Next Project: Arc 40 CBT Array

[r-carpenter]

Sounds to me Rick that basically you are saying: I don't have to share anything (not an obligation) and if you want my knowledge, you got to pay. Fair enough.

Now, here's what I would have liked to see from this build.
Line arrays are fairly difficult to build. Good sounding line arrays, anyway. CBTs have had so-so response from many listeners already. So, to me, looking at the unfiltered response, logistics behind filter development and subjective impressions of the listener (Kevin) would be a useful and beneficial info. I am sure, not only to me but to may DIYers who contemplated building one of these. What is Kevin going to learn from the build? He already knows how to 3D model and CNC.
Well, I'll b.utt out. Have a good time.

[Kevin K.]

Sounds to me Rick that basically you are saying: I don't have to share anything (not an obligation) and if you want my knowledge, you got to pay. Fair enough.

Now, here's what I would have liked to see from this build.
Line arrays are fairly difficult to build. Good sounding line arrays, anyway. CBTs have had so-so response from many listeners already. So, to me, looking at the unfiltered response, logistics behind filter development and subjective impressions of the listener (Kevin) would be a useful and beneficial info. I am sure, not only to me but to may DIYers who contemplated building one of these. What is Kevin going to learn from the build? He already knows how to 3D model and CNC.
Well, I'll b.utt out. Have a good time.

Roman,

Not sure why you have chosen to take issue with this build thread. I've seen numerous threads on the forum where "the how's or why's" of many designs are never disclosed.

I respect your opinions but can't say I agree with everything you've said. Your first statement about Rick is totally out of line IMHO, and if it was true, then Rick would be charging me for his help on this build and that is not the case. Then you questioned what I will learn from it. There is well over a thousand miles in between Rick and myself and he will have to instruct me on a lot of the things to do with these to complete them. If I walk away from this build not knowing any more than I do right now, I need to get out of this hobby all together. Will I be able to design and build one myself next time, probably not. And that is fine with me, really. My only goal with each new build is to learn just a little more then I knew before, it doesn't have to be an "All or Nothing" adventure.

Rick and I have talked briefly about the details of this build and I believe Rick will probably share enough information about this build for someone else to duplicate if they so desired. As for the "how's or why's" of the details, that's the part I suspect Rick will prefer to keep to himself as do many designers on these type of forums, especially the ones who make their living from Audio.

Hopefully, my opinions about your opinions don't drive a wedge between us, it is not my intention.

Take care,
Kevin

[rickcraig]

Sounds to me Rick that basically you are saying: I don't have to share anything (not an obligation) and if you want my knowledge, you got to pay. Fair enough.

Now, here's what I would have liked to see from this build.
Line arrays are fairly difficult to build. Good sounding line arrays, anyway. CBTs have had so-so response from many listeners already. So, to me, looking at the unfiltered response, logistics behind filter development and subjective impressions of the listener (Kevin) would be a useful and beneficial info. I am sure, not only to me but to may DIYers who contemplated building one of these. What is Kevin going to learn from the build? He already knows how to 3D model and CNC.
Well, I'll b.utt out. Have a good time.

Wrong assumption - I share things quite often without asking for anything in return. It is my full-time business though so I cannot give out everything for free. True, good sounding arrays are not easy to build. It takes a great deal of time and investing in parts and equipment. I've built more arrays than most so I have a pretty good idea how CBT designs compare to everything else. Due to the small sample number for most listeners I think forming an overall opinion on CBT's is difficult. One of the reasons for this project is to show what the format is really capable of with drivers that are neither ultra cheap or uber expensive. I'm sure in the process plenty of information will be shared that many will find beneficial and Kevin will have learned quite a bit as well.

[r-carpenter]

Due to the small sample number for most listeners I think forming an overall opinion on CBT's is difficult. One of the reasons for this project is to show what the format is really capable of with drivers that are neither ultra cheap or uber expensive. I'm sure in the process plenty of information will be shared that many will find beneficial and Kevin will have learned quite a bit as well.

It is not my opinion. I have not heard CBTs myself and only commented on other people's impressions.
Looking forward to the information your willing to share.

[r-carpenter]

Hopefully, my opinions about your opinions don't drive a wedge between us, it is not my intention.

Take care,
Kevin

Why would it?
Let me explain my position. Majority of the builds on this forum now days are either commercial kits or somebody else's designs. Considering your woodworking capabilities, I think you should have dived in to the design stage yourself and arrive to the conclusions, you yourself are happy with. And knowledgeable members, like Rick could steer you along the way. With use of DSP, changes in the x-over can be implemented instantly without additional investment in parts. This would be an interesting and challenging process.

[JavadS]

Why would it? Let me explain my position. Majority of the builds on this forum now days are either commercial kits or somebody else's designs. Considering your woodworking capabilities, I think you should have dived in to the design stage yourself and arrive to the conclusions, you yourself are happy with. And knowledgeable members, like Rick could steer you along the way. With use of DSP, changes in the x-over can be implemented instantly without additional investment in parts. This would be an interesting and challenging process.

I'll butt in where I shouldn't, but it's interesting how you have such strong expectations and opinions of what both Rick and Kevin should do. Why don't you give Kevin some space to share more about the project as it develops and I'm sure everyone will be happy with what comes about, there is no need to put such strong expectations or entitlement about someone else's project IMO. Javad

[Kevin K.]

Ok Roman, I understand your position a little better now. I agree with you, it doesn't seem like there are a lot of original designs on the forum now days, not sure why. So far, I haven't built any kits or anyone else's design for myself. It's not that I don't appreciate all of the designs and the designer's works, it's just in my nature to create things on my own. Some would view that as a mistake, perhaps, perhaps not. To me, it really all depends on why you are doing this in the first place. I enjoy this hobby for the creativity it allows me and it gives me an avenue to stay in practice on the CAD work which I also enjoy very much. I am learning "the basics" of audio design a little bit at a time, maybe not fast enough to suit some, but fast enough to suit me. I do appreciate your input.

[Dwight]

Just some words of encouragement on the merits of regular line arrays. I built some straight lines several years ago when they were all the rage, all holes cut by hand, whew! I used the 5 1/4 inch Definitive Technology buyouts, 12 per side I think and the Dayton PT2 planars 8 per side. The PT2 was deal of the day for $19 and either Jim Griffin or Rick Craig posted that this price was very close to cost for P.E. and you should jump on them if you needed them so I did. Everything you have heard about line arrays is true (at least the good stuff) they are very clean sounding and the music just seems to waft from them effortlessly. One thing I really like is that they sound very good even at low volume unlike some speakers that don't come to life unless cranked up. I have zero experience with CBT but I bet you will enjoy them. Keep us posted.

[Kevin K.]

Just some words of encouragement on the merits of regular line arrays. I built some straight lines several years ago when they were all the rage, all holes cut by hand, whew! I used the 5 1/4 inch Definitive Technology buyouts, 12 per side I think and the Dayton PT2 planars 8 per side. The PT2 was deal of the day for $19 and either Jim Griffin or Rick Craig posted that this price was very close to cost for P.E. and you should jump on them if you needed them so I did. Everything you have heard about line arrays is true (at least the good stuff) they are very clean sounding and the music just seems to waft from them effortlessly. One thing I really like is that they sound very good even at low volume unlike some speakers that don't come to life unless cranked up. I have zero experience with CBT but I bet you will enjoy them. Keep us posted.

Thanks for the insight and encouragement Dwight. Man that was a crazy good deal on the PT2's!

These are gonna take a while to build but I'm betting they wont disappoint. Super excited and can't wait to get to the finish line! There will be plenty of post between now and then, don't worry.

[Kevin K.]

It's been a couple of weeks and some of what I did this weekend really should have happened last weekend. Went in last weekend to cut some parts on the CNC, plugged in the 1TB flash drive that contains all of my cad files into the shop computer like I have done a hundred times before, except this time would be different. The IT guy upgraded the shop computer the previous week to Win 10 and installed a new virus software called "F-Secure". For some reason, still not sure why, it decided my Cad file for the array was a threat and corrupted it in the process of blocking it. Poof, all those hours designing this thing gone in the blink of an eye. A few choice words came out of my mouth, ok, not a few, a lot! After calming down, it was time to accept what had happened and start over. Needless to say, nothing gets plugged into that computer again without a back up on another drive.

I made some changes to the design in hopes of making it more stable front to rear and left to right. Don's approach for his arrays has been large foot pedestals to accomplish this. I wanted to try a different approach. Tom mentioned earlier I like to dive off into the deep end of the pool. This could now be considered the deep end of an Olympic diving pool Tom. Here is a screenshot of the revised CAD files. Don't pay attention to the colors, they are only for contrast.



The following is a screenshot of the substructure that everything is built around. The redesign increased the overall volume so a subdivision was required to bring it back down to the appropriate volume. The ribcage is attached to that and then outside panels would be attached to those.




Now this is where I expect to get laughed off the forum but I still feel it was worth it. Because of the complexity of the build and the fact that it takes 2 full 4x8 sheets of MDF to build one cabinet, I decided to build a half scale model. This would allow me to make sure the cabinets were feasible to build and to make any adjustments if necessary. Since the full scale cabinets will be built from 1/2" MDF, the half scale cabinets are built from 1/4". Hope you like pics, lots to follow. By the way, I found myself whistling the theme song from "Mission Impossible" the whole time I was building this. In other words, not super confident it could be pulled off.

This first pic shows all of the parts required to build one cabinet.



Everything is built from the inside out, so the subdivision sidewalls were glued together with a couple of shelves and then attached to the base.



Followed by the front subdivision panel and the back wall of the enclosure. All external panels were mitered to avoid "ghosting" after veneer.



There were grooves cut in the sidewalls of the subdivision for the ribs to slide in. This was to make sure the front of the ribs would land in the right place between driver openings on the front baffle.




Here is pic with all of the ribs glued in and the back cap in place. I did not glue the top back cap at this point, it was only held in place by a clamp for the next step.



Next was attaching the front baffle.



In this image, you can see where the ribs land between driver openings.



Due to the side panels having inside and outside arcs, an additional panel for each was needed for a bearing guide. They were attached with double sided tape and then chamfer cut. This tape is worth it's weight in gold!



The front side panels were glued on next, one side at a time.




And finally, the rear side panels. I did not glue these in place last night. They need some small adjustments (you can see the gaps in a couple of places). I ran out of steam and decided to call it a night.





Was it worth it? (you can stop laughing now) Not going to deny, it was a lot of work. But, IMHO, totally worth it. There were some inherent problems exposed that I will go back and fix in the final design. This should lead to it going together better when I build the full scale cabinets. Call me crazy, but I may even go through this whole "half scale" exercise again just to make sure. In other words, it may be a while before you see any more updates on the cabinets. The way I see it, you don't build a set of speakers like these very often, so there is no clock ticking on this build for me.

I'm also working with Rick on the wire harnesses and will probably build those before I actually build the cabinets. Was thinking it would be good to secure them to the subdivision to avoid any chance of rattles. If you look closely at the last picture with the ribcage you can see an opening on the left and right sides for the two harnesses to route through.

So, what do you think of it so far. With all of the ribs and arches, do you think it would be beneficial to line the walls? If so, that will probably have to be done to the side panels before they get glued on. The stuffing can be installed through the driver openings, they're big enough to get a hand inside of.

Thanks for checking it out!

[joeybutts]

Ahhhh!!! So much awesome going on. The design is beautiful, I'm a sucker for red and black motif, and I'm sure the audio aspect will sort itself out by the end. Keep bangin'.....

[donradick]

hope I don't get banned, but christ-all-mighty!!!
that's a complex structure! Don't think it ever could have been built before CAD.
I'm totally in awe, dude.

Yeah, if you've gone this far, build another 1/2 scale model.
Secure and/or hot glue the wire harness in.
I vote for lining the walls. You can usually tear it out if you need to, but you can't put it in later.

[tomzarbo]

Holy Cow,
That is literally incredible. That extra angle makes these so much more interesting looking if that's possible. That's precision that I can't get to. If I can't stick my pinky through a gap, I consider it 'fine.' I'm kind of kidding, but not by much.

I can't wait to see these come together, I know it will take some time, but I'm sure it will be worth the wait.
Start kicking, you're in deep!

TomZ

[Navy Guy]

Wow, the shape is really awesome!

[Kevin K.]

Thanks guys.

I think you're safe Don, the ban hammer isn't swinging your way for that.

Looks like the curse of the "double post" struck again Kerry. And they are an hour apart, never seen that before. Or, maybe you just wanted to emphasize that the shape is really awesome. Thanks.

Ok, it's gonna get lined. Will probably be a PITA, but it's gonna get lined. So for the next question, and maybe it will just lead to opinions, but I"m curious and don't fully understand the subject. Do you think kicking the sidewalls out helped diffraction or is it negated because I kicked the rear sidewalls back in? Thanks