Transmission line speakers

Who makes transmission line speakers now?
Acoustic Zen Crescendo was the bass champ at RMAF 07. I think the smaller model is transmission line also.
At the risk of sounding like a broken record, the best transmission line speakers I have heard are the JM Reynauds. I am a big fan of the (now doscontinued) Offrande speakers, but the entire line shares many of the same qualities: warm, liquid, detailed and a remarkably wide and deep soundstage.

Good luck
The Intuitive Design Summits also utilize a transmission line. They are more than worth the effort to seek out for an audition.
Though you almost never see it, TL loading is far more critical to the midrange than the low frequencies. The ability of such a design to let go of the notes is unrivaled by almost (I said, almost) any other loudspeaker design.

The medium - larger speakers in the Rega line feature TL loading of the low frequency drive units, and are some of the more underrated and overlooked products out there.

This opened a huge can of worms around here many years ago, but a purist would not consider a Von Schweikert design to be a TL. Instead, they're akin to what Bud Fried introduced as the "Line Tunnel", which is a stuffed, ported loudspeaker. Still, a most competent alignment, offering a lot of the performance of a TL with an even easier (and same low cost and ease of build) to implement design than a typical ported loudspeaker.

My own Fried (8" mid/woofer) A/6 and Fried (10" woofer) subwoofer feature the Line Tunnel. I find the A/6 are not ecliped by most anything built today under $5000.

One thing to keep in mind when dealing with true TL loading of the low frequencies is that almost no one gets it right. The two most common errors are undersizing the line and overstuffing it, the latter being the far more egregious fault. Better to not stuff at all as opposed to overstuffing. The end result being that they actually come across as bass shy and cold, as there is a pretty good sized dip in the mid/upper bass, even if they will play quite deep.

Still, once one has experienced the truly tuneful (and by that, I mean, the ability to discern musical low frequency notes as opposed to the typical and appropriately named "one note bass") low frequency response of a decent TL, it's never forgotten.
They aren't a TL? ( And the Frieds are a tapered, folded transmission line, which is almost identical to the design I've been using for woofers since 1980:( I suppose some peoples' definitions may vary, but transmission lines CAN take various forms(even variously damped, aperiodic chambers; as long as the 1/4 wavelegth goal remains): (
I spent the better part of a decade building various DIY transmission lines (in SpeakerBuilder magazine issue #4 of 1986 you'll find one of my designs), and in my experience there's a tradeoff: Sufficient output from the end of the line to reinforce the deep bass also results in a cancellation notch in the upper bass at the frequency where the line's effecive length is equal to 1 wavelength (which puts the line's output 180 degrees out-of-phase with the direct sound).

You can see that notch in SoundStage's measurement of a transmission line speaker:

Fortunately notches are relatively inaudible, so it looks much worse on paper than it sounds. Most people won't even know it's there.

There are techniques for minimizing this notch, but they involve tradeoffs in other areas.

That being said, a good transmission line can be a magnificent-sounding loudspeaker system, especially in the midrange as Trelja notes.


And especially when properly used with planars, as they are innately faster than most other alignments.
Well,what brought this all about,was a friend of mine picked up some B&W DM2a's and sold them to me for $21.00
That's what he payed for them at a thrift store here in Seattle area.
These are a transmission line speaker, and are seriously built,they would rate a 5 on an Audiogon scale as the tops are beat a little and they're old! The woofers say 1975 dated.

The bass has no boom at all,and as pointed out the mids and high are clear,very clear. There seems to be a righness to the timing of them.The sound come at you like real time,hard for my to say it right...
They are also very dynamic in nature, I love them and want to seek out others like them,or better. They stomp all the speakers I have ever had.

I wish I could post photos of them like Audiokarma,you can see them there(under the same name).

Thanks for the suggestions,I will research them all.

If anyone know more to look into, I'm all ears.
Wow the PMC's look great! I wonder what they go for used..
I must look into this.. thanks!
Mcgarick- The term you're looking for is, "PACE"(a quality of live music that T/Ls and TQWPs retain better than most designs): (
Rodman99999, for a very long time, I've struggled for the right term to describe the low frequency performance of a true TL loudspeaker. So far, I've yet to find it. Many folks seem to prefer "pitch", but that doesn't satisfy me, either.

What I'm talking about is that sense of being able to clearly discern the notes, and actually hear the music present in the low frequencies, just as we can through the mids and treble, as opposed to the "one note bass" of most competing products. The loudspeakers I use in my main system are ported or horns, and they do not come close in this regard.

What speakers are you using in your system? Were they produced by IMF or KEF, or more of a homegrown variety?

As I said, a purist would not consider the alignment VR employs to be a true TL. This fueled an extremely long and contentious debate here many years ago.

Finally, to reiterate another point in my first post, which Duke also spelled out, true TL is prone to a dip in the mid/upper bass response that leaves the speakers actually coming off as bass shy and cold.
When I owned my speaker company in Florida, a customer(very affluent) came in(1980) that wanted a pair of subs to go with his Acoustat Model IIIs. We experimented for some time with a number of designs and drivers(his $$). The best combo turned out to be the 10" woofer that Milo Nestorovic was using in his passive/active bass system, in an 8', tapered, folded, progressively damped(we settled on bonded dacron) transmission line. These were actively bi-amped with a Dahlquist DQ-LP1 and a Hafler DH-500(both modded). Proper damping(it took some doing) in the line effectively cancelled any frequencies but the very lowest(desired reinforcement) and eliminated them from the vent's output(no mid-bass dip). These were positioned upright(48" tall) between the planars, to eliminate time/phase problems. They integrated beautifully(no lag/great imaging and sound stage). The bi-amped KEF LS3-5A/B139 (in acoustic suspension) system I built/owned got sold, and his system duplicated, after I heard the dynamics. The only problems I've ever had with thinness have been room related(only lately). An expensive divorce forced me into a pitifully small listening room(nulls at 60/120/240hz). A modded TacT RCS 2.2X has solved that, enabling me to position the TLs, on their sides with the drivers in the room corners, to more evenly load the room(bi-amped with Maggies). No problems ever with "one note bass"(can't tell the kick from the double bass, etc/no definition or pitch). Part of that does come from having an amp that will control the driver in a basically undamped(no air suspension) enclosure too. I'm now using a modded TransNova 9505, that keeps an iron grip on the 10's. Things have progressed nicely since 1980. The only bass system I've encountered that makes me want is the Lyngdorf W-210, but I couldn't use them in my room anyway. No one sells the drivers separately now, or I'd have a pair in my TLs.
"Rodman99999, for a very long time, I've struggled for the right term to describe the low frequency performance of a true TL loudspeaker. So far, I've yet to find it. Many folks seem to prefer "pitch", but that doesn't satisfy me, either."

I'm listening to Bob Dylan's Modern Times CD,and was reading comment Trelja's comments,and it dawned on me that one quality that comes through,that's unique, is bass depth.The bass is so clear that you actually get bass depth,and this recording has that.
This may add to the timing affect. Very cool.

Those PMC's are pricey,maybe eBay, used sometime...
Mcgarick- Did you happen to read the article on Pace, Rhythm and Dynamics that I posted? It really brings many bass integration/presentation issues into perspective nicely. Many bass sytems will provide deep bass, but without any definition, speed or timing/phase accuracy
I did read your post Rodman99999, thank you for the informative read. Sound like you have lots of experience is this dept. I wish I had a better room,I think it kind of keeps me set back some,watcha gonna do?
The DM2a's sound good in my room,so Im keeping them for awhile.
I'm enjoying my system more than ever. I'm much more aware of boomy(blase) bass.
Ther are room correction systems available(ie: TacT, Lyngdorf), that can help you with room interaction(time/phase/freq response) problems. BUT- As long as you are enjoying the sound/music with which you are presented; nothing else matters. Happy listening!!
Rodman99999, from afar, I like the way your TL woofers look!

Nestorovic was a most capable loudspeaker designer/builder. Are you still using the Acoustats for the rest of the music? I've always been a fan of them.

My own TL subs, which were Bud Fried's personal units (he gave them to me just before he passed away a few years ago) sound similar in that they also use 10" (Gefco) woofers, with the line just a bit (if memory serves me correctly) longer than yours. They are referred to as the "O" subwoofers, which served as an upgrade to the "D" subs that were a part of the Valhalla System, which was the definitive product that represented Bud's life's work of what I like to refer to as the "Holy Trinity" of true TL bass and midrange (ala the "C3/L" sat"), series crossovers, and low Qts drivers.

In my opinion, the dacron (or, fiberglass) you employed is likely the best damping material choice for a TL. The foam Bud used breaks down over time. Long fiber wool is the considered the gold standard, but is subject to attack by moths, though there are products available these days that can be employed to address that.
Anybody have any experience with T+A elektroakustik TL speakers like the criterion TS 350?
I sold the Acoustats some years back, when I no longer had a listening room big enough to let that system breathe(everything sounded best with 3' feet behind, 10' between, 4' open to either side of the panels, and nothing behind my seat for 15'). The TLs were tuned to have usable output down to 16hz(more visceral than audible). I used to listen to a lot of pipe organ music, on vinyl(love direct-to-disc), with the turntable in a separate, attached room to avoid feedback. Those were the days! I'm now using a pair of modded Maggies(excellent speakers), and mass quantities of Auralex. Of course- It'd be a gas to have all my present equipment and cabling(nothing's the same but the TLs) in my old listening room, and be able to swap the Acoustats in for a comparison.
How about electrostatic with build in transmission subwoofer:
Thanks, Dracule1! I've been meaning to mention Roger Sanders' creations, the InnerSound and SandersSound speakers. Both his former and current company implement true TL woofer alignments.

I've spent a lot of time with Roger at the shows over the past couple of years, as we've shared rooms, meals, rides, etc., and we've discussed a lot of things in detail. His theories on TL design, as well as the implementation thereof, are spot on. The sonics speak for to that. I highly recommend his products to anyone.
Sanders had written some excellent/in depth articles on TLs and electrostatics that appeared in Speaker Builder mag, back in 1980(or so). Those were what led me to experiment with them and the(afore mentioned customer's) Acoustats.
You are better off designing and building a TL yourself then buying a commercial version. Most commercial TL's are undersized.
the best ive heard are the PMC EB1i.

2ch awsomeness!!!

after i win a powerball lottery, i will buy an entire 7.1 system from PMC!!!!!

are you planning on buying a pair? or are you just curious... i owned a pair of kestral 2's...sob....and there was pair for sale here recently. easy to replace parts, incredible bang for the buck.
FYI... an individual in Jupiter, FL has a vintage pair of IMF Studios (Fried design) they are giving up. More details here...

If interested, I'll forward their email to you.
This very nice lady in Florida gave me her IMF TLS50's
Hard to believe,but true. They were the most expensive free speakers I ever had to ship!

$278 bucks worth...

I hope they get here in one piece.

I'll update my findings with these venerable speakers.

She was an original owner, who listens to classical,so that a big plus right there.
She was very insistent they be adopted by someone who would appreciate them.

I can hardly wait...
Congratulations, Mcgarick! In response to the original post, I believe DALI makes a transmission line...the MegaLine.
Castle acoustics has made outstanding transmission line speakers for 30 plus years - floor standers from Severn model two way up are awsome transmission lines designs. The cabinets are small, but the soundstage and presense is HUGE.
Congratulations on the IMFs! I'm not surprised you love them, Bud Fried really put out some phenomenal products.

Sometimes, I listen to a pair of Frieds and wonder how far we've come over the past decade or two. While it's almost de rigeur for so many to declare that speakers are far superior these days due to advances in materials, being able to listen to a few different Fried models in my home leaves me more than skeptical.
Ok,I finally put my system up, there's a picture of the IMF TSL50's, a nude pic..I'll try to put some others too.

The mk2 are better looking as they would have nice wood instead of the black paint, non-the-less a fantastic speaker...that I'm proud to own.

I'm thrilled with my hifi now! took long enough!!
This is funny !
Owned the B&W DM2A in the mid 70's, and replaced them in 1978 with........IMF TLS50Mk2's !
The listening room I had, was too small for these speakers, so I moved on to Elipson B1303's in 1980.
Serious Stereo makes an excellent transmission line speaker using the Altec 604H. It is rather large but is 102db and the bass is deep with extreme clarity.
It would appear that you have taken Rodman99999's advice, although possibly unwittling. The IMF was made by Irving M. Fried, while he resided in England, before moving to Pennsylvania and starting Fried Products. So you are the proud owner of a pair of "Frieds". The one I saw in the picture was the "left" speaker (tweeter is on the inside). Not only will you find the sound of a transmission line such as this very pleasing, but the rules are more liberal for placement. As the bass will not become bloated when it's placed close to the rear or side walls. So you can set them up where the WAF facter is excellent, without comprimising the sound quality. I have some experience with Fried so if you need anything, just write.