Transmission line speakers

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.

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.

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.

Audiobyus1, I agree with your assessment of Fried loudspeakers.

However, apart from his time at Harvard and distinguished service to our country during WWII, Bud Fried lived his entire life in the suburban Philadelphia, PA area.

It is true he spent a few months per year in Europe and the UK, making in his estimation 3 to 4 trips on an annual basis in an unending search of audio. Although he never mentioned to me about maintaining a residence in the UK, given the amount of time he spent on the other side of the ocean, held a self-admitted tremendous fondness for the ladies, and the fact that he came from quite a wealthy background, it would make a lot of sense to have a second home there.

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.

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.