Tops to accommodate Xoc1's T18 - Page 2 - diyAudio
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Old 13th February 2012, 11:55 PM   #11
jbell is offline jbell  United States
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art:

aren't your "unity" ports a bit big?
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Old 14th February 2012, 10:29 AM   #12
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Originally Posted by Xoc1 View Post
As Art points out there is definitely a need to determine what SPL you want to acheive.
Not everyone will have the drivers, amplifiers, or plug sockets to be able to get these high levels!
i don't need a ton of SPL. most of the shows i play are small indoor, but through the summer i play several outdoor shows. i figure i will have head room with the T18s for most of my indoor shows.

if i went with the 4 -12" and 2 compression configuration, what are the rules for locating the 12" so they don't suffer from cancellation.

Art, i have messed around with a drawing similar to your cabinets, only with 12s.
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Old 14th February 2012, 11:52 AM   #13
SG3525 is offline SG3525  Slovenia
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I would suggest a normal BR design. I had the same problem finding the right tops for my LAB subs. I really like horn designs but it's hard to make them go low enough to meet with modern subs. So we decided to try a BR approach. From all the horn building we done I almost forgot how nice a god BR design can play

We decided on a 2x12" + 1,4" combo. Mid drivers are B&C 12NDL76 and high is 18sound ND1460A on a XT1464 horn.

The dip around 190Hz is from the height difference from the ground to the mic. Ground plane measurements show a flat response.
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Old 14th February 2012, 02:57 PM   #14
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Originally Posted by jbell View Post
art:

aren't your "unity" ports a bit big?
Not for 8" speakers.
Most of the designs you have seen are probably using 4-6" drivers, which have a smaller enclosed volume behind the ports.

The ports are fairly close to the ones used on the VTC line array (Danley licenses the Paraline and Synergy concepts to Yorkville, VTC is a subsidary of Yorkville) which my design is similar to.

I determined the port size through testing several different sizes, too small or too big both have problems, getting it "just right" took a while.
Modeling in Hornresp would have narrowed the port size selection process down quite a bit, but I (re) built those cabinets in 2008, and only got in to Hornresp last year.

At any rate, I have never been happier with a system than this one, the dispersion is completely uniform (-6 dB at 45 off axis) over 90 degrees down to Fc, and the line array/Paraline effect makes the front to back coverage very consistent.
In fact, a few engineers who recently mixed on the system were surprised to find that the mid/high level was actually slightly louder at the mix location (about 75 foot back in a 150' deep room) than it was at 10-20 feet from the speakers.

Art

Last edited by weltersys; 14th February 2012 at 03:18 PM.
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Old 14th February 2012, 03:16 PM   #15
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Originally Posted by scameron78 View Post
if i went with the 4 -12" and 2 compression configuration, what are the rules for locating the 12" so they don't suffer from cancellation.
If going front loaded, the "rule" would be a vertical alignment, HF horns on top, possibly with a mid rolloff on the lower 12" cones.

If using a Paraline/Synergy horn approach, the port exits should simply be placed as close to the horn apex as possible.

A 12" will acoustically fall off around 600 Hz with the Synergy style port loading, which is a (huge) stretch for most 1" exit drivers, you would probably need a 1 12" to 1 1" ratio to keep the HF driver excursion low enough to keep up.

The VTC EL210 uses 2 x10" and 2 x 1", the 10" only make 650 Hz before a rapid fall off, my 8" design only goes a bit higher.
The 3" diaphragm EV DH1AMT HF drivers I use load down to around 300 Hz, over an octave below the cutoff the VTC 1" has.

Art
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Old 14th February 2012, 05:06 PM   #16
tb46 is offline tb46  United States
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Hi Art,

Did you use a passive crossover on your unitys, or how did you solve that puzzle?

Regards,
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Old 14th February 2012, 06:51 PM   #17
jbell is offline jbell  United States
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Originally Posted by weltersys View Post
The 3" diaphragm EV DH1AMT HF drivers I use load down to around 300 Hz, over an octave below the cutoff the VTC 1" has.

Art
that explains it nicely... They didn't look small enough to get anywhere near about 800hz which was my guess....
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Old 14th February 2012, 11:24 PM   #18
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Hi Art,

Did you use a passive crossover on your unitys, or how did you solve that puzzle?

Regards,
Technically it is a Synergy horn, since it uses a Paraline device.

Passive crossovers are not very useful for PA work, the components for a dozen cabinets would cost a lot more than a DSP, and waste most of the power sent to the HF, reducing headroom.

Even though the ports create a steep acoustic crossover, there are out of band peaks that still need attenuation, frightfully hard to do with a passive crossover. I also use different amounts of cabinets on occasion,and sometimes with a large waveguide, different corrective EQ is required for each set up.

I am using DBX DriverackPa for DSP, it has just enough PEQ and delay to work.

Although I am quite pleased with the small format line array (and the individual cabinets weigh only 50 pounds apeice, so I can stack by myself) for most DJ type gigs, the even response a line array can provide is not a big selling point.

That said, I built a pair of 2x10" with a HF horn that each weigh around 80 pounds, I'd rather stack the 250 pounds of SFLA one at a time than lift those buggers to head level.

Art
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Old 14th February 2012, 11:49 PM   #19
NEO Dan is offline NEO Dan  United States
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Hey Art,
How close is the equivalent Hornresp model to you design? Any insight you can offer?
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Old 14th February 2012, 11:55 PM   #20
tb46 is offline tb46  United States
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Default Post #18

Hi Art,

Thanks for the explanation, I figured that you would be using an active solution.

Regards,
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