I am doing it myself (except the carpentry and masonry). Most of the manifold will be built with narrow cynder block short walls. The sub needs a round 20" hole smack center of the manifold opening (vertical/horizontal).

What was the story with the fact hat Tony, wen he installed his, had neighbors all around him clamoring as to what the unkknown sound was? I have a couple neighbors and worry they'll shut me down after install....Can the vented sound be contained somewhat relative to the outdoors...?

This one is NOT VENTING OUTDOORS. as long as you dont vent out you are fine, what is in the basement the Chateau Laffites? They may get knocked around a bit.;)

Jeff, tzucc only had that problem during the demo, when it was being vented entirely outdoors.

that was when the demo was done and he had an infinite baffle

http://cineramax.com/images/NewPlanSub.jpg

Wasn't the comment made that the back space should equal the size of the theater ?

Art

Wasn't the comment made that the back space should equal the size of the theater ?
Art,

Ideally. However, I believe Bruce has stated that you can get by with less.

Hi

I do not know the particular of the Rotary sub but I would assume it likes an infinite baffle... Venting it outside is the perfect case of Infinite Baffle. What problems did it create when the back wave was vented to the outside?

the neighbors 1000' feet away getting an overwhelming sense of dread...

the neighbors 1000' feet away getting an overwhelming sense of dread...
:) :p

Actually that is not a joke :D they were canvassing the neighborhood trying to figure out what was going on.

Rene

I do not know for sure but it seems like the main problem were the neighbors... getting an unhealthy dose of fright producing infrasonics... :) ... The rule of thumb in Infinite Baffle is that the venting volume must be at least 4 times the Vas of the driver , with 10 times being ideal, there seem to be no sonic benefits above 10 times. Oustide venting is infinite of course...

I will not go TRW , I will go IB though in my next HT and with a vengeance...

I believe the Vas of the TRW is infinity, since there is no suspension compliance returning the blade to a neutral position.

I believe the Vas of the TRW is infinity, since there is no suspension compliance returning the blade to a neutral position.

Then the best results would be attained by venting (literally) ;) the back wave outside. It is more a social than physical problem in all truth.

Bruce has changed his tune on this one, here thare are no neighboors in any direction for at least 1.5 football fields away, the house rests om a peninsula. Still Bruec insisted that venting to the backscpaece would work, considering th subplatform manifold.

These rae architects blueprints (not showing the manifold or proper platform height of 31" with a 15.5' first plat.).

http://cineramax.com/images/Architects-rendering.jpg

http://cineramax.com/images/Architects-rendering-plan.jpg

I look at the drawings above and don't see a 1/4 of the size of the theater to where the sub vents.

I have an adjacent posder room next to my theater that is approx 8 X 7 X 10. It opens to a billiards room that is approximately 25 X 25 X 9. THe theater is on the other side of the billiards room on one wall and adjacent to the powder room on another wall.

I could vent it into the powder room and that would be a 1: 8 ratio, BUT with the powder room door open, it would be about a 1:1 ratio with my theater. What happens if the door to the powder room is closed? DOes the sound disappear?.. I also want to know what other venting sounds to expect through my house and how loud?

And how loud is the fan when it is running? How far must it be away from the theater so as not to hear it operating / spinning?
So many questions...

Hi Jeff,

I look at the drawings above and don't see a 1/4 of the size of the theater to where the sub vents.

I have an adjacent posder room next to my theater that is approx 8 X 7 X 10. It opens to a billiards room that is approximately 25 X 25 X 9. THe theater is on the other side of the billiards room on one wall and adjacent to the powder room on another wall.

I could vent it into the powder room and that would be a 1: 8 ratio, BUT with the powder room door open, it would be about a 1:1 ratio with my theater. What happens if the door to the powder room is closed?

It will rattle and vibrate violently! :eek:

With it open, it will radiate rather freely into the house. The only thing I could think of would be putting a large vent that would look like a return vent to


DOes the sound disappear?.. I also want to know what other venting sounds to expect through my house and how loud?

One issue here is that the more isolate your room is, the greater the output outside the room. In effect the TRW works in reverse with the room forming the effective "box" playing to the rest of the house unless you also confine the backside. Using a crawl space or basement would be less taxing to the rest of the house, but you will most certainly experience the effects through the rest of the house, and more than you currently do, although not really in a "loud" manner but still quite identifiable.

Mark,

You've been to my place.....any ideas? I'd like to try this out if I could do so without destroying my house.

I believe the Vas of the TRW is infinity, since there is no suspension compliance returning the blade to a neutral position.

I believe the equivalent Vas would be frequency dependent. There are centering forces on the blades both in the form of the spider that centers the positioning voice coil as well the effect of the chosen shape of the blades. BruceT mentioned that the shape of the blades could vary the effect from a strong centering force from spinning and airflow to a system with little or no centering, or even "negative" centering force (for lack of a better term at the moment).

I
And how loud is the fan when it is running? How far must it be away from the theater so as not to hear it operating / spinning?
So many questions...

It is not so loud, in the case above you don't hear it because of the manifold and the venting to the underseats which muffle the hig frequencies.

Hi

I am not still not sure why one can not just vent the whole thing outside (if that is possible) ... Just curious... Regardless of its actual Vas (if this parameter can really be applied to the device) venting it outside results in an IB.. case closed... or am I missing something here?

Hi Mark,

"I believe the equivalent Vas would be frequency dependent. There are centering forces on the blades both in the form of the spider that centers the positioning voice coil as well the effect of the chosen shape of the blades. BruceT mentioned that the shape of the blades could vary the effect from a strong centering force from spinning and airflow to a system with little or no centering, or even "negative" centering force (for lack of a better term at the moment)."

Yes, I wasn't more definitive because I wasn't sure how the modulation works in there; to me it seems analogous to base current drive in a transistor.

I'm not an EE, so I'm out on a limb here, but the same way I don't think you'd say the output impedance at the collector is determined by the base/emitter impedance, I don't think the modulation mechanism reflects Vas.

The fact that the TRW has output at DC to go along with its infinite xmax says to me that it must have infinite compliance and therefore zero Vas.

My backspace turns out to be 1/6th of the theatre, I believe. BRuce and I measure the response with this situation vs opening the door to the outside (same door that was open for the demo that caused neighbors to wander over) and the response changed. The door closed had more boost from 10-20 and the the door open had more boost between 0 and 10 ... I might have that backwards, but the point is that it was six of one, half dozen of the other, so I felt I hadn't lost anything by not venting to an IB outdoors.

The media room ceiling (garage floor) does move so enough that it causes the garage volume to fluctuage enough to slap the garage doors against the frame slightly... that's the only sign to the outdoors that the twin fans are operating. My next door neighbor has never complained (like he did when the vibrating gravel rollers were smushing down our driveway base rock)... though they just sold the house :) coincidence?

Just watched Blood Diamonds... great sub 20Hz bass in several scenes... honestly, you get your money's worth out of the TRW's if there are about 5-10 scenes where it kicks in hard.... movies like WOTW are almost too much ... you feel like you have a mild concussion by the end of that flick.

Hi

I am not still not sure why one can not just vent the whole thing outside (if that is possible) ... Just curious... Regardless of its actual Vas (if this parameter can really be applied to the device) venting it outside results in an IB.. case closed... or am I missing something here?
FrantzM,

We tried that when the original demo was done at tzucc's theater. At the demo, the Thigpen
Rotary Subwoofer [RTW] was actually outside blowing through a hole in a plywood baffle that
was placed in an outside doorway close to tzucc's theater. Hence, the RTW was vented to the
outside.

In the evening, we were visited by a couple of tzucc's neighborsl They informed us that they and
many of tzucc's other neighbors were afraid to go into their homes, because they thought that
they were experiencing a "swarm" of earthquakes.

That's the problem with venting to the outside - it upsets the neighbors. These very low
frequency waves propagate far, and have disconcerting and unwanted effects on the
structures in the immediate area. If one didn't have neighbors to contend with; venting to the
outside would be ideal. However, most of us don't live in rural areas.

And my point is that venting to interior spaces that aren't even nearly equal to the theatre volume isn't much of a compromise as my install showed via measurements.

These very low
frequency waves propagate far, and have disconcerting and unwanted effects on the
structures in the immediate area. If one didn't have neighbors to contend with; venting to the
outside would be ideal. However, most of us don't live in rural areas.


How far does it travel? If my closest neighbors are 50' away will they have a problem?

How far does it travel? If my closest neighbors are 50' away will they have a problem?
Mitch,

I'm afraid 50' is NOTHING to these waves. When the demo was done at tzucc's; the effects were
felt within an area a quarter mile in radius.

The neighbors that finally tracked down the source of the sound said that neighbors for a
quarter mile around were evacuating their homes. These two neighbors were scouring the
entire area attempting to ascertain the source of the sound. It was difficult for them to
localize these very low frequencies. It wasn't until they were right outside tzucc's house that
they were able to tell that his house was the source of the sound.

Since we're talking about waves that are on the order of about 10 Hz [ from a few Hz up to 20 Hz,
so 10 Hz is a good order of magnitude], we're talking about waves that have a wavelength of
100' or more. So even though your neighbors are 50' away; that's HALF a wavelength or LESS!!

How far does it travel? If my closest neighbors are 50' away will they have a problem?

Sound attenuates over distance. The issue with very low frequencies is that with sound waves this large, it takes something similarly large to block or re-direct them. Adding to the variables, temperature over the ground and above can also affect how sound travels. The classic example is sound travelling over a small lake at night vs. daytime. Basically if the sound energy is radiated outside, it will fall off at a rate of approximately 20dB for every time you move 10x further from the source. Other than a hillside, not much will stop 10Hz, where it will just attenuate into environmental noise.

As Morbius said. In this context, 50' is rather close. If your room is not constructed to greatly isolate sound, there is still hope if sound leaks to the great outdoors from both the room and the backside of the TRW. An attic would work reasonably well in this regard.

Hi Mark,

"I believe the equivalent Vas would be frequency dependent. There are centering forces on the blades both in the form of the spider that centers the positioning voice coil as well the effect of the chosen shape of the blades. BruceT mentioned that the shape of the blades could vary the effect from a strong centering force from spinning and airflow to a system with little or no centering, or even "negative" centering force (for lack of a better term at the moment)."

Yes, I wasn't more definitive because I wasn't sure how the modulation works in there; to me it seems analogous to base current drive in a transistor.

I'm not an EE, so I'm out on a limb here, but the same way I don't think you'd say the output impedance at the collector is determined by the base/emitter impedance, I don't think the modulation mechanism reflects Vas.

The fact that the TRW has output at DC to go along with its infinite xmax says to me that it must have infinite compliance and therefore zero Vas.

To those reading along, excuse the geek-speak, as it really doesn't have any effect on how you might enjoy the TRW, it just is interesting to further explore how it really works and compares to other means of bass reproduction. That and I'm going cross-eye over CAD drawings and this is a good/fun break. ;)

Noah,

I think you are on track, but have a few of the behaviors reversed. The blades rotate at a constant speed, and the spider that centers the coil is plenty linear for its range of use. From this I think it's safe to consider the system to in fact have a relatively constant compliance WRT frequency (Cms in T/S terms). The TRW does not have infinite X-max. The blades have a maximum pitch and there is a maximum pressure differential (albeit quite high) beyond which the motor starts to stall. The output at DC and the non-conventional output vs. frequency limit comes from the fact that effective radiating area, or surface area (Sd of a conventional woofer) is frequency dependent.

The effective area at a given frequency is(should be) proportional to the angular rotation of the blades per 1/2 cycle. As such, from a T/S perspective, as frequency drops the Sd increases. Since Vas is a lumped parameter of Cms(constant) and Sd(inverse : F) the Vas increases with lowering frequency, and would in fact approach infinity towards DC. The difference in measurements when the rear space was opened suggests that there is some correlation to conventional T/S models, even if the model would have to be frequency dependent. We should be cautious in assuming what the relative parameters might be since the shape of the blades and many other geometric factors including fan speed will affect these things. The point is that the operation doesn't necessarily defy the models, but there are some more complex variables.

20 Hz has a wavelength of 56.5'

10 Hz has a wavelength of 113'

5 Hz has a wavelength of 226'

And we are tlaking about LOTS of spl. So it will take quite a lot to stop these waves.

OK here are some photos of my theater and adjoining bathroom and family room....

Any ideas for placement would be helpful.

I'd like to cut into this large soffet which is 28" X 28". It goes directly into the rear corner of the theater (also pictured). . That soffet is below my master bedroom closet. Fortunately, it is MY closet and not my wife's;). It could vent into my closet which is 8 X 14 X 10 (1120 cubic ft). My theater is 5400 cubic ft. I could let it vent in the closet or I could build a soffet up the one wall of my closet into the attic space (which is extremely large)...

The wall where the wet bar is is the rear corner of my theater. The powder room where I want to possibly put the rotary is next door.
http://www.winglake.com/images/components_current/rotary005.jpg


Note the alrge soffit over the doorway. It is essentially empty. To the right (not shown in photo) is an old shower that is drywalled over. So that is an empty space that could be used if needed. The shower is against an outer wall..

http://www.winglake.com/images/components_current/rotary006.jpg


This is the outside, opposite front corner of the theater. Note the digging at the front, that is wherethe generator is going that I asked about a few months ago. They poor the slab on Monday. The master bath windows are on the second level.
http://www.winglake.com/images/components_current/rotary012.jpg


This is the rar corner where the soffit ends. This is where I could open it up and let the air in...
http://www.winglake.com/images/components_current/rotary002.jpg


Here is the soffet. The other side of the wall here is the theater. THe soffet there goes right to that rear upper corner.
http://www.winglake.com/images/components_current/rotary015.jpg

Hey Mark! (Seaton)

I'm curious about this 'subwoofer'. I see a picture on page one with a fan blowing into a hole in a fiberglass filled box... Is there only one 'fan'? How can this generate any significant SPL? I don't see any other pictures.... I see only 1/2 inch plywood and a fan... looks like a DIY job if you could just get the 'fan'. Anymore pictures?

Hi Jeff,

I never saw your basement area, but I recall you having a separate HVAC system that kept the equipment room from over-heating. I was thinking that working out some ducting from the back wall thru the equipment area to the basement would make the most sense where the basement would pose the least annoyance to the house or neighboors. Not sure if this is a possible option or not, but that would be where I would first look.

Hey Mark! (Seaton)

I'm curious about this 'subwoofer'. I see a picture on page one with a fan blowing into a hole in a fiberglass filled box... Is there only one 'fan'? How can this generate any significant SPL? I don't see any other pictures.... I see only 1/2 inch plywood and a fan... looks like a DIY job if you could just get the 'fan'. Anymore pictures?

'Long time Health Nut,

There has been a TON of discussion on this forum about the device and how it works. Search out the other threads and search for posts about it by BruceT (Bruce Thigpen - inventor and manufacturer of the device) and myself. Yes, it works. ;)

Hey Mark! (Seaton)

I'm curious about this 'subwoofer'. I see a picture on page one with a fan blowing into a hole in a fiberglass filled box... Is there only one 'fan'? How can this generate any significant SPL? I don't see any other pictures.... I see only 1/2 inch plywood and a fan... looks like a DIY job if you could just get the 'fan'. Anymore pictures?

Health Nut,

It's a special fan - one that has blades whose pitch is controlled by the audio signal.

So when the audio signal goes positive; the blades pitch "positive" and pressurize the room to
a "positve" pressure. When the signal goes negative, the reverse happens, and the room pressure
goes below ambient pressure.

Oscillating pressure is what we call sound.

It DOES develop VERY significant SPL. When we did the demo at tzucc's theater, we were
regularly treated to single digit frequencies in excess of 100 dB.

Jeff,
I've never been in your upstairs. Front wall outside, left is dining room right is bathroom back is projection booth and rec room ?

Art

Hi Jeff,

I never saw your basement area, but I recall you having a separate HVAC system that kept the equipment room from over-heating. I was thinking that working out some ducting from the back wall thru the equipment area to the basement would make the most sense where the basement would pose the least annoyance to the house or neighboors. Not sure if this is a possible option or not, but that would be where I would first look.

It is possible to get it to the basement. But the theater is on a slab. That slab is 3 ft from the basment. So, I'd have to knock out a portion of the basement wall, burrow to the theater and punch through the theater wall. I could do it, but it could be more of a PITA than my thoughts above.

Jeff,
I've never been in your upstairs. Front wall outside, left is dining room right is bathroom back is projection booth and rec room ?

Art

Art,

Looking at the outdoor photo, the window to the right is the living room, and further right (out of the picture) is the dining room. The bathroom is around the corner to the left of the AC condensers there and down about 20 ft. The master bath is on top of the theater (see the three windows). My closet is to the left past the bathroom, just over the powder room adjacent to the theater.

It DOES develop VERY significant SPL. When we did the demo at tzucc's theater, we were regularly treated to single digit frequencies in excess of 100 dB.

Sounds good, I'll require 4... Then I suppose you still need soemthing to cover the 30-80 Hz range more adequately.

So when the audio signal goes positive; the blades pitch "positive" and pressurize the room to a "positve" pressure. When the signal goes negative, the reverse happens

I understand, it is just hard to believe that the fan can generate that much pressure... I'm defientely a fan of accurately reproduced bass into the single digits. I have my (4) 18 inch Black Hole Subs tuned to 14 Hz and ports 10 inches in diameter which outperform dual Wilson XS subs.... Was thinking of going with a large IB using (12) 18 inch drivers next... May still do that since it is more cost effective and can cover 5 Hz thru 80Hz (although likely would only use it from 5-60 Hz depending on if I use the N802 or upgrade to a more full range speaker)... Any reason why you people wouldn't want to just use (12) 18 inch drivers mounted into the front wall and backfiring into a room behind the theater which can also hold amps and various HT equipment..?

I don't see a problem just mounting (12) 18 inch drivers in the front wall... perhaps 4 vertically with three rows wide in one corner... crossed at 50 Hz and below.... I don't care about 1-5 Hz as much :) Would need amps such as those designed by CROWSON technology who specifically designed with no subharmonic filters and allow flat to 2 Hz. I believe a large infinite baffle, one that I have seen nobody else do, might be the way to go... I'm considering all options, but I think a small room behind the front wall of the theater holding the amps and otehr equipment is useful anyway... for custom, why not just use (12) 18 inch drivers? As you know, IB doesn't require lots of power because of the huge 'enclosure'. Again, I don't know anybody who has implemented (12) 18 inch drivers in an IB design directly into the room, but that is my plan so far... Simpler to integrate and digital EQ... Just seems to make sense to me.

Art,

This shows the bathroom down a ways along the theater wall
http://www.winglake.com/images/components_current/rotary010.jpg



This is the wall that follows the bathroom wall. The powder room is to the left.
http://www.winglake.com/images/components_current/rotary008.jpg

Hell Jeff , you're set ! Just build the right angle enclosure on that wall and rock ad roll ! :) That looks perfect , no limitations at all.

Art

Art,

I'd like to try and make this work....The whole idea is a bass head's wet dream!

Being 18 and in school working on my degree with 2 years to go... and reading these threads.... is pure torture.

Jeff, do it for everybody that can't. :p

It is possible to get it to the basement. But the theater is on a slab. That slab is 3 ft from the basment. So, I'd have to knock out a portion of the basement wall, burrow to the theater and punch through the theater wall. I could do it, but it could be more of a PITA than my thoughts above.

Hmm... I thought the basement extended under the equipment room? Isn't that where the air ducts go down to the basement?

The TRW needs a manifold of some length with turns, so routing back through somewhere isn't a problem, but yes, having to cut into the foundation is never fun.

If you did the "chute" up and out, I would absolutely plan on enclosing the pathway through your closet so the direct radiation is into the attic. You'd have to talk to Bruce to see how much opening area you would need.

The basement is still my pick if there's a reasonable way to drop down to it from the theater.

My 2c.

Healthnut... without exagerating... 4 fans could crack walls.

Tzucc has two smaller ones, and when it gets going (with a 200 watt amp driving the blades) the walls move SIGNIFICANTLY. they had to dial the system way back from its top potential.

And his room is built as sound as they come. His garage floor upstairs moves when there is too much sound.

This is about as far from a DIY as they come. THis is a totally different way of doing sound.

.. Any reason why you people wouldn't want to just use (12) 18 inch drivers mounted into the front wall and backfiring into a room behind the theater which can also hold amps and various HT equipment..?

Just seems to make sense to me.
Health Nut,

Doesn't make sense to me at all. As Bruce Thigpen ["brucet" on this forum] noted in our previous
TRW discussions, there is one HELL of an impedance mismatch between a cone subwoofer
and the air in the room.

Look at it this way. In one half cycle, how much air can 12 18" drivers move?

Well the area of a single 18" driver is about 254.5 sq inches, and a dozen will have an area of
3053.62 sq inches. Lets be generous and give the subwoofer a 3" excursion. So the volume of
air moved will be 9160.9 cu inches; or about 5.3 cu feet.

The TRW can move WAY MORE air than that!!! The effective "excursion" of the TRW is the
blade pitch times the rotational speed of the fan times half the period.

Additionally, the source of the acoustic power of the TRW is NOT the amp that modulates the
blades; that's just the "driver stage" to use amplifier terminology. The acoustic energy being
fed into the room is actually coming from the MOTOR driving the fan. Now we're talking power
measured in HORSEPOWER - FORGET your subwoofer amps that are rated in WATTS.

Because of the physics of the TRW; it will beat an array of subwoofers; HANDS DOWN!!!

Here is a photo of my basement. The theater slab sits 3 ft past the basement. You can see where ductwork already enters this unused space and heads toward the theater. THe space to the immediate left of the duct work is empty inside and where I could possibly use to run the venting. This dead area between the basement wall and the theater is enclosed by the roof but inaccessible. It is simply unused space that was leftover after we renovated the home. This wall is 3 ft from the theater. If I removed a few concret blocks over the transformers pictured (and marked), I could possibly get a flexitube (if you can use one of these) through the basment wall and take it into the middle row area of my theater. It would go through the basment block (pictured), make a 90 degree turn upward and then another 90 degree turn into the theater. With the constraints of the small space, it cold only be a flexible tubing. I could mount the Rotary sub in the basement anywhere....

Would this work or must the rotary sub be in the immediate theater wall. Could it be mounted 10 or 15 ft away from the theater?

http://www.winglake.com/images/components_current/100_0044.jpg

No flexitube can be used; whatever you use has to be extra rigid. I think that if you kept the path reasonably voluminous 31x28 (I know works) all the way to the theater it could work.

I wall point this situation out to Bruce.

Thanks.

I might be able to do a rigid duct with a little luck. What dimensions are required for the rigid duct? How wide, tall, etc? How far back can the fan sit from the theater?

Bruce knows about the dimensions but it may be necessary to slide down the 4 eqitechs to gain 4-5 inches. Let's see what he has to say.

I could move the top two Equitech's without much of a problem.

Jeff, Could you start your own thread on this problem solving , design and and ultimately the building of your TRW set up ? I think it would be a great resource.

Art

Will do Art.

I may have found my way to do it!

I'll get some pix and show.

Anyone who thinks there's no infrasonic information on current DVDs needs to find and read the 3-part reviews/tests of subwoofers done by Keith Yates and published in 'stereoplile ULTIMATE AV', issues June, July/Aug., and October 2004. I don't know if 'stereophile' has made it available on the website; if not, perhaps a bunch of you should ask that they do.

DVDs he used were 'U-571', 'Black Hawk Down', and 'Pearl Harbor'; he also used the 'Jurassic Lunch' cut of Telarc's 'Great Fantasy Adventure' CD.

Yates summarised his findings in one column; I'll send an image of that to anyone who e-mails me at jeffreybehr(at)cox(dot)net.

The winner was the Genelec HTS6; IIRC its price was $13K in 2004.

http://www.genelec-ht.com/products/hts6/hts6.php

Anyone who thinks there's no infrasonic information on current DVDs needs to find and read the 3-part reviews/tests of subwoofers done by Keith Yates and published in 'stereoplile ULTIMATE AV', ..
Jeffrey,

Keith Yates was in attendance at the demo of the Thigpen Rotary Woofer [ TRW ] at tzucc's
theater.

When this demo was done, Bruce Thigpen had a spectrum analyzer running on a laptop
computer, and connected to a microphone in the room.

As we played DVDs and "heard" and felt the subsonic content; we could also see the effect
of the subsonics registering on the spectrum analyzer. We could see what frequencies were
present and their absolute and relative magnitudes.

It's not surprising that DVDs have infrasonic content. Movie soundtracks have infrasonic
content, as many commercial movie theaters have infrasonic subwoofers, usually
"bass cannons", which are long Helmholtz radiators; behind the screens.

Rather than go through the effort of filtering the infrasonics from the movie soundtrack when
the DVD is mastered; the mastering engineer just writes the full spectrum of the movie soundtrack
to the DVD.

Mark,

"I think you are on track, but have a few of the behaviors reversed. The blades rotate at a constant speed, and the spider that centers the coil is plenty linear for its range of use. From this I think it's safe to consider the system to in fact have a relatively constant compliance WRT frequency (Cms in T/S terms)."

But those are the characteristics of the modulator, not the fan which is the source of the acoustic output.

"The TRW does not have infinite X-max..."

If the blades just stay pitched, the fan will produce a constant flux of air, though now I'm not sure DC airflow equates to DC acoustic output, if that's even defined.

"4 fans could crack walls"

Hmm. Fans have very low pressure capacity, so paralleling them might just cause more "slippage", not being positive displacement devices.

when the system is running and not even at top levels, the walls move. they could easily make them move much more. that could cause cracking.

Very possible, I'm just saying it's likely that the acoustic pressure doesn;t increase linearly with addition of more TRW's.

Jeff,

It's hard for me to follow what is going on with your pics. I'll try to spend more time and assemble an integrated image in my head of your house architecture.

But here are some things we learned in our install:
- forget tubing for the front or backside vent. Just delete this from your list. The TRW wants a square or nearly square aperture for the front and back side openings. In other words, 25 sq ft of narrow opening is very inferior to 25sq ft of square opening. My opening is about 2.something feet by 10 feet and Bruce feels it turns out to be less efficient than he had hoped for. Still kicks butt, but that's why he wanted to put two fans in... just in case the less than square aperture decreased efficiency. SO - you want a very open aperture directly to your room, with one 90 degree turn to absorb HF and MF and a very open aperture to your back vent.
- openings to additional backvent must be quite large in square-ish aperture as well.
My backventing goes to a volume 1/6th of the theatre, i.e. my bathroom and a 2nd attached small room. We made provisions to open the whole garage above as addtl vent space via an aperture in the garage floor/bathroom ceiling of about 6sq ft. It did absolutely nothing. The opening was too small. Strange.... you'd figure that air pressure changes would efficiently move through a 6sqft aperture... but the frequency response plots said no difference when we plugged that up and didn't plug it up.

My recommendation is to make sure you have the following, and if you do, you will finally be satiated in your quest for new bass extension:
1) 90 degree turn from fan into your room.
2) the aperture of the front side into your room, from the fan plate to the wall opening, should be kept constant and large and squarish.... Bruce can tell you what sq ft'age of this column you'd need.
3) this front side distance from fan to opening, via the 90 deg turn, needs to be no longer than a certain distance that BRuce can provide... I am going to say like 6 feet is ideal
4) the rear volume should similarly have a very easy time breathing through a straight shot of a square like short distance pathway. I have a 90 degree pathway using two separate vents into my small room and bath respectively. More specifically, the TRW's vent into a small crawlspace between my bathroom/room ceiling and the garage floor, and then I cut further vents into the ceiling (behind the fans of course) to vent into the bath/room areas with little 'resistance'.
5) I would not bend over backwards to get an infinite baffle. It seems that my much less than theoretically ideal back vent space produces reasonable additional spectrum and SPL to the XS and the Dogs.

Hope this helps.

"forget tubing for the front or backside vent. Just delete this from your list. The TRW wants a square or nearly square aperture for the front and back side openings. In other words, 25 sq ft of narrow opening is very inferior to 25sq ft of square opening."

I can't think of any technical reason why this would be true. And for the same crosssection area, a round section has less surface area/viscous flow losses, and is intrinsically much much stiffer and will flex less from the pressure pulses.

I think there must have been an unaccounted for implementation issue.

No Noah Bruce is ademant about this and it's Aspect Ratio. He hit me over the head witht the aspect ratio several times until I had to find a way to comply.

Peter, From what you and tzucc describe, it sounds like he was adamant about not having an opening that has a significant aspect ratio in one dimension vs the other. Round vs. square shouldn't be a problem.

tzucc,

Was that opening to the garage 6 feet square, or 6 square feet?

Also, I recall Bruce talking about typically wanting at least 2, if not 3, turns/folds in the manifold to acoustically low pass radiated noise. I may be wrong, but I recall more than a few of the demo setups having pathways much longer than 6'.

From my brief exposure and talking with Bruce, my feeling that many options can be made to work with attention to specific details. Since Bruce's company builds and installs each TRW, I suspect there is some room for adjustment and adaptation if conditions are known ahead of time. The main question I see for Jeff's case is if the cross-sectional area can be large enough to deliver sufficient performance without causing other problems. I suspect it can work, but Bruce is of course the one who has to make that call.

I can't think of any technical reason why this would be true. And for the same crosssection area, a round section has less surface area/viscous flow losses, and is intrinsically much much stiffer and will flex less from the pressure pulses.


Maybe because you're not technical enough. A large enough circle cross section is fine... obviously no one is suggesting it has to be 90 degree angles, but think about it... can you easily make a 25 sq ft circular opening, easier than a rectangular opening? My construction techniques say making a square is easier than a circle.

Peter, From what you and tzucc describe, it sounds like he was adamant about not having an opening that has a significant aspect ratio in one dimension vs the other. Round vs. square shouldn't be a problem.

tzucc,

Was that opening to the garage 6 feet square, or 6 square feet?

Also, I recall Bruce talking about typically wanting at least 2, if not 3, turns/folds in the manifold to acoustically low pass radiated noise. I may be wrong, but I recall more than a few of the demo setups having pathways much longer than 6'.

From my brief exposure and talking with Bruce, my feeling that many options can be made to work with attention to specific details. Since Bruce's company builds and installs each TRW, I suspect there is some room for adjustment and adaptation if conditions are known ahead of time. The main question I see for Jeff's case is if the cross-sectional area can be large enough to deliver sufficient performance without causing other problems. I suspect it can work, but Bruce is of course the one who has to make that call.

the two CES demo's Bruce's home attic install are about 6-8'. I have not seen any demo setup that is much longer than 6'. That doesn't mean it can't work... I do know Bruce has said that too long a path of any aspect ratio is not good either for efficiency.

My opening to the garage was about 6 sq ft total, but broken up in two pieces. The aspect ratio wasn't bad, it's just not enough cross section to make any usable difference.

6 sq.ft. makes sense that there wasn't much gain. At those frequencies and the size of the rear "room" an opening that size behaves somewhat like a large leak or a port who's output isn't used rather than a pathway to more open space. It probably does provide worthwhile help in relieving the pressure on the bathroom's walls and door! :eek:

You can model up the rear space as a lossy ported box and guestimate the "tuning frequency" of the opening. To work as an open pathway, you need the tuning frequency well above the operating range of the device.

A better word for me to have used would be theoretical.

Maybe because you're not technical enough. A large enough circle cross section is fine... obviously no one is suggesting it has to be 90 degree angles, but think about it... can you easily make a 25 sq ft circular opening, easier than a rectangular opening? My construction techniques say making a square is easier than a circle.

Noah,

A rotary woofers output sums and behaves much like a cone woofer. Adding
a second unit increases output by 6dB. Another interesting aspect is
horsepower. The current model is 1/3 horsepower. We have proved that upping
the power 10 times to 3 horsepower increases the output by 10dB. This
behavior is similar to a conventional loudspeaker. For the rotary woofer, given
enough horsepower, the acoustic output limit is very high but is difficult to
realize without sacrificing signal to noise ratio. In other words as you rotate the
blades faster, the maximum SPL limit goes up, but the generated noise also
goes up.
In terms of "slippage", it is the cone that slips at lower frequencies where the
cone velocity is very low relative to the velocity of sound. Pressure does not
want to build up in front of the cone, it simply slips aside.
We find very little compression in operation until the blades stall, at that point
the output dies quickly which is a ugly form of distortion. In an installation you
run the blades as slow as possible for the best signal to noise ratio with an
acceptable maximum SPL without stalling. The maximum is usually between
115 and 122dB between 1-20 Hz in most rooms. The 19 inch rotor is spinning
between 680 and 750 rpm. We try to pitch the blades to about plus or minus 45
degrees at the maximum.
Depending on blade geometry and blade chord relative to the pitch axis we
can expand or compress the audio signal. There are many nonlinearities, in the
speed range we run pressure is roughly proportional to the square of rpm so
the output goes up quickly is the rotational speed increases. Note that the
torque load also goes up and you run out of horsepower before the blades stall.
You are correct that a round opening would be best into a room, it is just not
practical to construct a round manifold in most installations. We want the
manifold to have the smallest pressure drop yet absorb the high frequency
random noise which is a product of the rotation of the blades.
In some respects the device is close to an acoustic transistor as you had
suggested earlier. Thanks very much for the comments.

brucet

Bruce,

"A rotary woofers output sums and behaves much like a cone woofer. Adding
a second unit increases output by 6dB. Another interesting aspect is
horsepower. The current model is 1/3 horsepower. We have proved that upping
the power 10 times to 3 horsepower increases the output by 10dB. This
behavior is similar to a conventional loudspeaker. "

It sure is; I stand corrected.

"In terms of "slippage", it is the cone that slips at lower frequencies where the
cone velocity is very low relative to the velocity of sound. Pressure does not
want to build up in front of the cone, it simply slips aside. "

I was speaking in terms of air volume displacement, but I see your point about acoustic output.

Very interesting further explanation of the TRW operation, thanks.

"it is just not practical to construct a round manifold in most installations."

Sonotube is available up to 5 ft dia, but that falls a bit short at 19.6 sq ft.

I guess square is good for the additional area for sound absorption.

And thanks for the thanks :)

Brucet,
If you had a long digital delay of the audio signal (say 10 seconds)
You could anticipate the upcoming demands on the sub-woofer and adjust the rotor RPM to accommodate.

http://cineramax.com/images/Helene.jpg
Since this house's interior design is NeoClassical and I did not feel like forcing this particular client (as I normally do) to do a contemporary design (regardless of the House motiff and his wife's wants), we brought in our old friends (of 18 years) First Impressions to collaborate in the design/implementation, along with the architect Zeb Jarosz and interior designer Austin Harrelson (www.austinharrelson.com) .

Working with Jeff Smith is very stimulating as well as personally satisfying to see how his style has refined itself over the years and the amazing accumumulation of tools of the trade/specialized contraptions, multistation cad staff , fully staffed Cabinet shop, staging areas, upholstery "sweat shop" and a cornucopia of inventive Home Theater resources he has accumulated in his 30,000 Square Foot home theater design showroom Global Command Center in North Miami.

www.cineloungers.com

2 weeks ago I got an email from Jeff saying:

"I've figured a way to cut into the backs of the front row seats so we can also blow up air up the asses of the people seating on the front row." :D :D :D

[PETER >>>NOTE TO SELF: Need to stop showing this picture to everyone.]
http://cineramax.com/images/Marilyn.jpg

How could I resist such a stimulating proposal? So we ran the idea by Bruce.

This is one of many sketches and 1st Imprs. Shop Drawings used to run the design by Bruce:

http://cineramax.com/images/hELENEsUBpLATJ.jpg.

Although initially Bruce thought it could work, he later sent this drawing eliminating the front row vents.

http://cineramax.com/images/hELENEsUBpLATB.jpg

It is taking awhile to get the perfect design , but we are almost there.

You are correct that a round opening would be best into a room, it is just not
practical to construct a round manifold in most installations. We want the
manifold to have the smallest pressure drop yet absorb the high frequency
random noise which is a product of the rotation of the blades.
Bruce,

I believe you are correct that it is not critical to have a shroud or manifold around the fan.

I think many are thinking that annulus just outside the outermost blade tips would be a
region where the air would flow counter to the direction the blades were forcing the air.

However, such a hypothesis means that there would be a flow shear at the outer blade
tips. The air just inside the blade tips would go one direction as forced by the blades, and
the air just outside the blades would flow in the opposite direction since it would not be
propelled by the blades and the ambient pressure would force this counter flow.

However, fluids don't "like" to have a shear in their velocity field. Such a flow is
would be Kelvin-Helmholtz unstable. That is, if that flow pattern ever did develop,
it would very quickly degenerate into turbulence. It's very tricky to get a "stable" flow shear.

http://cineramax.com/images/Helene_-rear_elev.jpg
We got this tonight. The TRW has to be evenly centered on the mainifold opening.

Peter,
I am glad to see you are implementing the TRW. It looks like it will be a nice install.

Did you attend the JL Audio factory tour a couple of weeks ago that AVS put together?

Hi

I hope to "hear" (feel could be a better term), the TRW soon.. it is a pretty unique piece. The only infrasonics transducer commercially available. I wonder what it adds to pure music reproduction.
Congrats Peter!

Thanks guys. Yes it is exciting but a prime example of the saying: "be careful what you ask for..." the amount of detail in the project is overwhelming. Lot's of new technology coming to market within the next 6 months will be implemented, with deliverables affecting many critical paths. The projector is the sickest piece of gear but there is very little info available so engineering it's pill-box porthole, balanced power( nema connector type?) , heat exhaust, and mounting is all being flown by the seat of the pants (during development) .

The client wanted to shoot a rocket to the moon,well... it launched all right. I am comfortable the plot will get us there, the trick will be controlling the crash as best possible. These "Experimental Prototype Home Theater Of Tomorrow" projects are one fairly large sized , protracted, calculated risk. It is simultaneously nerve-wrecking and comforting.

Eric I did not go to the JL lab demo, but I would consider it for the next project due in spring, with the Torus and the d-box but no TRW.

Peter very cool. Why no TRW in your next project? What home theatre is complete without it, unless the design constraints prohibit it for some reason?

Space constraint for back wave, just not there.

http://cineramax.com/images/RotarySubManifold.jpg

so is the sound pressure emitting from underneath the seats or from the ceiling or?

Underneath the seats. Maybe the most efficient way of venting the TRW.

The communications back and forth via email did not always conveyed Bruces intentions as I understoood them, the draftsman was still trying to vent to the front row in the next to last version. But this according to Bruce should work well.

seems like the furniture on top of the pressure wave would absorb alot of the energy?

Perhaps that is what Bruce wants. The furniture does straddle the opening leaving a few inches underneath. The entire platform is floating so when the trw kicks in I expect hell will break loose.

What my client wants is to bring in his uncle to show him the landing scene of Saving Private Ryan. I told him that if one of the survivors of normandy by any chance made their way to that event, that their pace makers would stop right then and there.

well... I am not sure Private Ryan is all that bass intensive wrt the TRW.
The ultimate TRW demo movie is WOTW... it is downright sick with tons of 1-20Hz.
Too bad we have to put up with the moron known as Tom Crooz the whole time.

Is anyone aware of studios that are mixing/mastering with a TRW or the Torus? I mean, how are they aware that they're even putting this LFE into their mixes if they can't reproduce it? Especially dealing with Allen's issue at the beginning of the thread where someone walking down a hallway generated an 8Hz wave at 100dB.

How can a studio mix for such low frequency? Are they using IB subs or something?

None.

If the content is there, in most cases they are just simply not aware of it. It may be harmonics from existing recordings, it may be that they added it by hitting a very low note that had additional content that was unknown. THey may have even done a spectral analysis and found it there and not cared.

But mixing for it... no. THe standard in many mixing studios is Genelec. Some use some bag end, and then a mixed bag after that.

Is anyone aware of studios that are mixing/mastering with a TRW or the Torus? I mean, how are they aware that they're even putting this LFE into their mixes if they can't reproduce it? Especially dealing with Allen's issue at the beginning of the thread where someone walking down a hallway generated an 8Hz wave at 100dB.

How can a studio mix for such low frequency? Are they using IB subs or something?

All of the Muse HD Laserdisc were matered in Sony Studios culver city facility in the early nineties usng a 16 foot wide Torus gain 1.5 projectors: Dual stack HDIH.


This room has beeen subsequently converted to a flatscreen though. But about 130 tittles were eveluated using a Torus.

But mixing for it... no. THe standard in many mixing studios is Genelec. Some use some bag end, and then a mixed bag after that.

Dynaudio Acoustics (http://www.dynaudioacoustics.com/Default.asp?Id=290) is the fastest growing speaker in this market.

Bruce (was out here for yet another TRW install) and I burned the midnight oil Fri nite, getting my TRW's tuned in even further.
This time we took the time to work on time and phase alignment. Again, we worked on equalization and level adjustments between the TRW, XS, Watchdogs and the X1s.

We wrapped around 1am and I will post the eq screenshot when I get it off the HTPC.

Interesting conclusion, though one which the acoustics experts out there will say no duh.
Basically I had the TRW's amped too high in level. The result was novel, to be sure, but also the high 0-20Hz levels were masking out the 40-100Hz region, which plays an equally important role in synthesizing a realistic sound effect. Once we got it all in balance, and a bit better time aligned, the M&T cannons were far punchier and actually caused the hairs on my skin to crawl... and remember, I have seen this movie clip only 100s of times already, but never like this.

We have more to do here, since the time/phase alignment was done ad hoc... we will use impulse response features of the sound software to get more accurate.... I am sure we do not have timing just right yet.

Bruce, thanks for consuming more midnight oil on my room... you are a pleasure to work with. It's nice to work with someone who is even more particular than me.

Is anyone aware of studios that are mixing/mastering with a TRW or the Torus? I mean, how are they aware that they're even putting this LFE into their mixes if they can't reproduce it?
jmichaelf,

As anyone who had heard the TRW in tzucc's theater or at others knows; there definitely IS
low frequency content in these DVDs.

However, are the studios mixing/mastering with the TRW in mind? I doubt it.
The TRW is too new - and there's infrasonic material on DVDs mastered even before
the inception of the TRW.

The studios DO mix the soundtracks with low frequencies in mind for commercial theaters.
Some commercial theaters have "bass cannons"; essentially "Helmholtz radiators" [ a big
subwoofer in a long tube ] to provide bass reinforcement..

When it comes to mastering the DVDs, the studios don't master with ultra-low frequency
content in mind; they just don't take it out of the mix they made for the commercial theater.

That's why we see so much low frequency content in DVDs; it's there because the mastering
studio didn't remove it from the soundtrack that was mixed for the commercial theater.

From what I understand most commercial theaters are designed for LFE at around 30Hz to prevent too much bass from passing into adjacent screening rooms. It's these extreme HT guys who are focusing on infrasonics.

I don't think there's a question regarding whether or not super low frequency content exists, but whether the studios are mixing it appropriately. Like Allen observed in the first pages of this thread, getting hit with a 5Hz wave caused by a footstep might feel cool, but it's far from realistic.

The TRW and the Wilson-Benesch Torus are very interesting products and I would be very interested to experience content mastered for LFE down to the single digits.

IMNSHO, the W-B Torus doesn't belong in this discussion any more than Bag End or some others do.

I do think that ideally the early adopters would have a manual/remote control to shelf the <10-16Hz content per the program content. The existence of the content is usually appropriately correlated and desirable, but the relative level is of course in question. The TRW and any other device capable of getting down to or below 10Hz is the proverbial chicken, and hopefully some eggs get hatched in the studios.

From what I understand most commercial theaters are designed for LFE at around 30Hz to prevent too much bass from passing into adjacent screening rooms. It's these extreme HT guys who are focusing on infrasonics.
jmichaelf,

There are MANY "stand-alone" theaters that don't have this problem. There ARE
commercial theaters that have "bass cannons" that go way below 30 Hz!!!

The soundtracks are mixed with theaters that can go very low in mind. If a theater is
in a multi-theater complex, and they need to limit the low frequency content, then a
simple high-pass filter at 30 Hz can be applied. But these theaters don't set the
standard to which the soundtrack is mixed.


I don't think there's a question regarding whether or not super low frequency content exists, but whether the studios are mixing it appropriately. Like Allen observed in the first pages of this thread, getting hit with a 5Hz wave caused by a footstep might feel cool, but it's far from realistic.

One could say the same thing about commercial theaters that have "bass cannons", as I
point out. They have the capability to reproduce very low frequencies, and if the studio
were mixing such that 5 Hz footsteps were unrealistic - then there would be PLENTY of
complaints from owners / patrons of these theaters.

This whole "5 Hz footsteps" is a "red herring" anyway - footsteps are NOT mostly 5 Hz!!!
You need something fairly massive to resonate at 5 Hz!!

From what I heard in tzucc's theater with 2 TRWs - 5 Hz footsteps are NOT a problem.
In fact, Bruce Thigpen had a computer doing a live frequency analysis running during
these auditions, and the TRW was silent until needed for a depth charge, cannon volley,
shotgun blast...whatever. Nothing AT ALL unrealistic in the mixing!!

No - I believe the studios are mixing infrasonic frequencies properly; intended for those
commercial theaters that have infrasonic capability.

When the DVD is made; the mastering engineers don't filter out the infrasonic content;
so one is left with the same mix as was done for the commercial theaters.

For as long as recordings have been made mistakes, thumps, noises, edits etc. have been there. I always preferred having a system that reproduced the mistakes as opposed to one that masked them.

Examples of low frequency mistakes in films: In the movie "V for Vendetta" along with the synthesized "click" of a TV remote control button push is a fairly strong 3hz thunk. "The Good Shepard" had a completely out of character low frequency noise underlying a scene with dialogue. However Morbius is correct that the vast majority of films have low frequency effects which are exactly as they should be.

In the real world sounds go literally all the way down in frequency, an audio system should do the same. An audible form of distortion exist if content below 20Hz is not reproduced.

This is the integrated frequency response of tzuccs three woofer systems at the listening position, 2 TRW-17's cover 0-18Hz, 1 Wilson XS covers 18Hz to 40Hz and 2 Wilson Watchdogs operate 40Hz to 80Hz. We started the measurement at 1hz up to 100Hz, the rolloff below 1Hz is not indicative of the rotary woofer which is actually capable of a static pressure change in the room. Although not as flat as we would like, the integration between the three systems covering more than six octaves is getting close and there is plenty of headroom.

brucet
http://www.eminent-tech.com/avsimages/tzucclogsweep.jpg

There are MANY "stand-alone" theaters that don't have this problem. There ARE
commercial theaters that have "bass cannons" that go way below 30 Hz!!!Such as? JBL's biggest commercial sub (4642) supposedly goes down to 22Hz but you'd need a HUGE number of those to come close to the listening levels (at 22 Hz) you'd find in an average home theater.

In the real world sounds go literally all the way down in frequency, an audio system should do the same. An audible form of distortion exist if content below 20Hz is not reproduced.

I totally agree... HP from The Absolute Sound had an interesting system based on Quad and Magnepan Woofer panels with Athena crossovers.. I put together a similar system Quad ESL-63 + Athena Crossover with Magnepan Tympani Woofer Panels, this system would go easily below 30 Hz in my room.... It was easy to switch on and off the Woofer panels. It was striking to hear ch amber Orchestra works with and without the Woofers.. Huge Difference.. Without the Quad alone the attributes of the Quads came through.. the sound was good but just like a reproduction.. Good sounding but one is keenly aware it was music being reproduced by speakers albeit grood ones... With the woofers.. well... reality sets in... more music, There was not that much bass in the musical works but among other things, the "clang" of Harpsichord became lifelike and there was an apparent increase in overall in clarity.. I would not have expected from adding woofers to a good speaker.

Proper Bass reproduction is more important than people would think in recreating realism in our home... my first thread in this forum was about this very subject...

Even a perfectly clean flute note without tremolo---which is very nearly a perfect sine wave in its steady state---produces content all the way town to DC due to the transients of attack and decay.

Such as? JBL's biggest commercial sub (4642) supposedly goes down to 22Hz but you'd need a HUGE number of those to come close to the listening levels (at 22 Hz) you'd find in an average home theater.
Greg_R,

I covered that in my post above. Many commercial theaters have what are called
"bass cannons". They are essentially "Helmholtz radiators". You take one of those big
commercial subwoofers and you put it in a long tube. The tube "reinforces" the lower
frequencies.

Many commercial theaters have a few of these big horizontal tubes behind the screen.
It is the length & volume of the tube that determines the tuning - not the subwoofer. So
you get lower frequencies from the subwoofer - lower than it normally could support.

As I stated above; they are "Helmholtz radiators":

http://en.wikipedia.org/wiki/Helmholtz_resonance

Even a perfectly clean flute note without tremolo---which is very nearly a perfect sine wave in its steady state---produces content all the way town to DC due to the transients of attack and decay.
Michael,

EXACTLY. Mathematically, you can't be finite simultaneously in BOTH the temporal
and frequency domains.

Although not as flat as we would like, the integration between the three systems covering more than six octaves is getting close and there is plenty of headroom.
Bruce and tzucc,

Is the dip at 90 Hz a room "mode"; or is that just the transition between the "Dogs" and the X-1s?

I'll let BRuce address that, as my room has always had this dip, even before the TRW's integration. BTW, to correct Bruce on one thing, we did change the Watchdogs to go up to 100Hz. THe reason for the fast falloff after 80Hz, is that the pink noise signal (a mono input to the Lexicon) was going to the center channel only and so the Watchdogs were not getting help from the X1s and possibly there was a room mode in that mic position as well.

I can say that without the power of the Lake Contour EQ system, we'd never been able to get the curve as good as it was here. We had to apply all kinds of amplification and attenuation bumps here and there to fix room modes.

I
I can say that without the power of the Lake Contour EQ system, we'd never been able to get the curve as good as it was here. We had to apply all kinds of amplification and attenuation bumps here and there to fix room modes.
tzucc,

Since you had the 80 Hz dip all along; then it's probably a room mode. Not much one can do
about a NULL in the room response.

The response that Bruce posted is remarkably flat response for those low frequencies. I would
have expected a much "bumpier" response at these low frequencies.

Looks like the Lake is doing a pretty good job.

What is the Lake contour EQ? Can you provide a link or some informantion on the company?

Enlightening responses here. Bruce & tzucc, that is an impressive graph!

What is the Lake contour EQ? Can you provide a link or some informantion on the company?


http://www.dolby.com/professional/live_sound/products/index.html


http://www.lake.com.au/graphics/Sys_main.jpg

Thank-you!

Why all the quotes?

In any case, it sounds like you're describing organ pipe-type resonators (forget the term, acoustic labyrinth maybe), which are not Helmholtz resonators.

Greg_R,

I covered that in my post above. Many commercial theaters have what are called
"bass cannons". They are essentially "Helmholtz radiators". You take one of those big
commercial subwoofers and you put it in a long tube. The tube "reinforces" the lower
frequencies.

Many commercial theaters have a few of these big horizontal tubes behind the screen.
It is the length & volume of the tube that determines the tuning - not the subwoofer. So
you get lower frequencies from the subwoofer - lower than it normally could support.

As I stated above; they are "Helmholtz radiators":

http://en.wikipedia.org/wiki/Helmholtz_resonance

The problem with Helmhotz resonators is they Quickly unload the driver below the tuning point. They would have to filter the bass aggressively just below the tuning frequency. So if you tune to 20 Hz, they'd have tons of distortion and bottom out with lots of bass below 16 Hz...

Basically you extend your bass response a little lower and with less distortion around the tuning frequency, but then it rapidly unloads just below the tuning frquency. When I build ported subs, I tune them as low as possible, usually to 14 Hz (which yields better group delay and sound quality).

Anyway, the rotary sub is incredible that it can do 1-20 Hz. I just which it was linear up to 60 Hz...

Why all the quotes?

"I" read them as "if" they're "stressers" for particular "words" he's attempting to enunciate "via" text.

In any case, it sounds like you're describing organ pipe-type resonators (forget the term, acoustic labyrinth maybe), which are not Helmholtz resonators.
noah,

I'm talking about pipes whose volumes and lengths are large enough so that the Physics
of how they resonate is in occordance with those as described originally by Hermann
von Helmholtz. Such devices are, by definition, "Helmholtz radiators".

Morbius,

They are not the same thing.

A Helmholtz resonator has a volume of air acting as a spring and a contained subset of it acting as a mass.

This forms a classical mass/spring resonant system; even though the parts are made of air, it's essentially a mechanical system.

But a pipe resonator functions according to its acoustic length; changing the volume doesn't change the resonant freq if the length is the same.

OTOH you can change any of the dimensions and/or volume of a HR and still tune it to the same frequency by varying the mass (vent air or PR).

Morbius,

They are not the same thing.

A Helmholtz resonator has a volume of air acting as a spring and a contained subset of it acting as a mass.

This forms a classical mass/spring resonant system; even though the parts are made of air, it's essentially a mechanical system.

But a pipe resonator functions according to its acoustic length; changing the volume doesn't change the resonant freq if the length is the same.

OTOH you can change any of the dimensions and/or volume of a HR and still tune it to the same frequency by varying the mass (vent air or PR).
noah,

You don't have to explain to me about what a Helmholtz resonator is or isn't;
and how an organ-pipe works!!

The devices that I'm talking about ARE Helmholtz radiators - they are large enough
and with a big enough volume of air so that the resonant frequencies are given by
Helmholtz's resonance condition.

An organ pipe resonator WON'T WORK for the frequencies we are talking about.
The devices I'm referring to fit behind the screen of a commercial theater. The screen
in a commercial theater is about 30 feet wide. If we were to put a pipe resonator
of 30 foot length - then 1/2 the wavelength would be 30 feet and the total wavelength
would be 60 feet. Such a pipe would have a resonance at about 18 Hz. This is about
as low as some of the largest pipe organs with 32 foot stops go. [ There are just a
handful that have 64 foot stops.]

If we want to get down into the single digits of the frequency domain; pipe organ type
resonators would have to be AT LEAST A COUPLE HUNDRED FEET LONG!!!

That's why you can't get down to single digit frequencies with a pipe organ resonantor;
at least NOT in the limited dimension we are talking about.

You HAVE to use something like a "Helmholtz radiator"!!!

One of the nice properties of the TRW is that it is not relying on resonances in a
long dimensioned cavity. The infrasonic frequencies that the TRW puts out have
wavelengths that are hundreds of feet long. Trying to get wavelengths of that
order would mean very BIG devices. The TRW solves this because it is not
relying on a big cavity to get long wavelenths; but rather on the relatively slow
oscillation of the pitch of the TRW fan blades. Another kudo for Bruce's insight.

DAMN it, noah - I'm a PHYSICIST with a doctorate from MIT!!!Yes, and John Kerry served in Vietnam. :rolleyes:

Here's a little hint for you, Morbius. When you feel you have to whip out your credentials, you are perilously close to losing your argument---even if you're right!

Do what I do and let other people do it for you :)

Do what I do and let other people do it for you
Michael,

You're correct - I retract my previous statement.

I was about to pop in a "oh boy... here we go again"

Just a thought greg... Subtlety is king. Always.

Yes, and John Kerry served in Vietnam. :rolleyes:


A political statement Michael?

Nah, it's just the analogy that struck me the quickest---and one that I hope can be appreciated from both sides of the aisle.

Dizzman's point is well made. I honestly doubt that a Ph.D. from MIT earned the respect of his dissertation committee through verbal intimidation. Rather, he had to convince them his work was correct, novel, and meritorious. When Greg brings that particular communication skill to this forum, he is an asset. Heaven knows he knows more about physics than any of us, even if he did learn it from the Stanford of the East! :)

Here is the helmholtz resonator in question...

http://pro.bose.com/images/pro/products/pi_cannon.jpg

Acoustic Cannon. (http://pro.bose.com/pdf/pro/tech_data/accoustic_wave_cannon/td_panaray_awcs.pdf)

I knew somebody was going to post the old wave cannon.

THe first time i saw one of those was (i seem to recall) hanging in the ceiling at a sound company in Vancouver called Western Sound.

Curt???

"You don't have to explain to me about what a Helmholtz resonator is or isn't;
and how an organ-pipe works!!"

You said "I'm talking about pipes whose volumes and lengths are large enough so that the Physics of how they resonate is in occordance with those as described originally by Hermann von Helmholtz. Such devices are, by definition, "Helmholtz radiators".", which belies an understanding that absolute volume/length have no bearing on whether a device is a HR or not.

Tiny ported computer speakers are HR's.

Here is the helmholtz resonator in question...

http://pro.bose.com/images/pro/products/pi_cannon.jpg

Acoustic Cannon. (http://pro.bose.com/pdf/pro/tech_data/accoustic_wave_cannon/td_panaray_awcs.pdf)

Isn't there a rule in the 20k forum never to speak of........ what shall remain unspoken? :p

I have also attempted with modicum success to fold two of these in separate labyrinth/manifolds under a platform uisng instead jbl 18" cones.

the Lake Contour EQ (http://www.dolby.com/professional/live_sound/products/index.html) is a very capable DSP equalizer, with almost extreme attention paid to minimizing distortion. I almost because the high end Lake can by any opinion called 'extreme'. The Lake Contour can act as a speaker crossover... two inputs, six outputs, arrange in a pair of 2 inputs to 3 outputs signal flows. F

In other words, you can take one or both inputs, and cross them over as you like to 3 outputs.

In my case, I take the Lexicon MC12B left/right sub outputs (LFE is turned off, hence it is mixed into the R/L sub outputs respectively), and use the Lake to mono them, then output four signals:
0-20Hz to the TRW
18-40 Hz to the XS
30-100Hz to the Watchdog L
30-100Hz to the Watchdog R

The Lake freq response as well as the MC12B fortunately goes flat down to near DC... no filtering.

Here's a little hint for you, Morbius. When you feel you have to whip out your credentials, you are perilously close to losing your argument---even if you're right!


Dr Grant, as an USC MBA, I fully endorse your public relations strategy!

I'll definitely be looking into the Lake or something similar next year... Thanks for the tips. I bet the sound is amazing!

I almost because the high end Lake can by any opinion called 'extreme'.

:confused: Hehe, you almost what?

What does the Lake retail for? What is the lowest Hz setting on the Lake? I don't thik Meridian 861 correction allows for EQ below 15 Hz or such? I forget the lowest Hz setting on the 861... Any reason you chose the Lexicon over the Meridian 861 v4?

Health Nut---the Lake goes all the way down to "near DC", as tzucc stated earlier. Given what we've seen at his place I can only assume it's usable to 1Hz or even below.

Health Nut,

According to the designer, the Lake is direct coupled, He was not sure if it would pass DC because of software, but seemed to think it would go below 1Hz. The specifications say flat to 2 or 3 Hz depending on I/O configuration.

In a search for ways to EQ extremely low frequencies this was the only unit I could find that did not have a high pass filter around 8Hz or greater. Tzuccs unit will not adjust below 16.53Hz, but I understand there may be a way to get the software to accept lower frequency adjustments. Even so, Mark Seaton can chime in and explain how you can correct even lower frequencies given that limitation.

Tzucc and I have passed about .3Hz through it with no noticeable rolloff. The retail price for the analog in and analog out unit is about $3700.00. The prices go up for digital and additional features. I hope this helps.

brucet

The full up extreme Lake processor is like $5k and it is insanely low distortion... something like 0.007% THD... if true, and I believe it, imagine how hard it is to get a DSP solution with A/D and D/A and processing error to stay down that low in THD... amazing.

I don't think there is any other EQ solution that can match the Lake in terms of accuracy and flexibility, however, my worldview is not advanced on this.

This Lake looks pretty neat. I am confused are there different models or are the Mesa, Contour and Flagship interchangeable?

What does that Lake run?

Out of curiosity; is the Lake able to EQ in the single digits? Also Tzucc is it in the main signal pathway or only the Bass?

Health Nut,

According to the designer, the Lake is direct coupled, He was not sure if it would pass DC because of software, but seemed to think it would go below 1Hz. The specifications say flat to 2 or 3 Hz depending on I/O configuration.

In a search for ways to EQ extremely low frequencies this was the only unit I could find that did not have a high pass filter around 8Hz or greater. Tzuccs unit will not adjust below 16.53Hz, but I understand there may be a way to get the software to accept lower frequency adjustments. Even so, Mark Seaton can chime in and explain how you can correct even lower frequencies given that limitation.

Tzucc and I have passed about .3Hz through it with no noticeable rolloff. The retail price for the analog in and analog out unit is about $3700.00. The prices go up for digital and additional features. I hope this helps.

brucet

Excellent!!! I too always find issues wits subsonic filters. Direct coupled is great!!! Its hard to find good amps that don't have subsonic filters at 8Hz or so.... What amps hae you come across with minimum subsonic filters? Croson Tecnologies uses 2 Hz subsonic just to prevent DC.....

Thaks for the great info. Glad to know a product like this exists!!! Will defintely be interested in picking this up once I get situated into a new house....

Mark Seaton can chime in and explain how you can correct even lower frequencies given that limitation.

My guess is that you add a shelf fitler function at the lowest point... You can't fine tune below that point but you can define what goes on below that.... Would still be nice to be able to have adjustment points into the single digits....

The Lake Contour (think that's the model Bruce has here) has no adjustments in the single digits... what this means is that you can low pass around 16Hz I think it is...which is fine for the TRW... it does well up to 20Hz. The Lake, in my setup, is only in the subwoofer path, going from the Lexicon sub outs to the various subwoofers. The L/C/R/surrounds are straight wire from the Lexicon.

The Lake can be controlled over TCP/IP (yeah, some people get it and have moved on past proprietary serial ports!!) via some software you install on a Windows PC. The software is somewhat cryptic and English, but is quite powerful and exploits the Lake well.

I heard Bruce's demo at CEDIA as well. Cool! Like "The Bland" space is an issue. I am considering a version of "El-Pipo" a 21" transmission line woofer designed by Nelson Pass. I hope to use it on its side behind a 2.35 set up. 13hz is discussed in the article. Easy to build too! Feed it the LFE output?

I heard Bruce's demo at CEDIA as well. Cool! Like "The Bland" space is an issue. I am considering a version of "El-Pipo" a 21" transmission line woofer designed by Nelson Pass. I hope to use it on its side behind a 2.35 set up. 13hz is discussed in the article. Easy to build too! Feed it the LFE output?

Forgot I had a picture

Not even sure why I was visiting the ET site but i got my first look at the Rotary Sub the other day. Have to say that it replaces the Hill Plasmatronics as the most unique speaker design I could ever imagine.

The camera needs more flash. More like a new camera is needed.

Here is the platform.

http://cineramax.com/images/Rorary_Sub_Rear_out.jpg

http://cineramax.com/images/Rorary_Sub_Platform2.jpg

http://cineramax.com/images/helene_side_elevation.jpg

btw, I am hopeful that Transformers will be a possible best demo for the TRWs... saw the movie the other day in a theatre and it seemed like it had lowest bass I'd ever heard in that theatre...so maybe just maybe it might tickle the TRW's into action.

btw, I am hopeful that Transformers will be a possible best demo for the TRWs... saw the movie the other day in a theatre and it seemed like it had lowest bass I'd ever heard in that theatre...so maybe just maybe it might tickle the TRW's into action.

That scene with iron hide doing the flip transform over the girl screaming is the one I hope gets the job done. :-)

I forget which scene it was, but the one with what I perceived to be the lowest bass in the movie was a surprise to me; like the very lowest bass would have been better utilized many other places in the film. Nonetheless, it should be a fun movie for home theatres with good subwoofs.

The Lake can go sub-DC in both correction and EQ...

But then the space/time continuum is torn and you have to listen to Stephen Hawking blather on about how you destroyed everything that is and ever was for slightly better sub-bass performance in your HT.

Still... Probably worth it.

:)

before any of you ask, I was not cranking up the twin TRW subs tonight around 8:05pm... lol. Glad I wasn't in the media room with all the cars above me when the 5.6 hit... my house was rolling pretty good.... MG, you missed a nice quake.

Holy crap is that funny Tony.

That was a gooder! Hey, you are a chicago guy... what is the best chicago pizza around here (not counting zacharys!)

Holy crap is that funny Tony.

That was a gooder! Hey, you are a chicago guy... what is the best chicago pizza around here (not counting zacharys!)

Not as good as being in Chicago but hey, it's California dude: http://www.patxispizza.com/

Just read about it! Yes I imagine I did miss a good one. I never felt a big one while I was in CA, really. I moved out after Loma Prieta. Oh, and I'll add a vote in for Paxti's, it's good stuff.

before any of you ask, I was not cranking up the twin TRW subs tonight around 8:05pm... lol.
tzucc,

Darn!!!! And I though I knew the culprit was our resident "bass master", tzucc and his
TRWs.

Oh well, as Jeffmac points out - it is California.

Just read about it! Yes I imagine I did. I never felt a big one while I was in CA, really.
Michael,

I didn't feel this one AT ALL. Our jam session was just breaking up and I was toting my
guitar out of the room at the time it hit. My fellow jammers were packing up their instruments,
so some were kneeling on the floor - so they were in a stationary, stable state - and they
felt it. The building has alarms that went off.

However, if you were on your feet, and "off balance" due to lugging an outboard weight like
a guitar and case - the quake was too moderate to feel.

Now Loma Prieta - I rode that one out on the top floor of a 7 story concrete building which
is where my office was located. [ That building was later butressed by two large towers
that flank the re-entrant corner of the "L-shaped" building.]

I'm glad my present office is on the 2nd floor of our newer 2-story steel-girder framed
building.

Dizz, if you're here in Bay Area and asking about good Chicago deep dish style pizza, then there is some Chicago themed place on Steven's Creek in Cupertino... it has the word Chicago in the name. It's actually pretty ok.

Never been to 'Patxi's', but I will go try it now.

The only other good deep dish place I've been to in CA is in Moreno Valley, east of LA.

BTW, bought Transformers HD. Video transfer... about a 6/10 (video detail not great), and low frequency audio content, about 5/10. I was expecting much more bass.... there were a few TRW exercising moments when the bots were stomping around with no other side sounds... but overall WOTW still holds the title as the best TRW demo movie so far.

I saw / heard the demo at CEDIA 2006. I stopped by and asked if it was the same at CES and was told it was basically the same so I did not want to waste their time or mine.

While the demo did show some <20 hz signals the connection between the low freq and the video was broken. Some girl walking across the floor and 8hz going off. This to me was not what happens in life. Perhaps it is so cool that the sub went off to you guys hence you had to have it but for me it just was unbelievable and totally got in the way of the movie.

Now if he can tie the sound to the action and have it be believable then you might have something.

Just because you can do a thing does not, in and of it self, justify it being done.

I am sorry that some here are so thin skinned (CINERAMAX and tzucc) , and had to call me a liar and doubt if I can hear or not. Come on boys, Grow up! You can handle the fact the the Emperor has no clothes can't you?

Geez guys get a life. You do not know me or have even spoken with me over the phone.

While soaking your customers may be your way of life, I on the other hand look after mine. I try to justify every penny I spend of theirs. I stand by my first post, this product IMO is looking for an application. Not ready for prime time also IMO.

I would gain far better results by acoustically treating the room which most rooms need desperately. If your customers have done everything they could do at an extremely high level and still want to pound $18K down a rat hole then be my guest. I would have to tell them to hang onto their $$$ and wait for next year. IMO, Which I am Allowed to have even if you Cool-Aide drinkers think otherwise.

ooooookkk. I guess that's that, then.

Hang on. I have to bring my M5 back to the dealership, and spit on them. Then I have to go over to the M-B dealership and set it on fire. It's all wrong, anyway.

Ken, who's post is this you've quoted? I don't remember calling anyone on this forum a liar, ever. Other names maybe, but liar, no.

... but overall WOTW still holds the title as the best TRW demo movie so far.

Have you played Pulse on your system? We used it in our subwoofer mini-shootout and it bottomed many a subwoofer with high-level infrasonics. I haven't seen the movie and heard it wasn't that good, but the one scene with the killer bass is entertaining.

Bruce told me about the University of Hawaii and how they used the TRW technology to simulate earthquakes, for the purposes of testing their earthquake remote sensors.

Here's a link to UoH's summary report (http://bassment.files.wordpress.com/2008/12/king_is59_summary.pdf).

Amazing. They detected the TRW over 3 miles away.... no wonder my neighbors walls were wobbling.

what's AVSforums issue with t i n y u r l ... I can't even put that word in a post without the avsforum software replacing it with a bunch of *'s.

???

I'm still hoping to check out your demo someday... Is there a BASS meeting sometime in Jan/Feb at your place? :)

Tzucc, try http://is.gd (http://is.gd/) instead.