http://www.behringer.com/DSP1124P/index.cfm?lang=ENG
It uses some kind of search algorithm that controls a parametric equalizer
It uses some kind of search algorithm that controls a parametric equalizer
The oldest versions of feedback-killers (or feedback eliminators) used frequency shifters that shifted the whole audio spectrum up or down. The frequency-shift was between some tenths of a Hz up to ca 20 Hz.
The working principle was similar to the so called phase method for SSB.
Regards
Charles
The working principle was similar to the so called phase method for SSB.
Regards
Charles
pinkmouse said:
I had the idea about that high Q. Couple years ago me and my friend were doing some experiment with mic and 3-way speaker. Each speaker had its "own" wistle frequency. I will have to do same test now to determine if this is true. Back then we were just beginers and did not pay atention on details. If the test shows that there is one frequency for each driver, in my case for 2-way PA speaker, then i would hace to build 2 Q filters that will choke those 2 frequencies.
Maybe i'm to paranoic about these stuff and i'm asking too much for total amplifier protection
Hi all
Anyone know why frequency-shifters might not be used anymore - or are they?
These work on all microphones and speakers, and won't cause a "blind spot" in the response at the filter frequency.
Only reported downside to these was a possible "beat" frequency if the gain is still too high - this meant that you could hear the shift I think as a beat.
cheers
John
Anyone know why frequency-shifters might not be used anymore - or are they?
These work on all microphones and speakers, and won't cause a "blind spot" in the response at the filter frequency.
Only reported downside to these was a possible "beat" frequency if the gain is still too high - this meant that you could hear the shift I think as a beat.
cheers
John
Hypercardiod microphones-well, you know, that is ok but i allways think for the worst case. A good singer, or performer, will be aware of the speaker-mic issue but the world is full of so called profesionals, speakers, who have no knowlage of it I think that they are made of steel so speakers magnet draws them to it
Couple of times i worked "live" contents in singing, for the radio station. Our two radio speakers, self called profesionals, were stickin to main speakers and the wistle was heard much often then their bright sentences No matter how many times i have told them not to go close to speaker they did it anyway. 
There was 5 meter at least for them to be on the stage but nooooo, if there was a posibility they would get in to the speaker all with the mic 
I think that they are made of steel so speakers magnet draws them to it Couple of times i worked "live" contents in singing, for the radio station. Our two radio speakers, self called profesionals, were stickin to main speakers and the wistle was heard much often then their bright sentences
No matter how many times i have told them not to go close to speaker they did it anyway. There was 5 meter at least for them to be on the stage but nooooo, if there was a posibility they would get in to the speaker all with the mic It's standard practice when sound-checking a PA system to 'ring round'.
The gain is increased until the system starts to ring (can be checked by clicking fingers in front of the mic - much less traumatic to system and operator than provoking howlround). EQ is applied to eliminate the ring, the gain is increased a little more, the new ringing frequency is EQd out, and so on, until ringing/howlround is pretty much random.
This simple process will allow a substantial increase in gain with minimal detriment to the sound if the initial setup is sensible and doesn't encourage major resonances.
The gain is increased until the system starts to ring (can be checked by clicking fingers in front of the mic - much less traumatic to system and operator than provoking howlround). EQ is applied to eliminate the ring, the gain is increased a little more, the new ringing frequency is EQd out, and so on, until ringing/howlround is pretty much random.
This simple process will allow a substantial increase in gain with minimal detriment to the sound if the initial setup is sensible and doesn't encourage major resonances.
Step One: Hypercardioid Microphones (Reject the best outright)
Step Two: Microphone vs. speaker placement (Angles!)
Step Three: Type of Speaker (some are worse at producing feedback)
Step Four: Parametric EQ (last step to give you the last few dB of gain).
I've used the Behringer Sharc and it allows you to place the mic
into the cone of the speaker, but at the cost of sound quality (it
creates many large narrow band cuts to eliminate the 'bad'
frequencies). Stick with hypercardioids first, they eliminate 70%
of feedback. Keeping speakers pointed 180 degrees from the
least sensitive angle of the mic is the next step. Acoustic suspension
speakers feedback worse than bass-reflex designs. A good parametric
EQ can take care of the rest of the bad frequencies generated by the
room.
Step Two: Microphone vs. speaker placement (Angles!)
Step Three: Type of Speaker (some are worse at producing feedback)
Step Four: Parametric EQ (last step to give you the last few dB of gain).
I've used the Behringer Sharc and it allows you to place the mic
into the cone of the speaker, but at the cost of sound quality (it
creates many large narrow band cuts to eliminate the 'bad'
frequencies). Stick with hypercardioids first, they eliminate 70%
of feedback. Keeping speakers pointed 180 degrees from the
least sensitive angle of the mic is the next step. Acoustic suspension
speakers feedback worse than bass-reflex designs. A good parametric
EQ can take care of the rest of the bad frequencies generated by the
room.
Loud stage monitors should be avoided as much as possible. Even when there is no positive feedback, a lot of the sound radiated by the monitors is still being picked up by all the microphones after being coloured and reverberated by stage acoustics. Furthermore, each stage monitor will be picked up in a different way and with a different delay by each microphone producing a big mess.
When there are a lot of loud monitors in the stage, the result after mixing is the usual live audio "can sound" trash with 20dB signal to noise ratio and an ugly "tail", which has to be disguised with tons of added reverb.
I strongly recommend in-ear monitoring, plain headphones and minimum stage monitoring. A quiet stage is one of the keys for high quality live audio.
BTW: Yes, I know, the hard part is to persuade singers and musicians... I used to do the PA for an old and stubborn singer which didn't seem to know how to sing with anything but 110dB of "monitoring". Musicians used to complain and to wear ear plugs... (No joke!)
When there are a lot of loud monitors in the stage, the result after mixing is the usual live audio "can sound" trash with 20dB signal to noise ratio and an ugly "tail", which has to be disguised with tons of added reverb.
I strongly recommend in-ear monitoring, plain headphones and minimum stage monitoring. A quiet stage is one of the keys for high quality live audio.
BTW: Yes, I know, the hard part is to persuade singers and musicians... I used to do the PA for an old and stubborn singer which didn't seem to know how to sing with anything but 110dB of "monitoring". Musicians used to complain and to wear ear plugs... (No joke!)
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