« Reply #1 on: July 21, 2007, 11:46:33 AM »
@nedster - since this is not an SMS forum, there are no restrictions to writing words fully; text speak is usually found in forums.
As for your feedback eliminator routing, your should use it in between the mixer outputs and amplifier inputs. To quote from the
Media College:
"Audio feedback
(also known as the Larsen effect) is a special kind of feedback which occurs when a feedback loop exists between an audio input (for example, a microphone or guitar pickup) and an audio output (for example, a loudspeaker). In this example, a signal received by the microphone is amplified and passed out of the loudspeaker. The sound from the loudspeaker can then be received by the microphone again, amplified further, and then passed out through the loudspeaker again. This is a good example of positive feedback. The frequency of the resulting sound is determined by resonant frequencies in the microphone, amplifier, and loudspeaker, the acoustics of the room, the directional pick-up and emission patterns of the microphone and loudspeaker, and the distance between them.
More specifically, the conditions for feedback follow the Barkhausen criterion, namely that an oscillation occurs in a feedback loop whose delay is an integer multiple of 360 degrees and the gain is equal to or greater than 1 (both at the given feedback frequency). If the gain is greater than 1, then the system can start to oscillate out of noise, that is to say: sound without anyone actually playing.
Most audio feedback results in a high-pitched squealing noise familiar to those who have listened to bands at house parties, and other locations where the sound setup is less than ideal — this usually occurs when live microphones are placed in the general direction of the output speakers. Professional setups circumvent feedback by placing the main speakers a far distance from the band or artist, and then having several smaller speakers known as monitors pointing back at each band member, but in the opposite direction of the microphones.
Audio feedback is usually undesirable. However, electric guitar players such as Pete Townshend and Jimi Hendrix have used it as an audio effect, and was used extensively after 1965 by the The Monks, first played onstage by The Who and first commercially recorded by The Beatles on the single "I Feel Fine" released November 26, 1964 in the UK. Used in this fashion, the artist has some control over the feedback's frequency and amplitude as the guitar strings (or other stringed instrument) form a filter within the feedback path and the artist can easily and rapidly "tune" this filter, producing wide ranging effects. Artists can even manipulate feedback by shaking their instruments (in the style of Pete Townshend) in front of the amplifier, creating a throbbing noise. More recently, Audioslave guitarist Tom Morello (formerly of Rage Against the Machine) has employed feedback in conjunction with a "killswitch" on his guitar and heavy use of the whammy bar to create inventive hip hop-influenced solos.
Also note that desirable feedback can be created by an effects unit by using a simple delay of about 50 ms fed back into the mixing console. This can be controlled by using the fader to determine a volume level.
To avoid feedback, automatic anti-feedback filters can be used. (In the marketplace these go by the name "feedback destroyer" or "feedback eliminator".) These electronic devices are a multi-band parametric equalizer combined with a spectrum analyzer which applies a notch filter to frequencies with a very high peak compared to the rest of the audio spectrum. This can also be accomplished by an audio engineer using either a parametric equalizer (normally found on a mixer's input channels) or a graphic equalizer (commonly connected between the mixer's outputs and the amplifier inputs to correct acoustical problems in a room or to address feedback issues)."From the same site about Grouping:
"Over view of Sub groups
IO5-D/c
Inline Module 5MT Series D
Stereo Master, Pan Pot's and Sub Groups
The main stereo master MIX is assinged to the tape chain. The input of the MIX PAN is driven by the tape chain fader output. Its output drives the stereo mix bus.
In addition, there is a second pan pot, the RT-PAN, that is driven by the output of the record chain fader.
Both Pan Pots are rotary controls with center detend. The center attenuation is 3 dB, which maintains are pure direction control that does not change the level.
While the mix pan is always in the signal path of the tape chain, the RT pan can be switched into the signal path from the record chain fader to the input of the routing matrix by the PAN switch, next to the pot. Since in most cases, the routing is used for mono recordings, the pan is only needed for a stereo recording. When active, it controls the level relation between the odd and the even routing busses.
It is possible to rout the output of the record chain fader to the mix bus. This very important feature makes it possible to use the channel for two independent input signals while mixing. The MIX switch routs the record fader to the main stereo bus. In differenc to the routing matrix, the RT-Pan is always active if the record fader feeds the mix bus.
TO RTG
The TO RTG (to Routing Matrix) switch next to the Mix Pan rerouts the output of the mix pan from the mix bus to the input of the routing matrix. This switch overrides the default signal flow from the output of the record chain fader to the routing matrix.
This function makes it possible to arrange audio sub groups on the fly without the need to consider the level relations and the pan settings. By pressing TO RTG, exactly the level that was sent to the mix bus now drives the input of the routing matrix. If a pair of routing busses is selected, that are not otherwise needed, these busses become a subgroup that mirrors level and pan settings exactly. This principle offers the choice to arrange any number of audio subgroups up to a maximum of 12 stereo at any time.
Sub Group Master Chains
Of course, an audio subgroups needs a master channel. The IO5-D/c inline modules offer the choice to use either the tape chain or the record chain of any channel as audio sub group master. While one of the chains is used as master, the other chain can still be used for another signal. The INP switch selects the output of the channel's routing bus amp as tape chain input signal. If SUB is pressed, the record chain becomes a sub group master. This method requires no patching but the channels of the selected routing busses must be used as master. In addition, it is possible to get the bus output signal from the patchbay. In this way, of course, any channel, including stereo channels or stereo returns of the master section can be used as subgroup master.
The audio subgroup system of the 5MT Series D mixing consoles is not limited to one level only. Since every subgroup master can be routed to another routing bus, it is possible to build up very complex grouping areas, from a simple one level only group to a system that can use up to 12 levels."Now this is specific to a particular piece of gear, but the principles are the same. Just apply them to the Spirit although I think yours is limited to 4-bus?
« Last Edit: July 21, 2007, 12:50:11 PM by KitC »
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