SEAS CNO-25-mkII, built by Trevor, UK

Copyright 2020 © Troels Gravesen

Dear All 
Thank you so much for a wonderful project.  I have just finished my CNO 2.5 speakers and thought that I would send you some pictures and thoughts.

Having built some HI Fi furniture recently I was drawn to your designs by the use of birch plywood as that is something I use a fair bit  After deciding that I could not get a 3 way design under our shutters I settled on the 2.5 and set about a slightly revised cabinet design.  I wanted to get the feeling that the cabinets were carved from a solid block of birch ply so laminated up some boards and decided to go for a 45 degree mitre on the top.  That gave some issues as, with the tweeter so close to the joint, I decided to cut the rebate for the tweeter after glueing up the cabinets.  A risky strategy as if it went wrong I would have to start again.  We were lucky.  I rebated the back layer of the front panel into the side and used some purple heart for the angled trim that I took around the bottom as well.

Everything else went smoothly.  It makes sense to make a jig to rout the internal baffles and I jointed it all using my Festool domino which is good for indexing the corner joints.  Finish is wiped on Epifanes varnish thinned 50/50 and five top coats of their rubbed effect interior varnish over 5 coats of gloss.

I am trying out some home made isolating feet, which I think look good.  They have isolating sticky pads on both sides and so far (i have only finished them today) work well.

Acoustically (where I am not that experienced) I have found, even with the compromised placement in the room, that the bass is well controlled, better than the Dali floor standers they replaced and the stereo image is much wider in the room.  Needless to say they are chalk and cheese from the speakers they replace and I am very happy with them.

I have just had the first play of the remastered Abbey Road LP and Mrs C described the result as very smooth.  But she is just as happy that Spencer the frog can still sit on the speaker without banging his head on the shutters!
Here are some pictures - you will see they sit nicely next to the Wurlitzer...

The system is :
Systemdek II with rewired Rega 250 with Origin structural mod.  
Nagoka MP110
Project valve pre amp
Cyrus 3 with PSX
Project SteamBox and DAC
with best regards



Hi Troels
I sent you a couple of build articles about my CNO-25’s and those concluded with the sentiment that unless we got a bigger house I was banned from building anything more.  
Well, believe it or not, we have moved to Wales and to an 18th Century Dairy farm.  Hence we have a separate “music room” and a much better setting for the CNO’s.
To work with the 25’s I have built a couple of subs along the lines of your Hypex ones using the Seas drivers  and passive radiators taking the speaker level input from the Icon Audio amp.  All sounds so much better with the speakers pulled out from the back wall and given a bit more separation.  I find that helps with my hearing which is biased in some frequencies to one side. I have reverted to spikes on the carpeted floor as opposed to my silicone isolation feet for the main speakers that I had on the hardwood floor.  Next I have to try making a high pass filter to sit between the passive pre amp and power amp.
I am so pleased with the results and when in a year or so’s time I have my barn converted into a workshop I have promised my friend John a pair of CNO-4’s.  Which I cant wait to hear.
Thank you so much for all your efforts and designs and I am sure Mrs C appreciates my re kindled interest in the hobby which seems to have resulted in a depletion of the bank balance and:
Gyrodec turntable
Audiomods tonearm
Hana SL cartridge 
Project valve phono pre amp
NVA passive pre
Icon Audio 60 amp
Project Streambox
Audiolab 6000CDT
and Mrs’s C’s good old Nakamichi Cassette Deck 2 (which still amazes)
all the best to you from the west of Wales


Previous set-up and construction: