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Kef R series dual concentric

Digital_Thor

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@ Zvu - This an interesting build :) I just got to make midrange and WG integration work out pretty well.... then stumbled upon a set of Seas C18. But they have a bit of tricky off-axis in the upper midrange. Your Uni-q seems much smoother there... even though the Seas plays very well... I kinda always have the itch :D

Even the Little Q150 looks very easy to EQ and implement in a bigger floor standing DIY build.... like with 2x 8" woofers - for example.
https://www.erinsaudiocorner.com/loudspeakers/kef_q150/

How would you say that the little R-model you have, compares to the one in Q150. Because I find it a little tricky to maneuver around the different driver from KEF :oops:

These look really good:
https://eu.kef.com/products/ci200rr
But so is the price :facepalm: Would the tweeter be any better... and would I merely pay a lot extra for magnet grill and passive filters?
 

nc535

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I suspect the extra bucks are for the larger woofer. One benefit of the larger woofer is less cone movement for the same SPL which means less doppler of the treble and less of a discontinuity between woofer and tweeter cone. So it might be worth it, depending on your budget. If you could get Amir or Erin to measure it you would have a better idea.
 

Digital_Thor

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I suspect the extra bucks are for the larger woofer. One benefit of the larger woofer is less cone movement for the same SPL which means less doppler of the treble and less of a discontinuity between woofer and tweeter cone. So it might be worth it, depending on your budget. If you could get Amir or Erin to measure it you would have a better idea.
My plan was to use it as a dedicated midrange, rather than try and make it play bass, which I already find my 2 x 6,5" woofers can't fully do - IMO - I need minimum 2 x 8" to reach my 4 subwoofers properly.

The KEF driver seems way smoother, than my Seas C18:

https://www.erinsaudiocorner.com/loudspeakers/kef_r3/


Not that my Seas C18 is not doing great.... but I believe the KEF could be very good with active control, EQ and DSP.
 
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Zvu

Zvu

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How would you say that the little R-model you have, compares to the one in Q150. Because I find it a little tricky to maneuver around the different driver from KEF :oops:

They are different. R coax is dedicated midrange and not suited for crossover points under 200Hz at 24dB/o. Q coax is midbass and can be used much lower. Linearity and distortion profile are better in R. If i would be looking at Q series, i'd look for used Q100/Q300. They are better crafted than Q150/Q350 and can be found cheap. There is a great thread by MrSticha at diyaudio.com about something of that sort.
 
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Digital_Thor

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They are different. R coax is dedicated midrange and not suited for crossover points under 200Hz at 24dB/o. Q coax is midbass and can be used much lower. Linearity and distortion profile are better in R. If i would be looking at Q series, i'd look for used Q100/Q300. They are better crafted than Q150/Q350 and can be found cheap. There is a great thread by MrSticha at diyaudio.com about something of that sort.
Thank you. Reading through that thread, it seems that all the Coax's have a resonance around 1-1,5kHz. Is that just part of the design - and does it matter in an active DSP system? I found a pair of used drivers from a set of R3's - and they are like half the price of my C18 :oops:
 
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Zvu

Zvu

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Reading through that thread, it seems that all the Coax's have a resonance around 1-1,5kHz.

How did you arrive at that conclusion ? Only Q series coax has suspension related resonance. Other Z flex suspension drivers are coated to adress that.

... does it matter in an active DSP system?

In my opinion it shouldn't be a problem.
 

Digital_Thor

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How did you arrive at that conclusion ? Only Q series coax has suspension related resonance. Other Z flex suspension drivers are coated to adress that.



In my opinion it shouldn't be a problem.
Because I made an error - sorry :facepalm: So yes.... you are right. The R series should be free from this :D

Is this model from the old or new series?
SP1753AA
 
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Zvu

Zvu

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R-2018, so 12 gen but not meta.
 

Digital_Thor

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Quicker than expected.... it's going to be a good weekend :p Thank you, to some German guy from Ebay called Alex, that also packed them nicely, so I received them in good shape :D For some reason - that I haven't figured out yet - they made the flange very small and narrow, even though the plastic ring covers a way larger diameter - weird. So it seems that wires has to be mounted after the driver is, since the space will be limited. Unless I find a spot where the edge is not super narrow because of the notch in the flange.... which seems way bigger than necessary. Oh, well... someone thought of something.... I just have to figure it out - my way :cool:

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hifi-alex

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Quicker than expected.... it's going to be a good weekend :p Thank you, to some German guy from Ebay called Alex, that also packed them nicely, so I received them in good shape :D

You‘re welcome - have fun with these beauties ;-)
 

Digital_Thor

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You‘re welcome - have fun with these beauties ;-)
The world is smaller than we sometimes think - especially online ;)

Just read about your builds, and I still have the Seas DXT after reading through Heissmann's homepage and donating his great work. Controlled dispersion is definitely the way to go for me :D But Coax's does something special, by keeping you in the sweet-spot and stereo-illusion, over a larger area.
So to me. You can definitely have an awesome experience with WG tweeters and well-matched midranges. But since I move around my apartment. The Coax keeps me in the music over a larger area, because the shift between the horizontal and vertical dispersion variations, are simply less pronounced.

Gonna be a fun build in the workshop today :D
 

alex-z

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Digital_Thor

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KEF uses it to extend the directivity control of the mid-range.

Yup... I'm with you so far. But the flange of the driver itself, is very small, leaving very little to put screws in when mounting this 2kg driver to the baffle. Since the plastic covers everything anyway, why not just make the flange bigger, leaving more air for the rear of the driver to breathe and also make it easier to build a proper structure in the baffle - IMO.
I might end up with machining something in aluminum to get things precise. Wood seems questionable with such tight tolerances + the mounting for the ring - which I still have no clue how to mount properly. Maybe some rubber insert in the baffle, could hold it in place....
 

Digital_Thor

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Getting closer to my final build, moving away from test boxes :p
When calculating the volume for the coax, I mostly see people doing passive. When doing passive, it seems that the Q of the box play a role, that should be less of an issue with active systems, since I connect the amplifier directly to the driver (running fully active here) - I could be wrong - have never done passive - so I'm sorry in advance :facepalm:

So... do I benefit from a bigger enclosure? Less enclosure reflections? Clearer midrange? Or is 3-4 liters just fine in an all square box?
 

Alex1022000

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I would suggest to use a non Square volume to reduce reflexion. i did use a truncated pyramid aka Ikea plant pot(https://www.ikea.com/de/de/p/vildapel-uebertopf-bambus-90233613/) i added a spacer to increase volume.
https://www.diyaudio.com/community/...ding-with-kef-coax-active.385321/post-7041879

If i remember correctly the volume was about 2liters in the end, i wanted a bit more but in the end it was fine according to my measurments.
3 to 4 Liter is plenty enough.
If u have the Space Go for a wood Bowl like: https://www.ikea.com/de/de/p/blanda-matt-servierschuessel-bambus-60214343/#content
get creativ local homedepot, Ikea etc. is perfect for looking for volumes U can also use cylindric shape.

i also would suggest to make an own thread for sharing your Build it should be worth it to document it.
 

Digital_Thor

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I would suggest to use a non Square volume to reduce reflexion. i did use a truncated pyramid aka Ikea plant pot(https://www.ikea.com/de/de/p/vildapel-uebertopf-bambus-90233613/) i added a spacer to increase volume.
https://www.diyaudio.com/community/...ding-with-kef-coax-active.385321/post-7041879

If i remember correctly the volume was about 2liters in the end, i wanted a bit more but in the end it was fine according to my measurments.
3 to 4 Liter is plenty enough.
If u have the Space Go for a wood Bowl like: https://www.ikea.com/de/de/p/blanda-matt-servierschuessel-bambus-60214343/#content
get creativ local homedepot, Ikea etc. is perfect for looking for volumes U can also use cylindric shape.

i also would suggest to make an own thread for sharing your Build it should be worth it to document it.
Thank you - I will do that. And by the way - great work on your build :D
 
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