[Teflon]

Depends what you mean by "loading" on the back. I think of a horn as more like an OB - in that the sound from the back of the cone is still heard. But with a sealed box, aperiodic or TL the idea, for the most part, is not to hear what comes out the back of the cone. In fact, I think with a horn you effectively have a 2-way speaker, higher frequencies from the cone, lower frequencies from the horn mouth - it tells you more about the enclosure than it tells you about your drivers.

[mightym]

Depends what you mean by "loading" on the back.

I just meant that right now they are in an OB.  That means the only " load " they see is the air in front and back of the driver.  The Designer described the Dallas II as a hybrid BLH/Transmission Line, having atributes of both, and using the characteristics of both to achieve the desired BW in reproduction.

The mouth of the horn isn't big enough, nor is the horn path long enough to play as low as needed, so the TL loading takes over below the horn.  the shape and size of the chamber directly behind the driver helps to make it all happen, and acts as a sort of mechanical low pass filter.

That is the "loading" I was referring to.

John

[mightym]

Short update:

The voids are all filled, I've been experimenting with how to glue the felt damping into the bends, and have satisfied myself that the method I wish to use is both efficacious, and mechanically sound ( I am using 2 different types of contact cement, brush-on for the cabinet, and spray-on for the felt.  I didn't want to distort the felt by trying to brush the cement on to the back of pre-cut pieces. ).  They appear to be compatible.  Once the last side is on I won't be able to reach the bends...

With any luck the last side of the boxes will get the glue today/this weekend.

John

[Teflon]

Let's have some photo's before the sides go on then 

p.s. perhaps you can screw the sides on, making it airtight with some kind of temporary gasket or something - you get to try it out and listen for a week or so before you 'finalize' it with glue.

[mightym]

perhaps you can screw the sides on, making it airtight with some kind of temporary gasket or something - you get to try it out and listen for a week or so before you 'finalize' it with glue.

You have an excellent idea there Teflon, I was trying to Not install the drivers until I had the cabinets finished.  I am afraid I will neglect to complete them otherwise.  I've been using a combination of glue/brads thus far in the build, it's not really conducive to just putting some screws in, and playing.  I'm working on a solution for that, a temporary seal for the horn path, and clamping the side on for some testing.

I'm trying to figure out how to seal without having to pick a lot of adhesive off before I can then glue the final side on....

I have a couple of rolls of foam weatherstrip tape, I usually use for speaker gaskets, that stuff will not peel off, I would end up picking bits of it off the gluing surfaces for weeks before I can close them up.  I'm open to suggestions.

I have considered using the foam that builders lay out on the slab under the studwall in the new construction around here.  They use it as a thermal break and seal.  I think I can trim it down to  a width that will work.  I don't think I can get any this weekend though.

Like I said, I'm open to suggestions.

John

[rjbond3rd]

Clamps work for damping purposes in my limited experience, even if the seal isn't perfect.  As soon as you tighten up the clamps, at one point you'll hear the bass kick in (I was playing music at a low volume at the time, and this was a BiB).

The Ron Clarke designs (at least the Austin, but from his writings, it seems all of them) damp the back of the driver's cone so well that as you lower the driver into place (to screw it in), if you are playing music at the time (low volume), you will see the cone travel quite a bit but it then stops as the frame snaps into the sealed position. And the bass suddenly appears.  At least that has been my experience as an Austin tinkerer (Serenechaos was the builder).

[Teflon]

rjbond3rd - I've only read about Rob Clarke from what I've found on the Frugal Horn website - if you have more material you can point me to please let me know.

mightym - not sure about that builders foam, it's very rigid and no doubt it'll be a right mess if you try trimming it to something like a thin layer. Kids 'playdo' might work, it's not supposed to be greay so it won't stain the wood but it will squish out a bit when you clamp it. Weather strip foam as you suggested might be good, just don't peel off the backing strip that exposes the glue. Maybe even corrugated coardboard with the 'holes' parallel to the edges.

[mightym]

Thanks Robert, Teflon for replying.

I don't think just clamping will do, but the mention of the playdough gave me an inspiration, involving playdough, and saran wrap...

I'll let you know how it goes.

John

PS:  Teflon, look up the old " Fullrange Forum", it's archived on the web.  Ron was  regular contributor there.

[mightym]

Wow, I didn't realize it had been so long since I updated the progress on the build.  I didn't use Playdough....

I made " ghetto gaskets " instead.  I stole a roll of plastic wrap that the better half had stuck in a drawer of the kitchen, it's wider (18") than the standard stuff in the cabinet with the foil, wax paper, etc.  The Plastic wrap was applied with the handyman's helper, ( you "Red Green" fans know what that is! ) and pulled smooth over the already prepared surfaces of the side panel, and the cabinet body.  An inexpensive tube of Silicone sealer then gave it's all for the cause, as I squeezed out a single bead that followed the edges of the horn path from mouth to driver chamber.  After waiting for the bead to partially cure ( skin over a bit so it wouldn't all squeeze out ) the sides were lowered into place and clamped.  My able assistant then helped me lower these behemoths to the floor.  Drivers installed, I hooked up the speakers cables and held my breath as I tweaked the loud knob on the amp.  I was rewarded with Bass from these drivers which had heretofore only played in an OB to break them in.  I'm still ecstatic this morning, and my ears are ringing a bit too  .  I guess I got a little wild with the volume ( I've already got Tinitus anyway, but the ringing is a bit more pronounced this AM ). 

All that aside, current progress is: Cabinets ready to close, wired, voids filled, outside of bends damped with thin felt, mating surfaces milled as close to flat as I can make them.

No pictures were taken last night, my phone was in the house...  I'm very pleased with what I heard last night, almost all the harshness I heard when I first started the break-in process has abated, the sound was detailed, fairly well balanced ( considering that the work table was where I needed to be, and I had to either stand right in front of them, or 10' away behind the work table ).  I am again stoked to work on this project, and get on to the finishing stages.  Now I have to remove the drivers and start the tweaking process there too.  Damping the frames, and magnet, coating the cones, possibly adding a phase plug, and grounding the frame.

Still lots of work to do....

John

[Teflon]

That's good news mightym, we're looking forward to some photos.

[rjbond3rd]

I might have a spare set of phase plugs from a pair of FE206E which were damaged in shipping (the drivers, not the phase plugs).  They are buried in the closet, assuming they really exist...

Hi Teflon, I don't have great links to Ron Clark's writings but as John says, he posted a lot at the fullrange forum back when that was the "it" place, and he also posted at a couple others which I found by Googling for the Austin.  You can definitely piece together the whole story. 

Short version is that he's an engineer and he loves horns.   When work was slow, he built a cab at his work, placed sensors into different parts, took pressure measurements, and gradually refined his math.  He has certain ideas about wavefronts, e.g. that you want to preserve the energy to reduce losses due to friction, and you want the wave to stay or at least return to a certain shape.

His last known project is a design called the Houston, which he (I think) says he gave up on (but he would also hint that he'd take it out of the drawer now and then, and revisit it).

I read a description of it as one FE206E that has "three actions," and I could never understand how this works but the driver faces up, points into a deflector and divides into two paths.  One path returns sound to the user (off the deflector).  The  third action is a BLH.  I could not quite picture the second action.  I would love to see a diagram if anyone knows of one.

Ron, my apologies if my summary is way off base!  My recap is surely flawed.

[chrisby]

I might have a spare set of phase plugs from a pair of FE206E which were damaged in shipping (the drivers, not the phase plugs).  They are buried in the closet, assuming they really exist...

Hi Teflon, I don't have great links to Ron Clark's writings but as John says, he posted a lot at the fullrange forum back when that was the "it" place, and he also posted at a couple others which I found by Googling for the Austin.  You can definitely piece together the whole story. 

Short version is that he's an engineer and he loves horns.   When work was slow, he built a cab at his work, placed sensors into different parts, took pressure measurements, and gradually refined his math.  He has certain ideas about wavefronts, e.g. that you want to preserve the energy to reduce losses due to friction, and you want the wave to stay or at least return to a certain shape.

His last known project is a design called the Houston, which he (I think) says he gave up on (but he would also hint that he'd take it out of the drawer now and then, and revisit it).

I read a description of it as one FE206E that has "three actions," and I could never understand how this works but the driver faces up, points into a deflector and divides into two paths.  One path returns sound to the user (off the deflector).  The  third action is a BLH.  I could not quite picture the second action.  I would love to see a diagram if anyone knows of one.

Ron, my apologies if my summary is way off base!  My recap is surely flawed.

Ron has unfortunately been unheard from for quite a while now - unless I've missed something, for reasons not certain.

Given the time that has elapsed since we have heard from him, I think the above is as accurate a description as we're likely to get

[rjbond3rd]

Hi Chris,

I hope he is okay.  Did you ever see a sketch of the Houston?  Or hear a better verbal description?

[mightym]

Robert, what you described RE: the Houston's sound somewhat like the original Lowther Audiovector to me.  Which if you were going to call the Dallas II's a BLH ( though it's more than that by Ron's description ) would make the Audiovector a compound horn, I guess.

If you should happen to stumble across the phase plugs while you are looking for something else ( that's how it works for me anyway )....  I would be interested.  I planned to knock some up on my own, so they weren't high on the list of things to do to finish the Dallas II's.

I did stop at the friendly Electrical Wholesale supply house on the way home today and picked up several packages of Duct Seal to smooth the airflow over the back of the drivers, and damp the frames.  I do not think it will take more than a pound of the stuff to do the pair of drivers, but at $1.43 per.,  I bought extras for the next project.  The counterman wanted to know what I was doing with it.....so I told him.....didn't even get a strange look out of him, nor did his eyes glaze over.  Guess it wasn't the strangest story he'd heard today...

Nothing else to report at this time...I've been lazy the last 2 nights watching PBS.  I hope to put in some time over the weekend, and get the cabs buttoned up, and the finishing started.  while finishes are drying I'll work on the driver tweaks.

John

PS, and off the subject, after hearing these for the first time the other night, now I'd like to think more about trying something like these as front Mains for an HT, with a pr of Lowther Ace style cabs for the surrounds, with the Fostex's too...Might be interesting, but I got no idea where to find a 5.1 SET amp....

[chrisby]

PS, and off the subject, after hearing these for the first time the other night, now I'd like to think more about trying something like these as front Mains for an HT, with a pr of Lowther Ace style cabs for the surrounds, with the Fostex's too...Might be interesting, but I got no idea where to find a 5.1 SET amp....

Steve's building block method?

http://www.decware.com/newsite/zkit2.htm

[mightym]

I'm sure that all 4 people who have been following along on this build/adventure all think that I've defied gravity and flown off into the ether, what with no action on the thread in so long.......

In my defense, I had to change positions at work, or find a new job, as the economy was not allowing me to make enough to cover my nut on a monthly basis, and not looking any better anytime soon.  Meh, I did what I had to do.  This means that I'm no longer home, except on the weekends.  When I log 67+ hrs. in a 5 day period, and then go home, It'll take me a while to get back to where I can do anything but sleep on the weekends.

I did manage to get some work done on the Dallas II's,  not as much as I'd like, but the sides are on, the drivers have been duct-sealed to damp the baskets, and smooth airflow around the magnets.  I just came in from the shop, I've got an audio bud coming by tomorrow to play, and in the morning I'll re-assemble them so we can begin the critical listening phase.  I still plan more driver tweaks, including some home-made phase plugs ( I figured out how to machine my own with a jig and my router. ). and some kind of coating on the cone,and whizzer.

I apologize for the lack of pictures,  I'll try to get one to post tomorrow while the are set up to play with.

Hopefully the next update, will not be so long in coming...

John

[mightym]

Steve's building block method?

http://www.decware.com/newsite/zkit2.htm

Interesting idea, now does anyone make a 5.1 surround pre-amp, with all the current processing bells and whistles too?

Another off topic comment, I picked up an old JBL autosound Sub the other day, and simmed a TH for it in Hornresp.  so I've got the sub covered already now, just need to pick up a plate amp for it....and build the horn......another horn? ( groan ).

John

[rjbond3rd]

Hi John,  I hear you on the economy.  My story is pretty much the same.

I am super psyched for your listening impressions!

[mightym]

I had a wonderful day today, listening to, lets see, Junior Brown, Stevie Ray Vaughn, Miles Davis, Diana Krall, Chris Botie, and a host of others.

While the cabinets are not finished, the drivers not tweaked to the Nth degree, I really liked the way these things sounded.  I can see where some would be happy to listen to these without a sub-woofer, that's how we did it today.  Nice dynamics, smooth presentation, good imaging with a little extra toe-in.  Any 8" widebander is going to beam some...  overall very pleased.  Detail is good, those lightweight cones are fast, fast, fast.  Even though I've got close to 100 hrs on the drivers now, I sometimes detected a tiny bit of raggedness in the highs.  They've smoothed out so much since they were first fed an audio signal, but there is still room for improvement.  My solution will probably entail more hours of time, and some driver tweaking.  Cone coating, felt on the inside of the frame legs, grounding the frame, and the "Big Kahuna" a phase plug are all on the list of things to do.

Since this is ostensibly a wide bandwidth board here, I have to comment on the other speakers we listened to today.  They were OB, with EV 12SPB(?), over Dayton 15" IB woofers on a common baffle, with a Dayton sub amp.  After fiddling to  match the Sub's amp's XO to my KT-88 SET, this was a very tuneful set-up.  I can see why some like the EV's so much, they are excellent drivers, especially considering they were manufactured in the 1960's probably.  Very detailed, we didn't even put a tweeter on them, though if we had I wouldn't have crossed it in anywhere under 10-12K, very, very nice drivers.

Alas we were too busy to take pictures, didn't even think about it until everything was torn down and put away, car packed etc.

Next up in the epic saga of my build is pulling the drivers for tweaking, and so I can make lots of dust finishing the horns.  I will try to get some photos up  with the next post ( don't it piss you off when these guys build stuff, and don't take any pics?  I know it does me   ).

John 

[squalor]

Hi mightym and fellow full-rangers, this is my first post here. I've been out of the game for awhile and was never very knowledgeable when I was into audio. I'm in this thread because of a lost PM and Email exchange with mightym. I cobbled together a pair of Dallas II's a few years ago and still enjoy them.
I scanned thru this thread and have a few questions; pardon me if I missed the answers. What wood/material did you use to construct these ? What glue ? What did you use for speaker wire ? Do they have feet, spikes or a plinth to sit on ? What is your listening room like ? Can you corner-load these ? You said you only used kitty litter for the bottom void and used foam for the other voids, what kind of foam ? Did you listen to anything with a fast walking bass line like boogie or fast kick drum like a heavy rock song ?
Is anyone else in this thread thinking about building a set of these ?
Here's a pic of mine.