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Old 28th May 2012, 10:41 PM   #1
kctess5 is offline kctess5  United States
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Default Cheap! party system

After going to see a Skrillex/Madeon/Wolfgang Gartner/A-Track (the list goes on) concert last night I feel the need for a system with some massive power handling capabilities and not incredibly hifi sound quality. Mostly, I want to be able to hit war volume in small outdoor venues like my own average sized suburban backyard.

I generally do full range systems as I listen incredibly near field and I like the coherence and sound quality they give for in room use, but they will not cut it for any sound reinforcement type application, so this is sort of foreign territory for me.

I was thinking using making two 2 way mains augmented by a horn loaded sub focused around high efficiency. I am thinking of going for a low crossover, around 300Hz between the mid woofer and the top woofer, to make the wave front more coherent over most of the range and then cross to the sub around 80Hz with a 30 Hz low cut. I already have an active crossover than can do the legwork for all of that.

My plan was to look for a beefy full range type driver with medium excursion capabilities for the upper range, and use a 10" PA driver for midbass, thus taking the excursion load off the full rangers and letting them hit very high volumes without going over excursion. The subwoofer design I can handle just fine, ive done it before.

Is using a full range type driver like this a okay idea?

Any overall suggestions?

I would love to keep total cost below $150 (not including crossover), I know this is a stretch, but as I said, I'm going lo-fi, if I want crystal clear articulation, I can go upstairs.
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Old 28th May 2012, 11:58 PM   #2
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'full range' drivers aren't typically built to handle high power, better to go for a cheap version of the 'econowave' - woofer in BR box + CD with horn
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Old 29th May 2012, 12:39 AM   #3
kctess5 is offline kctess5  United States
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I did some looking around and I found a few I though could go together

T3 Audio T200-12S4 12"
GRS 8FR-8 Full-Range 8"
Foster 025N03 Aluminum Horn Tweeter

Heres the idea:
Horn load the 12" sub to get some SPL out of it, its pretty high excursion (12.7mm) so it could do well assuming I didn't ask it to go too low, I'm thinking 50Hz taped horn.

Four of the GRS 8"s crossed in around 125Hz, they have 5mm of excursion and are very efficient. I calculate that 4 of them at 15watts each would hit 114.7 dB 1 meter, which is loud for a backyard.

Cross to the horn tweeters at 5KHz or so, I can change it easily so I can mess around with it. At 100 dB/meter/watt efficiency they will only need a few watts.

The sub will be a bit power hungry and I can deal with that, the mids I will probably need about 50 watts per channel, and the tweeters I can use a 10 wpc amp, the Lepai t amp should do the trick.

Total driver cost is $110, not too bad. I think I can get my hands 2 of the three amps, and I can just get one more Lepai t amp (I already have 2).

So with the drivers, amp, and MDF (no finish, keepin it quick and dirty) and a bit of stuffing I'd be looking at about $170, not too bad. And it could probably hit 115dB without too much trouble from 50Hz to 19kHz (the sub might not be able to but I need hornresp before I know for sure)

Look ok?
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Old 29th May 2012, 12:42 AM   #4
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Buy 16 of cheap 6" drives from partsexpress and build line arrays.
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Old 29th May 2012, 03:01 AM   #5
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by Wavebourn View Post
Buy 16 of cheap 6" drives from partsexpress and build line arrays.
Hi,

I tend to agree, 16 of these per side in a ~ 4ft high cabinet equalised
with a graphic EQ shouldn't be too shabby, around 102dB/W and the
1/x cylindrical wavefront will aid projection outside, 32 for $40.

3" x 5" Ribbed Paper Cone Shielded Woofer Speaker 299-286

Possibly double up your subwoofers to one each channel.

rgds, sreten.
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Old 29th May 2012, 03:49 AM   #6
kctess5 is offline kctess5  United States
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I like the line array suggestion, but I don't know about those little 3" by 5" things. I found a few options

12 of these:
6-1/2" Sealed Back Treated Paper Cone Midrange Speaker 289-126
6 per side. Thats $36. Max SPL 140 dB with ungodly amounts of power. More realistic output with 20 watts per side 120dB

2 of these:
Heavy Duty Titanium Super Tweeter TW44 270-125
Very efficient at 104 dB. 20 watts per channel gives 123 dB, I don't need line arrays for these things to get loud so I might as well save some cash

2 of these:
T3 Audio T200-12S4 12" 200 Watt Subwoofer 4 Ohm 269-086
Not very efficient. 100 watts per channel gives only 113.5 dB. That is of course without horn loading, with it they might be up near the others at 120 dB, but I don't know if I can design a horn that will go flat up to 800 Hz needed for the midrange crossover. There's not much I can do about that without spending a whole lot more though, and 113.5 dB is still pretty loud

What I am thinking to keep it small and portable is making only a bass cabinet, and just mounting the tweeter and midranges on a open baffle setup that folds up from the bass cabinet. Open baffle will be fine for both of those as there are no enclosure requirements with the sealed back midrange. That would also free me up to make a relatively large bass cab while keeping overall size manageable.

My current speakers are line arrays, although designed with hi-fi in mind rather than pure SPL, they are still quite dynamic so I am leaning towards line arrays for this also.
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Old 29th May 2012, 12:57 PM   #7
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Old 31st May 2012, 10:33 PM   #8
NiilaH is offline NiilaH  Finland
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The design Riley suggested might work pretty well for your needs. I have a feeling it's not going to put out a lot of low bass, but might offer you what you are after since it's capable of decent spls at least.

A slight word of warning when you talk about horn loading this t3 driver you mentioned. You just can't go and pick a driver from a shelf and expect it to work in a horn. Horn drivers need to have certain qualities if you are expecting to get a decent results as an out come from horn loading. Thiele-Small parameters tell you a lot about the driver and in what sort of use it might be intended.

For example for a horn driver we might want to look into a driver that has a high EBP value, which stands for efficiency bandwidth product. You can calculate an EBP of a given driver by dividing it's "fs" by it's "Qes". On this particular case with the T3 driver, we arrive at a EBP of 43.2 which is abysmal when considering the probabilities of it being a successful combination with a bass horn. EBP roughly estimates how well the cone of the driver is able to modulate the air column that form inside the horn. A general rule of thumb is to have a driver which EBP reaches over the 130 mark. Also drivers with less value than this have been known to work, but it's just a some kind of ballpark to aim your search. Mounting a low EBP driver to a demanding horn loading application will make it sound pretty gnarly. Slow, unarticulated and "one-noteish". Drivers that fit this criteria don't come in cheap because strong powerful motors yield high EBPs and these powerful motors cost a lot to manufacture.

Another thing that should be mentioned is that horn loading subjects the driver to a lot of pressure especially when we are dealing with long horns that are needed for reproduction of bass frequencies. This pressure caused by the viscosity of the air column has easily enough force to punch a hole through a cone that's not designed for horn load applications and I have my doubts that the t3 doesn't provide the much needed strength. Of course this phenomenon only applies when high sound pressures are to be extracted from the driver so the driver might be fine when driven with low levels. But Exceptionally bad combo in this sort of situation is a cone that's not designed to be horn loaded and high displacement of the cone because the more the driver moves, the more pressure it will create.

Good luck with your project!
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Old 31st May 2012, 11:52 PM   #9
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by kctess5 View Post
I like the line array suggestion, but I don't know about those little 3" by 5" things.

I found a few options 12 of these:
6-1/2" Sealed Back Treated Paper Cone Midrange Speaker 289-126
6 per side. Thats $36. Max SPL 140 dB with ungodly amounts of power.
More realistic output with 20 watts per side 120dB
Hi,

The sealed back 6.5" would be a disaster area given the bottom end is
specified as 800Hz. If your going for line arrays you want close spacing
which the " little 3"x5" " allow. Decent Xmax, lowish Qts, reasonable Fs.

16 per side will work with EQ. If your going for line arrays the last thing
you want is a separate tweeter with a very different dispersion pattern.

Around 1.5 to 2 cuft sealed and well stuffed for 16 of them, x/o around
150Hz to ideally a separate sub for each channel. They will need EQing.

rgds, sreten.

For lower impedance than 8 ohm you could go 20 (6.4 ohm 5ft+)
or 24 (5.3 ohm 6ft+) or 28 (4.6 ohm 7ft+) or 32 (4 ohm 8ft+).
The point is to exploit the cylindrical dispersion, and the taller
they are the lower in frequency the dispersion is maintained to.
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Last edited by sreten; 1st June 2012 at 12:19 AM.
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Old 1st June 2012, 01:46 AM   #10
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Cheap Party system. Dual 15's, 6.5 mid open back and a horn tweeter.

$400 including wood. Look around there are many choices for what you need. It helps if you have dealt with XO's in the past. Otherwise consider going active, it's easier
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