Building Blanda Salad Bowl Speakers ~ Nothing Is Parallel In The Googly Eyes 21Dec23-26Dec23

I've enjoyed designing and building custom speakers for the NestMT and have some additional "needs" I will fill with a new pair of DRC DIY speakers. They'll most likely adorn my study desk at the Nest so need to be small and great for close field listening. I've read about building spherical cabinets (few standing wave issues and significantly reduced diffraction interference) and have heard commercial (B&O) designs employing them as well. In fact, some DIY forums suggested that a build based on Ikea Blanda Matt bamboo bowls are effective and inexpensive! I bought four 8" bowls and gave it a try. In just 4 hrs I was enjoying HiFi sound with surprisingly good bass thumps.

I was impressed prior with the sound and performance of Tang Band full range 6.5" drivers I'd tried in the NestMT BLHs when I was settling on drivers for them. I dove hard on their line of 4" full range drivers for the Blandas and settled on a brand new and fairly wild design, the W4-2356. The design uses a patented offset voice coil and custom polymer cone which supposedly avoids concentric cone modalities and considerably reduces diffraction issues in any cabinet (though that will already be a small effect in a sphere with no flat front baffle). The driver is not cheap as it is new and uses a neodymium magnet; it is less efficient (85 dB/w) than I'm used to using, but early lab tests were very good, so I gave it a try.

Design choices beyond driver selection were very constrained given the cabinet is basically set from the get go... it's whatever two 8" salad bowls glued together will yield. That's 3.6 liters before adding the driver to a flat cut opening and 2.7 liters after removing that section. I sketched stuff and used modelers to help me choose bass reflex port dimensions given Theil/small parameters and the cabinet. The sealed cabinet variant performance would not have been good from initial modeling, so I went right to the ported style. I saw some Onken-like port mid-sections from other DIY builders but decided simpler & faster is warranted here.

Once supply chains caught up with my ideas, my first fabrication step was the most challenging part of the project. That was to cut a hole for the driver in the "front" bowl... the cuts needed to be perfectly sized and reveal a flat lip to secure the driver well while looking smooth to the sphere. The pro alternative was to use CO Lumber's power planer to repeatedly and carefully plane down sections to the right size from the sphere. Nah... I went full hand woodworker. Drawing the cut lines was done using a compass and I used a hacksaw to start the cut, then a simple fine toothed Japanese pull saw (flexible and thin) and took my time freehand to make the driver hole. The driver dry fit looked fine though the first bowl cut was a little large and I adjusted on the 2nd... gaskets will seal around the drivers to the bowls.

I then used a hole saw to cut a hole in the "back" for my ~ 1" x 4" flared port. I also drilled for the banana plugs. The port was a good friction fit but I glued it in place anyway. It's not a great location for the port directly behind the driver but the off-axis nature of this particular driver added confidence it'd be fine. I like it there aesthetically to remove the bowls' original manufacturing indentations & markings. Once the holes were completed I sanded the lips of the bowls to allow better acceptance of the glue. We don't want the spheres to roll around so I added 2 ball feet (drawer pulls) to each cabinet while the 3rd point of rest on the surface is the cabinet itself, which was dotted with a silicon foot. I then glued and clamped the bowls together into cabinets.

Once dried, I stuffed 6 oz of poly fiber fill into the interior and wired up the drivers. I laid a sealing gasket around the drivers and secured them to the "fronts" carefully with black wood screws.  All the hardware is silver/nickel to match the drivers' accents. Matt called them Googly Eyes.

I don't expect much great from a measurement standpoint ~ these aren't the best cabinets ever conceived, and they are tiny. However I was shocked and pleased at the listening results. The drivers are smoother at the mid-high end than other 4" sounding close-fields I've heard. The bass is just decent of course, but present at the rear tuned port as hoped ~ they could still use subwoofer support as you can imagine. I listened for a couple hours or so in the COS family room and lower level setups using just the Blandas and they are very nice... hell yeah, I can listen close or fill an entire room.

I measured the Googly Eyes on-axis close (green), off-axis close (brown), behind to check bass port (blue), and "far @ ~3m (purple). On axis close performance is great and confirms my sense about upper-mids. Off axis attenuates this some as expected. The bass is there as measured on the rear tuned port (blue) ~ and is fine in front when positioned close to a rear wall. Basically the Googly Eyes are fit for purpose in close field use and work surprisingly well in normal listening, and they measure out this way. Maybe I should damp the cabinets a bit more for even smoother performance.

I decommissioned the NOnkens and so tried the Fostex FE108NS drivers in the Blanda Bowls; the sizes and hole patterns were equivalent. I made no other changes other than the drivers. I listened and measured. Just as I noticed in the NOnkens, the New Sols are very nice near field drivers. And in fact, they sound great in the Blandas, with even nicer near and far sounds than with the wild Tang Bands, and they are more efficient. The measurements below were conducted exactly as prior with the Googly Eyes with one graph showing nearfield sweeps and the other showing sweeps captured from 10 ft. The Googly Eyes are better at some bass but the Blanda 108s are better at mids & highs... listening to tunes sounds like this too. I'm leaving the FE108NS drivers in the bowl cabinets for now but I will definitely need a subwoofer. I am hoping I can get a viable sub design from an 11" diameter Blanda bowl.

I even took the Blanda 108s for a spin in the NestMT CC spot ~ awesome. I still believe they'll be most unique in a Blanda 2.1 configuration. Loaded with the FE108NSs, the Blandas don't look as cool as the Googly Eyes with silver accents (given hardware I chose) but ultimately I think I'll make a different cabinet for the Tang Bands, but it's close.

And finally the Blanda 108s sit atop my desk, for which they were built. The bamboo looks cool on my bamboo desktop. Sometime ya just don't wanna wear headphones.

Update 27Jan24... I was concerned I might strike the drivers with something and hurt them, so wanted to protect them somehow. I bought some cheap Chinese (metal) grill covers and took them out of their frames and then just used neodymium magnets to secure the grills only to the drivers. Worked great.

December Music Appreciation ~ Grass & Pop 'History' Highlights 18Dec23

December music appreciation highlights from me do not include holiday songs, despite Billie  Eilish's appearance on SNL where she sang "Merry Little Christmas." Let's go...

• Olivia Rodrigo @ Tiny Desk 11Dec23 ~ Cool versions for NPR; very strong writer with a keen voice and great backing players. Though, I don't like reference to a "2nd string loser not worth mentioning;" whoever he is... he did get a song written about him.
  
• Abby Holliday in Studio Live "Slackjaw" 08Dec23 ~ Still releasing smoking guns; love it.
• Caitlin Canter with Will Seeders @ Burnham Hall, VT "Come By The Highway Home" 08Nov23 ~ Many Canter performances are spectacular... thanks Less Than Face.
  
• Steep Canyon Rangers @ NC Museum of Art "Fare Thee Well, Carolina Gals" 18Aug23 ~ Token male vocals for this month? Nah, but so good; doesn't even feature Steve Martin.
  
• Brothers Comatose & Rozzi "Let's Get It On" 09Aug23 ~ Great blues voice Rozzi. The Brothers collaborate so well.
• Bella White @ Green Mtn Bluegrass & Roots "The Way I Oughta Go" 25May23 ~ I am a big believer.
• Hawktail @ Sanders Theater "Updraft" 17Mar23 ~ Epic version, even for this awesome band, acoustic quartet of fiddler Brittany Haas, bassist Paul Kowert, guitarist Jordan Tice, and (Colorado) mandolinist Dominick Leslie. All original works from great musicians with many other solo and team projects like The Punch Brothers & Golden Highway. Less Than Face never falls short.
  
• Chris Thile & The Punch Brothers @ Orpheum/Boston covering Lightfoot/Rice "The Wreck Of The Edmund Fitzgerald" 17Mar22 ~ Throwback 'cause it's a good cover of a classic with cool musicians.
  
• AJ Lee & Tuttle Family @ Foothill Community Concert Series "Here In California" 12Mar17 ~ Nice get together from some formative grassers from NorCal.

5.1 Channel Signaling And HDMI Audio Extraction 18Nov23-12Dec23

Discrete 5.1 Channel Audio Extraction Trials: Excruciating... In the NestMT I want to use not only Dolby center channel & L/R surround signaling derived from stereo PCM via Dolby PLIIx, but also get discrete LPCM or 5.1 Dolby Digital to the speakers. Of my 3 main audio sources: Roku, JRiver, and vinyl, only Roku spits out true Dolby Digital; I turn the other streams into 2 ch PCM. Were I to use an AppleTV box, they prefer 6 channel LPCM. I want to extract the full unadulterated 5.1 digital signal directly from the Roku Ultra HDMI out while not disturbing the 4K/120Hz - UHD/HDR on HDMI bound for the TV. Almost all "extractors" only do 4K @ 60Hz and many just feign doing true DD 5.1 or DTS on the SPDIF optical out port, they just copy some channels to others. My TV is a capable 4K/120Hz/HDR monitor, as is the Roku Ultra, and I now access content at these levels often too ~ de-resolving or de-ranging is not in the cards (see ELSEWHERE on the blog to understand HD, UHD, and most importantly HDR). UHD/HDR pass through and full 5.1 digital audio extraction is an under-served need in the audiophile realm.

Rounds 1 & 2... I did find two boxes with the needed specs: the EZCOO AudioExtractor and the OREI 8K; both claimed 48Gbps (HDMI 2.1) bandwidth, real Dolby Digital 5.1 audio extraction, and the 4K/120Hz/HDR video pass through I sought. I bought some newer HDMI 2.1 cables to assure needed quality and bandwidth. Testing of the EZCOO failed badly and I returned it same day ~ it couldn't even pass through the HDMI properly. Fortunately testing of the OREI showed it capable of passing 4K/HDR @ 120Hz. I didn't test the audio extraction till arriving in Summit. I am out of luck for discrete DD 5.1 for the time being ~ while it did the video well, the only audio I could get from the OREI was stereo PCM, and I tried many HDMI sources. I returned it too. I went back to a derived center channel using PLIIx in the Dolby box.

Round 3... I still can't find an extractor with HDMI 2.1 support, sufficient fidelity, and operation which meets spec. So, I decoupled the HDMI pass thru task from the audio extraction task ~ I acquired a well-regarded high end HDMI splitter from HD Fury named Arcana 2. It does all the ARC/eARC stuff as well as even HDMI 2.1 @ 8K (for me 4K @ 144Hz with HDR is great). This splitter allows two different HDMI resolutions to be used while many splitters just drop all HDMI outs to the lesser spec connection. It's from the UK and more expensive but I tested it and HDMI passing was good. Plus it is super flexible in locking in the best modes on installation. However, while I got some stuff to work I could not get full 6 channel (5.1) audio from either HDMI port on the Arcana box ~ the UI even indicated it wasn't happening. Further, while a full HDMI pass through occurred, the TV would flash on occasion when labels and tickers appeared on the screen. Sometimes the Arcana wouldn't even re-sync to full UHD/HDR after the banners had passed. Lame; it was returned too.

Round 4... Undeterred but eyes open to the dearth of gear capable of meeting my specs, I continue to pursue the 2 separated tasks (HDMI pass through & audio extraction) idea to get discrete audio. I bought a gofanco Prophecy HDMI splitter. I'd split the HDMI from the Roku Ultra and send one out to the TV and the other out to a simpler extractor that I already have for extracting audio for measurements, and which I know works. An issue with my design in general is that I do still need regular 2 ch PCM for the main L&R speakers as the miniDSP DDRC22D accepts only that. Somehow from the Roku Ultra HDMI signal I need one optical pipe to carry 2 ch PCM for the mains and one optical pipe to carry DD 5.1 (or LPCM 6) for the center and surrounds. So, I will get 5.1 ch on optical from the extractor and 2 ch on optical from the TV. Well shit, the gofanco splitter didn't work either ~ HDMI pass through never really synchronized from Ultra to TV. The screen often went black and this was independent of using multiple sources and settings and even displays. I'm SOL again.

Round 5 - Final... Well enough of this BS, I decided to just acquire a newish, but cheapish/low power, AVR to do some of this, a Denon S570B. I'll use an alternative OREI splitter/extractor (the 102A) to get 5.1 DD on optical to the Dolby box for the center channel and 2 ch PCM on optical for the main L/R channels (minDSP) via a 2nd extractor on the 2nd HDMI out. The Denon also gets digital COAX back in from the Felston for Phono/ADC path and the JRiver streamer path. Testing in COS confirmed most operations; the new OREI S102 showed the most stable UHD/HDR pass through of the five gadgets I tested and it reliably extracted DD 5.1 audio for its optical port, when that existed in the source material from the Roku, and 2 ch PCM otherwise.

After pulling down the NOnkens I also gave the Denon AVR to Matt; I'll find a more inline scheme to get surround signalling from my existing Dolby DP564, but I may need to use it's AES3ID pro digital out ports and some interface conversion from that to SPDI/F for use with consumer DACs.

Hanging & Driving The NOnken Surrounds 09Dec23

Hanging The NOnken Surrounds... In deploying the NOnkens to the left & right surrounds locations I needed secure permanent installation spots that were out of the way of walking about and very strong to carry the weight. I chose to hang them from the wall above heads and point them at the seating properly. I think even Bro Brown can walk under them. Note that the full NestMT image is distorted and the NOnkens appear strange due the focal length... the direct head on images of the hanging NOnkens shown later are more representative of the install.

The NOnkens are 35 pounds a piece and in investigating mounting hardware I was immediately drawn to the pro PA stuff enabling suspension via a 35mm cup/pipe system ~ these had 5X or more the carrying capacity of other mounts and held up to 100# each. It's a widely used standard mounting system in theaters, stages, and mobile kits and most PA speakers these days have the cup built into the base. Enter the BiGalleons, adjustable powder coated steel mounts affixed to the wall via 6 substantial anchor bolts (which get covered up nicely). Each surround was outfitted on the back with an external mounting fixture I fabricated... I used 1 1/4" conduit (which had the proper ID to mate to the BiGalleons' "pin"), a block of leftover Baltic birch, U bracket holders lined with old bike tube rubber and a tapping screw (that goes into the hole to register the speaker to the "pin"). I bought and returned manufactured external mounts as they didn't allow the desired optimal mounting in the room ~ would've lowered the speaker and limited it's angling. My fixture screws into the back of the DRC NOnken and I can angle appropriately and install the surround almost right at the ceiling level. My mount will be proud from the wall a bit more but that's fine. I checked my angles and my working idea first, to assure all would fit OK, sure it was in ink :); 𝛼 = 51.3° and β = 54.5°. Installation went fine but I did needed quite a bit more 12 gauge oxygen-free zip cord speaker wire (I eschew all those expensive audiophile low loss cables for my own builds with banana plugs); 12 gauge is pretty big but this is a long run.

Surround Signaling... I purchased a Denon S570B on Cyber Monday for a good price - Denon should do audio well and they claim full 8K/UHD support, if I need that. It allows me to get surround decodes (DD 5.1 or D PLIIx) and power (since I returned the Schiit amp) for the surrounds. Why do I need decodes you might ask. Unfortunately, during comprehensive testing of the used Dolby DP564 I discovered that one of it's surround channel analog outputs doesn't work. Investigations online indicate that this 20 year old gear does tend to have this analog out failure mode ultimately. Therefore, the Denon decoder will be used for the surrounds ~ same algorithms after all; fortunately it has it's own time delay capability so I'll be able to dial that in cleanly for the surrounds. Initial testing of the Denon and new surrounds went well... I'm delivering 2 ch PCM or 5.1 DD to the S570B via COAX Spdif (big orange) from the Felston. Optical from an HDMI audio extractor would work too.

The NOnkens  are a decent size and hefty but the install went fairly smoothly into their spot. I still need to finish the NOnkens and hide the cabling but else I am online with 5.1.

Initial NestMT 5.1 Impressions... Holy soundfield! While I was wary of the final outcome, the new NOnken surrounds make the NestMT expansive; my mind is blown. The 6 high performance full range Fostex drivers in my custom back loaded horn and bass reflex Onken cabinets deliver the goods beyond reason ~ sure, they're augmented by Viawave/hi and Hsu/lo and even some signal processing but who cares if it sounds this cool. The recent expansion from 3.1 to 5.1 is ear-opening and unexpectedly good. The derived and direct surround sound from the Denon box is fine and clean. Listening is a blast however it is late so I will leave remeasuring and resetting delays for an update.

Measuring The NestMT 5.1... I rebuilt EQ in Dirac for the L/R mains (with Veriwave tweeter & Hsu sub) just for good measure ~ not much change. I then measured the center channel and surrounds and checked the impulse measurements to assure the delay is right between them. They are the about the same distance to my ears and fortunately not much tweaking is required. There is not much processing delay difference in the AVR for surrounds and in the DP564 for centers; what is needed can be done in the Denon AVR. I also remeasured the processing delays between mains and center/surrounds, which are handled in the Felston, for each source; they are again about the same as set prior for just the center. I won't bore you with the delay measurement graphs and settings... I'm just gonna provide the composite sweeps and their average. The "mains" graph includes the sub & supertweeter with the new Dirac EQ. The centers and the surrounds have no EQ applied and the surrounds are being measured off-axis of the mic. The new NestMT 5.1 system is amazing but I do note the 5dB baffle step shout from the surrounds 1KHz-4KHz and may want to address that with specific EQ.

The BOnken come NOnken saga made my move to 5.1 channels in the NestMT a tough road. The project to even hang the NOnkens, as described here, was very challenging, with its own hiccups along the path. It is worth it but I am glad it is almost over.

Update 31Dec24... I'm dissatisfied enough with the surround signaling (it was thin and odd derived from PCM 2 channel) AND the performance of the NOnken surrounds (described prior) that I have removed and decommissioned the speakers and have redeployed the drivers elsewhere for now. I will design something better from scratch and will seek better 5.1 signaling somehow. Matt will get the AVR and the surround hangers are very solid and will remain on the ready for reuse.

Building The DRC NOnken Surrounds 18Nov23-07Dec23

I conceived a scheme to "save the BOnken cabinet" by designing a new pair of surrounds derived from the huge prior speaker cabinet. I chose Fostex FE108NS full range 4" drivers similar to those in the DRC Onkens for these new surrounds after modeling and "simulating" possible derivative Onken cabinets and drivers. The FE108NS is the latest "new SOL (NS)" driver from Fostex; it is targeted for a back loaded horn cabinet but I can't handle that size. And I've seen the numbers/performance in a simple open baffle and these can be used in other designs. So I did...

The original SOL drivers were named for "the Sun beloved timelessly and close to our heart." These seem perfect for my need in a close setting. The drivers will do especially well in the mid-range in a wide baffle design (which I can derive from the existing BOnken cabinet. The new speakers will be new Onkens, so NOnkens.

I guess this project is "design while you saw." I peeled the BOnken felt out, cut 6" of depth out of the cabinet, and glued it back together at a depth of just 14" (vs the BOnken 20"). This was painful and it created a ton of sawdust but at least it worked. Don't try this at home kids ~ hoisting the hefty BOnken around for serious cuts was cumbersome. I only did it to employ the cabinet investment I'd already made. The reassembly along the depth is a simple butt joint but the 45mm of material along each side makes the butt sufficient with just glue, especially since eventually tops & bottoms will secure everything well. What the heck can I do with the nice Onken channel port pieces remaining?

After the assembly dried I cut it in half in the other direction. Unfortunately my table saw was shy of allowing the 17" cross cut and I had to start with a handheld Skilsaw and then tidy things up on the table saw. Yeah that 45mm of material did bend the circular saw blade at temp. Ugly, tons of sawdust, and time consuming but ultimately effective... the cut was completed as hoped. I used a jigsaw to cut new holes in each face for the new drivers. I added small front "baffle" pieces to cover up the hole where the old driver had been and even a corner to assure closure. I then reinstalled felt and new binding posts with wiring in each of the two new cabinets. I cut 4 new top/bottom pieces and secured all of them to the ends of the two speakers with screws, as I had done with the failed BOnken. Finally I installed the drivers. The NOnkens were born about 5:30pm MDT 07Dec23!

With all but finishing work to be done I measured the NOnkens. They sound "ok" and are appropriately sized for dual center channel use or surround use in the Nest Music Theater. See the not so flat sound pressure level (SPL) frequency sweep under test. While I don't like the drops at 150Hz & 900Hz, I am not going to equalize them ~ they are plenty clean full range speakers for LS/RS. A big issue though is the 1KHz-4KHz shout which is probably from baffle step issues and the poor cabinet tuning. I may yet try to physically tame that loud in the upper mids ~ some inner surfaces were undamped and my screw top assembly will allow me access for some tweaks. I am prepared to bevel the port openings but am unsure I need to do that ~ they should be ok as surrounds. Subjectively the 108NS is every bit as strong for near field listening as the 108E∑... I dropped the NOnkens in the center channel spot tonight and the front soundfield was great... I also listened to them several feet high as surrounds, just to make sure.

Finishing the NOnkens will be done in the same way as with my other NestMT speakers... sanding, true black stain, and multiple coats of poly. But that will wait for spring weather. They look odd but sound OK being crafted as a 2nd thought from a failed center channel BOnken project. I need to get the signaling right now for 5.1 channels, and hang the surrounds. And I need to likely tune the NOnkens more with EQ, damping, or other 'cause they are not great. There's a chance I will just retire the NOnken cabinets, reuse the drivers, and do something else to get to 5.1 ~ Onkens built on this circuitous route just don't have the finely tuned resistive ports that ground up Onken builds should ~ and the measurements show this both on baffle step issues and on port tuning.