Kleos - Dipole Line Array

[Johnloudb]

Okay, here is the facts:

Inspiration for this speaker started in this thread ( https://www.htguide.com/forum/showth...t=31848&page=1 ). Drivers are six Usher 8137A 8", BG-RD50 Planar Mid, and 6-8 BG-NEO3 tweeters. Crossover will be discrete JFET active crossover, I think, unless I decide to go tube. Probably passive tweeter/mid crossover.

My speaker is progressing, slowly, as is my usual pace. I have two baffles cut like that shown below. I named it Kleos, meaning glory, and hope the name will rub off on it. ;x(



Here is the walnut veneer I'm thinking about, 2 sheets:
http://www.cabinetparts.com/m/flexib...r/FLWALNUT3X8/

Round over, started -



I started some round over work and then thought maybe I should put the veneer on first. The veneer won't cover the round overs so I think it would be easier to put the veneer on the flat surface and then do the round overs?

I plan to use contact cement to glue the veneer on. Where can I get blue tape, to prevent tear outs?

Any veneer advice is welcome.

[ClosetSciFiGeek]

Blue "Painter's tape" is available at any home improvement store or Walmart(the evil that is in America).

[ThomasW]

Blue "Painter's tape" is available at any home improvement store or Walmart(the evil that is in America).

Correct but it has no special properties that help prevent router tearout.

I'm not aware of any special tape for this purpose

[Johnloudb]

Okay, I guess I had the wrong idea about it helping with tear out. So far have had no problems with tear out, so it will probably be fine - fingers crossed.

[Hank]

:W Just use lots of that 3M blue painters tape - you'll notice the audible effect

[JonMarsh]

And Hank will thank you kindly for your patronage.

[Johnloudb]

:W Just use lots of that 3M blue painters tape - you'll notice the audible effect

No Worries Hank, when I start with the finish you'll see lots of 3M blue tape! Hey, I may even tape the drivers in place, you know, for better sound. :T

[Johnloudb]

Things are moving along, slowly. But can see the light in the distance. All the chamfering is done, most of the sanding, and I've just about completed all the round over work on the Baffles.



These 2.5" 3M Stikit sanding blocks, with 3M Stikit sand paper are awesome and fit inside all the cutouts in my baffle. The round front is great for sanding inside the holes. I got two so I didn't have to change out sand paper to change the grit. I found them at Amazon. I read one review where he made a special point to order a bunch of these for himself and all his woodworking friends when he visited the US.



One almost finished baffle.



The base with Veneer applied.

[Johnloudb]

Well, I did kind of a boo-boo on my speaker project and I feel a bit ill.





My plan was to trim the veneer with the router round over bit. I thought I should look like the base below. I the round over of the corner after applying veneer.



But, since I did the round over before hand, it wouldn't trim the veneer. So I lowered the bit the thickness of the veneer and it cut it back farther than I expected.

Sooo ... I can't think of any option other than finish the job with the router. So it won't look exactly like I had planned but may still be okay.

I plan on finishing it with linseed oil, and then a clear polyurethane over that.

I know baltic birch doesn't take stain very well. Has anyone used linseed oil on on BB?

I may just paint the round overs black where the BB is exposed, but I'm nervous that I'll screw that up too. :cry:

I could always veneer over the round overs too, but not sure how I would do that without messing up. :cry:

Oh well, you hope for perfection and try for perfection ... :cry:

[Johnloudb]

Well, now that I'm over the shock I see that it's not that bad. Just 3/16th inch wider than the base round over, so it's not really a big deal I guess.

Here's the aluminum used for stiffening up the speaker.



It will be screwed on to the back like shown below.



And that's where I'm at for now. It's too cold to do veneer work or a finish now. So, I may start work on the active crossover. I may get one speaker together and take some measurements before putting a finish on it.

First snow just over a week ago. Thought the pear tree looked nice against the snow.

[cjd]

That's patch-able.

[Johnloudb]

Hi Chris, Sounds like you've had experience with this.

I'm glad you said that, though. I thought it would look funny with a patch but I guess if I'm careful it may blend in okay.

Then I'll get a metal straight edge and use box cutters to trim the veneer around the round over, the right way, instead of using the router.

[Amphiprion]

Crossover will be discrete JFET active crossover, I think, unless I decide to go tube.

Noooooo! I am going to task myself with making you an op-amp convert

Beautiful project btw. I think the panels are turning out great and will look fine with the way you plan to route the edges. My active speaker project is so banal in comparison it makes me envious....

[Hank]

These 2.5" 3M Stikit sanding blocks, with 3M Stikit sand paper are awesome...

I love this guy! Lookin' good, John! A little TLC with a veneer patch and no one will notice after they're finished. How do you plan to brace the baffles to the base?

[Johnloudb]

Noooooo! I am going to task myself with making you an op-amp convert

Beautiful project btw. I think the panels are turning out great and will look fine with the way you plan to route the edges. My active speaker project is so banal in comparison it makes me envious....

Thanks Mark! Well, I'm not really anti op-amp. Op-amps have lower overall distortion and maybe good op-amps are more "transparent." But, I think the overall system needs to have a few good overtones!

Your speaker project is really nice too Mark, just a bit smaller. I may just quit speaker building after this experience. It better sound good.

I love this guy! Lookin' good, John! A little TLC with a veneer patch and no one will notice after they're finished.

Hang on Hank, I haven't even mentioned the 3M 30NF contact cement I'm using for this project. I was a bit worried when I only had enough cement left to put one coat on the baffle and veneer. Usually people recommend two. But it holds strong ... this stuff just won't let go!

How do you plan to brace the baffles to the base?

I'm still trying to figure that out unfortunately. I think I'm going to use two 1-1/4" X 4" X ~40" boards laminated together. Similar to what Chuck did but I'll have two supports - one on each side. I'll route a 1/2" wide slit on the end, so it will attach to the aluminum angle with quarter inch bolts and silicone glue.

That's the direction I'm pointing right now anyway.

[Amphiprion]

Thanks Mark! Well, I'm not really anti op-amp. Op-amps have lower overall distortion and maybe good op-amps are more "transparent." But, I think the overall system needs to have a few good overtones!

So we'll design in a ring modulator Right now I am looking at the OPA1644 quad unit that TI came out with in the last year. Looks like a really nice unit. I don't know of any other quad parts out there that might compare. They advertise greater than 120db channel separation on both the dual and quad parts, distortion is just nonexistent, device quiescent current is a scant 1.8ma instead of the typical 5-10 for the usual suspects (OPA2134, NE5532), rail to rail output, etc etc. Might be a winner...

And keep it up with the 3M stuff guys, my stock hasn't been doing to well this past month. Need to get that revenue up

[JimS]

Looking good :T

I went with the "slimming" look of black roundovers with stained front . . .

PS - method was easy: finish the baffle veneer, apply your favorite blue tape in a reasonably straight line (use paper to cover the center of the baffle so no overspray) and spray the edges. I used truck bed liner and surprisingly had no bleedthough under the tape and ended up with very crisp lines

Apologies for the low-res pic, but gives you the idea

[Johnloudb]

Thanks Jim. That's pretty looking looking speaker!

I plan on keeping the outside roundovers of mine veneered, but not the opening between the woofers and midrange. So, at least that part will match the base.

I kind of like the all natural look of the baltic birch roundovers on this. I'll have to try finishing some test pieces, to see how it's going to look first though.

[1Michael]

LoL, you call that a boo boo :rofl: :rofl: Come over to my house and I will show you what real boo boos look like :rofl: Whats a half inch off here and there anyways...

[Johnloudb]

Well, I feel better now! :B

[Johnloudb]

I've been stalled on this project since it got cold out, and I can't veneer or finish, so I'm thinking about what to do about a tweeter.

Anyway, I'm consindering a $500.00 Raal tweeter or a line array of 6 B-G NEO3 tweets. I'm putting a space between the baffle and tweeter to prevent diffraction problems and increase off axis dispersion. The center to center spacing between the mids and tweets would be 7.5 to 8.5 inches, and crossover around 5kHz.

The tweeters will also be set back almost an inch. Of course, the tweeter is closer to the listener. I haven't calculated anything yet but I think by just adjusting the toe in of the speaker, I could get the tweeters and mids time aligned. We only have one listening chair in the room except when my mom and dad watch a movie together, rarely.

So, listening off axis doesn't have to be perfect.

Anyway, I'm leaning toward the Neo3 cause of cost and it can be used dipole.

Welcome any thoughts/concerns as this is my first speaker design.

[Johnloudb]

Opps .. the second drawing above is upside down.

Well, I think I'll be going with 6 neo3 tweets. I've got a couple of them and it looks like a row of them will mount easily to aluminum angle on each side.

I take the silence as conformation that I'm on the right track. Anyway, could be March before I can get this together.

[Saurav]

These might be stupid questions, but there are a couple of things I don't understand.

What are the two vertical slots for? Are you putting 2 of the RD planar drivers on each side?

Are the Neo3 tweeters going to be run dipole as well? I assume they are. By pushing them off the edge of the baffle like that, I think you will maximize dipole cancellation to the sides. The baffle width looks pretty close to running those drivers nude, and there are a few of us who've tried that here on HTG and on DIYAudio. You get nice even off-axis dispersion, at the cost of a fairly rolled-off on-axis response, and a somewhat deep notch somewhere in the 7-10kHz range depending on how wide your baffle is, and whether you're using the PDR version of the tweeter. Not a show stopper, but something to keep in mind, it'll need slightly more work in the XO.

Also, by having the tweeters further away from the mids, and a high crossover, are you setting yourself up for horizontal comb filtering? I have no idea, and maybe above 5kHz it doesn't matter.

It's entirely possible I've misunderstood what you're doing here, and this entire post is irrelevant

[Johnloudb]

Thanks for the input Saurav. The opening in the middle will just be open space (no RD50), so all the drivers have there "own space" so to speak.

I think the RD50 works well with an 8.5" baffle given reports from others as well as B-G's own speaker which is also 8.5" wide. So I think I'm okay there.

Good to know about the tweeter issues. I may increase the width of the tweeter baffle a bit. Can't make it very wide though. I will experiment with different configurations once I start taking measurements.

[Saurav]

Ah, I see, so you get some sound wrapping around the RD50 panel. That's clever

Experimenting with tweeter baffle shapes before you commit to a final one is a good idea. I agree, making it too wide will probably negate the whole point of going dipole. You could also try a tapered baffle, that will spread out the dipole corner frequency a bit. Aleksander from RAAL had some interesting comments about the RAAL dipole tweeter in a recent thread on DIY Audio. He went with a 'pear' shaped baffle for his tweeter for similar reasons.

[Johnloudb]

Ah, I see, so you get some sound wrapping around the RD50 panel. That's clever

I was going to take credit for that ... but I have no idea what I'm doing really. Jon M. mentioned putting a space between the mids and woofers to prevent the woofers from "pushing" on the mids, and it also just seemed like a good idea to have a space there to keep the baffle width of the mid closer to what's "ideal" for this driver. Now you're telling me about dipole cancelation from the sound wrapping around. Okay so that reduces sound emanating from the sides of the speakers, as I understand.

So, I feel fortunate that I'm stumbling around in the right direction.

Okay, it's been a cool and rainy spring and early summer here. It may have broke 75 degrees yesterday, not sure.

I've got to get this sucker done! Yesterday, I trimmed the veneer around the opening between the woofer and mid, and it looks nice, except were I screwed up. So, I'm going to patch that part now.

Still, waffling on how to support these things. I think maybe just build a couple supports out of laminated birch ply.

[JonMarsh]

I was going to take credit for that ... but I have no idea what I'm doing really. Jon M. mentioned putting a space between the mids and woofers to prevent the woofers from "pushing" on the mids, and it also just seemed like a good idea to have a space there to keep the baffle width of the mid closer to what's "ideal" for this driver. Now you're telling me about dipole cancelation from the sound wrapping around. Okay so that reduces sound emanating from the sides of the speakers, as I understand.

So, I feel fortunate that I'm stumbling around in the right direction.

Okay, it's been a cool and rainy spring and early summer here. It may have broke 75 degrees yesterday, not sure.

I've got to get this sucker done! Yesterday, I trimmed the veneer around the opening between the woofer and mid, and it looks nice, except were I screwed up. So, I'm going to patch that part now.

Still, waffling on how to support these things. I think maybe just build a couple supports out of laminated birch ply.

Steady progress, John. It's good to see I'm not the only person that has trouble finishing a project in just a year... Of course, my problem is that they seem to stretch out to two plus years- we're approaching the two year anniversary of the start of the Ardents. Keep us posted...

[Johnloudb]

Steady progress, John. It's good to see I'm not the only person that has trouble finishing a project in just a year... Of course, my problem is that they seem to stretch out to two plus years- we're approaching the two year anniversary of the start of the Ardents. Keep us posted...

Yeah, progress is what it's all about ... isn't it? :scratchhead: I am itching to get this done, and the weather is better so I have no more excuses. I hope to keep the posts coming and have something playing in 4-6 weeks.

I look forward to seeing the Ardents with the Scan woofer upgrade. I'm sure those will be real special.

[JonMarsh]

Yeah, progress is what it's all about ... isn't it? :scratchhead: I am itching to get this done, and the weather is better so I have no more excuses. I hope to keep the posts coming and have something playing in 4-6 weeks.

I look forward to seeing the Ardents with the Scan woofer upgrade. I'm sure those will be real special.

4 to 6 weeks sounds good!

I've got to get out of this travel mode I've been in lately, particularly flying all day on Sunday to get to the East Coast. Got few more comping up like that (at least) through early August.

Was hoping to take a long weekend for the 4th Holiday weekend, but that got killed to fly out to the East Coast to interview some AE candidates on Friday the 1st. Been trying to hire two new AE's for about four months now, not having much luck finding the right skill set combinations. Of course, I could say that the two marketing managers are hoping to get full blown Mozarts (all my analog power conversion design skills, plus programming including DSP experience), whereas in their respective market's our product position and reputation are unlikely to attract more than a Salieri.




Unfortunately, we're yet to find someone that has the AC-DC design knowledge and insight purely on the analog side... and all the candidates I've interviewed to date have MSEE, some most or all of their PhD work done. So I'd be real happy to find a Salieri at this point! Would make my life quite a bit easier...

[Johnloudb]

Well, I hope you find a Salieri soon. No one should have to put up with the kind of work load you do.

[Hank]

Yep, we're all worried that Jon may crack at any moment. Jon, if you find any analog knowledge depth, hire it - not many left out there.

Go for it John! Need any more blue painter's tape? :W

[JonMarsh]

Hey Hank,

I stocked up on the blue painter's tape pretty seriously back in February- unfortunately, the living room is still a disaster with the furniture pulled in, everything draped, and only two walls painted- no progress since mid February!

I'm off to Raleigh/Durham today via LAX and Houston to interview a candidate tomorrow. Wish me luck... he looks to be well educated on DC-DC power conversion, but the position needs a guy with experience in AC-DC including power factor correction and bi-directional converters (going from high voltage EV battery stack to standard stack), and general purpose AC-DC support. Probably a square peg for a pentagonal or hexagonal hole...

Good news is it looks like I may get to have some fun with a Class D project and SMPS for it using our newest MOSFETs. Went over the preliminary proposal with my manager Tuesday, and how I proposed to do some initial comparisons and evaluations of our new 200V FETs in a power stage; this could lead to a full on design with two development forks; one to interface with a proposed modulator/controller from our Forte Class D team in Munich, the other a four pole phase shift self oscillating design just implemented quasi-discretely - you know, a handful of IC's collected together ad hoc for the task at hand- at least I do have what I believe is an excellent driver product from Silicon Labs in their Si824x family; will also use that in a new bridge less PFC concept I'm working on that's a spin off of our OBC demo (on board battery charger for electric vehicle). Hey, at least it will give me something useful to do with my HP8903B and my other audio power test gear...

Now, I just have to help the PL21 guys hire someone so I can get free of that 30-40% commitment on top of my normal job/department.

The rest of this fiscal year is going to be BSC. And that doesn't stand for baffle step correction. Already way to much travel committed to, but at least I'm building up my United status again, as the combined UA/Continental flys a lot more places I need to go.

Have a great holiday weekend, guys!!

[Hank]

You too - relax with a bottle of top shelf tequila.

[Johnloudb]

Go for it John! Need any more blue painter's tape? :W

Hi Hank, sorry for the late reply, have had some problems last several days and haven't been on my computer. No, I'm well stocked up on blue painter's tape!

Is this blue enough for you?



BTW, I'm afraid I'll be spending the next 4-6 weeks trying to scrape off the some residual 3M contact cement around the roundover. Sanding hasn't worked because it just sands the wood around it. A knife cuts into the wood cause it's a curved surface.

Well, I wouldn't have it any other way though. There's not much to scrape off, but got to get it off. I will also read the label and see what method they recommend for removal.

Here is the patch. Will be visible up close but it's the best I could do.

[cjd]

Can you use a scraper to clean up any of the residual? A scraper will for sure be helpful to blend that patch in - it'll be almost invisible even up close once finished.

[Hank]

John, that's the loveliest blue to my eyes, and the red is the best red. Sorry about the boo-boo. Do try a scraper on it as cjd suggested. They're called cabinet scrapers. Here's a couple from the Rockler site: http://www.rockler.com/product.cfm?page=19725

[Hank]

Mark H:

Right now I am looking at the OPA1644 quad unit that TI came out with in the last year. Looks like a really nice unit. I don't know of any other quad parts out there that might compare. They advertise greater than 120db channel separation on both the dual and quad parts, distortion is just nonexistent, device quiescent current is a scant 1.8ma instead of the typical 5-10 for the usual suspects (OPA2134, NE5532), rail to rail output, etc etc. Might be a winner...

Hey Kid, how's your op amp work coming along? When is your next Austin trip?

[Johnloudb]

Can you use a scraper to clean up any of the residual? A scraper will for sure be helpful to blend that patch in - it'll be almost invisible even up close once finished.

Thanks Chris and Hank, I'll get a scraper and try that.

[Hank]

John, I hope the scraper helped. Any other progress for us lurkers?

[Johnloudb]

Yeah, I've been working on it. I started painting the back got 2 more coats left. I have the scraper but haven't tried it yet. After I paint the back I'll attach the aluminum angle with screws and silicone sealant. First got to drill a couple holes in the rail for attaching to the wood supports.

Then I'll see how the scraper works out, and put a linseed oil finish over the whole thing. Then a polyurethane coat over that. Oh, yeah got to find something to polish the aluminum. Anybody got suggestions that? Actually I've got to do that before attaching the aluminum to the baffle.

I've decided to get a local CNC shop to supply and cut the rest of the wood, for the supports and the base, or I won't get it done by the end of August as I plan to.

Appreciate the bump ... just the kind of motivation I need.

John

[JohnA]

Oh, yeah got to find something to polish the aluminum. Anybody got suggestions that? Actually I've got to do that before attaching the aluminum to the baffle.

Simichrome

http://www.competitionchemicals.com/simichrome/

Any motorcycle shop in your area will probably have it.

[Johnloudb]

Thank you JohnA! Looks like that will do it.

[Hank]

Way to go, John - progress! After you polish the aluminum, clean it (denatured alcohol?) and immediately spray it with lacquer or poly so it won't start to dull from aluminum oxide. Thought: why shiny? Why not have 'em black anodized?

[Johnloudb]

Way to go, John - progress! After you polish the aluminum, clean it (denatured alcohol?) and immediately spray it with lacquer or poly so it won't start to dull from aluminum oxide. Thought: why shiny? Why not have 'em black anodized?

Well, it would cost more to get them anodized. I'm not sure about the polish either. Looks like it gets really shiny. Maybe just a coat of polyurethane would be a better fit. I found that sanding the brown paint gives the paint a nice weathered look, and much more attractive than the plane brown color. I'll post a picture when I get a chance.

So, it'll be sanding after last coat ... then linseed oil, and then poly. And maybe just poly over the aluminum.

John

[Hank]

Okay, John, here's your motivational bump of the week. I'm a supporter, man.
(No, Jon, NOT athletic).