Rotary Subwoofer Install Blog

October 12, 2006

Pics of various venting points

Filed under: Uncategorized — bassment @ 12:33 pm

garage vent… inside that cavity, looking down, is another 7-8sq ft opening into the area behind the dual TRW install. So air pressure waves, in addition to venting into the bath/office outside the media room, also vents into the garage, albeit through a bit of a chokepoint. Trust me, there is lots of air pressure making it’s way through that opening into the garage… how can I tell? The garage doors slap around like pieces of cardboard.

the larger of the vents in the office and media room.

different angle, yes, I know, the paint didn’t quite match… it came out of the same can!
The flash bulb convicted me of faulty work here… but you’d be hard pressed to notice it in person.

the front side vent in the media room… again that damn flash bulb hints at what is normally unseed, i.e.
the insulation behind the foam grill. Hey, in person, this stuff all looks halfway professional!


Eqpt rack… red switch starts the twin turbines… the Lake EQ can be seen just below the DVHS. Bruce’s custom turbine amp below the HTPC.

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October 11, 2006

ultimate Haunted House

Filed under: Uncategorized — bassment @ 4:39 pm

This just in from Bruce…a haunted house ( in Tallahassee is using a TRW to create wierd and scary sensations for their c lients… apparently it’s a scream. Check out the video below… look at the door carefully…

Haunted House shaken by TRW’s

TRW chilling the Haunted House

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How to EQ and Crossover Five Subwoofers?

Filed under: Uncategorized — bassment @ 11:37 am

start with this:

Lake Contour EQ/crossover

this puppy has two XLR inputs, presumably from your subwoofer left and right outs (though you could also feed it subwoofer and LFE out, whatever, it can work from two inputs or one input and create almost anything you want).

Anyway, Bruce loaned me this puppy for evaluation (he is a dealer for Lake), and I am in love with the accuracy and capability of this EQ. After using pro audio junk like Ashley’s, I really appreciate a well done DSP based EQ/crossover.
So, this Lake takes in my subwoofer left and right out, sum’s them into a mono signal (at my request), and then splits out 4 signals for the two fans, the XS, and the left and right Watchdogs.

You can adjust the crossover points, filter shape, add EQ up and down anywhere, add phase adjustments, delay time, etc… really a very powerful unit.
Their new flagship EQ (about $5k)  has extremely low THD…  the unit I am looking foward to buying for myself.

October 10, 2006

TRW impact on movies… here are numbers

Filed under: Uncategorized — bassment @ 11:14 pm

I’ve taken some spectral analysis during some movie sequences suspected to have low bass content.
These snaps are of a peak hold FFT during the scene… so you are seeing the maximum SPL levels reached between 0 and 90 Hz for the 2-3 minute clips of interest. I believe Bruce and I calibrated this mic when he was here, so the SPLs should be somewhat accurate, but I’ll do the cal again soon, just to make sure.


this is HHGTTG (dts5.1), when the earth is demo’d. Notice that we’ve almost reached 115dB at 10Hz. Cool.

I need to post another snap of what happens without the TRW’s.

m and c cannon scene dts5.1 w TRW.GIF

this is Master and Commander (dts5.1), with all 5 subs woofing away. Pretty cool to listen to.

Nearly 110dB SPL across 1-5Hz.

m and c cannon scene dts5.1 no TRW.GIF

Now for the same scene in M and C without the TRW’s. The crossovers are set so that the XS is responsible for the performance around 20Hz.
You can see that it does pretty respectably down to 18Hz at 100dB or so… not bad at all!
My sentiments at this moment are to first calibrate the mic once again, and endeavor to make sure that these SPL readings are in fact accurate. Because if they are, I want to see 110-120dB SPL peaks being reached instead of 100-110.
I think. I am not sure… 120dB might just rattle the room apart as I’ve noted before… but 115 seems doable without drywall crumbling to dust.

I have put some fiberglass just behind the grill covering the TRW’s manifold … this has reduced fan self noise, but perhaps whacked a few dB off output. I have the following courses of action, again, assuming the mic is calibrated:
1) increase amplifier output… right now I am at 12 o’clock on the dial.
2) I could try opening the garage door or window up above… that provides more venting back space
3) I could try opening the media room office door…that would provide ultimate venting.
4) combination of 1 and 2or3.

I’ll check with Bruce as well… he got a clean 120dB out of the system with pure tones…I need to acquire that software and see if I can duplicate our earlier outputs.

Tomorrow I will post some pics of the finished install areas. I am no finish carpenter, but I did a decent job on the grills for which I copied Winstons original design.

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October 2, 2006

Crossover challenge

Filed under: Uncategorized — bassment @ 5:57 am

Just to be clear in the post below, what I ultimately wanted to do with all four subs was have the following happen:

1) Left Watchdog get all the 30-80Hz of all left channel signals, mains/surrounds/subwoofer

2) Right Watchdog get same, for all the right channel signals

3) XS to get mono 20-30Hz

4) TRW to get mono 0-20Hz

Unfortunately, the Lake, although extremely capable, did not allow us to set a given output to be any mixture of inputs. You can have any output assigned any filter, but they all share the same input mix. Which meant for my application that I had to go mono to all the four subs above.

October 1, 2006

Rotary Subwoofer early conclusions

Filed under: Uncategorized — bassment @ 9:54 pm

After a full day of watching movies, examining real time spectrum plots, calibrating mics, soundcards, and more, we came up with the optimal solution for deploying the TRW technology.

Thanks to a tip from Ilkka at, we learned what we had wanted to test for ourselves, which was that the L and R main channels have significant sub-bass content. And that the LFE does not get all the sub 20Hz content. There were several movie clips that did not show up sub 20Hz on the LFE, but did show up later when we had the crossover configured as I am about to describe. This is very important for those who have a separate LFE and subwoofer channel to understand and test for.
Recall that I have one Wilson XS driven by a 2400 Crown K2 amp, and two Wilson Watchdogs with their integrated 400W amp and eq, and now the twin rotary subwoofers, aka the TRWs.

We tried various combinations of the TRWs with either or both of the XS and the Dogs. The Dogs and TRWs provided an absolutely anemic experience at the movies. Clearly 20Hz+ is as vitally important as sub 20Hz. You must have both in balance, otherwise it just sounds wrong.

The XS and the TRW’s didn’t quite satisfy either… there was still something missing… slam, concussion, violence, in the movie clips. Concussion needs both sub 20Hz AND 40-80Hz, that much we learned from extensive testing today.

But how to put all four subwoofers together into an integrated and pleasing subwoofer solution? Clearly the TRW’s own 0-20Hz. Clearly the XS is better at 18-30Hz than the Dogs, and the Dogs, well, let them have from 30-80Hz. Which means we need one sophisticated crossover to handle all of this, and a crossover that can EQ and handle down to zero Hz, AND with low distortion.

Enter the best EQ on the planet… the Lake Contour. Two inputs, 6 outputs.

Here is what we did. We used the stereo Sub setting crossed at 100Hz, and turned off LFE on the Lexicon… doing so mixes the LFE with the Sub L and Sub R. The Lexicon automatically takes all the sub 100Hz in the L and R channel and, along with the LFE, shoves it into the L and R subwoofer channels, respectively.

We take the Stereo L and R sub outputs from the Lexicon and XLR them into the Lake Contour.
The Lake Contour can mix the two inputs together, so that’s what we do.. inside the Lake the L and R are mono’d. This mixing of stereo to mono was necessary so that the XS and the TRWs could get the mix of both L and R subwoofer bass… this was the only way to do it with the Contour, that I could see.
Now, we separate the mono signal internal to the Lake, and carve out the following 4 outputs:
1. TRW’s at 0-30Hz
2. Wilson XS at 20-40Hz
3. qty 2 Wilson WD’s, at 40-80Hz.

This provided a bass output that was so crisp, clean and violent, that we simply had to tone down by 3dB the two Lake inputs while watching WOTW. The lightening, the alien machine foot steps, everything was threatening to liquify the room and the body. Again, I have to say, I was, for the first time ever, cringing at the anticipation of the next infrasonic blast heading our way… finally, I can say the goal of ultimate bass has been achieved.

There is no room to improve from here. Distortion and SPL ouput have simultaenously been optimized to an extreme level. Where we can improve is on fan self noise. My room is extremely quiet, and when the movie is perfectly silent, you can hear what amounts to a normal air conditioner type of air noise.

Bruce is quite confident we can knock that all the way down to inaudible, it’s just that we simply ran out of time… they are flying back tomorrow AM after 14 days non stop here. They will be back in 4-6 weeks doing their next install in the SF Bay area.

The solution to knocking the self noise down is more fiberglass and turning the fan speed down a bit. We have so much available headroom we can easily make up for the resulting output loss with more volume.

This week I will post pics of simultaenous spectrum graphs alongside the movie running, so you can get an idea of the calibrated SPL levels we are reaching in the room.

Bottom line is that one really needs three subwoofer technologies to fully exploit the film sound opportunity. The TRW for 0-20Hz, a large multi 15 or 18″ driver subwoofer(s) for 18-30Hz, and several smaller subs 15-18″ that are tuned for output in the 40-80Hz region. With the right crossover and sound processor, one can achieve levels of bass that will absolutely frighten the most diehard bass fan.

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.

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