RUBY - All Alluminum Compact Monitor
Dayton RS-150-8 & Vifa D25AG-35

Last Update: 10 NOV 2006    

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With the holidays coming, I needed to put together a gift speaker for a good friend who has had more than his share of family health issues this year. He'll be spending a lot more time working from home. He needs some good tunes.

After looking thru the inventory, I came up with a pair of RS-150's & a pair Vifa D25AG's I got on clearance last year. I liked the RS-150 in the U3's I thought they'd make a tidy little "bookshelf" box. I wanted an unususal shape with a bit more depth, as I am planning roundovers of the top/side edges with a full veneer wrap. My box is a bit short & squat 8W X 12.5H X 11.75D using 3/4" MDF. It's rear vented (behind the tweeter) with a 1.5" D X 4" flared port. Box tuning (and F3) is about 46 Hz.

The raw measurements looked very promising. The D25 looked really smooth except for a dip at 3000. From prior experience, I knew the RS-150 is well behaved, but needs a high end resonance trap. Impedance looked very benign.

I wanted this to be a nice box, but I wasn't looking to break the bank on crossover parts, so I worked at simplifying the design, and reducing the cost of the component count. That meant keep the coil cost down. I designed with 18ga, 2 mH woofer coils. This costs a bit of sensitivity, but keeps the coil cost down. The other two coils are 20ga. The woofer uses a pseudo 2nd order low pass, with a parallel resonance trap. Crossover is about 2100. (If you are a real cheapskate, or insist on another 1 dB of sensitivity, you could substitute an iron core 2.0 coil. and use a 6 ohm pad resistor on the tweeter)

The tweeter uses an asymetrical, 3rd order electrical, topology. The asymetry helps smooth out the dip in the raw response (baffle edges) and results in a nicely balanced FR curve.

I have listened to a single speaker, with a mockup crossover. I am very happy. I never saw too many designs with the D25, I don't know why. This is a very smooth, detailed tweeter with a very capable lower limit. Admittedly the dome is a bit fragile, but the D25 will hit the highest levels in an effortless manner. I certainly prefer this aluminum dome to the D27 used in my Garnet design. At $33, I might give an edge to Seas 1212, at $22 (my cost last year) this tweeter was a bargain. Matched with the RS-150, this is a very smooth, neutral, & detailed box. Not particularly efficient (probably 81-82 db) but the combo covers the music range very nicely. The RS demonstrates a very nice bottom end, with a minimum of boom, but enough authority to handle a modest sized room.

I did some A/B listening with the AZ-2525. In a single speaker comparo of the AZ-2525 to the Ruby, the Ruby is more refined, smooth and warm and detailed. The AZ-2525 is more forward, crisp, and punchy and 1-2 db more efficient.