What’s the buzz with Line Array?

[toxcrusadr]

Just read this on a funny daily calendar:

Seen on Actual Resumes

• Bilingual in three languages
• Exposure to German for two years, but many words are inappropriate for business.

 

[bimasta]

I was taught French in elementary and high school but with little practical use over the years, my ability is limited.

Me too, and forgot 90% of it. But when I'm in France, it seems to come back. After 4–5 days, I'm having conversations! They think I'm a moron but we communicate. I even cursed a guy out, and he apologized.

 

[InfinityGold]

Oh I see Now. I had it all wrong I thought this was a Line Array .........Lol
Well anyway this is my Line Array of Infinity Speakers.

 

[wyn palmer]

You do get a boost in output with multiple drivers. Two woofers together, for example, gives you an extra 3 db on top of the doubled output from having two drivers, just as a bonus. It's kinda complicated but you get 6 db more acoustic output from only a 3 db (i.e. doubling) of input power. That is, assuming the drivers are in parallel. With line arrays you usually end up with series-parallel grouping so the output have to be calculated. I found a cool little spreadsheet that will calculate overall sensitivity and impedance of an array from the # drivers, driver impedance, driver sensitivity, and overall impedance of the array. It's posted to this thread for anyone who might be thinking about designing a LA.

http://www.htguide.com/forum/showthread.php?27677-Calculating-line-array-sensitivity

It's probably better to state the sensitivity issue in another way.
If you double the output voltage from a perfect, zero output impedance, amp, into a single subwoofer then the output sound level amplitude doubles (increases by 6dB, although the actual apparent loudness goes up by about 3dB) and the power out from the amp increases by 4x or also 6dB as the output power is calculated using V^2/Rload and you get 3dB for each doubling of power.
If you still have the single power amp, but you are now driving two sub woofers in parallel and the output of the subwoofers is coherent at the listening position (the outputs add so that at the listening position the amplitude is doubled) then the sound level doubles also but the power out from the amp increases by only 3dB due to the fact that the amplitude remains the same but the load R is halved, say from 8 ohms to 4 ohms. This does not apply if each sub woofer has its own amp.

 

[restorer-john]

I was in a fellow enthusiast home recently that had built these arrays. He currently did not have them hooked up but I very much would like to eventually hear them. The guy next to them is about 5’10” or so I’m guessing.

Back in the day, they were known as PA columns. He needs one more woofer at the top- it just looks wrong.

 

[toxcrusadr]

Back in the day, they were known as PA columns. He needs one more woofer at the top- it just looks wrong.

He's got 12 woofers there so another would make an odd number and mess up the impedance and wiring. 12 is hard enough, since it's not a 'square' (9 or 16 would be), the overall impedance is something other than the single driver impedance. I'm sure the designer took that into account. The mids appear to have 36, I didn't try to count the tweets.

 

[E-Stat]

I didn't try to count the tweets.

Sixty.

 

[Justgotohm]

Haha I did the same thing, counted all the drivers.

 

[restorer-john]

Haha I did the same thing, counted all the drivers.

Haha x2. I started counting and then thought I've got better things to do.

 

[StimpyWan]

I wonder why the IRS has such a wide baffle

The wider the baffle, the longer it takes the rear wave to wrap around to the front of the speaker. Once the rear wave combines with the front wave, they cancel out, since they're out of phase to one another. So, the wider the baffle, the less cancellation occurs, and the lower in frequency those drivers can play, with less worry of said cancellation. That wide baffle lets the Emims play low, and match better to the woofers.

 

[ultumax]

The wider the baffle, the longer it takes the rear wave to wrap around to the front of the speaker. Once the rear wave combines with the front wave, they cancel out, since they're out of phase to one another. So, the wider the baffle, the less cancellation occurs, and the lower in frequency those drivers can play, with less worry of said cancellation. That wide baffle lets the Emims play low, and match better to the woofers.

I. Never had line array speakers before but I remember a few years ago people raving about how good they were . How do they have so many drivers without independence being insanely high ohms or low ohms .
Parts express has a few kits not sure of sound quality or I’f they are hard to build.
Looks affordable tho https://www.parts-express.com/epique-cbt24k-line-array-speaker-kit-pair--301-984!!!
Anyone seen or built/ heard these .

 

[StimpyWan]

Most line arrays are wired with drivers grouped in smaller series/parallel groups. So, impedances can be balanced and controlled that way. Usually, the drivers at ear level are grouped together also. Then the higher drivers are together, and then the lower drivers too. This helps control dispersion as well.

 

[toxcrusadr]

Put two 8- ohm drivers in series for 16. Parallel two of these sets. 8 ohms total. Voila. You can do the same thing with 3x3, 4x4 etc. And there is no requirement that it has to be in squares. For example 3 sets of those pairs in parallel would be 5.3 ohms.

The grouping that StimpyWan is talking about can be done using different numbers of drivers in different configurations to get a different power consumption and output from the groups. So the center third of the line might be set up for 5.3 ohms and the upper and lower for 8 ohms, for more power output from the center of the array. AKA 'power tapering'.

The PE Dayton Epique linked above uses the convex curve for a sort of power tapering and a DSP for equalization, IIRC.