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Old 01-08-2014, 12:04 AM - Thread Starter
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The last paragraph is comedy. Are we all on the same planet? Anyway, really cool 32x15" build with 48 tons of concrete...

Enjoy,

John




Powersoft Amplifier Modules Drive Unique “Wall of Bass” In Austria



"Innovative approach delivers response to as low as 7 Hz
Powersoft D-Cell504 IS high power amplifier modules have been specified to drive a unique “Wall of Bass” in an Austrian nightclub that provides response to as low as 7 Hz.

The newly-reconstructed Club SUB, in the city of Wiener Neustadt, set out to integrate an optimized low-frequency solution, capable of reproducing a wide range of live and DJ-derived music (Drum ‘n’ Bass, Dubstep and Techno) and arts presentations, as well as workshops and theatrical performances.

And since the 300-capacity SUB is located in a heavily populated residential area heavy emphasis needed to be placed on acoustic isolation to avoid noise pollution. These were the challenges faced by project managers Wolfgang Sauter (from pro performance) and Reinhard Nell (from Lambda Labs).

Speaking of the background to the project, Lambda Labs German based director, Steffen Kroschel says, “The owners’ goal was to achieve a similar sound performance as it had in the Grelle Forelle Club in Vienna. Given the concerns of local residents, when Mr. Sauter surveyed the building, with its tube like architecture, the abstract idea of a ‘vibrating wall’ became more logical.”

He contacted Lambda Labs, where Nell supported the concept with simulation data, parameters and measurements, applying his knowledge of high-performance concrete “closed box” enclosures and amping. The drivers were developed especially for this application, going through 10 prototype stages, while the club owners helped with casting the concrete loudspeaker enclosures.

For the rear wall, behind the 6 x 5 meter (approximately 19.7 x 16.4 feet) stage, 400 kg (about 880 pounds) special concrete blocks were cast and set into a 6 x 3 meter (19.7 x 9.8 feet) wall, using 13 tons of heavy concrete and a further 35 tons for the foundation, requiring a monumental effort (shown in photo at right).

“It was extremely difficult to handle these enclosures with small forklift trucks and build the 50 cm deep low frequency absorber,” Kroschel says.“Behind the wall is sand, and under the wall, Mr. Sauter chose material that is used for highway construction.”

Each concrete block serves as loudspeaker enclosure with pressure-resistant rear chamber which implements the optimized impulse response of a “closed-box” design and maximizes the radiation resistance of the woofers through the acoustically hard surface.

A self-enveloped 15-inch loudspeaker was produced and adapted to the unusual demands of this project. The single chassis are designed to act together like one single swinging wall, in a similar principle to a piston in a cylinder.

Kroschel explains the concept further: “A perfect plane wave is created in the interior of the club, which naturally moves along the side walls and doesn’t induce any room modes. The rear of the main floor was converted into a single bass trap to absorb the incoming wave. The SUB thereby achieves an acoustical result that could never be reached even outdoors.”

And as for outside, there is virtually no noise escape, with both Nell and Sauter agreeing that “such an operating range and evenness of the low frequencies is overwhelming.”

But to achieve this optimum performance, every driver needed be powered by its own dedicated amplifier module to take advantage of shortest cable runs, perfect matching power supplies and impedance data. As a long-term partner of Lambda Labs, Nell chose Powersoft to provide amping for the “Wall of Bass,” while Lambda Labs supported the installation with items like amplifier mounting frames.

“As we have been using Powersoft amplifiers in our regular self-powered loudspeakers for four years, it was obvious to choose the company again for this project as we have a lot of experience with their modules, such as the Digimod 1500, which we use successfully in our subwoofer product MF-15A and our full range enclosure TX-3A,” Kroschel notes.

“Their amplifiers deliver stable power also in the low frequency range, are small and lightweight, and fulfill most of our demands regarding sound quality,” he continues. “For the project, we used the D-Cell, because it is very compact and still delivers plenty of power.”

The 32 Lambda Labs OEM CX 15-inch ultra-long excursion drivers, with ± 25mm linear excursion capability set in housings made from special concrete. Each is driven by 800-watt amplifying modules, with the maximum desired SPL reached at an excursion of only ±3mm. Therefore, the “Wall of Bass” manages with only 500-watt peak music power during operation, providing great energy efficiency.

Via the 2-channel 32 D-Cell504 IS amp modules, Powersoft was able to deliver 25,600 watts of amplifier power. In addition, special mid-high loudspeakers generate a cylinder wave for longer throw and less room reflections while the DJ reference sound is provided by CX-1A and CX-3A self-powered monitors with Powersoft D-Cell modules.

Available in both 2-channel and an incredibly compact 4-channel model with two amp units, D-Cell504 IS will power 2-way loudspeakers with up to 2 x 350 watts into 4 ohms or 1 x 700 watts in bridge mode at 8 ohms – or even 3-way systems with up to 700 watts on the low end.

Performance is enhanced via PFC power supply, allowing error proof operation, and Class D output stage, also available with DSP on board.

Integrated within an elegant aluminum heatsink panel, the D-Cell504 IS provides an interface panel with input volume potentiometer, double XLR for mono input and link out or stereo input operation, four LED for Limit, Clip, Signal and Ready signalling, with a 4-LED preset selection button to show the preset in use.

Easy access to the DSP mounted on board, is further facilitated via remote control capabilities provided by Powersoft’s proprietary Armonía Pro Audio Suite.

“The data we measured melts in one’s mouth,” says Nell. “The sound pressure level is beyond 140 dB and absolutely equal at any point in the room (not that anyone would need such sound pressure levels). And you don’t have the possibility to feel 7 Hz throughout your whole body.”

Summing up, Kroschel says that everyone who has played through the system has been impressed.

“For some it has changed their awareness of music,” he concludes. “Although we have not been able to find movie soundtracks with lower frequency response than 20 Hz, during our live presentations of the ‘Wall of Bass’, we play an original recording of a Challenger rocket launch, to give a natural idea of the breathtaking force. Another show element was to generate some sine waves down to 7 Hz, demonstrating this outstanding response by also making the acoustic waves visible with smoke.”

http://www.prosoundweb.com/site/2013/12/16/






More or less same article, but slightly different content from PowerSoft press release/website:

Florence, Italy, December 2013 – Powersoft D-Cell504 IS high power amplifier modules have been specified to drive a unique 'Wall of Bass' in an Austrian nightclub — as low as 7Hz.

The newly-reconstructed Club SUB, in the city of Wiener Neustadt, set out to integrate a perfect low frequency solution, capable of reproducing a wide range of live and DJ-derived music (Drum 'n' Bass, Dubstep and Techno) and arts presentations, as well as workshops and theatrical performance in a completely revolutionary way.

And since the 300-capacity SUB is located in a heavily populated residential area heavy emphasis needed to be placed on acoustic isolation to avoid noise pollution.

Project managers, Wolfgang Sauter (from pro performance) and Reinhard Nell (from Lambda Labs), were equal to the challenge.

Speaking of the background to the project, Lambda Labs German based director, Steffen Kroschel, said, "The owners' goal was to achieve a similar sound performance as it had in the Grelle Forelle Club in Vienna. Given the concerns of local residents, when Mr. Sauter surveyed the building, with its tube like architecture, the abstract idea of a 'vibrating wall' became more logical."

He contacted Lambda Labs where Richard Nell supported the concept with simulation data, parameters and measurements — applying his knowledge of high performance concrete 'closed box' enclosures and amping. The drivers were developed especially for this application, going through 10 prototype stages, while the club owners helped with casting the concrete loudspeaker enclosures.

For the rear wall, behind the 6 x 5 meter stage, 400 kg special concrete blocks were cast and set into a 6 x 3 metre wall, using 13 tons of heavy concrete and a further 35 tons for the foundation — requiring a monumental effort. "It was extremely difficult to handle these enclosures with small forklift trucks and build the 50 cm deep low frequency absorber," recalls Steffen. "Behind the wall is sand, and under the wall, Mr. Sauter chose material that is used for highway construction."

Each concrete block serves as loudspeaker enclosure with pressure-resistant rear chamber which implements the perfect impulse response of a 'closed-box' design and maximizes the radiation resistance of the woofers through the acoustically hard surface. A self-enveloped 15" speaker was produced and adapted to the unusual demands of this project. The single chassis are designed to act together like one single swinging wall — in a similar principle to a piston in a cylinder.

Steffen explains the concept further. "A perfect plane wave is created in the interior of the club, which naturally moves along the side walls and doesn't induce any room modes. The rear of the main floor was converted into a single bass trap to absorb the incoming wave. The SUB thereby achieves an acoustical result that could never be reached even outdoors."

And as for outside, there is virtually no noise escape and both Reinhard Nell and Wolfgang Sauter, agree that "such an operating range and evenness of the low frequencies is overwhelming".

But to achieve this optimum performance, every driver needed be powered by its own dedicated amplifier module to take advantage of shortest cable runs, perfect matching power supplies and impedance data. As a long-term partner of Lambda Labs, Reinhard Nell chose Powersoft to provide amping for the 'Wall of Bass' while Lambda Labs supported the installation with items like amplifier mounting frames.

"As we have been using Powersoft amplifiers in our regular self-powered loudspeakers for four years, it was obvious to choose the company again for this project as we have a lot of experience with their modules, such as the Digimod 1500, which we use successfully in our subwoofer product MF-15A and our full range enclosure TX-3A," continues Steffen.

"Their amplifiers deliver stable power also in the low frequency range, are small and lightweight and fulfill most of our demands regarding sound quality. For the project, we used the D-Cell, because it is very compact and still delivers plenty of power.

The 32 Lambda Labs OEM CX 15" ultra-long excursion drivers, with ± 25mm linear excursion capability set in housings made from special concrete. Each is driven by 800 Watt amplifying modules, with the maximum desired SPL reached at an excursion of only ±3mm. Therefore the 'Wall of Bass manages with only 500 Watt peak music power during operation, which sets new standards of energy efficiency.

Via their 2-channel 32 D-Cell504 IS amp modules, Powersoft were able to deliver 25,600 watts amping power, including 4in voice coil with custom made venting system using hardened membrane.

In addition, special mid-high speakers generate a cylinder wave for longer throw and less room reflections while the DJ reference sound is provided by CX-1A and CX-3A self-powered monitors with Powersoft D-Cell modules.

Available in both 2-channel and an incredibly compact 4-channel model with two amp units, D-Cell504 IS will power 2-way loudspeakers with up to 2 x 350W into 4Ω or 1 x 700W in bridge mode at 8Ω – or even 3-way systems with up to 700W on the low end.

Performance is enhanced via PFC power supply, allowing error proof operation, and premium quality Class D output stage, also available with DSP on board.

Integrated within an elegant aluminum heatsink panel, the D-Cell504 IS provides an interface panel with input volume potentiometer, double XLR for mono input and link out or stereo input operation, four LED for Limit, Clip, Signal and Ready signalling, with a four-LED preset selection button to show the preset in use. Easy access to the DSP mounted on board, is further facilitated via remote control capabilities provided by Powersoft's proprietary Armonía Pro Audio Suite™.

"The data we measured melts in one's mouth," summarised Reinhard Nell. "The sound pressure level is beyond 140dB and absolutely equal at any point in the room (not that anyone would need such sound pressure levels). And you don't have the possibility to feel 7Hz throughout your whole body every day."

Summing up, Steffen Kroschel says that everyone who has played through the system has been hugely impressed. "For some it has changed their awareness of music."

"Although we have not been able to find movie soundtracks with lower frequency response than 20 Hz, during our live presentations of the 'Wall of Bass', we play an original recording of a Challenger rocket launch, to give a natural idea of the breathtaking force. Another show element was to generate some sine waves down to 7Hz, demonstrating this outstanding response by also making the acoustic waves visible with smoke."

Needless to say, the installation has attracted huge interest, from cinema exhibitors to club owners. "Some people think this has to be very expensive — but it costs the same or less than other high-end installations, depending on room size and situations.

"If the 'Wall of Bass' is capable of being integrated, due to the building's architecture, the installation will result in absolutely perfect performance which can be adjusted to non concrete solutions. We now plan to realise some international projects to show the world what can be done with sound."

http://www.powersoft-audio.com/en/news/news-archive/733-powersoft-d-cell-504-is-modules-drive-unique-wall-of-bass.html


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Old 01-08-2014, 12:39 AM
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Wow, perfectly executed SBA, Powersoft amps, loads of power and a DSP, with concrete enclosures.
Definitely want to visit Austria..

Found this too.

tongue.gif
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Old 01-08-2014, 12:51 AM - Thread Starter
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nice.

really nice.

better than the op nice!

i thought the article was great, but the video really explains (more or less) the idea. everybody should watch that one for sure.

...and if anybody has any random information on the rear wall absorber, please kick it into the mix.

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Old 01-08-2014, 01:05 AM
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Perfect.
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Old 01-08-2014, 01:16 AM
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Quote:
Originally Posted by LTD02 View Post


eek.gifeek.gifeek.gifeek.gifeek.gifeek.gif
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Old 01-08-2014, 01:17 AM
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Old 01-08-2014, 01:19 AM
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Quote:
Originally Posted by LTD02 View Post

nice.

really nice.

better than the op nice!

i thought the article was great, but the video really explains (more or less) the idea. everybody should watch that one for sure.

...and if anybody has any random information on the rear wall absorber, please kick it into the mix.

For those who didn't see Folgot's thread about a single bass array (SBA), I agree, this video sums it up perfectly. Hell, it even made more sense to me and I read the whole thing.
Anyone building a dedicated theater room from scratch should really consider a SBA. I know I will when I get my own place.

I tried finding more information on the absorber, but so far all I see is that its 50CM and made of " the material used in highways " . Hmmm.
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Old 01-08-2014, 01:58 AM - Thread Starter
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op updated with additional release from powersoft site. includes this nugget:

"The 32 Lambda Labs OEM CX 15" ultra-long excursion drivers, with ± 25mm linear excursion capability set in housings made from special concrete. Each is driven by 800 Watt amplifying modules, with the maximum desired SPL reached at an excursion of only ±3mm. Therefore the 'Wall of Bass manages with only 500 Watt peak music power during operation, which sets new standards of energy efficiency."

i think that is somewhere around 130db btw.

:-)

interestingly, with the concrete enclosures and the absorber at the other end of the room, no sound leaves the building in those directions, so not only is it loud as hell, but also quiet as hell.

not sure what transmission loss for something like this would be at the wall/ceiling/floor.

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Old 01-08-2014, 04:28 AM
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Quote:
Originally Posted by Thatsnasty View Post

For those who didn't see Folgot's thread about a single bass array (SBA), I agree, this video sums it up perfectly. Hell, it even made more sense to me and I read the whole thing.
Anyone building a dedicated theater room from scratch should really consider a SBA. I know I will when I get my own place.

I tried finding more information on the absorber, but so far all I see is that its 50CM and made of " the material used in highways " . Hmmm.

I vaguely remember reading that thread about the SBA, and am considering doing something like that myself. Is the original idea for the SBA a pair of drivers that are all equal distance from the ceiling, floor, and each side wall? Are these drivers to be mounted in enclosures that are hung on the wall, or are they am infinite baffle design?

If I could possibly make some enclosures to hold the drivers and not have to resort to an IB and instead have the enclosures mounted in a SBA setup on the front wall, then I would likely give this a try!

How does the Dayton HO18 and/or the SI 18HT work in a SBA? What kind of enclosure specs would be necessary and how/where should the enclosures be mounted?

I am treating the back wall with lots of Safe-N-Sound to kill the reflection off the back wall, FYI.
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Old 01-08-2014, 07:09 AM
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I want.
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Old 01-08-2014, 07:53 AM
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Quote:
“For some it has changed their awareness of music,” he concludes. “Although we have not been able to find movie soundtracks with lower frequency response than 20 Hz, during our live presentations of the ‘Wall of Bass’, we play an original recording of a Challenger rocket launch, to give a natural idea of the breathtaking force. Another show element was to generate some sine waves down to 7 Hz, demonstrating this outstanding response by also making the acoustic waves visible with smoke.”


ummm look harder, or simply open your eyes
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Old 01-08-2014, 08:14 AM
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maximum desired SPL reached at an excursion of only ±3mm.....


Crank those puppies up. They're being sissies.

I would have loved for the second video to give some perspective of the impact.
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Old 01-08-2014, 08:58 AM
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+-3mm, because they've not yet taxed the rig with the deep stuff.

+1 on the SBA stuff, but remember, studio design has employed similar pitch and catch methods for a long time. Certainly not a planar wave, like this, PNW's, or Nils, but addressing front-to-back via massive and effective rear boundary treatment is not new.

Addressing side-to-side via careful placement (selective mode cancelation) and treatment as icing, leaves only height, which can be designed in.


Thanks for the heads up on this club, very cool.

I'm thinking the tough demanding effects could hit the limits of this thing, no? Not music, but soundtrack effects attempting to cover that many cubes, brutal task.

The club could've employed an IB, with equal sized backspace club area on other side with it's own tops, had twice the club goers capacity within the proper enjoyable distance from the array.

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Old 01-08-2014, 09:14 AM
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Old 01-08-2014, 09:18 AM
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Quote:
Originally Posted by Thatsnasty View Post

Wow, perfectly executed SBA, Powersoft amps, loads of power and a DSP, with concrete enclosures.
Definitely want to visit Austria..

Found this too.

tongue.gif


Just viewed this vid, this should be required viewing for all enthusiasts, ... well done.

Thanks for posting.

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Old 01-08-2014, 09:26 AM
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LTD,

There are so many red flags in this article, it would be easier to pick out the actual facts than the baloney.
Quote:
placed on acoustic isolation to avoid noise pollution

Ummm… dual opposed vs 200 tons of concrete?
Quote:
the abstract idea of a 'vibrating wall' became more logical

A vibrating wall of concrete? Oh, they mean the drivers. :roll eyes:
Quote:
The drivers were developed especially for this application, going through 10 prototype stages

Guess they never heard of a sealed sub before. 10 prototype stages. Wonder what the first 9 stages were?
Quote:
Each concrete block serves as loudspeaker enclosure with pressure-resistant rear chamber which implements the perfect impulse response of a 'closed-box' design and maximizes the radiation resistance of the woofers through the acoustically hard surface.

"Pressure resistant" rear chamber, "perfect impulse response", "radiation resistance"… I guess the drivers cone is unobtainium?
Quote:
A perfect plane wave is created in the interior of the club

A perfect plane wave? That would mean no boundary gain. As Nils showed and commented on:

a7e00a4bda63713874b52b368860381a.gif
Quote:
Originally Posted by FoLLgoTT View Post


A time ago I used closed boxes. But since there is no room gain with a DBA (you practically get free air conditions) I had to use a +12 dB shelving filter in the lower end. This dropped max SPL a lot, because of high cone excursion. So right now all subwoofers are vented designs.
Quote:
"The data we measured melts in one's mouth," summarised Reinhard Nell. "The sound pressure level is beyond 140dB and absolutely equal at any point in the room (not that anyone would need such sound pressure levels). And you don't have the possibility to feel 7Hz throughout your whole body every day."
Quote:
maximum desired SPL reached at an excursion of only ±3mm

So, since the data melted in their mouths, it's no longer available? I'm calling BS on the 140dB @ 7 Hz. with 3 mm of excursion… or any excursion for that matter. As Nils points out, you need a signal chain that's flat to 7 Hz, a .707 naked response (not impossible, but doubtful in the tiny box) and a 12dB boost shelf to get flat to 7 Hz with zero boundary gain. To reach 140dB @ 7 Hz, assuming all other conditions have been met, they're about 30KW short on amp and about 200 mm short on X-max.

OTOH, using room gain typically realized in a very transmission-loss-resistant room, they are throwing away 20dB of free lunch gain at 7 Hz. They would need no absorber at that frequency and the response at 7 Hz would be the same everywhere in the room.

They should stick to the typical pro sound metric of 30 Hz on the low end and then the whole story sounds much more credible, but not very interesting and overly expensive.
Quote:
Although we have not been able to find movie soundtracks with lower frequency response than 20 Hz, during our live presentations of the 'Wall of Bass'

Bwahahahaha… LTD, send them a copy of WOTW and include a note marking the scenes they should audition at 140dB. Make sure you tell them to film the results in Slo-Mo for the enjoyment factor. biggrin.gif
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Old 01-08-2014, 10:36 AM
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^^^^^^^

This sounds like a case of the PR people not having a real clue about audio and having to generate material. They latch on to "what sounds cool" and if does sound cool they make it sound cool even if it is technically wrong. Very typical in any industry.

I must be guilty because people say I am guilty because they chose to call me guilty because they refuse to see the truth. Much easier to be part of the mob..
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Old 01-08-2014, 10:43 AM
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Hi Dave,
I think I have to clarify a few things. smile.gif
Quote:
Originally Posted by bossobass View Post

A perfect plane wave? That would mean no boundary gain. As Nils showed and commented on:

1. This statement concerned only the cancellation of the plane wave by the rear array of a Double Bass Array.

2. I was wrong! A DBA indeed has room gain as any other subwoofer system does. I verified this behavior when I experimented in my empty cellar room. I'm sorry that this old statement still confuses people.


I had contact with Reinhard Nell a few months ago when I was planning my own system. The WOB uses the exact same concept as I did in my room (in fact I knew the concept before I knew the WOB). There is an array of subwoofers with a certain distance to each other and a big absorber on the rear wall. The differences between the WOB and my system are:

- much bigger room
- much more displacement (and much higher grid density)
- different absorber (porous + metal pane)

According to Reinhard they had problems with the mechanical load of the drivers, since the boxes are small and they are stacked heavily. In a stacked evironment the radiation resistance* is higher than in a usual setup. It can be compared with horn loading. The force on the cones increases. So the voice coil's former material and the glue between former and membran become important factors. And don't forget that it is not a home theater, but a disco. So the RMS power is very different in this application.

Taking the bigger room into account the WOB still has 7 times more displacement than I have. This gives about 122 dB @ 7 Hz under half space conditions. With +18 dB of room gain at this frequency 140 dB may be possible (I have that gain at 11 Hz). But I don't think with only +/- 3 mm of excursion. You are right that this is just not possible! In fact they need this excursion at the maximum desired SPL (with an unknown bandwidth) and not the maximum possible SPL. At least that is my understanding of this statement. smile.gif


*I think the term radiation resistance is much more often used in german than in english. Is it correct in english at all?
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Old 01-08-2014, 11:38 AM
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Hi Nils,

I was going to ask you to define the term "radiation resistance". smile.gif

It has no application to the subject that I can figure out. Do they mean "loading", as in the atmosphere, on the front side? Maybe they mean "Air Spring" on the back side, inside the enclosure?

It's likely they are referring to loading, so they required more motor strength to drive the cones to 3 mm (just kidding), er, full X-max in the outward 1/2 of the excursion cycle.

If there's room gain, there is no "perfect plane wave that moves along the walls". If there's a perfect plane wave, there's not nearly the output below 20 Hz they claim. The difference between 122dB and 140dB is 64 times. And, as you've noted, 3 mm of excursion is magnitudes off from reality.

2' of absorber at the opposite end of the room is irrelevant. With a perfect plane wave (no such thing in a room, BTW. It's a nice theory, but I never bought it in real life. At the VERY least, the leading edge is spherical.), the absorber is ineffective below a cut off frequency that's far above 7 Hz.

They have 130L of displacement. 16 of the LMS Ultra 18s will easily outgun their system and, no prototype stages necessary. IMO, using the room is a far more efficient method for achieving <20 Hz reproduction with far less non-linearities.

I would love to see some of the "melts-in-your-mouth" data. Do you know of any available? Even a FR taken from several places in the room might verify "some" of the claims made. wink.gif
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Old 01-08-2014, 12:27 PM
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Dave,
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Originally Posted by bossobass View Post

I was going to ask you to define the term "radiation resistance". smile.gif

I don't know if I found the correct term in english. It means the same as acoustic impedance. Here is an article about horns that uses this term. I don't know why the other term is used so often in german (and maybe translated incorrectly to english).

It defines how effective a moving cone creates sound pressure and is frequency dependant. A horn transforms the acoustic impedance to gain effectivity in that way that it has a larger opening area then the driver itself. Stacking has a similar effect. Generelly big cones increases the acoustic impedance.
Quote:
With a perfect plane wave (no such thing in a room, BTW. It's a nice theory, but I never bought it in real life. At the VERY least, the leading edge is spherical.), the absorber is ineffective below a cut off frequency that's far above 7 Hz.

According to this site the room length is 16,5 m. That means the first length mode is located at 10 Hz. Usually a partially damped mode effects a wider frequency range (lower Q). So I assume that 7 Hz is still noticeable increased by this mode.



Quote:
I would love to see some of the "melts-in-your-mouth" data. Do you know of any available? Even a FR taken from several places in the room might verify "some" of the claims made. wink.gif

I've never seen any. And I highly doubt that FR is the same everywhere in the room. Considering that the room is open and thus not completely rectangular this would be too good to be true. wink.gif
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Old 01-08-2014, 01:57 PM
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I have to agree that this is an amazing setup = Thanks for posting John. It's great that high SPL bass is getting more and more into the mainstream. I recall a club system in the LOUDSPEAKERS book that used a bass horn to get to 20Hz, also using a concrete structure.

These statements are not linked. The maximum desired SPL is not necessarily 140dB. I agree that there are quite a few anomalies and thanks for pointing them out Bosso.

Quote:
"The data we measured melts in one's mouth," summarised Reinhard Nell. "The sound pressure level is beyond 140dB and absolutely equal at any point in the room (not that anyone would need such sound pressure levels). And you don't have the possibility to feel 7Hz throughout your whole body every day."
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"maximum desired SPL reached at an excursion of only ±3mm"

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Old 01-08-2014, 02:08 PM
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10 iterations of a driver for a sealed enclosure...... 22mm of xmax when they "only need 3".

I hope the LE is low as all get out (eh LTD?)
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Old 01-08-2014, 03:32 PM
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How much separation (distance in feet pls) do I need, If want a pair of these for stereo subs ? I would be using the fronts from a Bose Lifestyle series smile.gif
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Old 01-08-2014, 03:49 PM - Thread Starter
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bb, i suppose that we can tackle all those issues one at a time...at some point. :-)

a plane wave tube is the ultimate expression of room gain and is a rather special situation. since all the radiation sums and is focused in one direction, the amount of room gain is very large.

here "room gain" is simply the increase in spl resulting from all the sound power being radiated in one direction down the "tube" instead of in all directions, like a subwoofer in 2pi space (as in an open field).

every sub in the array has a reflection. all of those virtual sources sum as though they are *actual subs*. what you see is not what is heard. what is heard is an infinitely tall and wide wall of subwoofers. more like this:



the efficiency of this system is unlike anything that you are familiar with, pushing into the limit of transforming electrical power into acoustical power. i suspect that this is why the rear chambers are "so small" (big motors in the drivers easily overcome the air spring of the small enclosures) and all the talk about radiation resistance. I'm not 100% on this, but each driver in "the wall" appears to cover about 1/2 sq meter of area. 50hz 4pi (anechoic) sensitivity at 1m for a 15" driver is in the ballpark of 82db 1w1m. so the increase in sensitivity 'per driver' is 20*log(4pi sq m / 1/2 sq m), or about +28db. that would give ~110db 1w sensitivity everywhere in the room at 50hz. interestingly, they mention 500 watts as getting them to their target level. i wouldn't be surprised if their target was >130db and 500 w applied to a 110db sensitive system gets you >130db.** anyway, still not sure about that calculation.

additionally, in a plane wave tube there is no loss in spl with distance. it is the same everywhere in the room (assuming your rear absorber is working! and except for the minor loss to friction as the waves move along the walls/ceiling/floor and over and around objects (and people for that matter).)

** I'm not sure what reference sensitivity should be used for something like this though, 1m 4pi, or something else?

...

radiation resistance:

zheka likes this.

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Old 01-08-2014, 03:57 PM - Thread Starter
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"2' of absorber at the opposite end of the room is irrelevant."

depends on how it works. if it is working on a mass principal, it could very well be absorbing the primary length resonance. more details are needed.

" With a perfect plane wave (no such thing in a room, BTW. It's a nice theory, but I never bought it in real life. At the VERY least, the leading edge is spherical.)"

there are 32 leading edge spheres, summed and you don't get a large sphere, you get a plane. considering the reflected virtual sources, the number of sources increases to infinity and you get a perfect plane wave. its not that the wave is actually a plane, just that an infinite number of leading edge spheres perfectively recreate a plane. same principal that line arrays work on, but in 2 dimensions instead of one.

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Old 01-08-2014, 04:05 PM - Thread Starter
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"placed on acoustic isolation to avoid noise pollution"

"Ummm… dual opposed vs 200 tons of concrete?"

i see your point. two issues here.

you are saying that dual opposed helps contain sound because the cabs themselves don't vibrate and that helps keep sound in the room.

in the wall of bass, the concrete is to keep the sound in the room which is radiating off the backside of the 32 x 15" drivers. it can't be an absorber like the rear wall, so it has to be dead with weight, which it is.

32 x 15" drivers in mini-sealed-sonotubes would still radiate quite a bit of noise through the structure even though the cabs themselves would be inert.



.

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Old 01-08-2014, 04:08 PM - Thread Starter
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"10 iterations of a driver for a sealed enclosure...... 22mm of xmax when they "only need 3".

I hope the LE is low as all get out (eh LTD?)"

how would i know? :-) maybe that is one thing they were working on during those 10 iterations!

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Old 01-08-2014, 05:07 PM
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The sensitivity of the system is probably around 104-105dB 1W/1M.
Quote:
Originally Posted by LTD02 View Post

"2' of absorber at the opposite end of the room is irrelevant."

depends on how it works. if it is working on a mass principal, it could very well be absorbing the primary length resonance. more details are needed.

" With a perfect plane wave (no such thing in a room, BTW. It's a nice theory, but I never bought it in real life. At the VERY least, the leading edge is spherical.)"

there are 32 leading edge spheres, summed and you don't get a large sphere, you get a plane. considering the reflected virtual sources, the number of sources increases to infinity and you get a perfect plane wave. its not that the wave is actually a plane, just that an infinite number of leading edge spheres perfectively recreate a plane. same principal that line arrays work on, but in 2 dimensions instead of one.

I don't agree with the theoretical tube story. The leading edge is spherical and there are reflections, as Nils has discovered, and thus, revised his theoretical understanding. The room is far from a tube and, even in a tube with an end there are reflections. A plane wave is only theoretical, just as a line is in in math said to be one-dimensional, length only. If the line is not 3D, LxHxD, it is invisible and, therefore, not a line, but a theoretical line.

But, back to the articles claims; suppose it is a "perfect plane wave", then there is no room gain and thus, @ 7 Hz, sensitivity drops and excursion and power requirements increase.

Theory is a circle jerk, show me the measurements. smile.gif
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Old 01-08-2014, 05:14 PM
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Quote:
Originally Posted by LTD02 View Post

"placed on acoustic isolation to avoid noise pollution"

"Ummm… dual opposed vs 200 tons of concrete?"

i see your point. two issues here.

you are saying that dual opposed helps contain sound because the cabs themselves don't vibrate and that helps keep sound in the room.

in the wall of bass, the concrete is to keep the sound in the room which is radiating off the backside of the 32 x 15" drivers. it can't be an absorber like the rear wall, so it has to be dead with weight, which it is.

32 x 15" drivers in mini-sealed-sonotubes would still radiate quite a bit of noise through the structure even though the cabs themselves would be inert.



.

You have to admit that tons of concrete to assure an inert wall being followed by the description "a vibrating wall" is a bit of a chuckle.

One walls concrete transmission loss barrier is a roof, entry and adjacent walls transmission loss open door.

The main problem in planning a wall with 32x15" long throws is indeed that it will be a vibrating wall. Dual opposed config eliminates that problem. Using concrete for a sub enclosure is not a new concept, but it is an unnecessary one.
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Old 01-08-2014, 05:17 PM
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Quote:
Originally Posted by LTD02 View Post

"10 iterations of a driver for a sealed enclosure...... 22mm of xmax when they "only need 3".

I hope the LE is low as all get out (eh LTD?)"

how would i know? :-) maybe that is one thing they were working on during those 10 iterations!

thats what I was implying (I was hoping the same thing).
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