Extreme Makeover: Bookshelf Speaker Edition

I finally finished a new pair of 2-way bookshelf speakers for my home theater, a project that started over two years ago. It was back in March of 2006 that I bought a pair of Dayton RS-150S-8 6″ Reference Series woofers and RS-28A-4 tweeters. The plan was to refinish an old pair of speakers that had some old MCM speakers in them that weren’t worth the time I spent on the nice enclosures that housed them. They never sounded very good, and the tweeters somehow got completely destroyed, in spite of the plastic shield that was suppose to protect them. So I picked the new speakers to drop in to the old cabinets in hopes of doing it with little modifications.

Then the summer passed and I never got to them, winter came and went, then last summer came and went and the speakers still sat in their original boxes. I at least had plenty of time to stew over the crossover, which I would do from time to time, tweaking and modifying each value until I finally came up with something that looked really good and used a minimal amount of components. After settling on a crossover design and having the boxes pretty much complete and getting ready to make this speaker happen, wouldn’t you know that Parts Express showcased a brand new two-way speaker in their projects section designed by none other than speaker guru Darren Kuzma, which used the exact two drivers I had sitting on my shelf. And they called it Encore.

I read through his whole design and was happy to read that he was very pleased with how the speakers sounded. I compared my crossover design to his and modeled both using PCD and compared the two plots. The FR plots looked nothing alike, not surprising since the designs were very different. I don’t claim to be a great crossover designer by any means, I just don’t have some of the better tools and software to model them up properly, so it’s a lot of trial and error for me. I considered buying the parts for his crossover and mine and comparing them to see which one I liked better. Then when it came down to actually buying the parts, I ended up just buying all the crossover parts for the Encores, since it was cheaper than trying to buy both, it accounted for baffle step compensation (mine didn’t) and it’s basically a proven design, even if only in one other speaker system. So what was once going to be a killer two-way speaker that I designed, turned into just a remake of these great Encore speakers. Which is fine with me, it’s only a slight hit to my speaker-building ego. They look great, though my typical paint job is pretty lousy. I think black paint is the hardest color to paint. Fortunately they sound a lot better than look. (Except for the drivers, they alone do look amazing).

I do plan to change up the box a bit and do a 4th order vented enclosure as soon as I get around to buying some new ports from PE. The total net volume is about 8L which is a bit small for a ported box and this 6″ driver, but it models well, slight 2 dB hump, and should give me some extra extension over the same volume sealed box. But for now, they are sealed and filled 100% with poly-fil. They certainly need a sub to hit any of the low notes at all. But the bass isn’t bad considering their size.

The match to my center channel is just a little bit off. I want to redo the crossover in my center channel, it’s a bit too bright for the mains. The last time I did a sweep on the center channel with REW, the response was somewhat erratic and showed a gradual rise from just a few hundred Hz up to 20 kHz. I would like to rebuild the center with the same drivers, but part of me just hates to tear apart a perfectly good speaker, just for the sonic aesthetics of having the exact same sound coming from the three front speakers. They sound close enough now, and with a slight tweak on the center’s crossover, I think I can get them to all sound similar enough to be satisfying. We watched a movie last night and my wife thought everything sounded great. Which I don’t disagree, the whole setup does sound great, but the match to the center needs to be better. Today I popped on a little Harry Connick Jr. for just some 2-channel listening and was completely blown away. The detail and clarity were astonishing. Harry’s voice sounded deep and rich, the piano sounded true, the high-hat was crisp, the sax so breathy and the big band brass just filled the living room. I couldn’t believe such impressive and filling sound could come from such little speakers. I am ecstatic with their performance.

Check out some of the pictures below to see just how I took an old pair of bookshelf speakers and made them brand new again. Just wanted to say thanks to Darren for the great crossover design! The speakers sound awesome. And thanks to Parts Express for their exceptional products and continued support for the DIY community. I definitely recommend this speaker project to anyone looking for a great HT/music bookshelf speaker that offers exceptional sound in a compact and affordable package.

In addition to everything from the Encore’s Part’s List (minus the cabinets) here’s what else I bought:

095-280 – 1/4″ (16-14) Female Disconnect 50 Pcs.
081-440 – #6 x 1″ Deep Thread Pan Head Screws Black (for tweeters)
081-425 – #8 x 1″ Deep Thread Pan Head Screws Black (for woofers)
100-020 – Dayton SKRL-14-50 14 AWG OFC Speaker Wire
260-311 – Gold Speaker Cup Terminal Round
Black Suede Behr Indoor Paint in Semi-gloss from Home Depot
100% Polyester Fill from JoAnne’s

Click on the thumbnails below for full-res pictures of the complete makeover. (Parts Express has removed Darren’s project and I can’t seem to find it any where)

10/30/2009 Update – Alternative Crossover Options – No Baffle Step

So it’s been about a year since I finished these speakers and after listening to countless CDs and watching a bunch of movies, I decided that, although these speakers sound great, they were a little too laid back for my liking. The highs were a little too soft, too muted, too mellow. I like something a little brighter, with a little more presence in the upper region. I figured this is due mostly to the full baffle step compensation in the crossover compounded with the fact that these are sitting on a bookshelf where the full baffle step is mostly already taken care of, so the need for compensation just wasn’t there in my application. It gave the speakers too much low end. Problem is I’ve got a subwoofer with this setup so having more low end from a 6″ woofer in when you’ve already got a 12″ woofer just made for a muggy, tonally imbalanced sound. I could never get the guitars and the symbols of the drums to have enough volume, enough crash, enough dynamic. Everything else drown it out. I compensated with EQ over the year, but it was time to fix it for good.

I modeled the crossover in PCD (Passive Crossover Designer) and by keeping the exact same components, or by adding very little, I wanted to see if I could remove the baffle step and increase the level to the tweeter, without having to buy a bunch of new parts, and this is what I came up with. I bypassed both shunt inductors on the woofer, so I end up with a very basic 2nd order 12 dB/octave low pass with a Zobel network following it. Nothing fancy, and no more baffle step. Now to bring the level of tweeter back up I dropped the 4 ohm resistor to a 2 ohm resistor and removed the 8.2uF cap again making it a simple 2nd order filter. These new values modeled up very nicely and gave me a nice flat response over the entire band of the speaker.

I changed the crossover in just one speakers and did an AB comparison of the old and new crossover and gave both a good listen. The crossover did exactly what I was hoping, it brought the high-end out of the dark ages and into my living room. The original crossover sounded like there was a pillow in front of the speaker compared to the new crossover. Vocals sounded cleaner and more intelligible and music overall had more presence, more sound, more highs, and just sounded, to me, much better. Acoustically they just sound “flatter” to me now. I suppose it was my own fault for adding full baffle step to a speaker and then putting it into a bookcase and adding a sub.

I measured the new response with Room EQ Wizard and my ECM8000 instrument mic and they have a very nice flat response when measured in my listening room while doing both near-field and far-field measurements. So I’m pretty happy with the new sound. We watched Transformers II the other night, right after I finished putting them all back together, and the movie sounded awesome. That movie has a great LFE track, too much bass to even handle. My whole house was just shaking the whole time. But the effects coming out of these speakers is much more pronounced and more believable. You actually feel like your there just a little bit more than before. Not to mention playing music sounds better too, just a bit more high end and less bass from such a small speaker.

I’ll add some plots and a schematic of the new crossover as soon as I get a chance…

11/27/2020 Update – Crossover Option #3 and Ported – Turning them into a Passive Studio Monitor

All right, this is finally it, these speakers went through one final makeover and have found a new home as my main monitors for my small recording studio/setup. I updated two elements to this speaker in this final makeover: I ported them and tweaked the crossover for a flatter near-field response. Both of these changes have completely opened up these speakers and now I can say they sound the best they ever have. But before I go into that, let’s start with the biggest question you may have, can you really build a pair of DIY speakers and use them for studio monitoring? Well, of course you can! But there are a few things to consider when doing so, one of the main ones being you have be able to measure the frequency response of the speakers in your room. There is no guess work here. Without measurement tools, you have no way to know if the speakers are artificially boosting bass or lacking highs. Your mix will be a function of what you hear in these speakers, for good or for bad. The design should try and create a sound that is flat and neutral, a sound that doesn’t attempt to add or take away anything from your mix. Ideally also taking into consideration the location of the speakers in your room, distance to the back/side walls and the floor. So being able to measure the speakers is absolutely key to getting a DIY speaker to even stand a chance of being used as a studio monitor. And even then, probably only for casual playing/recording/mixing and not for professional use. And since I’m no professional, these speakers work great in my little studio and have enjoyed them over the last year. In fact, a friend and I threw an EP of cover songs last year and these speakers were used exclusively for all my recording and mixing. Check it out over on Soundcloud under DMKR Music if you want to give it a listen.

Anyway, let’s get back to this build. A couple of weeks before starting on this project I was at Guitar Center and decided to pop in and listen to some of their studio monitors. I’d read so many articles and watched countless YouTube videos of reviews for various types of affordable studio monitors recently so it was fun to actually get to listen to some of them in person. My Guitar Center has a decent selection of standard two-way powered 5″ to 8″ studio monitors including JBL, Yamaha, KRK, Mackie, M-Audio and Adam Audio. I gave them all a good listen thinking maybe I would outfit my modest little studio with a pair of actual studio monitors instead of these home-brewed speakers I’d been using for the last year. They all sounded really good and I was very tempted to pick up a pair since most of them were on sale. And if I had to pick a pair of speakers that day based on my limited listening, it would have been the Adam Audio T7V’s. These speakers sounded better, smoother, cleaner than everything else on display. Treble was airy, bass was tight, vocals were clear, they just sounded awesome. Second to those I would have picked the JBL 306P MkII’s only because while they didn’t sound quite as good, they were much cheaper, on a budget the JBL’s would have been a better value, but realistically no other monitor on display could beat those T7V’s. In fact, I may still pick up a pair later down the road. Which sort of brings me to this genesis of this speaker makeover project.

After being impressed by the T7V’s, I stopped by adam-audio.com and spent some time researching these guys, just trying to figure out what makes them different, what makes their speakers sound so good. Never mind the fact that the T5V/T7V’s are considered to be their budget-friendly line, Adam Audio make some very nice, much more expensive studio monitors that can be found in professional studios all over the world. I was impressed to find was frequency response plots of most of their speakers right there on their site too. Sure enough if you look at the FR plots of the T7V they are nice and flat, have good extension all the way down to 40 Hz, and lack any any serious response peaks or dips. That’s when it hit me, this would actually make a great target frequency response for my own speakers. So I started to come up with an idea. The plan was to tweak the crossover in my speakers just right in order to achieve a similar frequency response and then maybe I could mimic a similar sound with these old little bookshelf speakers and use them for my little recording studio. At least for the meantime. I make no claim that by just matching an FR plot to another speaker will make them sound the same, but at least from a tonality stand point, they should sound similar, such that if I’m creating a mix of a some song, at least the treble and bass levels will be somewhat close to what most people would argue are really nice pair of real studio monitors. And until I finally break down and just buy a pair of T7V’s I’m going to make due with an updated version of these home speakers I’ve had for the last 10 years. Also it should be noted that if I were starting from scratch, I think it would be possible to come much closer to matching a pair of T7Vs using select drivers from Parts Express including their exclusive AMT tweeter which is at a least the same technology as the tweeters Adam Audio favors, even if they are not exactly the same. But for now we are just going to do a quick makeover to these old speakers I’ve had for a while, since I don’t have much other use for them right now.

The first thing I knew I needed to do with these speakers was to vent the enclosure, changing it from a sealed 2nd order enclosure to a 4th order vented one. Very few if any studio monitors use a sealed design, they just don’t have as much bass. The Dayton Audio 6″ Reference Driver works well in small vented enclosures, but since the cabinet was left over from an older speaker originally, it wasn’t quite optimized for a ported enclosure with this driver. Still I made due, with about 8 liters to work with I ended up adding a pair of 1-3/8 by 5-3/4″ ports tuning the enclosure to about 65 Hz. It’s a bit high and has some peaking, but still sounds much better than when it was sealed. See the plots below which show the difference in bass compared to when they were sealed. To help combat some peaking around 90 Hz I doubled-up on the insulation and poly-fil to try and dampen the enclosure as much as possible and make the enclosure appear as large as possible for the 6″ woofer. And note that I stole the double port idea also from Adam Audio but this time from their AX series. I couldn’t fit the two ports below the woofer though, so I put them between the woofer and tweeter, but they have a similar visual aesthetic as the A7X, they just aren’t quite as big. So overall porting the enclosure made a huge difference in the sound of these speakers, now they’ve got some actual bass and while the extension could be better, considering their size, they’re little to complain about. Plus those dual ports on the front just make them look meaner, more aggressive, more like an actual studio monitor.

Now it was time to tackle the crossover, I knew I had some work to do here. As the original crossover had a full baffle step and then was later tweaked by me to “bring up the highs a little” when I put a mic in front of them again years later they looked a bit worse than I remember. There’s was this big suck-out from 1-3 kHz and then a big peak around 5 Khz and then they dropped off pretty quickly above about 9 kHz. And as previously noted with the sealed enclosure the bass below 100 Hz was non-existent. I wanted these things flatter and I with a target T7V response to shoot for, I had to fix a few things for sure. With a small selection of crossover parts on-hand (inductors, caps resistors), I didn’t want to completely re-do the existing crossover because there were some good parts in there already. And unfortunately a year later as I write this blog post, I cannot for the life of me find my notes where I wrote down the final crossover components. But I was able to adjust the frequency response just enough to get to something that was reasonable. Remember I don’t have active EQ going on here, I’m left with only passive elements, so getting a ruler flat response was not going to be possible. But I was hoping to get to something that resembled the response plots of the T7V. I converted the .png file from Adam Audio’s website into a text/data file (using FPGraphTracer.exe) and imported it into Room EQ Wizard and that’s how I was able to make direct comparisons to my speakers and adjust the crossover accordingly. The final result you can see here which compares these speakers to the flat setting on the T7Vs. Overall it’s not bad and the basic shape of the response is mimicked nicely. Bass and treble levels match and even the mid-bass dip (around 200 Hz) is present in both speakers. This is a critical spot in most speakers as it can make the difference between a great sounding speaker and a muggy one. I’ve found it’s better to attenuate this region rather than accentuate it but oddly enough it matches the T7V pretty good in this region which isn’t something I did intentionally here other than by adding just enough insulation to tame this area since the box volume is a little small. I can’t believe I don’t have the final crossover values, I knew I would lose that piece of paper, I don’t know why I didn’t take a picture of it at least. If I find it though, I will update this post.

And I think that’s about it. I took a couple of pictures of the makeover, but not nearly as much as I should have. Adding the ports was an interesting endeavor and I did have to repaint the front baffle, but overall was a pretty straight forward remake. These speakers are currently being powered by a small SMLS 50×2 class D amplifier. The amp doesn’t quite do the speakers justice and I’ve been on the lookout for a better amp to replace it, but for now it’s doing the job as long as I don’t try and reach ear-splitting levels. The amp definitely poops out before the speakers do. When I built my Ultimax sub I tested out that Crown XLS1002 amp on these and they seriously sounded amazing. I couldn’t believe what 215 watts per channel on tap could sound like to a small pair of bookshelf speakers. They took some serious power before I feared I would melt them, but wow they sounded good and they had no problem playing loud, with the right amp. So while this project wasn’t really intended on being a how-to make a studio monitor, these speakers are doing a decent job. Only now a year later I really want to design a new pair of specific-intended studio monitors with active amplification and DSP to really make for a world class professional studio, but until then, these will have to do! Thanks for reading.

Older Pictures

The old speakersOld speakers removedNew baffles cover the old cutoutsCutting the holesNew holes cutFit-check driversFlush-mount baffle board attachedEdges routeredHoles in the crossover boards for partsCrossovers completedSpeaker partsFoam gasket on RS-150SEncores completeEncores completeEnclore left side

Updated Pictures Final Monitors

About Dan

For a complete biography, stop by www.danmarx.org and click around for a while.
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