PA cabinet design

[worshipldr]

I am planning to build some PA speakers for our church. I would like to use some old Electro-Voice SP12C drivers I have on hand. I like these even though they are not really new. At this time they are in some cabinets I built in the 80's that are not optimal. (But they do sound fantastic when plugged into the output of my Boogie 50 caliber+!) I would like suggestions for compression drivers, horns, and crossover, but mainly for cabinet design. For example, square or trapezoidal, MDF or other, shelf bracing or not, volume, etc. The room is approximately 2000-2500 square feet with a 10' drop ceiling (although this may change in the future) and our amp is a Crown with 200w/chan into 8 ohms; not sure of the model #. Mainly vocal input but probably keyboard and acoustic guitar as well. We don't need rock concert SPLs, but we would like adequate cushion so the system won't be overdriven. Budget is a factor; for example, I was just going to paint them, but any suggestions on appearance would be appreciated as well. This will be my 3rd speaker project. Thanks for the input.

[Paul O]

Re: PA cabinet design

For a relatively easy cabinet look into the Econowave, and I believe there is somebody producing flatpack kits for these now too. Unfortunately I don't think the drivers you have are going to be adequate for the intended use, just not enough power handling to generate useful SPLs in a room that big unless you have dozens of them to build some column speakers.

[worshipldr]

Re: PA cabinet design

Thanks Paul. Yes, the EV drivers are a bit wimpy, rated at 35w I believe, but we have them on hand and will probably use them until either they give up the ghost or we have the budget to replace them with a higher quality 12". Future plans could also include powered subs. As far as the econowave, those are DIY enclosure kits, right? I did find EV enclosure plans on the net but they were really old and I don't know if the science has totally passed them up. I don't mind the routing and cutting involved in doing my own; but if the econowave will save time and effort I'd consider it. I will b probably be providing 75-90% of the work on this project.

[Paul O]

Re: PA cabinet design

Update: Here's a link to complete Econowave style kits.. http://www.diysoundgroup.com/wavegui...aker-kits.html

Here's a link to PE flat pack kit for a 12" 2-way PA cabinet.. http://www.parts-express.com/pe/show...number=245-325

Here's a link to everything about the econowave. http://www.audiokarma.org/forums/sho...d.php?t=150939

I wouldn't cost much to produce some very high output speakers with these components, I built my own trapazoid cabs last year and with about $300 in drivers and parts I was in business.

[worshipldr]

Re: PA cabinet design

Thanks, Paul, just what I wanted. Only one problem - on the PE link it said the flatpack product is no longer available. LOL The EV specs I have show a Vb of 5.5 cu. ft. - quite a bit bigger than the specs on that pack.

[Paul O]

Re: PA cabinet design

Yeah that's typical of classic drivers, they need a massive box to produce any bass at all and even then can't handle much power so they won't get that loud. In comparison a Delta12LF in a 2.5cuft box will take 250w and produce 120db all day long.

[worshipldr]

Re: PA cabinet design

I guess I'm going to go ahead and build a clone of the PE flatpack kit for the 15" drivers, using the 12"s I have and xover, comp drivers, and horns from PE. I plan on using 3/4" MDF and incorporating a shelf brace, and doubling the baffle. What is the best fill material these days? Been a long time since my last project. Any other suggestions from the community here? Cosmetic enhancement ideas? Before I pull the trigger and buy the materials?

[worshipldr]

Re: PA cabinet design

The MDF got upgraded to 3/4" birch plywood when I went to HD and saw they had gorgeous void-free birch for only $7 more than the MDF. The project has begun; will post pics when complete.

[AMC]

Re: PA cabinet design

The MDF got upgraded to 3/4" birch plywood when I went to HD and saw they had gorgeous void-free birch for only $7 more than the MDF. The project has begun; will post pics when complete.

You'll never regret a material upgrade, and your lungs will thank you also.

[worshipldr]

Re: PA cabinet design

LOL yeah they are already thanking me after the session with the table saw. Made a big pile of sawdust and made some cuts w/o the dust mask in place. Sneeze, sneeze. Also discovered that the plywood was not entirely void-free, but still very good. Very nice surfaces.

[wg_ski]

Re: PA cabinet design

The inners matter more than the outers. The stuff that's not void free often has poor adhesion between plys. Watch out that those "nice surfaces" don't de-laminate on you.

[billfitzmaurice]

Re: PA cabinet design

The inners matter more than the outers. The stuff that's not void free often has poor adhesion between plys. Watch out that those "nice surfaces" don't de-laminate on you.

+1. Not trying to be a downer, but I've never seen real Baltic Birch at HD or Lowes, only a cheap Chinese imitation with thin outer veneers and inferior glues.

[worshipldr]

Re: PA cabinet design

Ouch. Bummer. It just said birch and, yes, I noticed the veneer is very thin. It has so far survived all the cutting w/o coming apart.

[kblackmore]

Re: PA cabinet design

Ouch!! $$Expensive$$ lesson learned

[wg_ski]

Re: PA cabinet design

Take a picture of the end grain, and we'll tell you whether you should be a little worried.. or a lot. I've seen everything from China-made that's every bit as good as Baltic, to domestically-grown that's "ok" to the Chinese stuff that's only good for buidling temporary construction dumpsters. For most of my builds I've switched to Araucoply, which is a good grade of spruce/pine. It's the same price as Monte Carlo Birch and it's the same thing every time.