The Tonian Labs TL-D1 loudspeaker is described as a "semi-open-baffle"  
design by its manufacturer.  It's a mid-sized floorstander with an 8"  
Fostex wideband driver coupled to a ribbon tweeter.  (Tonian does not  
reveal the details of the crossover and I do not know if the Fostex is  
run wide-open or not, but I suspect not, as I've never heard an  
unfiltered Fostex driver of any sort sound as neutral as this one does!)

This is a truly a remarkable speaker and I think almost anyone would  
acknowledge that.  Why?  I can think of several reasons:

1) It is the first speaker I have ever heard employing a wideband  
driver that is both very sensitive and yet not the *least* bit  
"shouty".  There are no peaks and no uneven frequency response of any  
sort, and that was verified by me with measurements.  This alone is a  
pretty remarkable achievement - in a speaker of any cost, must less  
one costing $2500.

2) It is *astonishingly* dynamic, in both the micro and macro sense,  
and with very little power as well.

3) It blends a cone with a ribbon in a way that is absolutely  
sonically transparent.  The speaker, like several other very good two- 
ways, is perfectly coherent and sounds like a point-source.  Is is the  
fact that this is done with a ribbon that is noteworthy.

I listen mostly to jazz, and the speaker is truly remarkable in this  
genre.  Bass reach is entirely adequate and bass articulation and  
detail absolutely second to none (save perhaps a front-loaded bass  
horn!).  This is really *the* speaker for jazz percussion.  Horns have  
just the right amount of bite, vocals are very natural, and nuance and  
detail are exemplary.  The delicacy and reach of the ribbon tweeter  
make the symbols come alive extremely well.

The speaker is perhaps less stellar on rock but still very good.   
Here, the lack of complete bass extension is noticeable, and some  
whizzer anomalies or cone break-up occasionally make themselves  
known.  However, this speaker does a much better job on rock than any  
of a number of single-driver high-efficiency models I've had, mostly  
back-loaded horns.

The speaker is indeed very revealing, with changes in sources and  
amplification very readily audible.  I have been rotating two amps,  
both of them stellar in their own right: a Korneff 45 SET amp and a  
First Watt F3.  Even the 45, with under two watts, is entirely  
adequate power-wise, but, as owners of such amps and speakers will be  
aware, the speaker does come alive dynamically a bit more with more  
power.

[The F3, at 15 watts, fills that bill.  This single-ended (and thus  
class A), single-stage JFET amplifier is quite remarkable; I never,  
ever thought I would find a solid-state amp that really holds its own  
against the best SETs but this one does.]

So, to close out this short review, if you have been seduced by the  
immediacy and clean bass of single-driver horn designs, but turned off  
by their bite (or at least a frequency response far from flat), you  
really need to hear this speaker.  Again, I was totally astonished to  
find a speaker under $10,000, at least, that can do what it can do.   
It is an amazing product and true giant-killer.