BillFitzmaurice.info

I will be helping with sound next weekend, and the artist does 4 channel / quadraphonic sound, plus a sub. (The venue is about 20x40, about a 100 standing capacity.)

I have two modern, two channel SS amps, XTi4000 and an Ashley ne800, and a pair of tube mono amps. They're 50-60 watts each, so I'm thinking that due to the "power x 10= doubling of volume" concept, they'll be sufficient.

My problem is this: the tube amps have RCA inputs. Will a standard adapter, ala: http://www.parts-express.com/xlr-female ... r--240-430 , keep the whole "balanced / unbalanced" thing copacetic? Is this even a concern that would cause a problem if not addressed?

Also, the tube amps have old school screw down binding posts, ala: http://www.parts-express.com/parts-expr ... k--090-475 . These supply the amplified signal to the speakers. Most of my speakers use Speakons. I've soldered a couple short bits of wire to the spades of these: http://www.parts-express.com/amphenol-s ... --092-0160 , so that I can wrap the wire around the posts, and plug my standard speakon cable into the connector and on to the speakers. Do I need to be concerned about which spade goes to hot, and which to ground? (As long as they're both set up the same and not out of phase with each other?)

Rich4349 wrote: Will a standard adapter... keep the whole "balanced / unbalanced" thing copacetic?

Converting to RCA makes it unbalanced.

Is this even a concern that would cause a problem if not addressed?

Ground loop noise is a real possibility.

Is this the best / easiest / cheapest solution? http://www.parts-express.com/talent-sxc ... r--233-168

Rich4349 wrote:Is this the best / easiest / cheapest solution? http://www.parts-express.com/talent-sxc ... r--233-168

Unbalanced and the potential to introduce noise reduces with short signal cable runs.
When I say short, I mean like less than 10 feet. Others say a max of 15-20 feet.

So if you need to use the valve amps for the cabs the greatest distance from the main gear, then what you linked looks like a good solution.

If you can keep the valve amps near all the rest of the gear (and use one of your other amps for the longest runs), meaning you can use short unbalanced cables, it's not ideal, but highly likely you'll be fine, without spending more dollars.

Have you got time to try setting up at home to see if it will work?

The next situation is this: how do I go about getting the signal from the mixer into 5 or 6 amps? This is the mixer: http://www.sweetwater.com/store/detail/X1222USB
http://www.mcmelectronics.com/content/P ... -10750.pdf

There are the main sends, then two aux sends: one pre-fader and one post. If I were to use a cable XLR splitter to send to multiple amps, I'm cutting the initial voltage to the amps in half, halving the volume the amps would be capable of creating, right? Not good. (Though for mains, my XTi4000 is serious overkill, and the Ashley makes 225/8 ohms 400/4 ohms, so maybe that's not completely out of the question.)
It seems the Monitor send would be good for feeding into my crossover / amp to the sub.

I should be able to get into the venue this week for a dry run.

I realize I have a lot of questions here, guys. Appreciate the help immensely!

Rich4349 wrote:The next situation is this: how do I go about getting the signal from the mixer into 5 or 6 amps? This is the mixer: http://www.sweetwater.com/store/detail/X1222USB
http://www.mcmelectronics.com/content/P ... -10750.pdf

There are the main sends, then two aux sends: one pre-fader and one post. If I were to use a cable XLR splitter to send to multiple amps, I'm cutting the initial voltage to the amps in half, halving the volume the amps would be capable of creating, right? Not good. (Though for mains, my XTi4000 is serious overkill, and the Ashley makes 225/8 ohms 400/4 ohms, so maybe that's not completely out of the question.)
It seems the Monitor send would be good for feeding into my crossover / amp to the sub.

I should be able to get into the venue this week for a dry run.

I realize I have a lot of questions here, guys. Appreciate the help immensely!

Are you really trying to run in Quad? That would mean 4 different sources. When you mention using an XLR splitter, that would mean sending the same source to different amps....that would not be quad. So, what exactly are you trying to do?

Also, you will need an extra send for the sub....or you will need a much bigger, more expensive mixer to pull this off.....and even then it will be really hard to mix it.

There is a reason the quadraphonic sound failed so quickly back in the 70s.

Bruce Weldy wrote: Are you really trying to run in Quad? That would mean 4 different sources.

Agreed.
The modern equivalent of quadraphonic would be 4.0, or, in your case, with a sub, 4.1.

If it's not strictly quadraphonic, something like a DCX 2496 (with it's 6 discreet outputs, but driven by the L+R outputs from the mixer) would be useable.
Seems that you crossover and power your sub via the XTI 4000.

Can you dry hire a DCX or similar unit?

Update:

Re-read the messages with my liaison; dual stereo will be fine, and seems to be what they've done in the past. His initial request was for me to augment their powered stereo speakers via those speakers' line outs. So it SHOULD be a simple matter to run those into my system as if coming directly from the mixer.

A bad feature of this is not being able to RTA the sound of the primary speakers, unless the sound runs to my Driverack PA+, THEN to the mains, then out of the line outs, back to my amps, then to my speakers. Oy. But if I did that, I'm RTAing two different speakers, which would be finding some average of both of their outputs, which to me sounds like neither one would be EQed correctly. (Perhaps this wouldn't sound terrible to the audience? I know: fat chance!)

Still don't understand why anyone would want to put speakers in four locations in a room that small. If he's not using the extra speakers for effects, then you are just creating havoc with the stereo sound.

That was MY thought, as well. The primary reason I can think of is "But 4 is more than 2! In fact, it's TWICE as much! Oughta be AMAZING!!"

Obviously the artist isn't a member on here!

I'm going to run the risk of alienating myself from the artist and his go-to guy and suggest better sound rather than just more sound. But the artist does "experimental" music, so weird reverb, phase issues, etc, might not only not be detectable, but if they are, enjoyed. Hard to say.

Here are some excerpts from his rider. (It should be noted that this is a very small, *very* low budget art venue, and effectively NONE of his rider items will be provided!

Requirements
1 x Mackie 1642-VLZ PRO MIXER
1 x Projection Screen 10' x 7' (3.05m x 2.14m) x1
1 x Projector Casio XJ- ST145 x1
Plus cables for connection from PC Laptop player / DVD player to projector
(please check /see additional notes on projection set up )
and details
1 x table, able to accommodate for Mackie 1642-VLZ PRO MIXER
Mac Book pro / RME interface / and DVD PLAYER /or PC laptop / Alessis i pad interface
Midi Keyboard / TAGC EQUIPMENT
I understand the sound system will be configured as a quad plus subs system so I would set up my equipment in a central position within the speakers and send my outs to the main mixer via the Mackie 1642-VLZ PRO MIXER so I can control the Levels and the position / panning etc of the Audio my self .I understand from the spec on the Mackie 1642-VLZ PRO MIXER there are 8 direct outs / 6 of which could be sent to the main desk so I can then control level and pan from the 1642-VLZ PRO MIXER.Plus a combined stereo out via the Balanced XLR OUTPUTS

So with the PA+ having only 2 inputs, yet 6 outputs, 4 independently controllable channels are not possible, only 2, right? The other 4 are for separate component speakers (L,M,H), right?

The 1642 will have 4 auxes that can be used as his outputs for the four (quad) mains. The main outs can be used to sum the inputs for the subs.

Panning will be a bitch. Sliders instead of joysticks.

Hopefully the artist will be aware of this.

Complete protection can only be accomplished with three PA+ units (one for subs (most important), one for the front mains and one for the rear mains).

You could use two stereo EQs for the quad outputs, so you can nix the <100Hz content to the mains.
You should at least use the PA+ for voltage protection of the sub signal.

Maybe this will be of some help.

Most of my speakers use Speakons. I've soldered a couple short bits of wire to the spades of these: http://www.parts-express.com/amphenol-s ... --092-0160 , so that I can wrap the wire around the posts, and plug my standard speakon cable into the connector and on to the speakers. Do I need to be concerned about which spade goes to hot, and which to ground?

That should be fine.
Convention says +1 will go to the positive output (hot), -1 will go to the negative output.

There are the main sends, then two aux sends: one pre-fader and one post.

You've confused me, are you now talking about sending from your mixer outs to a Mackie 1642 (which you don't have)?

Anyways, 2 mains out on your mixer go to PA+ for subs and left + right front, then use the 2 aux sends for the "rears". One of the aux sends being post fade doesn't matter, as long as you don't change the channel strip fader in the show, (unless you also increase aux 2 at the same time)...