Transmission Line Build and Play

Hi

I am new to posting on this site, but thought that the project I am undertaking might be of interest to some of this site's members.

Together with a good friend of mine, I want to look a bit further into replacing conventional oil and mineral based absorption material with alternatives such as wood fibre, sheeps wool, hemp and other natural fibres.


As the title of this post suggests, we want to trial these materials in a transmission line speaker, constructed by us, from an IPL Acoustics kit (IPL M1TLm Ribbon Transmission Line).


We are aware that long haired wool has often been used to fine tune, but we want to look at the bigger picture of replacing the profiled foam that runs along the labyrinth with a natural alternative.



We don't want to do this just to provide a greener alternative, although that is good news too, we want to see if we can improve on the sound.


Neither of us had previously heard TL speakers before, but when we listened to them, at the kit supplier's home (Ivan @ IPL Acoustics) we were seriously impressed and both commented on the unique nature of their presentation.

The supplied kit comes with profiled foam and a small quantity of long haired wool, for fine tuning, so our intention is to build the speakers as per kit, with one small change. We will gasket (draught excluder) and screw one side panel to enable us to gain easy access for changing over the absorption materials.

To give a why to all of this, I part own a sheep wool business and have experimented with different types and quantities of wool in closed box and ported speakers. This has produced some interesting and quite unexpected (by us) results.

Both my friend and I, were astonished at the impact differing absorption materials have on balance, definition, imaging and timbre not just between synthetic and natural fibres, but between wools!

We will/are taking photos as we go to provide something a bit more interesting to look at than just text! Pics here Flickr: theacousticshepherd's Photostream


Have just glued outer box, less one side panel.
 
So you guys think this is a brand new, revolutionary idea?
You're not gertting much interest because folks have been thre and done that, and as stated previously, you're using vague "magazine" terms that have also been done before.

Folks will need some objective results to get interested, and even then it's still pretty ho-hum.


What a bizarre site! Don't know if I have just posted in the wrong section or whether a TL speaker build designed to experiment with alternative cab absorption is just to dull to attract any interest/comments on a DIY Audio site!?
 
So you guys think this is a brand new, revolutionary idea?
You're not gertting much interest because folks have been thre and done that, and as stated previously, you're using vague "magazine" terms that have also been done before.

Folks will need some objective results to get interested, and even then it's still pretty ho-hum.

That's fantastic news! Clearly we are not old enough or well versed enough to have come across this before.Could you perhaps point us in the direction of any of this info/data please? Would really help us out knowing what has gone before.
 

pkitt

Member
2009-02-24 12:32 am
Have you looked up George Augsperger? He developed alignment tables and software for modeling TLs using polyester fiber, fiberglass, and other materials for the stuffing. Martin King developed his TL modeling software and alignment tables based on polyester fiber effects. Maybe these two sources could be useful for your experimentation.
Paul

Nearly forgot, could you perhaps explain where and what?
 
Have you looked up George Augsperger? He developed alignment tables and software for modeling TLs using polyester fiber, fiberglass, and other materials for the stuffing. Martin King developed his TL modeling software and alignment tables based on polyester fiber effects. Maybe these two sources could be useful for your experimentation.
Paul

Thanks Paul, really appreciate your help. Do you happen to know if any of this is web based, or is this research paper based?

Cheers T
 

pkitt

Member
2009-02-24 12:32 am
Pete gave you the link to Martin's site, and I misspelled George's last name. It's Augspurger and I don't know that he has a site, but if you do a web search you should find links to bits and pieces of his work. He had TL modeling software for sale.
Paul

Thanks Paul, really appreciate your help. Do you happen to know if any of this is web based, or is this research paper based?

Cheers T
 

pkitt

Member
2009-02-24 12:32 am
This might also help: http://citeseerx.ist.psu.edu/viewdoc...=rep1&type=pdf

That link was referenced by Bill Fitzmaurice in his post in this thread at Parts Express Tech Talk forum:
Philips 10100-8 10" woofer replacement in Transmission Line cabinets

The linked document is quite long and covers a lot of territory, but maybe it will be useful to you (the PE thread is interesting in its own right).
Paul

Cheers Paul, I will definitely take a look.

Thanks to all for your suggestions (well most of them anyway) with your recommendations and the material I have found myself, I am now knee deep in electronic literature.

One last thing though, before I try and make sense of it all, without the availability of an anechoic chamber or expensive kit/software, has anyone any recommendations on methodology for obtaining meaningful measurements of the absorption/damping?

From my perspective I am happy continuing to listen and take notes, but given people's early comments about non vague measured results, if there is a budget method for achieving this then I'd really appreciate some info on this.