Rotary Subwoofer Install Blog

September 29, 2006

Tuning has begun

Filed under: Uncategorized — bassment @ 1:12 pm

do you see that black door on the front left with the (mahogany framed) acoustic panel on it, in the picture below…

Well, I just heard from Winston (I am working in the office today) that at 115dB SPL, that 400lb door assembly is actually moving back and forth… ahem. Well, that isn’t exactly what we want to see. The backventing into the garage may not be cutting it in terms of surface area… we might have to vent to the outdoors through a screen door in the media room office.

Tonight for sure we’ll be posting hard data.

One last thing – Bruce accidentally powered up the amp while the TRW’s were running, and the transient impulse scared the p*ss out of me… it’s not like a loud noise, but more like some paranormal event. It happened twice more and still I it startled me significantly. The TRW’s will have a heck of a role to play in theme parts in the future!

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September 28, 2006

Construction phase complete – tuning now begins.

Filed under: Uncategorized — bassment @ 6:41 pm

Today we started at 0730 cleaning up both rooms. Surprisingly the mess evaporated reasonably fast, and by noon time we were all cleaned up and vacuumed. I put some fiberglass batting all around the back port space so as to further quiet down the fan noise.

Here’s what the front of the room looked like around noon:


Now, all the plastic is off the equipment, and the acoustic treatments are back on the wall, the left channel X1 and Watchdog are back in their place. BTW, I seem to have fry’d a right channel X1 tweeter. Led Zeppelin Whole Lotta Love was the culprit methings.

We still need paint of course, but now you can see the finished install of the TRW’s, sans the custom grill still to be designed and built:


Here is view of the back side of the TRWs:


Another view:


All of the above will be covered a breatheable grill cover.

Performance commentary: the room is really responding well to 0-5Hz, and Bruce tonight tweaked in new blade shapes, rpm’s for the TRW motors, switching frequency on the driver controller, etc… and the DC-20Hz curve is starting to look nice now.

We still are not satisfied with the high freq fan noise however. It’s quiet enough for a movie, but Bruce wants it much more silent, so he will work on this tomorrow.

By noon, Bruce feels we’ll be previewing some movie content and getting a feel for the bottom line, so to speak.

Bruce also is making me a custom mic that will measure down to <1Hz, and my HTPC will be able to show demo attendees the full spectrum response of the room to the TRW’s.

Tomorrow we should also start posting performance graphs… stay tuned for the news…

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September 27, 2006

More discussion and background can be found at

Filed under: Uncategorized — bassment @ 6:25 am

fwiw, if you’re interested:

September 26, 2006

when will we know?

Filed under: Uncategorized — bassment @ 11:09 pm

We should know the final results of this install saga sometime over the weekend. By that time we’ll have tested a couple of crossover alternatives and gathered alot of test data.

The goal, however, is known by all. The goal is to hit 120dB SPL as flat as possible between DC and 20Hz. I’d like to see 125dB SPL, but Bruce just won’t commit to that just yet.  Let’s recognize that 120dB at 10Hz is something like 10 or more Wilson XS each being driven by a 2000W amp. Bruce can chime in with the exact figure of merit here.

We’re at the 2/3rd point… TRW’s have been powered up…read on for what happened!

Filed under: Uncategorized — bassment @ 10:41 pm

OK, it’s Tuesday. Just to close off on that RS-485 issue, I had to buy $250 of software and RS-485 adapter gimmicks from Schneider Electric (supplier of the TRW motor controllers)… all of which was worth about $25. Nonetheless, this will fix the HTPC to TRW command/control connection.

Onwards… the box was completed this morning as you can see below… the first two pics show the inside of the box. The fiberglass batting is transparent to sub 20Hz frequencies, but absorbs well the modest higher frequency noise that the fan blades stir up. The second pic shows both TRW’s ready to bite the air. The 3rd pic shows the manifold fully assembled. The 4th pic shows the view from the media room, looking at the front left ceiling corner… into the manifold area.


Now the drywall guy is repairing our demo work… thanks Ramon and Javier for coming out on such short notice! You can see the manifold fully assembled, the TRWs in the back like cannons ready to fire.


OK, so we fired up the TRWs around 3pm. I was a bit anxious… I just destroyed the air tight sanctity of my media room, demo’d a perfectly nice soffit, ceiling, introduced dust and soot everywhere, all in the pursuit of sub 20Hz bass. So this first power-up test better do show potential for massive performance… this first test better show that our concept for the design of the manifold would provide the sufficient opening into the room, and sufficient back volume to let the TRW’s fulfill their potential, all without disturbing the peace outdoors or in the house.

Bruce hooked up the 250W amplifer to the TRW speaker wires, his laptop output to the amplifier input, and started his pink noise LFE test. Mind you, this was at 1W amplifier output. The media room doors were open at the time… and the hallway wine cellar door started shaking like a ghost was inside and wanted out. I had to close the IAC sound door to stop that nonsense… now we know why we should always install very heavy sound doors… so that the TRW will be unable to shake the 300 pound door leaf from it’s magnetic seals. The SPL in the 1-10Hz range was already at 100+ dB, and this was at 1W of amplifier output power. Talk about efficiency.

Then I went to close the media office/bath exterior door, as at this time we were venting outdoors, just like in the BAAS test. This caused the back venting to be limited to the media room office, bath, and garage area. As well as some area between the media room walls and the concrete surrounding foundation. Bruce related that the output dropped 3dB. We moved upstairs into the garage to see how much power was being back vented, via the AC plenum chase. The concrete garage floor was shaking underneath us in certain spots. The garage doors were hitting against the framing. So I had another idea. I opened up the door into the attic, which created more back vent volume. This reduced the garage floor banging to almost zero, but still we felt the garage floor shake. Simply amazing, for 1W!

Tomorrow we continue to improve the manifold design to further reduce high frequency noise. It’s already acceptable noise floor for movies, perhaps not so in my ultra quiet media room for 2 channel, at least not yet. Also tomorrow, Bruce continues to EQ the TRWs, via the amp’s on board EQ system. We need less output between 1-10Hz and more between 10-20Hz. Simple matter of playing with fan speed and the EQ. We’ll get it there.

One final open issue is the finish of the various new openings in walls and ceilings… I am searching for a suitable grill that lets the air pressure changes pass efficiently, but that block the unsightly ceiling and manifold views.

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September 25, 2006

Now I remember why we went to IP …

Filed under: Uncategorized — bassment @ 9:50 pm

Some codgers, esp in the custom install world, maintain the world should operate by RS-485 and other serial protocols. Well, after a day of hacking and whacking and still not making two points talk over RS-485, I declare serial dead. I remember many times getting caught by the RS-232 rx/tx snafu’s… is it straight or crossover from point to point?

Well, all devices in the home should be ethernet addressable, with TCP/IP stacks. Let every command/control word flow over a TCP or UDP stream. Life would be just so much simpler. Note to all vendors of things that need configuration or monitoring: get with the modern world and network your stupid boxes.

We wasted alot of time trying to get a PC to talk to the Altivar 31 motor controller this  afternoon over RS485. We have not finished the manifold boxes. Thus we have not powered up the TRW’s to check for noise floor. The drywall guy comes tomorrow, so we better be all done with the boxes and do his framing for him by 4pm tomorrow.

edit: in talking with Altivar tech support, we found out that the software they included with the motor controller is some demo piece of junk, and won’t even work with the new firmware inside the current motor controller.  So on top of RS485 issues, we have software that doesn’t talk to hardware.

Schneider Electric gets a major boo from us … another fine example of a vendor who treats their customers poorly.  Not only doesn’t the bundled software work with the motor controller, but we have to BUY the real software, AND it has to be shipped… can’t download it over the net. Very weak.  FYI, this is a French company.

On the plus side, once this motor controller software comes up, you can get lots of info about the motor driver status, control RPMs, switching frequency, all kinds of stuff.

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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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