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Old 10th October 2013, 07:46 PM   #1
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Default Help design 3 way PA set

in my neighborhood nowdays its every weekend live disco.
witch i don't mind at all, the youngsters seem quite good behaving.
by that i mean they did invite me over, not mutch drinking, live dj music in oldschool 1990-95 music style.
nothing wrong so far...

but the speakers they use are horrid.
i never was thinking i gona get that old and grumpy to get fed up with this.
realy.. i mean i never ever even noticed how bad are these new age palstic PA ghetto blaster things are.
Don't want to ruin the kids party, and they are quite close to my house, so any decent party SPL is clearly audible in my house. I do not mind that, but the absolute horrid and distorted sound drives me nuts.

argh.. anyways.. i visited this party a few times. i can confirm the whole thing is dostorting as hell. so i came up with a tipical grumpy old man style of solution.
I gona build a set of speakers for these youngsters so we can both have fun.


do forgive me the long intro. i just had to share it, as both the horrid sound drives me nuts, and the solution i came up with.

so back on topic...
The place is a tipical yard, speakers radiate into quarter space.
surprisingly there are quite a lot of people there, roughly between 50-60.

I think one or 2 pair of 3 way speakers should do the trick.
since they are NOOOOOOOOOBS (yess, loud cry out) I have to make the amps too.
I decided that 1x LM3886 is what i can afford.

I'm looking for advice, as i never done anything for PA.
Priority would be high efficiency (low amp power..), box size can be max. 300 liters or so. Horns are out of question, ported or closed box for the bass is what i would like.

First problem i have is that.. i have no experience in this field.
I need tips on driver combinations that match, along with crossover recomendations.
I seen some PA speakers using sometimes only a fiol cap as crossover, unlike the ones i made based on Rod Elliott's excellent guideline on passive 2 way crossovers.
This is a 3 way build, so it would be a tad bit different.
I can make extra amplifier for the bass part of the cabinet, reducing the mid and tweeter to a 2 way system. Noting special.
I did allso read compression drivers work best for PA, but i have no experience with them, nor with the horns they need.
So the next question is if regular DOME tweetrs can be used, jutch like the Vifa Dx25 ?

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Old 10th October 2013, 08:08 PM   #2
sreten is offline sreten  United Kingdom
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Hi,

FWIW whatever you build they will turn it up until it sounds so
hideous they have turn it down, your sensibilities won't help.

I like Rod Elliott's site but TBH he really doesn't know speakers,
beyond understanding it from a very electrical viewpoint well.

A 2way Econowave (search) in a scoop (search) should work.

rgds, sreten.

Don't build a chip amp. Buy a powerful cheap amp, new or used.
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Last edited by sreten; 10th October 2013 at 08:11 PM.
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Old 11th October 2013, 04:08 PM   #3
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Plastic PA cabs can be very, very good if you take them apart, properly damp and brace them internally, and seal them up. The drivers and crossover may be marginal, but they don't stand a chance if the cabinet falls apart above 90 db, so fix that first if they'll let you.

Plastic speaker cabinets - improving internal bracing & damping

If you build them decent PA sub or two, the bass sent to the mains can be reduced, also reducing their distortion.
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Old 11th October 2013, 09:30 PM   #4
wg_ski is offline wg_ski  United States
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Subs - exactly. They're probably giving their cabs 20dB of bass boost below tuning and clipping the tar out of them. A couple of SS15's, a Behringer amp and a crossover will fix that.
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Old 11th October 2013, 11:04 PM   #5
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I'd be wary of building proper subs - the VLF goes through walls and things as if they weren't there, which is more likely to get complaints.

I'd get a 15"er per side and put a nice big bump in the 60-80Hz range. Make it hit them in the chest and they're likely to be happy.
What are they using currently?
It might be that you can re-use their kit in some proper cabinets with a dedicated bass bin and improve things considerably.

Chris

PS - get compressor/limiters. Set them once and then super-glue the controls.

Last edited by chris661; 11th October 2013 at 11:09 PM.
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Old 12th October 2013, 03:56 PM   #6
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actualy the big bump at around 60-80 hz is the thing that gets on my nerves.
currently they play on some el-cheapo no name mixer, 2 cd players, a quite old looking and absolute unknown amp and a pair of Reflex mega baby speaker thingy.
The only option for bass controll is on the mixer, it only pushes 60-80 hz up. not realy sounding good. Yesterday i did try those "speakers" with a more proper amp, they sound like a 3 way system without a bass driver. useless. utterly useless....
not to mention the sharp edge sound of the tweeters.
My first assumption was to create a bass bin for them, but i had to realise it would simply not make thngs any better at all. That is why i'm upto make a set from zero. The chipamps will make sure they can not overdrive the thing, I simply plan to "integrate" a fixed resistor voltage divider on the input of the chipamps. So they can not be overdriven, and will allso limit the max. volume.




BTW, ss15 does not get me anywhere on google.

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Old 12th October 2013, 07:31 PM   #7
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Single sheet TH challenge
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Old 13th October 2013, 12:21 PM   #8
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Quote:
Originally Posted by Arty View Post
actualy the big bump at around 60-80 hz is the thing that gets on my nerves.
High output at 30-40Hz will be much worse, as it'll happily go through walls and things. If there's anyone else living nearby, they'll have something to say about it.

Quote:
currently they play on some el-cheapo no name mixer, 2 cd players, a quite old looking and absolute unknown amp and a pair of Reflex mega baby speaker thingy.
The only option for bass controll is on the mixer, it only pushes 60-80 hz up. not realy sounding good. Yesterday i did try those "speakers" with a more proper amp, they sound like a 3 way system without a bass driver. useless. utterly useless....
not to mention the sharp edge sound of the tweeters.
My first assumption was to create a bass bin for them, but i had to realise it would simply not make thngs any better at all. That is why i'm upto make a set from zero. The chipamps will make sure they can not overdrive the thing, I simply plan to "integrate" a fixed resistor voltage divider on the input of the chipamps. So they can not be overdriven, and will allso limit the max. volume.
It sounds like the speakers need repairing. Do you have any pictures of them?

The "bass" controls on most mixers are shelving. It just sounds like the speakers don't have any <60Hz output. You can test this by playing a 30Hz tone and then turning the bass control. Chances are you'll hear 60, 90 and 120Hz getting louder and quieter.

Chris
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Old 15th October 2013, 07:09 PM   #9
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partially solved...
managed to get my hands on an older W bin, 10" driver only but at least it sounds ehh.. lot better, but still far from perfect.

The tweeters had been replaced, rolled the bass off from the pair of baby boxes with a series cap on amplifier input.
thank You for the opinions and help, very mutch appretiated.

actualy i did find this excersize quite good, never considered W bins before.
i will open a new topic for W bins.
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