The System - Description and Photos

 
Speakers - I'll never buy speakers again after making my own - at this level I couldn't afford to! The speakers are the most important part of any system, and this is where the most time, research and money went. If you are contemplating buying or building a system, concentrate on the speakers and put most of your money there. Your ears will thank you.

Midrange and Highs
- are reproduced by Bohlender & Graebener Radia Series 75" planar magnetic drivers  in well braced, stuffed enclosures of 3/4" MDF  (the enclosures are not 'finished' yet - I made the mistake of setting them up for a trial listen!). I used to have them in bipole panels, but they really need a huge room for that configuration. The monopole boxes are more forgiving in placement, and better sounding in my humble opinion. These drivers can really take a beating; it's nice to be able to listen - no, to experience dynamics and transients that bring other tweeters to grief (like Crystal Method, or the gunfire in Forrest Gump, or the T. Rex splintering the trees on the Telarc Fantasy Adventure album). They have two (minor) faults; highs roll off off-axis, and the top end response begins rolling off near 16k. Believe me, you don't care when you're listening to them. The most common comments that I get is how effortless they are, how clean the highs are, and how good voices sound. They are crossed over at 300 hertz to

The Bass Section
 Dynaudio 24W-75 woofers (four per side) are mounted in sealed, heavily braced, stuffed 1" MDF enclosures, with separate volumes for each woofer. The Dynes are fast, precise, and are among the few woofers that can keep up with the Radias. Drums sound really good on these, and acoustic bass is well-defined. I heard that Dynaudio is no longer selling their drivers to the hobby market. If this is true, all I can say to Dynaudio is that it was a REALLY STUPID decision.  Here's a shot of one of the woofer enclosures during construction:
A well-braced woofer box
Separate terminals for each woofer are provided on the back of the enclosure so that various hookup combinations can be made; this has turned out to be a real blessing! Best results are obtained when each driver is on its own separate amp channel.  The front panel is 1-3/8" thick and is made of oak salvaged from a pipe yard. The wood was planed, cut into long square sections, laminated and beveled. The woofers cross over at 45 Hertz to

The 'Labyrinth' Subwoofers
18" drivers (brand no longer made/available, hope to change them out someday for other drivers) are mounted in two transmission line enclosures built of well braced 3/4" MDF. They are big, about the size of a refrigerator, not for impressing anyone, but because that's what it takes to do the job. These are true subwoofers which extend the system response down to a solid 12 Hertz. The Enya track 'Longships' has an awesome drum fundamental in this region which went unnoticed (thus unappreciated) until these subs were put in. It is amazing how much information there is below 32 Hertz on many recordings. Alphaville's 'Salvation' album is awesome. Massage, anyone? One of the fundamental resonances in my house is at 13 hertz which causes the windows to shake violently in their frames like an earthquake.  Low 20's gets various cabinet doors going. Bring on those pipe organs (and chills)! If someone tells you there's no useful musical energy below 30 or 40 Hertz, they just don't know.

The (right channel) mains:
B&G Radia 75 ribbon with Dynaudio 24W75s.
One of the two 18" transmission line subs. Yes, they're big. And heavy. 'I canna change the laws o' physics, Jim!'.
A true sub-woofer
 

Crossover - Marchand Electronics Model XM9L-3AA 24 dB/octave three-way. An active crossover was chosen because of the very low woofer/sub crossover point, and so that various frequencies could be tried (by changing resistor networks). This crossover is well-executed and extremely quiet. I highly recommend this company and their products. Early on, for fun, for a subwoofer crossover I actually tried a big iron core choke made from the primary and core of a neon sign transformer, with an 11uF capacitor. It did work, but it sure soaked up a lot of power!

Amplifiers - One Threshold S/500 stereo amp on the ribbons. They like current.
Two NAD 216 stereo amps on the woofers (gets by, need more power for dynamics, considering ATI).
Two Adcom GFA 565 monoblocks, one for each subwoofer.

Source - Radio Shack CD 6220 5-disc changer - I know, quit laughing, I'm looking for a better source! :-) Just can't do everything at once. And I'm waiting, impatiently, for the new 24/96 and 24/192 audio standards to come out in a player or transport before I die of old age! The audio/music industry/community can be such an exasperating drag on its own progress sometimes.

Volume Attenuator -  a nice, simple, two-pot affair in oak made by friend David Draper. Thanks again, Dave!

Cabling/Wires - a motley assortment, none notewothy except the interconnects from/through the volume control, which are government surplus silver plated Teflon insulated twisted pair with shield.  My experience with speaker cables was short and sweet.  I am NOT a cable tweakist. I like listening to music, not equipment. But, to satisfy my ever-curious nature I made various combinations of wire, Litz, coaxial cable and ribbon and measured their inductance and capacitance. And I found out that inductance is not necessarily bad, but capacitance has to be minimal. This makes sense because high frequency current can flow through a capacitor. The cables that had high capacitance caused a loss of extreme highs. It was not a day and night difference like the hype the audio magazine guys like to write; it was subtle, but it was there. The 'best' cable was twin copper ribbon conductors laid side by side on polyethylene tape. Even this 'optimum' configuration barely beat the plain, inexpensive 'zip cord' Monster cable that I used previously, which measured surprisingly good and works just fine. The 'worst' cable was a braided multistrand Litz.

Power - Dave to the rescue again with a 12 outlet gang box/cable that plugs into a line-filtered 30amp 240v outlet in the garage.  This was done for the initial Thanksgiving 1998 debut where we had 3000 watts on the system (and the Radias at that time were in bipole panels).

Room Treatment - Two corners of the room are occupied by large bass traps built of 1/2" MDF frames covered with perforated Masonite, and filled with foam peanuts.  These really knock down the prominent resonances of my non-audio dimensioned room  ( 8' x 16' x 17' - yehhk!).  Diffusers hung on the walls behind the speakers and the listener are made from 1" foam assembled to perforated Masonite backs in a quasi-quadratic residue configuration. A bookshelf also contributes some diffusion on a side wall.

The results of all this:  up to 120 dB of sonic bliss with minimal distortion, and no second mortgage!

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Copyright © 2000 by David McNamee. All Rights Reserved.
This bit of Tungsten's Castlepage last revised August 16, 2001.