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5.5" coax project using Sica 5,5 C 1,5 CP drivers

ppataki

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After building close to 20 projects using full range drivers and subwoofers and then a two-way system I have decided to strike out one more item on my DIY bucket list: building a coax driver-based speaker

I have chosen the Sica 5,5 C 1,5 CP driver for this project based on the manufacturer published measurements and based on this ASR thread here.

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Let's see what I will be able to make out of it!

To start with I have an old pair of sealed cabinets that I used to build for this project. After that they were just sitting in the attic so I thought let's re-purpose them for this new one

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The Sica coax drivers shall look like this in this cabinet:

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X-max limited max power will be around 45W (at 80Hz where the high-pass filter will pass it to the subs) producing 97.4dB (103.4dB for a pair) of SPL at 1 meter

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The drivers will hopefully arrive before 6th January but let's see
I will post pictures, stay tuned

Happy Holidays to all of you in the meantime! :)
 
If you can chamfer those edges even just a bit, that should be quite beneficial. Those coaxes have a nice continuous curvature to the surround/frame that kinda emphasizes the need
 
If you can chamfer those edges even just a bit, that should be quite beneficial. Those coaxes have a nice continuous curvature to the surround/frame that kinda emphasizes the need
The plan later is to put the speakers in sphere cabinets but first I want to test them in this spare box to see/hear how they perform
If they are good enough then they will replace my full range Markaudio MAOP drivers and the Adam T5V mod project too but if not then I will probably get back to the full range spheres with the MAOP drivers (I really do love those)

Other updates:
Forgot to mention that the coax speakers will be driven by a pair of Sabaj A30A full-digital amps, crossover will be done in Jriver (will try various settings to see which one is the best) and also integrated with two subs in the living room
 
Just a small update

The cabinets are almost ready, the acoustic treatment is finished:

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See a knock-knock test here

The only thing missing is a ring to reduce the baffle cutout so the Sica drivers would fit in - hopefully that will be done tomorrow

The drivers are on the way since Monday but apparently they will not arrive until next Monday unfortunately...
Stay tuned!
 
The cabinets are now ready (MDF ring added to reduce the baffle cutout)

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And finally the drivers have arrived!
IMHO they look beautiful

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I will put them in the cabinets today and hopefully I can even listen to them in the evening - will post further pictures and measurements too
 
This is how it looks like when completely assembled; please disregard (the lack of) aesthetics, this cabinet is only for testing purposes

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Now let's see the measurements! All from the MLP (~250cm)

I need to say that these drivers are not too linear...

Woofer:

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Tweeter:

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So the first thing I did is to fix the response with some pre-EQ, the woofers needed 9 filter, the tweeters needed 5 filters

Huge improvement:

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Then I went ahead and applied a crossover using Fabfilter Pro-Q 4. I was experimenting with 2000, 3000 and 4000Hz (all linear phase, 24dB/oct. Linkwitz-Riley) but there was no real difference between those:

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So I have checked the temporal graphs too and to me the one with the 4000Hz crossover looked the best so I went with that
Of course I have also listened to all three settings but could not hear any real difference....

Here is the step response:

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You can clearly see that the coax speaker is 'seen' by the microphone as a one-way speaker (you can't see the time delay between the woofer and the tweeter - since there is none)
I find this really great but more on that later

Group delay:

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Then I went ahead and integrated them with the two subs in my living room:

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Then applied Dirac:

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Group delay:

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Wavelet:

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Peak energy curve stays well below 10ms thanks to the correct integration of the subs using linear phase crossover + the linear phase shelf corrections
(there is no audible pre-echo)

I must say I am really satisfied with the end results! These drivers are a bang for the buck (70 EUR each from TLHP once back in stock)

Now some subjective evaluation:
(note: I totally cannot prove the below with measurements, hence subjective)

- before this project I did another one about modifying an Adam Audio T5V just to learn fully active mid/high crossover handling and to hear how a good 2-way system sounds compared to my beloved full range drivers. The Adams sounded great, really really detailed and dynamic highs thanks to the ribbon tweeter but the sound stage was not nearly as holographic as with the full range drivers (even with fully time aligned woofer and tweeter on the T5Vs). There was no 'live sound' feeling at all. I was extremely happy when I heard these Sica coax speakers, their sound stage very very closely resembles that of full range drivers! So if you are having a traditional 2-way or 3-way speaker and you want to listen to how the sound stage can become holographic but you refuse to use full range drivers then the coax can be a great alternative.

- apart from the phenomenal sound stage I can comment on the midrange clarity - I really do like how vocals sound

- treble is not as dynamic and detailed as with the ribbon tweeters but in turn they are non-fatiguing and can be enjoyed for long hours (even compared to full range drivers they are less fatiguing)

- you definitely need a subwoofer for these drivers, they are small and me crossing them at 80Hz is already on the borderline

And finally a video (with Dirac and the two subs)

Any questions/comments please don't hesitate!
 

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So, all your measurements are at 250cm in-room? Looks like impulse right window gating was 300-500ms.

Measurements include many room reflections that make impulse, spl and phase go up and down.
Left and right speaker were on same stand, not at listening setup?
Based on on-axis response at 250cm, speakers must sound quite cold!

That Sica seems to be a very good coaxial. However woofer is so small (Sd) that it is actually a midrange, suited for 3-way speakers

Baffle effect sim
ppataki coax proto edge.png
 
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