TunDar Transmission Line Mini Tower
Last Update: Dec 4, 2009 Lou's Home Page
"Don't be scared der, boy, it's yust the sound of tundar..." -- Iver the Carpenter
When I was a kid, one of my father's friends was an old Swedish carpenter named Iver. He was one of the best craftsman I ever met. (Ever see a guy hang a solid core door, with three hinges, using just a hammer, chisel, hand drill and screwdriver?) I remember being at his house during major monsoon storm. With his accent, he told me the lightning caused "TunDar". Sounded right to me for these.

Vifa D25-AG35-06 Tang Band W5-1685


I have far too many drivers in the garage for my life expectancy (unless I make 90!). I wanted to build a pair of quality speakers for the neurosurgeon who saved my wife last year with a very risky operation. Turns out he's a major electronics geek, and wanted something for a pair of 50 watt tube monoblocks. So I set out to make something special with stock on hand.

Back when they first came out, I thought the TangBand underhung drivers were pricey, but very intriguing. I bought a pair a year or so ago when they had a reasonable introductory price. From the initial model, it looked like they might go pretty low for a 5" driver, with 6mm of Xmax. Once it was measured and anointed by St. Zaph, I thought it would show up in a few designs. But it never did. So I thought I'd do some thing with the pair of W5-1685 I had bought.

Now what to use for a tweeter? I looked through the inventory and found a pair of Vifa D25 aluminum domes. I consider the D25 to be the Virginia Madsen of tweeters, been around for awhile but still mighty fine!. With the somewhat low woofer placement, I thought these would match up well and give me some flexibility in design. Kind of old school meets new school.

Since the Tang Band already needed a relatively large box, I thought I might try a transmission line. I engaged the help of of the ever generous Curt Campbell in coming up with a TL box. Based on a 10:1 taper ratio, this is what he/we came up with A 24" box is kind of awkward (a bit tall and top heavy for stands). So I turned it into a small floor stander by adding another foot to the bottom.

Cabinet Construction

I decided to go all 3/4 MDF with biscuit joints. Curt told me I'd be tweaking the design by adding & withdrawing stuffing for the front part of the line. Combine that with the Tangband's huge mass (6-8 lbs), a thick cast flange and I knew I needed hurricane nuts and a thicker baffle. So I laminated a layer of 3/8 mdf to the woofer area. I used 10-32 hurricane nuts with a dab of construction adhesive, and matching 1.25" cap screws I had on hand. (I did have to ream the holes in the driver flange a bit). I used mostly Titebond and clamps to assemble the box. At the top of the mitered "wedge", and for joining the sealed bottom I used PL construction adhesive and my brad nailer. I drilled three small holes in the bottom panel to pass wires to the drivers. The crossover will go into the base chamber.

It took about three measurement passes to figure out how much dacron batting to use. (I bought a garbage bag full of scraps for $5 from a local upholsterer) I would up with a bit of mattress topper on the underside of the top and on the wedge directly behind the woofer. I packed the rest of the front wedge with dacron. It's hard to describe how much I put in there, but the area below the drivers is really packed.

Crossover Design

It took me another three design passes to come up with a listenable crossover. I used too long a gate time when measuring and had a hard time sorting out ground bounce from internal reflections of the TL. (Duh, I should have done a nearfield splice on the woofer, but that never occurred to me for a 2 way.) The "final" crossover is a relatively simple coil/cap on the woofer. (The TangBand is a 4 ohm driver BTW).

For the tweeter I would up with a cap/coil/cap setup. The crossover is about 2600 Hz, with effectively 3rd order acoustic slopes on both drivers. (You'll have to take my word on that, the measurements would scare you off if you saw them!) I used 18ga air coil for the woofer, 20 ga on the tweeter. Overall I would call this a 6 ohm nominal speaker. (I will post "final" measurements at a later time)

The D25 is still a top notch tweeter with all the sizzle you could want. Run them too hot and they'll sound a bit edgy on poorly mastered material. I played with a variety of padding and thought 20 ohms was about right. (YMMV). I went through three iterations on adding and removing dacron. Finally left it loose along the sides of the driver, removed it from behind -- just leaving the mattress topper behind the woofer..

Listening Impressions

As you get older, you can go as hard, or go as long, or go as often -- you just can't go as long and as hard and as often. -- Pasquale

Sometimes you fire up a pair of boxes, and you know they are just "right". I knew that with the Shticks, so too with the TunDars. Just enough magic smoke to make them something special. These have a very refined and detailed presentation, slightly forward with a real shimmer to the top end. Now I think this TangBand is a legitimate competitor for some of the ScanSpeak 5" drivers. Lovely vocals, piano, strings & brass. Forgiving with bad recordings, but capable of revealing nuances in well mastered discs. The TL does a nice balanced job of covering the whole bass spectrum. No boom, just slam. Very broad and spacious soundstage even in the man-cave. (I ran these analog thru my modified Oppo CD player and the HK154 receiver)

This TangBand has a remarkable useable range for a small midwoofer. Thump + accurate midrange. They aren't particularly sensitive either (probably 82 db as designed). If you needed more dB from theses perhaps an MTM (series wired) would be a strong candidate.

I still love the D25. (and I still have fantasies about Virgina Madsen) I might give a slight edge to Seas H1212, and the RS28 can run a bit lower, but this does such a nice job on percussion, and depth of detail , it deserves consideration in that class of tweeters.

The Shticks convinced me that you can get truly full range sound from a relatively petite box -- albeit at the expense of sensitivity. In that design, the HiVi's were the limiting factor. In the TunDars, the TL configuration definitely buys you some very solid low end. They have serious, clean bass down to the low 40's. (Remember this is one 5" driver) The trade off is here is driver excursion. (You can't beat the laws of physics!) With synth, techno, hip-hop or crap mastered rock you can bottom out the TangBands with 30-40 watts. At sub 98db levels, or for a smaller room, I doubt most older folks would find them lacking. For jazz, chamber, classical, or adult contemporary the TunDars have all the refinement, range and sophistication most discriminating listeners could ask for -- in a relatively small footprint. There just isn't a lot of volume. If you're a 20 something, turn-it-up-to-11, headbanger, these aren't for you.