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Old 10th November 2005, 10:09 PM   #1
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Default PA speaker cab cinfig question

hello everyone. im new to this forum. anyways the question at hand .
pretty soon were having custom cabs being built for a PA system were putting together. were nto sure of the power amp were using yet. but what we do plan on is having the PA cabs include one 15 inch speaker,
a 1o inch , and a horn. what should we know before doing this . compatability, ohms, whatnot. overall making sure it works with out power amp. and if this is a wise speaker setup. and the pa is for vocals and keys btw. thanks
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Old 10th November 2005, 11:06 PM   #2
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Default Re: PA speaker cab cinfig question

Quote:
Originally posted by godfearingjerk we do plan on is having the PA cabs include one 15 inch speaker, a 1o inch , and a horn
Not a bad combination, what drivers do you have in mind?

Quote:
[i]what should we know before doing this. [/B]
Unless you or your cohorts have done it before, I wouldn't even consider it until you have read up on how to build speakers. It's not a matter of slapping them together, there is much to be learned unless the results don't matter.

Quote:
[i] making sure it works with out power amp.[/B]
Do you mean you want things to work out with the power amp or you want this to be a self powered unit? ie: no external amplifier required.

Quote:
[i] and if this is a wise speaker setup.[/B]
That depends on the drivers chosen, tha cabinets you are having built, the crossover network and your ability to tweak the sytem as you go along.

Quote:
[i]the pa is for vocals and keys btw. thanks [/B]
You have a 15", thems usually for da bass. How did you come up with the 15, 10 and horn combo?

Cal
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Old 11th November 2005, 05:42 AM   #3
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Most PA cabs are 8 ohms impedance. This is a reasonable figure for use in combinations or alone.

But why build custom cabs, why not get something already made. The design is already done. And on teh used market, you can get a lot of speaker for not much money. If you want to build speakers because you are interested in it yourself or from a hobby syandpoint fine. But if your main interest is in having reliable portable sound gear to support your performance, it seems to me that your efforts would be better elsewhere.

Cabs not only must have internal dimesions worked out to fit the drivers, but we also need them top withstand the rigors of travel. Your crossovers must be up to the task. Your jack plate needs to have proper connections and be sturdy. Got handles? Corners? if you have any intention of flying this cab, stop right now and consult a professional builder. The last thing you want is for the top to come off a cab and the rest of it fall on the congregation below.

How big is the venue it is to be used in? You need long throw horns or short throw horns? What crossover points have you selected for those drivers? How did you select the particular drivers in the first place? Is the eficiency rating of each driver compatible with the other?

How many folks in the audience? We trying to get to 100 listeners or an audience of 1500? This speaks to the power needed and the speaker to project that power.

Power amp and speaker both are determined by their use. SO without knowing that, it is difficult to make any decisions about them. it is kinda like asking me, "I'm getting a new car, what size tires are best?" Beats me, what kind of car?
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Old 12th November 2005, 07:56 PM   #4
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first off. thanks for the reply .reason being is that the cabs are being made free and wired free professionally . all we have to do is supply speakers so yeah that would be a hell of a lot cheaper than buying one. thats why . its only for small gigging. like bars or soemthing of the sort and practicing . basically weve got some old pa speakers with 10s and horns already in em. figured wed salvage it and buy some 15s, give em to the guy have him wire it and whatnot. then purchase a power amp and hook it up and hope nothing blows and it works. thats just my question. im no pro when it comes to this stuff. i just would like to save a little money is all as we are very tight on it. we already have to buy a lot of crap and have already purchased a lof of crap.
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Old 12th November 2005, 09:05 PM   #5
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Have a look at http://www.colomar.com/Shavano/construction.html which give lots of VERY useful information.

Vocal PA only isn't a problem (at least as far as blowing speakers is concerned), but keyboards have a massive frequency range, and can produce high power at a single frequency - and this can kill drivers. So bear this in mind when you decide on your power ratings!.

I built a pair of 1x12's with two piezo horns, which I was very pleased with (although I've only gigged them once). I've since bought a pair of cheap 1x15's with three piezo horns - ready built in cabinets they cost less than the parts for my 1x12's did!.

The 1x15's sound fine, although they are less efficient than the 1x12's, but the lower bass of the 1x15's, and higher power handling makes then preferable. However, while they sound fine, you can really see the cheapness in the cabinets - my 1x12's are nice and strong, the cheap 1x15's are rather weak - OK acoustically, but they wouldn't stand much throwing around.

However, as I run the PA I take good care of them!, and handle them gently

BTW, I run my daughters three piece rock band through them, two vocal mikes, bass and guitar (both DI'd), keyboard, and the drums miked up with four mikes.

If someone is building you cabinets, presumably they will be strong as well? - it is a valuble asset in PA speakers, but does cost money.
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