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December 2017
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PureAudioProject Trio15 Horn1 Open Baffle Design Speaker
A trip down the rabbit hole.
Review By Paul L. Schumann


PureAudioProject Trio15 Horn1 Open Baffle Design Speaker Review


"But I don't want to go among mad people," Alice remarked.
"Oh, you can't help that," said the Cat: "we're all mad here. I'm mad. You're mad."
"How do you know I'm mad?" said Alice.
"You must be," said the Cat, "or you wouldn't have come here."
     -- Alice's Adventures in Wonderland


First of all, let me be totally upfront with you my dear readers, this is the first review I've written in a long time, so if I come off as an old curmudgeon, I apologize. In the business of high-end audio, the one constant is change. So when Steven asked me to review the Trio15 Horns, I knew I'd be in for a challenge. After so long, could I still use the reviewer part of my brain?


"The time has come," the Walrus said,
"To talk of many things:
Of shoes--and ships--and sealing-wax--
Of cabbages--and kings--
And why the sea is boiling hot--
And whether pigs have wings."
     -- Through the Looking-Glass and What Alice Found There


Before you continue reading this, I would recommend you read Rick Becker's excellent review of the PureAudioProject Trio Horn1's sibling, the first generation of the Trio15 with TB driver. Rick does an excellent job of going through the assembly process of these early and more DIY speakers. I have to honestly say the Trio15 Horns that arrived at my humble abode were the latest generation, with Aluminum Frame and almost completely assembled. All I had to do is put in the horns, add capacitors to the crossovers, connect the drivers and was ready to go. No soldering or woodworking required. If you've ever put together anything from IKEA, you get the idea.

Once they were built, I had to make some space for the as my regular speakers are Thiel 1.5s, which are about as unobtrusive as you can get at only 8" wide. The Trio Horns are just over 21" across. This required me to do some rearranging of the baby grand within my living room. Luckily, I was just able to make things fit. Once in place, you really can't miss these guys as they are visually appealing and sizeable. The ones Ze'ev of PureAudioProject sent me have the white panels. Combined with the dual 15" drivers and beautiful wood horns in a D'Appolito configuration, these speakers are real attention grabbers. Depending on your significant other, these could have a variety of opinions concerning styling. It might be a good idea to show your sweetie some images before you order them.


PureAudioProject Trio15 Horn1 Open Baffle Design Speaker Review


Now let's move on to the components themselves. The bass drivers are upgrades of the longstanding Eminence Alpha 15" driver. They have been redesigned to sound best when mounted on an open baffle. With cast aluminum baskets and large neodymium magnets, they are quite impressive from the front and the back. The real focus ofPureAudioProject'sTrio15 Horn1, and what catches your eye when you first see them, are the beautiful wood horns. The wood horns themselves remind me of the old TAD version in their construction, using beautiful stained laminates. The compression driver itself is a new design using a polymer cone for a more natural tonality. This horn/driver pairing plays down to 550 Hz, which is C# above tenor C. This is very typical of tweeter horns. The crossover itself is called ‘Leonidas' and is a simple network with the horn and bass drivers hooked up in series (Series Network). Each crossover has one inductor, one capacitor, and two resistors, that's it! Such a simple crossover lets you know the quality of the drivers that PureAudioProject is using in theses speakers since no correction is needed. This low part count gives you the benefit of less coloration between you and the music. We'll talk more about that later.


"Who in the world am I? Ah, that's the great puzzle."
     -- Alice's Adventures in Wonderland


Because you cannot go down to the nearest audio salon (what few are left) and listen to these speakers prior to purchase, I am going to write this part of the review a little differently. Firstly, let's talk about the unique configuration. Open baffle speakers are interesting creatures in themselves because of how they interact with the room. Since there is no box around them, the room itself is the enclosure. Be prepared to play quite a bit with where you place them. The second point is that they are horns. This gives them an efficiency of 94 to 96 dB/W/m with an impedance of 8 Ohms. In my smaller room, it's probably closer to the 96dB. This makes them ripe for SET amps of lower power. This also makes them tricky, since horns are so revealing with their high sensitivity. The weakest chain in the audio link will be exposed. Another thing to consider is that horns typically will not give a ruler-flat response. That's the tradeoff for the delicious dynamics they give you.

When I first started listening to the Trio15 Horns, I was driving them with my trusty Jolida SJ202A. It's a 40 Wpc push-pull EL34 stereo amp that I have modified over the years. While this was not a perfect match for the horns, it was a good place to start. Early listening sessions revealed that at first, the bass drivers were tight and lagging behind the horn. After about a week of regular listening, this went away as the bass drivers started to break in. As the horn driver/crossover components settled in, there was a reduction of brightness. Over the second week, the Trio Horns became more revealing of nuances in the music. Unfortunately, this also meant I was hearing more of the muddling that horns can reveal in push-pull pentode amps. A SET would be needed.

Enter the Line Magnetic 218IA, a 211-based integrated amplifier. Line Magnetic uses PureAudioProject Trio15 speakers to demonstrate their equipment so they are knows to work well together. After a short period of time, I had the glowing beast within my own home and hooked up to the Trio15 Horns1.


In another moment down went Alice after it, never once considering how in the world she was to get out again.
    -- Alice's Adventures in Wonderland


PureAudioProject Trio15 Horn1 Open Baffle Design Speaker Review


This Is Where The Story Gets More Interesting
Adding another new component to the mix is always a tricky business. Where does the sound of one begin and the other end? Ah yes, knowing I would have to be patient as things settled in. After several more weeks of casual listening, I sat down for some serious listening. This was when I started to notice something. Whenever the volume was turned up to get the bass cranking, the treble was a bit bright for extended listening. I mentioned this to Ze'ev, and he sent me some resistors and capacitors to swap out, but this did not fix the problem. Ze'ev said it sounded like I had something hooked up out of polarity. I went through all the possible culprits twice to make sure, but to no avail. As I was struggling with this problem, the word "polarity" kept going through my head. Then I had a "I wonder if ..." moment. The iFi Audio micro iDSD, which I use as a DAC/preamplifier within my system, has an absolute polarity switch on it. I had fiddled with this switch in the past, but hadn't heard any difference in my regular system.

I know that some audiophiles insist that absolute polarity is a critical aspect of music reproduction that is ignored. So with that in mind, I flipped the switch. Presto! Suddenly the bass and treble were in sync and glorious music was coming form the Trio Horns. At that point I scratched my head and chalked it up to another mystery of life solved. Only a million more left to go.


Cat: "Where are you going?"
Alice: "Which way should I go?"
Cat: "That depends on where you are going."
Alice: "I don't know."
Cat: Then it doesn't matter which way you go."
     -- Alice's Adventures in Wonderland


Now that I had the absolute polarity quandary resolved, and had a good sense of the overall sound of the Trio Horns, I was ready to truly explore the mysteries of a modifiable crossover. I had no idea what was out there when I first started on this journey. A lot of companies make crossover components and some enterprising people have done a good job of comparing them. When I first received the Trio15 Horn1, the crossovers came with Mundorf MCap Classic capacitors (polypropylene dielectric), Mundorf BS140 Inductors, and Mundorf MResist MOX (metal oxide) resistors. When Ze'ev sent me other parts to try, was really curious how much of a difference it would make. I know parts choice is big for electronic component designers, but I'd never heard much about them in crossovers. The little care package he sent me contained Clarity Cap CSA capacitors and Mundorf M-Resist Supreme wire-wound resistors. As Ze'ev instructed, I only made one change at a time so I could parse things out. (A word of advice, a short-handled Phillips-head screwdriver will come in real handy for this work. It's a little tight down there.)


PureAudioProject Trio15 Horn1 Open Baffle Design Speaker Review


The first change I made was to swap out capacitors. With the Clarity Caps there definitely was a greater resolution of detail, but at the expense of thinning out the mid-range. Adding the Mundorf wire-wound resistors did more of the same. The music took on a hard edge that made it a difficult listening experience. When I returned to the original configuration, a good balance was returned. Now this doesn't mean that the parts I tested are "worse" than the ones that were part of the original configuration, they just don't work as well in this particular application. Like I said, horns are sensitive beasts and their bottom crossover frequency is down into the mid-range, well below that of normal tweeters. This is part of the fun of these speakers: the ability to swap out parts to suit one's taste. My wife and I are very sensitive to anything that is bright. You may have a totally different impression. Isn't that what is so great about audio? One person's cup of tea is another person's muddy water.


"Take some more tea," the March Hare said to Alice, very earnestly.
"I've had nothing yet," Alice replied in an offended tone, "so I can't take more."
"You mean you can't take less," said the Hatter: "it's very easy to take more than nothing."
"Nobody asked your opinion," said Alice."
     -- Alice's Adventures in Wonderland)


Are PureAudioProject ‘sTrio15 Horn1 My Cup Of Tea?
Let's explore this.
As I have said, they are very revealing speakers. Subtle cues normally buried in the mix suddenly come to life. Snow Patrol's album Fallen Empires is a tough nut to crack because of its dense arrangements and many times it can sound muddled. But with the Trio15 Horn1 all the instruments and voices are distinct with their individual tonalities intact. Alison Sudol's vocals from A Fine Frenzy's One Cell in the Sea jump to life as she switches back and forth from her deeper full throated voice to her little-girlish head voice. John Elliot Gardiner's renditions of Beethoven's piano concertos has a strikingly different tonality of fortepiano, instead of just sounding clunky, it now has a gravitas like that of a real instrument!

The interplay of instruments from Genesis' Trick of the Tail is suddenly so obvious. Sometimes I'm surprised while listening to some classical recordings to hear that a section wasn't quite on pitch or just a quarter beat behind. Time and time again, recordings which I have listened to my whole adult life suddenly gained new meaning as more musical cues are revealed.

Because the Trio15 Horn1 have so much speaker surface area and are an open-baffle design, their presentation reminds me of a planar loudspeaker. This means a big open soundscape with lots of depth. If you're a fan of symphonic music like I am, this is a joy. To get this illusion, you will need to make sure that the Trio15 Horns are toed in so that the horns are pointed directly at you. I found that off axis listening made everything more diffuse and less engaging.

Now lets get to what I consider the two holy grails of music, tone and dynamics. Tone is the area where many horn loudspeakers can fall. The distortion caused by sound waves propagating out of the horn can cause coloration. This tends to show up in vocals. This is not the case with the Trio Horns. Whether it was Imogen Heap, Peter Gabriel, K.D. Lang, Don Henley or Bjork, each retained their distinctive timber and intonation. With each listen, I gained more understanding of how these great artists used their voices to enhance the emotion of every song.


PureAudioProject Trio15 Horn1 Open Baffle Design Speaker Review


Now I Saved The Best For Last: Dynamics
As I said, dynamics are where horns excel. The Trio15 Horns lived up to that expectation. From ppp to fff, the Trio15 Horns handled it all with aplomb. How many times did my wife and I sit down to listen at what we thought was a reasonable volume only to end up with a symphony orchestra at full tilt in our living room! Of course all this was at such a low distortion that we didn't even realize how loud it was until we tried to talk to each other. My favorite demonstration of the incredible dynamics was not large-scale orchestra music, but a solo instrumentalist. The recent Michael Hedges compilation Beyond Boundaries, has several songs of him playing the harp guitar. These close-mic'ed recordings demonstrate the forcefulness of Hedges' playing. No matter how many times I listened to these songs through the Trio15 Horns, I literately jumped every time Hedges banged out the bass line. Amazing!


"Oh, I've had such a curious dream!" said Alice.
     -- Alice's Adventures in Wonderland


I complement PureAudioProject on creating truly unique loudspeakers. They have the open presentation of planars, but retain the impressive dynamics of traditional horns. The horns and bass drivers are mated perfectly for an engaging lifelike presentation. They have the added capability of switching out components in the crossover to tailor the sound to your liking. Yes, I'll have that cup of tea now, with milk please.




Sub–bass (10Hz – 60Hz)

Mid–bass (80Hz – 200Hz)

Midrange (200Hz – 3,000Hz)

High Frequencies (3,000Hz On Up)



Inner Resolution

Soundscape Width Front

Soundscape Width Rear
Soundscape Depth Behind Speakers

Soundscape Extension Into Room


Fit And Finish

Self Noise

Value For The Money



Type: Open baffle loudspeaker
Horn1: Extended Polymer 1.4" compression tweeter
           47cm x 23cm custom-made wood horn
Woofers: PAP exclusive OB-A15Neo
Sensitivity: 94 to 96dB/W/m (in a typical room)
Nominal Impedance: 8 Ohm
Frequency Response: 32Hz to 19KkHz (in a typical room)
Crossovers: Manufactured by Mundorf in Germany
                  Option1: Leonidas crossover, Trio15 Horn1 configuration
                  Option 2: Audiophile-grade two-way crossover
No notch filters
Bi-amp'ing option available
Main Capacitor (in serial to the horn) is interchangeable
Horn SPL is adjustable by gold plated jumper selecting four high resolution audiophile-grade resistors
Horn Finishing: Gloss White Baffle and Wood horn (others available)
Dimensions: 21.25" x 46.67" x 10.63" (HxWxD)
Weight: 81.6 lbs each
Price: Shipped from the USA $7490, excl. VAT and shipping
Shipped in the EU: €8900 incl. 19% VAT and excl. shipping, shipping from Frankfurt Germany



Company Information
434 Lee Street
Iowa City, IA 52246

Voice USA: (877) 927-2233
EU (D): +49 (0)151 696 49581
Direct: +972 54 258 4258
E-mail: info@pureaudioproject.com
Website: www.PureAudioProject.com

















































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