XG12 Sealed Monitor
Lou's Homepage     Last Update 29 August 2005

The XG12 was designed as a wedding gift for some good friends. I had picked up the Vifa XG18 fiberglass woofers awhile back when PE was clearing them out. I always thought they were cool looking. A lot of folks have been raving about the Seas tweeters and I had picked up a pair of the H1212 (27TBFC/G) awhile ago and thought they would be a nice match for the Vifa's.

Several folks who used the Vifa's preferred them sealed. Since I knew the new owners were living in an apartment, (and would eventually get a sub), I designed these from the get-go as sealed units. The box dimensions below are for 3/4 stock. I used baltic birch but I'm sure MDF would do as well. I think you could add or subtract an inch from the depth and not alter the performance appreciably. Volume is about 16 liters.

The mounting for the Vifa is unusual. I used a 1/2" rabbet bit to fine tune the depth. (directions can be found HERE) With two silicone seals, these are quite easy to mount and seal. The Seas is metric so a bit of filing and sanding is needed for a good fit. I used a 5/8" rabbeting bit after veneering.

Crossover and Measurements

Both drivers measured out very smooth. See measurements here. The final crossover is at about 2000 Hz. The configuration is a slightly modified 2nd order on both sides. The small resistor on the woofer side helps with phase alignment. Cap values of 16.2 to 17 do not appreciably change the response, so make the woofer cap up out of smaller values if you wish. I would estimate efficiency to be 83 db, with about 4dB of baffle step.

On the tweeter side, the split resistors are used to help with phase alignment. Any changes in padding should be done on the high side. I settled on 13.5 but feel free to adjust for taste.

Finishing and Assembly

Ryan and Karla chose Hickory/Pecan with a satin finish. The more I work with this veneer, the more I appreciate it. It's hard, flexible, has dramatic grain, and is easy to work with. Pricing is usually comparable to oak. (Personally, I don't care if I ever see another piece of stained oak)

For the XG12, I built and veneered the boxes before I measured (to get the depths correct). For finishing, I sanded the veneer with 220 grit, then wiped on a coat of Zinsser Seal Coat diluted 1:1 with alcohol. (This product is dewaxed shellac.) If you wipe, use a small pad of cotton cloth, saturated with the sealer. Use a single pass, let it dry. The shellac was followed with three coats of Fuhr 355 acrylic. After 3 days, I hand sanded with 1200 grit, then 2000 grit to get the final sheen. Pecan is an open pore wood, so grain will show (like oak).

I noted a significant peak in the XG measurements at about 1000 hz. There is a slight peak at that point in the Vifa supplied measurements as well. I thought this might have been exacerbated by the box dimensions as an internal standing wave would be expected from the height of the box at about 1000 Hz. In final form, I added a pad of dense foam at the top of the box, along with a medium pack of dacron pillow stuffing. I could not detect the peak in listening tests.

Listening Impressions

In a word, smoooooth. The lower order slopes present a very well integrated and spacious soundstage. The Seas is every bit as good as people claim, not harsh in the least, very good detail, lots of air and sparkle. The Vifa does a commendable job on vocals, piano, and strings. Off axis response is really exceptional, the image holds up very nicely. As it is sealed, it doesn't provide the bottom end of the Cryolites, nor will it handle the same power levels. I think jazz/classical/pop listeners will find the bass entirely adequate (F3 is about 65 Hz). A sub would make these sing - especially if you could roll off some of the bottom end.

In a head to head with the Cryolites, I'd have a hard time picking between the two. Both are pretty inefficient. The XG12 may have a slight edge in imaging and ultimate high end definition. The Cryolites have more substantial bass, and are a bit warmer in the vocal range. The XG12 seems a bit more forward, but that might be desireable to some.

If you can live with the power limitations (no more than an honest 60 watts), and the inefficiency, this is a very capable combination that few would find lacking. With a sub, the XG12 would satisfy most anyone.


XG12s in their New Home