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Dayton/Vifa Center Channel

This project started out as an attempt at a complete home theater system.  My old HT system was pieced together with completely different speakers, which most people will tell you is a big no-no.  The original goal was to build 4 identical speakers for the front and surround speakers, using Wayne J's D2s.  Of course, I couldn't leave well enough alone, so I decided to make some fancier cabinets for them.  At the time, I wasn't able to find any decent center channel designs, so I decided to go ahead and make my own.  I got the center and the front speakers assembled and ready for paint.  While the D2s were in the garage, we had a big storm, and the cabinets (sitting on the floor) ended up getting terrible water damage.  That was so infuriating that I had to give up on the project for a while to calm myself down.  After getting some other projects taken care of, I came back to the D2s and built the proper enclosures.  The original write-up for the "Dayton HT" system can be viewed here.  I decided to break this project up because the D2s have been sold.  The write-up for the D2s can be viewed here.

This page is intended to focus on the center channel.  I was a little hesitant to build it because I knew it was an important speaker - probably the most important in the HT setup.  I'm still not really sure what makes a good center channel speaker, but I figured I couldn't do much worse than my old center speaker.  I decided to use the Vifa D27SG tweeter from the old center channel since I already had it.  I haven't seen many shielded soft dome tweeters that are much cheaper or that would give much better performance, so it's probably a pretty good choice.  Being on a fairly tight budget, I chose the Dayton 5-1/4" woofer.  I had heard good things about it, so it seemed a good candidate.

The goal was to build a relatively low cost center channel speaker that others could easily reproduce.  The real draw-back is this - I don't have good measurement equipment, nor do I have the patience to tweak a design by ear.  This alone almost made me give up on the idea, but I plunged in anyway.  I have since then become more familiar with Speaker Workshop.  My original intent was to use Speaker Workshop to do the design work, but I was never able to get reliable results, and I didn't want to put down the money for a good calibrated mic.  I have since then built a better testing jig, and I have a new computer that works considerably better with Speaker Workshop.  I can now obtain reliable and consistent impedence measurements.  I also recently found out that there is another speaker building "addict" in town with the ability to "calibrate" my mic against his.  I still have to get the mic built, but I hope to be able to take some good measurements and update the crossover in the near future.  I will add an appendix to this article when I get the new crossover figured out (no promises though).

Here's what the current design looks like.  Right now the front baffle is only held on by a couple of screws, and the enclosure just has a quick coat of black spray paint on it so it isn't just bare MDF.  I whipped together a grill quick so the speaker would be a little more presentable.  As it stands, it actually doesn't look too bad.

You will quickly notice that it is not a standard sized center channel speaker.  I designed the entertainment center so that I would be able to put the center speaker on a shelf above the TV, which left me with quite a bit of room to work with.  I decided to go with the rather wide baffle for a couple of reasons.  First, the woofers require a rather large box, so it was either make it taller and deeper, or wider.  Wider also works out well to allow the enclosure to be vented to the front.  I chose to use dual ports to reduce the possibility of uneven loading if the port was placed closer to one of the woofers.  As you will also note from the picture, the tweeter is slightly offset from the woofers.  I may end up building a new baffle and offset the woofers and tweeter even more.  This is done to allow for a better vertical response.

The internal volume of the enclosure is about 0.90 cuft.  The enclosure is tuned to 43 Hz using two 1-1/2" I.D. ports.  This will give a lower cuttoff of about 48 Hz.  The external enclosure dimensions are 26-1/4"W x 7-1/2"H x 12"D.  These dimensions were chosen so the center channel is roughly the same width as my 27" TV.  The drawing below gives dimensions to properly locate the ports and drivers.  Not shown in the drawing are the two shelf braces that tie the front, back, top and bottom together.  Their location isn't particularly important, but having them there is essential.  The box will have some serious resonance problems without them.  Put one on both sides of the tweeter between the tweeter and woofer.  The braces can be created by cutting the proper size rectangular piece, and then removing most of the material by either routing holes (make sure the minimum thickness doesn't drop below about an inch) or cut out "windows" using a jig saw.

The woofers are run in parallel, which may produce a slightly tougher load on an amp than some commercial designs.  I thought about running the woofers in series, but the loss in effeciency didn't seem worth it, plus additional padding would be required on the tweeter.  The crossover shown below uses textbook values for 2nd order Linkwitz-Riley slopes.  I haven't tweaked the crossover at all yet, so for now just consider it a recommendation.  I think it sounds pretty good myself, but there are still a few things I would like to work out a little better.

Qty Part Number Description
$ each
2 295-300 Dayton 5-1/4" woofer
1 D27SG-05-06 (Madisound) Vifa 1" silk dome
1 027-423 5.1 uF poly cap
1 027-426 8.2 uF poly cap
1 027-348 22 uF electrolytic cap
1 027-458 .47 uF film/foil cap
1 266-822 0.8 mH 18ga inductor
1 266-816 0.5 mH 18ga inductor
1 016-4 4 W 10W resistor