Intro
I have always appreciate the basical principle of open baffle speakers. If you face up to their hidden limits – first the theorical short circuit and the cancellation between the front and rear output in reverse phase at low frequencies – you can easily fall in love with all their qualities: airiness and transparency in general, dynamic and articulation, cleanliness and lack of perturbance on the bass. Therefore, I always wanted a pair of this speakers as an editorial reference.
Design
PureAudioProject - abbreviated PAP from now on - is a recently added company that deals only in open baffles – abbreviated OB from now on. I was able to get a first look to this tech at the specialized fairs, which left me with this thought: "OK, this is a genuine sound, but where are the crates?”
Born from the mind of the AD Ze'ev Schlik, the company is based in Israel, very close to Morel, and it produces and delivers directly with logistics bases both in Europe and in the USA too.
I think Pap’s OB concept is quite catchy. To give you an idea:
- a two-way OB speaker
- where the lower way is reproduced by two parallel woofers
- the woofers are 10 or 15 ", depending the space they have to be used in
- and the mid-high way is reproduced by several drivers (one for type of model), chosen by the purchaser and interchangeable
- with three separate crossovers to choose from, available in full range basic or, with surcharge, two-way, passive or active
- all mounted on a unique support structure, with a separate panel for each speaker
A beautiful application of the Latin principle divide et impera.
In detail, medium-highs frequencies can be reproduced by wide band, dome, ribbon or horn loudspeakers. The PAP project is built upon the use of refined audio components and collaborations with established world producers, such as Morel and Eminence for woofers; Beyma, ESS Heil AMT, Morel, Mundorf, Tang Band and Voxativ for mid-tweeters; and again Mundorf for crossovers.
In the PAP’s catalogue we find also what can be regarded as the extreme version of the Trio15 model, the Quintet15, an imposing speaker, with as many as four 15" woofers per channel.
Manufacture and assembly
The PAP diffusers arrive disassembled, in the classic "flat packs": like an Ikea project. You can find an interesting video, shot by someone like us - a passionate audiophile of the product - at this link¬.
How to do it, in summary: mount the metal structure, mount the speakers on their panels, mount the panels on the metal structure, connect the cables to the speakers, mount the components on the crossover, attach it to the bottom of the frame, connect the already spun cables to the crossover, and it’s done! In a couple of hours, without technical skills and without even seeing a welder, anyone can succeed in mounting the PAPs in their listening environment.
Let’s look at the single components.
If the 10" of the Trio10 are produced by Morel, the two 15" speakers that equip all the Trio15 models are straight upgrades from the Eminence Alpha15a, exclusively produced for PAP. For over 50 years Eminence equals professional speakers, perhaps the most experienced manufacturer of amplifiers for instruments such as bass and guitars that, as you know many times happen to be... open baffle!
These Eminence by PAP have seen an optimization for use in open baffle. With a very open die-cast aluminium basket - to reduce the turbulence of the rear emission of the cone-, a neodymium magnetic unit, 2.5 "coil, a ring of Faraday - see here a search on its advantages - and a very rigid spider. Jerry McNutt, Head of Product Design Eminence, states precisely that "speakers are specifically optimized for OB use, those with the best performance and less distortion." The following graph, obtained in an anechoic room, is therefore not entirely related to the listening experience in the environment, where the two woofers, in parallel, give justice to low range frequencies.
The horn of these Trio15 Horn1 is from PAP, custom-made, with compression driver in 1.4-inch plastic polymer. Aligned with the woofers, the trumpet naturally decreases around 550 Hz, the crossing with the low range is around 500 Hz and the filter is of first order Series Topology. This profile also implies that, around 15 thousand Hz, its response starts to quickly decrease. However, its efficiency can be modified with an increase in the treble, and also in the whole range of the horn, with a cap and a resistor - in two different values - connected in parallel to the basic resistor. It is therefore possible to change the efficiency of the horn without having to weld or untie, without technical or practical skills.
The Leonidas crossover is an original design from PAP, called after the name of it’s designer, Leon Huijgen, a DIY veteran from the Netherlands. it can be mounted on all models, both 10 and 15 ", and is characterized by a short signal path and simple layout. It has very thick printed tracks, connections to golden clamps and interchangeable audiophile quality components, in accordance with their positions and values. It can be mounted on the right or left side of the case, helping to reach the connectors even with short cables.
The supplied cables are of the Omega Audio High Cables multi-mills branded, in 1.5 mm OFC copper, which can be upgraded with cryogenically-patented PAP flat cables.
Smart the small feet included, the SuperSpike of the Norwegian Soundcare. These are tips with floor-padded underlays. What’s interesting about them, is that the sub-itip "wraps" the tip, so that it rests on it when the box is fixed and “follow you” when you move it. No more unstable supports or streaked floors, just take a look at this pic!
Listening test
In an OB the surface area of the front panel is an acoustic screen that physically separates the front and rear sound emissions, avoiding the cancellation between the front one in phase and the rear one in the counter phase. So how is it possible that these PAPs sound, can reach the lowest frequencies, equipped as they are with such small front panels? The reason is technical, and you find a summary of it in these two articles by Filippo Punzo - link here and here – Italian only. But for those of you, who just want to read this article I’m going to do a little re-cap. For the OB loudspeakers we needed: high - Qts, large radiant surface, high Vas - low yield and great excursion. Ndr | See the legend here. Have a look at Eminence cards for the PAP speakers, you can see that almost all the factors are meet. Except for the excursion - low value, which however allows the PAP speakers to contain as much as possible break-up phenomena of the cone.
Why this additional technical info? Because the specific characteristics of the OB loudspeakers should provide - above all - the positioning in the environment, which we are now going to analyse.
In a way the OB is a "naked" speaker. There is no cabinet to "protect" it from the reflections of the environment. That's why in my testing I tried to keep the PAP about 1.2 / 1.5 meters from the back wall, to get the best compromise between extension and bass punch. The boxes were positioned 1.6 meters from their internal corners, since they are quite wide, and I could not move them further apart. The triangle of the sweet spot was isosceles, in fact due to their large radiating surface, the PAPs should be listened from faraway, like isodynamic or electrostatic panels. You can listen to them more closely, but you will hear on some instruments the shifting of their image. This is due to the more marked passage of the emission from the frequencies of the trumpet to those of the woofer or vice versa. Turning up the volume, the depth of the scene is reduced and even the cleaning and articulation on the bass takes a hit. On the other hand, at the best distance from the wall, these two parameters improve significantly. They reach a rare equilibrium, combined with that feeling of airiness and lack of effort in the reproduction typical of OBs.
The Horn1 demands to be oriented towards the listener, with a good toe-in, because putted in a "flat" position, doesn’t reach a correct tonal balance. Also raising the front feet - to centre the trumpet towards the listener - helps to get the best possible frequency extension, especially on high frequency.
Let's analyse the three typical frequency ranges. I’m talking about three, because the way in which the woofer and trumpet crosses in the middle is peculiar and must be described.
The four 15 "woofers’ basses need a good running-in. In agreement with Ze'ev and with other reviewers or PAP owners, we concluded that after about 150 hours they "give up" and after 200 totals they stabilize. Their advantage is that, if you have done well, after you can really use them to the core. So the bass is there, it just need a bit of care.
The large surface combined with the limited excursion gives detail, articulation and definition, without distortion and with a lot of control. Do not expect the punch of an ATC or a PMC, also since you can get a proper home punch with less watts. Look at the Horn1, that thanks to the 8 ohms of impedance and 94-96 dB of sensitivity, finally sees the single-ended or low power amp as their favourite partners. I also run them with 70 watts in class D with a very modern Technics SU-G700, which have met PAP’s power estate expectations, but at the same time reduced a little their expressive articulation.
The woofer cones’ size and structure make them light, fast and very linear, both for extreme bass and for the midrange of voices, piano and orchestral instruments in general. Ending up with a full-bodied and focused sound.
I have to say that I was sceptic about the woofers being easy to drive. But the technical sheet, did not lie. The bass is neither boxy or boomy. To confirm this, the bass of this OB hasn’t created that sound "congestion" in my test room, that has sometimes annoyed me with other models.
The mid is present and natural, without effort. The Horn1 are very detectable, both for sensitivity - 94/96 dB - and for type of emission - the horn mid-tweeter. The latter does not have some of the harshness of the components with metallic drivers, which has been a pleasant surprise.
In fact, the acute timbre has the roll-off typical of this type of trumpet and, thanks to the overlap of the woofer, the timbre on the middle-acute is warm, but not euphonic, for technical features goes a little in subtraction on the highest timbre but at the same time it gives you long listening.
The sound is natural and without feeling of "electricity in the air", which I personally don’t really like. The PAP is really good in pulling out the sound from the "box" of the cabinet.
Pro
If you decide on buying the PAP, you can potentially continue in acquiring other "average units", having fun in having many cases in one: the choice of starting midrange is up to you!
Also, the beauty of being able to change the components of the crossover at will - trying new or different capacitors, coils or resistors - makes it a game without end.
The widespread approval for the PAP idea is an excellent indication of how good this project is. Have a look on their website and see for yourself the reviews and comments. Rarely have I seen so many spontaneous manifestations of affection and appreciation for an audiophile project in recent years.
Con
To get the best out of the PAP we need room for it. If not, there is always the Trio10 ... ;-)
Maybe
I must let you know that by tightening or loosening the Allen screws of the panels, the sound changes remarkably. When the baffle is freer, the sound is richer / denser, perhaps it has a lower definition. When you tighten the diaphragm screws to the frame, it sounds cleaner / more precise. Just like when a traditional box is loaded with weights.
Second point: but if full range they already sound like that, what about in bi-amplification?!
Quick metaphors and final recap
I have tried different models and I can say that the PAP and the Horn1, change the way you listen. With them we can de-construct our idea of Hi-Fi, to get much closer to the original sound. They offer that kind of sound that doesn’t blow your mind in any frequency range, but it’s natural and present. They do not aspire to fairness and neutrality but look more at achieving the physical experience of an amp / instrument case. They sound very "in the room", which I much prefer, leaving to the rest the holographic "theatre". So, leave aside your prejudices and let a "natural" listening win you over.
Whom are they for?
You need to build them, but they are not DIY. The PAP speakers are aimed at those who have always had the desire of “get their hands dirty” and build one for themselves, without having much of a technical, theoretical or manual skill. With this project you can discover yourself a designer, simply with a screwdriver and an Allen wrench. You will be easily able of assembling their boxes in a couple of hours, while having fun modifying their response with the additional components.
N.B. If I have the chance to get my hands on the Horn1 again, I hope to write a detailed article on the tweaking of the crossover: the Mundorf components supplied are already of high quality, but if I can get my hands on some NOS paper capacitor and oil of appropriate value ...
So, if you are looking for the open presentation of planers and much of the dynamics traditionally attributed to trumpet systems, the PAP Horn1 might just be what you’re looking for!
SCHEME SUMMARY
Timbre | frequency extension, faithful reproduction capacity of the instrument and its harmonics
The articulation and understanding of the instruments is excellent, especially when you do not pilot these OBs with high damping amplifiers, which tend to close them a bit. The tone is clear, without exaltations of any kind, although some may prefer them with the horn more open on the extreme, which is easily obtained with the kit of components to be placed on the crossover, at two levels of intervention. I also very much appreciate them for the roll-off which, when you listen to it on the axis with the mouth of the trumpet, makes you forget everything else. The advice, however, is not to plunge the room, making it excessively absorbent.
Dynamic | micro (detail) and macro (absolute), extension and speed of transients
With a mix of ease of handling, lightness of the components and speed, dynamics and power handling are really rewarding. Get used to the lack of listening fatigue and their realism never over the top, as mentioned just above.
Image | environment, transparency, scene, sound plans, virtual stage, sense of presence, resolution
Depth of the scene strictly related to the distance from the back wall. In general, ambience and sense of presence are accentuated, since the construction of the loudspeakers itself prevents them from playing "on the speakers". They are also able to hold great distances between them, creating fabulous stages.
Tonality | general setting of the appliance, if present or characteristic: for example, hot, cold, tack, amber, glossy, matt ...
I would say warm but not opaque, it is the kind of emission of music in the environment that I think is very close to the natural instrument.
Emotion | capacity for emotional involvement, very dependent on couplings, absolutely anarchic and personal parameter
The PAP point to the true of the musical instrument, they are among the best cases I have ever tried and therefore I strongly recommended.
Manufacture and packaging | The first is solid and concrete, especially thinking about how little "case" there is in an OB. It is an "all-loudspeaker": what you see is heard. The packaging changes with the supplier of the component, always however lean but professional.
Price/performance ratio | Very high, especially if we think that these Horn1 are the most expensive of the lot of Trio15. We could instead start - with 4,290 euros all included in the EU area - from the already very interesting Trio15TB with the Tang Band W8-1808 to equip us with a PAP with the larger 15 "woofers. It is the PAP project that deserves a Spark in the Dark ReMusic.
Official technical specification
Type: floor diffuser, two-way, open baffle
Sensitivity: from 94 to 96dB in a domestic environment
Impedance: 8ohm
Frequency response: from 29 / 32Hz to 19kHz in a domestic environment
Woofer: Eminence OB-A15neo on PAP specifications
Horn1: compression driver in 1.4-inch plastic polymer, PAP wood trumpet, 42x17cm LxH
Crossover: Mundorf production, Germany
First option: Leonidas crossover in configuration and components for Trio15 Horn1
Second option: two-way crossover and selected components
No notch filter - NdR - Filter eliminates band - in the crossover
Main condenser, in series with the horn, interchangeable
The efficiency of the trumpet can be modified by means of some bridges and selected audiophile quality resistors
Finishes: German oak, natural bamboo or lacquered, see here
Dimensions: 54x116x27cm LxHxD
Weight: 37kg each
Official distributor: direct sales, to the PureAudioProject website
Price on the date of review: 7.990.00 USD shipped from the USA, shipping included; 7.990,00 EUR shipped from the EU, Frankfurt, Germany, 19% VAT and shipping included
Associated equipment: to my system
