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DIY - 212 cabinet - help with ports calculation

KoziejMaclowski

KoziejMaclowski

Jun 8, 2019
44
12
#1
Hello. I have two faital 120pr300 8 ohm drivers. I'm going to make some custom cabinet 212. I need to help from you! I allready have some plans for construction. That will be my first custom cabinet.

I'm attaching some plans. (preffer nice look over mobility)
I have done some calculations in WinISD.

Volume 100l
Tuning freq: 55,05hz
Vents: 3 vents, diameter 11.00 cm vent length 20.1 cm
at System input power 300W air velocity 50hz: 16 m/s

Wonder also about:
110l
3 vents: 11.00 diameter 17,53 lengths

I'm doing it right?

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#2
Hard to say without plugging into winISD. Sounds roughly in the ballpark although I would have expected slightly longer ports, not that I have worked with high excursion 12''. If you can rig up ports with duct tape and cardboard temporarily you can fine tune them by experiment before glue.

How's your power handling with 55hz tuning?

Something else to consider is dual cabinets. It's nice to grab one little cab for rehearsals
 
#3
Downunderwonder said:
Hard to say without plugging into winISD. Sounds roughly in the ballpark although I would have expected slightly longer ports, not that I have worked with high excursion 12''. If you can rig up ports with duct tape and cardboard temporarily you can fine tune them by experiment before glue.

How's your power handling with 55hz tuning?

Something else to consider is dual cabinets. It's nice to grab one little cab for rehearsals
Click to expand...

Thanks. I will use eden wtx260 for now. I don't know what you mean by power handling at 55hz. But I can post some graphs from winISD tommorow. want to buy monacor telescope bass reflex ports so will be able for tuning them. Also these ports are screwed.

Screenshot_20190609_025741.jpg
 
#4
50L per driver or 1.76 / 1.8 cubic feet
Sounds about right. Probably offer little more power handling.

2.2 to 2.6 cubic feet per driver probably offer more bass response. Depends on the driver.
Or about 62 to 68 L per driver

Im looking for data sheet.

Most tend to high tune. I typically prefer tuning low as possible.

Can be as simple as tuning to Driver Fs.
And typically stick to larger BB3 or BB4 alignments.

Some will go with higher tunings to squeeze extra 60 or so watts. And fiddle around with non true alignments

I find it pointless and tend to tune low for better transients. Hence using BB3 or BB4
Alignments.

Which basically tune to driver Fs then adjust volume according to driver Vas.

Given better transients and lower bass.
F3 will be high in the model.

Real life with normal EQ = equals more bass

Haven't seen driver driver specs yet. I'll assume if Fs is high. The driver likes smaller volume has decent high-end and just tune at Fs or 2/3 hz below.

Just remember to get correct port length subract driver and bracing volume. And assume and subtract the rough generic port volume to get correct length. Likewise if your using single flare ports use correct end factor correction.

Like the bracing. Looks shallow try make deep as possible. And liking the width.
 
Last edited:
#5
KoziejMaclowski said:
Hello. I have two faital 120pr300 8 ohm drivers. I'm going to make some custom cabinet 212. I need to help from you! I allready have some plans for construction. That will be my first custom cabinet.

I'm attaching some plans. (preffer nice look over mobility)
I have done some calculations in WinISD.

Volume 100l
Tuning freq: 55,05hz
Vents: 3 vents, diameter 11.00 cm vent length 20.1 cm
at System input power 300W air velocity 50hz: 16 m/s

Wonder also about:
110l
3 vents: 11.00 diameter 17,53 lengths

I'm doing it right?

View attachment 3440116
View attachment 3440117
Click to expand...

You are on the way to design a pedigree Tschebyscheff alignment (4th order Tschebyscheff HPF).
IMO/IME that's not a good idea with bass cabinets
 
Last edited:
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#11
ThisBass said:
WinISD is a fudging freeware tool anyway.
Click to expand...
What does WinISD get wrong, that would be of concern to a DIY speaker builder? I compared graphs from WinISD to ones produced by my own derivations from basic electromechanics, and they were in good agreement. The laws of physics are the ultimate freeware. ;)
 
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#17
One suggestion - my experience is that the internal damping has a far greater effect on the sound than the port tuning. I strongly advise constructing the cabinet in such a way that you can readily change the amount of damping material in early testing and development, and only once you are satisfied gluing everything in place.

If your development access will be through the front baffle I would double the number of screws on it. I had access through the back and was staggered by how much more it moved than I had expected.
 
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#18
JimChjones said:
One suggestion - my experience is that the internal damping has a far greater effect on the sound than the port tuning. I strongly advise constructing the cabinet in such a way that you can readily change the amount of damping material in early testing and development, and only once you are satisfied gluing everything in place.
Click to expand...
Thanks! Yes I will glue only rear panel, at the front and keep front palnel on screws.
Also I will use Loctite glue for screws, its not pernament connection but helps securing bolts.

Also I guess I need to add volume, so it will match tuning after adding damping materials.
 
#20
KoziejMaclowski said:
At the other side I will glue M7 nut inside wood.
Click to expand...
Over here, we use T-nuts with threaded fasteners if we don't use plain old wood screws. Regardless, you need a fastener every 100-125mm or so.

And what's going on in the area behind the ports? It looks to me like the bracing is forming resonant cavities separate from the main chamber...kind of like a band-pass enclosure. Is that part of the intent of the design?
 

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