Gain structure questions not covered in read me or FAQ's

The Slice

Okay, I've posted here before on the system I am using at a church. I understand the basics of setting the gain structure. The problem: The speaker being used is a powered unit and, cannot disconnect speakers from amp without disassembly, and second, setting the gain to the level of clipping, would be way to loud for the room. I have done a little better by getting the relationship between the mixing console and the DRPA so that I'm getting better results from compression, limiting, etc.. The gain on the speaker-amp is down almost to the point of dropping out all together. I'm also wondering if this is having an effect on the sound. Would using an attenuator between the DRPA and the speaker-amp help?

Equipment:

Ramsa 4416
DRPA
Samson powered amp (Yeah, I know, Iknow, but it's what I can afford)
I should note that it's divided to 50 amps for highs, and 150 for lows, and has single input to onboard crossover.


I know I could do much better, but they actually don't sound too bad, and I don't do very much of the sound work - nothing outside the church stuff. If I were in to this for money, it would be different.

Gadget

I'd set the Sampsons @ 50% and get as good a gain structure as you can through the DRPA then let the MASTER faders on the mixer be the final volume control... if they are only @ -40 db so what.. as long as the sound is quiet and you have lots of headroom your fine...
Gadget

The Slice

The only problem with that is that it brings the input level to the DRPA so low, that the compressor and limiter are almost ineffective. While I'm here, I have another interesting phenomenon happening, that seems to be intermittent. I'm getting what sounds like a kind of strange reverb. It's only a single repeat, like what you would hear if you were recording in the room with a three head analogue tape deck and listening to the playback rather than the input signal. I'm almost positive that it's coming from the front of the sanctuary. as opposed to sound bouncing off the back wall. I don't know if it's a delayed signal due to the compression (if that's possible), or what. It's far worse when the pastor is in front of the speaker. The speaker is about 6 - 12\" away from the front wall, and about 3 - 4' from the side wall, and is on a stand so that the bottom of the unit is about 6' in the air. The pastor at this time is in a position that's about a foot or so in front of the speaker with his back to the speaker. I'm using a Shure, cardioid lavalier mic and actually have no problem with feedback. The other interesting thing is that when he's there, the sound becomes a bit muddier and sort of muffled as well.

Gadget

Then use a combination of the crossover gainson the DRPA and the controls on the speakers to lower the output to the sampsons... you also have the input gain switch on the back of the DRPA that will lower the input sensitivity to -10....seems kind of strange to use compression on a church system... are your using both at the same time?

try turning the speakers so they crossfire to avoid the back wall and see what happens (as a test) comb filtering will be worse but...

Try this...
http://www.mcsquared.com/reverb.htm
play the various files and see if they match up with what your experiencing.

A lav...with speakers BEHIND the speaker...YUCK... sounds like a recipe for disaster...

Those speakers should be center clustered and aimed down on the congregation...so the sound gets on the people and off the hard surfaces...if that isn't possible... treat the back wall if possible...

G

The Slice

Thanks Gadget. I already have the gains way back at the crossover (I think to about -12 dB) to get a faster response for the AFS, or more appropriatetely to get an earlier response from the AFS so that the \"ringing\" doesn't get to annoying levels before the AFS responds. BTW, I'm only using one speaker, as two would be way too much for the room. I know this is not the best. Perhaps here is where I can ask advice on a better setup. I want to fly a single speaker (Ramsa WSA 80), but have to use what's available as we don't have the equipment to access the upper aspects of the ceiling without renting a lift. (It's a vaulted ceiling that parallels the roof line and is somewhere around 20' at the peak, or higher. My idea originally was to make use of two screw eyes already in the beams, and suspend a pipe from ropes from them and secure the speaker to that. The problem is that the eyes are about 9' apart, and about 6' from the peak of the ceiling. The pastor doesn't like that idea (appearance wise), and also thinks that the congregation may object as well. My thought was to fly the speaker from one of the eyes. The questions are: will the speaker being ~ 4.5' off center make a big difference, and does anyone have an idea of how to secure the horizontal axis (L - R) of a speaker when it's suspended off of a single line? I may be able to attach something to the speaker that will stabilize it against the beam as a way to do that. P.S. I can get a pull, or pilot line up and through the eye without having to go all the way up there, and then use that to pull a heavier line up and through. There's also another eye near the wall where the beam changes from the diagonal to vertical. This will keep the rigging line and the speaker cable out of sight. The other option is to make use of the column speaker that's already up there, and use my own amp to drive that. That's not a great option either as I've tried doing that before by sending the output of the DRPA to the house system (an in wall amp, and the speaker) with the system EQ bypassed (off). It's great for regular speech, but for music, it stinks. I was thinking about hooking up my own amp to the speaker itself, but when I checked it out, it seems as if the wires (2) are connected to the 16 ohm output of the amp. I'm not so sure that this is a good idea for an amp that's rated for an 8 ohm output. I suppose the only way to find out for sure is to put a meter across the speaker wires and confirm what the resistance is. The column is a 4 speaker unit with something like 6x9\" speakers. It's not surprising that the sound coming off it would be lousy for music, as the speakers are just too small to carry the lower frequencies well. One other thing that I'm curious about is whether bypassing the whole amp itself (a Rauland Borg) and driving the speaker column off a Biamp dual 100w amp, would it likely make a difference, and can I somehow negate the 16 vs 8 ohm impedance problem, perhaps by by bridging the amp without having to get into the column?

Gadget

You couldn't post a picture could you?

Didi you listen to the links I sent? and what is your thought there?

G

The Slice

Okay, I have a bit more information for you. To start with, the dimensions (approximate) of the sanctuary. This does not include the stage/altar area. W 38' L 51' H to top of wall 13' Estimated height from floor to ceiling 20'






This is a wide shot of the sanctuary. In this picture, you can see the relative position of the pastor to the speaker during the \"joys and concerns\" (at the candles).




This shows both the eyes into the beams, and the back of the column speaker. The eyes are ~ 11' apart which would put each eye ~ 5.5' off center. Picture taken from the altar area.






This is a little closer shot of the altar/stage area. If you look at the \"corner\" where the upper level (top step) is, it is approximately the position of the eye in the beam above. These beams are ~ 3' forward of the stage/altar area.


So far as the samples go, nothing really fit what I have heard from time to time. What I've heard is only a single repeat a fraction of a second later. I'm wondering if the compression, or limiting has something to do with it. I shut off the comp and limiter yesterday and did okay, but what I found interesting was the change in the pastor's voice (through the system) and found that I needed to make changes on the channel EQ for his mic. Shure receiver (not sure which model) with WL 185 mic.

I was under the impression that I needed to use compression to compensate for the changes in the relative position of his mouth to the mic, and limiting as a way to insure no feedback beyond the AFS (levels just too plain high). Two questions, will the adjusting of the gain at the xover have an effect on the EQ, or anything else? I did a little experimenting yesterday and went even further down with the gain for the pastor, and brought it up for the youth choir (not as strong, and further from the mics). Second is whether that 5.5' off center for the speaker will have a noticeably negative effect on the sound? It can't be any worse than the other speaker where it is, which is somewhere about twice the distance off center.

BTW Gadget, I love your avatar, but it's a little sadistic isn't it?

Gadget

ABSOLUTELY NOT! NO don't even consider hanging anything but banners from those eyelets! :shock: ESPECIALLY with rope!!!

I will have to get back with this later...

As for the avatar.. I get frustrated sometimes... 8) what can I say...
G

Dennis

When hanging anything overhead, think \"steel\". For suspending speakers, use rigging chain or 1/8\" to 3/16\" stainless steel cable. The cable looks better than the chain if that is an issue. A riggers nylon spanset would easily hold the weight but you would need a steel safety to go with it because nylon burns/melts.

Your overhead hang points should be machine threaded eyebolts that go through the entire beam and have nuts on each side of the beam. The eyebolts must have an adequate advertised weight rating with at least a 5:1 load factor. It would be even better if you hired professional riggers to install your overhead hang points. They are expensive but much cheaper than a lawsuit.

Your speakers must have flypoints on them. DO NOT HANG THEM FROM THE HANDELS. If they don't have flypoints, you will have to install some. Check out ATM Flyware for rigging solutions: http://www.atm-fly-ware.com/

It is unsafe to try to rig speakers at 14' to 20' without a scissor lift or some form of personnel lift. Rent one for one day. It's less expensive than a hospital visit.

Dennis

Dra

Dennis, good advice. I will add one thing, though. If you are bolting through the beam (horizontal to the floor), be sure to check the shear rating of the eyebolts. Usually considerably less than the load rating. Get threads as close to the eye as possible. If threads are not close enough to the eye, stack washersand jam them tight with a nut. Also, get the eye as close to the beam as possible. Use fender washers to get the greatest clamping force on the beam or better, plate. Like Dennis said (sort of), ain't no such thing as too big. One last thing, many use a back up suspension if the first should fail.

DRA

The Slice

Wow! First let me make it clear that the unit you see in the picture is NOT what I was planning to fly - it's way too heavy. What I was planning on flying was a Ramsa WS A80 which weighs about 7.5 Kg. - 16.5 lbs. The eye in the beam is about 1/4\" diameter steel (hard to tell from photo). I have a hanging chair in my place with a screw eye of approximately the same size that I use, and I'm at least 10 times the weight of the speaker. I would also think that an eye screwed into a beam perpendicular to the direction of the load is actually stronger than one with the load along the axis of the screw part of the screw eye. The speaker is molded plastic with the handle as part of the molding as opposed to a handle that's attached. There are also threaded inserts into the plastic for the mounting bracket. There are two types, one for stands, and the other for ball mount brackets that the speaker can either sit on, or hang from. So far as actually getting it up there, I have a way of rigging a very long pole with a clip to hold a string and weight to drop through the eye, then using that string to pull up a heavier line. So far as material to hang it goes, I actually have plastic coated wire (steel) which I think is either 3/16\" or 1/4\" (the wire itself).

The bottom line is that the powers that be within the church see what I'm doing more as \"icing on the cake\" rather than something that's really needed. Along with that, we are a church that is struggling to survive in several ways. While safety is of the utmost importance, money is tight both for the church and myself, so my options are limited.

Now, with that aside, as a possible option, I have tried using the house system by feeding a signal to the house amp and bypassing the EQ on the unit. The sound wasn't all that great with the column. Fine for speech, but lousy for music.What are the chances that I could get better sound off of the column by driving the column directly from another amp. The house amp is a 35 watt Rauland Borg. The other amp is a GLI 100 watt/channel 2 channel amp. The problem is that the speaker is hooked up to the 16 ohm connections on the RB amp. I'm not sure how the GLI will handle the double impedance

Dennis

Is the speaker that you want to hang heavy enough to hurt someone if it falls? If you don't have enough money to fly it correctly, you don't have enough money to fly it at all. Stick with your tripod stands.

We can come up with ways to cheat when you are wiring up electronic equipment so you might use a wye cable or some other widget to make a piece of gear do something other than what it was primarily designed for but no one on this forum is going to endorse substandard rigging practices. It could come back and bite us.

Dennis

The Slice

Okay, I've given up on flying the speaker for now, certainly with the plans I had.

So now, how about the other questions? The house system has a Rouland-Borg amp in it (35w) plus the column speaker shown in the pics. I have tried already feeding a line level signal from the DRPA to the Aux input using a matching transformer to go from balanced to unbalanced. With the EQ on the R-B bypassed, the sound coming from my system sounded a little better, but not much. The first question involving this is whether there is likely to be any improvement in the overall sound, if I just disconnect the speaker and drive that from a GLI 100/channel amp? I suspect that the bottom line is that it's not a question of what amp, but but the speaker column itself. I'd just like to confirm that if possible. As I said before, the house system is great for speech, and is nice and clear, but not for music as it's missing upper and lower frequencies. Am I correct that it's okay to run a higher load (impedance), but not a lower one unless the amp is designed for it?

To the question on the DRPA. I've found that I can solve (at least in part) the problem of running the amp at such a low level (almost to the point of cutting out. I'm doing this by dropping the signal at the xover. This was a suggestion made earlier to get a less audible response when running AFS. If I change that level after running EQ and AFS, will it affect either?

Gadget

UFDA...

Well... the column speaker is a \"fullrange\" cone only speaker that is DESIGNED for speech only...why not take that down and put a REAL speaker where it was..although sending the sound through those chopper blades is a real NO NO...as for the 35 watt amp... are you kidding? speech only, nothing more through that...you would need a speaker of 90 degrees in that position though... how about one that has a vertical pattern that coupled with the horizontal covers the people and not the spaces...? maybe move it back one column to avoid the fan and make sure the vertical pattern is over the head of the raised stage area...Hey, you have a beam... you can make t work, it's just a matter of making sure its safe...

What is the coverage pattern of that speaker you want to fly? USUALLY in a church of that size we would spec 2 speakers with 60X40 patterns for a 120 degree horizontal, or with a rotatable horn for 80 degrees horizontal and 60 vertical.. this helps keep the sound OFF the walls and ceiling, and on the public... If you have the speakers too far toward the audience/congregation, you will miss the first few rows...

Gadget

The Slice

Hey Gadget, thanks for the reply. Your response doesn't surprise me. That's pretty much what I figured. For the time being, I'll just have to stick with the set up that I currently have. Yes, I know that's not ideal either, but it's better than going back to the house system. To the other question, will cutting the gain at the xover be essentially the same as putting an in line attenuator between the DRPA, and the amp, or will it affect anything set in the DRPA.

Do I want to know what UFDA means? Does it end with \"Ass\"? 8)