The Badwater Bass'n: 8 x IB15 two manifold Infinite Baffle

I decided to call my infinite baffle sub The Badwater Bass'n. For those that don't know, Badwater Basin is the lowest point in North America at 282 ft below sea level. I'm hoping to go 256 Hz below C level! (middle C is at 261 Hz but can vary from 256-280 Hz depending on scale). Since the sub system will be composed of two manifolds that are located in the crawl space under the living room they will also be below "see" level.

I am using eight (8) Acoustic Elegance IB15 drivers. They were purchased a little over year ago and were the last available with copper shorting rings. These were handmade by John Janowitz. The drivers are 8 ohms each and will be connected in 4 channels of 2 drivers for a 4 ohm load per channel. I have two Face Audio F1200-TS amplifiers powering the IB System.







I purchased two cast iron grills from Van Dykes. They were on sale for half price. I have been looking for grills for about a year now. I thought about getting the cast iron grill inserts for gas grills and even found some the right size. However,a couple weeks ago I found the ones below and decided to get them since I like the look.

On May 17 I cut the plywood for the manifolds. I bought 3/4" 11 ply birch veneer/poplar layers from Menards. It is almost the same as some baltic birch I used for another project and stiffer than Arauco plywood. I am only going to use one layer of wood and I was able to cut both manifolds from 1 piece of plywood. I cut it the same day I made another subwoofer. The pile on the left is for the IB system and the pile on the right is for the 12" dual opposed sub I made.



I cut all the pieces using my circular saw, a straight edge, and some clamps. I then cut the openings with a Jasper jig and my Bosch plunge cut router. I then glued the edges with PL Premium and clamped and nailed them together. I used some 12" strips of plywood to strengthen the joints by installing them vertically along the joints at each corner. I finished making the boxes on Memorial Day (May 28).



I removed the carpet and refinished the wood floors back in January. The joists run lengthwise in the room so I was afraid I wasn't going to get the manifolds symetrical. However, after more measuring they were going to be the same. I started the opening on Memorial day. I used my Rotozip for 3 cuts on the first hole and the router for the last cut. Because I have wood floors I was able to use one of the boards as my reference point. I then drilled a hole up from the bottom (I was in the crawl space) by the stud for the first corner of my opening. My opening is is 14 3/4" x 18 1/2". This size was dictated by the cast iron grates I purchased.

For the second hole I used the router for all cuts. I used a Freud spiral upcut bit and cut 1/4" at a time out of the 3/4" thick wood floor. For both holes I screwed the cast iron grate to the floor (with the screw in the scrap portion) and used it as a guide for the router or Rotozip. It worked great. However, I realized as I was cutting that it would have been even easier to make a guide using a scrap piece of plywood and screw it to the scrap part of the floor and then route around the whole piece of plywood.

Since my manifold is large than my boxes I had to reduce the ends of the manifold a little. My boxes are 17 1/4" wide and the manifold opening is 18 1/2". I bought some scrap 2x6" boards at Menards for a total of $5 and cut two for each end of the manifold. I slid them up between the joists and screwed them in. I made sure the inner boards had exactly 15 3/4" of space between them so they would line up with the inside of the manifold.

I have super chunk bass traps in the front of the room that go from floor to ceiling. You can see the bass trap in this picture.


I screwed the grate to the scrap portion of the floor. I then ran the router along one side with using a spiral upcut bit. I did about 3 cuts before going through the floor.


The hole is now cut and the grate is in place. I had to remove the bottom foot of my bass traps to allow space for the router to make the cut. The bass trap will actually cover one corner of the grate.


I cut some scrap 2x8's and made double ends for the manifold. My manifold opening is bigger than the actual manifold so I made the inner end line up exactly with the inside of the manifold.


I installed the manifolds last Wednesday. I slid the manifold under the crawl space near the opening. The drivers were handed down to me through the opening and I installed them in the manifold. Due to clearance issues, two of the drivers face in and two face out. I installed the in facing drivers first from the inside of the manifold and then the out facing drivers from the outside of the manifold. I just used #8 Spax screws for installation. I like them because I don't need to drill a pilot hole and they hold great in plywood. I used 1 1/4" screws with the points sticking out on the other side so that the full width of the screw is in the plywood.

After installing all drivers, I had my brother jack up the manifold to the joists while I pulled up from the top. I then fastened steel straps to four corners between the manifolds and the ends. I also put a strip of gasket material between the manifold and joists/ends to seal it up.

I had drilled a small hole in the bottom of the manifold and I used it to run a pair of wires through. I will move the amps to the basement, but for now I put them in the living room and ran the wires up through the grate. This will allow me to easily change the gain while setting things up.

I finished the build on Thursday evening and then went camping for the next three days. However, I did get a change to listen Thursday evening. It is absolutely incredible! The sound quality beats anything I have ever heard and the headroom seems infinite. It has the slam of ported subs and the extension of sealed. The bass is so clearly defined, articulate, and musical. My wife listened and she even commented on how good it sounded.
 

Edited by desertdome - 6/6/12 at 1:45pm

I listened to a bunch of bass intensive Blu-ray clips Monday night. The cannon shots in Master & Commander are amazing. You feel like you are on the ship. One of my favorites is the long flight and crash scene from Flight of the Phoenix. I used to have two Buttkickers mounted to my floor joists and the tactile sensation when the plane rolled was really neat. With the IB the whole floor and couch are shaking with a much more defined tactile feel. You feel every shudder of the plane and the room feels like it is coming apart.

Here is the manifold from the top looking down. I couldn't have made the manifold any smaller.

The in-facing drivers have enough excursion clearance and won't hit the frame of the out-facing drivers.

Thanks. I am crossing over at 100 Hz and haven't EQ'd yet. I haven't had time yet to start measuring and I'm having too much fun listening. I will be using JRiver Media Center for all playback and it is very flexible regarding crossover frequencies, slopes, bass routing, parametric EQ, and limiting. I have owned a DCX2496 and a miniDSP in the past and they don't come close to the flexibility of JRiver.

Here are the subs I have owned and used in my living room:

• Hsu VTF-2 Mk I
• Hsu VTF-2 MK III with MBM-12
  - later added two Buttkickers in floor joists
• av123 MFW-15 single with Buttkickers
• av123 MFW-15 dual with Buttkickers
• Dual MFW-15 Turbo's (Acoustic Elegance custom AV15 driver with two customized Dayton SA1000 amps)
• Dual DIY dual opposed subs with MFW-15 drivers and Dayton SA1000 amp
• IB with 8 IB15 drivers and 2 Face F1200TS amps

Here is what I have also heard in the past 6 months:

• Danley DTS-10
• Rythmik F15
• CHT SS-18.2
• CHT VS-18.2
• dual CHT 18.T
• Elemental Designs A7S-750
• dual Seaton Submersive HPs
• dual JTR Orbit Shifters
• dual JTR Captivators
• dual JTR Captivator S's
• dual Hsu VTF-15H
• dual Lilmike F-20 Cinema subs

I'm not going to comment on each subwoofer system since I did most of that in the GTG threads. I'll will make more comparison comments to my own systems once I EQ the IB. There could be some peaks that are coloring my immediate impressions and I want to make sure I am comparing more apples to apples regarding frequency response and integration with the mains.
One pair of subs is wired opposite the other pair so they all move inward at the same time.

Thanks. I'm just glad I don't have to deal with spiders and snakes. My brother does HVAC systems in Los Angeles and has to always be on the alert for Black Widows and Brown Recluse spiders.

For those interested in these drivers, more may be available soon. John Janowitz posted on the Acoustic Elegance forum in May 14 the following info:

Thanks for all the kind comments.

HuskerOmaha was trying to come up with a name for his build. I was trying to think of places that went low, such as Death Valley. I was googling a bunch of stuff and then saw that Badwater Basin was the lowest place in the U.S. I couldn't resist the play on words/concepts and decided to keep the name for my own build.
I should have taken a picture with the SubDudes propped underneath the manifolds. You and Dennis will have to come over sometime. In a few more weeks I hope to have the living room finished with LS-6 line source mains, Bill Fitzmaurice's Wedgehorn 6's for surrounds, Seymour AV retractable AT screen, and the IB subs.

I first started reading about infinite baffles subs at the Cult of the Infinitely Baffled about two years ago. It is a great site and has lots of information about IB systems. I particularly enjoyed reading all the build threads. After reading for a little while I realized the crawlspace under my living room would probably work for an IB. I bought 8 of the MFW-15 drivers and originally planned to use them for the IB. Soon after buying the MFW-15 drivers, John Janowitz announced in a thread at Acoustic Elegance that he might not have anymore IB drivers for a long time. I contacted him and bought the last 8 drivers with copper shorting rings. I received the drivers a month to two later and have been storing them for the past year.

I had several challenges in installing the build. There is an electrical conduit the runs under the living room and brings the main electrical service into my house. It didn't leave much room for the manifold and I also thought the frame of the drivers might hit it. I also have an HVAC duct for the living room located at the front of the room and near where I would install a manifold. The joists were different widths and different heights (one was 7" while the others were 7 1/4"). Rather than make my manifolds to fit the width of the joists, I decided I would fasten them to the 2x8 ends I was installing instead of the joists. I could then space the ends the exact width I needed. I also wanted the manifolds to be as small as possible. Due to clearance issues with the front brick wall in the crawlspace, I would need at least two of the drivers to face out. This doesn't leave room in a small manifold so I needed the other two drivers to face in. I also had two walls to deal with in the front left corner. I measured and it looked like an in-facing driver would just fit against the left wall. You will see what I am talking about in the pictures below. The manifolds ended up being in the only joists bays that I could use and are perfectly symmetrical in the room.

Here is the right manifold. You can see the conduit made for a close fit. The plywood for the IB was the first plywood I have ever cut with my circular saw. I cut it with some clamps and a straight edge. Some of the cuts weren't quite accurate because my straight edge slid a little on the first cut. I wasn't too concerned because the PL Premium fills the gaps just fine. After cutting the plywood for the manifold, I then cut the plywood for my Lab 12 Dual Opposed project. These cuts were much more accurate and the sub turned out looking very good. The little strengthening strips are 12" long because I can cut up to 12" with my compound miter saw. I had a 3" x 8' strip of plywood that I cut down to 12" and then ripped in half with the compound miter saw. If the brick looks bad it is because it is 122 years old and has some badwater stains.


The side shot of the manifold shows the 4" of clearance between the driver and front wall. This also shows the first driver I installed and I forgot to put the binding posts at the bottom in my excitement at finally loading the drivers. At the top you can see the joist that was only 7". I had some little scraps of plywood that I glued to the top of the manifold before jacking the manifold up.


Like I mentioned earlier, I made the ends so they were the same width as the manifold this made it easy to attach the metal straps. You can also see the gasket I put between the manifold and the joists/ends.


The left manifold was wedged between the wall and the conduit.


There was so little clearance that the driver actually touches the wall. The manifold is mounted over to the right as far as possible.

The LS6's have been almost done for a long time. I have everything on hand to finish them and did an under round on the woofer holes. I wanted to protect them more so I applied a coat of Miniwax gloss wipe-on poly. It didn't dry properly so I did some research and found out that poly doesn't work over rosewood due to the oils in the wood unless the rosewood is first coated with a wax-free shellac. I stripped off the poly using mineral spirits and then applied some wax-free shellac. It looked good in some places but terrible in others. I then decided to strip the speakers down to the veneer. I've been working on that using Zinsser StripFast Furniture Refinisher. It is removing all the finish without changing the color of the veneer. These are Palisander which is the brown tinted veneer. I have the speakers in my office and I open a window and work on them during lunch. It has been slow doing it that way. I've been too busy with other things to spend a weekend working on them.

After they are stripped I will apply the shellac followed by several coats of the wipe-on poly. Then they will get lined with NoRez, port tubes installed, filled with some polyfill, and have the drivers and tweeters installed. The crossovers are finished with the exception of adding a few bypass caps.
I'm looking forward to seeing what happens when I crossover the LS6's lower than the low pass on the infinite baffle. With 4 sources of midbass I'm hoping to get a much smoother frequency response. How are you integrating the LS6's with your subs?