Tarkus

The Repository->DIY->Tarkus


Part of being a guy is liking big, loud speakers.  It's in the DNA or something.  Sure, we spend our nights and weekends building and listening to modest bookshelf speakers, but deep inside most guys want to build something bold and blaring.  It may be interesting to listen to pristine audiophile recordings on perfectly-engineered equipment--but honestly, is that really the type of music that makes up most guys' music collections?

I've seen lots and lots of talk on forums, people wanting to do a "skull-crushing" 3-way speaker; something akin to the Klipsch and Cerwin Vega "monkey coffins" of their wilder years.  I was up for the task, but if I was going to do such a speaker, I wanted to meet a few additional criteria besides just being big and loud. 

  • I wanted it to have an interesting look--something more than just a rectangular "monkey coffin."
  • I also wanted to make it as lightweight as possible--or at least be modular.
  • Most importantly, I had a sound in mind: I wanted them to walk the line between "refined and resolving" and "kick ass." 

Here's a link to the build log I did along the way, for when you have a lot of extra reading time.





Driver Selection

First up, I had to find a killer 10" woofer.  Without a great woofer, this speaker was meaningless.  I had to find one that could go deep and go loud, and it had to fit in a reasonable-sized box, and couldn't break the bank.  It just so happens that Peerless is just the company to deliver such a woofer!  Their SLS series woofers have the perfect tradeoff between sensitivity, power handling, and bass extension... most every other 8"-10" woofer out there in the sub-$150 range compromised too much one one of those three.  In a 62 liter box, the Peerless 830668 10" SLS gets an F3 of 29 Hz and can pump out 106 dB before excursion problems set in.  It also has a healthy sensitivity around 89 dB (which equates to a net 85-86 dB after baffle step losses and floor-bounce gain are factored in).  For the bargain price of $55, how can you beat that?  About the only thing to complain about this woofer is its stamped steel frame... the verdict is still out whether or not I can hear a steel frame, though. 


For the mid, I knew I wanted a paper cone, because they tend to be best at reproducing electric guitars.  (Why is this so?  Less odd-order harmonic distortion?  Smoother Frequency Response?  I don't honestly know why paper cones make more realistic-sounding guitars, but my best guess is that they tend to have cone breakup that is similar to that of a guitar speaker.)  I also knew I wanted a "large" mid, at least 6" in diameter--but, it had to have a fairly smooth Frequency Response so that I could cross to a tweeter at 2000 Hz or higher without problems.  For less than $50, pickins were slim.  I took a gamble on a Peerless 830657 6.5" midwoofer from their SDS series; and it turned out better than I expected.



Finally, as for the tweeter, I pretty much had it in mind that I was going to use the Vifa/Peerless DX25.  I'd used it recently in other designs, and learned its quirks.  It's not the easiest tweeter to work with, but once you get it right, it sounds great.  Also, for a dome tweeter, it can go extremely loud.  






Enclosure Design

When most people picture a loud, large speaker, they tend to think of a huge rectangular box--something shaped like a refrigerator, more or less.  I have a big problem with this type of speaker, though: it's too heavy!  Yes, I am a wimp, and I believe that most home audio speakers should be able to be moved by one person.  (I used to work in pro sound and pro video.  I did my time.)  As a workaround to the heavy-rectangular-box problem, I separated the woofer from the tweeter and mid.  To make this 2-part speaker more visually interesting, I started playing with using some angles on the cabs.  I borrowed a few design cues from Wilson and VonSchweikert--nothing too dramatic, though.  (After all, I was the one who was going to have to build it, and the tools in my garage are pretty basic.)  The Tarkus can be built without the angles, if one chooses.  The top cabinet would measure 13.25"H x 9"W x 11"D, and the bottom cabinet would measure 24.75"H x 13"W x 16.5"D.

The tweeter/mid enclosure is about 13 liters, sealed.  It is filled with polyfil.  The tweeter is flush-mounted, however the mid and woofer are both designed to be surface-mounted.

The woofer cabinet is 62 Liters, tuned to 30 Hz.  I used a 4" dia piece of SCH 40 PVC that was 13.5" inches long.  It just barely fits!  I think one could get the same results using a 3" flared precision port, 8.5" long.  The Woofer cabinet is lined with convoluted "eggcrate" foam, and does not have any stuffing or polyfil. The woofer cabinet will need a decent amount of bracing to tie the walls together, both from side-to-side and back-to-front.  The TM cabinet will probably only need one simple brace; perhaps a piece of scrap 3" wide, tying the side walls together.  Here are some graphs of the bass response, for those who like looking at graphs: Bass Frequency Response, Port Air Speed, and Cone Excursion.  



Crossover Design

The crossover is mostly 2nd order electrical filters and L-pads all-around.  The mid has a mild notch filter (C4+L3), centered around 4.5 KHz.  Note that the mid and tweeter are both connected with reverse polarity.











As you can see, the Frequency Response is generally very flat, however the Tarkus was intentionally voiced for rock music.  I mean, they are still capable of playing jazz or female vocal with finesse, but what they really like are guitars, electric bass, drums, cymbals, and synthesizers.  I have been playing these instruments for 15 years now; I know what a Marshall half-stack or an Ampeg or an overdriven Fender Bassman sounds like.  I wasn't happy with the design until it sounded like those amps were in the room with me.  




The impedance load of the Tarkus is generally safe for most amplifiers.  It does dip down to 5 Ohms a few times, but that's pretty normal, even for commercial speakers that call themselves "8 Ohm nominal."  It goes without saying, the Tarkus like some power behind them.  They will get to 106 dB @ 75 Watts, before xmax becomes an issue.  However, having an amp with more Wattage than that allows for some headroom, which is a good thing.















Here's a diagram of a suggested crossover layout.  You don't have to do it this way; the woofer cabinet is plenty big, and you can spread out the crossover in pretty much any way you'd like.  But this was my all-on-one-board solution (11" x 11" I think).  As you can see, the resistors are all doubled-up for increased power handling. 

















Also, because the top and bottom cabinet are separate, there is a need to somehow connect the two together.  There are several solutions to this, all of them fine.  You could use an outboard crossover; you could put the woofer filter in the woofer cabinet and the tweeter and mid filter in the top cabinet; you could put the whole crossover in the woofer cabinet, then connect the tweeter and mid separately.  In my case, since I mounted the whole crossover on a single board in the woofer cabinet, I needed some sort of connectors to go to the top cabinet.  I could have used Speakon, banana plugs, 1/4" jacks, the list goes on.  I kept it as simple as possible, and used spring-clip connectors and a few inches of speaker wire between the two cabinets. 












Here is a Bill of Materials for the Tarkus from Parts Express.  The drivers are all widely available throughout the US and internationally, so you shouldn't have much trouble procuring them.  You can also shop around for crossover components; use whatever brand suits you.  As long as the value is within 5-10%, you'll be fine. 


Finishing

Of course, if you DIY your own speakers, you can finish them any way you want.  I'm still a hack woodworker, and finishing is still a very new arena to me.  The finish I did on the Tarkus was definitely the best I've done yet, so I'm going to take a moment to show it off.

I built these speakers for my dad, for the "great room" at his vacation house.  He loves Stickley furniture, so that was the finish I went for.  I followed the mission oak instructions by Jeff Jewitt, for the most part.  Some products weren't locally available, so I winged it here and there.  But if memory serves me, it went something like this:

1.  Apply veneer: Paper-backed Quarter-sawn White Oak

2.  Stain: TransTint "medium brown" dye, mixed with water

3.  Seal: 2 coats Minwax gloss wipe-on polyurethane

4.  Glazing: Minwax "mahogany" gel stain

5.  Topcoat: Minwax semi-flat polyurethane

6.  Rub-out: steel wool and furniture wax

The results did look like Stickley!  My dad and I were both quite shocked when we set the speakers next to his Stickley "Morris" chair, and the finishes appeared to be "cut from the same cloth."






Final Thoughts

The Tarkus were designed to play loud, play clean, and to bring rock recordings to life.

Rant on: Unlike classical and acoustic music, Rock recordings are not meant to emulate a concert hall.  With rock, everything is close-mic'ed, sent through effects, and mixed at a console.  It's a studio sound, and it is what rock sounds like, and there should be no shame in that.  Furthermore, the production of rock music is part of the composition itself.  Consider for example the work of: George Martin (The Beatles), Brian Wilson (Beach Boys), Alan Parsons (Pink Floyd), Trent Reznor (Nine Inch Nails), Phil Spector, Ted Templeman (Van Halen), Terry Date (Pantera, Soundgarden), Mike Stone (Queen), Bob Rock (Metallica), David Bottrill (Tool, King Crimson), Rick Rubin, Andy Wallace (Nirvana, Jeff Buckley, Rage Against the Machine)....  The list practically never ends.

And it's not just rock music that is so heavily influenced by its production.  Other genres such as Country, Pop, R&B, and Hip Hop also rely on recording production as an integral part their sound, and the composition of the songs themselves.  In some ways, it boggles my mind that more speakers aren't designed with this in mind.  Rant off.

The Tarkus are indeed capable of producing the "pant-leg-shaking sensation" when cranked up past 100 dB.  However, at more conservative listening levels, say 80-90 dB, I have found myself very surprised to hear depth and resolve in rock recordings I never would have imagined were there.  Even at "quaint" levels of 70-80 dB, the Tarkus are still a lot of fun to listen to, and their ability to play low bass confidently still comes through.  In fact, I think the thing I enjoyed the most from this design was the ability it gave me to differentiate the kick drum from the electric bass, and hear them separately--not sort of "mashed together" as is the norm on smaller speakers.  (To explain further: kick drum is typically identified in a mix by the attack around 2-4 KHz.  This way, you can hear it on any old speaker.  What you typically do not hear on smaller speakers is the actual resonance of the kick drum, which is very low, anywhere from 100 Hz down to below 20 Hz, depending on the size of the drum and its tuning.  You can rarely pick this out on a normal speaker because it gets mixed up with the electric bass (or is removed altogether by the mix engineer).  The larger woofers in this design, however, let the two coexist, which I really enjoyed, being a drummer and all)

So enough talk.  Guys have been clamoring for something bold and loud, and this is my contribution.  Forget the Telarc, Mapleshade, and Sheffield Labs CDs--these speakers are for the rest of your collection!  (You know, the stuff you'd rather be listening to.)



Versions by other DIYers

The Tarkus design has inspired some really stunning builds.  Take a look.

The first person (to my knowledge) to tackle the Tarkus was [bolland83] from the Parts Express board.  In the style of good ol' rock n' roll, he did a faux sunburst finish that left a lasting impression on the PE board members.  His build threads are here and here.
 
 
 


[cowtown] of the Parts Express board had the idea to do the Tarkus in a 1-piece curved cabinet.  He took on many new challenges in the project, but the final result was a glowing success.  His build thread is here, which does a good job of explaining each step of the process.
   


This is a pair crafted by Dave G in cherry veneer.
 
 
 


Finally, this is a completely different speaker design, but it deserves some mention.  It was done by Parts Express employee mattp, who liked the looks of the Tarkus that he um... borrowed from it, liberally.  His design uses some exclusive, pricey HiVi drivers.  More info here
 
 
 


This build was done by Steve in a speaker-building frenzy of sorts.  (you may notice he built a pair of Overnight Sensation TM and MTM in the background).  The color and woodgrain is really striking.
 
  




by Paul Carmody | this page was last updated May 26, 2012

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