Speakers for auditorium sound?

Question

I'm doing a series of iPhoto slide show presentations using a projector. Do I need to get a good set of external speakers? The projector is an InFocus X3, and I think it has some sort of built-in sound, but I was just wondering if anyone knew the best way to go, or even IF a pair of external speakers plugged into the headphone jack would be good enough sound for auditorium use (about 400 people in a room with rather bad acoustics).
Anybody had any experience blasting music through an iMac (with external speakers) to a big party or something? What's a good set to get?
Thanks for your help,
Julie
20" iMac G5 2.1 GHz PowerPC   Mac OS X (10.4.4)  

Answer 1

cool... more details on the room.
Presuming you ARE working from a stage AND there are mic jacks on the stage:
Audio:
I did this recently for a Macintosh User Group meeting... Using a small 4-8 channel mixer (if one is available - if not, keep reading), connect the iMac to the the small mixer previously described. Connect the "Main Out" via XLR cable to the mic jack on stage. iMac audio level at 1/2... small mixer audio level at about 1/3 and gain (if it has a separate knob) at about 1/2... and let the main board operator take care of everything else. Since you are feeding into only one mic jack on the stage, this set up is mono only. Stereo capabilities will also depend on the main board and amp set up, so I won't go there). If you need to adjust sound and the main board is not accessible, up the level and gain on the small mixer first - if you need more, LAST recourse is to increase the iMac's audio level - when is starts to sound scratchy, back off until that goes away.
Guitar Center has several small mixes <http://guitarcenter.com/products/dispDeals.cfm?sel=7>... Behringer is another one they carry in their sotres - but not advertised on the web site. They are all around $150 to $300. If you'll never use it again, it may not be worth it, but the site manager might be interested. I generally use them for a drum-set (which can use 5 mics or more - if synth drums are used, too) - or this sort of "can't get to the board, so this 'pre-board' will have to make due". At the Mac User Group meetings, the main sound board is locked up in a back room, but always-on so the school principal needs only plug in a mic and start talking.
If a small mixer is not available, then feeding the left and right audio from your computer into a single on-stage mic input jack is the way to go. In the previous post, one of the shopping items was a 1/8" male head-phone to left-audio/right-audio "tail". Instead of that, get a 1/8" male stereo headphone to mono RCA female. This connects from the iMac headphone jack to the male RCA audio cable on one end. The other end connects to a female RCA-1/4 in male... which connects to a 1/4" female-XLR male... which plugs into the stage female XLR mic input.
If there are no mic jacks on the stage and the site manager is using a snake, then just treat the XLR connectors on the stage-end of the snake like you would if you were plugging into the board itself. The site manager should be able to assist with this.
Video:
Presuming you already have the Apple video converter tail for your iMac, you can get a VGA video cable as long as you want... Fry's Electronics (Outpost.com online) has LONG ones... http://shop3.outpost.com/product/4473316?site=sr:SEARCH:MAINRSLTPG There are likely other sources, but Fry's is nearby for me. If this link does not work, got to Outpost.com and search for "vga cable".
Measuring the spot from where you will be speaking - presuming the same place the iMac is - to where the projector will be and add at least 10 feet... remember, the cable on the floor needs to get up to the iMac (on a podium) and up to the projector (on a table?). We live in a 3-dimensional world...
Other logistics...
Don't forget duct-tape... the cables need to be taped down to the floor so people don't trip. The site manager might take care of this, but one can always use duct tape elsewhere, so just be sure to bring a big roll. Heck, leave it with the site manager if that person does take care of it... I guess that's up to you.
If at all possbile, make arrangements with the site manager and set up everything to be sure it all works - and you are comfortable with the sound-levels, video cable and all the other hook-ups. Presuming no one else is around, doing a short test with your computer and everything plugged in a couple of days before the FIRST time will ensure you have the right cables, adapters, and even sound levels... so that you have time to recover and get stuff just in case... AND be sure to mark all your cables and adapters and gear so everyone knows who owns what. White tape with your name (use a Sharpie) is easiest (though removeable - so pros and cons to that).
... and if you are speaking - hence, mic'd up - a handheld mic (better yet, a wireless lavalier) should be used so you don't have to scream at your audience - and you want to be comfortable with that, too. If handheld, is there a mic stand? Is it connected to the podium? Will that get in the way of the iMac monitor? A stick or boom mic stand (not part of the podium) might be in order - the site manager should be able to address this since you indicated there are mics... If you use a small table next to the podium for thee iMac, a lavalier (clip-on mic) would be easiest since it will leave both your hands free to use the computer while you are speaking. If a lav is not available, a couple of mics (one at the podium and one at the iMac on the table) might be in order. A wireless hand-held mic will also be useful if available (hold mic in one hand while using mouse with other) which would make the multiple wired mics unnecessary.
By the way, what's the show about?
HAVE FUN!