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Project by knotscott posted 07-11-2009 08:00 AM 3137 views 1 time favorited 8 comments Add to Favorites Watch
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These were built several years ago, but I’m still really pleased with both the look and the sound. At the time I wasn’t into woodworking, so I designed the cabinets and had them built from MDF by a local cabinet maker, then hired the paint job…that’s faux wood on the sides and base.

This is a proprietary design that I developed over a period of 7 years (I’ve designed about 9 models, of which I built and sold a couple hundred pairs under the name of Sterling Acoustics…these are by far my favorite set). The basic cabinet is an 8’ folding transmission line for the 8” Focal kevlar long throw woofer, the 5-1/4” mid is also a Focal kevlar driver that’s in an aperiodic chamber that vents into the T-line. The tweeter is a dual chamber Seas aluminum dome. The crossover is passive, using some unique poly capacitors that are made specifically for Convergent Audio Technology’s “CAT” preamps and amplifiers. The inductors are heptalitz air core, and the internal wire is Kimber Kable. Each driver has it’s own input terminal… the drivers are currently tri-wired with some very average basic OFC 14 awg speaker wire but were wired with Kimber Kable once upon a time at our other house….they can also be tri-amped. For a number of years now they’ve been hooked up to a Lazarus Cascade Basic tube preamp, and a pair of modified Dynaco Stereo 70 tube amps that were converted into triode mono blocks. At only 17 watts per channel (less than 1/10th the power output of some of my other amps…Hafler DH500 255wpc, NYAL Moscode 300 150wpc, Distech LS-2 @ 105 wpc), they’re the sweetest sounding amps I’ve owned. Ironically, about the time my “poor man’s” highend system was really coming together and sounded amazing, we were at the stage in our lives when the primary music in the house was Alvin and the Chip Monks, Raffi, and the Muppets! Now that the kids are bigger, I’m 49 and I’m certain my high frequency hearing is no where near as sensitive as when I built these. The system now sits largely neglected and is no longer optimized for the room, and gets used mainly for Christmas music, but was once a very nice sounding setup with these speakers…the potential is still there, but I suppose I lack the motivation or desire to do anything about it right now.

-- Happiness is like wetting your pants...everyone can see it, but only you can feel the warmth....

8 comments so far

View Todd A. Clippinger's profile

Todd A. Clippinger

8901 posts in 4128 days

#1 posted 07-11-2009 08:21 AM

That is a sweet design.

I had thought about making my own speakers sometime.

-- Todd A. Clippinger, Montana,

View Durnik150's profile


647 posts in 3350 days

#2 posted 07-11-2009 09:56 AM

Excellent! If you need anywhere to field test them ij their home, left me know.

-- Behind the Bark is a lot of Heartwood----Charles, Centennial, CO

View Chris Davis's profile

Chris Davis

1560 posts in 4011 days

#3 posted 07-11-2009 12:16 PM

I never knew speakers were so complicated. I’d love to see the inside and how all that is wired. Great Job!

-- Watch live video from our shop.!current-projects/c3c1

View CharlieM1958's profile


16275 posts in 4247 days

#4 posted 07-11-2009 03:25 PM

Really cool looking, and I’m sure they must sound great.

-- Charlie M. "Woodworking - patience = firewood"

View a1Jim's profile


117127 posts in 3606 days

#5 posted 07-11-2009 04:43 PM

Interesting and unique design well done Scott

-- wood crafting & woodworking classes

View PurpLev's profile


8536 posts in 3677 days

#6 posted 07-12-2009 04:01 AM

focal? going straight to the top huh? looks great. Interesting to see that it’s made of MDF, and the resonance is good. I made mine from Birch Plywood with B&W speakers, and in terms of sound – there’s a lot to be desired. I was thinking about a remake from solid wood, but maybe I’ll give MDF a try first.

Thanks for the info. good read!

-- ㊍ When in doubt - There is no doubt - Go the safer route.

View cabinetmaster's profile


10874 posts in 3587 days

#7 posted 07-12-2009 04:06 AM

I have made a few speaker boxes for some friends and they always ask me to use MDF. Now I know why. Thanks for the post and those speakers look fantastic.

-- Jerry--A man can never have enough tools or clamps

View knotscott's profile


8057 posts in 3404 days

#8 posted 07-12-2009 02:19 PM

Thanks for the comments gang.

Purp Lev – MDF is inert and more acoustically neutral than ply and hard woods. The resonance is really achieve by the box design, and should be controlled and minimized as much as possible for home speakers….the T-line eliminates the resonance, while most other designs “control” it to a specific frequency.

Home music reproduction has very different goals than live music production. There’s a lot of confusion caused by those differences when the advice is treated as generic without being applied to the specific discipline. Pine and ply are excellent for guitar and instrument speakers, but add too much color and warmth to a typical home hi-fi setup….it’s always a matter of what someone likes, but the term “Hi-Fi” stands for high fidelity, or faithful reproduction of the original, which means as little coloration or change as possible….warts and all…transparency and neutrality are desirable if that’s the goal. Different objectives than a musician would have.

There are some other basic generic tricks that you might consider…the box is only one of the main components…drivers and crossovers are the other two. Since they should be proprietary, it’s probably best to trust B&W’s approach and recreate their original design as closely as possible, but it might be worth upgrading any electrolytic caps to a decent poly cap of the same value. If there wire is subpar, replace that too with some decent OFC speaker wire….brand name isn’t critical, but design and gauge matter. It’s also very important to get the tweeter and midbass drivers as phyically close together as possible to avoid phase shift…the idea is to produce a single music wave from two drivers, so you have to get the centers of the drivers within the distance of the wavelength of the crossover frequency between them…most tweeters crossover in the 2k to 3kz range, making it very difficult to get them that close. (a 1kz frequency has a wavelength of about 12”, 2kz ~ 6”, etc.). Ok…too much coffee! ...good luck!

-- Happiness is like wetting your pants...everyone can see it, but only you can feel the warmth....

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