New Speaker-fi: Audio Artistry CBT36

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New Speaker-fi: Audio Artistry CBT36

Postby amb » July 18th, 2012, 3:52 am

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Although I think my current DIY θ19 speaker system sounds great, I've nevertheless been on the lookout for a new speaker project for quite some time. I wanted something "statement level" in design and execution that would do the β24 power amp justice. I've thought about conventional dynamic speakers, electrostatic panels, ribbons, air-motion transformers, line source arrays, etc., but not a single one stood out as a clear and compelling solution. That is, until recently.

Don Keele, who is a well-known authority in the speaker design world (I've been following his work since the 1970s) and Marshall Kay designed a new speaker called the Audio Artistry CBT36. "CBT" stands for Constant Beamwidth Transducer and is implemented as a curved line array. However, it is far from being just another line array. The name "CBT" suggests that it has the very desirable trait of virtually no frequency response change anywhere you are in the listening area. The drivers in the array are "Legendre shaded" in that they do not all play at the same volume, which is a part of design. But I am getting a little ahead of myself here...

The CBT36 is a very unique system, backed up by a lot of science and research. Even though I've not auditioned them, I trust the designers. Comments by Stereophile's John Atkinson (calling it "one of the best sounds at the 2011 RMAF") as well as very positive feedback from others who had auditioned them makes it confidence-inspiring, not to mention the ample technical details and measurement results published by Keele.

The CBT36 is currently offered as a DIY kit via Parts Express, which includes the precision CNC'ed cabinets and bases (unfinished), 36 bass/mid drivers, 144 tweeters, sealing gaskets, "shading" resistors, wires, connectors, fiber-fill, comprehensive assembly manual and documentation, and even some solder. The current price is $1980 a pair, which, given what you're getting, is an incredible value. There are rumours that Audio Artistry will be offering finished CBT36s in the future for some $9000 a pair.

One thing to note, this system must be bi-amped. There is neither a passive crossover network, nor is one recommended. The designers provide setup instructions for the Behringer DCX2496 digital electronic crossover, and separate power amps should be used for the bass/mid and tweeter drivers.

I think the design is a great blend of the benefits of a point source and a line source, and IMHO superior to a planar or curved
planar (e.g., Martin Logan). The CBT36 will also be very room-acoustics friendly since its horizontal and vertical dispersion does not vary with frequency above the bass range. It's said to provide incredible soundstage and not only at one sweet spot, but just about anywhere in the listening space.

The large number of drivers also mean that each one is doing a small fraction of the total work, and thus the system could handle enormous power, has tremendous dynamic range and low distortion characteristics. Subwoofers are recommended for the lowest fundamentals below 45Hz.

Not to mention that they look absolutely stunning. ;) More importantly, I like that the styling is dictated by its design -- form follows function. It's not merely a gimmick.

Here are some links with more info about the CBT36:
http://www.parts-express.com/cbt36/
http://www.audioartistry.com/products_CBT.htm
http://www.xlrtechs.com/dbkeele.com/CBT.php

Needless to say I ordered a pair, waited for over a month (it was out of stock) and now they have finally arrived. I also ordered a DCX2496 electronic crossover, and am contemplating building another β24 power amp for bi-amping. I already have two Sunfire True Subwoofers (flat to 18Hz), along with a Velodyne SMS-1 subwoofer management system, so I am all set on that front.

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Re: New Speaker-fi: Audio Artistry CBT36

Postby amb » July 18th, 2012, 4:02 am

Here are some pics to start off:

The four boxes that everything came in, prior to unpacking:
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A close-up of the labels on the tall boxes containing the cabinet parts:
Image

The cabinet columns -- still wrapped in plastic:
Image

Yup, 36 bass/mid drivers, 144 tweeters, wires and other parts:
Image

Gaskets, fiber-fill, and the documentation pack:
Image

The cabinet bases and hardware:
Image

Another look at the curved columns, now out of the plastic bags:
Image

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Re: New Speaker-fi: Audio Artistry CBT36

Postby Nebby » July 18th, 2012, 5:57 am

I've always been interested in line arrays, so I'll be following your build with great interest :) I wonder how they mass produce that curved front and rear baffle?
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Re: New Speaker-fi: Audio Artistry CBT36

Postby joeyjojo » July 18th, 2012, 6:30 am

Looking good.

So the DIY element of this is what exactly? Treating the wood, assembling the drivers and wiring them to the connectors? Seems trivial.

You say you're "considering" another B24 for the bi-amping. What's the alternative?
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Re: New Speaker-fi: Audio Artistry CBT36

Postby wolfie » July 18th, 2012, 7:14 am

I've been looking for speakers for some years now and this project will take top priority for me.

I will also get the recommended crossover (shortest route to listening) but i wonder if you have any intention to someday put a crossover on your project list.

Some B24's will soon appear on my project list also. I've made some of your projects and have always been impressed by the quality of the parts and the excellence of your extensive documentation.
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Re: New Speaker-fi: Audio Artistry CBT36

Postby linux-works » July 18th, 2012, 9:46 am

there are better crossovers than the dcx, but not for the price! and also, its all digital inside and you can send spdif in and hack it to get i2s out, bypassing every one of the analog pre/post stages. at that point, its only DSP and there's no analog degradation.

the minidsp is a challenger but I'm not sure its up to the behringer set of features.

there won't be an analog filter invented that can beat pure numerical crunching and when you stay all digital, analog is just not even in the vocabulary anymore ;)

what I'd like to do, someday, is take my own dcx2496 and tap into its i2s outputs, bypass its onboard set of 3 dacs and send the i2s to gamma2 boards (3 of them) or something like that. there are a lot of mods for the dcx to fix its less-than-perfect set of power supplies but if you treat the box as a computation-only box, the psu then does not matter at all.

I've been using my own dcx for about a year now on my active XO spkrs and if there's ever a choice, I'll pick active over the single-amp approach. its more hassle (the vol control has to be multi-gang) but I do think its worth it.

but two b24's and those speakers: did you buy extra home insurance to make sure the floors can hold all that?? ;)
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Re: New Speaker-fi: Audio Artistry CBT36

Postby amb » July 18th, 2012, 10:28 am

Nebby wrote:I've always been interested in line arrays, so I'll be following your build with great interest :) I wonder how they mass produce that curved front and rear baffle?

I think they are simply bent into a curve.

joeyjojo wrote:So the DIY element of this is what exactly? Treating the wood, assembling the drivers and wiring them to the connectors? Seems trivial.

It may seem so, but the cabinet finishing will be a work of love. It's a different kind of DIY, which I used to do a lot more of years ago.

You say you're "considering" another B24 for the bi-amping. What's the alternative?

Until I finish building another β24, I may use one of my Hafler DH-220s in the interim. But to me it just doesn't seem "right" not to use β24s everywhere.

wolfie wrote:I will also get the recommended crossover (shortest route to listening) but i wonder if you have any intention to someday put a crossover on your project list.

I'll probably do some mods to the DCX2496, once I figure out its innards. Most likely just analog stuff.

As for another crossover project, probably not. I like the flexibility of the DCX2496 and it doesn't make sense to try to emulate it (when it costs about $300 street price). If you use its analog inputs, it does involve an extra A/D and D/A conversion inside, but I don't think it's worse than complex analog filters.

linux-works wrote:but two b24's and those speakers: did you buy extra home insurance to make sure the floors can hold all that?? ;)

lol, I'll need to get rid of my neighbors too.
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Re: New Speaker-fi: Audio Artistry CBT36

Postby linux-works » July 18th, 2012, 10:56 am

I'm half serious - 2 b24's is a lot of weight. are those spkrs and the cabinets heavy? what are their quoted weights, once built?

how about breaking the tweeters into groups and powering them with b22 sections or chip-amp sections? and then use the existing b24 for the heavy lifting (lol).
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Re: New Speaker-fi: Audio Artistry CBT36

Postby particleman14 » July 18th, 2012, 12:25 pm

I've been eyeing these arrays for quite some time now too. very interested to see how they turn out. what type of painting scheme are you thinking of?
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Re: New Speaker-fi: Audio Artistry CBT36

Postby amb » July 18th, 2012, 12:51 pm

particleman14 wrote:I've been eyeing these arrays for quite some time now too. very interested to see how they turn out. what type of painting scheme are you thinking of?

I'm still weighing the options. The front baffle will most likely be a glossy automotive-grade paint similar to the Parts Express catalog sample, but I'm still thinking about the color. I have also not yet decided on the rest of the enclosure. Parts Express did theirs in all black. I might do that, or go with a wood veneer. The curvature of the columns may make wood grains look weird, though.
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