Today is your lucky day! CBT arrays have a beamwidth of well over 120 degrees and great dynamics.
Congrats Jim! It is good to hear that arrays were independently rated and did very well. Maybe we'll finally start to see more builds now.
How did you set them up at MWAF? Did you apply EQ, Audessey correction, or some other form of correction, or was it all passive? Did you route the bass to a sub?
How did you set them up at MWAF? Did you apply EQ, Audessey correction, or some other form of correction, or was it all passive? Did you route the bass to a sub?
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The competition in the Open Unlimited (OU) class are all active entries so the passive entries are placed in one of the other 3 classes. The second place speaker in the OU class was Brian Z's Reference Monitor that is described in his thread on Parts Express's Tech Talk forum at:
Let's post something interesting: the ultimate small speaker build thread. -
Techtalk Speaker Building, Audio, Video Discussion Forum
Lots of technology in Brian's small monitors.
For some photos of several speakers which won first, second, or third in the various classes of the MWAF speaker competition see this thread starting with:
Countdown to MWAF... -
Techtalk Speaker Building, Audio, Video Discussion Forum
I'm in post #58 of that thread. Page through the next two pages to see Brian Z's second place in OU at post #71 and Scott M's third place in OU in post#75. As you can see it was quite a beauty contest for speakers.
As there is not enough time to tweak or change your setup at the event, my speakers are the same as in my home listening room that I mentioned in Post #60 of this thread.
Jim
Let's post something interesting: the ultimate small speaker build thread. -
Techtalk Speaker Building, Audio, Video Discussion Forum
Lots of technology in Brian's small monitors.
For some photos of several speakers which won first, second, or third in the various classes of the MWAF speaker competition see this thread starting with:
Countdown to MWAF... -
Techtalk Speaker Building, Audio, Video Discussion Forum
I'm in post #58 of that thread. Page through the next two pages to see Brian Z's second place in OU at post #71 and Scott M's third place in OU in post#75. As you can see it was quite a beauty contest for speakers.
As there is not enough time to tweak or change your setup at the event, my speakers are the same as in my home listening room that I mentioned in Post #60 of this thread.
Jim
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View attachment ModifiedCBT24Weighting.pdf
I have attached a file which shows the Modified CBT24 Weighting Network. The resultant nominal input impedance of the array is approximately 4 ohms.
The resistors in Bank 3 of the weighting network have desired values are 8 ohms and 25 ohms. The power rating I wish to have is 20 Watts for each resistor.
For my arrays I used two parallel connected 16 ohms Mills non-inductive resistors to yield the 8 ohms resistor value. Each of the 16 ohms resistors are rated 12 Watts so the two parallel connected units would be a 24 Watts total rating. To realize the 25 ohms resistor value I have paralleled connected two 47 ohms resistors to yield a value close to the desired 25 ohms. My Mills resistor supplier stocks 47 ohms resistors so a 23.5 ohms value is close enough.
I have attached a file which shows the Modified CBT24 Weighting Network. The resultant nominal input impedance of the array is approximately 4 ohms.
The resistors in Bank 3 of the weighting network have desired values are 8 ohms and 25 ohms. The power rating I wish to have is 20 Watts for each resistor.
For my arrays I used two parallel connected 16 ohms Mills non-inductive resistors to yield the 8 ohms resistor value. Each of the 16 ohms resistors are rated 12 Watts so the two parallel connected units would be a 24 Watts total rating. To realize the 25 ohms resistor value I have paralleled connected two 47 ohms resistors to yield a value close to the desired 25 ohms. My Mills resistor supplier stocks 47 ohms resistors so a 23.5 ohms value is close enough.
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Jim, referring to your post 65, were you able to set them up with correction at the event? If yes, then how did you do the EQ? And how about the sub?
Looking at the pics, it appears that the judging was sighted. Is that true? If so, it is a little disappointing because it is easy to put a curtain in front of the judges and that would eliminate bias. The diy competition in Seattle is unsighted for the judges, and in fact, there were strict rules on where the judges could and could not go during listening. Not trying to take anything away from your speakers. I totally believe that they sound awesome. Just wishing the MWAF/PE folks could've done it a little better.
Looking at the pics, it appears that the judging was sighted. Is that true? If so, it is a little disappointing because it is easy to put a curtain in front of the judges and that would eliminate bias. The diy competition in Seattle is unsighted for the judges, and in fact, there were strict rules on where the judges could and could not go during listening. Not trying to take anything away from your speakers. I totally believe that they sound awesome. Just wishing the MWAF/PE folks could've done it a little better.
I really go back and forth on the Unity horn thing. I've built a ton of them, but my day-in-day-out speaker is a weird CBT loaded-in-a-waveguide thing. It doesn't have much 'sparkle' in the treble but the midrange is just spot-on.
So it's interesting that John's Synergy Horn came in 2nd, and Rick's CBT came in first.
So it's interesting that John's Synergy Horn came in 2nd, and Rick's CBT came in first.
I think horns always have a signature to them. Anything less than a Geddes like implementation will probably have some kind of megaphone effect to some extent.
I've been playing around with compression drivers mounted directly to the baffle. The sound is subjectively less harsh on challenging music despite having to use more power. Like a dome tweeter with higher output.
I've been playing around with compression drivers mounted directly to the baffle. The sound is subjectively less harsh on challenging music despite having to use more power. Like a dome tweeter with higher output.
With my Summas I noticed that I could listen to them all day long, similar to my weird CBT thing. There were weeks where I'd have them playing 50-60 hours a week. (I work at home.)
I build waveguides a bit obsessively and I've started to notice a couple things about them:
1) as they get larger and larger, they seem to perform worse. Basically it's easier to get spectacular performance out of a modestly sized waveguide than a large waveguide
2) The jury is still out, but wide angle waveguides seem to outperform narrow angle waveguides. The difference isn't night and day, it's subtle, hence "the jury is still out." There's an AES paper that found that shallower waveguides are subjectively better sounding. (I'm too lazy to look it up, it's from 2004ish)
I've definitely been tempted to build a CBT of waveguides, because there's no reason you can't combine the two.
The EAW Anya can be configured in various ways, but if you shade the arrays in the element and curve them electronically, it is basically a CBT of waveguides.
I build waveguides a bit obsessively and I've started to notice a couple things about them:
1) as they get larger and larger, they seem to perform worse. Basically it's easier to get spectacular performance out of a modestly sized waveguide than a large waveguide
2) The jury is still out, but wide angle waveguides seem to outperform narrow angle waveguides. The difference isn't night and day, it's subtle, hence "the jury is still out." There's an AES paper that found that shallower waveguides are subjectively better sounding. (I'm too lazy to look it up, it's from 2004ish)
I've definitely been tempted to build a CBT of waveguides, because there's no reason you can't combine the two.
The EAW Anya can be configured in various ways, but if you shade the arrays in the element and curve them electronically, it is basically a CBT of waveguides.
ra7, if it worries you that the judges could view the speakers, you should revisit the judging criteria given in the MWAF link in my post #60 above.
The five judging factors are:
The Craftsmanship (visual)
Originality / Design (visual)
Tonal Balance (audio)
Clarity (audio)
Imaging (audio)
Notice that the first two are visual elements while the last three are audio/hearing criteria.
Patrick, my CBT was the only one at the MWAF this year. Who is Rick?
Jim
The five judging factors are:
The Craftsmanship (visual)
Originality / Design (visual)
Tonal Balance (audio)
Clarity (audio)
Imaging (audio)
Notice that the first two are visual elements while the last three are audio/hearing criteria.
Patrick, my CBT was the only one at the MWAF this year. Who is Rick?
Jim
I see now that you have simplified the shading a great deal compared to Keele. As far as I can see you have:
-3 banks insted of 5.
-Size of the banks 50% + 25% + 25+ instead of Keele's progressively smaller banks.
This seems clever if it works, since the shading network will be much simplified. Do you have any idea how this modification affects performance compared to Keeles shading scheme with 5 banks?
Since you won the first price, I guess it works well!
jeno,
Don Keele shared his weighting network for his Dayton Audio Epique CBT24 arrays sold by Parts Express. Don's network uses a three level network to achieve a Legendre taper.
Epique CBT24 Line Array Speaker System Pair
The Epique CBT24 use a 16 ohms nominal impedance driver also sold by P-E.
My Modified CBT24 design evolved from Don's weighting approach but I'm using the 4 ohms SBA65. So the weighting network for the SBA65 needed changes to maintain the same power levels and impedances.
Jim
Don Keele shared his weighting network for his Dayton Audio Epique CBT24 arrays sold by Parts Express. Don's network uses a three level network to achieve a Legendre taper.
Epique CBT24 Line Array Speaker System Pair
The Epique CBT24 use a 16 ohms nominal impedance driver also sold by P-E.
My Modified CBT24 design evolved from Don's weighting approach but I'm using the 4 ohms SBA65. So the weighting network for the SBA65 needed changes to maintain the same power levels and impedances.
Jim
The passive weighting network which Keele uses and that I use/recommend is very simple and straight forward. Having the experience with my DSP corrected 3 stereo amplifiers open baffle speaker, I understand what a triamp system can do.
Don Keele has a paper which discusses a CBT he designed with a straight array. The delay and amplification levels uses separate channels. These channels accommodate the phase changes (accounts for the time delay achieved by the array curve) to vary the differences in phase and gain for each bank of drivers.
JBL sells their CBT Series of speakers which have straight array cabinets yet achieve the CBT benefits via internal phase shift networks. These speakers uses Don Keele's previous CBT work. See this link for details:
CBT Series
Don Keele has a paper which discusses a CBT he designed with a straight array. The delay and amplification levels uses separate channels. These channels accommodate the phase changes (accounts for the time delay achieved by the array curve) to vary the differences in phase and gain for each bank of drivers.
JBL sells their CBT Series of speakers which have straight array cabinets yet achieve the CBT benefits via internal phase shift networks. These speakers uses Don Keele's previous CBT work. See this link for details:
CBT Series
Note that the JBL CBTs, with a passive network, barely curves the wavefront at all. The vertical beamwidth is something like ten degrees. Much narrower than the CBTs that Keele did for Parts Express.
My 'hunch' is that JBL was doing their best to make them cost effective. A curved cabinet is expensive to manufacture and ship. And a shaded array has less output than a straight array.
So the JBL CBTs have a *tiny* bit of curvature, to make them more cost effective.
Details here:
Passive Loudspeaker Delay
My 'hunch' is that JBL was doing their best to make them cost effective. A curved cabinet is expensive to manufacture and ship. And a shaded array has less output than a straight array.
So the JBL CBTs have a *tiny* bit of curvature, to make them more cost effective.
Details here:
Passive Loudspeaker Delay