Edit: See “Reply number 5”  :-/

I recently completed the BK 20 folded horn speakers using Lii silver 8 drivers. Thought I would share my experience and impressions.

In my quest to find the  “perfect”, pure, minimalist system to counterbalance my “uber high end solid state separates”   I discovered Decware. After some research I ordered the SE84UFO (still on the waiting list). My original intent was to pair it with my JBL 4367’, a local craigslist purchase.

While  researching the SE84 I noticed the OB full range speakers on the Decware site. “Wow. The epitome of minimalist purity.”  

My last experience with open baffle full range drivers was a pair of Kraco whizzer cone drivers (purchased from Kmart during a blue light special) sitting loose in the back window of my car during high school! Needless to say, that left a painful impression. (Fortunately not in the back of my head after a sudden stop!)

Based on the glowing reviews, I decided to dip a toe in the water. The silver 8s were ordered.  

I had a pair of 22 inch Baltic Birch plywood discs left over from a prior project.  A straight cut along the bottom. A quick hole with a circle jig and a “kick stand” on the back with attached with pocket holes. Done. Not A perfect baffle  by any means, but a quick way to get the flavor.

Speakers arrived and were installed.

I needed more bass.

For my purposes additional drivers or subwoofers were not an option.  I decided on the Fostex BK-20 folded horn flat pack.

The kit arrived, but the Lii drivers were ever so slightly too big. Not sure how I let that slip by. The Fostex drivers were on sale, order placed, just a little further down the rabbit hole.

While awaiting their arrival, I assembled the horns. No cutting or measuring with a kit so that was good. The fit and finish of the pieces were flawless. Instructions were vague and difficult to follow. There are a lot of places where you could go wrong in the assembly. Dry fit first. Mark everything, especially make note of where to glue.  One step at a time. Patience.

A down side of folded horns Is the tendency for the mids and highs to emanate from the horns which can affect timing and imagery. (I have experienced none of this. Separation, imaging and dimension are all superb!) To mitigate this I elected to adhere 1/4 inch wool felt to a few key areas internally. I was a little hesitant to do this, as I feared it may alter the tuning length of the horn. I compensated by removing 15 g of poly fill from each enclosure.  I have no test equipment to measure, but it seems to have turned out well.

I highly recommend the use of Elmers wood glue Max. Much longer open time than other white glues.  Aligning the pieces is fiddly and slow. You’ll be grateful for the extra time! You also need way more clamps than they recommend. Can’t have enough.

I am a huge fan of the exposed edge Baltic Birch plywood look.  This look is trending in Uber high-end urban loft $100,000 kitchen installs.  As much as I like the look, I don’t think I would be brave enough to do an entire kitchen in it! But with speakers and furniture it can be a beautiful accent. Not everybody’s cup of tea.

For the finish I went with a hand buffed  hard wax. I used to be afraid of such finishes. I thought they were a mythical beast best left to the most skilled artisans.  Not so. Infinitely easier and more forgiving to apply than polyurethane.

I use a product called Odie’s oil. Highly touted by many experienced wood workers. Contrary to other finishes, with this product,  you absolutely must sand the bare wood to a very very high grit. I did 800 grit. Do not skip intermediate grits! The results are stunning. There is a depth and luster to finish unlike anything you could ever get with polyurethane. The finish is very pleasing to the touch also.

As good as the results are, I found myself still wanting more. It is addictive. I wish I had gone with 1200 grit!  The higher you go in the grits, the easier the sanding is and more rewarding!

As easy as the finish is to apply, as with everything, there is a right and wrong way to do it. Watch the manufacturer’s videos first! Do it.  

Also, I do NOT like the Odies dark or oxi on birch ply.  Slightly orange hue could cause it to be mistaken for pine ply.  Regular oil gives the Birch a more golden blond hue. There are other hard wax oil’s that will leave the color even closer to natural but Odies is my sweet spot.

The Fostex  drivers arrived. Seemed much more substantial and heavier than the Lii’s. Pleased with my choice, they were installed. Time for some listening.

My first impressions were positive. However in certain tracks where the singer “leans into” the high notes, Nora Jones and Allison Krauss, the sound was grating.

Continued listening for a week, to allow for proper break in, only to become more focused on the flaws.  I kept taking sideways glances at the Lii drivers still sitting on the floor in their hastily made open baffles.

I could take it no longer. I had to try the Silver 8s in these cabinets.

Everything back to the garage!  

Did what I should’ve done in the beginning.  

Installed a 1/8th inch rabbet bit on my router. Set the depth to 1/4 inch for a trial run. (Do NOT confuse the two. 1/8th inch bit! ...Depth 1/4”) Cut a hole in some white poster board slightly larger than the driver opening and taped it to the baffle to protect the finish. Once carefully around the opening with the router and the Lii dropped right in. Absolutely perfect fit!  I didn’t bother going any deeper with the rabbet. (Had I done this prior to assembling I may have gone deeper with the rabbet then flipped the board over and removed the rest of the rabbet with a flush cut bit.)

This all sounds much more complicated and difficult than it is. I am not a skilled woodworker. This is the third time in my life using a router. Don’t let enlarging the hole deter you.  Maybe practice on scrap first. But overall, easy peasy.  Like all high speed sharp spinning metal any lack of attention or accident could be devastating. Routers look more innocuous than saws with the smaller barely expose bits. Don’t let that fool you.

I had to plug two of the screw holes for the old drivers and then drill new holes to match the Lii’s. Highly recommend the use of a “centering drill bit”designed for installing door hinges! Easy to find on Amazon.  (May have drill slightly deeper after).

Several hours later back in the room with “new” drivers installed. There was an instant improvement. Norah and Allison were now much smoother in the upper registers.  The bass was a little bit shy. There was so a slight “popping” of “p”s and “ticking” of “t”s. I had noticed this with the Fostex  drivers too. Not unpleasant, but notable. After extended break in, this effect has diminished greatly.

The speakers continue to bloom favoring an extended and gentle break in period. I would stay away from break in sound tracks or loud bass heavy music at first. Slowly ease into it over a week.

Now fully broken in, The bass has bloomed, the smoothness and presentation and air continues to astound me. Absolutely mesmerizing! I am currently running them with a KT88 push pull amp. I can’t wait to hear them with a SE Class A.

For reference, my solid state system consists of Mark Levinson separates and B&W802D3s. Not going to say these sound better.  They sound different in exactly the way I was looking for. Recorded music played back on a hi-fi system is a brilliant illusion. There are many flavors of that illusion.  

I highly recommend this speaker combination.  (I do have an eye on the brand new Lee Silver 10s!)

I’ll try to post some photos. I have taken some pictures, however they just don’t show the finish. In fact, The photos come out almost looking like something that you would see sitting unfinished on the rack the big box store! Not sure why. Trust me, they do not look like that in person!

The "choose file" box works with photos on my computer.  I find that I can only post one per post and they don't show up if I try to preview the post.

If you post photos that are already on the Web, it is a different process.

Thanks Archi. I was trying multiple. Will try again. Little less motivated now. See my prior post.  :-?

OK, not sure why the pictures are so freaking big. Someone enlighten me?

I resize pictures to around 720X540 and they seem to fit in one frame.

Rob, Do you know if there is a larger version of the BK-20 folded horn that might be a better fit for the Silver 10s?

Thanks for getting those pics up!  I see what you mean, but can imagine how good they must look (and sound) in person.

Still frustrated with my photos. This one shows Finish a little better, still not right. Note the reflection. Sorry can’t downsize on my iPhone apparently without another app. You'll have to scroll

Rob7

Good to hear you did not trash your speakers. A builders worst nightmare.

Nice work  

No worries on the picture sizing. All one has to do is hit the file link above the posted picture and a window comes up with the full in frame photo.  

John

Uh, oh!  

The 10s are in. I’m very much enjoying them.  Would be interesting to measure but I don’t have the equipment. Definitely dig lower than the 8s but still not chest thumping. Maybe very slightly less of definition in the lows likely due to cabinet incompatibilities. While they sound superb, these cabinets may not allow them to reach their full potential.  Possible they may do better in a ported bass reflex design as shown on Lii audios website. Seriously wondering if it would not have been better to splurge and go full in on the $3000 speakers with cabinet.  Neither one of the speakers seem outstanding in “busy” rock ‘n’ roll music.  Very very good but not superb.  Most other genres are outstanding.  Of note, this is a secondary system for me. I had  been running it with the highly acclaimed Oppo 205.  I brought my Denafrips DAC into the room from my other system. Absolute world of difference! Incredibly more musical and engaging and less harsh with AND Better detail!  One thing I can say without a doubt, I do not like the more expensive Fostex speakers with these cabinets. I have seen on another website that the cheapest  ones are their best offering. Would be curious to know what that would’ve sounded like. It is a fun ongoing experiment!