Rotary Subwoofer Install Blog

September 25, 2006

HVAC, Electrical mods are all done…

Filed under: Uncategorized — bassment @ 1:00 pm

The HVAC guy just completed his part. Rejiggering the supply and return plenums, cutting new grills into the soffit, and capping off the soffit modifications. We also went from 16″ to 14″ plenums to make more room for the TRW’s.

Electrician did his thing… brought down a 240V for the motor controller (Altivar 31), moved a ceiling lamp fixture into two sconces on the wall.

Bruce is now wiring the motor wires and voice coil wires up as we speak.

Winston is building the side and bottoms of the manifold. I have been searching for an RS-485 to RS-232 adapter so as to control the TRW motors from the HTPC, so I’m off to R&D Electronics in Fremont to get one for $50. We’ll also wire in a motor on/off remote switch at the equipment rack in the rear of the theatre… this gives us a completely remote controlled solution with an HTPC software GUI for command/control.

Today’s been very productive. Bruce hopes to power up the TRW’s with blades sometime this evening.

Status Quo: HVAC done. Electrician done.  TRW rough install done.

Yet to Go:  Light Framing/Drywall repair.  Room cleanup.  Manifold completion. TRW powerup and tuning.

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September 24, 2006

Second (and final) TRW goes in…

Filed under: Uncategorized — bassment @ 7:03 pm


The second TRW is now installed, and both are roughly concentric. The final tweaks will occur with the fan blades in and a rear reinforcement needs to be added to deal with axial forces from the voice coil.

The motors will be driven by an Altivar 31 motor controller, which will tell the motors how fast to spin, and this will be totally adjustable by PC software on the HTPC. The LFE signal from the Lexicon MC12B will feed into a 250W amp that will drive both TRW’s directly from the amp using 12 gauge speaker wire routed through some conduit that we fortunately installed from day one.

Next step is to wire in the motor controller, build the bottom and side of the manifold box, and line the manifold box with 3.5″ fiberglass batting (from Home Depot). Then we’ll use some perforated drop ceiling lighting grills to act as a grill into the media room, and for the back vents inside the bath/office area. We may or may not use additional back venting in the garage… we’ll see after some testing.

More pics tomorrow.

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First TRW goes in…

Filed under: Uncategorized — bassment @ 3:15 pm

The pics here show the view looking from the media room ceiling through the hole in the wall, towards the manifold openings for the TRW’s.

The last pic shows the first TRW installed. Winston is adjusting positioning to get concentricity between the fan blades and the manifold opening.


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September 23, 2006

SPL versus fan noise

Filed under: Uncategorized — bassment @ 9:58 am

One thing we are trying to balance is SPL output vs noise … more SPL is available if there the manifold is shallow, however, this comes at the expense of more fan noise. The deeper the fan sits back in the manifold, the more high frequency fan noise is captured by the baffle insulation, but then SPL starts to be impacted.

So, this is what we are working on today as we build the manifold. Also we are designing the mounts for the TRW fan motor drivers… we will hang them upside down from the garage floor parallam joists. This will isolate the fan motors and vibration from the media room completely. Good solution.

More pics coming later today.

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TRW exploded parts and assembled snaps…

Filed under: Uncategorized — bassment @ 8:11 am


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Point of no return

Filed under: Uncategorized — bassment @ 8:01 am


Now we start moving HVAC ducting around so as to make a wide open space for the TRW manifold box to sit on top of the bath/office ceiling, and blow into the media room. All that framing above in the second pic has to come out. The ducting in the third pic has to be moved, which was not trivial. Oh, and the ceiling fixture that was in the ceiling had to be converted to wall sconces. Also note the office door leading up the ground level… if needed, we can vent the backside of the woofer through a screen door here.


Bruce Thigpen taking measurements… the TRW install has to be done in motion, as we open up the ceiling and walls, we get more visibility into what can be done with what dimensions.


All of the framing and drywall above will need to go… this separates the media room from the office/bath ceiling.


The drywall surrounding the soffit has been removed.


So now we have removed all the drywall on the soffit, the soffit framing, the soffit, and the drywall sealing the media room off from the office. Notice the 30 degree angle… Bruce wanted a flare opening as the air pressure waves enter the media room, because it improves the efficiency of the TRW, which results in more SPL at VLF.

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Point of no return

Filed under: Uncategorized — bassment @ 7:45 am

When we actually demo the soffit and punch a hole through the media room wall, then we’re not turning back. It took some consideration to get this point. Before today, the media room was air-tight… non trivial expenses, such as the magnetically sealed IAC sound doors, were undertaken to keep the room air tight, to minimize sound incursion/leakage. Now that will be partially compromised, because the media room will have an air pathway between the media room and the bath/office, and possibly the garage and/or garage attic.

However, in the pursuit of maximum bass, nothing shall stand in our way, even reasonableness.

In the leftmost picture below, you can see the soffit before we start the demolition, in the upper left corner of the photo. These pics were taken Thursday 21, 2006.


So there it is… the soffit is down, and the point of no return has been reached. Next step is to breach the drywall above Bruce’s head in the right most picture.

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Point of no return – the demolition starts

Filed under: Uncategorized — bassment @ 7:34 am


First thing to do, before Bruce and Winston arrived from CEDIA, was to have the bath and office ceiling removed. Above, one of our demo team tapes the media room IAC sound door, and the cherry cabinets where all the CD’s, vinyl and DVD’s are kept.


Better to score the drywall with a knife, instead of the Sawz-all. The knife method cuts way down on dust. Now reaching the point of no return!


The media room office ceiling is down… still we can easily repair this, so we can still easily turn back.


Above you can see the office ceiling clear, with some framing yet to remove, and the bathroom behind it. Also now cleaning up the mess.

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Installing the TRW – the implications

Filed under: Uncategorized — bassment @ 7:15 am

Installing the TRW into an already finished room is no simple feat. The TRW must stride a boundary between the room of interest and a sufficient back space volume. For an existing home theatre, this means cutting into a or ceiling, no other way around it! For my particular situation, since I am underneath a garage, the ceiling was out. The walls were out, because on the other side of the drywall is 12″ concrete, then mother earth.

Except for one wall – the wall leading to a basement popout which houses a half bath and a small ‘office’. It was the wall between the media room and the bath that Bruce and I focused on the possibility of installing the first ever TRW. It turns out that there is an HVAC chase that runs between basement and the garage and garage attic, and this chase is pretty wide (12-15 sq feet) and starts above the bathroom ceiling corner.

So we decided, that if we could install the TRW(s) above the media room bathroom ceiling, pushing air into the media room at ceiling height, that we could then backport the TRW into the media room bath/office (via a ceiling grate) and also into the garage and garage attic via the HVAC chase. Of course, the HVAC chase is not fully available to move air in and out because about half of it is occupied by fat 14″ SoundCore plenums.

But this was and is the only possibility to meet the unique install requirements of the TRW. As a last ditch backup, we could always install a screen door on the media room office external door (leading up to the ground level), and let the TRW’s vent to the outdoors. But that is not preferable (though it is optimal from a performance point of view) since the VLF pressure waves have a chance of being noticed by neighbors, as during the demo.

All this boils down to readily accepting the fact that one will have to do serious room surgery. Demolition of framing, drywall, the resulting dust, possible unforeseen damage to equipment, etc… The best way to get over that anxiety is to bash open a few pieces of drywall and get way past the point of no return.

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September 22, 2006

BAAS Demo of the Thigpen Rotary Woofer (TRW)

Filed under: Uncategorized — bassment @ 11:16 am

Bruce Thigpen and Winston Wright flew out on the Eminent Technologies corporate aircraft, complete with one TRW-17 rotary subwoofer and all the necessary installation retrofit needed to temporarily affix the TRW (we’ll refer to the new sub unit by TRW from here on out) to a door leading to my media room.

Bruce and Winston were very careful in crafting the temp install… the TRW, unlike all conventional subwoofers, needs a large space behind the room it is pushing air in and out of. In my case, we used the great outdoors as the back vent space. More on that later. So we installed the TRW into a doorway which then leads into a media room office. Winston constructed a nice temporary baffle to redirect the air pressure waves around the corner into the media room, via a temporarily open IAC studio grade sound door.

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The purpose of the demo was to install, for the first time, the TRW into a real home theatre, and try off the shelf DVD content, and see if the TRW made any noticeable difference. Bruce had prepared cuts from about 10 DVDs that he found had good sub 20Hz content. DVD’s with plenty of sub 20Hz content are not very common, but quite fortunately many of the action and suspense type films do integrate quite a bit of the VLF (we’ll refer to sub 20Hz content at VLF from now on). Perhaps for the purpose of seat shakers? Who knows, but the VLF is certainly there, as can be measured by analyzing the DD or DTS soundtrack.

Bruce ran through the clips with and without the TRW in the system. Mind you, this is comparing the Wilson XS and two Wilson Watchdogs with and without the TRW… so the TRW better do something significant to add to these three powerful subs. The audience consisted of several of SF Bay area members. We also invited Keith Yates who attended. Keith is THE eminent high end home theatre designer/acoustician in California, if not the world. His knowledge on acoustics and all things home theatre is unsurpassed. You can read the comments on the AVSForum thread where we discussed audience reactions.

Suffice to say the difference the TRW made was quite significant. After seeing/hearing with the TRW, the Vogon’s destruction of Earth scene in HHGTTG was empty and hollow with just the three subs, almost devoid of the rumbling that the TRW provided. The cannon shots in Master Commander were OK before the TRW, hitting you in the but. With the TRW, the cannon shots were shockingly violent. You were absolutely there in the cannon bay of the British man’o’war, getting a concussion from the black powder cannon blast. WOW! After these clips, I simply HAD to HAVE this TRW IN MY THEATRE!

Also, it’s worth noting that the official demo attendees were not the only to enjoy the virtues of VLF at high SPLs. Turns out we had some unintended attendees… namely my neighbors about 1000ft away. As was related by this neighbor (who I had not met before this demo nite), she and her cul-de-sac neighbors were walking around the neighborhood wondering what was shaking their walls and rattling their pictures. It was a slow shaking she said, much like an earthquake, except it kept going on and off for hours during the day. So she and her son started wandering the neighborhood looking for what was the source of this wierd vibration. Well, by trial and error she found out house, and I fessed up. Of course, I took her and her son down the the bassment for a demo, and she turned into an avid fan (no pun intended) and wondered how she might get one of these for their home theatre.

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Some YouTube video links: TRW subwoofer in action

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