May 5, 2007 at 4:30pm
Did anyone try to program a feedback killer with max? Actually, I’m doing a piece with real-time processing with 5 simple delays (without feedback) at different length (between 529 and 6001 ms) and the patch is very susceptible to feedback loops problems.
The processing is on a piano captured with a At-822 quite near, the 2 speakers are not aiming the piano and it is in a Chapel.
Basically, my feedback killer patch tries to control feedback loops in analysing the incoming sound (which voluntarily contains feedback loop) with fiddle and sending the frequencies of the sines to notch filters.
Unfortunately, this patch is not efficient enough, it cuts feedbacks a bit but not completely… (when I run my other patch in parallel…). Then, I put a little variation on the delays’ length but still, it feeds!
Thanks for any help!
I also join the part of my patch with the 5 delays.
May 5, 2007 at 6:06pm
I’ve seen setups with combination speaker and microphone arrays which
On 5/5/07, Julien-Robert
May 5, 2007 at 6:34pm
The website contains some information about a scientist method to acheive a feedback cancelation. Unfortunately, the terms used are too advanced for my knowledge and this is based on concepts that I don’t know… so, it does not really help me.
For the idea of jiggle the filters depending on the feedback’s movements, if they succeeded to do it (for speech), I really don’t know how to do it in a case where the source is constantly playing (piano) and where there is always others sounds (real-time processing)… Because in this case, we can not analyse the sound using fiddle which will be useless for a complex sound (it will constantly move in all the directions)…
May 7, 2007 at 3:45pm
This would only help for the amplified, undelayed signal
> Unfortunately, this patch is not efficient enough, it cuts feedbacks
Why do you think this would help? to vary a delay would just add some
Filtering feedback pitches would only work for direct undelayed
Your delayed material has fundamentals of 0.17 Hz to 2 Hz….
You could search for techniques of echo suppression like it is used for
May 23, 2007 at 5:38pm
One other way to do it would be with a dynamic convolution filter using
This all said, you might find that a multiband compressor-limiter with
On May 7, 2007, at 11:45 AM, Stefan Tiedje wrote:
> Julien-Robert schrieb:
May 24, 2007 at 6:31pm
You might want to try pitch shifting the output of the speakers by a fractional amount. Or as previously suggested with a notch filter try varying the amount of pitch shift. freqshift~ should do the trick, remember only to shift a very small amount so noone notices.
May 25, 2007 at 12:09am
i might be crazy, but i think you guys are getting way too techno-geek about this problem. in a live sound setup, feedback happens because of poor setup. period. just because the speakers are pointing away from the microphone doesn’t mean everything is ok. you also have to think about reflections (especially in a church). if you’re pointing the speaker directly (i.e. perpendicular to) the back wall, then you’re going to get a big reflection back at the stage.
using crazy dynamic notch filters is generally the easy way out, and it usually doesn’t work too well. not to mention that any type of processing you do to artifically get rid of feedback is going to adversely affect the quality of sound. there is no getting around this. notch filters, jiggly notch filters, dynamic convolution filters, pitch shifting (?!) will all substantially decrease the quality of sound coming out of your speakers. if the quality of sound is not an issue, then go for it.
here are some things to consider:
the greater your signal to noise ratio is for the piano (or anything else being miked), the greater gain before feedback you will have. this means you can get a louder signal out of your speakers before it starts to feedback. so, try moving the mic closer to the piano. try putting the mic way inside of the piano and closing the lid most of the way. try facing the piano so that the lid opens away from the speakers. in other words, first try getting rid of the problem without using electronics.
here’s something else to consider:
assuming that the microphone and the speaker (and any major structural elements of the room) are not moving, your mic-speaker system will ALWAYS feed back at the same frequencies. so, armed with that knowledge, during your sound check, turn the gain way up until it just starts to feedback. find the frequency of the feedback and notch it out. then, turn the gain up some more and find the next feedback frequency and notch it out. continue until your gain is high enough. as long as you don’t move the mic or speaker, you should have gotten rid of most of the major resonance frequencies of the system. of course, if any of those frequencies occur in the music, you’re not going to hear them either.
feedback eliminators work marginally well for speech, since they are looking for pure sine waves with a steady frequency. however, music is chock full of sine waves with steady frequencies, and that tends to confuse the hell out of feedback eliminators.
i’d recommend googling “gain structure” or “audio gain structure”. there’s bound to be a ton of articles on this very important topic, which will help you immensely in getting rid of feedback.
May 25, 2007 at 5:11pm
Parent is right. The other contributor to feedback is routing of the
- If you want the dry sound of the instrument, do not, unless there is
- Definitely use the piano at 1/4 stick if you haven’t already.
- You might try a PZM microphone on the piano taped to the lid, with
- You might place gobos near the piano to block certain reflections.
- Use metering within Max on your input to bring your input signal to a
- I prefer faders using linear gain coefficients using *~ and
- Avoid reliance on wishful thinking when designing delay loop
> i might be crazy, but i think you guys are getting way too techno-geek
This all said, there are definitely circumstances where crazy
Jul 18, 2007 at 8:00pm
i have to attach 4 accelerometers to dancers’ limbs for a piece. i have
Jul 18, 2007 at 8:19pm
Quote: email@example.com wrote on Sat, 05 May 2007 18:30
One other solution is to use a Schertler DYN-P or DYN-GP pickup instead of normal microphones :) The Schertler is expensive but is supposed to have a better sound than piezos, for examples. Maybe the C-ducer condenser microphone pickup is good too (probably less natural). When I have time I will rent a Schertler and a C-ducer to see how it is in practice. Lots of piezo contact microphones I tried were quite good for high register but had crappy bass sounds (much like a guitar or a CP-80, which is not bad but at least unnatural).
Also, some people use a combination of any contact microphone (for the “power”) with two electrostatic microphones (for the “space” and the “spectra”) to reduce feedback …
Aug 15, 2009 at 12:52pm
what do I use to open the attachment maybe I could be sum help
Aug 15, 2009 at 8:02pm
I did these patches on max 4.6. It’s all packaged in a standard zip file.
Aug 16, 2009 at 2:53am
stefan is right, the comparison with analog feedback killers
in a tapping delay, “feedback killer” usually means an
that is not exactly the same as the speaker-and-mic stuff,
p.s. i wish a had a perfect autogain .. i dont have.
i use the following 2 methods:
Aug 16, 2009 at 2:59am
you can almost hear someone walking into the thread and
Aug 16, 2009 at 3:10am
what do I use to open the attachment maybe I could be sum help
his patches are in text format.
in OS9 you have to type them to “TEXT/max2″, and in windows
when something doesnt work as bin, try as text.
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