I've seem offset drivers in OBs but not flip flopped FRs and woofers.  Perhaps you are on to a great audio discovery.

Lin has pointed me in another direction now. This Emerald Physics dipole thing has me wound up.
I made a mistake of looking at other EP speakers and saw something else of interest to me. Slide over for the pic, lots of white there!


This also looks doable.
So many options in life.
I'm getting ready to go to St. Louis to shop for wood.

Palomino, the tube is as easy as your nearby Lowe's. Sono tube for concrete footings. I'm thinking epoxy or bondo to cover any flaws, prime and paint.
Today I found a source for my wood slab needs. They had some nice slabs of spalted maple, walnut and several other species that were in the 24" + width range.

Or an open baffle line array...

So many ideas!
Better judgment has settled in, Before I spend $500 for a couple of hunks of really nice lumber, I'm going to experiment on some aspen wood 24X48x.75 panels that they sell at Lowe's for less than $30 a piece.
This way when I won't feel as bad when I screw up. This will also give me the option of moving the 8" driver around to figure out the best configuration.

Where did you end up on the drivers?  Tang Band/Alphas?  If so, how will you cross them or is that TBD?

A bunch of boxes arrived this evening. I've already unpacked everything and wired the speakers to a amp.
The low pass crossover is hooked up to one pair of the alpha's, not caring for what I'm hearing on that side right now.
No discernible bass at this time out of anything, I'm hoping that the baffles will fix that.

I roughed one out tonight. And when I say rough, I mean rough.
It is just a proof of concept at this point.
It does have bass, thank goodness.
I need to make them less deep.
Running the Alpha's full range right now.

VERY cool, Donnie! I'll be most interested to hear what you find is the optimal distance betw the Alphas. Keep us in the loop, will you?

Randy

Pal,

Just curious if you have tired running your Augies full range (by-passing the crossover completely).

My experience with the 15A was similar to yours using a 250hz crossover. When I eliminated the crossover completely the muddiness was gone.

My theory with regard to the muddiness. It's not the driver sounding bad but rather the brain detecting a disconnect between the 15A and the higher frequency driver (a lack of cohesion between the two as far as the brain is concerned).

When I run my 15a's full range the higher frequency driver just seems to float on top of everything from the 15A's. The 15A's present the brain with a cohesive Bass line from about 45hz to well over 1,000hz similar to what a Bass Guitar actually does.

In my case adding the crossover #1: sucked some life out of the music and #2: just seemed to create a transition issue that is a real red flag for the brain. I'm also wondering if the crossover introduces some signal time smearing which adds to the disconnect between low and high frequency drivers?

I used to take the approach: Why isn't this sounding good? More recently I've been taking the approach: Why isn't my brain buying this?

Donnie, even though the equal distances on the sides and above the TB may look nice, it really hurts OB sound.

DBC,

I do not recall it sounding bad when I ran the augies full range.  I can give that a try again just to see if its muddy.  

I can also measure it again to see if it jacks up the high bass/low mids.

DBC,

I tired it and it sounded horrible.  I didn't remember that and I figured it out.  My experiment before was with the augies supporting the monoliths. So with the single driver is unlistenable but with the monoliths it was ok.  I may toss the monos back in and see how I feel about it now that I have some experience with the single driver crossed to the augie.

That might explain why the examples Donnie posted earlier had such a wide spread.  At the time, I wondered why did they make them so deep?

Donnie,
I suppose you could also try offsetting the rear facing one from the front one in the left-right plane, just to get the magnets a field width or more apart.
That would takes some symmetry out of the look but from the front I don't think it would be noticeable.
Anyway, your experimentation will tell much more than my guesses!  LOL.

It's a good feeling to have them both assembled, eh?  I end up rushing something every time.  I'm like a little kid.

Very interested I your thoughts on the alphas running wide open with the tang bands.

I have been using a little eq in audirvana to tame a couple hot spots in the tang bands. Not a lot.  Now getting the best sound ever.

Hi Donnie,

My guess is that your two woofers as configured are really only doing the work of one. Would seem to me that the back wave off the front woofer is effectively Canceled Out by the front wave of the rear woofer. So in effect what your are hearing is the Front wave off the front woofer and the rear wave off the rear woofer (the equivalent of one woofer).

After you have listened for a while, you could test this theory by simply removing the rear panel & woofer. If my theory holds true then you should have about the same bass output with the one Woofer.

Quote:


Some thoughts. Based on my experience 3/4" thick baffle material is too unstable, it vibrates too easily. I can imagine that each speaker with twin baffles and twin 15" drivers are vibrating to some degree. If they are vibrating then they are producing sound separate from the drivers. So the baffles themselves become big speaker diaphragms. For proof of concept, 3/4" material is easy to work with but can have very negative effect on the sound quality.

Some of the perceived bass output you are hearing could be from the baffles themselves vibrating in harmony (in phase) with one another. Reversing phase on the rear driver may kill the bass since each baffle would be vibrating out of phase ????

You mention these things will shake the house. I suspect there is quite a bit of vibration being transmitted from the baffles to the floor and out to the side walls by virtue of them sitting directly on the floor. Only way to know for certain would be to sit them on isolation platforms.

I had a period where my floors & walls were vibrating. One would naturally assume this is due to sound waves from the speaker driver traveling through the air, hitting walls and exciting the room surfaces. I finally put the downfiring subs I used at the time on Isolation platforms and this eliminated floor & wall vibrations at high volumes.

Point being: if acoustic energy is being dispersed evenly out into the listening space in the form of sound waves, it's very difficult to make the floor & walls vibrate. On the other hand if you sit 4 Butt-Kickers on the floor (which the Alpha 15's basically are) then it's not too hard to see how the floor and walls would shake.

If your Baffles, Floor & Walls are all vibrating then they are producing sound independent of that coming out of the drivers themselves. Your Decware speakers are stout little suckers with materials and internal bracing specially designed to minimize cabinet ringing (not easy).

Quote:


I can tell you if your walls are vibrating the primary cause is not how loud you play. Rather it's the mechanical transfer of vibration from the speakers to your floor and out to the walls. Concrete is worse than conventional wood construction. Scroll down in this link and they discuss concrete floors:

http://www.htguys.com/news/2010/12/5/auralex-subdude-video-review.html

I have a pair of Klipsch RF7 mains that I drive with a 220 watt Peachtree integrated amp. I can easily achieve 100 db continuous with this combination. With subs & mains sitting on proper isolation platforms I have minimal floor & wall vibration. Remove the isolation platforms and the room vibrates causing a reduction in sound quality (mainly loss of clarity & definition).

I wouldn't worry about the way you have the woofers since they make a lot of bass together and very little (none) out of phase.

You think maybe the ground underneath the concrete damps it a wee bit.
I've never seen a driveway or road move like a suspension bridge no matter how windy (see link).

As always people disagree about what happens, why it happens, or if it even matters.

For two new machining centers we just put in at the factory that I work at, we used 160,00 lbs of steel and over 150 trucks of concrete in it's foundation. Maybe that is what I need to do for these speakers.
I'm going to try putting some water pipe foam insulation on the bottoms of the baffles and see what it does. Cheap, direct, and easy.

I'm really enjoying these speakers now.
Their sound is intoxicating.
Probably if I did any kind of testing they would measure way wrong.
But to my ears they sound pretty good, not as good as HR1's, but pretty good in their own way.
I'm going over to Lowe's in a bit to pick up some of those foam snakes that are used to insulate water pipes so I can see if decoupling them from the floor does anything .
Experimentation is fun.

Quote:


Have you noticed a change in the bass?  Since you already have the pad and carpet you may not be getting much extra isolation from the foam.  I never had much luck with foam type isolation on my solid wood supports and flooring.

I'm trying to work up the nerve to install the low pass filters into these speakers. Should I waste my time doing it?

Lin, the low pass filters are set at 100 hertz. I may just low pass the rear speaker.
And yes the soundstage sounds higher than I'm used to. It sounds maybe a foot higher than normal. I might need to drop my full range drivers a few inches.

12db.   http://www.parts-express.com/parts-express-100-hz-low-pass-8-ohm-crossover--266-...

There are some new developments to share on my OB project.
After waking up at the unprecedented early time of 2:30 am this morning instead of my usual 3:45, I found that I had a little time on my hands.
So I started experimenting with my low pass filters.
First idea tried was low passing the rear woofers. I really couldn't tell the difference, pointing out to me that maybe the rear woofer was redundant.
Second idea tried was low passing both front and back woofers. Something was missing, detail was lost and the soundstage constricted.
Third idea tried was just low passing the front woofer and unhooking the rears altogether, major mistake, everything went flat.
Fourth time was a charm, low passing the front and full ranging the rear. That was the secret. Wow, major soundstage everything sounding where I thought it should be, and depth where I've never had depth before. Another problem with the height of the soundstage also seems to have lowered itself 6". Lin called it right, I really need to listen to his advice closer.
So now onto version 2.0 of this project.
I have decided to build this as the pro's do it, not out of solid wood, but out of MDF and veneer on a interesting wood front.
The first quote for what wood I had in mind was almost $1800 without any machining done to it. That, my friends, is a chunk of money. If I were to spend that kind of money, I would just pony up the cash for some HR-1's and live in bliss for the rest of my life.
But with me being me, the challenge of building something outweighs rational thought.
So, now there is a order for some Red Gum veneer rushing through the vastness of cyberspace.
My CAD Monkey and I are going to Lowe's to buy a couple of sheets of MDF this week and some sort of harebrained project will begin again, using the lessons learned from the last few weeks of experimentation.
A couple of lessons learned are;
.750"  material is too thin, I'm going to laminate 2 pieces of .750" MDF for some thickness, I hope that it works.
The height of the full rangers might still need to be dropped a couple of inches so that I can take the riser out of the back baffle. People use 34" for a reason.
My wire routing needs to be looked at, I hate how sloppy it all looks.
I'm scared as hell about the veneering, it looks so easy on all of the youtube videos. For some reason I believe that it isn't as easy as a 10 minute instructional makes it look.
Oh well, onward and upward.

Palomino, These look pretty cool, nice and simple.
http://www.mockett.com/grommets-wire-management/wire-managers/wm28-2in-90.html

Version 2.0 of these speakers is about to begin. My CAD Monkey and I picked up a couple of sheets of .750" MDF the other day. Man is that stuff heavy, now I know why they don't make it in 1.5", it would take 3 men, 2 boys and possibly a trained seal to pick it up!
The plan is to saw some blanks out, drill some dowel holes in them and glue them together with Titebond 3 to get my 1.5" thickness.
After that I will start hacking the shapes out.
The veneering still has me a bit scared, but I will cross that raging river when I get to it. Other people do it, they can't all be smarter-better-more gooder than me, can they?
I'm in way too deep now, past the point of no return, might as well forge forward.

I now have the MDF laminated and getting the shapes roughed out.
MDF is a bit more difficult to cut than ply or the aspen that I have been cutting.
So everything is still moving forward. I still wish I had a clue of what I am doing..

Donnie,

Did you at least use a compass to draw out the circle first?

Zygi

I think you could save some time by using a 12 gauge and a file to clean up the edges.  Also I am concerned that your ear pieces may be capturing dust and allowing it to get in your head.  That said, if you actually cut a 10 or 12 inch hole with ___  amount of 3/16" drill holes, AND had the trooper spirit to do it twice, I'd like to buy you at least two beers, one for each speaker.

Steve

00

Hell Donnie…I'd buy you dinner the next time I'm in town….I think I recall you liking O'Charlies  ::) if I'm not mistaken.

Good one Steve!

Zygi

IME it is better and easier to live with ugly until the design proves its worth.

Progress report:
Back sides of the front baffle primed and sanded smoooooth.


Veneered front.


Front of both.



I've decided to shellac the veneer after trying out four or five different stains, amber shellac looks best to me.
The primed parts are going to be red.
A lot more work needs to be done!

Archie,
I used Danish oil and wax on my last project. I put some of the oil on a piece of scrap veneer yesterday, the oil hid some of the detail that the shellac brought out.

Painting the back sides of the front baffles this morning, Torii Red of course!
The veneered side is coming along with 3 coats of shellac out of more than likely 6 coats total.
Apply, dry, sand flat, apply, dry, sand flat......
It is getting to the point where I want to bolt these together and listen to them.
Patience is a virtue that I want right now!

A rectangular baffle with a plain jane flat top usually works best (see Decware-Spatial-PureAudio-etc); worst is a perfectly round baffle with the driver in the middle since the distance from the driver to the edge is the same in all directions.


How far apart are the woofers on your previous baffle?

A quick update. My OCD has kicked in and I keep putting finish on and sanding it off. I can't seem to satisfy myself.
I've already used a quart of shellac on the two veneered faces.
Weirdness continues !

What is the distance between baffles?

If my calculation is right that should work quite well with your baffle width.

DONE! Finally.
They are now playing in my fortified bunker.
First impressions? Not too bad, I need to mess with placement and stuff like that.
Lessons learned, lots of them. Veneering is tough to get right, I hope that next time it will be a little better, a little flatter and less bubbly.
I really need to get into spray painting to save me time sanding.
But that stuff is just fluff, the main thing is how they sound. More time with them will tell me if I just wasted 8 weekends and way more money that I'm willing to tell my wife.
Pictures:

Palomino,
I'm crossing only the front Alpha over at 100hz, 12db per octave . I haven't experimented with much at all yet. They just got wired up tonight.
They are heavy, there is almost 2 sheets of .75" MDF used on these two speakers!
The imaging seems to be pretty good as I listen while punching this in on my iPad .
I'm already planning my next two projects, a suitcase stereo for my sister and an extreme makeover of my "Rocker"  DM clones.
More to come.

Looks like there are a variety of width, height and driver placement designs. As I was reading and observing the thread I am wondering if designing a modular type of experimental board would allow you to move drivers and adjust width/height to dial it in by ear during listening tests. One question in my mind is there a maximum width that will negate any positive attributes of the open design? It seems the examples shown all have edges ending near or close to the radius of the driver. I own Legacy speakers and they have had the Whisper which uses bass drivers behind one another for at least 15 or more years now. Perhaps the angle of the front face allows a greater latitude of actual driver placement so it adds another aspect to the experiment.

Some guys do a wing design with cheap wood and piano hinges.  That way you can make them wider or thinner on the fly and because the wood is cheap, you can try different driver placement.

The Pure Audio design I did is somewhat modular in that I can swap out boards, but I had to commit to a width because of the frame.  I just looked at what others were doing in that area and settled on 23".

I hope to try a thinner, less expensive design with the Betsy and 15a drivers.  I'll still bi-amp.  Mine current ones take up a lot of room.

'As I'm punching this in Eric Clapton's Slowhand in hi-Rez is playing, sounding pretty damn good.'

I kinda eased into it. I started with a $100 driver in a winged design.  Then a $200 driver in a modular setup.

What I have is wonderful but I am interested in exploring how much of what I have now can I get in a less expensive design and then if I get some mad money, what can I do with a primo driver.

Donne, Palamino,

Thanks for the good suggestions. I have been kicking around ideas in my head and I am thinking about small portable OB units that can be placed close to the listener somewhat like a cross between headphones and speakers. This I am thinking will negate much of a rooms acoustical issues since it will be such a near field listening position. Using a sub for support on the low end. With proper positioning and quality drivers a dedicated listening room may not be necessary and very spouse friendly lol. Hmmm  wheels turning now.

Jeff,
Something like this?

Or these?


Or these?



Or maybe this?  http://gainphile.blogspot.com/2009/09/s11-ob-bookshelf-open-baffle-with-seas.htm...

So Jeff, What comes to mind to me would be something like a floor lamp with a small baffle attached.
Something like this type of lamp



Am I getting close to your vision?
One on either side of your chair.
Damn, I might have to make something like this.

I wanted to comment on something that I've noticed with my open baffles. They sound better with the windows open. Weird. I can't think of an explanation. They just sound more open and lifelike.
Maybe it is the smell of my rat bastard neighbor cooking on his grill?

Update:
After a month or so of playing I am very happy with my handiwork, at least sonically.
The sound has really started coming together, there is more than enough bass and I really love the soundstage.
Several of my friends that have listened to my speakers have commented on how nice they sound and how cool they look. I will temper their comments because none of my friends give a hoot about my strange obsession for listening to music.
Overall, I'm pretty happy with what I've done and it kept me off of the street for a good part of 8 weeks.
Lessons learned:
Work on the overall plan a little more, "winging it" only goes so far.
I need to work on my veneering skills, the next time will be a lot better.
Take my time, I got a little impatient towards the end of the project and it shows up in the little details that I let get by me.
But most importantly, make sure that you have fun. This is a hobby, not a job.  

Good read, thanks.