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[Nathan Riddle]

Nathan,

The "math" to determine the effective pattern control of a CDL array is a bit more complicated than a few 1/4 wave calculations.

As in any line array, each addition of another element affects the pattern control.

Keele's predictions for 1 to 6 boxes (attached) are probably "close enough for rock & roll"  .

Art

Well that's why I'm here, to learn

Is the 'box count' the same as driver count?
Does the box/driver predictions take into account physical size?

[Art Welter]

Well that's why I'm here, to learn

Is the 'box count' the same as driver count?
Does the box/driver predictions take into account physical size?

Each box has 8 HF drivers in a curved array, the predictions taking into account physical size and shading.

You can read all about it:

"Based on the Constant-Directivity Two-Way Loudspeaker System design presented at the 143rd AES Convention in New York by Hugh Sarvis and Don Keele"

https://pae-web.presonusmusic.com/downloads/products/pdf/AES_143__eBrief_188_V1-_Keele_Sarvis_-_Design_and_Implementation_of_a_CD_Two-Way_12__Woofer_Wedge_Loudspeaker_System.pdf

[Nathan Riddle]

Each box has 8 HF drivers in a curved array, the predictions taking into account physical size and shading.

You can read all about it:

"Based on the Constant-Directivity Two-Way Loudspeaker System design presented at the 143rd AES Convention in New York by Hugh Sarvis and Don Keele"

https://pae-web.presonusmusic.com/downloads/products/pdf/AES_143__eBrief_188_V1-_Keele_Sarvis_-_Design_and_Implementation_of_a_CD_Two-Way_12__Woofer_Wedge_Loudspeaker_System.pdf

Wow, that is literally the paper on how they built the unit. It performs better than I expected. Nice job Presonus.

I wasn't far off with my 3kHz calculation though.

[John L Nobile]

Each box has 8 HF drivers in a curved array, the predictions taking into account physical size and shading.

You can read all about it:

"Based on the Constant-Directivity Two-Way Loudspeaker System design presented at the 143rd AES Convention in New York by Hugh Sarvis and Don Keele"

https://pae-web.presonusmusic.com/downloads/products/pdf/AES_143__eBrief_188_V1-_Keele_Sarvis_-_Design_and_Implementation_of_a_CD_Two-Way_12__Woofer_Wedge_Loudspeaker_System.pdf

Very interesting. I didn't realize that this was where Presonus got the inspiration. Thanks for clearing that up for me Art. My head stopped spinning.

[Chris Grimshaw]

... and in the end, we're still waving bits of cardboard around with magnets.

Chris

[Stephen Kirby]

There's still a long way to go, especially in SR.  Look at how much bottom and level comes out of those little bluetooth speakers.  Apple has a patent on a system for capacitively sensing the position of the diaphragm and applying various limiting schemes to keep it within excursion limits.  Thus maximizing the amount of level you can get out of a small device.  Such amazing things you can do with computers these days.

[Rory Buszka]

Wow, that is literally the paper on how they built the unit. It performs better than I expected. Nice job Presonus.

I wasn't far off with my 3kHz calculation though.

It is clever how Don Keele and Hugh Sarvis (WorxAudio) developed this concept to incorporate the only unclaimed embodiment of a Constant-Beamwidth Transducer (CBT) array in Keele's earlier patent US7826622B2 by placing the attenuation circuit upstream of individual amplifier sections that subdivide the circular-arc array of wideband drivers. Otherwise they might expect to have infringed on the earlier CBT patent. Directivity and level shaded arrays of line array cabinets have already been proposed, where any level shading is provided upstream of the power amplifier rather than being integral to the speaker. The Keele patent claims an array speaker with level shading networks provided between the input terminals and the speaker itself, rather than ahead of an integrated power amplifier, according to my reading.

In the earliest presentation I attended where Don Keele and Marshall Kay presented the curved CBT36 speaker, Don commented that after spending his entire career working on improvements to horn technology, he now saw small drivers as being capable enough to work together in an array that would be more compact than a horn and replace horns in many applications. The circular-arc CBT in particular is intended to replace a single large horn in systems where wide horizontal dispersion is needed, and the vertical coverage angle can be subtended between the extents of the circular arc array.

The Bose F1 812 is an example of another system where a traditional high frequency horn is replaced by twelve (Tymphany-made) 2-1/2" cone drivers, and a 12" driver is placed behind the array. Calling this a "coaxial" approach is not strictly accurate because the system is not axisymmetric. In my own hearing of the Bose F1 812 system at a WFX speaker demo event, I found the array of full-range drivers to have a "softer" sound characteristic, probably due to some power compression and additional mechanical compression (driver break-up), but in certain applications like a medium-throw auditorium installation, this characteristic could be desirable to avoid sounding "piercing", but these cabinets should present no great risk to the medium format line arrays of the world. I think it would be reasonable to expect the Presonus array to have a similar characteristic. For installation purposes, I would have hoped for a full-face grille rather than the partially perforated panels on either side of the central array for a cleaner look, but there is probably time for Presonus to revise their product in a later version.

[Scott Holtzman]

... and in the end, we're still waving bits of cardboard around with magnets.

Chris

and Kevlar

[Marjan Milosevic]

Dynacord did that decades ago.

[Marjan Milosevic]

JBL too

[ProSoundWeb Community]