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Old 9th April 2012, 07:26 AM   #1
kctess5 is offline kctess5  United States
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Default PA System Design

So here's the deal...

Next year I will be building my school a PA system as a senior project. I won't actually be starting on it until after the summer but the ASB director has asked me to do a rough budget to present to the ASB to get their okay on the project.

I will have roughly a $5000 dollar budget, I plan to try to work with home depot, parts express, etc to get donations and or discounts so if the design goes over that budget I could probably make it work.

I want to be able to hit incredibly loud levels with this system as our school has a habit of destroying systems by pushing them beyond their limits, I'm thinking somewhere between 140 and 150 dB as a rough guideline.

I've got the low end part of this covered for the most part, I plan to use 4 of the C/E/X PA or similar which I think I can pull off for under $2000.

What I'm not so sure about is the mid-treble range. I want it to have as high dispersion as possible, be almost as loud as the subs (considering the kind of music that will be played its ok if they can't handle quite the same levels), and relatively easy to move around. They should cover 100Hz and up. I plan to build two of them. I'd love to horn load everything for higher spl but I don't know if its better to have direct radiating mids for the just over 100Hz range

I'm not honestly sure what my school has in the way of amps, crossovers, equalizers, soundboards, etc, but I can find that out sometime next week, but I won't worry about that until I know what kind of power I will need.

Can anyone point me in the right direction for the top speakers? If there are any designs or papers I should take a look at let me know.

Any general advice would be appreciated! I don't have much experience in the way of PA systems as I usually do home audio.

Thanks in advance!
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Old 9th April 2012, 08:49 AM   #2
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You will need horn loading, and you will need multiple boxes per side. Have a look at the Speakerplans site and forum. Something like the MT122 should do the job, though I'm not sure it gets down to 100Hz. Don't forget to budget in the price of hardware like wheels and handles and suchlike.
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Old 9th April 2012, 09:51 AM   #3
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4x Punisher Bass horns and 2x X-Tro top cabinets will get 140dB spl with H60 x V40 dispersion.
Speakerstore
Speakerstore
Info on x-over settings here:
Punisher Horn II

But only from 50Hz up so that could be a problem.
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Old 9th April 2012, 10:40 AM   #4
kctess5 is offline kctess5  United States
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I've been looking at all kinds of different options for the past few hours and I think I'm starting to lean towards the Bill Fitzmaurice DR250. I could build 4 of them and it would be modular enough to use at our football field and also at our small outdoor stage for lunchtime events and the like.

And I really like the C/E/X subwoofer. The size/transportability are good, the drivers are (relatively) cheap at ~$300, its got great output, and it doesn't look hard to build.

Finding info on the BFM tops is tricky without his plans, I can't even find the max power handling right now, but I gather that 4 could hit pretty close to 140dB, and their dispersion is perfect for the stadium with a bit of a tilt upwards on the top speaker in the stack (about 10 degrees). I also can't find anything about the cost...

Quote:
4x Punisher Bass horns and 2x X-Tro top cabinets will get 140dB spl with H60 x V40 dispersion.
Speakerstore
That first link has a really interesting design, I'll look into it, it does look a bit big. I wouldn't mind the size but I'm not the one who will be handling the system (scary!)
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Old 12th April 2012, 12:02 PM   #5
brig001 is offline brig001  United Kingdom
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I don't think you are going about this the right way. Making something louder won't stop them destroying it, just more people will suffer hearing damage in the process. Remember, there is no safe exposure time for >115dB.

Get a good compressor/limiter, set it up to give a sensible maximum SPL, put it in a box and lock it. Now it is much harder to damage the PA and peoples hearing.

Brian.
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Old 7th July 2012, 02:12 AM   #6
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Have you built your subs yet? I would suggest the Xoc1 TH-18. The C/E/X 6 Fold 18" TH is quite massive in size and the TH-18 plays louder (what you're asking for). The 6 Fold also requires a bit more timber.

And, yes, with proper gain staging and a brickwall limiter, you shouldn't have problems with blowing drivers.
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Old 7th July 2012, 02:41 AM   #7
kctess5 is offline kctess5  United States
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Hmmm good idea. Very tempting. I don't think that extra size, timber, and less efficiency is worth it for 8 more Hz. With the B&C 18PS76 (which I ordered) it models ruler flat from 45Hz to 130 Hz with an F3 of about 39Hz. Also the extra height and higher aspect ratio would make it easier to wheel around

I've already ordered all the stuff from PE but it looks like it would be fine because the general layout is similar, it's just the wood thats different. And I could order one less sheet so my surplus budget would go from $300 to about $370

I don't start building until the beginning of the school year, I have 2 class periods to do it.

It's about 3dB more efficient for this driver so my 300 wpc crown amps will be able to do quite a bit more damage. 137dB according to hornresp

Thanks for the tip
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Old 7th July 2012, 03:42 AM   #8
imix500 is offline imix500  United States
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Hi kctess5,
Just chiming in with a few questions about power and processing-

Are you bridging the 300 W/ch Crowns one per sub? It might be good to have around 1kW available to each driver for maximun output if possible.
Just curious if you already have amps for the tops as well?

Also, do you already have processing? Going by Bills posted chart of the Dr250 it would be wise to have parametric filters available (just quickly counted six spots) to help smooth them out esspecialy around 10k where the piezos can be a bit unsettling.
Cheers!
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Old 7th July 2012, 04:43 AM   #9
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Quote:
Originally Posted by kctess5 View Post
Hmmm good idea. Very tempting. I don't think that extra size, timber, and less efficiency is worth it for 8 more Hz.
It wasn't for us - not a significant enough of a difference. But, the extra SPL from the TH-18 was worth going that route. After even MORE wood for bracing the TH-18, and the little bit extra effort to maneuver them compared to the SS15s, it was the right decision. The 6 Fold would've taken a LOT more wood and been MUCH heavier.


Quote:
Originally Posted by kctess5 View Post
With the B&C 18PS76 (which I ordered) it models ruler flat from 45Hz to 130 Hz with an F3 of about 39Hz. Also the extra height and higher aspect ratio would make it easier to wheel around
Perfect!


Quote:
Originally Posted by kctess5 View Post
And I could order one less sheet so my surplus budget would go from $300 to about $370
Maybe you mean $370 to $300..? You will need more wood for the 6 Fold after bracing and cone make-up is taken into account.


Quote:
Originally Posted by kctess5 View Post
I don't start building until the beginning of the school year, I have 2 class periods to do it.

It's about 3dB more efficient for this driver so my 300 wpc crown amps will be able to do quite a bit more damage. 137dB according to hornresp

Thanks for the tip
Glad I could help! Happy building!
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Old 7th July 2012, 06:09 AM   #10
kctess5 is offline kctess5  United States
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Quote:
Maybe you mean $370 to $300..? You will need more wood for the 6 Fold after bracing and cone make-up is taken into account.
Wait a little confused...

Quote:
The 6 Fold would've taken a LOT more wood and been MUCH heavier.
If the original plan was to build the FT30 6 folds and I changed it to build the TH-18 wouldn't I need less wood than originally budgeted? Isn't that what you just said?

Quote:
Are you bridging the 300 W/ch Crowns one per sub? It might be good to have around 1kW available to each driver for maximun output if possible.
Just curious if you already have amps for the tops as well?
No thats not quite in the budget. I'm going 1 Crown XLS 1000 DriveCore Series Power Amplifier Flexible for Any Pro Audio Amplification Need 245-500 per 2 subwoofers so one on each channel. I didn't think the relatively small output increase of 3 dB while having to spend $600 more and worrying about power compression, over excursion, etc...

And I'm using the same amps for the tops also. I don't actually have any of the amps but the purchase orders have already been sent pending delivery in August, it's complicated.

Quote:
Also, do you already have processing?
I'm getting a dbx DriveRack PA+ Complete Loudspeaker Management System 246-171 to handle limiting, delay, eq, crossover, and all that fun stuff. I'm excited to get to use it actually, it seems quite capable.

Quote:
10k where the piezos can be a bit unsettling.
I'm using the compression drivers
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