Classix III

Did you ever eat at a restaurant so upscale that the entrees took several sentences to describe, and contained ingredients so exotic that you wonder if they made them up? When they bring your food to you, it's perfectly centered on a giant plate, and the garnishes take up more space than the actual food. You eat your small dish, pay the exorbitant bill, and in the end you think to yourself, "Maybe I should have just gone out for a burrito?" The Classix are the audio equivalent of that burrito. Tasty, spicy, flavorful, filling... probably fattening, too. But so much fun!

Due to changes in the tweeter market, we are now at Version III of the Classix. The overall vibe and flavor of the Classix remains unchanged. As long as Dayton keeps making this woofer, the design can live on!

Drivers

Dayton DC160

The Classix series is designed around the Dayton DC160 6.5" woofer. It's pretty easy to tell that I have a penchant for this driver--you may also notice that audiophiles and engineer-types eschew the DC160. I think it's all a matter of looking at the driver objectively vs. subjectively. Objectively, it has a "simple motor design" and its harmonic distortion graphs aren't all that impressive. Subjectively, however, this driver is "euphonic"--meaning that most ears find it very enjoyable and pleasing to listen to, despite poor measurements. I believe that if a driver sounds really good, then it's a good candidate for a speaker design, regardless of how it measures.

Dayton TD25F-4

The TD25F is a newer offering from Dayton Audio. It features a 1" dome, and traditional large magnet and a flange that's just a bit smaller than the standard 4" diameter. It takes a bit of patience to get sounding great in a crossover, but I guess that's the tradeoff for its steal of a price.

Enclosure Design

The cabinet for the Classix III retains the same overall dimensions as the Classix II. I simply made an adjustment in the driver spacing on the front baffle, accounting for the smaller tweeter flange of the TD25F. It's a "medium-sized" bookshelf speaker, with an internal volume of around 15 Liters. It's tuned to 40 Hz, and uses a 2" vent that is 8" long. It reaches an F3 in the mid 30 Hz range with a great sense of ease. As you can see, there is a front-ported version and a rear-ported version. The two cabinets will perform identically; which one to choose is a matter of aesthetic taste.

The cabinet should probably be built with 3/4" MDF or plywood. A single brace ought to suffice to keep the panels of the cabinet from resonating. The internal walls of the cabinet should be lined with "eggcrate" convoluted foam, and one can add a handful or two of polyfil for additional damping, if desired.

Crossover Design

With this newest generation of the Classix crossover, I experimented with everything from a "clean slate" design to keeping the same basic topology and tweaking a few values. In the end, I did a sort of hybrid of those two.

The woofer filter has remained unchanged from the previous generation; honestly, this is as good as I'm gonna be able to get the DC160 to sound--and it does sound quite good. With the tweeter filter I was able to simplify things, and bring down the component count. The TD25F is fickle, though. The impedance spike is a doozy, and is audible unless you compensate for it somehow. In this case, using resistor R2 in parallel with the tweeter was able to flatten this spike; and from there, the rest of the filter came together.

The crossover point is just the slightest bit below 2 KHz. That's as high as you can push the DC160--there's literally nothing left after that. And even though we're working at the limits of both of these drivers, they actually integrate very naturally together.

Also, my graph shows a bit of a rise between 300 and 900 Hz. Please don't worry too much about this. It's just because of how I gated the measurements. The woofer filter is exactly the same as it's been in the last generations, remember? Whatever good things you've heard about the bass and midrange in the previous versions remains here.

The impedance load presented by the Classix III are an easy load for any amp to drive.

Listening Impressions

I know you'll think I'm kidding, but of all the speaker designs I've done, if I could only keep a handful, these would be near the top of my list. Why? Because not everything I listen to is all that well-recorded--and that's where the Classix really shine. For example: give them a grungy rock album and they will run with it. Hip Hop, R&B, Pop, Metal, Country--all stuff we spent so many hours of our lives listening to, developing emotional ties to--that music usually doesn't stand much of a chance on a true HiFi set of speakers. But as I said, the Classix have a "euphonic" quality about them. They gloss over many of the problematic details of popular music (that an "audiophile" speaker would glare at you with), but at the same time are engineered to be revealing enough that most people would be surprised to hear new things in favorite old recordings.

With this tweeter, I was able to lock in the treble to a higher degree than I ever have before. I don't think this is necessarily because the Dayton TD25 is a better tweeter than the ones in the previous versions, but rather simply because of the wisdom I've gained with age. In other words, I know what sound I like, and am just more skilled in homing in on it. The center image is tight, and there is still a nice sense of detail without becoming fatiguing.

The big highlight of the Classix family has always been the deep bass coming from such an unassuming bookshelf speaker cabinet. Perhaps one reason I'm so attached to this design family is that I wish so dearly I had it while I was living in apartments. During that time--the time before I knew what DIY was--I had to keep listening volumes pretty soft, and all I had to listen through was a dusty pair of old Cerwin Vegas. Kinda sad, really. I loved listening to music, but a sub was out of the question, and the Cerwin Vegas sort of sucked the life out of the music. If only I'd had something like these.

Honestly, despite the fact that these are generally "cheap" drivers, and no one's really expecting anything high fidelity from them, every time I listen to them, I'm genuinely surprised that something this cheap can sound this good. A few minutes into a good song, and I've completely forgotten that this woofer is so notorious for having no midrange.

In closing, I'd like to write a letter.

Dear Classix,

Thank you for bringing that music I used to love in high school and college back to life. Thank you also for making modern recordings listenable again. I look forward to many years of head bobbing and toe tapping (and possibly air drumming) together.

Sincerely,

Me.

Completed Versions by DIYers

This handsome pair was built by [DrDyna]. The finish is Parts Express vinyl. (Hmm. that speaker in the background looks familiar...)

Here's some inspiration for your next finish. This pair was done by [billiam] for his son's bedroom.

Here is a moody pair by Bastien

How about a pretty white pair by Freirik. Did I mention I love white speakers?

Tastefully done in Oak veneer by Scott. These had his family searching the room for the subwoofer.

by Paul Carmody | last updated November 10, 2024