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There's no such thing as a transmission line speaker
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speakerguru
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PostPosted: Wed May 23, 2007 11:20 am    Post subject: There's no such thing as a transmission line speaker Reply with quote

I'm feeling capriciously provocative Twisted Evil today and the forum seems ever so quiet, so here goes;

A so-called "transmission line" speaker is the same as a reflex cabinet but by using a pipe instead of a helmholz resonator (as the resonant device) you are giving yourself more problems with the suppression of strong overtones in the pipe than you would have had with the higher mode resonances in a regular box.
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ColinR
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PostPosted: Fri May 25, 2007 3:22 pm    Post subject: Reply with quote

Yes and no, forget Mathcad and Augspurger & King.

Your reflex analogue will apply to LNB, PMC and pipe designs.

IMF TLS80, RSPM and Webb R50's less so.

Not with Webb Lentek or triangulated Bailey or Rogers Pro9TL.

The more irregular the cross-section and the more tapered the pipe the more chance you have of getting some reinforcement at it's end and not a series of Helmholz solutions along the line length.
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suffolk2
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PostPosted: Fri Jun 15, 2007 9:57 am    Post subject: Reply with quote

I have had the bailey design and do have the rega xel transmission line speakers, and other ported designs and the difference I have noticed is with the transmission line design, the bass is more controlled and has more ambiance.

This a non technical analysis Very Happy

What are the pros / cons of the transmission design in sonic terms ?
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DrBoar
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PostPosted: Mon Jun 18, 2007 2:04 pm    Post subject: Reply with quote

A TLS can be either a quarter wave resonator and then have a lightly damped pipe. The fundamental resonanse will give high radiation resistance ( large sound output for a small cone motion) over a small range say 1/3 to 1/2 octave very much like the bass reflex box.

Or the TLS can have an extremly damped pipe whos purpose is to loose all the back radiation. Web and others. I really do not see the use of this latter design. What the benefit would be compared to a wellbraced closed box with a lot of resistive damping material in it.

I have heard 1/4 wave pipes getting strong bass at 40 Hz from a 4" driver.

Very Happy . The snag is that a 50 Hz pipe do give a huge boost from 40 to 60 Hz at the most then the little guy is on its own and will fail terribly from 60 Hz up towards 150 Hz or so.

Bassreflex is a good thing but it steep slopes 24dB/oct makes it sesitive to changes is the resonance system. Hot/cold voice coil changing the Qes, amplitude dependent compliance etc.

How sensitive 1/4 wave pipes are Voigts or TLS I have yet to figure out.

They all are closed boxes that use a resonator to gain bass output over a limited frequency range. Both can be badly designed....


I have heard some really nice TLS but they may have sounded equaly good in well braced over damped bass reflexes for all I know. Wink
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proffski
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PostPosted: Sun Feb 28, 2010 9:37 pm    Post subject: Bristol Hi-Fi Show 2010. Reply with quote

Just returned from our once yearly pilgrimage to the Bristol Hi-Fi Show.
My favourite stands are obviously KEF, Spendor, Wilson Benesch, Meridian, and many others... read on gentle folk.

Now I'm an easy going amicable sort of chap who is quite normal until he finds some old KEF loudspeakers, IMF or the derivatives. Then I go all sentimental and gooey like de-vulcanised rubber! Then very possessive, MINE!

One of the stands we always head for is PMC, the Professional Monitoring Company who still make TL or Labyrinth loudspeakers.
I care not a fig as to whether the alleged TL is truly a real TL or just a labyrinth; I like the sound of the beasts if they are well designed in the 1st place!

Yes I am quite aware of the similarities on paper between the reflex, the ABR and the “Transmission Line” as well as the pros & cons (he ducks from the stones, rocks and abuse)…

I have described on at least two occasions the design and building as well as tuning of my ½ wavelength ‘Labyrinth” utilising a KEF B139, B110B and Decca Ribbon back in the 1970s. You can all breathe easy, I’m not about to repeat again… yet.

PMC get their TLs or Labyrinths right, forget the theoretical negatives, group delay, phase anomalies in general and so on. In a room of sufficient volume they sound in perfect control, speed, and no boom or resonances whatsoever.

Today we were not disappointed as we were treated to one of their smaller designs, the cute IB2i, it was magnificent!
Gosh these beauties sure knew how to sing, they reproduced everything thrown at them with confidence, clarity and cohesiveness. Stunning!

Whist not having the transparency of the best electrostatics they made up with their ability to go loud or quiet with no perceivable dynamic compression at all, transients were vertical, and the LF extension so clean, no bass doubling, no nasty overhang, and no subwoofer needed!
Yes, I liked them!!! http://www.pmc-speakers.com/product.php?mode=view&pid=141
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speakerman19422
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PostPosted: Sat Mar 27, 2010 2:35 am    Post subject: t-lines Reply with quote

I have been listening to my various Fried designs for 30 years this year.. The bass and midrange sounds more natural in t-lines. I built t-line mid bass enclosre with Fried Oem drivers that were in aperiodic damped cabinets originally. The differnce in sound and new detail never heard in old cabinets are amazing. The bass at line terminus gives a very wide soundstage. Fried claimed a pair produced a 40 foot wide soundstage. I would not go back to any other type of enclosure unless required to by law.
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proffski
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PostPosted: Sat Mar 27, 2010 11:49 am    Post subject: Labyrynth Thingies Reply with quote

Agreed on most points, but there again I have also heard TLs or whatever the correct technical term is which sounded strange. Whatever the technical explanation, good ones are bl**dy good! Smile
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speakerguru
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PostPosted: Mon Mar 29, 2010 9:00 am    Post subject: Reply with quote

Guys, you've hijacked this thread somwhat just to say that you like the sound of some "TL" speakers. That's not and never was the point.

If you measure a good sounding "TL" you will very likely find that it is a very leaky closed box or a reflex with a very low box resonance frequency. What you will not find is a low frequency transmission line. Any realistic sized box will be a collection of "lumped" components, i.e. acoustic mass, acoustic compliance and various acoustic losses. You can work out for yourselves what the wavelength is at 20Hz and ~340m/s
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proffski
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PostPosted: Mon Mar 29, 2010 9:54 am    Post subject: Reply with quote

Almost 17 metres I'd say, or 56 feet in English, but we all knew that.
Any allowances for temperature, humidity & long wool stuffing? Cool
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SaSi
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PostPosted: Tue Mar 30, 2010 8:09 pm    Post subject: Reply with quote

speakerguru wrote:
...If you measure a good sounding "TL" you will very likely find that it is a very leaky closed box or a reflex with a very low box resonance frequency. What you will not find is a low frequency transmission line. Any realistic sized box will be a collection of "lumped" components, i.e. acoustic mass, acoustic compliance and various acoustic losses. You can work out for yourselves what the wavelength is at 20Hz and ~340m/s

I have calculated that a pair of compound B300 in a 190lt enclosure with two 52cm pipes of 10cm diameter each tunes flat down to 19Hz. And WinISD models group delay to rival a Q=0,7 sealed box down to 40Hz or so.

I'm not sure if this could be considered to be a TL but should I decide that 2x10cm pipes are inadequate, switching to a 30cm pipe calculates 2.4m length for the same tuning frequency of 20Hz , something that seems to enter the quarter wave territory for a frequency much higher than the goal tuning frequency of 20Hz.

And if the 30cm pipe remains unstuffed - as it "should" then lot's of interesting things can happen as it should start behaving like a badly built transmission line.
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proffski
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PostPosted: Tue Mar 30, 2010 11:52 pm    Post subject: Reply with quote

Up to a point I agree with Speakerguru, he is an acomplished engineer, I am an amateur and blinkered to suit my views.

Sadly the term TL has become generic, as for example:

1. Anything which is a vacuum cleaner = Hoover.
2. Public address system in bus or railway station = Tannoy

Hence a derivative of the acoustic labyrinth by default becomes a TL
We know or at least I hope we know the difference but the name has stuck... So most of us visualise a tube with a speaker at one end rightly or wrongly as a TL.
It is a shame that it is easier to explain and understand a transmission line in RF terms!

Going back to the speed of sound in air, did not Mr Bailey work out that it can drop down by 50% in a correctly damped pipe?

I see that the bass driver Bowers & Wilkins £55,000 Nautilus is described as "Tube Loaded". http://www.bowers-wilkins.co.uk/display.aspx?infid=1729&sc=hf

As much as I love the sound of some pipe loaded loudspeakers I still stand by my comments in previous postings.

The best bass (not to be confused with deepest)I have ever heard, or the most accurate from a moving coil transducer was on the B&W DM70, sadly lacking in power handling. Probably on the same level but different has to be Yamaha NS1000.

Panels are a different thing, and a friends twin pairs of Quads 2905s driven by the Musical Fidelity 1KW behemoth take some beating...

Oh, and by far the worst tube or labyrinth or TL or quarter wave loaded loudspeakers I have ever heard by far were a few variants on the awful Kapellmeister! Shocked
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speakerman19422
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PostPosted: Wed Mar 31, 2010 1:21 am    Post subject: Reply with quote

I am quoting some of Bud Fried's brochure.[Transmission line free flow filter progressively absorb energy with frequency, along a long path. At the very lowest frequencies, the mass of air in the line is acoustically added to the mass of the driver diaphram, forming an equivalent acoustic air mass of enormous size. Thus the line reproduces crisply, without the time lags of resonant system, avoids cabinet relection effects, presents a much flatter impedance to the amplifier for greater power transfer and forms a plane source propagator. Transmission lines are better than other enclosures. They have zero ambient pressure, so that drivers can react rapidly]. I would rather listen to my t-lines then ported or closed box. Forget the math t-lines sound more like live music. Even cheap 4$ to 10$ woofers sound better in t-lines then the other enclosures. Using my Digital sound pressure meter that only goes down to 31.5 hz the response is almost ruler flat on Stereophile Test CD 3 bass tracks from 200Hz to 31.5Hz, -8db at 25 Hz.- 12db at 20Hz all at 1 meter..Room acoustics play some part but the whole back of my house is open from family room to kitchen. My 10" sub woofer t-line enckosures are 37"H by 14"W by 23.75"D using 1" high density particle board.
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proffski
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PostPosted: Wed May 26, 2010 11:00 pm    Post subject: Having a Laugh! Reply with quote

Some of the very worst loudspeakers I ever heard at a Hi-Fi show.
Allegedly made in the UK... Shocked

These were at the Bristol show circa 2006 I think, but my brain has been trying to erase the incident from memory! Shocked

It looks and it sounded like a car eliptical loudspeaker in a rather nice enclosure. Available on ePrey if you are desperate and only £2K for the black piano finish version.
Worth a good look around the links if you are down and need cheering up, see if you can understand the hype better than I did.

http://www.worldsbestloudspeakers.com/

http://www.resolution-loudspeakers.co.uk/tnt_review.html

http://www.resolution-loudspeakers.co.uk/
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audiolabtower
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PostPosted: Wed May 26, 2010 11:23 pm    Post subject: Reply with quote

is that patent real? I'm absolutely gobsmacked you could patent a pipe enclosure in 2004 !!! Unless the patent is for the "ceramic reflectors" or some such other rubbish.
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proffski
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PostPosted: Thu May 27, 2010 12:09 am    Post subject: Reply with quote

audiolabtower wrote:
is that patent real? I'm absolutely gobsmacked you could patent a pipe enclosure in 2004 !!! Unless the patent is for the "ceramic reflectors" or some such other rubbish.


Beats me, the car speakers looks nice for a car speaker though. Smile
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