Dan Marx and Kevin Rolfe are DMKR, Cover Classic 80’s Songs

Posted on January 26, 2020 by Dan

This is the story about a cover band. The unlikely duo of two friends who met in high school. Two strangers who bonded over a common love of music – 80’s music to be more precise. A chance encounter almost gone wrong all those years ago with a single answer to a single question initiated by the then stranger named Kevin.

“So what kind of bands do you like?”

The dreaded question of all time for any introverted teen. Unsure of whether or not to admit his true love of all things synth pop, Dan blurted out the one and only band that he could think of in that moment that would surely solicit acceptance, a band that was considered universally ‘cool’ by anyone who was anyone in 1989.

“Um, Def Leppard.”

This answer did not get the expected response. Kevin’s facial expression dropped and he simply replied,

“Oh, that’s cool. I like Erasure, OMD, Depeche Mode, New Order and, you know, bands like…”

Dan couldn’t believe what he was hearing. Another person actually liked all of his truly favorite bands and without hesitation he quickly interrupted,

“Me too! I love all those bands!”

And that was the beginning of a friendship that would endure three decades.

Now after thousands upon thousands of hours gone by over the years discussing artists, music and bands and going to concert after concert as teenagers, these two have recently joined forces once again to bring you their own musical renditions of some of the greatest songs ever written, some of their favorite tunes, by some of the greatest bands of all time.

So sit back, turn up your speakers and enjoy a few songs off of their debut EP, Big Sky Dr.

https://soundcloud.com/dmkrmusic/

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Making of The Dayton Reference 2-way MTM Center Channel Speaker

Posted on November 20, 2019 by Dan

Shortly after completing my Dayton HiVi RTS181.3 speakers, I got to work on a matching center channel to finish off the front sound stage of my family room theater. And this weekend, after approximately 10 weeks since I started this little speaker project, I can finally say it is now complete! And what can I say about how it sounds? Well in a word, it sounds fantastic! And just in time to binge watch all of our favorite Disney movies on Disney+ to boot! As with most of my speaker builds, here’s the matching blog to describe the design and build process in its entirety, show of some pictures, talk about the crossover, show some response plots and give my overall thoughts on this speaker for anyone out there hoping to design and build something similar. This is an awesome center channel speaker, so far everything I have watched sounds neutral, clear, detailed and all around very good. Read on to find out more.

First off, some quick stats: the Dayton Reference 2-way center channel speaker consists of a pair of Dayton Audio Reference RS125-4 5″ aluminum cone drivers matched with the RST28F-4 1-1/8″ soft dome tweeter in a horizontal MTM configuration. The enclosure is made from 3/4″ MDF with solid 3/4″ oak side panels for a decorative, classic look (and to match their complimentary LR speakers). The cabinet is 19-1/2 x 5-1/2 x 10 inches (WxHxD) which equates to about 8.7 liters with a 2 x 6 inch port which results in a 60 Hz tuning frequency and an f3 of 58 Hz. This is an optimized cabinet volume for a pair of RS125-4 drivers resulting in a maximally flat response though excursion below tuning needs to be kept in check. This speaker will perform best when used in a home theater environment with the receiver settings set to SMALL or at the very least with a high-pass filter set no lower than 50 Hz. The crossover is a fairly simple 12 dB/octave topology on both the woofers and tweeter centered around 2,700 Hz with a fixed L-pad on the tweeter (and a notch circuit to tame a response peak at around 15 kHz). A total of 12 elements are used made up of air core inductors, metalized polypropylene capacitors and non-inductive resistors. A 5-way binding post speaker terminal mounted in the rear provides easy connection to the receiver. The cabinet walls are lined with 100% cotton batting and the cabinet is 50% loosely stuffed with 100% polyfil stuffing. And that’s about it!

Okay so let’s get right down to the nitty gritty of this speaker project – the design. I went through many of iterations of center channel concepts before ending up on this one and I know what you’re thinking, you’re thinking Dan, this is a basic, no-frills, run-of-the-mill, crappy, horizontal MTM speaker that’s going to suffer from all the same problems every other cheap horizontal MTM center channel speaker suffers from, what do you mean you spent hours and hours designing this thing, it looks like it took you 5 seconds to plop those three drivers into place, this is boring, I’m outa’ here. And you’d be mostly right, this design is arguably flawed at the outset in that it suffers from poor horizontal off-axis response due to overlapping sound waves from having two drivers spaced 8 inches apart from each other on the front baffle and producing the same frequencies. This effect (typically referred to as lobing or comb filtering) can be easily be verified by modeling this driver layout in a crossover simulation tool such as Passive Crossover Designer (PCD).

But before we get to that, I had designed on paper a wide variety of other driver layout combinations that perform much better than this design in both frequency extension, power handling and off-axis performance, but still I ultimately settled on this one for a variety of reasons which I will get into. This is where we come to the part about DIY speaker building that I love so much. Every speaker design has its strengths and its weaknesses. Every design has inherent constraints that must be managed and balanced. My constraint isn’t your constraint. What looks good doesn’t sound good and what sounds good doesn’t look good. And so on and so forth. I simulated tons of driver layout combinations using PCD for horizontal off-axis response and basically came to this conclusion: the absolute ideal layout for a center channel speaker when it comes to horizontal off-axis response is to use a single full-range driver or a point source. Every other design that deviates from this is a compromise with respect to ideal off-axis response.

Since full-range drivers in and of themselves are a compromise in other ways, that design choice would simply trade one limitation for another. And while super-flat off-axis response plots look great when showing off a speaker’s performance in audio forums and with your audiophile friends, its real word benefit is far less practical, in my opinion. At least with respect to center channel speakers in a home theater environment. I believe better off-axis response has far more merit in two-channel audio listening environments than anywhere else. But when it comes to a center channel speaker playing dialogue from a movie, how critical is having ruler flat off-axis response? Is it because of poor ole’ Grandma sitting in the far corner seat on the couch constantly saying, “What he’d say? What’s going on? I can’t understand anything they are saying”. Everyone else will just think Grandma needs to turn up her hearing aid, but you will know the truth, the real reason she’s oblivious to the movie’s plot: your crappy MTM center channel puts a massive null in the frequency range of human speech right at that spot on the couch where Grandma likes to sit. If only you’d forked over a few more bucks for a bigger, better center channel, perhaps a 3-way design that aligns the tweeter above the midrange driver and uses two woofers with a crossover frequency that’s nice and low so as to minimize the effects of comb filtering, then maybe Grandma would actually know what’s going on during movie night for a change.

That’s okay, I’m not going to lose sleep over building an MTM speaker and flipping it on its side into its worst possible orientation because ultimately there are far more reasons for movie dialogue to be unintelligible than a little off-axis comb filtering. It’s true though, in free space, or measured near-field, the off-axis horizontal response of an MTM flipped on its side is pretty abysmal. Which can be confirmed in both simulation and in real-world measurements. See the various graphs I’ve shown here that showcase this effect in both simulations and in measured data for this speaker. So what can be done about it? And does it really matter? So first and foremost, the best way to combat poor off-axis response is to change the layout of the drivers. Go point source, as mentioned above, or coaxial with the tweeter inside the woofer, a design KEF capitalized on years ago which has done them very well. More recently Parts Express has started to offer some inexpensive coaxial drivers for those aiming for that truly point source sound. If I were to build another another center channel today, I would probably like to do a 3-way using that Dayton 4″ coaxial driver paired with a set of RS150-4 woofers à la Elac’s Uni-Fi UC5. I drafted up this design and it looks pretty awesome (see pic above, top left image). I wish PE offered more coaxial options that like. But if none of those options suit your fancy, then a regular MT speaker with the tweeter above the woofer is the next best layout option. Even if it doesn’t “look right” sitting underneath your TV, it will have very good horizontal off-axis response. Just behind that is the same MT speaker but rotated on its side. In this case you swap horizontal off-axis performance of a typical 2-way speaker for its vertical performance. Still not a bad deal if you’re in a pinch but definitely better than a straight horizontal MTM layout.

The next best option is to go MTM but design the crossover as a 2.5-way. This way you get the nice bass response of dual drivers, but you set the crossover point for just one of the drivers much lower, say only a few hundred Hz, so that only one driver is producing frequencies where comb filtering typically starts to become a problem. With only one driver producing the higher frequencies, the setup behaves more like an MT on its side but has the benefit of additional sensitivity at the lower frequencies, better power handling and increased bass performance due to the dual drivers. One of the best layout options that is becoming more and more popular is one that basically combines the two previous designs into a single 3-way speaker with the tweeter above the midrange and a pair of woofers on either side. The midrange and tweeter behave like an MT rotated vertically (yeah) and since you’ve got that dedicated midrange that can play fairly low, the two woofers on either side, albeit far apart from each can be crossed over very low so as to where comb filter effects are minimized. Keep the two woofers close enough together with respect to the crossover frequency and lobing won’t be significant at all, or at best, only start to come into play way off axis, beyond 60 degrees or so. Which is completely reasonable for movie and home theater environments. Most TV’s start to look like garbage beyond 30 degrees off axis anyway, so now Grandma can complain about not only not being to hear the people in the movie but how your 4K HDTV with HDR10 looks like crap from her spot on the couch. Guess what, she won’t be wrong! Hey, I can only make so many people happy. Wait until you put a microphone in Grandma’s seat and measure your subwoofer only to realize that guess what, she’s got the most bumping seat in the house! Go figure. Of course she does, it’s in the corner where no one else wants to sit. TV looks like poop, can’t understand the dialogue and there’s so much bass her dentures keep rattling out of her head. I’m starting to think Grandma might not come over for movie night any more.

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Introducing the Dayton HiVi RTS181.3 Two-Way Bookshelf Speaker

Posted on August 26, 2019 by Dan

A few months ago I decided to redo a pair of bookshelf speakers I had built almost 15 years ago. Click here if you want to check them out. This speaker makeover consists of swapping the HiVi Research W6 driver for a sleeker Dayton Audio RS180-8 7″ woofer and replacing the vanilla Vifa dome tweeter with a HiVi research RT1.3WE planar ribbon tweeter. And the results turned out awesome. The speakers sound much better, have a smoother, flatter frequency response, have more bass, more treble (thanks to a much more complex crossover) and I think they just look a lot better, more modern, more high-end then they did before. This blog post is meant to serve as the condensed version of a forthcoming (and much longer) post that goes into a lot more detail surrounding the design aspects of this speaker with a special focus on the crossover. For this post, I’m just going to show off some pictures and kind of walk through the process of taking this old pair of speakers and making them shiny and new again. I’ll also share some of my thoughts about this speaker project overall for those looking to embark on something similar.

With a retrofit build like this there were two basic criteria I had to stick to when picking out a new woofer: it had to model/sim well in the existing enclosure volume of 0.57 cubic feet and it had to physically fit in the cutout of the old woofer. This actually narrowed my search down quite a bit. Parts Express has a great selection of 6″-7″ woofers that would have fit the bill nicely, but when I ran the numbers for the Dayton Audio RS180-8 aluminium cone woofer, I knew I had a winner on my hands. I’ve used several Reference Series drivers from Dayton Audio and they never disappoint. It modeled great in the volume I had, and even with the original tuning frequency of 42 Hz, I wouldn’t even need to change the port length, and being that it is a 7″ woofer, it actually fit the opening almost perfectly compared to the old Hi-Vi W6 woofer. And with the woofer all picked out, I moved onto the tweeter selection.

This proved to be a much more difficult task. The original tweeter cutout matched a fairly standard 104mm diameter faceplate, common with a lot of tweeters, especially Vifa tweeters. It would have been easy to pick up a XT25TG30 or a DX25BG60 and they would have dropped right in, but I really wanted to do something different, something more challenging and more of a departure from the original tweeter, which was an older Vifa DX25TG soft dome. I wasn’t exactly sure how I was going to flush mount a new driver with a different diameter faceplate onto a speaker that already had a hole cutout in the middle of it though. So that was my original hesitation to selecting a completely new tweeter. But once I figured that out though (which I’ll go into below) I ventured beyond identical tweeter sizes. That’s when the HiVi Research RT1.3WE planar ribbon tweeter caught my eye. This tweeter looked sweet! A planar ribbon type tweeter with a nice and flat frequency response, a flat impedance curve and a huge 4.7″ aluminum faceplate. I quickly sketched up some drawings of these two drivers mounted into my pre-existing enclosure and they looked absolutely fantastic. Driver spacing was perfect on the front baffle and the dark gray surround color of the Dayton woofer matched the dark gray aluminum faceplace of the HiVi tweeter nicely and I just loved that little hint of copper peeking through its metal grill. Also the black metal grill actually matches the black aluminum cone really well. And that grill would help keep kids’ poking fingers at bay. I had found my tweeter. I added a pair of woofers and tweeters to my shopping cart and week later these beauties showed up at my doorstep. Let the speaker project begin!

With drivers in hand and the speaker enclosures already done, I had to figure out just how to get these new speakers to work with the existing holes of the original speaker boxes. For starters, I really wanted to flush-mount both the woofer and tweeter. Which is really what made this whole process just that much harder. With holes already cut in the enclosure, there’s no way to get a router in there to make a perfect circle to create a recess for the driver basket because there’s just a big open hole there. Normally you would use a circle jig with and a center guide pin in the middle of the location where you want the driver and you router the recess portion first, and then go back and cutout the driver hole. Or in some cases you can add another thinner board on top of the baffle that is cut out separately from the woofer hole. Both options seemed like non-starters. The speaker hole was supposed to come second, not first.

That’s when I came up with the idea to glue a strip of MDF inside the cabinet to the backside of the front baffle that had small blocks of MDF glued to it that were equal to the thickness of the baffle. This basically put a piece of wood just big enough for the guide pin of a circle jig to fit right in the middle of each driver cutout and at the same height as the baffle. As if the holes weren’t even there. And with that, I set the circle jig to the exact size for the woofer and tweeter, set the depth to match the thickness of the drivers, and cut out with perfect precision the recesses required to flush mount each driver. After that was complete, I ripped out that temporary MDF strip and small wood blocks and was left with a perfect recess to fit the new drivers. Well, I still had to take a jigsaw to the tweeter cutout because it was literally fitting a square tweeter in a round hole. The HiVi tweeter housing has a rectangular shape so I just had to cut little corners out of the existing round hole from the previous tweeter and I used a paper template as a guide that that matched the tweeter dimensions for doing so. Piece of cake. Let’s move on!

Alright so this is where we get to the abridged version of this blog post, the crossover design. This seriously deserves a complete post of its own and I’ve actually already started writing it, and it’s long, and wordy, and goes on and on about concepts of baffle step compensation and notch filters and discusses in detail response plots from REW of literally hundreds of different crossover combinations that I tried before settling on the final design you see here. So I won’t rehash those details again. Suffice it to say, I ended up with a ~2,800 Hz crossover point and 24 dB/octave slopes, a full 6 dB of baffle step compensation (which after two weeks of really listening in my actual room, I revamped it to be only 3.5 dB of BSC and to me they sound way better, see updated schematic to the left) and notch filters on both the woofer and tweeter to help clean up some driver resonances. In all, the crossover has 15 total elements, which is bigger and badder than any crossover I have designed to date. They were so massive in fact, that I didn’t even end up putting them inside the cabinet, I built separate little wooden enclosures to house all of the capacitors, inductors and resistors. This certainly is not everybody’s cup of tea, but I had more room to store the crossovers outside than I felt like I had space inside the enclosures. So I just went for it and made the entire crossover its own little box, painted it black, stained it dark brown and said to myself, well isn’t that fantastic!

My wife’s first comment when she saw them was, “Where do you plan on putting those?”. I resisted the urge to say, “They mount above the speakers on the wall, like picture frames!” Showcasing my beautiful crossovers next to pictures of our beautiful children. Instead I replied, “They’ll go inside or underneath the media console, don’t worry, you’ll never see them.” She made a grumble and walked off only half satisfied with my response. To be fair to her, at this point in the whole speaker process, it had been months since I started. I had taken over half the house with all my speaker measurement gear, laptops, amps, mixing consoles, wires galore, not to mention the speakers themselves half-finished, everything just sitting in whichever room I had commandeered for the week to do all of my speaker testing. So when I took over the kitchen table to solder the crossovers into these little boxes, I could understand her curiosity. I think she was happy though that the crossovers would not become a permanent part of our family room decor. As you can see in the finished pictures, the crossovers fit nicely into the bottom cabinet of our media console and sit up against the sides, with the door closed, they are completely out of the way, out of sight, out of mind.

Jeesh Dan, that’s the abridged version? Yup, just dumb stories and no technical substance, for now. I’ll let most of the pictures do the talking. All anybody really wants to see is pictures anyway. The crossovers feature all air-core, low-DCR inductors, metalized polypropylene capacitors and non-wire wound resistors. I used Passive Crossover Designer 7.0 to simulate and design the crossovers and used REW (Room EQ Wizard) to take all the measurements, 533 measurements in total, once all was said and done. I finally realized the limit to the number of graphs you can display at once in REW – and it’s 99. And you know what? Sometimes, it just wasn’t enough. Moving on.

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How I Turned an Old HP Tower Case into an Awesome HTPC Case

Posted on June 8, 2019 by Dan

Let’s face it, the era of the HTPC, or Media PC, is just about dead. With support for Windows 7 finally coming to a close, and by extension the renown Windows Media Center (aka WMC), combined with the fact that just about every smart TV on the planet these days comes with built-in apps for streaming Netflix, Amazon, Hulu and YouTube, there just isn’t a compelling need for a massive computer tucked inside your media cabinet anymore. I built my first HTPC over 10 years ago and I’ve become reliant on it as the hub of my family room entertainment system ever since. While external set top boxes like Roku, Apple TV, Amazon Fire Sticks, and of course smart TVs, have taken over what once was one of the great advantages of the HTPC, namely watching unlimited amounts of streaming TV and movies, there’s some things that old HTPC still does best.

Such as pop in a TV tuner card and you’re watching live over-the-air (OTA) TV in HD. Can’t catch a show when it airs? WMC lets you record all your favorite shows and then watch them anytime on any computer in the house. And it just works, every time. How about that pile of ripped DVDs that play perfectly with VLC Player (and in 5.1 surround sound) that basically are unplayable through almost any other means? The HTPC has you covered. Or log into Google Photos to watch last night’s ballet performance on your big screen (since the first time you watched it, it was through your dinky phone). What about a game of Kahoot!? It’s a party when everyone gathers around the TV for a round of “Name that Disney Movie!”. And those are just a few of the things that an HTPC is awesome at. Or at least I haven’t figured out a better, cheaper, more elegant solution to do any of those things, so why mess with it?

When we recently renovated our family room, we got rid of our massive entertainment center and downsized to a simple media console, I knew I had to figure something out for the ‘ole HTPC. It was basically just a computer, it was huge (and ugly) and would not fit inside the tiny compartment of the new media console. Plus it was old, just about 8 years old now but still going strong with an old AMD A4-3400 APU and Radeon 6410 graphics, it’s worked out well over the years. However, as more and more 1080p content became available, and more and more streaming options online moved to 1080p, this old machine was often be pegged at 100% CPU usage. Doing anything besides watching a DVD or TV show in WMC nearly brought it to its knees. I’m looking at you iTunes.

I bring this up because it would have been easy to buy a smaller HTPC case and swap the old mATX motherboard, HDD and PSU into a new rig that would have fit just fine into the new media console, but I was ready to upgrade that old thing and figured now would be a great time to do it. As it would happen, I purchased a used HP XW4600 workstation PC a few years ago that never really got used for anything and was just sitting out in the garage. It’s got a Core 2 Duo E8500, 3.16 GHz Intel processor with 8 GB of PC2-6400 DDR2-800 RAM and an Nvidia Quadro FX 1800 graphics card. It’s all 9-year-old tech by today’s standards, but still more than enough for an HTPC, even if it wouldn’t be 4k capable. I knew this would still make a great, albeit modest, upgrade to my current setup. Only there was one major problem with this whole plan – the motherboard was a full-size ATX motherboard. So in other words, it’s huge. I searched online for media cases that support full ATX motherboards, they are few and far between, plus they are expensive. More than the combined value of the parts I would be putting inside. SilverStone makes one, it’s not flashy, but it’s still $100. While reasonably priced, I was hoping to convert this old HP XW4600 tower into a usable HTPC for less than $25. So with that, I concocted a plan and I hereby present you with how to create the ultimate DIY computer case for *less than $25.

Before I start, let me just say that I won’t be going into any of the computer building details, and this it not a how-to build a HTPC blog post. I basically took an old HP tower and gutted it and just reassembled it into a custom case. So that will be the focus of this blog. Nothing more and nothing less. Well, I added a couple of extra fans, a TV tuner card, a 5.1 sound card and second HDD, but that’s just standard routine for just about any HTPC. Oh yeah, and I, um, ditched the optical drive completely. Which oddly enough is exactly what makes this entire rig actually possible and super easy to pull off. If you’ve come this far, but are dead set on keeping an optical drive in your setup, take this information for what it’s worth. Most of what I did will need to be modified to allow room for an optical drive, somewhere, I don’t know where, one won’t fit the way I did it, which is why I opted to eliminate it completely. I can’t remember the last time I used an optical drive in my HTPC, let alone an optical drive in any of my computers for that matter. So what good is a Media PC without a, um, media drive? Well ask yourself, when was the last time you used some kind of physical media lately?

Alright so let’s get to the build. First things first, gut the case. Actually before that, find a clean, open place to set up shop for a couple of days, because this build takes at least a solid weekend to complete. With all the old gear out, now’s a good time to vacuum out the 10 years of dust that’s been building up in there. If possible, remove the 5.25 inch bays and the 3.5 inch HDD bays so you’re left with just the bare case. On the XW4600 these pieces come apart from the case with a few discrete little screws. So discrete that I didn’t realize they came out until after I had cut the case in half. Or rather, I cut the case at 11 inches from the back. The original depth of this case was 17 inches and the depth of my media console is only 15 inches. Which means for anything to fit inside it, it really needs to be about 14 inches or less, to allow room for cables and wires to come out the back and not get crammed into the wall behind it.

A standard ATX motherboard is 12 x 9.6 inches so 11 inches is about the smallest you can go before a standard ATX form factor motherboard won’t fit anymore. The width of the case is 17.75 inches (or I guess that’s the height) which is also pretty standard for a midsize tower such as this. My media console is 19 inches wide so this just about maxes out the size that will fit while still leaving some room for airflow for the pair of fans on each side. I used a jigsaw with a metal cutting blade and after marking a line around the entire case at 11 inches, I just took my time and cut along the line. I kept a Shop Vac on with the hose inside the case to suck up the metal shavings as I cut. With the case literally cut in half, I took a piece of sandpaper and sanded down all the edges since the jigsaw leaves a pretty ragged cut. But once sanded down, it’s nice and smooth and the potential for any additional metal shavings getting into the computer is eliminated.

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Weekend Project: Build a 108″ DIY Projector Screen for $28

Posted on August 5, 2018 by Dan

This weekend I built a super-cheap, no-frills, 108″ projector screen for my family room home theater. A modest setup consisting of a Pioneer 7.1 AVR, some DIY speakers and sub I built years ago and a 50″ Panasonic plasma HDTV. We’ve got the usual array of sources as well – a Panasonic Blu-ray player, Xbox 360 and the ubiquitous Home Theater PC (long live Windows Media Center!). I’ve been toying around with the idea of a garage theater for the last year, so I do have a projector, but have yet to bite the bullet on formalizing some kind of air conditioning out there, so in the summer months, movies in the garage come at a fairly high cost of nearly sweating to death.

I always thought it would be fun to just bring the projector in the house and project on a wall so we could watch movies in the (air conditioned) house, but there was just no good place to put it where there was easy access to the existing home theater equipment and a good wall to hang a screen. That’s when I started concocting a plan, a plan which involved making a super cheap screen which I could actually hang from my existing entertainment center in front of the TV/stereo/center thus making the transition from TV time to full-blown-movie-going extravaganza as easy as hanging a picture on a wall. And since I wasn’t sure how this would work out overall, I started out thinking this would just be a proof of concept only, so I did it as cheaply as possible. This whole thing only cost $28. So far it’s worked out so well, I see no reason to upgrade or change it out for something “better”. So without further adieu, I offer up this tutorial and a few pictures for you so you too can transform your family room home theater into a bigger, better movie experience for less than it costs to take the kids to Chick-fil-A.

List of materials:

Qty (3) yards Roc-Lon Blackout Fabric (white/white or white/beige) from Joann’s (54″ wide) – $12 (with a 50% off coupon) normally $7.99/yard – don’t forget the coupon!
Qty (4) 3x1x96 inch furring strip pine lumber – $6 – The Home Depot
Qty (6) 2×4 inch Simpson Strong-Tie Mending Plate – $4 – The Home Depot
Qty (2) D-Ring Frame Hangers – $2 – Walmart
Qty (2) Small Caribiner – $2 – Walmart
Pack of 3/8″ Heavy Duty Staples – $2 – Walmart

List of Tools/Supplies:

Staple Gun
Scissors
Measuring Tape
Miter Saw
Titebond II Wood Glue
Orbital Sander and 60 grit sandpaper
Cordless Drill and Drill Bits
Phillips Screwdriver
Square

First and foremost, let’s talk about the Roc-Lon Black Out fabric. They sell 4 different colors as well as mixed front/back colors but you want to note the color of the backside of the fabric because that is the side you will project onto. The frontside, the side that is rolled outwards, has a bit of a texture to it, but the backside is smoother, has almost no texture and is more rubbery – that is the side you care about. My Joann’s had a white/white, a beige/white a beige/beige and an ivory/white (front/back) to choose from. I ended up getting the beige/white because the roll had more fabric on it and looked like it was in better shape. I was worried about whether or not wrinkles would iron out or not stretch out properly. You just want to make sure that the backside is white, but the frontside doesn’t matter as much.

Turns out that you can iron this fabric and small wrinkles will stretch out so you don’t have to be too fussy about the condition. Quick tip though, bring your own 2″ cardboard role and after they cut it have them re-roll it onto your own role, otherwise they will fold it 3-4 times over which creates creases. They did this with my fabric and I didn’t think any of it at the time, but it creased badly, which meant I had to spend 30 minutes trying to iron out all the wrinkles, which like I said you can do, it does work, but it’s extra time that would otherwise be unnecessary if I had just been a little more prepared going to the store. They may have extra rolls there too you could ask them nicely if they’d roll it for you. Also, don’t try and iron the rubbery side, aka the projector side or backside, it doesn’t work well and will ruin the texture on that side, you have to iron the frontside/fabric/texture side. It’s still not easy to iron a huge 54″ x 108″ piece of fabric though, without creating creases as you iron out creases just trying to manage this beast of a piece of fabric on a tiny ironing board.

So I had purchased the Carl’s Place Sampler Pack a couple of months ago and was planning on buying one of their premium screen materials, so I was able to compare some of their samples to Joanns’ Roc-Lon blackout cloth and here’s what I can say about the similarities. The “frontside” of the Roc-Lon blackout is very close to “backside” of the very popular Carl’s place standard white Blackout Cloth. It’s got the same type of fabric-like texture to it, it’s almost the exact same color white and has similar stretching properties although the Carl’s Place Blackout cloth is slightly more flexible/stretchier. But the backside of the Ron-Lon fabric looks and feels almost exactly the same as the frontside of the Carl’s Place Blackout cloth, which is why if you buy this fabric, you will want to project on what is effectively the backside with respect to how it’s rolled, since it matches the definition defined by Carl’s Place as “the smooth texture side with a rubber coating faces the audience”. Both materials are the same thickness as well measuring 0.014 inches [0.35mm] thick. Visually, using projected content, the Roc-Lon and Carl’s Place blackout cloths are nearly indistinguishable in terms of white/black levels and color balance. I observed no obvious hot spots or changes in texture or sheen that would be observable or distracting in any way.

I’ve got some pictures of the fronts and backs of both fabrics in both natural light and projected light so you can see the differences. I’d probably have to give the edge to the Carl’s Place Blackout if I were being super picky about the texture, because the fabric texture bleadthru from the other side is ever so slightly less obvious on the CP Blackout cloth than with the Roc-Lon Blackouut but we’re talking nanoinches. And it depends on which location in the fabric you’re looking at. Click on the two pictures above and you can see what I’m referring to. This is with natural light, it is far less obvious with projected light. Of course the most obvious disadvantage to the Joann’s stuff is you’re limited to a 54″ height. Which works out to about 53 usable inches vertically (once you wrap and staple it to a wooden frame) and 94.25″ horizontally which makes for a 108″ total diagonal screen with a 16:9 aspect ratio. Carl’s Place doubles that to 110″ allowing for some extremely large screens.

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Decoding the Signal Path of My 2-Channel Stereo

Posted on April 21, 2018 by Dan

Last week I changed around my stereo a little bit just for fun and wanted to share a few of the things I learned in doing so. I didn’t do anything too crazy, just removed the Schiit SYS passive pre-amp and replaced it with a Denon AVR-1801 receiver. The receiver has been part of my garage theater which is currently undergoing some modifications. So I thought this would be a good opportunity to add it to my 2-channel stereo setup so I’d have an actual active pre-amp in the mix. Or rather, an active 5.1 receiver that happens to have a pair or RCA pre-outs (not something every receiver has these days I’ve come to find out) that should double nicely as a dedicated pre-amp. Acting as a pre-amp only the Denon holds its own quite well. A plethora of inputs, optical, coaxial, analog, even a phono input. Right now I’ve got two modest sources, an Apple Airport Express and a Sony DVP-S300 DVD/CD player. It’s worth mentioning that I bought the Sony unit from Goodwill for $6, the Airport Express from a guy on Craigslist for $20 and the Denon unit from a different guy on Craigslist for $50. Total investment at this point – $75. I do audio on the cheap, I know. But good gear doesn’t have to cost a fortune either. And good used stuff is even better.

Now back to the setup. Since the Denon has both analog and digital inputs, I was left with two connectivity options for each source: connect the CD player and Airport Express to the analog CD/DVD inputs using a couple pairs of RCA cables, or connect the S/PDIF or Toslink output from the CD player/Airport to the S/PDIF and/or Toslink inputs on the receiver. Either way you get sound coming out the other end. What difference would either option make? Was there not an obvious better way to connect up this equipment? If so, what was it? And was there a way to know which option would be better without actually listening to them?

So my first instinct was to connect everything up using only the digital interfaces. I figured the Denon probably has a better digital-to-analog path in it and therefore would sound better. This means the conversion to analog is bypassed on both the Apple Airport and Sony units to allow the Denon unit to do all the work. I have nothing against running analog in’s and out’s between stereo gear, but if you can keep things in the digital domain longer, and not flip flop between them too often, then it just seems like that should be better. Especially if you have reason to believe one of the two potential DACs and subsequent analog parts in your signal path is significantly better in one piece of gear than in the other. Imagine having two pairs of speakers connected to your amp via an A/B selector switch and selecting the crappier speakers all the time without even realizing it. Little did you know that just by switching to “speakers B”, you could have been listening to a much better pair of “speakers”, you just had to pick the better pair and put those in your signal path. Just about every stereo setup anyone owns probably has an unused DAC in there somewhere. Missed opportunity perhaps?

After connecting the CD player to the Denon via the S/PDIF port, I popped in some CDs and had a listen. Up until this point my setup was such that I was using the DAC in the CD player to convert the digital 1’s and 0’s to analog, but now I was feeding those same 1’s and 0’s to the Denon unit and allowing it to decode and convert those bits into analog sound. So what did I think? Did it sound better? Actually, my first impression was that it did sound better. Inexplicably better, not definitive, but somehow just better. Maybe I was just hearing things? Probably, but could I prove that one setup was superior to the other? Sure, why not? So I decided to do a little deep dive into the physical signal path differences between these two setups and compare them. What is actually different? Which configuration looks better on paper? What DAC chips are actually in these units? Were there other obvious defining differences? Read on to learn what I found out.

For now this is just going to be a paper analysis. I’m not going to actually measure anything. So if you’re hoping for FR and phase plots, THD and FFT plots, sorry to disappoint. But this is an easy analysis just about anyone can do with their own stereo, though your mileage may vary depending on which gear you’ve got, brand and how old (or new) it is. The internet is a huge resource, but even then, some old parts are just not going to turn up. And some of the newer and boutique audio shops just aren’t going to publish that kind of info. No sense revealing the Colonel’s secret 11 herbs and spices.

You can download a pdf of the information I put together for this chain analysis here which includes excerpts of schematics and block diagrams for both units. Datasheets for all of the components can be found by clicking the hyperlinks within this post.

I started out by searching for service manuals for both the Sony DVD/CD player and the Denon AVR. Service manuals are great for digging into this kind of thing and I found a ton of super useful information on both units. Such as schematics, part numbers, troubleshooting tips, you name it, these service manuals had it. That’s when the fun began! I traced out the digital and analog signal paths for each unit starting at the optical transport and finishing at the pre-out of the receiver. The one thing I was interested in initially was what DAC was in each of these units (but I actually learned quite a bit more). I was hoping from there I could then find out some specifications that might indicate which one should be better. My search didn’t stop at just the DAC though. But I’ll jump right into that part, since it’s the most relateable component. And if you don’t end up reading this entire article, you will at least have learned that much.

The Sony DVP-S300 contains a Sony CXD8750N-T2 2-channel DAC. There is absolutely zero information about this DAC available online. It is most likely one of Sony’s proprietary designs so they aren’t inclined to publish anything on it which means there’s no info out there to get any sense of what the DAC can do. Searching the part number online reveals that it appears in units with model numbers M35/S300/S305/S315/S500D/S705D/S715. So it was a popular DAC in its day used in a wide variety of now discontinued models. Not much else go go on there.

So let’s move on to the DAC in the Denon receiver. This is where it got a lot more interesting. The DAC in a Denon AVR-1801 is an AKM AK4527 “High Performance Multi-channel Audio CODEC”. AKM have been making DACs for ages and have a wide portfolio of DAC and DAC-related products. The the most interesting thing noted in the datasheet for the AK4527 is they claim it supports multi-bit. The first paragraph in the data sheet states,

“The DAC introduces the new developed Advanced Multi-Bit architecture, and achieves wider dynamic range and lower outband noise.”

There is no other mention of multi-bit in the rest of the datasheet and in most cases there are references to sigma-delta processing if it does come up again. I have no idea if this DAC does in fact support multi-bit as it’s commonly referred to today or not. This data sheet is dated 1999. Other specs tout 128x oversampling, 96 kHz sampling rate, 24-bit 8x digital filter, 106 dB S/R and high jitter tolerance. EEtimes.com wrote a short article about this DAC when it was released back in 1999 and here’s a short excerpt from that article:

“The six D-to-A channels use a new multi-bit sigma-delta architecture with 128X over-sampling. The dynamic range in this direction is 106 dB. This part brings a new performance level to multi channel codecs,” said Ahmad Nowbakht, applications engineer at AKM Semiconductor, a subsidiary of Asahi Kasei Microsystems Co. of Tokyo. He suggested the AK4527 could be used with compressed audio applications such as AC-3, DTS or other multi-channel standards. “It could be used in DVD players, DVD-RAM drives, or home audio receivers along with many other multi channel audio systems,” he added. The AK4527 is packaged in a small 44-pin LQFP, 10-x-10-mm, package with the same pinout as AKM’s previous two-input/six-output codecs. Prototype quantities are available now, priced at $6.12 each for 5,000 pieces.

So there you go, what’s the real takeaway? That they use the term multi-bit and sigma-delta in the same sentence? Like, which is it? How about the fact that this is a $6 DAC? Either way, if I had to blindly pick a DAC in my setup, either the Sony unit or the AKM unit, based on the information available, I’d probably pick the AKM DAC over the Sony DAC just because it’s got some decent specs against a part that has, well, no specs. It offers good dynamic range with 24-bit/96 kHz processing whereas the Sony DAC probably only supports 16-bit/44.1 kHz audio, seeing as how it is designed for a regular CD player, ideally there’s no reason for anything higher. Besides the bit depth and sample rate, are there other less obvious sonic benefits to one DAC over the other? Perhaps other features built into each chip make a larger difference, like better digital filtering, better tolerance to jitter, better DC biasing (power supply and power supply filtering) and better analog filtering. Specs alone hardly tell the whole story. But it’s certainly a starting point.

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