Baffle Diffraction Step Loss In My miniOnkens ~ Dealing With It 30Apr24

Speakers and drivers are normally modeled in 2pi space; this means they are expected to be projecting forward in a hemisphere. I model this way. When measuring and listening to the NestMT miniOnkens (currently deployed as surrounds) in free space, I see and hear a significant rising sound pressure level (SPL) with frequency. The measurement is a smidge flatter when the speakers are directly against the wall (SPL graph not shown). Speaker designers want a flat response over frequencies and humans even prefer a declining SPL with frequency (that's why I always look for a system matching my personal "house curve"). What is going on here? It is called baffle diffraction step (BDS) loss.

What Is Baffle Diffraction Step (BDS) Loss?... The acoustical load that the front baffle of a speaker presents is different for low frequencies than high frequencies. Speakers tend to project mid-high frequencies directly forward in a 2 pi hemisphere while lower frequencies project in a full sphere (4 pi). This difference results in a ~6dB loss in presented sound pressure level at the lower frequencies. The step for this occurs at the frequency whose wavelength is about 8X the width of the baffle. In multi-driver speakers this is often handled in the crossover circuit by attenuating the tweeter.

Reviewing The DRC miniOnkens... My miniOnken's baffle is beveled (which helps with diffusion and ameliorates ripples in SPL) and presents about a 4.15" width. To find the frequency of the expected baffle diffraction step one takes 1/8 the speed of sound and divides by the width of the baffle: (1/8 * 13560 in/sec)/4.15in = 1099Hz. Does the expectation match the observed measurement? Yes ~ exactly!

Dealing With Baffle Diffraction Step (BDS) Loss... One can of course "do nothing." Purely acoustically one can place speakers with this attribute directly against a wall, which will likely improve low freq SPL by bringing the much larger/wider baffle load into play which will make the low frequencies present more forward in a hemisphere. Depending on the situation: sometimes you can, sometimes you can't. Little else can be done to the cabinet/speaker itself acoustically. However, one can build a simple passive circuit which will reduce the high frequencies by the 6dB and make the overall SPL flatter. The implication is though, that doing so will reduce the efficiency of the speakers (less so if the correction is at line level); either is something I rue as I tend to seek high efficiency drivers/speakers and drive them with lower power amplifiers. A guy's gotta try though. Dr John Murphy showed an accepted approach for building a passive circuit for Loudspeaker Diffraction Loss and Compensation... I won't delve into his math or derivations further, but jump to accepted correction circuits.

Correcting BDS Loss In The DRC miniOnkens... I will not typically have access to adding a simple RC circuit to the line level so will need to use an RL circuit directly on the speaker level signals (grrr... loss, just to heat). This is just what crossovers and the like, which are internal to many speakers do, so it's an accepted correction scheme. I'll do calculations here based on the full 6dB attenuation of the high end (even though in my room the attenuation might be less due to the wall). The 6dB assumption is right on for free space speaker placement.

R2 is the speaker system resistance (the FE108E∑ is 6.8Ω and the miniOnken system is nominally 7Ω, say) and we'll make R1=R2=R. Murphy derived the equation for inductance given the width (W in meters) of the baffle and nominal system resistance R: L1 = W * R / 1.021 = 0.1054 * 7 / 1.021 = .723mH = 723µH. This correction assumes 3dB down at the step frequency and 6dB at the high end. Well, this is a fairly expensive and large inductor, and equally rare resistor... bummer. I imagine I will ultimately make a box with adjustable components to allow me to investigate passive circuit correction on a variety of speakers but here are the right components for a 6dB passive circuit for the miniOnkens.

BDS Correction Experiments Using A Digital XOver... Whoa, here's an idea. I have a miniDSP 2x4HD and can experiment with various high freq BDS correction attenuation levels as well as step freq settings and compare results! I can even measure in free space and in the "closer to the wall" listening position. This won't be a permanent install of the 2x4HD as I don't like the processing delay introduced by it. It will however give me an solid indication of what attenuation and knee I should be targeting in any correction circuit. Glad I haven't sold the 2x4HD. I built a simple 6dB high freq attenuation in the 2x4HD with the knee at 1.1KHz as my original measurements above suggested. 

Voila, using my measurement mic and REW I swept the speakers corrected and uncorrected/bypassed and can see the appropriateness of a BDS correction for the miniOnkens, as doing so has the speakers right on my desired house curve. Somewhat surprising to me is that measuring the miniOnkens against the wall did NOT substantially change the rising SPL phenomenon.

These experiments have shown me that the passive circuit described above, and even the values calculated for the resistor and inductor, would have the desired effect to correct the miniOnken's BDS behaviors.

Measuring The Corrected miniOnkens & Implications Of Compensating For BDS Loss... Uh, you will have to wait for an update to this entry where I disclose the final results of this work... it is just system design and experiments thus far. I'd like to see what effect the circuit would have on efficiency.

Solid Day Again On The S Platte ~ Cold & Wind Had Folks Leave Early 29Apr24

With the PT still flowing heavy, I made another outing to 11 Mile Canyon today. Fishing was good. Flows are consistently 130cfs and there were 28 cars up to the last bridge area. It was cold and windy so despite the car count I had my favored sections mostly available. But my toes and fingers were pretty cold, especially "early." I didn't arrive till 10:45am. While it started slow in the cold waters from snowmelt. I again caught a passel of fish, including one near pure cutthroat, a couple of browns, and many healthy 16"-18" cutbows, but no 20"ers. The play remains maroon/brown midges in the morning and then a modest BWO hatch occurred at ~1:30pm. I went to two mayflies below the Perdigon (which also worked) before that and caught bigger fish then. Unlike my last outing, the egg did nothing today. The deadliest tie was my Destiny's Child. Fun with the Rodfather Diamond Blaze ~ it is the favored among my 4s (plus it is the one rigged and in the carrier). Here are the better or unexpected fish.

 

The #1 bug in April this year, for me, on the SPlatte, by a wide margin, has been Coffin's maroon Pop Top. Recipe: #22 TMC 2288H, red & black thread body covered in Sally Hansen's, UV2 rust thorax, and UV cinnamon ice wings (the pop top). I drop this behind Juan's money midge, which also does some scoring, but the emerger trailer has scored more. We are getting into mayflies now finally, and I also expect more green midges will soon appear and I'll flip mornings to my Blue Oyster Cult larva midge trailed by the olive Pop Top. Anyway...

Denver Stuff On A Weathery WE ~ Old Friends And When Kids Rule 27Apr24-28Apr24

It was pretty nasty in the sky all weekend. We were invited to Comet Brews in Littleton for a unique beer & cheese pairing. We met up with our great friends T&L at their kid's brewery in downtown L. Yeah, MeMaw had some kid duties on behalf of the hosting Brian & Lisa team. We had a blast eating good cheeses described by Allende and hearing Brian's choices of beer for pairing with them. I think we liked the cheddar with porter best, and as mated with Brian's Wilkenstein dark. We dined after in town center at Smokin' Fins with T&L... our regular date was actually missed one month in March but we are back on schedule.

The beers were low abv for the most part but enjoyed heartily and delicious. Of course our buddy TAW paired with funky flavored seltzers. Brian is a busy man as he's a full time code jock for AMZ while brewmaster for Comet, and dad to a brood. Awesome. We "toured" his new installations with mechE supreme dad assisting ~ a 20' auger from roaster to grist install above a kettle... weirdest suspension imaginable. So good to be with the Wilkes again.

We headed home in a bit of rain and headed back out of Peregrine in the AM with a bit of snow, NP. This day we hit Morrison, CO in the shadow of Red Rock Amp. We visited the home of our good friends Craig & Cyndi for a baby shower of their likely 5th grandchild. While it's Z&MJ who outperform, we were celebrating Brock & Anna's 1st. I had not seen them in years and they just returned to CO in BV... good visit. But while grandma & grandpa (and the greats) were about the new pro-creation we were there for the recent and their parents. Voz's new digs in Morrison are awesome, appointed, positioned, and decorated perfectly. Yeah, that is the Denver skyline behind us. So good to hang with the couples and their families.

Of course we closed out the WE a@ Torchy's near Matt, with Matt. Always great to see him.

Stellar Day In 11 Mile With Yoho 24Apr24

Jim & I made a mostly last minute fly fishing trip to the S Platte in 11 Mile Canyon. The PT is still raging 700cfs so we altered out target. It was a gorgeous day, though the sun brought the pollen out heavily. We arrived pretty early and were fishing by 9am but the water was cold and fishing was slow till 10:30am or so. Too, despite early arrival, there were already 25 cars in the canyon and key spots up top were already occupied. From 11am to 3pm, when we finally quit, fishing was awesome. We even saw a mayfly hatch about 2pm and we caught our 1st fish of the year on mayflies in the canyon and Jim caught risers on a dry. Else the best bugs for me were the cinnamon colored midges and the bigger slabs hit the milking salmon egg I use as attractor. I even caught a couple on the oil can Perdigon in the faster water in the PM. Whoa what a great day out there. I haven't recently counted so closely but at the end the day I'd landed 20 nice cutbows mostly 16"-18" with the largest just 19", but all were very healthy, including some nice colorful slabs. The Rodfather Diamond Blaze served mightily. No brownies though. Plenty of activity on the spawning redds... I observed one guy looting the redds and while I thought to chastise, I didn't.

We stopped at Red Leg to commemorate, dine, and enjoy the vibe there. The Lobstah Shack dinner was very good. Thanks Jim.

April Music Appreciation ~ Tracking Our Concert Schedule 22Apr24

The concert season is upon us so prep is important. One's gotta absorb the vibe & lyrics before the shows. Else, it seems, one can bob unknowingly to the tune which is intended to tune you out. Anyway... Kala & I have a full season ahead, for which I am grateful my best has agreed. Awesome. So, with that in mind, and in that event order, I bring you April MA; just prep...

• 11Jun24 Margo Cilker @ Lulu’s Downtown - Steelhead Trout 23Feb24
  
• 21Jun24 Old Crow Medicine Show And Molly Tuttle & Golden Highway @ Dillon Amp - [cover] White Rabbit 07Apr23
  
• 12Jul24 Jason Isbell & 400 Unit @ Dillon Amp - King Of Oklahoma 20Nov23 ~ as much as I hoped Amanda would show, they divorced so it's unlikely; rock on Jason
  
• 21Jul24 Steep Canyon Rangers @ Breck Riverwalk Center - Various From Fort Collins 11Aug23
  
• 22Jul24 Norah Jones & Hurray For The Riff Rafa @ Ford Amp. Vail - NJ: Staring @ The Wall 21Feb24 and HfRR: Alibi 13Apr24 
• 03Aug24 Bluegrass & Beer Festival @ Keystone - Liver Down The River 13Mar23
  
• 10Aug24 Rocky Mtn Folks Festival (Bonny Light Horsemen, Margo Cilker, more) @ Planet Bluegrass, Lyons -Various From BLH Supergroup 22Jul22
• 19Oct24 Lawrence @ Fillmore - Casualty 03Aug23
  
• 01Nov24-02Nov24 Moab Folk Festival - Ft: Mighty Poplar | I Was A Cowboy 16May23
  

How Do You Check The Flows? ~ I Use DWR 22Apr24

I was a beta tester for Colorado Dept of Natural Resources (Dept of Water Resources) when they altered the database and services behind their water flow sensors site. Now you build your own custom set of gauges and save them in your profile on the site. You get your own personal credentials for free to do this ~ then use My Stations and Tools there to build the list and even custom graphs (as I did below to combine all my relevant Arkansas gauges on one graph). Here is what I use as my dashboard... then if I want to see more detail I can click enlarge a thumbnail and get the full screen version as shown below. I am a visual guy so I always use the graphs but if you like raw data for the day, that's available too. The site is HERE.

The most challenging part is interpreting the shorthand gauge names. Like knowing that MFBLKMCO is Middle Fork of South Platte Below Montgomery Rez Near Alma; whew.

All said this is a great data service from Colorado. And, there are plenty more in the US like this, such as for demographic and census data, for housing data, for weather data, etc. Yet, it is insufficient, as unless you personally know the water control engineers, you will not know what's gonna happen tomorrow.

Wierdest Day On The Ark ~ A Tripple The Hard Way 21Apr24

Yeah, I got nabbed in Canon City for speeding... it was almost a sheepish stop at just 10 over and he even said, "have a better day." Grrr. Super foggy coming out of COS and even on 115 toward the Arkansas River Valley, but then it cleared OK. Jim & I met GL at Pinnacle Rock for a run at the caddis hatch, which I'd heard had entered lower Big Horn Sheep Canyon. Well, it had... even though Jim & I only saw the leftovers on the banks' brush from the day prior, as we left early, Greg said the canyon was full of 'em by the end of the day on the drive home. Jim & I both used Rodfather 4 weight weaponry. We caught our fill for sure on this ultimately decent day in BHSC. It got windy and cool in the PM however. I had only fished here once per year on the last several feeling it still hadn't recovered from the Hayden fire. It has now, I had a gob of fish on one pass at 400cfs and while none were large, it was fun and encouraging. The weirdest part is that I caught 1/3 rainbows, not Jim though, and GL caught 80% 'bows! I also felt they were the larger and stronger of the catch. Everything we caught was on mayflies as well ~ for me a black ice Perdigon, MHFBPT, or DCEZWD40 and for GL an Anato mayfly. It's good that lower BHSC is back as before this, driving out to the Ark meant a 2 hr one way jaunt. I can fish it again!

I made a full pass and above the boat ramp there's an island which I used for my return. There I surprised a duck on their nest of eggs; it was cool and I went a long way around. I also caught a sucker to cap my ugly triple for the day.

No pics with Greg as he was hiding as we left. Fun outing on the Ark, especially now knowing the lower BHSC has recovered, with rainbows no less. Jim & I got back to town for stellar tastes at Jax with our lady friends...

CoWWBoyz Spring Fly Fishing ~ Upper Ark, 11 Mile Canyon, Trout Ck & More 14Apr24-17Apr24

Rockin' The Upper Ark On Day 1... We first hit the upper Arkansas River near Salida at Rincon & the Chaffe Co line. We crushed it around Rincon with many fish caught on many different bugs in the morning. Rob was into fish and farmed the lower corner. For me the black ice Perdigon, MHFBPT, and Wired Up Ice caddis were the main producers. For most, the mayflies, whatever color, were the main producers. It was a completely gorgeous 65° day in the banana belt, with flows bumped a smidge over 250cfs and the water murky just a bit. Here are some CoWWBoyz (GL, Poop, Rob, & me) in their element on the river and the Murk Brothers (Rick, Matt, Rob & me) on the tailgate of MdB's new tricked Taco.

I caught some 15"-16" browns, one a decent Scottish looking guy, and even scored a rarer rainbow out here. Nice. A good time was had by all.

I was pleased to vacate "Matt's spot" when he rambled down to the upstream section at Salida East with Rob to catch him some more. The freestone Ark is a very cool river, especially when fished with friends.

Slaying It In The Wind On S Platte In 11 Mile Canyon On Day 2... fishing was good despite the cold wind; we slayed many fish today in 11 Mile. There were not even many fishermen ~ the weather forecast likely held many back. We arrived at the last bridge in the canyon at 9am and quickly hit the water to assure decent spots, including "the hot corner." No bug sign but the fish were feeding on our imitations. We even had a couple of doubles for Matt & me and Rick & me. Best bugs were eggs and midges still: money, maroon pop top, purple Manhattan, top secret, etc.

Matt & I hit a double as shown below. Strangely Matt twice hooked into a pike in the depths with a streamer. I wasn't there but hear-tell it was a monster torpedo >27". Thankfully Matt's streamer dislodged before he had to deal with it in earnest. Matt & Rick also did a little comedy act one fish caught.

I roamed the river more than most of the CoWWBoyz, but that's the norm. I caught a number of good fish using the Rodfather Bombadeer and the bugs mentioned above. The browns really liked the egg.

90 Fish Day With Andy @ Rainbow Falls On Day 3... Just wow; we availed ourselves of Mr Holley's generosity and skills (fishing & cooking) today by heading out to Trout Ck & Big Springs. The awful weather forecast and 2" of new snow in Woodland Pk scared most folks away. We were the smart ones ultimately as we threw caution to the wind and were served with an actually gorgeous day of weather and fun. We went early to secure the waterfall spot but the lack of fishermen allowed us to roam all around the bests spots on the property ~ it was amazing.

We all landed fish from our 1st casts, and mostly thereafter to boot! We changed bug strategy as the day and bug activity moved along. Midges in the morning, mayflies mid-day, and a mix in the afternoon. Andy regularly scored nicer fish from holes recently abandoned... impressive. He used the Rodfather Bombadeer all morning (till rigging a dry fly rod). Rob too landed big fish, including the largest trout of his life; on top of the most fish in a day in his life, he scored some nice PRs this day.

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I on the other had kept my catch small & tasteful using the Rodfather Diamond Blaze, while I spent considerable time re-rigging. I capped my incompetence with plenty of failed camera work too this day.

Andy grabbed some keen drone footage. I don't have one so was impressed with it's stability in filming us and the grounds. I caught a pair of eagles circling overhead of the pond where we dined on Andy's fine veggie-free lunch. What a great spot to inhabit given the plethora of their prey... the palominos seem especially easy targets.

At the end of the day Andy took us on a quick tour of facilities including the fish hatchery runs full of trout of all sizes... released on one Saturday per month throughout summer, beginning next weekend! We also stopped at the source of a lot of the water for this private water; "Big Spring" is just that at the base of a ridge on the edge of the property.

It was a remarkable day for many reasons ~ thanks so much Andy. Thanks everyone for coming out for HaineoRADo.