Transmission Line Speaker Cabinets for HiFi

[JazzGuitarGimp]

Back in the mid-70's, I was at a friend of a friend's house, and this guy had just built a pair of what he called Transmission Line speakers. They were volumous (as in large, not loud), and sounded very impressive. Yesterday, I got to thinking about that day, and how great the speakers sounded, and so I ventured over to Wikipedia to learn more. See here:

http://en.m.wikipedia.org/wiki/Transmis ... oudspeaker

One thing I learned, is the acronym TL is used when discussing this particular cabinet design. Which spurred another line of thought: the Electrovoice TL806 cabinet. Yet in looking at the construction plan for the TL806, it seems obvious that it is not a transmission line design. Funny that...

But I am curious, have any of you built or bought transmission lines speakers for HiFi? What are your thoughts?

[Cantplay]

I use a pair of modified 8" fostex full range in an onken style cabinet for my bedroom system.

Take a look at this: WWW.planet10-hifi.com

John

[rp]

A picture is worth a thousand words to those who may be unfamiliar:

Lou, are you asking about adapting their use to MI or wanting to build yourself some hifi? TLs and horns come from the birth of audio amplification when SE triodes ruled the earth. It was a way of getting the most volume, most linear sound out of a few watts, often you had 7-10W for a whole theater - 15-20Ws was like Carnegie Hall! IIRC TLs get around the damping problem you get with box speakers (acoustic suspension/ported). The early amps besides low power didn't have NFB, and as Williamson amps show up after the war you see TLs and horns start to fade and box speakers take over. The last picts shows someone moving his klipschorns (honey, look what I bought us!) you can see why they faded. Then with the '80s tube revival, and thanks to Japanese audio fetishists, you had SEs getting rediscovered and TLs and horns making comeback. Meadow Lark Audio (extinct now?) was offering modern compact TLS in the 90's.

Back to MI, an open back solves the dampening problem too and we don't care much about linearity, and as for getting volume out of a sealed 4x12 we now have Super Leads for that. But how about a TL for a Champ! 5C1? SE, low watts, no NFB - Do it, blow our minds!

Here's some quick surfing links if you're thinking hifi:

http://www.wilmslow-audio.co.uk/

Definitely google Lowther. They make full range drivers (think about it!) that allow you to avoid crossovers and that are maximized by a TL design. As cantplay mentioned Fostex makes cheaper full range drivers for TLs, yes Fostex is a pretty cool company. All theses full-range driver companies offer cabinet plans and then there are the infinite DIY blogs.

Horn Porn:

http://www.klipschupgrades.com/restorations.shtml

BTW the Klipsh were shaped that way as they were made to go into the corner and used the megaphone effect of the wall boundaries to mechanically help amplify, speakers and walls became one. Must be a bitch to tweak IMO.

My take: I don't think you can just step into the shallow end of the pool with a bathing cap and waddle around, TLs and SE amps are more about doing a cannonball into the deep end. It's not really about hooking up your $50 DVD/CD player and your old Sony stereo or even the 35W PP tube amp you built. If you have to pay someone to do your wood work and build your tube gear it's crazy money.

[Aurora]

The BW Nautilus is not a transmission line, rather a socalled terminated line, where the back energy is terminated acoustically resistive,- converted to heat, not reflected or put out in the open as in a TL.

[Bill Moore]

Back in the day, I had a friend who was playing with transmission line designs, and I got the idea to build one for my truck. I've forgotten the actual lengths I used of 4" PVC filled with dampening material, (my friend was in on the design). I used some decent quality 6 x 9 3 way speakers in a box that was sealed to the PVC array that filled the space behind the seat. (Had to be at least 8' of pipe for each driver).
Really a wild looking system, and had fairly decent bass response for the drivers I used!

[rp]

The BW Nautilus is not a transmission line, rather a socalled terminated line, where the back energy is terminated acoustically resistive,- converted to heat, not reflected or put out in the open as in a TL.

Ah! Wondered what happened at the end of the giant cochlea and those stacked vuvuzelas.

For myself if I ever ventured down this road I'd go for the a Lowther TL and the purity of a single crossover-less driver and an oh so dainty and precious pair of mono 2A3 SEs. Luckily, I have a guitar amp jones to keep me distracted.

[Aurora]

I forgot to say that lines are as such open to the room, but with so much damping that the soundwave is heavily damped with respect to the front output...

BillMore - without seeing the actual design, that sounds more like a acoustically damped pipe, better known as a resistive vent or aperiodic load....

[norburybrook]

the best and most common true transmission line speakers over here in the UK and EU are PMC. Thye're make a very professional studio series of monitors favoured by a lot of mastering engineers but also make a domestic range for home use.

http://pmc-speakers.com/


my mastering engineer uses them so I know them well


Marcus

[Bill Moore]

Tomato-tomoto, I don't know, the line was round instead of square as you have in a box.

[JazzGuitarGimp]

This is all very interesting.

rp, no, I'm not thinking about MI applications - HiFi only. I may buy some MDF and see if I can't render myself certifiably insane trying to get all the angles right.

I already have a pair of Bottlehead SET 2A3 monoblocks and I had been driving a pair of Realistic Mach Two's (15" 3-Way), but the foam surrounds on the woofers have rotted away.

Many, many years ago, I owned a pair of Klipsch La Scala's. I used them as PA speakers. I actually didn't realize they were designed as HiFi speakers. I'm kind of kicking myself in the pants for selling them. On well, another "the one that got away" story!

I've had my turntable and album collection in storage for almost 10 years. After I get moved (end of this month) and settled into our new home (who knows how long that will take), it's my plan to start listening to vinyl again. I am going to build a SS integrated preamp that will likely feature a 2-way electronic crossover, and use that to drive four tube monoblocks. Crossover at about 2KHz. So I am thinking about a two-way speaker system with a transmission line woofer and an exponential horn / compression driver for the top end.

[rp]

Lou, keep in mind the magic of horns/TLs has to do with the hyper speed and super efficiency of the special drivers. Those small diameter, full range coaxial drivers specially designed by the likes of Fostex and Lowther give TLs their unique quality. Done right they are like electrostatic speakers but without the twee artificial delicacy of electrostatics - more impact across the band even in the treble, if that seems right to say. I like my ss w/ported box speakers for what they are (Spendor/Naim) but when you evaluate a system and compare to real (live) music as a benchmark you realize that live music is incredibly dynamic, fast, everything from 20-20khtz 'punches' and horn systems do seem "more right" in this regard. It can get fatiguing, and given the mechanical aspect of the designs the magic only happens when they are played loud, something I don't do much anymore. They have a sweet spot of a certain (high) decibel point that is too limiting for me to listen to music depending on mood or time of day.

Anyway, building a TL using normal drivers doesn't seem worth the effort to me. Do some background on Fostex, some of their drivers are like $50-$100. And you don't need tweeter horns or cross-over parts. If you make a mistake you can always sell the drivers on ebay and as for the cabinets you can put some tar paper across the top, stick them in the yard and let the dog move into them!

http://www.wilmslow-audio.co.uk/fostex-56-c.asp

[ER]

I got DEEP into the hi-fi rabbit hole a while ago and discovered the key to life-like acoustic energy in the room has everything to do with impedance matching at every stage.

What this means is current over voltage, simple circuits, and where things fall apart the quickest is with speakers; the best impedance match with the air in the room is a horn. Exponential horns are designed for maximum efficiency, it's worth giving up a little efficiency for better fidelity and constant directivity, I recommend conical horns or nearly so, known as "wave guides" now days. Another bonus is that you can use the directivity of horns to minimize room reflections that plague normal speakers.

I had a big 3 way horn system with folded bass horns and "synergy" style horns that share a common throat between the mid and high drivers, it sounded great, but I down-sized to 2 way "econowaves" using a jensen ultra-flex or "Onken" type cabinet with 15" woofers and QSC HPR152i horns http://www.parts-express.com/qsc-pl-000 ... i--245-625 with RCF ND1411-M drivers http://www.rcf.it/en_US/products/precis ... s/nd1411-m These drivers have a low compression throat and a radial phase plug similar to the old RCA theater compression drivers, and sound fantastic.

I'm really happy with the econowave design and don't miss the big horns to badly. They sound like live music and are detailed enough to use as studio monitors. The big onken cabinets were overkill and I think some ported cabinets with some high efficiency woofers would work just as well. The ones I have now are around 98dB/watt, I have some 102dB/watt woofers but they're 4 ohms and I haven't bothered making different crossovers to go 4 ohm, though I may soon since the surrounds on the woofers I have now are going south.

Take the speakers you have now and convert them to econowaves, a google search will get you there, and it won't cost you much and will play very well with those 2a3's.

[potatofarmer]

Bill Fitzmaurice is still cranking out horn designs.
http://www.billfitzmaurice.com/index.html

It looks like he's made some transmission line-esque projects too:
http://www.billfitzmaurice.com/TLAH.html

[passfan]

You can do an ebay search for DCM Timeframe. They are an inexpensive design from the 70's and 80's that sound large , as you say , and deliver tight big bottom end out of 1 or 2 5" cones .

[TUBEDUDE]

I built a pair for my fiance last Christmas. They are a simple design using cheap 5 1/4" pyle car speakers, driven with a $20 class T amplifier. Originally it was to replace the crappy 1" speakers in her TV. She has a hard time hearing, and I thought it would be more intelligible with a wider freq range. That way she wouldn't have to have the volume so high. As it turned out, the sound was phenomenal! Listening to concerts on cable was stunning. I plugged in my Ipod and was blown away. Dynamic, full rich lows rivaled my expensive stereo system. 20 bucks in speakers, a sheet of plywood, glue, screws, some dacron and magic.