 7ms! I have no problem saying that we will still percieve this as a single pulse of sound, but the timbre of the note will certainly be different. Now if we were to increase the time-delay difference, there is a point where the tap-dancing phenomenon starts to occur where we then percieve two seperate tone bursts instead of a single one. The comb-filtering that occurs because two drivers are playing the same frequency is yet another factor to worry about....but one that gets minimized from Al's super steep crossovers. The slope of the crossover however is not going to directly affect the combinational tone difference due to the time-delay. And as Al mentioned, two drivers playing different frequencies do not exhibit any comb-filtering effects. To differentiate the effects between the two, we can limit measurements to frequencies outside the crossover passband (where comb-filtering isn't an issue). Quote Link to comment Share on other sites More sharing options...
DrWho Posted October 23, 2005 Share Posted October 23, 2005 Dr. Who, you too seem to have savy, coupled with the right equipment to do a simple test for upload. Puting aside the issue of calculating the speed of sound, let's focus on audibility of the "two-tap" phenomenon. Can you put together single tone LF (but at the upper -not lower - end of the KHorn woofer's handling ability) tracks with increasing delays until you think you've found an audible echo? If so, upload it and tell us what the delay factor was. I think this would accurately tell us whether the relative pathways for woofers vs. mid-ranges in this model have any audible significance. My software at home only allows 9ms intervals so I'm not sure how feasible that would be. Besides, the khorn doesn't have the "two-tap" phenomenon. There is a minimum time-delay where the "two tap" occurs. For time periods shorter than this interval, the percieved intermodulation distortion is still going to change (as a function of the time-delay). I have always hesitated referring to it as "intermodulation distortion" because distortion is always implied as a bad thing, but the intermodulation distortion is vital to the sound of live instruments. I've always heard IMD used when measuring the performance of a particular driver (every driver has some form of harmonic distortion, which will in turn produce intermodulation distortions) http://www.audiovideo101.com/dictionary/im-distortion.asp Hopefully the analogy (A, then A+B, then makes it clear that the "average" intermodulation distortion over the time period will be different than the original (A+B only). We still hear it as one note, but our ears are going to hear the "average". How audible is it? Just listen to the demo [] (every drum hit sounds like one hit, but the timbre changes) Quote Link to comment Share on other sites More sharing options...
Jeff Matthews Posted October 23, 2005 Share Posted October 23, 2005 DrWho, very well-reasoned and explained. I get it now that you use the A,A+B,B approach. I tried to notice something from the drums in your uploads. But with that guitar, keyboard and bass, etc., going all at the same time, I can't really grasp it. Got something with say, just the drums? Quote Link to comment Share on other sites More sharing options...
tofu Posted October 23, 2005 Author Share Posted October 23, 2005 this glue takes way too long to dry Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted October 23, 2005 Share Posted October 23, 2005 Who, I don't understand why you are persuing the sum of two tone frequencies through the Khorn woofer idea. A horn loaded speaker has very low intermod distortion. It's under 1% even at high volume levels. The IM distortion of a direct radiator is a lot worse. Intermod will NOT generate an echo. It just sounds bad! I have done intermod tests at midrange frequencies and I will post the plots to show that there is very little distortion generated by a horn speaker if you care to see them. The diaphragm motion is also very low compared to a direct radator. The large diapgragm motion COULD cause intermod in the form of doplar shift as a high frequency source (the cone) is move to you and away from you by the lower frequency of the two. Again, the horn reduces the diaphragm motion and therefor the doplar distortion and all the other types of distortion. I really think you are barking up the wrong tree!BTW: The distortion caused by doplar would be frequency modulation, not IM distortion. I believe that, plus IM distortion is what PWK called "total modulation distortion" in his papers. AL K. Quote Link to comment Share on other sites More sharing options...
DrWho Posted October 23, 2005 Share Posted October 23, 2005 It's not the intermodulation distortion of the bassbin that is the problem! The IMD ratings for speakers are measuring the amounts of IMD present that are directly associated with the harmonic distortion of the driver. In the issue of time-delay I'm not even talking about the drivers. The link I posted explains this better. Any source of sound where more than one frequency is present exhibits intermodulation distortion. It's the intermodulation distortion between the delayed frequencies and undelayed frequencies that is changing as a function of the time-delay. (in other words, the combinational tones between the delayed frequencies and undelayed frequencies change as a function of the amount of time-delay). I tried so hard to not refer to it as intermodulation distortion because it instantly gets associated with a driver spec, but its not the driver specs that I'm talking about. Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted October 23, 2005 Share Posted October 23, 2005 Who, Well, here are the plots anynow. Ready or not! They are of the K500 horn and two different drivers on the Trachorn. The test was done at 100 dB SPL. Notice the intermod products (F2 + - F1) are about 45 dB down! A hoorn woofer would be just as clean. No echos or significant IMD here! Al K. Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted October 23, 2005 Share Posted October 23, 2005 Who, You are looking for intermod products generated by two sources that are out of time with each other, but, IM distortion is casue by nonlinear systems like amplifiers and speakers. Where is the nonlinearity? Are you assuming the air between you and the speakers is nonlinear? Are your ears non linear? If you ears are nonlinear, everyhting you ever heard in your life must be distorted! Your ears is the "given" in this discussion. The echo is cassued by two different path lengths just like the echo of a sound bouncing off a far wall. It is purely propogation time, nothing more! Al K. Quote Link to comment Share on other sites More sharing options...
DrWho Posted October 23, 2005 Share Posted October 23, 2005 Here's the time delay with a drum segment. Keep in mind that it's the same 2000Hz crossover. It's interesting to note how much different the low end sounds, yet it's so far away from the crossover point of delay. And at 9ms you can just hear the kick drum doubling up too. Drum Time Delay.zip Quote Link to comment Share on other sites More sharing options...
Jeff Matthews Posted October 23, 2005 Share Posted October 23, 2005 Here I go, again being an unseasoned "audiophile" trying to intelligently digest this theory. But.......... Dr Who, you gave the A, A+B, B approach. I get it. However, if we are saying that a time-delay (phase shift?) has no effect on the frequency or tone, then where does your approach come into play? If, for example, a 400hz note is projected through the speaker. A is the mid-range blowing 400hz, A+B are the mid-range and woofer blowing 400hz, and B is the woofer blowing 400hz. Now, let's separate the phase shift for a moment, and focus only on the note. Doesn't a 400hz note sound the SAME, whether it is projected through a mid-range or woofer? I would think so. 400hz is 400hz is 400hz. So, bearing in mind that we are only dealing with a single, fixed note for this purpose, it seems A is the mid blowing 400hz. A+B means the woofer just joined in at the same tone, and B is the woofer dragging behind at the same tone at the end. So, it should sound like one continuous note, and the only difference would be that its total length is 7ms longer. That said, I can see where the phase-shift would cause a set of repeated gaps and bleedovers through a song, but only in theory and not to our audible reality. Let's say the guitar and bass are supposed to come in together. We hear the guitar come in through the mid. Next, we hear the bass. Let's assume now that the guitar and bass are supposed to stop at the same time. The bass would then bleed over. Of course, this assumes NO common playing of the same frequency within the single instrument through BOTH the mid and the woofer (i.e., the bass only comes in through the woofer). If there is commonality, it seems the gaps and bleeds are reduced. Am I right so far? If so, I can't imagine you'd hear any difference because in the real world, I don't know of a guitarist who can keep up with a bassist to within 7ms, and vise versa. That goes for all instruments. That also goes for changes in tunes within the same instrument that could THEORETICALLY transverse from mid to woofer IN A MUTUALLY-EXCLUSIVE manner. Once the tone played by a single instrument crosses into the overlap and is played by both the mid and woofer, there would be no phase shift. So, it would appear the "real" issue is the delayed starts and stops WITHIN WHAT SHOULD BE ONLY A SINGLE HARMONY. Like I said, I know of no musician who can keep up with other musicians to within 7ms. Right or wrong? Quote Link to comment Share on other sites More sharing options...
Jeff Matthews Posted October 23, 2005 Share Posted October 23, 2005 Here's the time delay with a drum segment. Keep in mind that it's the same 2000Hz crossover. It's interesting to note how much different the low end sounds, yet it's so far away from the crossover point of delay. And at 9ms you can just hear the kick drum doubling up too. I don't hear it. I'm a drummer, and I can't hear it. I'm not trying to go into credentials by saying I am a drummer, but I generally tend to focus on drums in a tune. Those echos are in both versions. They are part of the song. Quote Link to comment Share on other sites More sharing options...
Deang Posted October 23, 2005 Share Posted October 23, 2005 All this fretting over 7 millionths of a second. I'll be kind and just not say anything more. Quote Link to comment Share on other sites More sharing options...
DrWho Posted October 23, 2005 Share Posted October 23, 2005 Who, You are looking for intermod products generated by two sources that are out of time with each other, but, IM distortion is casue by nonlinear systems like amplifiers and speakers. Where is the nonlinearity? Are you assuming the air between you and the speakers is nonlinear? Are your ears non linear? If you ears are nonlinear, everyhting you ever heard in your life must be distorted! Your ears is the "given" in this discussion. The echo is cassued by two different path lengths just like the echo of a sound bouncing off a far wall. It is purely propogation time, nothing more! I feel like we're struggling with terminology here...I am using intermod distortion interchangeably with combination tones. You are referring to intermod distortion measurements as they pertain to harmonic distortion. Any two frequencies when played at the same time also create sum and difference tones. The set of all these tones can be referred to as intermodulation distortion: "Intermodulation distortion begins with additional frequencies being produced by the sum and difference (addition and subtraction) of two original frequencies. For instance, two frequencies of 2 kHz and 8 kHz may have been produced by an audio system. Intermodulation distortion would create two additional signals at 10 kHz (the sum or addition of 2 and 8 kHz) and 6 kHz (the difference between the numbers or subtraction of 2 from 8 kHz)." http://www.audiovideo101.com/dictionary/im-distortion.asp The measurements to which you refer stem from the harmonic distortion of the nonlinear devices to which you refer: "Each of these new signals, the first parts of intermodulation distortion, would then develop harmonics of their own (creating harmonics from 6 kHz of 12 kHz, 18 kHz and so on while producing harmonics of 10 kHz at 20 kHz, 30 kHz and son on). To further confuse the issue and add even more distortion, these harmonics (the harmonics created from the sum and difference frequencies of the original two frequencies) would then create their own sum and difference distortions (for example, the first harmonics located at 12 kHz and 20 kHz would create a sum frequency of 32 kHz and a difference frequency of 8 kHz)." http://www.audiovideo101.com/dictionary/im-distortion.asp If I'm incorrectly using the term "IMD" then by all means interchange it with the concept of combination tones....which are always there. (they don't require a nonliner system). The point is that the combination tones are changing with time (A, A+B, and even though it happens in a timespan that is recognized as a single instance, the percieved timbre still changes. http://www.audiovideo101.com/dictionary/im-distortion.asp'> Quote Link to comment Share on other sites More sharing options...
Jeff Matthews Posted October 23, 2005 Share Posted October 23, 2005 All this fretting over 7 millionths of a second. I'll be kind and just not say anything more. 7 thousandths. But point well taken. That's the point I am making - that 7 thousandths doesn't matter. But I like to hear the theory and to hear somebody try to convince me it does... does.. does... does. Quote Link to comment Share on other sites More sharing options...
Jeff Matthews Posted October 23, 2005 Share Posted October 23, 2005 The point is that the combination tones are changing with time (A, A+B, and even though it happens in a timespan that is recognized as a single instance, the percieved timbre still changes. http://www.audiovideo101.com/dictionary/im-distortion.asp'> Okay, read my prior thread about 400hz is 400hz is 400hz and no musician is capable of keeping up to a 7ms degree of accuracy. If this is the difference you refer to as a difference in "perceived timbre," I still think it's imperceptible. Quote Link to comment Share on other sites More sharing options...
DrWho Posted October 23, 2005 Share Posted October 23, 2005 Here I go, again being an unseasoned "audiophile" trying to intelligently digest this theory. But.......... Dr Who, you gave the A, A+B, B approach. I get it. However, if we are saying that a time-delay (phase shift?) has no effect on the frequency or tone, then where does your approach come into play? If, for example, a 400hz note is projected through the speaker. A is the mid-range blowing 400hz, A+B are the mid-range and woofer blowing 400hz, and B is the woofer blowing 400hz. Now, let's separate the phase shift for a moment, and focus only on the note. Doesn't a 400hz note sound the SAME, whether it is projected through a mid-range or woofer? I would think so. 400hz is 400hz is 400hz. So, bearing in mind that we are only dealing with a single, fixed note for this purpose, it seems A is the mid blowing 400hz. A+B means the woofer just joined in at the same tone, and B is the woofer dragging behind at the same tone at the end. So, it should sound like one continuous note, and the only difference would be that its total length is 7ms longer. That said, I can see where the phase-shift would cause a set of repeated gaps and bleedovers through a song, but only in theory and not to our audible reality. Let's say the guitar and bass are supposed to come in together. We hear the guitar come in through the mid. Next, we hear the bass. Let's assume now that the guitar and bass are supposed to stop at the same time. The bass would then bleed over. Of course, this assumes NO common playing of the same frequency within the single instrument through BOTH the mid and the woofer (i.e., the bass only comes in through the woofer). If there is commonality, it seems the gaps and bleeds are reduced. Am I right so far? If so, I can't imagine you'd hear any difference because in the real world, I don't know of a guitarist who can keep up with a bassist to within 7ms, and vise versa. That goes for all instruments. That also goes for changes in tunes within the same instrument that could THEORETICALLY transverse from mid to woofer IN A MUTUALLY-EXCLUSIVE manner. Once the tone played by a single instrument crosses into the overlap and is played by both the mid and woofer, there would be no phase shift. So, it would appear the "real" issue is the delayed starts and stops WITHIN WHAT SHOULD BE ONLY A SINGLE HARMONY. Like I said, I know of no musician who can keep up with other musicians to within 7ms. Right or wrong? The problem comes into play when we have a 60Hz frequency on the woofer and a 4kHz frequency on the squaker, not when a single tone is being played. In other words, every frequency below 400Hz is going to be delayed relative to any frequency above 400Hz (ignoring the pass band region of the crossover). All of these frequencies are going to NOT interract for the first 7ms and last 7ms of the sound. In the middle, the phase between all the frequencies will be different than if both sounds arrived at the same time...so in the middle section the combination tones are going to have a different amplitude structure. Btw, here's another version of the drum delay without all the rain sticks in the front (so it starts right on the tribal drum hit). This should make it easier to AB between the two because you can just hit next right away and hear the difference quicker. Drum Time Delay short.zip Quote Link to comment Share on other sites More sharing options...
Deang Posted October 23, 2005 Share Posted October 23, 2005 Yeah, then how come it says 'milli'? I mean, isn't that like the first five letters in 'million'? Of course, thousandths -- and this changes everything. I still think it's ridiculous. Quote Link to comment Share on other sites More sharing options...
Jeff Matthews Posted October 23, 2005 Share Posted October 23, 2005 Yeah, then how come it says 'milli'? I mean, isn't that like the first five letters in 'million'? Stupid *** metric system.[:$] All right, Mr. Baiter (like my double entendre?[:$]), in the metric world, milli=1000ths and micro=1,000,000ths. Quote Link to comment Share on other sites More sharing options...
Parrot Posted October 23, 2005 Share Posted October 23, 2005 As far as spurious double-taps go, the only records I can think of that I own that have clicking heels are Flamenco guitar ones. And the taps of the Spanish dancers are mighty fast and of course there's lots of echo. Hope this helps. Quote Link to comment Share on other sites More sharing options...
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