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HalAir Aeralis - Fullrange Line Array (Vifa TC9-18-08)
HalAir Aeralis - Fullrange Line Array (Vifa TC9-18-08)
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Old 16th August 2019, 05:32 PM   #21
Halair is offline Halair  Norway
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Todays efforts, baking time!

1660g EG, 125degF for several hours
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Old 17th August 2019, 11:17 AM   #22
Halair is offline Halair  Norway
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No pictures yet but the test cabinet i complete and playing

To-do list:
  • Make the diffuser
  • Create plugs/circuit for impedance testing, using REW
  • Get creative with the stuffing...

I took the test cabinet over to my old LAīs and performed an informal knuckle test to them, there is no comparison
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Old 18th August 2019, 07:05 AM   #23
Halair is offline Halair  Norway
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Okay, test rig completed and seem to be operational - this is no quality test performed just a quick scan to get baselines and data to learn from.
The cabinet is not fully sealed, neither at the driver side or rear wall.

Time to read up on how to "read" impedance plots, I mean they read resistance but how it all connects
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Old 18th August 2019, 07:50 AM   #24
mondogenerator is offline mondogenerator  England
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The Magenta trace, open back, is showing extra peaks at harmonics of the fundamental resonance.

That is how I interpret the plot. The two sealed plots dont show this cavity resonance. Stuffing the open back version to varying degrees may help damp this resonance out.

That would be a good test...

How much damping to eliminate those peaks?

Seeing as there are two magenta traces, its confusing to look at.

The Fb has dropped from Fs due to air mass loading the rear of the cone, but the column of air is resonant. Damping rear should help damp that out

Epic build by the looks of it - I've considered sand resin before and never had the nerve to try it!
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Last edited by mondogenerator; 18th August 2019 at 07:56 AM.
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Old 18th August 2019, 08:41 AM   #25
Halair is offline Halair  Norway
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Thanks for the comments Mondo I have never done this kind of testing and appreciate all input!

Okay, the driver have been sealed properly and same is the rear (removable) back wall.
I briefly tested with diffuser with/without other stuffing (interior lined with felt on all)

This should be considered the first "valid" set of sample data.

HalAir Aeralis - Fullrange Line Array (Vifa TC9-18-08)-impedance_diff2-jpg
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Last edited by Halair; 18th August 2019 at 09:01 AM.
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Old 19th August 2019, 05:54 PM   #26
wesayso is offline wesayso  Netherlands
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To really know/learn what's going on, don't be afraid to zoom in on the plots.
You're looking to get the least amount of wiggles from the peak value and above.

Open air looks nice and clean, now zoom in on the 150-2 Khz to see from 6 to ~16 Ohm.
The better damping will show the least amount of wiggles. That's what we're after.Every wiggle could possibly lead to a FR anomalie (dip/peak). Use the Vifa open air as the reference. The Max stuffing seems to look good, what stuffing? I'd expect a max stuffing to shift the peak to the left (lower in HZ) a bit. The itchy fiberglass does that quite well. While a layer of felt generally lowers the wiggles by quite a bit. That combination worked best for me. While on this scale everything looks fine, don't be afraid to zoom in a little closer. Like I said, felt on walls and itchy fiberglass (loose but kind of filled) in the open middle works wonders. Keep the back side of the driver free. I have a layer of felt there between back of driver and the fiberglass fill. About ~ 1.5 to 2 cm free air between back of driver and that felt layer.
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Old 19th August 2019, 06:55 PM   #27
Halair is offline Halair  Norway
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Thank you Ronald, I will visit this aspect of the build several times before they are completed
Tested a little back and forth today and the diffusor dont seem to smooth out for me, it causes the peaks to be a little "loopsided". In terms of peak symmetry and lack of wiggles it seems to be a KISS=better scenario.
Interiour fully covered with felt and various degree of "itchy stuff" placed inside seemed to be the cleanest. As each driver will be a closed chamber I can later test each driver individually, so if I decide to go all-in I might opt to tune each one individually so they all are as close as possible. Its gonne be a FUN fall/winter

A couple of pictures from today test run forming the casting tubes:

The last one is especially enticing, resembelling a "top fuelled" compressor intake Canīt wait to stack 24 pieces of these up...

Last edited by Halair; 19th August 2019 at 07:00 PM.
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