You are here

Live 3 second delay / echo

For performing musicians and engineers: stagecraft, engineering and gear.

Re: Live 3 second delay / echo

Postby Sam Spoons » Thu Aug 29, 2019 6:29 pm

Good effort Stratman, :clap: I was wondering myself how much delay is required to make the system impervious to feedback, or indeed if that's possible. I did try short delays (a few ms) a few years ago but they did not help much if at all. I guess if the delay is less than the room's reverb time feedback/howlround will be a risk.
User avatar
Sam Spoons
Jedi Poster
Posts: 9991
Joined: Thu Jan 23, 2003 1:00 am
Location: Manchester UK
Finally taking this recording lark seriously (and recording my Gypsy Jazz CD)........

Re: Live 3 second delay / echo

Postby Folderol » Thu Aug 29, 2019 6:33 pm

A suggestion (from the depth of my ignorance)
Mount mic and speakers on the same surface pointing to a highly sound absorbent one the other side of the room/corridor or whatever. Apply a fairly narrow band-pass filter to the microphone - just wide enough to respond reasonably to speech.
User avatar
Folderol
Jedi Poster
Posts: 8749
Joined: Sat Nov 15, 2008 1:00 am
Location: The Mudway Towns, UK
Yes. I am that Linux nut.
Onwards and... err... sideways!

Re: Live 3 second delay / echo

Postby Stratman57 » Thu Aug 29, 2019 8:21 pm

Thanks Sam.

I was working on the theory that the surface the PZM is mounted on effectively disappears, so if the mic was mounted on a large wall with the speakers maybe flush with the wall surface the feedback would be minimised, assuming the mic was isolated from wall vibrations. I had the repeat level less than the mic level, so the next 3s repeat wouldn't start to feedback.

I only had a low cut filter on the mic, but having a high cut would also help I think. The PZM I was using was as standard, not modified to use phantom power or for balanced operation so I think with a higher spec boundary mic more gain before feedback could be achieved. The hemispherical pick up pattern could also be modified to minimise pickup from the speakers.

Interesting problem, it's the sort of thing the drama director I work with would come up with for a production, and expect me to sort it out. And fun to do without the pressure. :-)

Regards, Simon.
Stratman57
Regular
Posts: 151
Joined: Wed Apr 20, 2005 12:00 am

Re: Live 3 second delay / echo

Postby Hugh Robjohns » Fri Aug 30, 2019 10:37 am

Stratman57 wrote:...if the mic was mounted on a large wall with the speakers maybe flush with the wall surface the feedback would be minimised, assuming the mic was isolated from wall vibrations.

A PZM on the wall with soffit-mounted speakers would be a sensible solution, but it would need an effective high-pass filter to prevent pickup of the LF from the speakers which would radiate hemispherically along the wall.

The mid and HF from the speakers normally has a much narrower radiation patter so the PZM in the middle of the wall would, effectively, be in a sound shadow and not pick up much direct sound at all. Strong reflections from any rear or side walls would be the biggest problem, but drapes or similar would deal with the worst of that...

H
User avatar
Hugh Robjohns
Moderator
Posts: 24298
Joined: Fri Jul 25, 2003 12:00 am
Location: Worcestershire, UK
Technical Editor, Sound On Sound

Previous

Who is online

Users browsing this forum: No registered users