Speakers would be the first place to start (as already mentioned taking
them off the ground will make a difference)
Also, put them at the end of the room instead of the middle - then
people can choose to sit near or not - that way the people who want to
chat over their meal can get a seat away from the sound, and not fight
with it, and those who want to listen can get close, and will be
quieter (in an ideal world - it won't work perfectly,but it will help)
Position yourself out of direct throw range of the speakers - ie behind
them. From what you say, the music isn't over bassy, which is the
frequency most prevalent from behind a PA due to the spherical
dispersion. Other frequencies have a more directional dispersion.
If you can't do any of that, work out which mic it is that is causing
the problem (I would suspect the Shure), by deliberately inducing
feedback on one mic only (do it during a break, when the place is full
- you don't need to push to full howl round, just to the point it
starts to build, and note which mic causes most)
If it is the Shure, you could get a directional muffler for it like the
ones tv or film engineers use - they usually set you back around =A3100
- =A3250 for a good one.
Or tune the room (either spectral analysis if you're a sound gorilla
like me, or by ear if you are a good musician). Find the frequencies
that cause the feedback (it will usually be one main frequency, with a
1st order harmonic either side) which reacts to the room acoustics
badly - I've seen rooms with more, but they tend to be stone barns with
lots of fixed furnishing, and odd shapes. Then set up a compressor with
side chain eq between your mixer and amp to keep that frequency under
control.
Remember as well that tube amps actually add a certain amount of
distortion (usually lots of 2nd order harmonic which sounds nice - the
cause of the "warm" sound tube amp users like), but it is still a form
of harmonic distortion, and will induce feedback more readily than a
more linear amplification without the distortion.
Or you could get a feedback destroyer - which is essentially the above
idea, but with several compressors linked each to a parametric eq
(Behringer do one that works fairly well. Expect to take a hit on sound
quality, but only when necessary). They work well, and have the benefit
of an auto listen and tune mode (which much to my suprise also works
well)
If you're in the UK, I have one of the above Behringers that I'm
selling (don't do band work anymore, and it's surplus to requirements -
well looked after though, and I have the manuals, and probably the
original box somewhere). If you're interested (I'll probably want
about =A340ish for it), email me at
. We can do
it through ebay or something (I'm going to list it anyway, but would be
happy not to have to...Shameless selling attempt over, and my apologies
to all for the fact that this ng is an info node, and not a
marketplace...:-) )
Also, if you want to get in touch at the email above, I am happy to
give you a more in depth analysis of the room and setup (we can do it
on here, but I'm not very regular in my newsgroup habits, and it will
probably take a good few answered questions to nail it fully. I can
save the mails, and post them as a faq if there is interest).
Feedback is a swine though. I've been in that position often enough
that I'll happily help anyone as much as I can (definetly comes under
the heading of my boy scout good deed for the day...:-) - the fewer
tarnished Karma's from feedback the better - I used to end up
apologising to everybody for days after a bad run in with howlround,
because it made me really snappy and grumpy until I'd sorted it -
usually got lots of noise from the bands too who would spend days
rubbing in the fact that it was them who had the right to grump, as it
was my job to solve those problems, and having me grump about them
wasn't fair...:-)
Anyway, hope this helps some.
Leo.