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-   -   The cheapest PA system (http://www.diyaudio.com/forums/pa-systems/134125-cheapest-pa-system.html)

andrew_87 1st December 2008 06:45 PM

The cheapest PA system
 
Hi guys! :)
i'm here to show you my new project: a PA system with a super performance/cost quotient.

target:
- f. response: 45hz(f3) - 16000hz circa
- hi max spl (near 140dB)
- stack use (0.5phi)
- low cost


after some ideas i have realised that to contain cost i have to create a 2way system:

- low frequency: 45hz to 500hz (if it is possible highest, like 800hz but i will test it)
- hi frequency: 500hz (800hz)to the highest possible frequency
- eventually piezo tweeters

to have a very high SPL i decide to use horns: frontloaded horn is probably impossible (due to freq. range), so i will project a rearloaded horn, i don't really like rearhorns but in this case i will use! :)

the driver that, in my opinion, has the best performance/cost quotient is the Skytronic 902.442:

http://export.skytronic.com/product/....php?s=902.442

a cheap 12" whit big voice coil (100mm) and good t&s for a horn.


Here is the project using HornResp:

http://img88.imageshack.us/img88/710...respyz5.th.jpg


and here is the project using AJhorn:

http://img89.imageshack.us/img89/9052/ajrespbr5.th.jpg


GOOD! (in my opinion) :D


i would create 4 scoopbin, so i can create a stack and work in 0.5phi... probably i can get 140dB whit only 1.2KW from this bass system... :bigeyes:



for the high frequency i probably use this compression driver (but i don't know if they can go to 500hz):

http://www.usblaster.com/Products/DJ...ers//USB%20387

or this:

http://www.usblaster.com/Products/DJ...vers/USB%20384

(probably the first)

in my opinion i need 4 compression driver with few watts: so i can improve the durability of the system.


what do you think about this crazy project?
:D :D :D :D

andrew_87 2nd December 2008 11:24 AM

no opinions?

:)

HK26147 2nd December 2008 05:58 PM

My opinion - though you may not not want to hear it is:
A 2 way PA with a clean output of 140db is a lofty goal. I won't say it's impossible, but you want it cheap as well?
I am unfamiliar with those drivers you mentioned, nor have I seen any feedback on them... Based upon the pdf specs:
The 12" driver has only a 4mm excursion - Excursion limited and Insufficient to generate that sort of SPL before mecahnical damage or thermal failure, I'm guessing.
It's been my experience that a PA made from cheapest parts can not be made to sound good, and will not be very durable and robust.
There is a huge sonic difference in a PA made with cheap parts and one made with name brand drivers.
You pay a lot of money for a driver like a 2206 or a 2226, but after over 8 years and thousands of watts they still sound better than new OEM drivers.
I repair drivers and so I would rather repair a used/damaged ( cone tear etc ) JBL then buy a new OEM despite price.

andrew_87 2nd December 2008 06:21 PM

probably 140dB is too high for my application... and this is impossible for this kind of product...
I will test the woofer and the driver, after this i will decide...
:)

thank you for your opinion!
:)

andrew_87 2nd December 2008 06:52 PM

anothor thing, what do you think about my rearloaded horn project?

thanks

Cal Weldon 2nd December 2008 06:59 PM

By the time you reach 140dB your nose starts to bleed.

I agree with HK, 140 is a bit lofty. I run 6 15" horn loaded Selenium PA woofers plus 2 horn mids and 2 horn tweeters and expect a clean 125 dB with 1.5K of power.

Tell us what these are for, maybe we can help.

andrew_87 2nd December 2008 07:03 PM

i have calculated a theorical spl at 1 meter in a 0.5phi emission...
so real 115-120dB are enoght! :)

i would create this system for a carnival wagon...
:)

HK26147 2nd December 2008 07:37 PM

Forum member Davygrvy built 6 horns each with an Eminence HL10 ( Total Driver cost $780 ). These horns formed a fairly small stack.
And when given enough power produced painful SPL.
I used to set up a parade float sound system myself, and I'm guessing his stack would fit your carnival wagon system.
But not as a 2 way.

andrew_87 2nd December 2008 07:45 PM

Quote:

Originally posted by HK26147
My opinion - though you may not not want to hear it is:
A 2 way PA with a clean output of 140db is a lofty goal. I won't say it's impossible, but you want it cheap as well?
I am unfamiliar with those drivers you mentioned, nor have I seen any feedback on them... Based upon the pdf specs:
The 12" driver has only a 4mm excursion - Excursion limited and Insufficient to generate that sort of SPL before mecahnical damage or thermal failure, I'm guessing.
It's been my experience that a PA made from cheapest parts can not be made to sound good, and will not be very durable and robust.
There is a huge sonic difference in a PA made with cheap parts and one made with name brand drivers.
You pay a lot of money for a driver like a 2206 or a 2226, but after over 8 years and thousands of watts they still sound better than new OEM drivers.
I repair drivers and so I would rather repair a used/damaged ( cone tear etc ) JBL then buy a new OEM despite price.

my metod to have an approx of the max thoerical output,

http://img518.imageshack.us/img518/5639/tempig0.th.jpg


i use it to note the difference between different thorical project...
isn't correct but for approx the difference between project is good...

:)

andrew_87 2nd December 2008 07:50 PM

another simulation...

http://img57.imageshack.us/img57/9266/tempxr0.th.jpg

:)

140dB was refered to these simulations...

;)

:)


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