Rotary Subwoofer Install Blog

September 30, 2006

Lexicon MC12B RCA outs – not good for low bass

Filed under: Uncategorized — bassment @ 12:33 pm

A tip for all you bass hounds… the RCA out LFE cuts off around 10Hz, but the XLR LFE out goes practically down to DC.

We noticed this because the current TRW amp sports an RCA in and we saw much less output below 10Hz than the BAAS demo. I went to Guitar Center and got an XLR to RCA adapter cable, then took XLR LFE from the MC12B to the TRW amp, and all the 0-10Hz reappeared.

But it is quite cool that the MC12B does give the FULL spectrum in it’s surround processing… thank you dearly Mr Lexicon… you did the right thing damn it!

Also, I can confirm that the Crown K2 amp cuts off at 10Hz, just like it’s spec says… we were testing the Wilson XS below 20Hz, and the amp wouldn’t let us go below 10Hz. BTW, the XS does a more than impressive job below 20Hz, down to 10Hz… I would not have guessed it could reach the SPL’s it did… it is quite a respectable piece of subwoofer.  Respect out to Dave Wilson, once again.

Hard Numbers are in…

Filed under: Uncategorized — bassment @ 12:00 pm

OK, here are the results of the installation of the dual TRW’s seen here in this blog.
First let me say that Bruce wants to convey this data to show what the distortion is at given frequencies vs SPL.
Actually the 120dB here is more like 125dB, but he wanted to be conservative, but do understand that the distortion figures hold more or less for another 3 to 5dB. The charts below are all SPLs and distortion measured at the golden seating position.
Distortion for 1Hz at 120dB SPL
tzucc install 1Hz 120dB.jpg

Distortion for 7Hz at 120dB SPL
tzucc install 7Hz 120dB.jpg

Distortion for 9Hz at 120dB SPL
tzucc install 9Hz 110dB.jpg

Distortion for 12Hz at 120dB SPL
tzucc install 12Hz 120dB.jpg

Frequency response of TRW solution, at seating position, about 1/2W of amplifier power:
tzucc install freq resp.jpg

We are going to tweak up the crossover to get closer to 20Hz on the upside, so as to blend with the Watchdogs better.
Note that this curve can be shifted all the way to 125dB SPL or more without compression. The point is you can see how flat the response is from 1Hz to 20Hz. Probably from 0 to 20Hz, but the mic probably doesn’t respond well to less than 1Hz:)

There you go… this establishes the TRW as a solution for previously unknown SPL levels at sub 20Hz frequencies, AND with low distortion. You can find reviews on the web for various 15″ and 18″ subs with phenomenally high distortion at levels like 95dB at 12Hz. Of course, this isn’t really fair, since most of these subs aren’t tuned for performance below 20Hz, but just to make the comparison for funs sake, it would take fifty dual 18″ subs to equal the current TRW install at 12Hz.
How’s that for a figure of merit? Again, it’s not a fair comparison, because these other subs aren’t tuned or designed to even try for 12Hz.

Next up is to get some graphs of SPL’s reached during various movie clips… check back tomorrow AM for that.

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Install Plans for reference

Filed under: Uncategorized — bassment @ 8:00 am

Given the amazing and surprising results of the TRW’s, I thought I would share the plan drawings so you can understand better how the TRWs are mechanically configured with respect to the room. It is hard to get a sense for the layout just from the preceeding pics.

Below shows a side view… the room on the right is the media room receiving the pressure waves from the ceiling install of the fans through the manifold, quieted down by insulation as the pressure waves travels from the TRW (rotary woofer) to the media room. To the left and below the TRW manifold are two small rooms, a bathroom, and an equal sized ‘office’ where I store movies, albums, CD’s, and cables/manuals. The volume of those two rooms together is about 1/6th of the media room itself. These two rooms are part of the back venting volume. Remember, it’s critical in this design to provide large amounts of volume on the backside of the ‘speaker’ (TRW). The second pic is the top view looking down from the sky into the manifold. ALSO notice that the backvent path continues into the garage, as noted in the first pic. The garage is more volume than the media room by about 15%, so that gives more than a 1:1 ratio of back volume, which is what Bruce ideally wanted.

tzucc woofer installation.JPGtop view concept.JPGtzucc hvac layout.JPG
The third pic above shows the HVAC layout, which was a constraint… we had to fit the manifold in between the supply and return lines, and because we would destroy part of the soffit to cut in the manifold, we also had to change where the vents in the soffit would be, on one side only of course.

Bruce and I were worried that the opening between the office/bath and the garage would be too constricting for efficient presentation of the garage volume to the TRW’s backventing needs. This opening could only be about 8 sq feet without cutting into the concrete garage floor up above.

However, as the numbers will soon show and First Impressions post show, the garage was receiving all the back pressure waves that we would have wanted. It intrigues me as to how efficient that small opening was in connecting the garage volume to the office/bath volume.

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September 29, 2006

First Impressions

Filed under: Uncategorized — bassment @ 9:51 pm

I spent the day in the office while Bruce and Winston got the TRW’s hooked up to my Lexicon and sound system.

I arrived at home around 5pm, and Bruce asked if I wanted to hear the good news or the bad news.

OK. What a way to arrive home after a week of destroying the sanctity of my media room! I wanted to hear good news and better news. Bruce is the kind of rare individual that offers no hype or sugar coating… he likes to talk facts. So, I better face up to the music and hear what’s what.

The bad news came first: the Wilson Watchdogs were picking up lots of motor noise, quite audible. Oh crap.

The good news, also bad news again: the media room construction simply cannot take the full output of the TRWs.
Well, this could be good or bad, depending on what SPL the room can and can not take.

The Watchdog problem turned out not to be a Watchdog problem, but some kind of wierd wiring snafu in the patch panel I was using… when we hooked the Watchdog directly to the Lexicon MC12B output, the Watchdog was absolutely silent.
So, this is easy to fix… the patch panel was there for when we had EQ’s that we wanted to patch in and out. The Ashley EQ’s distort too much in my opinion, and thus are out of the system anyway.

Now for the good/bad news. I sat down to hear and feel what was the issue with the high SPL and the room.
Bruce turned on a 7Hz test signal at 125dB SPL and I simply could not believe what we were observing.
The room walls were moving what I thought to be at least a 1/4 inch back and forth. But happened next was really unexpected. The 300lb door leaf on the IAC sound door was actually shaking and slapping the metal door frame. You have to understand that the door leaf is sealed to the metal frame with two full magnet surrounds… people who have been in my media room are typically unable to open the door because of the mass and the magnetic seal holding capability. I always have to pause the movie, and push the door open.

And 200W of amplifier power applied to the TRW was flapping this door in the frame like a piece of paper.

We’ll post actual frequency vs SPL vs THD charts in the next 24 hours.

Clearly, this TRW technology is by far, the most powerful solution for sub-bass.

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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