(note: I initially posted this over at head-fi.org but thought I should port it over here where it makes more sense)
This started off as just a review for the Celsus Sound SP-One active bookshelf speakers, but trying to describe any sound producing device in a vacuum is a fool's errand. I also obtained the SP-One because it is very similar in size to two other sets of bookshelf speakers I already had, so the resulting comparisons is only natural. Even if those reading are unfamiliar with them, having some reference and comparisons is better than none.
Some links to their respective product pages:http://www.celsus-sound.com/index.php/products/speakers/sp-onehttp://www.johnblue-audio.com/indexMain.php?language=en&mod=3&action=read&class=1&id=2http://www.centrance.com/products/masterclass/
Of note, while I do have the active version of the SP-One, I also tested in in passive mode which I will describe in greater detail down below.
Some general specs for you to glance at... SP-One Masterclass JB3
Impedance (ohm) 6 4 6
Max Power (W) 60 25 30
Sensitivity dB @1W @1m 88 87
Configuration 2-way 2-way coaxial/coplanar 1-way
Drivers 1.5"/3.5" 1"(?)/4" 3"
Port rear round front slot front round
HxWxD (mm) 195x130x180 230x145x207 208x129x188
Volume (L) 4.6 6.9 5.0
Weight each (kg) 2.3 2.48 2.1
(thanks to @srb for fixing the formatting!)
So all three of these are what I would term "actual" bookshelf size, ie: they can actually fit into a bookshelf (there are so many bookshelf speakers these days that I feel are more appropriately labelled as standmount, as there's no way they would ever fit on a shelf or desk). All three are built from solid wood and are ported designs. Build quality on each is fantastic and original pricing is all roughly the same in the $500-ish category.
For amping purposes, all three have been matched with integrated dac/amp units. I have paired the SP-One with its most likely partner the NuPrime IDA-8. The Masterclass 2504 comes in with the matching Centrance Dacmini PX. Lastly, the Johnblue JB3 is a bit of the odd duck as it does not have an obvious partner, but I mated it with my steadfast Bryston B60 (fully upgraded with SST outputs and internal dac). In reality not because I thought it would be a perfect match, but because that's what I had available. Build and Design Celsus Sound SP-One
First of all, the packaging on these was fantastic. I know there are some people who really drool over unboxing videos; sorry I don't have one of those for you, but the fit and finish of a slick package really adds to the ownership of a product. The speaker box itself is printed all around and is a significant aesthetic step over the usual black on brown cardboard. The whole thing is double boxed, and the second box fits like a second skin with no extra padding needed. Within the box, the speakers are nestled in fitted foam and each is wrapped in their own soft white linen bag with silica gel packets. Be careful lifting them out of box, as they do not have grills and I nearly stuck my finger through the tweeter taking it out. Learn from me and lift from the sides.
The cabinets of the SP-One are made of a nice solid bamboo; no veneer here. I'll admit I was a bit concerned at first about it looking and feeling like a cutting board, but in person they are very smooth and nice to the touch. The aesthetic certainly sticks out from other speakers that have that typical gloss paint or wood veneer, so in that sense carries a bit more of a modern natural look. They feel solid and don't have any knock or ring to them (they are surprisingly inert in this regard) when you rap them with your knuckle. The ad copy states these are a double cavity cabinet. Opening it up, within the bamboo there appears to be a second wall built right inside, and that itself is further lined with acoustic foam on top. Definitely a very very solid cabinet which explains why the smallest speaker in this lineup is not the lightest.
The back plate is secured via screws, on which an L-shaped port is mounted. There is also the crossover circuit, with some clip on leads to connect to the speakers. Simple, and not really much else to say about that. On the active version, one speaker houses all the amplification circuitry which is mounted next to the crossover. Again, it's a compact affair and nothing too fancy which is fine by me. On the passive version all you'll have is a set of binding posts on the rear plate.
Later on I did do some experimenting and bypassed the internal amp. Obviously this is not something recommended by the manufacturer and would void their warranty, so I won't go into any details on how I did so; but for the purpose of this review I wanted to pair it in passive mode with their most likely partner the NuPrime IDA-8 (which I reviewed separately here: http://www.audiocircle.com/index.php?topic=139386.0
The configuration of the SP-One is a fairly standard 2-way vertical arrangement with the tweeter mounted above the woofer. The woofer itself has a bit of special sauce going on with a patent pending folded ring surround that offers more linear performance in the upper vocal band where traditional woofers falter, and also offers extension down to a solid 50Hz. John Blue JB3
I have to admit, there's something about the aesthetics of the JB3 that really catch my eye. An elegant piano black finish (apparently 1mm thick which is impressive and takes many coats to accomplish) with their very pretty custom driver mounted up top. My photography skills do not do it justice so I won't even try. Easily the best looking speaker of the three in my opinion (though tastes will vary).
The construction is also solid wood. I did not open the cabinet, but you can find all sorts of tasty images and information over at 6moons that describes the audiophile construction in detail.http://www.6moons.com/audioreviews/johnblue/jb3.html
There are easily more boutique components and qualities in the JB3 than the other two combined. Even the binding posts at the back are much more refined than what you'd typically find. The cabinet is not quite as inert as the SP-One, but it doesn't ring and otherwise feels and sounds solid. The JB3 is the lightest of the speakers in this comparison.
Unlike the other two, the JB3 is a one-way design using their own proprietary drivers. At 3" this is also the smallest driver in the roundup by a good margin. Unique in the roundup is it employs a whizzer cone which the other two do not have; in theory the whizzer will increase/control the upper frequency content. Aesthetically, it makes the JB3 look a whole lot fancier. The grill cover is functional but really uglifies everything as it rather juts out and doesn't add anything to the aesthetic. Centrance Masterclass 2504
Last but not least, the 2504 also shares in the solid wood construction of the other two. No MDF or plastic here. Unlike the other two though, it has a front port in the form of a long slot beneath the driver. As a front port, this does allow for placement closer to the wall, which I will talk about later. It is also the largest and heaviest of the trio, though only marginally moreso than the others.
At first glance it appears to be a single driver speaker, but it is in a fact a coaxial driver design. In layman's terms, the tweeter and woofer are mounted on the same axis and also time aligned. While more complex to implement, this allows them to behave as a point source which in theory should offer a cleaner and more coherent sound. With a standard two or three way speaker, the sound is split into their respective frequency bands and originates from multiple drivers thus there will always be a slight "gap" in cohesion, until you are far out enough that the wavefronts have merged; this is grossly simplified of course, but enough to get a basic idea. While the 4" woofer is the largest of the three speakers here, it shares some of that real estate with the tweeter due to the coaxial design so in practice is probably similar to the SP-One's woofer area.
In terms of appearance, the 2504 is certainly the most "business-like" of the trio. It won't win any beauty contests, but it won't get you kicked out of the club either. Now don't get me wrong, the finish is still very nice to behold, and the coaxial driver has the recessed tweeter potion which is kinda neat, but just simply not as cool looking as the JB3 and looks very old fashioned next to the SP-One. On the flipside, this speaker is also the only one with a full front protective grill, which completely obscures the look of it anyways. If you wanted a speaker that you could hide on the desk or shelf, or look like just any other generic noise making box, this would be ideal.
I could not find a sensitivity spec for the Centrance, nor did I make any direct measurements, but based on my listening tests and the very similar specs in everything else, it would not be unreasonable to assume it is somewhere in the high 80's. Quite average for this style of speaker.
A quick note on pricing: the Masterclass 2504 do show up on Massdrop these days for much cheaper Listening
I'm going to start each segment here talking a bit about the required speaker placement, since this by itself affects the sound so much. I will not however make any special accommodations for acoustic treatment, and each speaker's assessments will be given in an untreated room in roughly the same placement unless otherwise noted.
My typical placement for the speakers was on a dining room table, with the back wall about 3-4 feet away, and speakers oriented in roughly a 4 foot equilateral triangle with me at the focus point. Elevation was provided by very unscientific and non-audiophile approved boxes or pelican cases roughly a foot off the table. If I was feeling fancy, I used a binder to angle the speakers up.
Also as a general note, you have to keep in mind these are all bookshelf speakers with small drivers, with cabinet volumes are not much more than a milk jug. As such, keep your expectations about bass within the realm of plausibility and according to the laws of physics. They're all good for what they are, but none are going to work miracles. Celsus Sound SP-One
The SP-One is the only one of the three with a rear port, which typically does not like being up close to a wall. I must say after some experimenting that I found this to be absolutely true in this case. General rule of thumb says you only need a couple inches of space for a rear port, but I felt the SP-One needed at least six inches when at an angle in typical triangular/nearfield formation. If the wall was too close, not only would it start to feel boomy, but you could hear the huffing from the port reflecting off the wall (albeit only when you pushed the volume to undignified levels).
When projecting broadly into a room and facing both speakers forward, I settled on placement roughly a foot out from the wall. Room corners are also big magnifiers, so try to maintain some side distance if possible as well. It didn't muddy as much as a rear wall, and some may even enjoy the midbass boost, but for my preferences I liked to give them as much space as I could for clarity.
On the flipside, desk placement was not a big deal with the SP-One. The initial table reflection did cause some smearing, but even a thin book under the front to angle it up alleviated this. On the flip-flipside, do not put the speakers at the front edge of the desk with a lot of table behind it. This seems to create a bit of an odd honk, I'm assuming from the rear port reflecting off the horizontal surface.
Most listening impressions were done with the speakers in passive mode, with amplification provided by a NuPrime IDA-8. Impressions with the internal amp are mentioned separately at the end.
My general sonic impression of the SP-One was of a very good performing speaker with remarkably smooth and well extended frequency response. Overall low end reach was the deepest of the three speakers by an easy margin. Don't go expecting the reach of something with 12" woofers mind you, but considering the SP-One's woofer is only 3.5" it was absolutely remarkable and was pushing into the mid 50 Hz range. If I had to criticize though, while there is a hefty amount of bass, I did find it somewhat squishy. The SP-One uses the rear port to great advantage to generate that low end reach, but there's no free lunch and it came at the cost of clarity. That all said, this was far from a mess, and the complaint of muddiness extends primarily to the very bottom octave which the Centrance and John Blue lack entirely. Above that region it is reasonably clean. The midbass has a solid feel, more thick than kick. The other two speakers comparatively produce more impact but higher up.
As we transition into the midband things remain reasonably clean and level throughout. It has a very "full" sound, moreso than the JB3 which feels a bit withdrawn in comparison. The vocal range is very strong and up front; I wouldn't say it gets shouty, but it is stronger than the JB3 and 2504.
The midrange into treble is remarkably smooth and even handed, unlike the 2504 which suffers from a narrow dip and the JB3 which tilts up. Here the SP-One shines with a laid-back yet very well balanced tonality, leaning slightly to the warm side of things due to the enhanced bass presence. The cohesion is fantastic throughout the mids; not as "crisp" as the JB3 but more "silky" if I can abuse all the cliché audiophile terminology. If I had to nitpick, while the evenness of the SP-One is the best of the three, it is less energetic in the top end. Great for a relaxed listen, but not if you want something to seize you by the throat or ears. Notable was that I did not hear any discrepancy moving into the treble range, even at close range. Oftentimes when in the nearfield with a two-way speaker system you get a bit of etch when you near the crossover region but I did not notice anything out of sorts here. Not to say it doesn't possibly exist, but it was not noticeable in my listening.
Perhaps it was the look of the bamboo, but one word that came to mind while evaluating the sound was "organic". There was a much more natural character to the SP-One wherein the music sounded effortless and I could more easily forget about where it was coming from. With the JB3 I often felt like it was sound coming through a funnel and I had to step back to enjoy it, and the 2504 was more like a studio monitor that was great for picking out details but not something that you could simply chill out with.
I did not find that the SP-One had a "sweet spot" as most speakers do. Overall it provided very good room filling sound and had excellent off-axis performance. Absolute positioning was better in the centre obviously, but staging was consistently good (not amazing) walking around the room. In this sense I would not classify the SP-One as nearfield, but rather grudgingly place it into mid-field category as it seems to perform well at all ranges but I personally enjoyed it best at middle range. While this speaker did the best at putting music into the entire room and letting me walk around without losing a sense of it, it was not as good as the JB3 or 2504 for telling me exactly where the instruments should be; but again those both had the limitation of requiring you to sit more precisely in the sweet spot.
Now I know this review is comparing primarily against the Centrance 2504 and John Blue JB3, but I want to take a very brief diversion here and mention that I did have the chance to compare vs the Genelec 1030A (predecessor to the current 8040 model; it too being a 2-way ported active speaker). In short, the Genelecs are amazing. They reach just as low but are much cleaner, and their clarity is better up top. If you ask yourself whether you can get better performance in this size package, the answer is yes... but you're paying triple to get it. Note: the 1030 are a slight size category up, the 8020's are closer size-wise; I did not have a chance to compare that one directly but from all reports those in the same family should be reasonably similar. I also have a set of powered Yorkville YSM8 monitors,yet another 2-way ported active speaker. Pricewise for the pair about the same as the SP-One, but significantly larger/heavier. These have better extension at both ends but also suffer from audible hiss from the speakers at close range. So it's a constant trade off of cost and size and performance. So coming back to the SP-One... Have I heard better at that price? Yes, but they were five times the size. Have I heard better in the size? Yes, but it cost three times as much. Pick your poison.
One last note on the SP-One, it can also be driven louder than the JB3 and 2504. This may seem academic to some, but it's an important consideration when compact size is crucial but you still want to fill a room with more than just ambient listening level sound. You can potentially use the SP-One for movie night and have some satisfying rumble while still being heard over kitchen chatter in the background. You couldn't say the same for the other two.
--Internal vs External amping--
I'm going to go on record as saying that I was not a huge fan of the built-in amp. For the price of the active over passive model, and considering it comes with a bluetooth receiver, I think it's certainly worthwhile if you want the convenience factor. I'd rank the stock amp performance roughly in the same league as a Topping amplifier which is in the same budget ballpark, but lacking the bluetooth input. Moving to an external amp really breathes more life into the SP-One... but please bear in mind, I am now comparing the stock amp with the NuPrime IDA-8, which is nearly an order of magnitude higher in cost. Worth noting however was that the stock amp was completely silent with zero noise floor. That's actually a nice feat, considering I've heard more expensive active speakers that could not accomplish this.
With the stock amp, my overall impressions were mostly similar but I noted a few areas in which I found lacking as follows (the gripes are overstated):
- grain in the upper end; slightly raspy when pushed hard
- somewhat withdrawn lower treble, like a slight scoop
- a pushiness in the upper mids
- staging narrower
- midbass slightly hollower, does not seem to reach as low, loses some thump
Moving to the better amp alleviated these issues and more. As I said before, considering the low price point of the built-in amp, if you're going for convenience this is not a bad deal at all. I have heard powered monitors that are bigger and more expensive than the SP-One that do not perform at the same level.
All said and done, the issues are not that big. The speakers in active mode are still an excellent all-around performer, but if you are looking for higher performance and have the money to spend, I can highly recommend pairing the passive version of the SP-One it with the NuPrime IDA-8.
I did also pair it briefly with a Bryston, Lab Gruppen, and Luxman amplifiers. While my notes above pertain predominantly with the NuPrime, these external amplifiers all performed better than the stock amp.
Sigh, I am also going to say on record that I am not a fan of bluetooth (not just this one, I mean *all* bluetooth). I know it has improved in recent years, but to my ears it still sounds like early mp3 compression algorithms from the 90's. My primary beef with it is this grain in the upper registers, rather similar to what I noted with the stock amp in the treble but here it's more like something is missing rather than a distortion product. Along with the grain is also the feeling of a withdrawn upper end at the same time, as if it were slightly muted or if there were a gentle down slow slope over the entire region.
As soon as I switched to analog inputs my gripe with this was over. Of course, my source for bluetooth is my 5 year old (ancient by today's standards) Samsung smartphone, so take that into consideration. John Blue JB3
Overall I found the JB3 the least fussy when it came to placement. It didn't mind being near a wall nor being on the desk surface, and in fact appreciated having a bit of bass reinforcement from either without getting too much bloom. Of course it sounded better/cleaner being away from both, but it didn't get all mushed if it was, unlike the other two speakers mentioned here. On the downside, the JB3 was the one most susceptible to port chuffing (the noise of air huffing in and out of the reflex port) which limited it's ability to drive loud especially if bassy music or sounds were being played.
I had mentioned the whizzer cone earlier, wherein it's supposed to control directivity of the upper frequencies and such. I'll happily report that that does indeed seem to be the case here, as the JB3 had the clearest top end of the three speakers and easily had the greatest sense of "air" and projection. In a way, it reminded me a bit like a horn. Crystal clear and shining, but potentially very forward and could get "heavy" in that light sort of way. There was a broad peak somewhere in the lower treble that contributed to this.
So this horn like presence combined with the port chuffing really made me feel the JB3 was not ideal for nearfield listening. It also tended to have a rather narrow sweet spot where it sounded best. My usual desk position roughly 4 feet away, while supremely detailed and revealing at times, also felt too aggressive.
Reconfiguring into a more typical living room arrangement, speakers 6-8 feet apart, seating roughly the same distance away, this was magical. The horn qualities now blossomed into a fantastic sense of air an order of magnitude greater than the other two speakers, and I could no longer hear the chuffing which was distracting at close distances. The JB3 has the least bass of the three, and while I don't want to say the "most" treble, it easily wins for the greatest upper end presence. I would not classify any of the speakers here as sibilant, but the JB3 is the sharpest of the bunch in comparison.
While the low end of the JB3 is the weakest of the three, it does manage to punch a bit harder than the SP-One in the midbass, but low end extension is weak which is not surprising considering this is the smallest driver in the roundup, and the only full-range one at that. This single driver configuration might also account for the clarity and horn-like qualities which I've mentioned several times now. While the SP-One has a "natural" timbre, the JB3 has a "simple" or "transparent" timbre to it, like the music wants to rise up and be heard whereas the SP-One is more of a settle down and chill. I imagine part of this is not just from the single-driver config but also the lack of any crossover components, giving the "purest" connection from amp to transducer.
Detailing on the JB3 is superb, but narrow focused. The 2504 also has excellent detailing, and provides a better overall view of the music while the JB3 requires that you hone in on each segment separately. In this area these two speakers are stronger than the SP-One.
Soundstage is decent. Really, all three speakers do well in this arena, but all in slightly different ways. The JB3 makes the sound seem bigger than it is, almost as if there were a hint of extra resonance in the room. Great for vocals and small instrument arrangements, perhaps less so on busier recordings. Electronica and other genres that rely heavily on artificially generated sounds in general did not seem to play well with the JB3 either, and sounded too sterile yet hazy. I also did not find it to be a good speaker for movies, rendering voices too shouty and not enough low end for special effects.
As an interesting note, the JB3 is a very nice speaker that plays over top others simultaneously. Perhaps in this way it seems to act a bit like a bootstrapped supertweeter. When I do testing with multiple speakers hooked up simultaneously, there's often that transition moment when I switch to another and haven't turned the first one off yet. Usually that just results in a hot bloated mess (more volume is not better!), but with the JB3 it was like an extra layer of energy and breath up top. It didn't muddy everything down below, but rather augmented it. This wasn't perfect of course, and it worked better on some songs or genres more than others, but it begs for further experimentation.
Along those lines, the JB3 is also the only speaker in this comparison that made me want to experiment with different amps (I have this longing to try an SET tube amp with it. Furthermore it also piqued my curiosity for what the bigger speakers in the John Blue family can do. So while the JB3 doesn't check all the boxes, the ones it did ticked them in such a way that I really want to explore them further.
One weakness of the JB3 is that it has limits to how loud it can be driven before it starts to misbehave. When pushed, it starts to garble and you worry that you might blow the speakers. This puts it in an odd spot as I felt it did not perform best in the nearfield, but now you need more power at midfield range. In this sense it has the sweet spot not just in terms of positioning, but also for playback volume. If you have a reasonably quiet and suitably sized room and are listening to acoustic arrangements, the JB3 are an absolute delight. If you're looking to headbang, this is not the speaker for you. Centrance Masterclass 2504
The 2504 is perfectly happy with its butt up against a wall, which gives it a certain degree of bass boost. While it is certainly humped, I did not find it overly muddy and remained relatively clean (yes there's a certain blur to be expected when you're essentially using the reflection of a phase delayed signal, but it wasn't bloated like other random speakers I've tried in the past).
Conversely, the 2504 hates sitting on a desk surface. I'd wager it has to do with the wide front port at the bottom of the speaker which just produces a very smeared midbass coming off the desk. Far moreso than the JB3 that has the lower front port as well. Placing them at an angle helps somewhat, but a stand (plus angle) is highly recommended. Try to give them at least 6 inches of elevation
My personal configuration for the Masterclass is actually as a bedroom speaker, where I have it placed in an odd position. I have an inset closet in the bedroom which I converted into a desk area. The closet is roughly 2 feet deep and 5 feet wide. I have a small hutch for the desk on which I place the speakers, so there is no horizontal surface directly in front of them. This gives me all sorts of bass reinforcement and it's admittedly a bit honky inside the closet cavity, but smooths out surprisingly well outside of it, and all my upper end sails out nice and smooth.
The 2504 has the largest woofer of the trio here (at a staggering 4", just ridiculous compared to the others), and while it does not have the lowest reach (that honour goes to the SP-One), I would say it does have the cleanest bottom end. With the SP-One you could tell it was a reflex port at play; it's hard to describe, but there's a certain tonality where even if the absolute frequency response is smooth, there's still this hump of energy before you get the rolloff. While the 2504 is still a ported speaker, the "hump effect" as it were is not as pronounced and the energy handling in the low end is more even handed and doesn't produce the muddiness that often accompanies ported boxes. Overall I felt the 2504 had the best "kick" or impact in the midbass of the speakers in this roundup.
My one criticism of the 2504 is that there is a strong but narrow dip in the upper mids, which I'm guessing is most likely the crossover at play. This renders a slight disjointedness in that region when listening to the typical audiophile genre of instrument + female vocalist. In other genres where things are busier, it is not noticeable unless you're really looking for it. It's a shame, because other than that blip I would say the Centrance has the best integration of highs and mids.
The overall midrange is very clean, veering towards clinical. Detailing is very prominent and up front. I've mentioned now that the SP-One has this down low feel and the JB3 seems to lift sounds upwards. As temped as I am to say the 2504 fits right in the middle, that doesn't feel accurate to me. While it does reside in that happy middle zone, it's more like we're taking a bit of a zoom/macro lens and honing in on the music. These are advertised as studio monitors and they do seem to fit the bill. Even despite that narrow dip in the upper mids, I feel the precision of the 2504 is the strongest in this comparison.
Much like the SP-One, the 2504 has a generous sweet spot. Not as wide, but still lets you move a foot off axis and not lose any sense of spatial cues. When you're in the sweet spot though, the imaging and clarity are the best of the bunch and I'd say the 2504 is the most nearfield of the three speakers tested here.
Power handling on paper is the lowest of the three, but in practice I found it to sit in the middle and eeks out above the JB3. While the JB3 distorts quickly under load, the 2504 seems to have more of a compressive behaviour rather than distortive so it isn't as obvious (though this isn't ideal either if you have a habit of overdriving... in which case get yourself something more heavy duty) and remains cohesive much better at high volumes. The TL;DR Version
- greatest low end reach
- keep away from the rear wall
- largest ambience
- plays well at all ranges but best at midfield
- most "organic"
- images like a horn
- not fussy with desk/wall placement
- shouty at nearfield, sounds best at midfield
- very precise imaging but narrow sweet spot
- most "air"
- business class
- needs to be raised on stands, doesn't mind the wall
- best cohesion except for that one crossover spot
- excellent in nearfield
- most "critical"