Sica 5" and 6" hifi coaxials measurements

I have decided to publish full measurements of those good performing coaxial drivers. Coaxial drivers is quite a buzzword nowadays, we all know that the concept generally is very good and has benefits, though real life coaxes suffer from a lot of issues, measured performance is far from ideal. and prices are quite high.
I created 2way loudspeakers from both, and 3way from 5" coax + 6" Sica woofer. Based on listening impressions, feedback from hifi friends, and measurements, those drivers are ones of better coaxes available on the market, and Sica did the engineering right. Both sound very good and make good two way loudspeakers and definitely make good midrange-tweeter for 3ways.
Sica 6.5H 1.5CP
Sica 5.5H 1.5CP

Measurements were done in small enclosures with R28 front baffle edges, mic distance 1m for FR and 30cm for distortion, gating 10ms, SPL calibrated, measurement voltage 2.82V, microphone Earthworks M30.

5" coax assessment:
  • 3kHz dip in tweeter response is trouble and not nice to look at. It makes crossover design quite challenging. Off axis responses are consistent so the issue is correctable with active crossovers.
  • distortion performance is good for basic drivers and does not suggest any big issues
  • tweeter top end response is not perfect, though is much better then what we usually see from other coaxes
  • we had side by side comparison with KEF LS50, LS50 measurements showed elevated 3-kHz area if I recall well. Sica sounded better in all aspects.
6" coax assessment:
  • 3kHz dip again. Off axis responses are consistent so the issue is correctable with active crossovers.
  • distortion performance is good for basic drivers and does not suggest any big issues
  • tweeter top end response is not perfect, though is much better then what we usually see from other coaxes
  • I attached also Vituix 6pack for completed 2way passive loudspeaker, this version sounds very good, has reasonable low end extension and overall listening impression and feedback was there was something really right and good in the sound
  • small wrinkle at 800Hz is front port interference
Both are visually very nice drivers, though some details are not perfect, for example consistency of the glue ring and surround centering.
I am also glad they use paper cones with some kind of coating, which means less severe breakups and generally better sound then alu cones (I am not a fan of KEF sound at all, though I admit Meta versions might be step in the right direction to better sound)

Crossover design for both was not easy due to 3kHz tweeter response dips. Standard two way 6" + WG is much easier. Acoustic LR4 at 2000-2500Hz is mandatory due to a) tweeter: rising distortion <2kHz, b) better directivity match, c) uneven response of midwoofer >2.5kHz.

I have lived with those 3 loudpeakers/projects for ~2years and have a lot of experience and comparison to standard 2ways and 3ways. They sound very good and for the price there is very little to complaint about. But ClassIllu 2way (Scan Speak 18W/8545K00 + 6600) beats it in every aspect. It is not fair comparison, ClassIllu drivers cost is much higher, though it tells me that coax is not the only feature that makes a good sound or would be the only prerequisite for the good sound.
 

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I have been playing around with the 5inch coax in a tear drop shaped experimental enclosure along with Satori WO24P woofers in 3way. Those adventures and related measurements are given around this page:
https://www.diyaudio.com/community/threads/a-3-way-design-study.376620/post-7115048
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My recent ongoing 3way project with thile 5inch coax in an open cardioid enclosure is also given at the end of the above thread
IMG-20230520-WA0014 (1).jpg
 

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The 5" Sica coax is a very nice sounding driver.

IMO, the Seas H1353/T18REX sounds a bit better than the 6" Sica, especially as a full range solution without a sub. Its capable of decent bass extension in a ported enclosure. Very few small coax drivers are able to work well without some form of sub or dedicated LF driver.

Used as a mid, the 5" Sica is capable of higher resolution compared to other similar priced small coaxes. It makes for a capable nearfield monitor driver. On paper, the tweeter FR looks worse than it sounds.
 
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I noticed I did not attach correct sixpack for 6" coax 2way T2, so here it is, Sensitivity matches the individual measurement of the midwoofer. This is final version, proven by longterm listening.

I also attached T3 sixpack, this is standmount 3way with 5" coax and 6" Sica woofer 6.5H 1.5C
 

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Marveloudio: in my view these are good drivers. Measurements are not perfect, but they are good enough, showing less issues then SB/Seas/... drivers. They are quite cheap drivers, look good, and sound really nice. Definitely ones of the better coaxes available on the market. You cannot expect miracles.

If there is anyone looking for decent coax, I can recommend those. To get better sound, one would have to invest more.

I have decided to try those because I wanted to have experience with coax drivers. These looked the least worse, and my measurements + listening confirmed.
 
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Thanks for posting all this. Very good information! Cool you are rocking with passive filters.

Would have hoped for lower distortion on the tweeter (being able to cross with more shallow filter). But guess you cant have it all.

I have yet to experiment with coax. How would you compare the sound against midwoofer and tweeter with good WG?
(For instance SB17 and SB26 tweeter in Waveguide or similar drivers).

In Siegberg Audio Manta speaker, it look like it can play rather Loud if asked for.
 
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@ Pida

Did you get a chance to try the "over-toe" with the 21W/8855-10 + D3004/6600 waveguide system or coaxials? So that the on-axis of the 2 speakers intersects in front of the MLP ?

I'd be most curious to read about what you think after you did that.
 
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Tweeter distortion and possibility to cross over low or with shallower slopes are usually the issue in coax. Due to space constraints tweeter is very small, almost no chamber.

First I should describe my listening space as it pre-determines my conclusions. I listen in my hifi workshop. Room 5x6m, acoustic diffusors on the sides and front wall, a lot of furniture with speaker stuff etc. Listening distance ~3-4m, I move sofa sometimes closer or further.
Generally, I like the sound from those coaxes a lot. I was quite skeptic at the beginning though. After some crossover tuning and listening sessions I like the sound. I cannot say I hear some difference of the sound compared to 6+1 or 6+1+WG which I could attribute to coaxial arrangement though. Certain aspects are similar to 6+1+WG because both have WG => similar behavior in the room. Compared to 6+1 it sounds different because 6+1 gives the impression of wider scene due to more more energy coming from the reflections. I made 18WU+12MU+T25B, without WG, and this loudspeaker had the widest scene I have experienced so far due to T25 firing full energy not only on axis but also off axis. I cannot say it sounded bad, it was just different type of the sound. If I had to pick, I prefer 4-6" Waveguides which sounds somehow clean and clear, correct, the scene is well defined, sweet spot is wider, and ~3-6kHz area is not that problematic.
So 6+1+WG and 6" coax sound quite similar in certain aspects.
If we decide to go higher with drivers cost for 6+1+WG the benefits are the side of this arrangement, I mean better bass and generally better behaved drivers + flexibility with crossover points and slopes.

To be more specific, SB17 is not my cup of tea, though something like 18W Discovery, Seas ER18-U18, Sica 6.5H 1.5C, + "XT25" Discovery in WG, Scan Speak 9130, SB26......these combos would likely be little bit better compared to coax. But I have to admit this all depends on listening environment and ears sensitivity to vertical problems of non-coincident drivers arrangement.

Would have hoped for lower distortion on the tweeter (being able to cross with more shallow filter). But guess you cant have it all.

I have yet to experiment with coax. How would you compare the sound against midwoofer and tweeter with good WG?
(For instance SB17 and SB26 tweeter in Waveguide or similar drivers).
 
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I have it on ToDo list. I moved 21W 2way to my house and system is not connected yet, so there is good opportunity to try over toe-in soon.
I currently work on finishing Discovery10 in the workshop. These start to sound very good.

@ Pida

Did you get a chance to try the "over-toe" with the 21W/8855-10 + D3004/6600 waveguide system or coaxials? So that the on-axis of the 2 speakers intersects in front of the MLP ?

I'd be most curious to read about what you think after you did that.
 
Thank you for your introducing the sica coaxial speakers!

I'm a beginner to the speaker building world. But I'd like to build a small 2 way speaker for desktop use, and the sica 5" coaxial intrigued me a lot.
If possible, could you please open the network of the speakers?

I'm currently studying the cross over network published by the sica itself. But I'd like to get more reference for the network.
I prefer the passive network, because I don't have the active crossover.

Thanks in advance.
 
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Thank you for your introducing the sica coaxial speakers!

I'm a beginner to the speaker building world. But I'd like to build a small 2 way speaker for desktop use, and the sica 5" coaxial intrigued me a lot.
If possible, could you please open the network of the speakers?

I'm currently studying the cross over network published by the sica itself. But I'd like to get more reference for the network.
I prefer the passive network, because I don't have the active crossover.

Thanks in advance.
Here you go. Translate if you like or have to.
 
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I just placed a order on two 5.5 coaxials. Thinking about which cab to build for them, the Sica datasheet suggest a volume and crossover but doesn't suggest cabinet dimensions. Are not crossover picky with baffle dimensions? I'm also thinking about fiancino or fianco, but if I'll go ported I want to make a round port and other dimensions than the fianco, I don't like the look of a big cube that much, Fiancino looks slim and nice tho! I ordered port pipes which is of equivalent length and cm2 area as fianco, but 90% of the suggested port in Sica paper.

If I can get away with a simpler crossover network like in the Sica paper it's nice, it looks to have a similar linear response as the fianco which has more than twice the components.
 
Thanks looks interesting, I made an account to find a pdf or plan for it, but they never sent me an activation mail (they wrote I need to beember to get the plan for the speaker). Hope it's on its way so I can examine the cabinet a bit more. What would be beneficial going small ported compared to small sealed (Fiancino)?
 
Just listening to my own design with the 5.5c, sounding awesome. They are bi-amped using my Line 6 HX stomp as DSP. I'm experimenting with delay and I think I like .4 mS delay on the tweeter. Thanks for streering me to these coaxials.
 

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I just placed a order on two 5.5 coaxials. Thinking about which cab to build for them, the Sica datasheet suggest a volume and crossover but doesn't suggest cabinet dimensions. Are not crossover picky with baffle dimensions? I'm also thinking about fiancino or fianco, but if I'll go ported I want to make a round port and other dimensions than the fianco, I don't like the look of a big cube that much, Fiancino looks slim and nice tho! I ordered port pipes which is of equivalent length and cm2 area as fianco, but 90% of the suggested port in Sica paper.

If I can get away with a simpler crossover network like in the Sica paper it's nice, it looks to have a similar linear response as the fianco which has more than twice the components.
Please keep us posted how these look out of the box in terms of quality and fit/finish. The last two sets I received were a bit rough looking with some concerns of the way they were assembled. I guess for the price its a bit of a gamble. Hopefully they'll be ok.
 
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