OBL-15, built by Max, Denmark
Copyright 2017 © Troels Gravesen

Hi Troels
 
Now I have an update for the OBL-15 after “burn-in” and I have added some construction pictures.
 
I decided to built the speakers using 25 mm black MDF and use wood oil as surface treatment. It was my first time building speakers at this level. First time user of router and circular saw. It was part of the investment to get these power tools and learn to use them. YouTube videos are very handy here. Especially safety regarding circular saws   I used the saw to cut the 5 degree angle for the two supports for the baffle and also the 20 degree angle on the top of the bas/mid baffle. Rest was pre-cut in rectangular size done by one of the big DIY stores.
 
Speakers was bulit over a period of approx. 3 months. It was on the limit what was practical in a 3 room appartment     ......happy I had a balcony for the most dusty work.
Think between 150 – 200 hours was used for the construction and “thinking”. I am very happy for the many answers I got from you regarding constuction details and use of router etc.
 
For the crossover I decided to upgrade to full Superior Z-caps for the mid and Alumen Z-cap for the tweeter. Then I also decided to go with all smooth foil for the ELKO’s. These bigger capacitors required some “thinking” when the crossover where built. I used TEC7 glue for mouting the crossover components. Seems to stick on everything. It just need time to dry which can take 12 hours or more depending on the thickness of the layer of glue. When dry it is like hard rubber.
 
The sound of the speakers:
My system consist of a NAD M3 amp, Bluesound node, Cambridge dacmagic plus, Tidal Hifi agreement for streaming. Latest addition is a stepped attenuator. I don’t use the M3 pre-amp but go directly from the DAC in fixed output mode into the attenuator to the main amp of the M3. This gives the best possible sound in my system. Much better than using the M3 pre-amp. It takes some of the dynamics if the M3 pre-amp is used.
 
OBL-15 was sounding very good when first used but a little “thin” in the bass response. In fact my SBA NAC-61 speakers (an original “TG”) had a more solid bass response at this stage. After burn-in (several hours with 10 Hz at large amplitudes) the bass response is now on par with NAC-61 at low to normal levels but really has some dynamics when pushed a little bit. NAC-61 has its limitation here. I made an A/B test and I found out how good the NAC-61 really is. It is a shame not so many has built them. That said the OBL-15 has a huge dynamic overhead and I think also a bit more detailed. Bass response is very controlled and dry and has the same “sound” all the way down where a ported system change a bit when the port takes over and can trigger some nasty room nodes. The OBL-15 does not do that in my room. This was part of the reason to built them. I am very happy with the speakers and may update later with SE/SET tube monoblocks.  Orchestral music with its dynamics and complex sounds is perfect match for the OBL-15. Also the sound of a cymbal in jazz music is impressing. It sounds very real. Especially this sound can sound very “funny” on not so well designed speakers. Think my neighbors has found out I have got new speakers. They are probably not as happy as I am
 
 
Regards
Max