Articles, Brochures & Reviews, oh my!

A big part of this project has been trying to learn all I can about the original RSTL and RSTL-M. Through the generosity of others, most especially Nick Mellor from the UK, Allegro Sound, Falcon Acoustics and others (both documented and not), I’ve been able to amass quite a collection of literature on the RSTLs. Here is a summary:

  • DIY Articles & papers
    • Klang & Ton / Dec 87-Jan 88 / German
    • Klang & Ton / ?? / Hifi Boxenheft Spezial Nr. 2 / German
    • ?? / ?? / Norwegian? / hifisentralen.no forum
    • A+O Stuffing Instructions / ?? / German / private
  • Reviews
    • Gramophone / Dec 86 / English (UK)
    • Hi-Fi News & Record Review / Jul 88 / English (UK)
    • Stereophile / Dec 89 / English (USA)
    • Gramophone / Apr 96 / English (UK) – RSTL-M
  • White Papers
    • A Monitoring Approach to Loudspeaker Design / May 87 / English (UK)
  • Brochures
    • TDL Brochure (6 pages) / 1988 / English (UK)
    • TDL Reference Series ‘M’ / 1995-6? / English (UK)
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Go deep!

In my previous post, I mentioned a discussion about this project on the diyAudio site. One comment referenced an analysis by Martin J. King (http://www.quarter-wave.com/), widely regarded to have the best transmission line modeling software available. He stated that Dr. King had found “Dalines” (what G. L. Augspurger calls “Pipe with Coupling Chamber” ?) inferior to designs. I did find this reference on diyAudio that supports his statement.

Without further ado, here is my model of the Tang Band W8Q-1071F in a RSTL line. Could there be something better? Maybe. Does this strike me as a configuration that will have deep bass? Yes. Am I worried about the dip at 100Hz? Not really – right now I expect I’ll have an active crossover at or below 100Hz, so I’m not at all concerned. Should I go full passive, I’ll have to review my stuffing plans.

Image of TangBand response graph in RSTL

Simulation of TangBand behavior in the RSTL line

Why can’t it be Round?

It has been a long time again since I’ve posted. Two reasons. One, through the generosity of a visitor, I’ve been digesting some much more detailed information about the original DIY version of the RSTL. When I get done with the translations and cleanup, I’ll post more about what I’ve learned here.

Today though I’ll tell you about a(nother) project that took WAY longer than it should have – creating the countersink template for the woofers. Oh why oh why can’t they be nice and round like most of the other drivers I’ve worked with over the years? Even the line array of ribbons I used in my last speaker were nothing compared to this guy.

I used “Easy Driver Flush-Mounting” in the June 2001 audioXpress as my guide. Suffice it to say Mr. Buike was facing far fewer issues with the Focal woofer in his example than I did with the Tang Band’s irregular shape. The basic idea is to use a flush-trimming bit with a bottom-mounted guide to create a template 1/2″ larger than the driver:

Image of Routing first template

Using router table, trim bit and driver to make 1/2 inch “oversize” template

Note the taped-on plastic bag to keep dust out of the driver. Also note the trim bit protruding just to the left of the driver, so it can use the edge of the driver as a guide. I’m going to skip a WHOLE BUNCH of stuff that turned out to be hard here and jump to the next good part. When it is all done, you’re left with a template that is the right shape except it is 1/2″ bigger than the driver on all sides (the width of the trim bit):

Image of completed first template

Completed first “oversize” template

Finally, cut this template down by 3/8″ per side to leave a nice 1/8″ border around the driver:

Image of completed template

Completed template, with driver for comparison

Notice I left a large border all the way around the cutout, both to leave room to clamp the template and to support the router. A lesson learned (over and over) the hard way.

Crosscut sled project from Hell

Every big project seems to have something that just doesn’t go well. At all. Well, at least one something. For me, it has been building a crosscut sled for the new table saw. It took me three tries and it still has a variety of problems. For now though, it will work and I can do most of the things I need to with it. It isn’t as pretty as the one on the cover of Fine Woodworking magazine:

Picture of crosscut sled

Crosscut sled sitting on table saw

However it (finally) works pretty well and is sturdier than my old one. The main problem now is that I need to make cross cuts 45″ long. While I can do this by supporting the piece to the right of the sled, currently there is no way to make repeatable cuts the way I can for short pieces by clamping a scrap against the back fence at the right distance. I’m considering now how to make some sort of extension to allow making these repeatable 45″ cuts, as there are many of them in a RSTL.

Getting a Woody!

Boy, it has been over a month since I’ve posted! Most of the past month focused on adding to my woodworking tools. I’ll go into more details in future posts, but here is a quick overview of all the great new (and used) equipment I’ve added:

Used table saw with router table extension

Craigslist table saw with router table extension

 

Delta dust collector

Delta dust collector for table saw and router table

 

Router table and new clamps

With two routers, I can leave one in the router table while keeping my DeWalt plunge router for hand use. I picked up a bunch of new clamps too.

I’ve also had to spend time building a cross-cut sled, a push stick, a 135 degree angle jig… More about these in a future post.

The Holy Grail found?

Through DIY Audio member Duck-Twacy’s generosity and zelfbouwaudio.nl member Sark’s vision, I finally have a copy of the Klang+Ton article on the DIY version of the RSTL from the December 1987/January 1988 issue. That was the first thing I learned – this article was in a single issue. I’d just assumed Klang+Ton was a monthly and it was a two-part article. Way back in 2003 Duck-Twacy posted on the DIY Audio forum that he had the article and was willing to scan for interested parties. This sounded promising, but this post was over 9 years old. Would he still be reachable on DIY Audio? Would he still have this now 24+-year-old magazine?

The answer to the first question is yes, Duck-Twacy still is reachable via the DIY Audio site some 9 years later. Amazingly, he responded overnight to my request for the scan! Did he actually still have the magazine? It didn’t sound like it, but his colleague Sark on the zelfbouwaudio.nl forum had the foresight and vision to scan all of his Klang+Ton issues, presumably just for circumstances like this. They made the entire issue available to me.

Gentlemen, thank you both. I’ve been searching for this article for a long time, so I can’t tell you how much I appreciate you making it available to me!