Is One Speaker Driver enough? Pearl Acoustics Sibelius REVIEW

Review

This is a review written by Terry Ellis August 2022.

For my video review please see my YouTube channel link here

The Pearl Acoustics Sibelius is a unique speaker which dares to be different. This is because it’s a traditionally sized floor standing speaker, but one that uses only a single driver. Despite the obvious technical advantages, such as it being a single point source speaker with no crossover needed, we don’t see this design used very often.  If you’re an audiophile who has been around the block a few times, you will know why and, no-doubt, have a preconceived idea about how single driver speakers sound and their limitations. However, driver technology keeps getting better, and so can the Sibelius break the mould, and is one driver all you need?

You can put me in the preconception category and when I was asked to review the Sibelius I was initially hesitant because, given the kind of speakers and sound I like, I didn’t think any single driver speaker would work for me. But this review is not about me, it’s about how the Sibelius will suit you. I can say, off the bat, that I have been more impressed than I expected to be. With a price tag of €4,500, plus shipping and taxes, this is not a cheap speaker and so I need to scrutinise them in the same way I would a multiple driver speaker.  I will therefore be comparing the Sibelius to the new Mission 770, my reference speakers, which cost a fair chunk less, but deliver big for the money. I think you may find this comparison very interesting.

What’s the Story?

The Pearl Acoustics Sibelius speakers are the result of a twenty plus year project and there is no one better to tell you the story than the designer himself. Harley Lovegrove and Pearl Acoustics have their own YouTube channel with Harley telling you the speaker’s story and more.  There is no need for me to repeat any of that, you can follow the link. However, what I will tell you about is a long conversation I had with Harley when I asked him some very simple but important questions. The main question being “why a single driver speaker?”.  He gave me a great answer. He said, “if you can get everything you need from one driver, why would you use more”. He explained things a little further and used the example of a microphone. “I have one here, and this microphone has a single capsule, which in many ways is like a speaker driver, and it can capture sounds from 20khz to 20hz, the full audible range”, and so Harley’s chosen speaker driver, which is bespoke to Pearl Acoustics, the 4 inch Markaudio wide-band driver, he feels is the right size and driver, in the right cabinet, to deliver the same full range sound.

It goes without saying that the driver is clearly extremely important for a single driver speaker and, although there are advantages to using a single driver, there are also limitations.  One of the limitations being the sound pressure levels achievable, the amount of air being moved, and how you perceive that as part of the overall delivery.  I was told that the driver’s profile is shallower to allow for a wider listening sweet spot and, being a single driver, means there is no crossover, so no crossover distortion or phase issues. But that means you cannot use the crossover to tune the speaker performance. What you will be hearing is more of the driver’s raw performance for mid-range and treble, which again emphasises why the driver is really important for a speaker like the Sibelius.

Build

The cabinet is crucial for every speaker but extremely crucial for the Sibelius sound and performance. For starters the cabinet is made from real wood, French Oak to be precise. Visually, each cabinet will have its own unique wood character and pairs must be matched as closely as possible.  Harley told me that it is a challenging process to build cabinets from real wood because the wood wants to take its own shape. Because of this, there is an eight-week drying time for every cabinet. This is pretty extreme when you think about it. Thick French oak is used and so that the cabinet is inert and Harley made the decision that the cabinet would not colour the sound of the speaker.  What I found very surprising is just how much I liked the look of the speakers in my room.  Looking at pictures and some other videos, I didn’t think I would like them visually but, in the flesh, they look really good, and their slender shape is very appealing. The finish on the review pair was natural, although there are several different colour finishes to choose from. The driver was the SG model or ‘silver’ and you can choose between this or the CG, which is a copper finish driver, both are identical for performance. I like the idea of customising your speaker to suit your room or preferences.

One downside to the design of the cabinet is a flat base, which means that on my short pile carpet the speaker was not stable at all and would certainly not be child or even dog proof. There are dedicated Sibelius stands designed to solve this. The stands are quite heavy and quite understated in design. You can level them using the supplied spikes, and the Sibelius literally just sit on the stands (not fixed), improving their stability no end. The stands also raise the speaker off the ground to allow for air from the port to flow underneath, which is designed to improve their bass.  I think the stands will be essential in a lot of cases and so best to budget for them at the time of purchase because at €350 plus taxes and shipping, they are not cheap.

Another thing to consider is the positioning of the speaker terminals. They are high up on the rear of each speaker, which only really matters if you have very short speaker cables which may not reach and might need replacing. This may be an additional cost to factor in. Pearl Acoustics sell their own speaker cables which they included for the review. However, I didn’t use them because it would be too much of a change to my system all at once, and this is a review of the speakers, not the speakers and cables together.

I think the main reason that the terminals are so high is likely due to what we cannot see on the inside of the speaker, and that is its quarter wave V horn. I asked for some images to show what this is, and I was told it is a Pearl Acoustics protected design and so sadly I don’t have anything to show you.  I am sure like any horn or speaker port it will be as you would expect, a clever method of using the back wave pressure from the driver that travels through the quarter wave V horn extending the bass, and maybe improving the sound pressure level of the bass and at the same time keeping it in phase. This is the clever part of the speaker’s design for achieving deeper bass from a very small driver that only has a limited movement range.  All we see is the vent-type port at the bottom of the front of the speaker, which made me think they were a transmission line design, but not in this case.

Sound Quality

For sound quality the Sibelius is very much amplifier dependent, so much so I made a video discussing some of the differences I experienced with the three amplifiers I had been using.  I ended up using the Leema Acoustics Tucana II Anniversary the most because I preferred the overall synergy. The Leema is a high-power, high-current Class A/B solid state integrated amplifier.

What I hadn’t done at this time was measure the speakers. Some of what I saw in the measurements made more sense out of what I had been hearing. I’ll start with some of the big audible ‘pros’ of the Sibelius and then some of the shortcomings. The Sibelius are quite a tall speaker, and which means that the driver is set quite high. I don’t know if that is the only reason, but I really enjoyed the height of the sound stage they delivered. It is not something I often think about, but it is something I noticed here. The second ‘big thing’ is the soundstage width, depth, and coherency. The musical images and elements within the soundstage had very noticeable layering with a good amount space between them. Transients were always presented cleanly, but on the softer, smoother and more graceful side of what I would class as neutral. I mostly noticed this for vocals.  In fact, in the main, the speakers sound very smooth and graceful, which is why I think I preferred a more upfront and lively sounding amplifier with them. I also think that in order to achieve this type of excellent soundstage, the speakers need to be transparent. It seems that the very inert French Oak thick-walled cabinets are doing their job well and, as Harley required, not adding any colour to the music, as that would blur or thicken the sound.

I found the overall balance of the speakers’ presentation to be very even handed. By that I mean the bass well balanced with the treble and mid-range. I also found the treble to be slightly forward but, because the delivery is so smooth, you don’t really hear it as forward. Instead, treble details just pop more from the background so that small details in music are resolved very clearly. When you combine that with the speed of the single driver, a fast percussive Spanish guitar like Rodrigo Y Gabriella, sounds wonderfully inciteful. In some electronic music, such as Faithless, I noticed the treble details in some of that track were floating around my head in a surround sound like effect, which was very cool and impressive.

The bass from the Sibelius was certainly not massive in output, and not as tactile as many other speakers I have had in my room, but it was surprisingly satisfying in terms of extension, smoothness, control and timing. I did find the Sibelius sounded like they have been tuned for bass extension rather than mid bass fullness or punch, but that meant that they always have a wide-open sound stage. The trade-off is big male vocals, which don’t sound quite as bold, and electronic music, which doesn’t kick you as hard, or the bass doesn’t quite pressurise the room or your body as much.

I found the Sibelius sound to be quite precise overall, very tight, nicely focused and great for the small details in music, favouring those element over a larger and grander scale of sound. In various Hans Zimmer, and other movie soundtracks, the small details are clearly presented and the music flows wonderfully, but the overall grandness of scale of the music is a little subdued and less epic.

I appreciate I am well into preferences here for how I how I like music to sound, how loud I listen and how ‘big’ I like it to be. You also should bear in mind that my listening room has a lot of acoustic treatment, allowing me to listen much louder than in a normal, more reverberant room, without any listening fatigue or strain. Throughout this review I had concerns about the volume levels. I need to be careful here in how I explain this because I have been listening quite loud, as I always do, and I haven’t heard a single bad or bum note from the Sibelius because resulting from an overworked driver. However, there is a recommended volume limit on the website of 96-98db, making me feel much more conscious of the volume I was playing music at than I normally would be.

Interestingly YouTuber Ron of New Record Days, recently did a listening volume poll. From over a thousand audiophiles, it seems like most listen at a much lower volumes than me and so the 98db volume recommended maximum is likely going to be fine for the majority.

To summarise my experience with the Sibelius, they are great for giving you a very relaxed intimate and detailed musical experience with no listening fatigue and, regardless of my preferences of how I like music to be presented, at the end of many multiple hour listening sessions I enjoyed all of them, surely that is what is always most important.

Comparison with the New Mission 770

A good place to start is by looking at how both speakers measured in my room. There is a lot you can discern from the differences.  Firstly, with the Sibelius, you can clearly see that, with room gain, they are delivering almost a full range sound from bass down into the 30Hz levels, up to about 16Khz before serious roll off. That’s pretty impressive for a single 4inch driver. Comparing with the Mission 770, because of room acoustics, there are bass and other similarities. However, you can see the Mission have much more output at the very low end and in the 100hz region, but the Sibelius is close and just as well behaved in a lot of regards. Don’t forget, that’s comparing a 4inch wide-band driver to an 8 inch mid bass driver and 1 1/4 inch tweeter.

Of course, this does not tell us the full story. The upper mid-range and treble region comparison is where things become more interesting. You can see that the tweeter in the Mission is more well behaved for frequency compared to the single driver of the Sibelius. You won’t hear the peaks in the response as you can see them in the graphs, but it does explain why treble details pop out more, as I mentioned previously.  Both speakers roll off the lower treble in the upper vocal region, probably for a smoother sound and more emphasised depth to the sound stage, but the Sibelius do this more extremely. I am sure this is an indicator of the very smooth sound they deliver, a sound that’s always quite set back compared to the Mission which sound forward by comparison. Graphs plotted like this normalise averages of multiple points measured in the room. They don’t show you everything, but they give you a good general indication of a speaker’s behaviour and character.  Neither speaker is text-book neutral, but the Mission is definitely the more neutral of the two.  Both speakers have some distinct character, but I would say the Sibelius has a strong character, especially in the upper vocal and treble region and this is probably why amplifier choice is very important with them.

But that is all just squiggly lines and technical jargon. What are the main sonic differences between the speakers? I started the comparison using the Leema Tucana amplifier. The first thing I noticed was that the Missions sounded larger, more energetic, or with more energy to their music delivery. There was more mid-bass presence from the Missions which I preferred, but a less smooth transition through the bass range which I didn’t.  The mid-range from the Missions sounded more disjointed from the bass and treble compared to the very cohesive sound of the Sibelius. The Missions were more forward and more immediate sounding but there was a little bit of ‘grit’ to the sound too. I would also describe the listening experience with the Mission as being very up close and personal, whereas the Sibelius was like you are looking at the music happening in front of you.

Using a music example such as the Rodrigo Y Gabriela and percussive Spanish guitar I mentioned earlier, I think the Sibelius sounded more like a how a microphone might pick up the sound of percussive guitar playing. There were a lot of intricate details and a very focused sound, whereas the Missions gave much more of the overall energy and impact of the music, as though it is happening live. I have been up close to and recorded an exceptional percussive guitar player JonJan Kavlakagou so I do have a real world audible references to call on here.

The Leema is not the ideal amplifier for the Mission speakers, and so I changed it out for the Pass Labs INT25, which is a pure class A single-ended type design solid state integrated amplifier. Now the comparison was totally different. The Pass Labs combined with the Missions sound fantastic, especially with vocals. This is a great pairing because there is now real smoothness to the delivery and they sound significantly more cohesive between the bass, mids, and treble. As a trade-off, they are a little bit less attacking and live sounding.

Using The Pass Labs, the Missions sound the more solid and meaty of the two speakers. I think mostly because of their more solid upper bass and how that balances better with the amplifiers’ character. Listening to Agnes Obel on both speakers, the Mission deliver in every area of the track, scale detail, musicality, solidity sound stage. Overall it is very impressive. When switching to the Sibelius they sound very top end focused and the sound lacks the scale and the body to the music through the lower mid-range and upper bass.  The INT25 is still underpowered to get the maximum from the Missions, but it was producing a better balanced and more enjoyable overall sound through the Mission 770 for how I like music to be presented.

Conclusion

To wrap things up I considered who the Pearl Acoustics Sibelius are for. To my mind they are for audiophiles with smaller to medium sized rooms, who listen more at moderate volumes and who are really into musical details, and differences. They are audiophiles who appreciate a tight tuneful bass that’s modest in output and won’t upset the neighbours or other people in the home. They are for audiophiles who are big on sound stage, instrument placement more so than sound stage grandiosity, and who prefer fine intricate detail of sound over outright energy and attack. Also, they are for audiophiles who maybe have to place speakers near the walls and don’t want to suffer boomy bass.  Buyers need to be happy to try different amplifiers to find the best that works for them, with the Sibelius, in their room.  I think the Sibelius have a strong character. By that I mean a way of presenting music with their own thumbprint on it.  Speaking to Harley, he said that he designed them so that when he closes his eyes, he can see real instruments being played in front of him in a concert hall. That is the intended character of the speaker and may be appealing to you.

I have been impressed by the build quality and the look of the speakers. I also like Pearl Acoustics approach to customer service and giving customers a buying experience that is a little more personal and special. These experiences don’t make any difference to the sound but do make a positive difference to how you feel about spending this kind of money.

I want to close out by saying this has not been an easy review for me. Critiquing another audiophiles twenty year speaker project is almost like criticising one of their children. It is not something you do without extreme care and honesty about your findings and that is how I have approached this review. If that is an approach to HiFi reviewing you appreciate, please subscribe to see my YouTube videos and follow my website and Facebook page.

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