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 Blackout 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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I Started a YouTube Channel – “How to Play” Songs on the Piano – Go Check it Out

Posted on April 1, 2018 by Dan

So a few weeks ago I pulled out my camera tripod, I set it up hovering over my keyboard and with my phone attached to the end, I hit record. I started playing a song, it was Piano Song by Erasure. A song I learned how to play some twenty-plus years ago. A song I taught myself how to play just by listening to the song over and over. A CD player on repeat with my parent’s old upright in the living room of my house growing up. This is something I’ve enjoyed doing ever since I was in grade school to this very day. As the phone recorded while I played through the oh so familiar chords I thought, what if I were to try and teach someone how to play this song? How would I do it? How long would it take to explain? How well do I know the names of all the chords in this song? Do I even play the song correctly? Would people care if it’s not note for note? Would people want to learn how to play this old song from so long ago? Should I post this on YouTube? Aren’t there already a million tutorials all over the Internet already? What difference would one more video really make?

After a couple of takes, hitting record and walking through a simple explanation of the chords for Piano Song, I finally ended up with a take that I thought was decent. Not perfect. But not garbage. I flubbed the chords only once or twice and I didn’t say something completely stupid on that take. I realized it is quite difficult to play piano and talk at the same time (totally different from playing and singing at the same time) especially when the talking breaks up the rhythm and timing of just playing the song beginning to end. And trying to play the piano and speak coherent sentences is no walk in the park either. The main reason it took me so many takes to get just one right. But I was really just playing around at this point. This song would be my “proof of concept” song. I would record it, edit it, add chord descriptions using some form of video editing software (Windows Movie Maker anyone?) and then post it to YouTube and see if I got any bites. This would be the first song, one of many I planned on doing depending if people liked it or not. If it was well received, then maybe I’d do another and another. What if made a video of every song I’ve ever learned how to play? Would people actually watch them? Would people like them? I asked myself all these questions, but ultimately knew there was only one way to find out. I’d have to post it and scariest of all…make it public.

I have to admit though, I am terrified of YouTube. And by that I mean YouTube as a platform for content creators not just for the casual viewer. YouTube is a melting pot for so many different types of people with complex varying interests from all over the world. They get billions of views per day and their market reach is near endless. And the worst part about YouTube is…the comments section. Here you can find the cream of the crop for some of the worst things ever said on the Internet. I just wasn’t interested in playing on that playground. Like the little grade-school boy inside me who liked to play piano instead of sports, the kids here are just too mean. Not to mention the fact that most of the stuff you can find on YouTube showcase people that have spent (what must be the better part of) their entire natural lifetime honing in on a skill that makes them seem almost super human. They have an unnatural ability to outflip, outrun, outplay, outperform, outdive, outrock, out-you-name-it, any talent you actually thought you had. I’m pretty sure there’s a 4-year-old kid that can wipe the floor with my sorry piano-playing skills. Not to mention that one kid who can pick out a Eb-add9-flat5-maj7-11th-over-C# just by hearing the one chord even without any other context (freaking amazing by the way). Makes you pretty much want to crawl back in bed and ask yourself, “What am I doing with my life”? Where comments like, “Kid can do this…I find a Cheeto stuck to my face” are not uncommon. Believe me, I’ve been there, I live there. Not necessarily with the whole Cheeto thing, but as someone who ditched Facebook a decade ago and don’t regret it one bit, I’m definitely not immune to the culture of social comparisons and mentally ranking where I fall in this vast world of talented individuals.

Which brings me back to the piano tutorials. I basically decided to throw caution to the wind and just go for it. I mean, why not? I’ve got about 100 songs in my back pocket that I’ve played for years that I could record today. And easily hundreds more I plan on figuring out just to grow the channel into hopefully something worthwhile. I don’t admit to being an awesome piano player. And I’m sure I will get comments where people tell me I suck or whatever. But ultimately I just decided, so what? I enjoy playing piano and I really enjoy playing all of the songs I’ve learned how to play. And if I can help even one person learn a great song, a song from a band that we both know and love, then it will be totally worth it to me. And as far as everyone else is concerned, well what can I say, haters gonna hate.

Anyway, the plan is to try and upload at least one video per week so that in one year from now I have 52 reasonably-produced instructional videos showing how to play different songs on the piano. For now my main interest will be to do songs that are originally played on the piano and/or are written for the piano. I don’t like adapting songs played on the guitar or other instruments and converting them into a piano arrangement. While I have done that for a handful of songs, I don’t typically enjoy doing them as much and am never quite happy with the way they turn out. So for now if it’s played on the piano and even better, it is primarily played only on the piano with very little other accompaniment, then that’s my jam. Especially because it’s usually easier for me to pick out subtle nuances in chords and chord variations (like inversions and augmented/diminished chords) if it’s just a solo piano playing without a lot of extra instruments backing it.

So without further adieu, I present the latest in YouTube greatness, Dan’s Piano Tutorials – An instructional video series teaching you how to play all your favorite tunes from the 80’s, 90’s and today. Take a minute to check out my channel which as of this writing has a whopping 5 songs including bands like Erasure, Morrissey, Matt Nathanson, Death Cab for Cutie and Coldplay. Click Subscribe to get updates on new videos and be sure to comment on which ones you like best! Also feel free to shoot me suggestions for songs you’d like to see me cover, they can be obscure titles, rare B-sides, deep cuts, or maybe just videos for songs no one has ever done before. I’m always open to a good “figure out this song” challenge. As always, thanks for supporting this blog and I look forward to seeing everyone over on YouTube!

https://www.youtube.com/user/danaktion/

Sample Playlist of my most recent songs from the Dan Marx Piano Tutorial Channel

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Setting up a 3-Way Speaker with MiniDSP 2×4 using REW

Posted on August 5, 2017 by Dan

It’s been about a month since the completion of these speakers and it’s about time I do a write-up on how I set up and tuned these speakers. I’ve spent the last several weeks and many hours setting up and dialing in these speakers and overall I’d say I am very happy with the results of this setup. I doubt this will be my final tuning/crossover setup with the MiniDSP but for now I’m just enjoying the new speakers and how awesome they truly do sound. Because overall the speakers sound fantastic. Better than I could have hoped for. Of course, my opinion is somewhat/mostly biased. But they literally sound just how the response plots would indicate – flat and neutral. No frequency range sounds out of balance, neither too forward nor too timid. But before I get into the subjectivity that is describing hi-fi sound, let me share the setup.

The above block diagram details the setup for measuring and tuning the speakers. The setup starts with a pair of laptops, one running windows 7 with the MiniDSP 4-Way Advanced Crossover Plug-in while the other is running Lunix Mint Cinnamon and REW 5.19 Beta 4. The sound card is a Behringer UCA222 connected via USB. My measurement mic is a Behringer ECM8000 using the cal factors available from Behringer’s website. Home Theater Shack also has a popular cal table for the ECM8000 (newecm.cal) but I felt like it over-corrected above 10 kHz and wasn’t realistic of the actual response of my microphone. When I use it, it causes almost every speaker I own to have this rising tail at 20 kHz that I just don’t believe. Behringer’s correction factor is more subtle and even though I am sure it still does not perfectly represent my microphone, I feel like it’s close enough for casual home use. See my comparison plot below.

Also the Behringer cal table includes phase. I think the main reason people use the newecm.cal is because the correction factor goes all the way down to 5 Hz to satisfy all the bassheads need for insanely low frequency measurements. Since the mic needs 48V phantom power, I use a Behringer XENYX 1202FX mixing console (which is normally part of my home recording studio) between the mic and the UCA222. A Schiit Audio SCH-13 Sys Preamp allows simple volume adjustment of two different sources. For my modest setup at the moment, I have an old Sony DVD/CD player and an Apple Airport Express. Better sources are in the works, including a real pre-amp, but for now, this is what I’ve got. The Airport Express is more for just convenience of listening than any kind of critical listening. Check out this post here on my whole house audio system.

So I debated doing a really nice all-aluminum housing for the MiniDPs and in the end just installed everything into an old VCR enclosure. The big spring-loaded slot in the front makes for easy access to the USB cables that I keep tucked away in there when not in programming mode. It’s not super glamorous, but is functional and practical. Both MiniDPSs are mounted on standoffs along with four LM317 linear regulator kits I picked up for $2 a piece on Amazon. I had an old 15 Vdc wallwart that after tearing it apart realized it was complete garbage. It claims an output current of 1000 mA which is just about right for two MiniDSPs (they draw 150 mA each) while maintaining some overhead. But with only a single transformer, a full-wave bridge rectifier and one capacitor, this would not be my first choice in powering any audio gear. But it’s nothing we can’t clean up nicely with some decent linear regulators. The wallwart provides 15 Vdc and feeds the first LM317 which takes the voltage down to 10 Vdc. The second LM317 takes the voltage down to 5 Vdc and over to the MiniDSP. Each LM317 claims roughly 65 dB ripple rejection so long as Vin-Vout > 5 Vdc at 150 mA. So with two in series, we probably get around 100 dB rejection which should be enough for even the most demanding audio needs. Since the MiniDSP outputs feed the UPA-700 amp with a fixed 29 dB of gain, everything in the signal path and DC bias paths needs to be dead quiet in order to provide quiet, hum-free and hiss-free experience. I think I succeeded because even though there exists what I would call traditional background white noise in the setup, you only hear it from less than 1 foot away from the tweeter with your ear directly in front of the speakers. Once you back up a couple of feet, everything is dead quite. And this is with the original MiniDSP kit which only claim >98 dB SNR. It’s definitely plenty for me. And yes, the MiniDSP’s are on all the time. For curiosity sake, I plugged my little VCR/MiniDSP setup into a Killawatt meter and measured a measly 3 watts (or 0.003 kW/h) which if left on year-round amounts to only 26 kW/year (24*365*.003). I pay about $0.1/kWh at my house on average which amounts to a grand total of $2.60/year. So to leave on a pair of MiniDSP’s 24-7-365 costs less than a side of fries at Five Guys. In other words, it’s basically peanuts. Which oddly enough, you can also get at Five Guys.

I made six sets of speaker cables that are each 14 feet in length from a 100-foot spool of 12 gauge OFC speaker wire from Parts Express. I bought 12 sets of black/red screw-style banana plugs which dressed up the cables nicely and provide a clean transition from speaker cable to the binding posts at the back of the speakers. I wanted to do something fancier on each side, like bundle each set of cables into some nice black expanded cable sleeving but just ended up leaving the speaker cables exposed for now. It’s functional and does the job. No complaints here.

Here’s a quick shot of the back of the upper cabinet with the nice Dayton Audio Premium gold-plated binding post terminals and aluminum face plate from Parts Express. Normally I wouldn’t go all out and buy such fancy binding posts, but for this build I decided they would complement the high-end feel of the speakers overall. They are super nice and provide a robust quality and feel to the speakers. I definitely recommend them for that great premium look.

Here’s the basic microphone setup for doing near-field measurements of just the midrange driver. I moved the microphone around a lot during my measurements. I did near-field plots of each driver at 0.5″ distances and then 6″ and 12″ and 30″ and 1M distances (approximately) as well as in-room measurements. I haven’t done a lot of off-axis measurements yet. But I do plan to take more measurements as time permits. This mic orientation and distance do not represent all of the measurements taken/shown here.

So this is sort of how the setup looked. The old Dell Inspiron was used to connect to each MiniDSP and provide instantaneous crossover and PEQ changes while the HP Elitebook on the right was running REW for taking and recording all the measurements. I only played with one speaker at a time, so I could make all the adjustments to just one MiniDSP unit. Once I was satisfied with the settings, I saved a configuration file and then loaded the settings onto the second MiniDSP. I did some casual listening of various types of music with each setting. Then I would go back to making adjustments as needed and redo the process of tweaking one unit, taking a measurement, loading the second MiniDSP and then doing some listening. I basically did this for about a month. What I’ve really been doing with this whole experience is educating myself on not only the basics of crossover design but some of the more complex elements as well. I figured I have a really nice set of speakers built into a great enclosure, now is my opportunity to really understand the benefits of different slope rates or crossover types on a really nice set of speakers. I have at my disposal the ability to test multiple filter types and slopes and take tons of measurements to see just what makes one filter better than another.

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DM-4 Reference Speaker Build Part V – Finally Complete!

Posted on April 14, 2017 by Dan

The speakers are done! I’m super excited to finally unveil the completion of the DM-4 Reference Loudspeaker. It’s been crazy though, the last few months have been such a roller coaster of different, unexpected projects, as is evidenced by my last few posts. It seemed like with each new project this speaker build kept getting put off more and more. At some point I said to myself, I just need to finish a couple of these other things on the to-do list and then hit the speaker project full-time and just get them done. This has probably been the longest time I’ve spent doing a single speaker build. From conception to completion this project taken almost 3 years. It got the point where in the middle somewhere I completely lost interest in the whole project and began designing a completely different set of speakers. But alas I persevered and now I can say that I am super happy I did because these speakers turned out amazing! Well, in looks at least. As of this post I haven’t hooked them up and actually listened to them yet aside from my initial tuning of lower enclosures which I did a few months ago. The method for creating the crossovers and doing the measurements will have to be saved for another post. For now I just wanted to get the rest of the build pics up and of course the final shots of them sitting in my living room just looking awesome.

It’s funny because as with so many DIY projects, at some point you just have to accept the little flaws in a project and recognize that this thing is made by the hand of an imperfect person. I know I get way too picky about the fit and finish of the final product that can’t enjoy it for what it is. Overall these speakers went together without too much fuss. I’ve been working with wood and MDF and building speakers for many years so I’ve come to understand what it takes to get the job done without making too many mistakes. But when it comes to the final paint and finish work, I’m a complete mess. For this project things were looking good all the way up until I added the Polycrylic clear coat. Staining the birch was a piece of cake, it went on like any stain, really cleanly and looked flawless once complete. I went out on a limb and did the black surfaces with just spray paint and to my surprise that also went on really well. I think I did 3 coats of gray primer and then 2 coats of flat black. I had masked off the birch while spray painting and when I lifted the masking for the first time I got a glimpse of what these speakers were going to look like and I was super excited.

The gray stain contrasting the black just made a killer combination that just looked different from the usual speaker. So I was excited and pumped to put on that first coat of clear coat to give it that clean, smooth, subtle shine to it. This is where it all fell apart. I seriously have to find a better method for clear-coating speakers. There has to be a better way. I won’t go into the details, but I ended up with 4 coats before I just gave up and said it’s as good as it’s going to get. After each coat I’d find a drip, or a spot where I’d brushed it again when I shouldn’t have, or a spot I missed completely. So I’d sand it down and put on another coat, only to miss another spot, over-brush a different spot and end up with a run somewhere else. After sanding down that coat and doing it again and again I just quit and said it is what it is. So that’s when I decided you know what, they’re not perfect and overall they look as good as I ever could have expected them to look so I’m just going to say that I’m happy with them for now. But if and when I learn how to do a proper clear coat, I’ll remove all the drivers, sand this top coat down once again and finish them proper. But that’s down the road, like, way down the road.

Well I should do a write-up on the final build of these speakers. They definitely deserve it, there are so many little details that went into every aspect of making this speaker. You can probably gleam how they were built from all the pics but a few words won’t hurt. I’ve already written quite a bit leading up to this point. A lot of finishing these speakers is just duplicating what I did to the lower cabs. I had just finished building the upper cabinet when I stopped late last year. So I will pick up this post with adding the 1/4″ MDF to the front/top/back/bottom and cutting the 45° chamfer around the edges. The 1/4″ MDF worked out great and gives a clean finish to work with as far as painting goes. Plus it allowed a perfect flush fit for the Dayton Audio drivers. I used Parts Express’s sweet Jasper Jig Model 240 to router perfect holes for the woofer and tweeter. This took a lot of trial and error though! I think I went through 5 different boards before I found a size that allowed the drivers to fit just right without the gap being too big or too small. I was shooting for a gap that was at least 0.005″ but no more than 0.015″. That’s basically a baffle diameter that is 1/32″ larger than the diameter of the driver basket. This allows for some growth from paint/clear coat but no so much that the driver can actually move around. The smaller the gap, the better the finished speaker looks, in my opinion. I did error on the smaller side for the tweeter and I had a tough time getting it fit after the 4 coats of clear coat that lined the inside edge. But since it is probably the only driver anyone is really going to look at, I wanted to make sure the transition from the tweeter’s faceplate to the baffle was absolutely seamless. Plus with the Jasper’s fairly course 1/16″ increments (or 0.062″) I didn’t have much choice with the tweeter as one size was spot on at 0.000″ and the next size bigger left a whopping 0.0315″ gap around the whole tweeter. That was more than double what I had already agreed was reasonable from an aesthetics perspective. So I cut it with no gap and then sanded it slightly to get the tweeter to fit. I then just tried to be careful with the paint and clear coat so as to not decrease that size too much. It worked out, because the tweeter fit by the skin of its teeth and the gap is nearly zero.

The next step was adding the acoustic insulation – I reiterate what I had stated about doing this insulation technique on the lower cabinets that it was an absolute pain and was super time consuming but I think in the end it is going to provide superior damping and absorptive properties than some of the traditional (and simpler) methods. I took a bunch of pictures of each layer going into the cabinet and then made a “sample coupon” on a separate piece of MDF just so show a cool cutaway view of the built-up layers of materials. In short each upper cabinet is covered with 2 layers of 1/2″ (6-lb.) standard carpet pad following by 4 layers of a 80/20 cotton/poly blend fabric/fill and then 4 layers of a 100% poly batting material. The total thickness ends up being almost 3″. Each layer is glued onto the previous layer with spray glue to create one cohesive material that won’t move around and hopefully provide consistent absorptive properties throughout the enclosure and in both enclosures. The upper cabinet is sealed and will have an approximate high-pass filter of around 200-400 Hz so for the most part I was shooting for a nearly-full enclosure, but still ended up with a solid pocket of just air with no fill in just the middle portion. So it’s probably like 75% filled if I had to guess? The lower cabinet only has the walls lined and is probably only 15% filled.

Alright so now the cabinets are done it’s time to start working on the finish. I picked up a can of Winwax “Classic Gray” and put 3 coats of stain the on birch sides for all four speakers. I didn’t bother masking the bare MDF since I was planning on painting it anyway. I should have stained those raw MDF edges better though because the spots I overbrushed with the stain actually sanded nicely and cleaned up that rough MDF edge look and then painted even better. But I did what I could to sand the bare MDF edge so it didn’t look like crap. In the end they are not perfect, I could have done some better edge prep, but they look fine overall and am not going to worry about it too much. After letting the stain dry I masked off the sides and began preparations to paint everything else. I picked up 3 cans of Painter’s Touch 2X gray primer and 3 cans of the flat black. Over the course of the next couple of months I went out to the garage and painted a coat of the primer, then sanded it, then did another coat and sanded it, until I had a really nice flat base finish. Then I moved on to the flat black paint. I also sanded between coats until I had a near-flawless black finish. This spray paint went on really well and I would definitely use this spray paint again. The flat black is extremely flat and I wouldn’t recommend it as a final top coat. It needs a satin or semi-gloss clear coat of some kind to finish it off.

Once the paint was all dry I brought the speakers in the house for the first time. I didn’t want to do the clear coat/top coat in the garage because seriously anything that sits in my garage for more than 5 minutes is immediately covered in a layer of dust/saw-dust/paint-dust/you-name-it-dust. It’s not like I’ve got a 10,000 clean room at my disposal so the house will have to be good enough. I masked off the floor and my coffee table and set up the speakers for their first coat of Minmwax Polycrylic Satin clear coat. I’ve used this stuff before on countless projects and usually praise the ease with which this product goes on. It’s usually forgiving of brush strokes, provides a really consistent sheen across its surface and it’s water based so clean-up is a breeze. But I realized that painting over a solid black surface is not as easy. Every blemish in the coat was readily visible. Any imperfection in the base finish showed through and any area in the top coat that wasn’t applied perfectly evenly was visible when the light shown off it at certain angles. Thus began the paint-sand-paint-sand-paint-sand-paint nightmare that lasted about a week. And yes, with the speakers sitting in my living room just like this pretty much the entire time. Anyway, I called it good enough after that last coat and accepted the fact that once again I’ve nearly ruined a perfectly good project with a shoddy top coat. I started looking at past speaker projects and realized that none of them are perfect and that surely after a while I’d soon forget all about it anyway. I can say that birch sides look great. The clear coat went on and after only the second coat looked great. So I will say that real wood, with a grain and some texture to it, is way more forgiving of the irregularities in the top coat. But that solid flat black was something else. Especially since the fronts have the holes for the drivers, brushing around the driver openings and trying to get it look seamless was just a pain. I’m doing a spray top coat next time. I’m sure that goes on easier.

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