Nest Music Theater Part Thirty ~ The Road To 5.1.2 & Building MiniOnken Surrounds 14Mar24-29Mar24

I can't leave good enough alone. Plus, I found a pair of my favored full range 4" Fostex FE108EZs for sale; they were used but I snapped them up and they are in great shape. Getting five channels of gear all on Fostex ESigmas will make the timbre of the entire soundfield more consistent.

I have to decide how to deploy these great drivers AND I want to find the right path to get to an even more immersive 3D surround setup. Dolby Atmos (and indeed many DSP derived modes built into AVRs, esp Yamahas') needs "height" speakers. I have just the spot already plumbed that'll serve for the "height" or "front presence" in this new 3D scheme, and I have the channels, with both derived and discrete signal and power, already in the Yamaha 7810. This next step for the NestMT will require I more normally locate LS/RS speakers to ear level just behind the listening spot and use the suspended speaker spot for "height." The objectives here are to optimally deploy the Fostex FE108EZs while configuring a 5.1.2 system.

5.1.2 Layout... The "new" nomenclature for audio surround speaker systems has the 1st # indicate the number of ear level speakers (usually 2 front mains, 1 center, and 2 surrounds), the 2nd # indicate the number of subwoofers, and the 3rd # indicate the number of "height" or "presence" speakers. For the NestMT: the 5 refers to the FL/FR mains, the CC, and the SL/SR surrounds (once redeployed to ear level). I have one subwoofer; that's the .1. Dolby Atmos, DTS:X, and Yamaha Cinema 3D DSP recommend "height" or "front presence" placement be in line with and above (at basically ceiling level) listening position - that is exactly where I built hangers already and these will be the final .2 (FPL/FPR) in the 5.1.2 designation.

The 5.1.2 Experiment... To assure I was making a subjective improvement, I set up the NestMT in a trial 5.1.2 config using the Blanda 108s as surrounds and converting the suspended Tang Band Tri-Ports to FPL/FPR speakers. I balanced the setup manually by simply using noise on each channel and making volumes @ listener equal from each speaker. This is important as I have a variety of different amps driving the various channels in the NestMT. Then, auditing even derived stuff sounded amazing and modern discrete soundtracks were immersive. Fortunately speaker stands borrowed from COS are the perfect 34" height and I found great surround placement in reasonably correct but protected spots. I will have to figure out how to hide the speaker wire runs however. The Yamaha shows 5.0.2 because it is not responsible for generating the subwoofer signal and really it's just pumping 3.0.2 as I have a separate signalling and amplification system for the mains. Actually I'm even just using the center channel pre-out from the Yamaha and amplifying with the Willsenton EL34 amp.

Surround Cabinet Alternatives... Use of the "new" FE108EZs will be as SL/SR surrounds. The question is in what cabinets they should be hosted:

• The very best enclosures would be brand new back loaded horns (BLHs), Frugal-Horn-Alikes, or TQWT transmission lines built for purpose for this driver (EBP=240) and location... these would also require the most work.
  
• The 2nd best choice in my mind is a 2nd set of Onkens, like the dual center channel I already built; probably an alternative, smaller, and simpler Onken however... this also requires a decent bit of work.
  
• The 3rd idea is a single new center channel cabinet being driven by the Yamaha's CC power (and using the Willsenton amp elsewhere), or not, and redeploying the current Onkens to the SL/SR locations... slightly less work than above but also a greater unknown.
  
• The 4th notion is to replace the Tang Band drivers in the Tri-Ports with the FE108EZs for surrounds and build new FPL/FPR cabinets for the suspended Tang Bands (or FE108NSs)... again slightly less work than the more complex cabinets but also likely less performant. Yet, given pre-existence of Tri-Port cabinets, it's measurable now.
  
• The 5th alternative is to build new Blanda bowls for the FE108EZs... easier to build (I'd stain them black like the rest of the NestMT) but again likely less performant. Yet again, I have Blanda's and can use them to measure performance before going this way.

I chose #2 above without much further analysis and will build some new smaller Onkens with bottom-aligned restricted bass ports. #1 was too much work; #3 held too many unknowns; #4 was the same work, so why; #5 is not right for this driver.

Building The mini Onken... I built a pair of speakers approximating Dave's mFOnken. Super small (<5 liter), super nice homes for the venerable Fostex FE108EZs serving as surrounds. I just needed to find a metric or decimal inches ruler to make things easier from my metric drawing.

I found the ruler for just $10! It is just simpler ~ whomever believed we should stick to inches and ratios was not thinking ahead - decimal inches are OK but metric is even better; it is the 1/8ths and 1/32nds that are far from intuitive or useful for precision work. I found all the 15mm Baltic birch needed to craft a new pair of mini Onkens from prior builds' scraps, so that's nice. Bring out the table saw ~ I made all the cuts in mm measurements as in the drawing. Here are all the raw pieces, the driver hole setup, and the final parts ready for Titebond III.

I glued the front to the top & sides first as they were easiest to align. After a skosh of dry time I added the the bottom with the back in there as dry fit to assure all is square. I did a quick driver dry fit and then clamped it all well for a longer dry time. Clamp city baby.

I removed the back and installed all the port makings and eased an area around the driver hole on the rear of the baffle with a dremel tool.

I made a keen 45° side bevel cut 15mm deep on each front side vertical edge. Harrowing time, but all's good. Small full range Onkens are well served with good dispersion, and this finishing touch on the baffle increases that. But where are the ports you should ask... I wanted the front to be all one piece so I hid them. I then drilled through the baffle with a 12mm bit, chiseled, and filed to expose the port infrastructure hidden behind the front baffle. Clean.

I glued the back in place; access to the innards will be strictly through the driver hole. I sanded the speakers all around, though I will wait for warmer weather to stain them. I installed the binding posts and wired the drivers. I loosely stuffed the entire cabinet and secured the drivers with #8 1" black wood screws and some foam tape for the driver-baffle interface. Rock solid.

I did ask Fostex and Madisound how to interpret the "date code" stamp on the back of the drivers but Fostex would not answer either of us. I'm pretty sure it is a manufacturing date but don't really know.

I tested the new speakers independently at the 2m listening distance... awesome. I did not expect much bass below 100Hz and performance is about as expected. They are actually excellent from 70Hz-14.5KHz, though a little narrowly tuned for bass. These are fabulous in the mid-range and have a decent high end, though rising. They are keen, small, responsive, full range, dynamic speakers. I do see the rising response and sense I perhaps should've left the baffle un-beveled, the step would likely have helped... too late now but I might experiment.

I dropped the Mini Onkens into the the NestMT 5.1.2 surround spots and re-balanced the system... I also "told" the Yamaha that the surrounds were "small" and should be cutoff at 60Hz. The sub handles all the bass smoothly and mostly omni-directionally anyway. I remeasured in the actual listening position... better actually. I also "hid" the speaker wire runs under the baseboards and carpeting for a clean and finished install. I await warmer weather at 10Kft elevation for final finishing.

New & Deleted Connections... I've been able to delete the OREI and get 2 chan PCM from the TV back to the miniDSP. I also tested and approved use of the Sony TV's speaker array as an augmented center channel (at least for now) as the Yamaha drives the pre-outs and the powered outs simultaneously and the TV speakers can be driven externally by an alternative power amp. Cool. The new connection diagram for 5.1.2 and this special CC augmentation is shown below.

Derived and Discrete 5.1.2 Soundfield Impressions... OMG, in just 18 moths I've gone from 2.1, to 3.1, to 5.1, to 5.1.2 and would not go back. All the speakers are custom designed, single driver dynamics, full range, and hand built. Sure I do sometimes mute some of the presence and surround stuff for some music pieces but mostly it is all active; I definitely keep it all active for movie soundtracks. Being immersed  in the 3D soundfield is a trip ~ even the Dolby PLIIx/z derivations from 2 channel PCM are great. The Cinema DSP 3D derivations from Yamaha (various concert halls, etc) can be a bit much for me, though I do trial them occasionally. The 5.1.2 system is most thrilling when a modern Atmos or other 6-10 channel soundtrack is playing, but that's less frequent for me than listening to tunes on the Nest Music Theater. I guess I need to lash in a BluRay player and check out some of the concert footage with discrete multi-channel soundtracks I used to enjoy.