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torclausen 2nd July 2012 07:08 AM

Help designing outdoor PA.

A group of friends are building a sound cart, we call it the booty bump. And we are trying to use the best science possible in its design, which is why I am writing. The design is mostly set, so I will tell you what I know.

Sure 4x100 class d amp (the new one) running on 36 volts SLA batteries.

A pyramid two way electronic crossover with bass boost (cr78)

mids and highs likely will be two kicker 6x9's (they are unusually efficient)

A space in the cart that is 6 cubic feet for the lows, powered by the remaining two channels of the sure amp....

And that is what I want help with: What is the loudest, best sounding, lightest thing I can do with that space, for less than $200.

1) My initial idea is to avoid deep bass, because its just too power hungry, and all I have is 100 watts x 2.

2) The cart has two speaker sides, so I would like to have two woofers facing port and starboard. (I think it should play up into midbass (I think that will make more volume on the whole, yes?), and thus becoming directional)

3) The cart will be made of plywood. There is room on the face for a 12" or smaller.

4) Extra credit for a speaker choice that allow for us to upgrade to a larger amp in the future.

5) I like the idea of a ported enclosure, with it being tuned for maximum volume from say, 40 hz and up. (unless you think we can be both loud and low)

Money is tight, so if there are two (or more) less expensive, efficient speakers, we are all ears.

Thanks for hearing this out!

Warmly Tor

PS, if you think the kicker 6x9's are a bad idea (they are loud and clear) -please feel free to propose another idea. They cost $55 a pair.

mr. doom 3rd July 2012 01:39 AM

A pair of neo 12"s would work in 6 cubes, can you use another side of the cart for a speaker?. The peavey neo 12" is cheap and light. That would give much more bump than any 6X9 and take more power down the road... Not a true subwoofer but it is hard to do a light/loud/cheap mobile sub, and the 30 watts the sure will output to a 8ohm driver won't hurt it. I have used the peavey 10" neos and was impressed with the output to weight ratio, four of those and four big horns would pull good db's from a small amp.

torclausen 3rd July 2012 06:05 AM

That sounds good. I wished I could run that amp harder with four ohms. Not many PA's out there at 4 ohms though. Those do look like nice speakers. I like the idea of them in series... (the 10's).

Do you have advise on the horns? I am completely uninformed about tweeters. I am concerned that my obsession with efficiency will compromise the sound quality too much. Have you heard some good horns that will pick up where there 10" peavey's leave off?

Thanks again ~ good advise.

mr. doom 3rd July 2012 03:52 PM

The Peavey's are fairly smooth and can run up over 3k so just about any any tweeter will "work". I am trying some MCM specials that run $22 and have a large cheap plastic horn attached, my pair both were slightly chipped in shipping but they sound fine for the price and can crossover low if you need to.

A piezo array can be made cheap as dirt and will get the job done also.

tomi 4th July 2012 09:37 PM

Would anyone suggest a bandpass design for bass if we're going for efficiency over fidelity and depth - or are these too hard to design well?

mdocod 8th July 2012 03:50 AM

Hello Tor,

1. You don't need to avoid bass, you have plenty of amplification, you just need some reasonably efficient and cost effective way to utilise the available box space.

2. I think that you should keep an open mind about where to do your crossover. I'd suggest letting your tops extend down to where they are comfortable.

3. Plywood, check :) I'm surprised to hear there's only room for a 12" per side on a 6ft^3 cab... is that with the 6x9's in place? What are the dimensions of this "box?"

4. A driver choice that is optimised for a future potential amplification upgrade is could wind up being less than optimal under the current amplification. I recommend sticking to the amplification available, and NOT planning on more in the future. More amplification just creates more power storage challenges. Try to focus on getting the most out of the amplification you have.

5. The type of enclosure (ported, sealed, line, horn, etc) will depend on what balance of driver gain vs box gain is best for the drivers chosen.

I can't really tell what specifically the $200 budget needs to "cover." so I can't really begin to make suggestions. I will say that I would not use the car speakers personally, however, the alternative would be a more complicated road. I am willing to advise on that but would need a lot of details about the box and what height it will be elevated to, etc etc.


torclausen 26th July 2012 07:20 PM

So here is what I need help on.

As I said above, I have kicker 6x9's in little prefab boxes. They seems to crap out at around 120 Hz and below.

I have a box(or the space for a box), that is over 3.5 cubic feet. It is square-ish and the two opposing sides make up the lower face of our mobile cart.

I just attempted to build a subwoofer with a DVC infinity 12" sub, in a sealed box, downfiring. Some people have now advised that that was a bad idea, as that driver isn't at its best (far from it) in that enclosure. A bandpass could be made for the infinity sub, but I'm told it could be done optimising 40-80 Hz, leaving 80-120 underserved.

Could anyone advise another thing to do with this space, making the most outdoor PA type loudness. Perhaps two ten inch 4 ohm PA woofers each facing out on each side... playing loud at 35-120? The amp wants 4 ohms. Or four total 8 ohm 8" PA woofers?

We spend $60 on the DVC infinity Sub, we plan to return it.

Has anyone seen some good drivers that could work in this range on clearance?


torclausen 26th July 2012 07:22 PM

PS the budget is flexible, the amps (2050 sure amps) are all purchased. Its just this woofer box I need help building.

mr. doom 26th July 2012 07:45 PM

These 10"dvc drivers are surprisingly efficient.

I have used them with a 15watt t-amp and they pulled a decent amount of bump from limited power.

Grymer 1st September 2017 08:30 AM

Designing a speaker for street-performance
Hi forum

When designing a normal PA, how do I determine a good cab volume and what port size would be best for specific drivers? This is for a cheap project and I think I'm going for the cheap speakers along with a couple of ASD1001 horn-drivers that I already have. Either 10 or 12 inches.

This project is for a street-performance speaker, so this is the design I have been thinking about. (Terrible drawing in paint) It is built on a trolley, so it's easy to move around. I have everything I need to do the amp, batteries, eq, mixerboard and so on. The speaker will mostly be used for keys, guitar and mic. (Pretty much acoustic)

I have two small 2x100w boards along with a MiniDSP to eq and crossover. The idea is to have as good a spray-angle as possible, since the speaker will most likely be used on "narrow" streets.

Besides that. Any ideas on how sound quality can be improved? I think I'm gonna put some thin acoustic foam on the opposite side of both speaker-sides :)

If you have any suggestions to the design, please tell me.

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