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#1
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enhancing early reflections?
i have some tracks of a flute part that were recorded in a dry room and
lack any semblance of realistic early reflections. if i want to add some more realism to the sound by enhancing early reflections, should i tweak up one of my delay patches, or one of my small room reverbs? any guidelines or techniques you might suggest? thanks. |
#2
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..
When it comes to creating the impression of a believable reverb environment, what are the factors that matter most? There are three areas of reverb perception. Firstly, there's the whole issue of intelligibility and appealing reverb and what influences them; what makes something hard to understand and appreciate as opposed to easy to understand and appreciated. You have the sense of distance, which is influenced by nearly any time range. Direct sound energy coming in nearly any time period will cause a feeling that you are at some distance from the originating sound. This distance effect will be made up of original direct sound, and its relationship to duplicate delays. If a delay arrives within 15ms of the original sound it will create imaging problems. For example, if you have a sound panned in the center and a delay of 1-15ms on the right, what you will hear is the image in the center shifting to the left. This is caused by the innate characteristics of human hearing in its relationship to localization. The ear perceives localization because a sound wave will arrive at one ear slightly later than the other ear. This is an innate survival mechanism for human behavior. It is otherwise known as the Haas effect. If a delay of 1-15ms is brought back and panned to the same position as the original you will create phasing effects. If a delay signal arrives later than 15ms but before 100ms (approx) from the original sound it will create dimension, for what you have done is alerted your psycho-aural response, which tells you that you are listening to the sound in a reflective environment. Whereas, if you just heard the original sound only the psycho-aural response would create the effect that you are standing in a field. If you had a signal panned centered and delays of 40ms (left) and 60ms (right) it would sound like you were sitting at a distance with the left reflective surface slightly closer to you than the right. If these delayed signals are dull sounding it will imply that the reflective surfaces are absorbing the high frequency content and placing you in an environment of wooden walls rather than glass. If a reflection is heard after 100mS, you will perceive it as a separate form of sound energy, perhaps as a discrete delay depending on the nature of the source. It will also be easy to localize it in the stereo image, so if you have a reflection coming in at 200ms and it's panned to the left side, you'll hear it coming from the left. This is not true if it arrives between 15-100ms. If the delay occurs between 15-100ms it will not be perceived as a discrete delay, it will only create depth. If the delay comes from the left it will be difficult to localize the delay in the panning image, for it will not be perceived as a separate sound event although if you have very short percussive sounds such as rim shots, clicks or handclaps, you will perceive the reflection separately because of its transient nature and short duration time. If this occurs, you will need to shorten the delay times to maintain clarity. Generally, any reflections arriving between 15-100ms will not affect clarity. Adding reverb with delays will create a natural sounding acoustic environment (more on that later). In figure, you will see the setting of a concert hall with three different seating positions situated at fixed distances from the original sound source. In position "A" you will mostly hear the original sound source (80%), little early reflections (5%) and reverb (15%). In position "B" you will hear the original sound (60%) early reflections (20%) and reverb (20%). In position "C" you will hear original sound (40%), early reflections (30%) and reverb (30%). In position "A" the original sound source (80%) will be full in frequency response and arrive to the listening position in 5ms. The early reflections will barely be audible because the listener is sitting very close to the sound source and the walls of the hall are almost all-equal distance from the listening position. The reverb will be delayed when it arrives back to the listening position. The actual time of this delay will be measured by the distance from the original sound source to the walls and then back to the ear (100ms pre delay). The reverb will not be bright. It will be warm sounding for the high frequency content of the reflections have been absorbed by the walls. Because the "A" listening position is not close to a wall and at a distance to the original sound source it will barely hear any early reflections. The delay of the onset of the reverb will indicate how far the walls are from the listener. The length of the reverb will indicate how live the environment is. The overall sound will be intimate, clear and pleasing to the ear, especially if it is a great singer performing a ballad. To create this in mixing you will need to add in a reverb that rolls off more high frequency content over the decay of the reverb. This means, as a reverb gets longer it also gets duller. A pre delay of 100-150ms is needed to create the effect that the singer is close but in a live acoustical environment. Watch out for sibilance in the reverb. Sibilance is just noise and will effect clarity in the mix. The way to get rid of this is to heavily de-ess the reverb send not the reverb return. Try to remove all sibilant information above 3kHz. Roll off the reverb return in the high frequency and low frequency area and maybe slightly boost around 2-2.5K to add a little presence for clarity in the reverb. If using a long reverb time that tends to thin out over time add in a stereo delay based on the rhythmic value of the song. If the song has a tempo of 120bpm, a quarter note will equal 500ms. It is important that when you add in a delay to your reverb that it be a fundamental of the rhythm for the landing of the beginning of the delay will also land on an instrument playing on the same beat. This will allow you to increase the delay to your reverb without noticing it as a discrete delay. Obviously, if the delay was 400 or 600ms you would hear the delay sounding discrete for it is landing in awkward places in the rhythm of the song. If you add in a de-essed, slightly regenerated quarter note delay to your reverb sound, you will add musical body to the sound of the reverb. Instead of adding a mono 500ms delay, add a stereo delay of 490ms (left) and 510ms (right). Make sure the 2 delays are at least 15ms apart to prevent the Haas effect. This stereo delay will enhance the effect of the reverb and still sound in time with the song. Also insert a low pass filter on the delay, so when it regenerates it sounds less bright on each additional delay and more believable to the listener for this is what truly happens in a natural acoustic environment. In total the original sound will be 80%, early reflections 5% and reverb 15%. In listening position "B", the original sound source (60%) will have less high end and low end due to the increased distance between the sound source and the listener and arrive 35ms at the listening position. The early reflections (20%) will be arriving mainly from the left and right walls. The longer the early reflections, the greater the distance between the sound source and the listening position. Especially if the early reflections get less bright with the longer delay time. The early reflections inform the psycho-aural response by informing the listener that they are in an acoustic environment with at least two reflective surfaces. A delay of 60 and 80ms will indicate that the listener is sitting further away from the sound source than with a delay of 20 and 40ms. It is important that the delays reside between 20 and 100ms and be at least 15ms in difference to prevent the Haas effect and that the longer delay be slightly lower in level. The reverb will arrive to the "B" listening position sooner than the "A" listening position. This is because in the "B" position the time it takes for the original sound to arrive to the listening position is 35ms and the onset of reverb begins at 100ms. The difference is 65ms, which is what your pre-delay should be set to. The reverb frequency response will sound better due to the slight deterioration of the original sound caused by the time it takes for sound to arrive to the "B" listening position from the sound source. So to create this dimensional effect, make sure that the original sound source does not have an extremely wide frequency response. The depth will be created by at least two or more delays arriving between 20-100ms. The sooner the delay the closer you will be to the sound source. Make sure the delay has some high frequency roll off so the ear will not confuse the delayed signal with the original signal as being the focus. The reverb will have a smaller pre-delay and sound slightly brighter than the reverb in the "A" listening position. Be careful that the reverb time does not corrupt the harmonic content of the original sound source. Most instruments that require this effect will be playing in a harmonic content rather than a melodic content, like a lead vocal or a solo. A good rule of thumb is to make sure that the reverb time of an instrument playing harmonically is not too long where the mix becomes harmonically confusing. In listening position "C" the original sound (40%) will arrive to the listening position (65ms) at a lower level than positions "A" and "B" and its frequency response will be even less than listening position "A" and "B". That is not to say you should go out of your way to deteriorate the sonic quality of the sound. It is more like "Do not put too much efforts to make it sound full". It should contain low end and presence in keeping with the character of the instrument. The early reflections will be longer than the reflections of listening position "B" (60-80ms). They will still sound less bright than the original sound but will be more prominent in level in the overall sound (30%). It might also be good to create more additional delays (120 and 160ms) beyond 100ms, but these delays should only add depth and not necessarily be heard as discrete delays. The reverb will also contribute more to the overall sound and its pre-delay will be even shorter. In the "C" listening position, the original sound arrives to the listening position 65ms later. Because the acoustics of the environment are fixed, the reverb should not change dramatically. With the onset of reverb occurring 100ms after the original sound source, the difference between the reverb arriving to the listening position and the original sound is only 35ms, which is now your pre-delay setting. Overall as we move further back from the sound source the frequency response of the original sound source gets smaller and early reflections and reverb add to the overall sound. As you move further away from the sound source the reflections and the reverb increase in content to the overall sound. The distance in time between the original sound source and the early reflections and reverb will decrease. The overall sound source should always be louder than the reflections and the reverb for this is a fundamental rule in creating depth in your mix. If you chose reverb as a pre-send, the reverb that is generated will still contribute qualities of the original sound source. The frequency response of the reverb dictates the acoustic properties of the reflected materials. If it is hard like concrete, the reverb will contain a lot of mid-range and high end. If the reflective material is wood it will mainly absorb high and mid-range frequencies. Many musicians prefer older concert halls because of their warm acoustical properties that tend to just reflect the musical content of the sound source. Remember that reverb works best when it is treated in a musical context. It can elongate the duration of beautiful melodies; it can create more resonance to drums and add perspective to various harmonic instruments in the mix. If you have a sound source like singing and want the vocal to sound like a ballad performance, you'll find that you can create a recording where the singer sounds close or far away, at the same time. This is a very easy thing to do if you have no 1st reflections, early reflections and late reflections (highly diffused). You get this by close-miking the original sound and then adding delays, pre-delay to the late energy (reverb), and reverb with hall or a plate setting. If, for example, you use a reverb setting of say, 3 seconds with 100ms pre-delay on the onset of later highly diffused reflections (reverb), you'll find that the vocalist sounds very intimate, a sort of "in-your-face" sound but in a hall environment. If you like this reverb setup but wish to create more distance between the singer and the listener and don't want to change the reverb decay time, you will have to introduce a series of 1st reflections so you can slightly recess the singer. Just using a standard 3sec reverb setting with no pre-delay and no delays (reflections) will just give you a basic 2 dimensional hall environment without any sense of listener-to-vocalist distance, no matter how much reverb or length of reverb time you assign to the original signal. By adding the earlier energy and over a wider range we can create what type of a 3 dimensional sound we desire in our mix. If you add in delays from 50ms-250msec you might create problems with the sound remaining intelligible and clear. However, you might want to utilize this for creating a slap back type of effect for lead vocalist. If used effectively, it will create distance between the original sound source and the listener. It is also important to decrease the high frequency response to keep the original vocal more present and clear and also allowing you to use more of the delay signal. |
#3
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my goodness - thanks so much for the amazingly detailed response. i
hope others have the chance to read this. |
#4
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JN,
thanks so much for the amazingly detailed response. I can't match that post! But I will answer your initial question: or one of my small room reverbs? Yeah, that's what I do with great success. But don't overdo it. A little electronic ambience goes a long way, and if you add too much it sounds artificial. I often switch the bus Return on and off while the track plays, so I can better hear how much effect I'm adding. --Ethan |
#5
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You could try playback through some decent speakers, miking them from the
room, and then add the result back into the original recording. -- Roger W. Norman SirMusic Studio http://blogs.salon.com/0004478/ wrote in message ups.com... i have some tracks of a flute part that were recorded in a dry room and lack any semblance of realistic early reflections. if i want to add some more realism to the sound by enhancing early reflections, should i tweak up one of my delay patches, or one of my small room reverbs? any guidelines or techniques you might suggest? thanks. |
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