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Old 10th September 2012, 01:13 PM   #1
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Default DIY PA speaker build - need advice please

I am planning on building a PA system for my cover band to use at rehearsals and live gigs (200 - 300 people max). Our budget is very tight and that's why I'd prefer to build it myself rather than rent or buy... If you could offer some advice I would really appreciate it.

So far I have a small Behringer Euroback FX Pro mixer and an old two channel mosfet amp running at 500w per channel (unsure of the output impedance). I have been advised that 8 Ohm speakers will work fine, but I would like some more advice on this. More specifically, what sort of speaker configuration will match the amp and sound good at gigs?

I was considering running 2 x 12" 400W drivers and 2 x 18" 550W drivers (all 8 Ohm), but am trying to determine the best way to wire them. Maybe a simpler way to go would be to find and follow a tested design for a 15" driver and just build 2 of those with one driver in each. I am open to suggestions...

Am I on the right track? What advice do you have?
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Old 12th September 2012, 03:38 PM   #2
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Check out the forums at speakerplans.com, they are pretty interesting.

Eminence and selenium drivers seem to be regarded as the best value drivers in general.

Sounds like you need a pretty standard system, some tops consisting of a 1" horn and 12" midwoofer, and some subs, typically 15" or 18" in folded horn/tapped horn or maybe bass reflex.

Most people would run this as an active crossover system with a line level crossover/processor and 6 (3 per side) amp channels.

Budget wise, for something like this, $300 for drivers for tops pair, $300-500 sub drivers pair, $600-800 two more amps, $300 processor, plus wood for boxes, paint, hardware, connectors, cables, grilles.

So, not cheap or easy, but that's a real pa system. Start cutting corners from there at your own risk.

If you REALLY want cheap and easy and pretty good, go to your local guitar center and pick up a pair of used Peavey PR15's. For a few hundred dollars you get a viable speaker that's pretty decent without a sub, is light, and plugs right into your existing gear. Plenty for mic'd drums and vocals. It also has resale value when you're ready to upgrade.

(disclaimer: I'm not a PA expert, ran sound for some friends band many years ago, and just recently been looking to put together a small system)

Last edited by turbodawg; 12th September 2012 at 03:41 PM.
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Old 18th October 2012, 04:02 PM   #3
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Hello

I'm not sure if this the place to ask this question, but which is louder type of cabinet?

folded horn (front or rear loaded)
ported cabinet
sealed
scoop or hog scoop
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Old 18th October 2012, 04:31 PM   #4
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It's a little complex, but also easy : pick a 18" with high excursion and feed it with thousand of Watts
Usually it is done in that way. Amplifiers are now light & powerful, and subwoofers need to be portable and stackable.
Like member Turbodawg , I put the disclaimer that I'm not into pro sound-
me not at all !!
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Old 18th October 2012, 08:08 PM   #5
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For this you might well need a system that only goes down to 100Hz. an un amplified drum kit can be loud enough for this type of venue, and if the other instruments have large enough amplifiers these need not be mic'ed..

Bass bellow 80-100Hz. costs money and it is a lot cheaper if you can avoid amplifying it with a p.a.
rcw
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Old 18th October 2012, 08:42 PM   #6
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I'm looking build one of these for DJing. Crowds range from 100 to 500 people, just looking what will give good coverage, weather full range or sub!
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Old 18th October 2012, 10:57 PM   #7
Enzo is offline Enzo  United States
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I have to agree with turbodawg, look at some used gear.

In general, building your own stuff from scratch is great if you want a project or just the satisfaction of building something, or maybe you want some specific features not all available in one commercial unit. But DIY is usually not a way to save money.

Your home made speaker will need the boxes, and covering, the woofer the horn driver and horn, the crossover and jack plate, probably handles. Add all that stuff up for dollar cost. Now look what you can get in the used commercial gear for $200.

In Pro audio, certainly Peavey makes good sturdy stuff and it is not usually high cost. Yorkville speakers do not have any snob appeal as a brand name, but the gear is well made and you get a lot of speaker for the money. On the use market, these brands are good to look for.

Louder is a complex question. All else being equal, sometimes there is a trade off, one speaker may be louder, but has a more limited dispersal pattern. You have to think about your audience. You don;t want to beam your PA sound right at one or two tables square in front of you, you want it to spread across the audience. That is more a matter of the dimensions of the gig rather than strictly the number of listeners.

One other thing, in my opinion, remember this is a dance bar, not an audio engineers convention. The dancers at your live gig, or at your DJ gig, are not sitting there in the stereo sweet spot critically listening to every sparkling high and each snorting bass of your music. They are there to dance, get drunk, meet women or men. They are not thinking that gee your midrange is grainy on the left side or that the stereo separation is less than optimal. As a former pro soundman, I usually ran my mixes in mono anyway. In a dance bar, in stereo, the tables on the left only heard half the music, and on the right, the other half.
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Old 19th October 2012, 11:57 AM   #8
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LOL, I understand, that makes sense.
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Old 19th October 2012, 12:42 PM   #9
AndrewT is offline AndrewT  Scotland
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I have not seen it in the earlier replies,
Dedicate one amplifier to each speaker.
Lose one speaker or one amplifier and the gig goes on.

doubling up speakers from a single amp just because the spec says it can drive 4ohms or 2ohms means you lose many speakers if the channel goes down. Could that be "end of gig"?

And possibly more important:
dedicate a channel of mixer output + amp + speaker for the main Vocals/Singer.
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Old 19th October 2012, 01:21 PM   #10
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It would be good to post what amps those are??
Pix if they are not well known.

A bit depends on how much gear and boxes you are willing to haul around to a gig.

The usual "PA" set up gives what I call "boom and sizzle".
Awful bright brittle highs, and some sort of boom in the bass, not much flatness or clarity in the mids. Worse if some fool turns the "treble knob" on the mixer.

I'd suggest that the usual 1" horn and driver is a recipe for horrid sound, unless ur very careful and know what you are doing.

Otoh, the more you can pack into a horn in terms of frequency range, the easier it is to make it sound good, but the horn gets bigger and heavier.

The other thing is to make sure that you never clip the amps.
So, you need to run in the middle of the power range, which of course is *impossible* with a PA that is not over sized and over powered. So the only other option is soft knee limiters at least between the mix board and the amps. If you want to get slick, then they are on each channel of the board (in or out side, your choice). This prevents any clipping.

But bands that do this often run their sound into heavy compression by playing loudly on stage and also getting too much stage sound into the mics.

It is one thing to try to amplify vocals, another much more difficult job to amplify instruments, and nearly impossible to do well is mic'ing drums. Until you get to a pro level system, and a pro engineer to do the mix.

You can consider a Class D amp for the bass. Light, cheap, powerful. That's a good idea.

Keep the analog mosfet amps for the mids and highs...

Of course you can't run hundreds of watts into a single tweeter either...

The only other free advice I'd give is to build in a roll off on the tweeters above 10kHz. Most of what comes out there in a live gig is IM and hash. Being down 6dB @20kHz is a blessing. You could simply drop an inductor in series... I'd actually start the rolloff a bit lower in freq myself.

Btw, the twist of the "treble knob" is usually to get more presence (2-5kHz) but what it gets is usually a monster boost at the extreme high end, which has little or no benefit to the listener.

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