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-   -   Christmas Build (https://www.hometheatershack.com/forums/ib-infinite-baffle-subwoofer-build-projects/63366-christmas-build.html)

blitzer 11-20-12 10:01 PM

Christmas Build

Santa is bringing the bass!

Ok, I am in planning and purchasing mode, I've done a lot of reading here and after much learning much about IB subs here - I have the bug. I have made up my mind to do it and shore up the wall to reduce the vibrations. I will be ordering components near the end of November for a build to start Dec and finish at the end of Dec - My company has a mandatory vacation period one week at the end of the year - so the idea is to spend that week finishing up the subs and be ready for a new year of bass.

My current thoughts on setup are the following based on what I have read here:
- minidsp - was looking at 1124, but minidsp is more....geeky??
- Behringer EP4000 - good old standard with plenty of true RMS power
- 4 Fi IB318 18" drivers (I have over 50 * VAS behind the wall - so I am good there)
- one or 2 manifolds - have not decided - more on that later

This appears to be what many people have gone with in the threads.

My main goal is to have something that is great for both music and HT. I have a Magnepan setup right now and they are not the best HT speakers and blending the Magnepan 3.6 and subwoofers is near impossible. But I have read that IB subs are different in that way. I really hate one note bass and bass heard that is the result of cabinet resonances and do know what a sub is supposed to sound like. My biggest fear with and IB sub is that it is going to shake the front wall badly(just from the air pressure) - and that will affect the sound. The front wall is a staggered stud wall and as such is more prone to vibrations. I will have to do some sort of stabilization of the front wall.

One thing I would like some advice on before I order the drivers(and begin the few weeks wait) is should I get the 2ohm or the 4ohm version of the FI IB318 drivers?: http://store.ficaraudio.com/ib318
Per the driver wiring diagrams on this site I believe I could get 4ohm or 8ohm bridged configuration with either the 2ohm or the 4ohm drivers. It that is true - which is better - is there a difference? I guess there is less windings on the 2ohm version?


Spoiler - here is the finished front line.

Mike P. 11-23-12 12:01 PM

Re: Christmas Build

Whether you get the S2's or S4's will depend on how you want to run the amp. A pair if S2's can be wired for a 4 ohm load, one pair to each channel of the amp. 4 S4's can be wired for a 4 ohm load and the amp would run in 4 ohms bridged mode.

You want to avoid a 2 ohm load on a EP4000, if pushed hard it will kick out on thermal overload.

blitzer 11-23-12 05:07 PM

Robo266317 also helped out with this........Simply wire two pairs in series and then wire the those in parrallel.
eg. (from http://www.bcae1.com/spkrmlti.htm )

Thanks for your help. I ordered the ep4000 and 4 IB318 drivers today.

I will be designing the manifold(s) this weekend.

blitzer 11-24-12 01:52 PM

Re: Christmas Build

2 Attachment(s)
My original thinking was to put 2 manifolds under my screen on the right and left side, but it turns out that I would have to saw through about 8 inches of concrete to do so. I have never sawed through concrete. So I am contemplating the design you see below. The idea is to output below the center channel speaker that is attached to the wall.

The cube holding the drivers is 2' X 2', but could be wider if I need a bigger output hole. The current design opening into the room is 24" X about 11". The blocks that the manifold is sitting on are 4" tall.

Anyone have thoughts on this design?

Mike P. 11-24-12 06:57 PM

Re: Christmas Build

Your manifold opening, which is 264 square inches, should ideally equal the total area of your drivers, which is 750 square inches. Your manifold is 35% of the drivers Sd, you need to go bigger.

blitzer 11-24-12 09:16 PM

So this configuration is not ideal because 24" x 24" is only 576. Maybe I can make it wider.

vann_d 11-25-12 12:02 AM

Re: Christmas Build

Yes, you need to go bigger as Mike suggested. You are basically horn-loading your subs with this configuration. The response can be simulated using Hornresp program but it would be much more predictable if you could enlarge the area to at least 4x sd of Fi IB318

vann_d 11-25-12 12:05 AM

Re: Christmas Build

If you could at least make opening the size of one side of the manifold it would be a lot better

vann_d 11-28-12 05:36 PM

In my build I'm planning on similar config but with 2 manifolds. Each one with 2 opposed IB 18s. They will be flanking the mains. Makes it a little easier to get the opening required.

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