Next Project: Arc 40 CBT Array

[Millstonemike]

No run time on these yet Sydney. But you do bring up a good point, I wonder how long it will take for the woofers to break-in/loosen up so to speak. Since the arrays are shaded, I'm guessing it will happen in stages, bottom bank first, followed by each subsequent bank.

I'm sorry I didn't mention this before. From building a sub a few years ago, I read that breaking in a woofer was best done in free air using its resonant frequency with little power (so as not to exceed xmax). I guess it's too late now unless you remove some drivers and tap into the individual woofer connections.

[Kevin K.]

Thanks Tom.

Perhaps Rick will chime in and we can see what he thinks on Rory's comment. If I was guessing, allowing the woofers to all play lower frequencies "un-shaded" while "shading" the tweeters or higher frequencies would cause the arrays to sound thick(not sure if that's the right word for it) as you moved closer to them, kind of like taking a speaker that has full BSC built into the crossover and mounting it in a wall. One of the amazing things about the CBT arrays is their ability to sound the same from near or far and I believe you would lose that if you did what Rory was talking about. Maybe I'm way off base here and have everything confused, not difficult for me to do, trust me.

[tomzarbo]

You know Kevin,

it doesn't seem like something anyone is working towards, but I keep thinking about Rory's comment back in the hotel the evening after last year's MWAF... Regarding the smaller arrays that you built the cabinet for....

The jist of it was...

it would be interesting if you could just "shade" the directional output of the woofers while leaving the low (non-directional) frequency output un-attenuated. In other words, get the full bass effect from the upper drivers while toning down what needed to be toned down for it to work as a shaded array.

I thought it was a genius idea at the time and I still do... though I have no idea how difficult that would be to pull off... even with DSP and all those tricks.

I just wonder what all your woofers could do if they were all working 100% in the lower registers! With the small array in the hotel room, you could see visibly that the upper drivers were not moving as much as the lower ones. Maybe with your larger array it wouldn't be so pronounced?

At any rate, they look crazy good and I'm wondering if I'll hear them in Southern, New Jersey when you fire them up!

TomZ

[Kevin K.]

Thanks for the kind words Fellas!

I should have been more specific when asking for good Demo CD's. John's suggestions was what I had in mind, something with good sound effects and or imaging to demonstrate with. As for music, like you guys said, it's more of a personal taste thing and I doubt we would find something that everyone would agree on. After reviewing the Recommended test tracks link Sydney provided, it looks like several of my favorites were recommended by other members; Eagles, Dire Straits, Fleetwood Mac, Pink Floyd.

No run time on these yet Sydney. But you do bring up a good point, I wonder how long it will take for the woofers to break-in/loosen up so to speak. Since the arrays are shaded, I'm guessing it will happen in stages, bottom bank first, followed by each subsequent bank.

[Derekj]

Beautiful! Well done Kevin.

[---k---]

Wow. Amazing work.

[Millstonemike]

I tend to play from my current play list

+1. It will allow you to ascertain performance quicker by playing what you already know.

They look stunning.

[Sydney]

They turned out very nice - ( how much run time on them? ).
As far as test material - there is gobs on Recommended Test Tracks/Recordings Sticky
I tend to play from my current play list

[jhollander]

Looks great. Telarc Sampler five plus has some good explosions and cannon fire.

[Kevin K.]

It was a long day but I feel like I made some good progress. One of the cabinets is completely finished, the other will follow in a couple of days. Plan on spending tomorrow learning how to use the Omni-Mic. Once I have some good measurements from the first speaker, I'll send those to Rick so he can start doing his thing and in the meantime I will go back to work on the second cabinet.

Today consisted of lots of testing to confirm I have everything wired right and to make sure all the drivers are good. I did a "Rub and Buzz" test on all of the tweeters, one out of the 40 failed. The test sample had an Fs of 875hz, the one that failed showed over 1450hz. All of the others were within 5-10% of the original. I ordered a couple of extra tweeters so no big deal. Performed the "Rub and Buzz" test on the woofers twice. Once before installing and once after installing, they all passed with no problems. After all of the woofers were installed, used a AA battery to check each bank and confirm the drivers were in phase, everything was right. Still need to do a phase check on the tweeters but don't have any reason to suspect anything is wrong.

Part of what took so long today was "poor planning" on my part. I made the decision this last week to change from Phillip's wood screws to Allen head machine screws to mount the drivers. Because of this, 100 t-nuts had to be installed the hard way and that took a while. To me, it was worth it, I love the look of these screws with the drivers.

Here's some pics. Yep, they were all taken with the camera on the phone, it's all I've got. I'll try to put a real camera in the budget later this year. Anyway, the phone isn't to blame for one of the characteristics of the speakers. The Sapele can almost appear to change hues depending on where you are standing and how much light is on it. If it has very little light on it, it looks reddish brown. If it has a lot of light on it, it looks more orange. I love it!! This first photo shows exactly what I'm describing, they appear to change colors as you move from the bottom to the top of the photo.




I took pictures in two different rooms, my office and the conference room. The pics above were in the conference room with no flash, the pics that follow this were taken in my office (which has a couple of lights out right now) so the flash was used to offset how dark it was.





I've tried about everything to get a good picture of the Karelian baffles, not much luck. It's difficult to get a good shot of it with out the glare taking away from it. The Karelian is quite stunning up close. This pic also show the screws I decided on. Wish they had done a better job on the black plating but it will have to do.



That's about it for this weekend fellas. Hopefully I can post some measurements of the finished speakers by next weekend. I'm dying to hear these fire up and this next week is going to be like one gigantic tease, all I can do is look at em!

If any of you guys have suggestions for good demo CD's, let me know please. Rick is trying to get me that track Don played last year at MWAF of the prop plane. Wish I never would have heard that on Don's CBT's, it's what started me down this path months ago.

[Kevin K.]

Evidence the end of the build is close, very close! That late Christmas present finally arrived.



Enclosures are done for the most part, just need to fluff and install Acousta-Stuf , then the drivers. Shading boards are built and ready to be installed. Still need to build the harnesses from the amp to the speakers, that shouldn't take long.

This weekend will consist of running a few test to confirm everything on my end is right, rub and buzz, impedance, and then some sweeps. Will be working with Rick on and off over the next week to finalize the programming on the DSP. With a little luck (fingers crossed), these may actually get fired up and roaring by next weekend. Will post final pics of the enclosures later this weekend once the drivers are installed and will follow that up with the measurements once they are completed.

Was thinking about recording these playing a few different songs once everything was worked out but I don't have any idea what is needed to create a high quality audio recording for YouTube. Does it take specialty equipment? And if so, wouldn't it still only be as good as what the viewer is listening to it with amp and speaker wise?

More updates soon fellas!

[Kevin K.]

Looking great Kevin. That veneer is beautiful, can't wait to see and hear these this summer! =)

Thanks Javad! I'm getting really close to the finish line. Was hoping to spray the lacquer this weekend but we're not coming out of the 40's here in Texas. Next weekend looks better, highs in the upper 60's. Not gonna take a chance on messing them up with this much work already in em. Looking forward to seeing what you bring to this year's MWAF as well!

[JavadS]

Looking great Kevin. That veneer is beautiful, can't wait to see and hear these this summer! =)

[Squidspeak]

Please share, I'm all ears. I did pick up some Sherwin Williams Precat Lacquer for this project. It's the T77 F37. I know multiple coats of this can be applied, sanded, applied and sanded but I just thought it might still be faster to apply the grain filler first. Thanks.

Hi Kevin, Sherwin Williams, Valspar and Cambell Coatings all have a full range of finishing products. both solvent base and waterbourne . Grain filling aside most of these products can be done in a 48 hr. time period start to finish.

[donradick]

I know exactly what you mean. I applied it with a cloth and yes, there were some areas that didn't lay down nice and flat because it was drying so fast. Wasn't to concerned about it since most of it would be sanded or scraped off when applying the grain filler. After this next coat of BLO dries, I will spray the sealcoat on prior to the lacquer. Do you have a compressor and spray gun? I sprayed it on the Silverbacks and it worked pretty good for me. I like spraying for the exact reason you mentioned, nice and flat. Just have to get accustomed to spraying to avoid the runs. It's better to shoot many light coats instead of one heavy one.

That's what I thought, a spray rig for shellac is best. Thanks K