First of all you've jumped in the deep end doing live theatre, not an easy task at all. You don't say what type or size of PA system you are using or the brand of mics so I can only give general comments.
The first thing you need to do is get the gain structure of the mics right. Have a look at the receivers and check if you have an audio level meter as well as an RF meter. With the actor speaking or singing into the mic check the level and make sure it's not peaking. Check the transmitter to see if it has adjustable output. The wireless mics I've used are adjustable in 5dB increments down to minus 30dB. If you can get this right it should solve your distortion problems.
Next set the channel fader at 0dB and slowly bring up the gain until it starts to ring. Now you need to adjust your eq to pull out the offending freqencies. Your best solution here is a 32 band graphic for each mic, but a good compromise is to send male voices to one subgroup and female voices to another with an EQ on each subgroup. If you can get it loud enough to just light the channel peak led with faders at 0dB you have reached the maximum volume for your system.
A SMALL amount of compression may help but too much will cause you more feedback problems.
If your sound is "hollow" reverb will make it worse.
I'm by no means an expert at this but I hope this helps a little.

PissedOff Fed:
You have walked in to a hornets' nest, eh? First off, the "hollow sound" is probably the placement of the mic on the actor(s), in relationship to any stage monitors and the FOH. You will need to work on that first...because:"Garbage in, garbage out" rules here. Like the first poster correctly ascertained, you haven't told us what type of wireless mics you have, etc. headset-type mics that put the element by the performers' mouth are best, but aesthetics and budget may make these impractical. Are these mics omni or uni-directional? You'd be surprised how many lavs pick up everything around them. If you are using stage monitors, keep them down, with minimal live talent in them. Try to use them primarily for the music tracks to cue the singers.
As for the dynamics of the vocalists, it sounds like you are dealing with talented amateurs here, who may not have the best breath control. A decent "voice processor" like a dbx 286a patched between the wireless receivers output and the mixers channel line input can do wonders here.
Then again, maybe a voice coach is in order here to delicately "steer" the vocalist out of trouble.
By the way, this question should have been posted in the "live sound" forum further down the list. There are lots of theater/church pro's who can provide you with more input....

Yes, it certainly does. Thanks!

Theatre is a challenge, but I love it. Sound design is my main interest, along with general audio production (and photography, tech theatre, music...). Thanks for the advice.

Do you think that the EQ on a mackie board is sufficient? I know it's nothing like a real 32 band equalizer, but we're a high school theatre company, budget is completely funded by ticket sales.

Our PA is a pretty standard cluster, and I think that we're using two crown amps (not sure of the power, though), one for the subwoofer/main speaker and one for the horns/highs. The mic's are sennheisers, e100's. Four of them. Then we're testing out a shure lav that we have, to see if it works (we've had problems with its reception of late) and to see if we need to rent a fifth mic. Another strain on our budget... That, and we're getting condoms (YAAAYY!!!) I love that condoms are standard for lav's. It makes me feel very immature to giggle at that, but oh well.

They're cheap, though.

The e100 RECIEVERS have a gain nob on the back, and squelch is adjustable on the display. I'll have to fiddle with it tomorrow afternoon. The AF level has been peaking a bit, but I hadn't time to do anything about it on Friday when we tested the mic's with actors for the first time. I don't believe that they have any sort of gain on the actual transmitters. Just squelch.

On a mackie board, how would I send the EQ to a subgroup? Through an aux send? I'm not really that familiar with the board as a whole. I can work my way around a simple alesis or behringer board nicely, I know what just about everything does. I'm also comfortable with the channels individually, even many individual channels. I just haven't done too much with subgroups at all, never had much need. It's pretty simple, isn't it? About the same is the simpler boards, but just a but more complex? And, how would I adjust the effect that the EQ unit has on each subgroup?

Finally, how can I really use the 32 band equalizer effectively when I'm not 100% positive what I'm doing with the four band on the mackie? I'm not sure what frequencies to boost/cut in order to make a voice sound better/more flattering.

Thanks,
Ben

Ah, thanks again. I'll re-post it there. Either that, or just put a link. I think that will be easier. I'm not sure, I believe that they're omni-directional, just from what I've experienced, but I'm really not positive. We have no monitors. Just the center cluster. It's a high school auditorium, and I'm mixing in the back of the balcony outside of the shittly constructed booth with a noisy AC unit above where I ought to be sitting in there.

The mics are placed on the actor's lapel-ish area. I'd rather run them up and tape them onto their heads or around the ear, but it may not work out that way. I'm not sure what tape would work best there, medical tape doesn't seem to stick. And, that would limit their ability to make effective costume changes. Unless they can clip the mic to their underwear. And, for the actresses, it might be a bit odd to have a 16 year old sound designer clipping a mic to their underpants, as close as I am to one of them.

With the dbx unit, would I run that into an aux send as well, and adjust it on each channel? I'm not that experienced with doing much analog mixing, though it's something that I'm really interested in and am trying to find more opportunities to do.

If all you have available is lapel mics and 4 band EQ then you need to change your career path from sound tech to magician :lol: .
Is it possible for you to hire some headset mics? Since you already have the receivers maybe you could just hire the headsets. I really think you are going to struggle to get any sort of volume with lapel mics.
As for subgroups what model Mackie board do you have? Usually each channel will have switches to assign subgroups in combination with the pan controls. If you are not familiar with the board I suggest you download and read the manual.

I think it's a 1604 VLZ-pro? Less than five years old, but probably four or five. I get the idea of subgroups, more or less, and how to group them... but, more complex mixing techniques involving an externa equalizer like the Behringer DEQ1024 or something. I'm really leaning toward putting the mic's up around the ear or, in some cases, through the hair and onto the forehead... I'm just not entirely sure how to go about doing that. That ought to take care of a lot of the problems, since the mic will be more stable/secure and likely a bit closer to the sound source.

Hiring headset mics is pretty much out of the question. We don't have the budget, and if we do, which it isn't really my business to know as a student, there are better things to use it on. Like a panel saw for our shop. If I propose to rent anything, it will likely be a behringer eq unit. Even that, though, however cheap (100-150 new) might be superfluous.

Any advice with the current setup? Five lav's that distort like crazy, running into recievers under the apron, that then run up through a snake to the mackie 1604 vlz pro. 4 band eq. Center cluster. Orchestra playing, elevated, pretty far upstage.

Thanks!

Ok here's some suggestions
1. Check the audio level from the mic as we discussed earlier
2. At the very least see if you can beg, borrow or steal a 32 band eq, put all the wireless mics to a subgroup and insert the eq over the subgroup.
3. Unless your board is more than 100yds or so from the stage you should be able to connect the receivers to the board with short cables instead of sending the signals through a snake. That way you can keep an eye on the level meters.
4. Go into the hall when nobody is around, clip on one of the mics and say "check one two" many thousands of times while pushing up the level and adjusting the eq until it starts to sound better.
5. Pray a lot

I forgot to say - most important have fun while you're doing it. Trying to get good sound with less than ideal equipment is a great learning experience if nothing else.

Thanks, very much. And, yes, it is a very fun experience. I love just being able to go in there and mess around, rewire stuff, adjust the setup. I'm so grateful for the freedom that the producer and tech director give us. It's awesome. I think that, without them, the experience would just be so much different, much less fun. I'm sure that I wouldn't learn as much, and definitely wouldn't be able to run with as much.

The EQ is not likely. At all. But, it's just occurred to me that we might have a really old EQ unit in our black box booth. That's the only option

Thanks again! I'll try this stuff out.