SpeakerTalk

[speakerguru]

I'm feeling capriciously provocative 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.

[ColinR]

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]

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

What are the pros / cons of the transmission design in sonic terms ?

[DrBoar]

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.

. 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.

[proffski]

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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I contend that for a nation to try to tax itself into prosperity is like a
man standing in a bucket and trying to lift himself up by the handle.
-Winston Churchill

[speakerman19422]

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.

[proffski]

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!
_________________
I contend that for a nation to try to tax itself into prosperity is like a
man standing in a bucket and trying to lift himself up by the handle.
-Winston Churchill

[speakerguru]

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

[proffski]

Almost 17 metres I'd say, or 56 feet in English, but we all knew that.
Any allowances for temperature, humidity & long wool stuffing?
_________________
I contend that for a nation to try to tax itself into prosperity is like a
man standing in a bucket and trying to lift himself up by the handle.
-Winston Churchill

[SaSi]

[proffski]

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!
_________________
I contend that for a nation to try to tax itself into prosperity is like a
man standing in a bucket and trying to lift himself up by the handle.
-Winston Churchill

[speakerman19422]

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.

[proffski]

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

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

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/
_________________
I contend that for a nation to try to tax itself into prosperity is like a
man standing in a bucket and trying to lift himself up by the handle.
-Winston Churchill

[audiolabtower]

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.

[proffski]