Deep Dive into Funktion One IB218

I'm going to be embarking on a build soon and I'm curious about this cabinet and if anyone here has experience in the design. The plan is to replicate 4 similar cabinets and potentially build 2 Infra Horns to supplement them.

As far as I've searched, I could only find one set of vague plans and I have no idea as to its accuracy. I was able to extrapolate approximate volumes from the plans and it looks like the tuning is fairly high considering reported response. (65Hz according WinISD). Bandwidth isn't too wide either. Am I missing something here?

Vt Rear chambers = 225.4 L
Vt Front chamber = 216 L
Port area = 1030 cm^2
Port Length = 7.62 cm

These will be my first 4th order cabinets and I'd love to get some input from those with more experience. Do these plans and model seem accurate for those boxes?

Cheers!

Edit: all drivers modeled @ 2000 watts
 

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Side comment: As I'm sure there may be others with this opinion - I suggested to my partner we strike the 4th order plans and built dual 21" BR cabs using those monstrous BMS drivers. (136 dB @ 30 Hz) @[email protected]

Alas, my partner is quite adamant about a 4th order design with bolt on horns. He's also paying for the drivers so I'll grant his some leverage in the design. :D
 
You can't sim that accurately in WinISD.

To get a more accurate sim you would need to calculate the cross sectional area at the closed end of the front chamber, at the midpoint of the drivers, at the beginning of the port and at the end of the port. You would also need the length of each of those segments.

If you could provide all those specifics as well as driver t/s I could run a quick sim in Hornresp. Not sure how much difference it will make but it will be an accurate sim.
 
Thanks Just a Guy,

I'm at work currently and I have updated plans on my PC at home. Unibox gave similar results. I didn't even think to try Horn Resp. I'm still new to it. I'll post the updated plans when I can.

So far 18XL1600 is the driver of choice but I feel there is a better suited driver out there (one for a sealed alignment should work with 4th order I presume). In that case from what I've read: High Qts, High Vas, Low Fs should do well.
 
Out of curiosity, what's your (or your partner's?) reason for trying to replicate the F1 218? Not that I think there's anything wrong necessarily with that.

But if the primary reason is because F1 has a reputation for great sounding speakers, I wouldn't bother. Most of the magic is in the axehead cone mid-highs. Their bass bins, AFAIK, are quality but fairly run-of-the-mill design wise. You might save yourself some trouble going with a proven, well-documented design.

Unfortunately I don't have much to add as far as your questions go. You might have better luck and more accurate results modelling it as an offset driver horn in hornresp.
 

SUBduction

Member
2014-10-11 3:13 pm
Out of curiosity, what's your (or your partner's?) reason for trying to replicate the F1 218?

HAHA ahhh.. I think they're hung up on the name's prestige ;). I've never personally heard the IB218's I keep pushing dual 21s in a BR alignment for some seriously low extension. Alternatively, I've already built 2 Cubo Subs with 18XL1600s and I'm REALLY happy with the results. Adding another 6 bins would be killer imo. I've already learned my lesson by mixing different horns.

Like I said, they are really down to contribute by purchasing drivers and hardware, which I'm totally OK with! They need a bit more education on F1... meaning I need more education on F1.
 
Here is what I came up with. Please excuse the crudeness of MS Paint.

I'd do away with the hatches and just mount the drivers from the front. There should be enough space in the "horn" to pass them through and fit them in. Screwing them might be difficult, but not impossible. Making the center brace for the horn removable would make it a lot easier.
 

just a guy

Member
2006-05-12 6:59 pm
Normally I'd assume I did something wrong because this looks so bad - but it looks exactly like what you got so in this case I'll assume it's right. Shown at 6000 watts it only uses 10 mm excursion and f3 is way high. This has to be one of the worst designs I've ever seen.

[IMGDEAD]http://s32.postimg.org/733srmn11/image.png[/IMGDEAD]
 
Thanks just a guy. I kept scratching my head on this. Looks like this a true one-note-wonder. So many pitfalls in the data. I can only conclude that this design from the web is complete bunk or maybe these need to be used in multiples with the infra horn to help system response. Unibox threw up a red flag for exceeding Xmax and port air velocity.

This is actually what I was looking for - more justification for another design. I have a hard time believing this is F1's actual design.
 
As shown (at 6000 watts) excursion definitely was not a problem and port velocity was around 36 m/s.

6000 watts is probably a lot more than the drivers can handle so port velocity at much lower power levels is probably ok.

But the design is still junk unless I did something very wrong. Check my inputs.
 
All things considered, it's enough to dissuade me. These would be used outside in the mountains running off of a gas generator. I wish I was playing a 3 phase, multiquip game but right now we're running two 8kw gennies. That may change soon but for the time being looks like cubo sub is looking much better at this moment.
 

mag

Member
2008-01-23 9:22 pm
Chiasso
Not exactly the same data but very similar results...
I have used PD1850 as driver.
Things are different if the "infra-horn" is attached (See S4,S5,L45 on data).
But the size of this stuff becomes impossible...
Anyway I suspect there is something wrong in the plan...
Are you sure that is 4th order?
There are no vents between the 2 chambers?
 

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mag

Member
2008-01-23 9:22 pm
Chiasso
I don' believe it is fixed only by processing... Funktion One can do much better than this....
Modern 18inch pro drivers are all similar, probably they use custom drivers with T/S parameters completely different with respect standard RCF, PD, 18sound and the like...
Probably there is BS on the specs, but I have heard them with infrahorn attached and they are quite impressive on the low end
 
Another question from curiosity- how was the layout in OP's post arrived at? Is that known to be approximately what the internals look like, or a wild guess? Can't help but thinking there's a fold or two missing. There's lots of ways to get approximately the same specs as the IB218 with these drivers and this much cabinet volume, but this layout seems completely wrong from looking at the sims.
 
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Another question from curiosity- how was the layout in OP's post arrived at?

Excellent question. I believe this is another "I read it on the Internet" problem. This design is all I could find after searching around. Like I mentioned, the most likely cause for these poor sims is these plans have zero validity as to their accuracy. They only thing we really know are outer dimensions. Someone could have easily filled in the gaps as to what's going on inside and then posted it.

I've been in and out of service lately. We're doing a bit of off-road location scouting but I'll find the time to put together a much better set of 4th order plans just for giggles. I feel like that 7 cm port is that boxes Achilles heal, bringing Fb up too high. This obvious solution is to make the port longer at the cost of box size. Seeing at these are already fairly big boxes, that is a huge detractor having to make the box bigger. Someone somewhere did mention something about having to break a few eggs to make an omelet though.
 
I don' believe it is fixed only by processing... Funktion One can do much better than this....
Modern 18inch pro drivers are all similar, probably they use custom drivers with T/S parameters completely different with respect standard RCF, PD, 18sound and the like...
Probably there is BS on the specs, but I have heard them with infrahorn attached and they are quite impressive on the low end

I know from a guy who distribute Function One that those drivers are custom build by different suppliers to the specs that Function One asks. They are not regular drivers, but custom OEM builds.

And that infrabass only works well with the extra horn section. Without you better use the F221

SoundServies%20Infra.jpg