[sl_1800]

I own the latest parts express CBT36 version. I have slightly modified the design to encompass a 15" parts express sub and Digamoda DSP controled 3 channel amps.

The sound is mind blowing. Much better than I heard at RMAF 

Not a easy build, but I have had many a reference quality speaker and these will hang with any of them regardless of price. They have some of the best imaging I have ever expierenced.

Takes a little effort to tweek the speaker balance to your room / system. but WAY easy compared with tweeking standard passive crossovers.

nickd, would you mind telling us what other speakers you have had that you have had?  I'm not doubting you I'm just curious what they were.

[Bjorn]

If it's scaled down, one will not get a controlled uniform response particularly low in frequency. And obviously you will not have the same output. Other then that, I think it could work, but Don Keele would be the person to give a better answer.

Below is a picture of a smaller CBT prototype. It measured great, but became omni earlier in frequency then CBT36.


Also a few pics of my CBT36 speakers. I certaintly wouldn't judge a speaker from a show by the way. I'm not sure now, but at the first shows Audioartistry demoed them with a ruler flat response. A flat response sounds too bright IMO and especially if the room isn't much treated. The beauty with an active speaker system like this is of course that you can tailor the response to the room and taste.

[studley]

Re the CBT 36 kit, are the cabinets completely unfinished I.e. you have to paint them yourself?

Also some more comments on the difficulty of the build would be interesting.  Bjorn?

[milford3]

One very simple question.  How does one handle the crossover on these speakers?  Oh, by the way, they are beautiful.

[James Romeyn]

deleted

[Bjorn]

Re the CBT 36 kit, are the cabinets completely unfinished I.e. you have to paint them yourself?

Also some more comments on the difficulty of the build would be interesting.  Bjorn?

The cabinets are unfinished. They are very coarse and need much sanding as well as paint. I got someone do to that for me.

This was the first speakers I've ever built. I had not even soldered before. I got some help, but I wouldn't say it's difficult. It's simply takes time. The manual is so thorough and detailed, that anyone can build this as long as they can solder. And if one has soldered before, like me, you just need to practise a little before starting.
The manual takes you step by step.

The manual suggests a Behringer DCX2496 crossover and also tells you how to set it up. You can also download the presets directly from Audioartistry's website. I would however recommend using a miniDSP 4x10 Hd or 10x10 Hd instead. The Behringer is a bottleneck when it comes to sound quality and it's not without noise when hocking up with commercial electronics. The miniDSP is also much easier to use and has a volume control. So no need for a preamp. I believe Audioartistry will also soon give presets for the minDSP which can be loaded in. It might help speeding up the process by asking them for it.

[James Romeyn]

What is CBT36 sensitivity anechoic? 

I suppose CBT36 rate of decrease vs. distance differs from normal mono pole.  For instance, monopole SPL decreases with square of increased distance, while dipole decreases at only one half mono pole rate. 

[James Romeyn]

...The manual suggests a Behringer DCX2496 crossover and also tells you how to set it up. You can also download the presets directly from Audioartistry's website. I would however recommend using a miniDSP 4x10 Hd or 10x10 Hd instead. The Behringer is a bottleneck when it comes to sound quality and it's not without noise when hocking up with commercial electronics...

Do the above negative reports re. the 2496 derive from personal experience?  If yes, please explain details.  If this is only 2nd hand report to you it would be nice to know.   

This is critical because I contemplate 2496 for LP/HP @ 80 Hz only, in top level system. 

[James Romeyn]

I want to hear CBT36 at first opportunity.  Holler if you know of CBT36 audition in Salt Lake City area or parts N. 

Quotes from Audio Artistry page:

"THE VERTICAL AND HORIZONTAL COVERAGE OF THE CBT36 GREATLY REDUCES
CEILING AND WALL REFLECTIONS:
The above-the-floor vertical coverage of the CBT36 is a narrow 28º which is extremely stable with frequency. This greatly reduces ceiling reflections as compared to a typical box style system. In addition, the horizontal coverage which is very broad narrows as you go around the side of the system, which also significantly minimizes side wall reflections.

I must miss something obvious, sorry.  How is "horizontal coverage" simultaneously "broad" and "narrow as you go around the side?"  Does not horizontal radiation = lateral radiation as defined by radiation to the L and R "side" of some defined vertical line?  The terms "broad horizontal coverage" and minimum "side wall reflections" are mutually exclusive.  This looks like ad copy text from uninformed author.   

EXTREMELY EVEN COVERAGE WITH NO SWEET-SPOT LISTENING AXIS:
The system has extremely well-behaved and smooth coverage from locations well above the array to points even down at floor level, and at distances from directly in front of the speaker to points in the rear of the listening room. The horizontal coverage is extremely broad and uniform even out to plus-minus 90 degrees.

Sorry, again, 180 degree horizontal radiation = extreme quantities of side wall and other reflections from furniture in very large radius.  The very best and most unique quality of MBL is also their worst quality (360 degree radiation).   

The CBT36's variation of loudness with, distance is also very unique. At standing height, the system's volume level hardly changes over a range from directly in front of the system to points 10 feet away!

MAXIMUM SPL AND DISTORTION:
The system can be played extremely loud and remains very clean and effortless at all levels. The large number of drivers minimizes distortion, and driven with powerful amplifiers the system can generate very-high instantaneous peaks.

I realize that certain companies such as Klipsch overstate sensitivity by about 5-7 dB.  But surely Keele, Linkwitz, and Toole can specify some sensitivity spec with whatever qualifiers they so desire, such as the fact that SPL decreases with distance at only 1/2 the rate of a mono pole!  Then readers can make their own calculations.  Without numbers the above language has absolutely no definite meaning.

SYSTEM REQUIREMENTS:
The system must be bi-amped and requires a DSP-based speaker processor along with two stereo power amplifiers. For extended bass response below 45 Hz, one or two powerful subwoofers are required.

Above states 45 Hz yet they crossed @ 60 Hz at RMAF 2011:

...Demmed with Jeff Rowland Design Group amplification and crossed over to an active woofer below 60Hz...

The difference between 45 and 60 Hz is .4 octave or almost twice the cone stroke.  The smaller the mid bass the higher the cut off and 3" is the smallest I know of.  The closer to the limit of operation the more critical is a high-pass pole required.  Did they employ high pass pole @ 60 Hz at RMAF?  Also, the higher the sub pole the more difficult is sub setup lacking a distributed array.  In my experience the more difficult the sub install the more critical is continuous phase control or at least 90 degree setting. 

All these little details spell the difference between happiness and failed performance.  Buyers deserve to know if they need another stereo 60 Hz crossover pole and multiple subs to match show performance.  A 60 Hz pole increases setup and siting difficulty.  IMO subs require 90 degree phase crossed in that range.     

[Bjorn]

What is CBT36 sensitivity anechoic? 

I suppose CBT36 rate of decrease vs. distance differs from normal mono pole.  For instance, monopole SPL decreases with square of increased distance, while dipole decreases at only one half mono pole rate.

The sensitive changes with frequency and falls the higher it goes up in freqeuncy. This is stated in the manual by the way:

Note: the raw sensitivity (no crossover or EQ) of the CBT36 is frequency dependent. It is roughly flat from 80 to 300
Hz and then rolls off at 3 dB/octave (10 dB/decade) up to 20 kHz. See later section “CBT36 Power Rolloff” in
Appendix 2 for further explanation of this rolloff. For more details see Fig. 26 in this section. Here are some
approximate sensitivity numbers at different frequencies:
80 to 300 Hz: 94 dB
800 Hz: 89 dB
8 kHz: 79 dB

The reduction of SPL is 3 db pr meter. It's 6 dB pr meter with a regular speaker. Because the CBT uses the floor as a mirror, the sensitivity of the array is doubled compared to a free standing array of the same height. Still, due to the fact that CBT36 uses ineffective tweeters, the sensitivity in the treble area isn't very high. But I don't believe it has any limitations for home usage. It can play loud. I've attached an illustration of the sensitivity and SPL of CBT36.

Do the above negative reports re. the 2496 derive from personal experience?  If yes, please explain details.  If this is only 2nd hand report to you it would be nice to know.   

This is critical because I contemplate 2496 for LP/HP @ 80 Hz only, in top level system.

I have the DCX2496. The noise isn't a major problem though. But there will be some hiss coming from the tweeters unless you either use pro amps or do some modification. It's possible to modify the DCX2496 to a high-end product, but it's not cheap. The fact that the sound quality isn't stellar, is well known and something you can google.
http://www.linearaudio.nl/
http://www.pilghamaudio.com/index.php?page=dcx-active-upg
http://www.audiocircle.com/index.php?topic=47777.0

[James Romeyn]

What should readers presume by your lack of reply to my points rel. to seller's ad text relative to apparent obvious and extreme contradictions re. radiation patterns?

Do you employ high pass global main speaker crossover, slope, pole, subs, etc?   

Do you mean "meter" or doubling of distance?

[Bjorn]

James:
Here's a comment from Don Keele regarding the horizontal dispersion:

The horizontal coverage of the CBT36 is a function of the horizontal off-axis angle and actually gets narrower as you go off-axis. Here’s a fig from my paper to illustrate that illustrates the sound field of a free-standing circular-arc CBT line array. Because the array is a ground-plane array the narrowing goes down to floor level, i.e. you get less and less illumination of the side walls as you go around the side. If you listen to the system on the side, it gets louder and louder as you squat down!

So what’s the conclusion? Yes the CBT36 does illuminate the walls, but with essentially a spectrum that is quite flat and that decreases considerably with height at distances particularly close to the array.

A subwoofer should be crossed over dependent on the frequency response and your need for SPL. I cross them over at 80 Hz. There's no definite answers here, but personally I wouldn't use the CBT36 as low as 45 Hz. Remember that it's a sealed box and in reality not a big speaker considering the size of the drivers. Crossing over in the 80 Hz area isn't much of a problem considering that those frequencies are difficult to localize. When crossing over quite a bit higher, integration with time because important.

Regarding the vertical dispersion and the wide horizontal dispersion, here's something I've written earlier that you might find useful:

The CBTs can offer both; A spacious soundfield where the reflected energy resembles the direct signal and hence little coloration. Or a more precise and sharp image with treatment if that's what you want. The listener gets to choose and both will work extremely well.
A typical waveguide/horn speaker can however not give the spacious soundfield without much coloration. If you leave the sidewalls reflective, you end up with some reflective energy at certain frequencies and nothing or less at others. In that case, broadband treatment is required for correctness.
An even more so vertically where the waveguide/horn will show more lobing.

With the CBT the floor reflection is a benefit. It is coupled to the floor and the reflection contributes what is effectively the other half of the CBT. So it negates the need for a full arc. This is a great advantage. It effectively eliminates the need for floor treatment that is problematic at best. Especially as any floor treatment typically exhibits a such a high frequency profile as to not be effective as broadband absorption for a traditional speaker. A bare broadband reflective floor surface is optimal.

The vertical disperion of a full CBT arc is 45 degrees. Therefore I am thinking that when placed on the floor, that the upward tilt would be restricted to 1/2 that. Thus from the horizontal plane it would only be a 22.5 degree upward distribution. As such, this effectively eliminates early ceiling reflections until well behind the typical listening position and thus eliminates the need for ceiling treatment, unlike typical loudspeakers.

The CBT benefits from a near uniform 180 degree power response and a constrained vertical distribution. In both axes it avoids a collapsing polar power response, which so typical of other designs.
http://www.xlrtechs.com/dbkeele.com/images/Card%20Back%20Large.png

And in all cases, the soundstage of the CBT offers an improvement over traditional speakers, as not only is the power response uniform over the horizontal plane, substantially increasing usable listening positions or eliminating many of the typical constraints that limit listening positons, and the limitations of a nearfield response due to destructive driver interaction (superposition) are effectively rendered moot.

[James Romeyn]

Just so readers know, I have no affinity for and no regard for any speaker with mono pole, bi pole, dipole, nor omni pole radiation pattern.  Any such speaker regardless of cost and complexity is wholly inadequate to reproduce musical sound in a domestic space.

That's why I find this speaker so interesting. 

But certainly, from the image, at the mid vertical point, this CBT has extremely wide 180 degree dispersion pattern which inevitably increases reflections from the side wall at that vertical point and any furnishings on that line.   

I should have a 2496 here soon enough to hear it myself.  I presume the fact that I will cross at 80 Hz hp/lp makes all comparisons moot to other persons employing typical 1.0-2.5k Hz pole.  I asked you to explain your use of the qualifier "bottleneck" not other opinions which are already on on record.  I know about Google and how to use it.   

[Bjorn]

Just so readers know, I have no affinity for and no regard for any speaker with mono pole, bi pole, dipole, nor omni pole radiation pattern.  Any such speaker regardless of cost and complexity is wholly inadequate to reproduce musical sound in a domestic space.

That's why I find this speaker so interesting. 

But certainly, from the image, at the mid vertical point, this CBT has extremely wide 180 degree dispersion pattern which inevitably increases reflections from the side wall at that vertical point and any furnishings on that line.

Several of your questions are answered in the manual or in Don's paper. The manual can be downloaded:
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=301-980
Don's page with papers:
http://www.xlrtechs.com/dbkeele.com/CBT.php

Your question regarding the horizontal dispersion was answered in my previous message. Like mentioned, with the CBTs the listener can choose between a wide and spacious soundfield with little coloration leaving the sidewalls reflective or a sharp and precise image with sidewall treatment. The fact is that a speaker with a narrow horizontal dispersion will give you coloration without sidewall treatment because it becomes omni horizontally at a certain frequency, where dependent on the size of the horn. If you desire an acurrate and precise image you need in reality sidewall treatment for both types of speakers. Vertically, the CBT doesn't need any, while a horn speaker does.

[James Romeyn]

Thanks for the links.

There is a unique array that simultaneously provides immersion equal to MBL and image precision equal to the world's best point source mini monitor.  For a time I thought possibly this CBT might equal the array I describe above, but from this reading it apparently does not.   

The array I describe above also provides density of the best horn systems, transparency of the best planar, 96 dB sensitivity from high 30 Hz range up (in-room), and other unique benefits such as higher pitch accuracy from top to bottom and stage size 75' beyond front and side walls. 

[bernardo]

Well don't keep us in the dark - you are describing the perfect speaker. I for one want to know what speaker you are describing.

[studley]

Thanks for the links.

There is a unique array that simultaneously provides immersion equal to MBL and image precision equal to the world's best point source mini monitor.  For a time I thought possibly this CBT might equal the array I describe above, but from this reading it apparently does not.   

The array I describe above also provides density of the best horn systems, transparency of the best planar, 96 dB sensitivity from high 30 Hz range up (in-room), and other unique benefits such as higher pitch accuracy from top to bottom and stage size 75' beyond front and side walls.

Let me guess, you sell them?

[rjbond3rd]

I heard the CBT at RMAF a few years ago and thought it was incredible.  Completely unlike any other speaker.  At that particular show, it was EQ'ed too bright, and the musical choices were just awful, but the sound was fantastic. 

They sounded huge, and projected a sort of forest of sound.  Not the standard holographic imaging , but a different thing completely.  A description probably can't do them justice. 

(If I had two criticisms: (a) like nearly all other speakers, the CBT's don't necessarily have -tone- completely nailed with those particular drivers, but you can't have everything -- I have speakers with perfect tone which are worse in just about all other respects than the CBT's, and (b) as amazing as they are, they don't "breathe" like a perfectly tweaked horn system, but those are -very- picky criticisms!  It seems most people don't value those two things anyway.)

[Bjorn]

I heard the CBT at RMAF a few years ago and thought it was incredible.  Completely unlike any other speaker.  At that particular show, it was EQ'ed too bright, and the musical choices were just awful, but the sound was fantastic. 

They sounded huge, and projected a sort of forest of sound.  Not the standard holographic imaging , but a different thing completely.  A description probably can't do them justice. 

(If I had two criticisms: (a) like nearly all other speakers, the CBT's don't necessarily have -tone- completely nailed with those particular drivers, but you can't have everything -- I have speakers with perfect tone which are worse in just about all other respects than the CBT's, and (b) as amazing as they are, they don't "breathe" like a perfectly tweaked horn system, but those are -very- picky criticisms!  It seems most people don't value those two things anyway.)

I believe they were EQ'ed flat. And a flat response will in most cases sound too bright. Most seem to prefer a response that is lifted in the bass and gradually falls towards the top end. Not a problem when you have an active speaker system where this can be adjusted to the taste and room.


Like previously mentioned, you can also have a precise image with the CBTs. One simply need to treat the sidewalls with some absorption or deflectors. That's the beauty of these speakers; They can give great pin pointing for those who want that with some treatment or a wide and spacious sound using lateral contribution with little coloration. They choice is there. The best way to combine precise image and spaciousness is attenuating early reflections and diffuse late arrival ones from behind. That's what I personally do.

A speaker like MBL, which is omni horizontally, is in my opinion detrimental in small rooms. It will never yield anything close to a precise image. The room would had to be completely dampened and that would become an overly dry and dead environment. The front wall reflections should be avoided. If one wants to have contributing reflections in a setup, they should come from sidewalls. Either from both sidewalls or only from the opposite sidewalls, depending on the size of the room and taste.
MBL, the more expensive ones, only has a flat response by the way at a certain height. The CBT is flat at almost every height.

[athakuria]

Please excuse me if I come across as ignorant, but unfortunately I cannot seem to get any response from AudioArtistry .. I have had the kit for some time and still have to finish the cabinets. So I have a long way to go
So my question is how difficult is to configure the mindsp 10x10 HD for optimal sound out of the CBT36s?

Appreciate you taking the time to respnd.

Anjan