Sealed 15″ Ultimax + MiniDSP + Crown XLS 1002 + Remote Trigger = Killer Subwoofer Project!

Posted on August 17, 2020 by Dan

About a year and a half ago the wife and I decided to retire our old entertainment center and completely make over our family room. We bought a new TV, a huge couch/sectional, a new area rug, a new leather ottoman (thanks Costco for basically furnishing my house), installed a bunch of ship-lap on the wall (thank you Fixer Upper for putting ideas into my wife’s head) and we bought a new media console (thank you HomeGoods, I really didn’t want to build another entertainment center). Of course after all this I took the opportunity to re-build an old pair pair of 2-way speakers and build a new center channel for the home theater to complement the new family room (thank you Parts Express). And that’s about where everything sat for over a year. It had everything we could have wanted but it lacked one vital thing…a subwoofer. So this past month I decided it was time to break out the power tools and start making some saw dust and built a killer new subwoofer for our family room theater. Now that it’s done I can finally say the room is officially complete! Man I can’t believe I went so long without having crazy bumping bass. Movies, games and music all sound so much better now, the bass is massive, it absolutely rattles the entire house. But before we get into that, let’s get down to the design, the build process, show off some pics, talk about my cool miniDSP enclosure, how I setup the miniDSP as well as how I made a neat little relay box to remote trigger the Crown amp to turn on and off with my receiver. So hunker down and read on below!

So the gist of the setup is this: a single Dayton Audio Ultimax UM15-22 subwoofer in a sealed 2.82 cu.ft. (80 liter) enclosure powered by a Crown XLS 1002 power amp and PEQ’d with a miniDSP 2×4 in a custom aluminum enclosure. Also I built a relay trigger for the Crown amp so that it goes into standby mode anytime the system is not use. This is a great setup for a small family room theater without being too over-the-top. Though it might pale in comparison to what some people have in their theaters, especially when it comes to the Ultimax series of subwoofers, for my modest little setup, it is just right. And quite frankly puts out way more rumble than should be possible for what is basically just a thousand watt 19.5″ cube. I’ll go through each of these parts of this project, explain some of the design choices I made, show a bunch of pics, and hopefully you find some of this useful if you want to build something like this for your home/family room theater.

The start of this project begins with probably one of the most important things – designing the subwoofer and picking out the drivers. I probably tossed around a hundred different ideas over the past year before really starting to commit to something I was going to follow through with. But at one point nothing was off the table, from doing a massive IB in the attic, to just a simple 8″ sub, to multiple sealed subs or just one massive ported sub to a smaller sub with passive radiators. Parts Express has such a great selection that it’s really hard to narrow down what you really want vs. what you really need vs. what you can really afford. Not to mention deciding how much time you want to spend building and integrating this thing into your home theater. All factors which can be very different for everybody, which is why to me there is no one-size-fits-all solution when it comes to subwoofer solutions. Which quite frankly is true for a lot of speakers or just audio gear in general. Here’s ultimately why I landed on the design that you see here today. And it’s based a lot on compromise, trading one design goal for another, putting a bit more emphasis on one factor than another, thus tipping the design in one direction when someone else might go another way. As you read on you will see that for me the major trade off was giving up some low-end SPL for a simple, small, compact enclosure.

I opened up my copy of Unibox 4.08 enclosure modeling software and entered in the T/S parameters for the last few Ultimax and Reference Series drivers that I was missing. Now I was able to compare everything from a single 8″ Ultimax to quad 18″ Reference Series drivers and everything in between. I realize that PE carries other subs and other websites carry other drivers, but truth be told, and let’s be honest, I am a Parts Express fan to the core. So I didn’t do a lot of shopping around on this front. And Dayton Audio make for such a great value proposition, you really can’t go wrong. Anyway, I swear I can spend hours playing around with driver combinations in Unibox, just comparing frequency response graphs of different size enclosures and comparing sealed to ported to PR designs. Seeing which ones have the best low-frequency extension, which designs exceed Xmax too soon, which ones need huge ports to maintain low air speed, which ones aren’t flat or need huge boxes, etc., etc. Everyone has their technique, and I look at a lot of factors when it comes to any notional design at this stage. Cost is always a concern as well, something Unibox can’t predict. I mean sure, I can simulate four 18″ Ultimaxes in 20 cubic foot enclosures all day long and then ooh and ahh at the crazy 14 Hz tune and an SPL approaching 130 dB at 15 Hz. But then I start to look at what that physically might look like in our family room and how much that type of setup might actually cost and I have to ask myself, is it really worth it? Well, duh, of course it would be worth it! But we’re going to choose to go another way with the objective of this build to keeping the cost to something fairly reasonable and that the sub be as inconspicuous as possible, something that fits the room and doesn’t take up a ton of space but can still hit 20-30 Hz with enough energy to shake and rattle the house.

What is a little more nuanced with the Daytons is differentiating between the Reference Series and Ultimax series drivers. They sort of each have their niche and they model completely differently. Ultimax tends to favor larger ported enclosures and needs a lot of power, but ultimately can hit louder and lower than the Reference Series without exceeding Xmax. Reference on the other hand is more efficient, it can do more with the power you do provide, doesn’t require nearly the same volume enclosure to still have great extension, but Xmax can easily be exceeded since they just don’t have quite the same excursion that Ultimax does. It can be a toss-up though and you really have to just look at the frequency response plots, the excursion plots and the box volumes for each and see if it’s something you want to do. Comparing difference designs is pretty easy especially across just two different driver families, if you just stick with one box type, but once you start comparing sealed to ported, to PR designs across different driver series, it can be a little tough to decide. Is it worth making the box just a little bit bigger to gain another 1-2 dB at 20 Hz? The excursion sims are starting to look a little scary, what if I am really easy on the volume knob, hey more power never hurt anyone as long as I am careful it should be fine, right? Whatever you have to tell yourself so that you can get to a design that you’re comfortable and happy with. But most importantly, it should be a design that you’re excited about building. A design so awesome that you can’t sleep the night before you start it because you’re just that excited to work on it. If building a plain-Jane ported 12″ box doesn’t seem like fun, even if the simulations say it will sound great, then don’t build it.

So for me to narrow down the process, I made the executive decision to just go sealed, because everything I modeled ported required a box that was just way bigger than what I wanted to do for this room. And if you really pay attention to port air speed to minimize port chuffing, port area need to be pretty big, which means the ports need to be long for proper tuning, which means the box needs to be that much bigger to account for the added port volume. Passive radiators do fix this problem (at a cost) and I almost bit the bullet on a single 12″ Reference driver with a matching pair of 12″ PRs. It basically checked all the boxes for my design, the box size was reasonable, the low-end extension was good and the cost was right on budget. I had everything in my cart, ready to check out and then at the last minute I backed out. I don’t recall my exact reasons, it would have been a perfectly fine subwoofer, but I think I was just a little bummed that I had settled on just a single 12″ driver. It just didn’t feel big enough. And for the same cost or even less, I realized I could go with a bigger driver in the same size box if I just committed to a sealed design. (Probably spending too much time on AVSForum didn’t help matters). That’s when I turned to Ultimax and realized that these drivers model fantastic in small sealed boxes. Extension rolls off as any 2nd order sealed driver would but you can still hit a decent f3 in enclosures that are not huge. And if you’re willing to compromise a bit on the system Qtc, then you can make the box even smaller, keeping Xmax even more in check without giving up too much on low-end extension. Not to mention the rugged glass fiber woven cone seemed like it would be a bit more durable than the softer aluminum cone of the RS series. Plus, I really think these drivers look awesome. That massively fat high-roll rubber surround, the omission of any sort of dust cap and that sweet-looking woven cone, a cast basket, leads stitched into the spider, plus the dual 2-ohm coils means more flexibility with amplifier options. So this was it, we were going Ultimax. And since I wasn’t too keen on just the 12″ it was really deciding between the 15″ and the 18″.

After modeling the UM15-22 and UM18-22 in various enclosures sizes, I ended up deciding to go with the 15″ as it didn’t require quite as big a box as the 18″ and with the money I saved I put towards a miniDSP. I figured if you had a $300 budget for just the driver, then the 15″ and a miniDSP would be more flexible and could possibly sound better than an 18″ without any DSP. And I realize the volume requirements are not that much different between the two subs, arguably I was splitting hairs a wee bit. The 18″ models fine in only 4 cubes but the 15″ works in a little as 3 cubes (it’s roughly the difference between an 18″ cube and a 20″ cube after bracing with 3/4″ MDF) if you’re willing to put up with a Qtc in the high 0.8’s. I ended up making my box only a 19.5″ cube which is 2.82 cu. ft. after bracing, driver, a double-thick front baffle and 1/4″ MDF finish) for a final Qtc of 0.88 (walls lined). Most people would probably just buy the 18″ and call it day, make the box as big as needed, and then end up buying the miniDSP (or equivalent) anyway. But I was really trying to keep the box under a 20″ cube and the budget wasn’t something I wanted to stretch any more (at least any more than I already had). However that 18″ can do another +2.5 dB over the 15″ at 20 Hz for only an extra 28 liters and at 5 cu. ft it will do +3.5 dB, which isn’t insignificant. But I can say that I am more than happy with just the 15″ so far. It absolutely bumps and shakes my whole house like nobody’s business. I don’t think you can go wrong with either driver. Also the 15″ on paper was a better match for the Crown XLS 1002 that would be driving it. I think the 18″ would have wanted more power. But going back to why I abandoned the 12″ PR design, I figured that the 15″ Ultimax also gave me a better upgrade path to either dual sealed 15’s or just building a 12 cu.ft. ported box down the road for just the cost of a couple sheets of MDF (which by comparison would be +10 dB at 20 Hz compared to the sealed enclosure that is one fourth that size, definitely not insignificant). So into the cart went the UM15-22 along with a miniDSP kit, a pair of terminal cups and some rubber feet. Done, let’s move on…

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How to Build a Rockin’ Outdoor Speaker Setup with Sump Pump Subwoofer

Posted on June 6, 2020 by Dan

At long last, here is the complete write-up on how I installed a killer outdoor speaker setup, complete with 12″ subwoofer, using mostly gear from Craigslist, Amazon, Crutchfield and The Home Depot. I’ll go into how I designed this outdoor speaker setup as well as how I ran the speaker wire, mounted the speakers, built the subwoofer and my preferred method for playing wireless/streaming audio on a budget. If you’re about to tackle a similar project, then read on! Hopefully some of the methods I used here are helpful to you or at the very least will get you thinking about different ways to take on your own outdoor speaker/subwoofer project.

First off, let’s just get right into the specs and the audio gear used in this setup:

Speakers
Polk Audio Atrium5 2-way 5″ Woofer with 3/4″ Dome Tweeter Outdoor Speakers
AudioPulse Epic 12″ Aluminum Cone Subwoofer in a Sealed Sump Pump Basin Enclosure

Audio
Russound R235LS 2-Channel Single Zone Amplifier (2×50 watts into 4 ohms to sub)
Russound DPA1.2 2-Channel Single Zone Amplifier (2×35 watts into 8 ohms to Polks)
Optimus 12-2011 3-way Active Crossover set at 90 Hz

Wireless
Apple Airport Express with iOS or iTunes on PC

Miscellaneous
500 feet 16 gauge 2-conductor speaker wire (direct burial rated) pure copper
100 feet 3/4″ Schedule 40 Conduit and PVC pipe
Various Elbow and T-fittings for conduit and PVC pipe
(4) 1″ Conduit Clamps
SpeakON 4-Pole Connectors for subwoofer
4-speaker Binding Post Wall Plate
(2) Single Gang Low Voltage Retro Boxes (the orange ones)
1/8″ to RCA cable and (2) RCA-RCA Cables
12 Vdc 1A wallwart AC-DC adapter (for the crossover)

The Polk Audio Atrium5 Outdoor Speakers

So let’s talk about the speakers. I don’t buy many commercial speakers, since I enjoy building speakers more (isn’t that obvious?) but I have to make exceptions when it comes to certain types of speakers, like computer speakers, in-ceiling speakers and certainly outdoor speakers. I could have whipped up a 2-way speaker design using some nice poly or aluminum-cone drivers from Parts Express and attempted to build some kind of waterproof enclosure but realistically it seemed faster, easier and simpler just to buy a pair of finished outdoor speakers and save me the time and hassle. Man I’ve gotten lazy in my old age. After I received a gift card from work to Crutchfield for $100 it sort of sealed my fate and ended up buying a pair of Polk Audio Atrium5 outdoor speakers on sale for $169. Why the Polks you might ask? Besides the 5-stars reviews from just about every major retailer who sells these speakers, I’ve been a fan of Polk Audio speakers ever since I was little kid and went to my first real stereo store sometime in the late 80’s. I must have been 12 or 13 years old at the time but I still remember walking into this little store in a strip mall right next to the Miller’s Outpost (tell me you didn’t buy all your clothes from Millers Outpost?) that literally only carried high-end audio gear (this was no Circuit City) and that’s when I saw them, this massive pair of Polk Audio speakers, with a driver array as tall as I was, multiple woofers, of bank of rectangular dome tweeters and a huge 15″ flat subwoofer (that I would later learn was a passive radiator) right there in the middle of the showroom floor. These speakers were like nothing I had ever seen before and I was completely taken back by the shear visual appearance of them towering over every other speaker in the store. I have no idea what they sounded like, we never auditioned them that day, my dad was in the market for a pair of speakers I’m sure, but nothing like what those Polks had to offer. Of course the speakers I saw were none other than the SDA Stereo Dimensional Array line of speakers, what would now be considered Vintage Polk or Classic Polk Audio, the speakers that basically put Polk Audio on the map. I guess I’ve just respected Polk Audio as commercial speaker brand ever since, even if I never owned a pair of those speakers. Even today I don’t actually own any Polk Audio speakers (except for a CS1 center channel that I use in my garage theater and now these Atrium5’s), still whenever I see some Polk Audio speakers on Craigslist I’m always tempted to pick up a pair to play around with. So the Atrium5’s are basically the first pair of Polk Audio speakers I’ve ever really owned. And let’s just say, I am not disappointed. Though 12-year old me would be just a little bit disappointed I didn’t get something flashier. And outdoor speakers? C’mon man!

Anyway, sorry for the diversion, back to the Atrium5’s. After several weeks of very casual listening, I can easily say that these speakers sound awesome, have great treble, clear midrange and decent bass (though they do sound much fuller when supplemented with a subwoofer). You could do without the subwoofer but realize the practical limitation of a 5″ woofer in a small sealed enclosure. I measured the speakers using REW in my house before installing them outside and was pleasantly surprised by the nice flat response from these speakers. Check out the frequency response plots below. There’s a little boost in the treble to keep music sounding bright with a subtle drop in the midrange to prevent overemphasis of vocals. Bass down to about 70 Hz before it starts to roll-off. The enclosure is solid, the 5″ polycone woofer should withstand the elements and you get a legit 3/4″ aluminum dome tweeter. The plethora of 5-star reviews is enough to sell just about anyone on these speakers and after measuring them and listening to them for a few weeks now, I definitely agree with the reviews, these are a great-sounding pair of speakers that will do justice for almost any outdoor setup. A 5-year warranty has you covered for half a decade, so here’s to hoping they withstand the harsh sun of the Arizona desert. I didn’t install them underneath my roof/eaves like they recommend, but I did put them underneath some oleanders which should keep most of the direct sun off of them. They’ll take the full brunt of any rains/monsoons however, so hopefully they can withstand a little water. For now though I give the speakers 5 big stars to add to all the others. I couldn’t have built a better pair of speakers for the price. And certainly not as fast as clicking Complete Order and having them show up on my doorstep 3 days later. I could get used to this whole ‘buying finished/commercial speakers’ thing.

Apple Airport Express and Russound Amplifiers

So let’s move on to how I wired these things up to my whole house audio system. I currently have a 5 zones in my house that use discontinued Apple Airport Express units as the main streaming devices. I think a lot of people forget that these aren’t just wi-fi extenders but actually streaming audio playback devices. This is my go-to setup for whole house audio. They are small, wireless (or wired) and are basically plug and play. Apple Airports work flawlessly with iOS and iTunes. You can pick and choose your zones in iTunes and play music to any single or multiple zones with independent volume control on each. Timing is synced up for all zones so you don’t have the echo/delay effect which can happen when the timing of the music across zones is out of sync. In iOS on your phone you can only select one zone, but that rarely causes too many issues with the wife/kids using their phones as most of the time they only want to play music to one zone at a time anyway. Still you can use iTunes and the Remote App within iOS to control music in your library and play to multiple zones while controlling the music with your phone. You just can’t play music on your phone to more than one zone (or more than one Apple Airport) for some reason. But frankly this setup works great, sounds great, is easy to hook up, is cheap ($20 is the average price for a used Airport Express) and is totally integrated for anyone living within the Apple ecosystem. A similar approach can be done with Amazon’s Echo Dot or Google’s Chromecast, depending on your evil empire of choice. Also, if you pick up Amoeba’s Airfoil software on PC you can stream anything playing on your computer including YouTube, Spotify, Amazon Music, whatever your favorite streaming platform. The Apple Airports just look like an available device and it plays to them like any speaker. Airfoil has worked great for me over the years. The software isn’t free but is definitely worth getting. So we’ll add one Apple Airport Express to create one more zone and we’ll call it “Pool”.

Now that we have a way to get music wirelessly from our phone or computer to something all the way at the other end of the house, the next trick is amplifying that music and then getting it all the way into the backyard and to our speakers. The cheapest way to do this by far is to buy a cheap stereo receiver locally. You can easily find an old Sony or Denon unit for $20-$30 and they have plenty of power for driving a pair of outdoor speakers to levels your neighbors will certainly not appreciate. The only downside, they are big, they are bulky and for the most part you just need to leave it on all the time if you want music anytime. The second best approach is to pick up a small, class-D amp from Amazon brand new. SMSL, Topping and Lepai all make great little amps that can push about 25-50 watts/channel and these things are tiny, they draw very little current and can be placed just about anywhere. Downside again is that they also need to be left powered on all the time. Not as big of a deal as the bulky old receiver because these things are small and don’t draw a lot of current but not exactly an energy-friendly option. The best option, in my opinion, is to pick up an amplifier designed for use in a whole-house audio setup, something from brands like Russound, Niles or Dayton Audio, who specialize in special amplifiers designed for whole house audio distribution. I watched Craigslist and letgo for months before putting together this system and really just got super lucky and managed to find a pair of Russound amps locally from two different sellers. One guy had a brand new, in-box, Russound R235LS single-zone amplifier and he was only asking $20 for it. Another person was selling an older Russound DPA1.2 single-zone amplifier for only $30. I messaged them both and managed to pick them up the next day. So after spending a mere $50 I ended up with a near-matching pair of 2-channel Russound whole-house audio amplifiers to power the Atrium 5’s and the sub. Specs wise these amps can can drive 35 watts/channel into 8 ohms from 20-20,000 Hz at less than 0.05% THD. Both amps are bridgeable, have auto-on/off sensing, and have a 12 Vdc trigger in/out to drive other gear. Plus they are compact and beefy and weigh like 9 pounds a piece. I believe they are class A/B and not not class D although the product manuals do not specify either way. The weight alone makes me think at the very least they are not class D, so class A/B would be the next logical choice. They sound absolutely fantastic and the auto-sensing works perfectly. The amps stay plugged in all the time in standby and kick on as soon as the music starts. I have the trigger out on the one unit feeding the trigger in on the other, so only one unit actually triggers based on audio sensing while the other one just does what it’s told via the trigger. The setup so far works perfectly. So while just about anything can work for powering a pair of outdoor speakers, my recommendation is keep an eye out for anyone looking to get rid of whole-house audio style amplifiers and if nothing shows up in your town then hit up eBay or OfferUp. The auto-sensing and trigger in/outs alone will make it worth your while in the long run.

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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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