Adventures In Transmission Line Loudspeakers

Graham Slee wrote: Here is my idea for a TL for the Alpair 7. I wish I was good at woodwork! (hint)

Graham has the TL terminus (port or TL open end) on the back of the cabinet.
With the exception of the TL terminus location,
  This is very similar to the Radford S.90 as shown here... http://www.t-linespeakers.org/classics/radford.html   ...
     and the Bailey found here...    http://www.mh-audio.nl/bailey_tml.asp  ...


Here is another idea with the port NOT on the front or back...  http://www.mh-audio.nl/TML.asp  ...
 BUT on the TOP ! with only 1 fold in the TL.

The calculators on the mh-audio.nl site I found are good for a very rough approximation only... getting into the "ballpark". Some box size adjustments are still needed here.

HINT:
There may be other calculators that are a closer approximation to Martin J. King's and Dr A.R. Bailey's designs.

There are many speaker designs on the DIY websites... all types.
But, as with many other things, there are also many misdirected ideas as well.

I find the FH3 to have a very strong following and it has been designed with very close approximation to an
accepted design methodology.
(You will find many vague references like the one I just gave in this topic of TLs. Many that have the knowledge
 do not wish to dishonor or violate copyrights of others when making confirming statements. There are so many theories and factual evidences.)

The following is quoted from ... http://www.frugal-horn.com/ ...
"An estimated 1,000+ Frugel-Horn Mk3 have been built by the diy hifi community. FH3 been shown to work with a wide variety of drivers. The FH3 has been followed by a larger Frugel-Horn XL and smaller Frugel-Horn Lite. Independent cottage industry Flat-pak manufacture and bespoke finished Frugel-Horns has started up in Canada (North America), UK, Australia, & The Netherlands. More are being encouraged."

Note that the FH3 is the middle model. The FH XL being larger and the FH Lite being smaller.


Edited by BAK - 31 Dec 2016 at 12:08am

Drewan77 wrote: Graham Slee wrote: Headline: Genesis, Carpet Crawlers blows Graham Slee's socks off  (or on the LH side floor.... blew his brains out )

 All that was left is his shoes !!!!

Having further thoughts about my prototype idea, I think it better to have a removeable side than a removeable baffle. This will mean adjusting the dimensions of the pipe depths to make them uniform because there would no longer be the battens to hold the baffle on. Also I guess the slight taper might be a hindrance to tuning, so it needs to be constant. Hopefully Stefan hasn't started making the boxes...

Some TL designers reckon the Vas has a bearing on the performance and the air mass of the line should be Vas or Vas x 0.7. The volume of the box as it stands is about 2.5 times the driver's Vas.

Making the box smaller would shorten the pipe which needs to be 1.2m (48") to tune to 70 Hz at 1/4 wavelength.

Perhaps the solution would be to stick further thicknesses of MDF on the inside - this would certainly reduce the volume, or maybe the design should be started over?

Here we need the opinion of the specialist (over to you Stefan).

Ah, the things you find surfing...

http://audiojudgement.com/speaker-baffle-design-and-diffraction/

Now I understand baffle-step.

Put quite simply the distance between the speaker and the edge of the cabinet will defract at some frequency increasing output above that frequency. In crossover design baffle step compensation is used to combat the increased output. Another way to reduce this boost in output is to cover the baffle with felt...

So here's why the LS35A have a felt surround to the tweeter, and why my hobby felt (see earlier photo) did make an audible difference, and I was not kidding myself.

So, to get minimal upper frequency boost the baffle should be non-existent, and so I am basically making a Teletubbies speaker!

So are the response plots of the Alpair 7 made on a baffle or not? And if so, what was the baffle dimensions? Without such info we are all in the dark.