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[Greg_Cameron]

My biggest concern beyond amp, deployment, ROI, etc. is the rigging. I'm leery of a no-name budget Chinese system that will be hanging in the air. Who knows what the quality of the steel is and how well it's engineered. At least with any known brand, even lower end stuff, you can be fairly certain the rigging hardware is safe to fly over humans before a know brand puts their name on the product. This kind of thing scares the crap out of me.


Greg

[Scott Holtzman]

I swear I have seen Alcon in the gear summaries in LSI.

Know nothing about them.  So many good comments.

By the time you power them,you could get FBT or DB Tech boxes that have support,  a dealer channel and published performance data.



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[Chris Grimshaw]

I think the others have adequately covered the arguments for/against buying some line array boxes from China.

I had a quick look at the data that's been published, and it looks to me like the 12"s are rated for 450w continuous each, so the "LF" (actually more like midbass, but whatever) band would be 900w continuous rated. The cabinet is rated for 1000w continuous in total.

When it comes to power for your speakers, here's how it works:

You can destroy a speaker using an amplifier in two ways:

1 - Mechanically. If you put lots of bass through the speakers, especially below the port tuning frequency, the cones will flap around and parts of the speaker will smash intoother parts of the speaker. We're looking at the voice coil hitting the back plate, torn spiders or surrounds, folded cones, stuff like that. Dropping a mic without filtering in place will do that.
These days, so long as you put a highpass filter somewhere sensible and keep the cabinet design sensible, it's unlikely to be a problem.

2 - Thermally. Simply put, too much power for too long. Heat builds up and the adhesives holding everything together start to break down. Thermal failure can be fast, too - HF drivers can be made to act as a fuse if you use an amp with too much peak power.
Anyway, long-term thermal failure. This could get quite mathematical, but stay with me. The important bit is that +3dB = 2x power.

Speakers get their power ratings by using pink noise with a 6dB crest factor, and letting it blast for a couple of hours. Usually, the speaker is in free air (ie, lots of ventilation), and probably in a room with A/C.

Crest factor (or duty cycle - they're the same thing but expressed in different ways) is the thing that it all hinges around.

Square waves have 0dB crest factor, or 100% duty cycle. This should be obvious - the signal is always on, and always at full voltage (either positive or negative), and switches instantly between them.
Sine waves have a 3dB crest factor, or 50% duty cycle. Peak voltage is achieved twice per cycle, and the RMS voltage is at 0.707...x the peak voltage. Since power is proportional to the square of the voltage, 0.707...^2=0.5, so that's 50%.
The AES standard (AES-2 1984 Rev 2003, section 4.5.1) pink noise test signal has a 6dB crest factor. So, it spends a small fraction of it's time at peak voltage, and the RMS voltage is 0.5x peak. 25% duty cycle.


So, we take a speaker, apply that pink noise, and using a true-RMS voltage meter we find that it was receiving 28.3v RMS when very close to thermal failure. For convenience, it was an 8ohm driver and we're going to leave impedance variations to one side. 28.3v RMS into an 8ohm driver is 100w. Now, that driver was also receiving 400w peaks during that test. It's just that, due to the nature of the pink noise test signal, some time was spent below 100w, so it averages out. We've now got two different power ratings for the same driver - 100w RMS, 400w peak.


Okay, so we can use an amplifier that can put out 400w peaks, and get maximum output from the driver, right?

Well, yes and no.

Usually, that'll work fine. There are some caveats, though:

- If sine-wave-like content appears, you're now in serious danger of melting the driver, as it's receiving 2x it's rated thermal power. That could be mic feedback, a sustained note on a guitar, EDM bass drop, whatever. It's getting 200w of heating power from the 400w amp, and it's not going to last long.
- We don't use speakers in free-air. They're usually in an insulative box that doesn't have much air flow, so the driver is sitting in hot air and won't be able to get rid of heat as effectively. They should be de-rated accordingly, but by how much is anyone's guess.

The average power of the program material will vary greatly. I know of some dubstep where the bass line is a compressed 36Hz sine wave. It sits somewhere between a sine wave and a square wave for heating power, so if you took that 400w amp and 100w driver, the driver would be toast before you got near to clipping. Spoken word, however, is the opposite - with all the dynamic range, you could probably use an even bigger amplifier, clip it occasionally, and still not have to worry about thermal problems for the driver.

Most modern pop music has a peak-to-average ratio in the region of 10dB. That means you could, in theory, use a 1000w amplifier for that 100w driver. If you tickle the red lights, though, the driver is unlikely to survive. In that case, I'd argue it's a waste of a 1000w amplifier.

If we used that 400w amplifier, you'd be okay to go 3dB into clipping with modern pop music, and the driver would still be just about okay, and most people won't notice 3dB of clipping.


Yet another thing to consider is power compression. Do you really want to run your drivers at high power? When they get hot, they get quieter due to increased resistance of the voice coil. I used to use some 12" drivers with 3" voice coils and a 500w thermal rating. After running with a 1000w/ch amplifier for a rock 'n' roll gig, I found that they were around 6dB quieter than the rest of the system!


So, what's the conclusion?

As we keep saying around here, it depends.

If a system is going to be used by DJs with no clever limting, I'd recommend amplifiers with power equal to the RMS power of the speakers. It won't go as loud as the same cabinets with bigger amplifiers, but the system is likely to survive the night.
If you're going to set clever limiters and/or be careful with it, I see no problem with going to 4x RMS.
Most people split the difference, go to 2x RMS, and allow the amps to clip occasionally.

Remember that the difference between the two extremes is 6dB, which sounds roughly like "half as loud again". The 2x RMS system will be 3dB away from each, which is a "noticeable increase in level". It's worth playing around with something that can alter the level in dB to find out how big those differences are.

Phew, that's a long post. Time for lunch.

Chris

[David Sturzenbecher]

I swear I have seen Alcon in the gear summaries in LSI.

Alcon is a well respected loudspeaker manufacture. Aclon is not.

[Ray Aberle]

Alcon is a well respected loudspeaker manufacture. Aclon is not.

You mean.... they might be trying to gain business over someone's confusion and thinking that they're the reputable manufacturer when they're not??

Who would ever think of doing such a thing!

[Mike Pyle]

I swear I have seen Alcon in the gear summaries in LSI.

Scott, I have some new JRBL cabinets I want you to check out!

[Tim McCulloch]

Alex, it's time for the Anvil of Reality to drop.

I wouldn't buy this shit with your money, my money, or anyones money.

As was pointed out up thread, this product will not help you grow in any meaningful way.  While you may not work with artists that have clout to demand "real" PA (or have clients that will do so), you will be incredibly disappointed in the performance of this "system" and if it's as bad as I expect it to be, your clients and artists will be disappointed, too.

I've mixed on a very similar system that was touted to be JBL, and the only things in that rig found to be genuine were the Crown ITech HD 4x3500 amplifiers - the top boxes and subs were counterfeits that sound NOTHING like the JBL products they appear to copy.  The buyer (an installation done more for thrift than for reality) doesn't care, because the price was "right" but any act with a BE spends too much time trying to make the rig sound decent.  After mixing a couple of shows on this rig, I was brought in on a service call to find the stuff already blown up and recommend fixes (my suggestion involved kerosene and a cigarette lighter in the field behind the venue).  The 3 hours of trouble shooting and tuning work indicated to me that it would be necessary to roll my own processing and build the presets for the Itechs.  I am not necessarily competent to design line array processing and even if I were, the price I would have to charge to build manufacturer-level processing design would make the fee high enough that the venue should have purchased genuine JBL to start with.

So here's the deal, Alex.  You're going to spend money on this, money you will not recover once you find out how truly awful this crap is, and you will not be able to sell locally as everyone will know how shitty it sounds.  Putting money into this counterfeit - designing processing and dealing with bogus rigging - could be spent on real products that come with correct processing, manufacturer/distributor support and parts availability, and a network of other users from whom you can rent additional speakers when you need them.

Now, do you *really* need a "line array"?  From a sonic standpoint, probably not.  From a marketing perspective, possibly so.  If you need the word "line" in your speaker system description consider one of the column "line arrays" like the DBTechnologies Engenia IG4T (reviewed favorably by users here at PSW) or consider buying used name-brand equipment.

The 2 axioms that assist the purchase decision making:

1) The wrong product at the 'right price' is still the wrong product.
2) Buy once, cry once.

[Ray Aberle]

Scott, I have some new JRBL cabinets I want you to check out!

I think you meant Bortec Labs.

[Matt Greiner]

I think you meant Bortec Labs.

Well at least try are trying to hide what they're knocking off.....  lol.

[Scott Holtzman]

Yea,  I missed the spelling difference.

This is a 30k+ mistake I hope the OP heeds the excellent advice offered here.



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